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[SCM] gawk branch, master, updated. gawk-4.1.0-5387-gcd915e25
|
From: |
Arnold Robbins |
|
Subject: |
[SCM] gawk branch, master, updated. gawk-4.1.0-5387-gcd915e25 |
|
Date: |
Thu, 19 Oct 2023 02:41:24 -0400 (EDT) |
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the project "gawk".
The branch, master has been updated
via cd915e2556c62b4957fb8ee38674436425127d2e (commit)
from 1064fd0dc1766023303d7ca24fee7e0bae4bb402 (commit)
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- Log -----------------------------------------------------------------
http://git.sv.gnu.org/cgit/gawk.git/commit/?id=cd915e2556c62b4957fb8ee38674436425127d2e
commit cd915e2556c62b4957fb8ee38674436425127d2e
Author: Arnold D. Robbins <arnold@skeeve.com>
Date: Thu Oct 19 09:40:48 2023 +0300
Update to Texinfo 7.1. Lets us remove gawktexi.in in favor of gawk.texi.
diff --git a/ChangeLog b/ChangeLog
index a4d15075..123bcf41 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2023-10-19 Arnold D. Robbins <arnold@skeeve.com>
+
+ * NEWS: Updated.
+ * README: Version bumped to 5.3.0. Updated info about makeinfo
+ and texinfo.tex versions.
+
2023-10-17 Arnold D. Robbins <arnold@skeeve.com>
* re.c (make_regexp): Fix setting ok_to_escape.
diff --git a/NEWS b/NEWS
index 93fab8a0..82459204 100644
--- a/NEWS
+++ b/NEWS
@@ -30,7 +30,11 @@ Changes from 5.2.x to 5.3.0
the minor version was reset to zero. The API remains source code
compatible; that is, existing extensions should only require recompilation.
-6. And of course, there have been several minor code cleanups and bug fixes.
+6. The manual now requires Texinfo 7.1 and its texinfo.tex for formatting.
+ As a result, we no longer need to pre-process it, removing the need
+ for gawktexi.in and leaving just gawk.texi.
+
+7. And of course, there have been several minor code cleanups and bug fixes.
See the ChangeLog for details.
Changes from 5.2.2 to 5.2.x
diff --git a/README b/README
index faf9c893..f34d07b5 100644
--- a/README
+++ b/README
@@ -7,7 +7,7 @@
README:
-This is GNU Awk 5.2.2. It is upwardly compatible with Brian Kernighan's
+This is GNU Awk 5.3.0. It is upwardly compatible with Brian Kernighan's
version of Unix awk. It is almost completely compliant with the
2018 POSIX 1003.1 standard for awk. (See the note below about POSIX.)
@@ -21,10 +21,10 @@ Changes in this version are summarized in the NEWS file.
Read the file POSIX.STD for a discussion of issues where the standard
says one thing but gawk does something different.
-To format the documentation with TeX, use at least version 2023-01-02.21
+To format the documentation with TeX, use at least version 2023-09-19.19
of texinfo.tex. There is a usable copy of texinfo.tex in the doc directory.
-You must also use at least version 7.0.1 of texindex and of makeinfo
-from the texinfo-7.0.1 distribution.
+You must also use at least version 7.1 of texindex and of makeinfo
+from the texinfo-7.1 distribution.
INSTALLATION:
diff --git a/awklib/ChangeLog b/awklib/ChangeLog
index 1a840d44..34cb9352 100644
--- a/awklib/ChangeLog
+++ b/awklib/ChangeLog
@@ -1,3 +1,7 @@
+2023-10-19 Arnold D. Robbins <arnold@skeeve.com>
+
+ * Makefile.am: Replace gawktexi.in with gawk.texi.
+
2023-05-07 Arnold D. Robbins <arnold@skeeve.com>
* 5.2.2: Release tar ball made.
diff --git a/awklib/Makefile.am b/awklib/Makefile.am
index 0eeccf9c..df881805 100644
--- a/awklib/Makefile.am
+++ b/awklib/Makefile.am
@@ -65,11 +65,11 @@ clean-local:
rm -fr eg.old
rm -fr grcat.dSYM pwcat.dSYM
-$(srcdir)/stamp-eg: $(srcdir)/../doc/gawktexi.in $(srcdir)/../doc/gawkinet.texi
+$(srcdir)/stamp-eg: $(srcdir)/../doc/gawk.texi $(srcdir)/../doc/gawkinet.texi
cd $(srcdir) && \
rm -fr eg && \
rm -fr stamp-eg && \
- $(AWKPROG) -f ./extract.awk ../doc/gawktexi.in ../doc/gawkinet.texi
+ $(AWKPROG) -f ./extract.awk ../doc/gawk.texi ../doc/gawkinet.texi
@echo 'some makes are stupid and will not check a directory' >
$(srcdir)/stamp-eg
@echo 'against a file, so this file is a place holder. gack.' >>
$(srcdir)/stamp-eg
diff --git a/awklib/Makefile.in b/awklib/Makefile.in
index 5b3a7d9a..28847cac 100644
--- a/awklib/Makefile.in
+++ b/awklib/Makefile.in
@@ -692,11 +692,11 @@ clean-local:
rm -fr eg.old
rm -fr grcat.dSYM pwcat.dSYM
-$(srcdir)/stamp-eg: $(srcdir)/../doc/gawktexi.in $(srcdir)/../doc/gawkinet.texi
+$(srcdir)/stamp-eg: $(srcdir)/../doc/gawk.texi $(srcdir)/../doc/gawkinet.texi
cd $(srcdir) && \
rm -fr eg && \
rm -fr stamp-eg && \
- $(AWKPROG) -f ./extract.awk ../doc/gawktexi.in ../doc/gawkinet.texi
+ $(AWKPROG) -f ./extract.awk ../doc/gawk.texi ../doc/gawkinet.texi
@echo 'some makes are stupid and will not check a directory' >
$(srcdir)/stamp-eg
@echo 'against a file, so this file is a place holder. gack.' >>
$(srcdir)/stamp-eg
diff --git a/build-aux/ChangeLog b/build-aux/ChangeLog
index 369ee1fd..8819d06f 100644
--- a/build-aux/ChangeLog
+++ b/build-aux/ChangeLog
@@ -1,3 +1,7 @@
+2023-10-19 Arnold D. Robbins <arnold@skeeve.com>
+
+ * texinfo.tex: Upated from Texinfo 7.1 distribution.
+
2023-10-04 Arnold D. Robbins <arnold@skeeve.com>
* config.guess, config.sub, texinfo.tex: Sync from GNULIB.
diff --git a/build-aux/texinfo.tex b/build-aux/texinfo.tex
index e8c382f5..c96d4d7b 100644
--- a/build-aux/texinfo.tex
+++ b/build-aux/texinfo.tex
@@ -1,5 +1,5 @@
% texinfo.tex -- TeX macros to handle Texinfo files.
-%
+%
% Load plain if necessary, i.e., if running under initex.
\expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi
%
@@ -212,7 +212,7 @@
% @errormsg{MSG}. Do the index-like expansions on MSG, but if things
% aren't perfect, it's not the end of the world, being an error message,
% after all.
-%
+%
\def\errormsg{\begingroup \indexnofonts \doerrormsg}
\def\doerrormsg#1{\errmessage{#1}}
@@ -425,7 +425,7 @@
}%
}
-% First remove any @comment, then any @c comment. Pass the result on to
+% First remove any @comment, then any @c comment. Pass the result on to
% \argremovespace.
\def\argremovecomment#1\comment#2\ArgTerm{\argremovec #1\c\ArgTerm}
\def\argremovec#1\c#2\ArgTerm{\argremovespace#1$ $\ArgTerm}
@@ -1026,8 +1026,8 @@ where each line of input produces a line of output.}
end
end
}
- % The -2 in the arguments here gives all the input to TeX catcode 12
- % (other) or 10 (space), preventing undefined control sequence errors. See
+ % The -2 in the arguments here gives all the input to TeX catcode 12
+ % (other) or 10 (space), preventing undefined control sequence errors. See
% https://lists.gnu.org/archive/html/bug-texinfo/2019-08/msg00031.html
%
\endgroup
@@ -1129,7 +1129,7 @@ where each line of input produces a line of output.}
% for display in the outlines, and in other places. Thus, we have to
% double any backslashes. Otherwise, a name like "\node" will be
% interpreted as a newline (\n), followed by o, d, e. Not good.
-%
+%
% See http://www.ntg.nl/pipermail/ntg-pdftex/2004-July/000654.html and
% related messages. The final outcome is that it is up to the TeX user
% to double the backslashes and otherwise make the string valid, so
@@ -1421,7 +1421,7 @@ output) for that.)}
% We use the node names as the destinations.
%
% Currently we prefix the section name with the section number
- % for chapter and appendix headings only in order to avoid too much
+ % for chapter and appendix headings only in order to avoid too much
% horizontal space being required in the PDF viewer.
\def\numchapentry##1##2##3##4{%
\dopdfoutline{##2 ##1}{count-\expnumber{chap##2}}{##3}{##4}}%
@@ -1444,7 +1444,7 @@ output) for that.)}
% their "best" equivalent, based on the @documentencoding. Too
% much work for too little return. Just use the ASCII equivalents
% we use for the index sort strings.
- %
+ %
\indexnofonts
\setupdatafile
% We can have normal brace characters in the PDF outlines, unlike
@@ -1670,7 +1670,7 @@ output) for that.)}
% We use node names as destinations.
%
% Currently we prefix the section name with the section number
- % for chapter and appendix headings only in order to avoid too much
+ % for chapter and appendix headings only in order to avoid too much
% horizontal space being required in the PDF viewer.
\def\partentry##1##2##3##4{}% ignore parts in the outlines
\def\numchapentry##1##2##3##4{%
@@ -2697,7 +2697,7 @@ end
}
% Commands to set the quote options.
-%
+%
\parseargdef\codequoteundirected{%
\def\temp{#1}%
\ifx\temp\onword
@@ -2743,7 +2743,7 @@ end
% If we are in a monospaced environment, however, 1) always use \ttsl,
% and 2) do not add an italic correction.
\def\dosmartslant#1#2{%
- \ifusingtt
+ \ifusingtt
{{\ttsl #2}\let\next=\relax}%
{\def\next{{#1#2}\smartitaliccorrection}}%
\next
@@ -2922,7 +2922,7 @@ end
\gdef\codedash{\futurelet\next\codedashfinish}
\gdef\codedashfinish{%
\normaldash % always output the dash character itself.
- %
+ %
% Now, output a discretionary to allow a line break, unless
% (a) the next character is a -, or
% (b) the preceding character is a -, or
@@ -3028,7 +3028,7 @@ end
% For pdfTeX and LuaTeX
\ifurefurlonlylink
% PDF plus option to not display url, show just arg
- \unhbox0
+ \unhbox0
\else
% PDF, normally display both arg and url for consistency,
% visibility, if the pdf is eventually used to print, etc.
@@ -3041,7 +3041,7 @@ end
% For XeTeX
\ifurefurlonlylink
% PDF plus option to not display url, show just arg
- \unhbox0
+ \unhbox0
\else
% PDF, normally display both arg and url for consistency,
% visibility, if the pdf is eventually used to print, etc.
@@ -3099,10 +3099,10 @@ end
}
}
-% By default we'll break after the special characters, but some people like to
-% break before the special chars, so allow that. Also allow no breaking at
+% By default we'll break after the special characters, but some people like to
+% break before the special chars, so allow that. Also allow no breaking at
% all, for manual control.
-%
+%
\parseargdef\urefbreakstyle{%
\def\txiarg{#1}%
\ifx\txiarg\wordnone
@@ -3121,10 +3121,10 @@ end
\def\wordnone{none}
% Allow a ragged right output to aid breaking long URL's. There can
-% be a break at the \allowbreak with no extra glue (if the existing stretch in
+% be a break at the \allowbreak with no extra glue (if the existing stretch in
% the line is sufficient), a break at the \penalty with extra glue added
% at the end of the line, or no break at all here.
-% Changing the value of the penalty and/or the amount of stretch affects how
+% Changing the value of the penalty and/or the amount of stretch affects how
% preferable one choice is over the other.
\def\urefallowbreak{%
\penalty0\relax
@@ -3339,7 +3339,7 @@ $$%
% @inlinefmt{FMTNAME,PROCESSED-TEXT} and @inlineraw{FMTNAME,RAW-TEXT}.
% Ignore unless FMTNAME == tex; then it is like @iftex and @tex,
% except specified as a normal braced arg, so no newlines to worry about.
-%
+%
\def\outfmtnametex{tex}
%
\long\def\inlinefmt#1{\doinlinefmt #1,\finish}
@@ -3347,7 +3347,7 @@ $$%
\def\inlinefmtname{#1}%
\ifx\inlinefmtname\outfmtnametex \ignorespaces #2\fi
}
-%
+%
% @inlinefmtifelse{FMTNAME,THEN-TEXT,ELSE-TEXT} expands THEN-TEXT if
% FMTNAME is tex, else ELSE-TEXT.
\long\def\inlinefmtifelse#1{\doinlinefmtifelse #1,,,\finish}
@@ -3363,7 +3363,7 @@ $$%
% *right* brace they would have to use a command anyway, so they may as
% well use a command to get a left brace too. We could re-use the
% delimiter character idea from \verb, but it seems like overkill.
-%
+%
\long\def\inlineraw{\tex \doinlineraw}
\long\def\doinlineraw#1{\doinlinerawtwo #1,\finish}
\def\doinlinerawtwo#1,#2,\finish{%
@@ -3649,7 +3649,7 @@ $$%
% for non-CM glyphs. That is ec* for regular text and tc* for the text
% companion symbols (LaTeX TS1 encoding). Both are part of the ec
% package and follow the same conventions.
-%
+%
\def\ecfont{\etcfont{e}}
\def\tcfont{\etcfont{t}}
%
@@ -3731,7 +3731,7 @@ $$%
after the title page.}}%
\def\setshortcontentsaftertitlepage{%
\errmessage{@setshortcontentsaftertitlepage has been removed as a Texinfo
- command; move your @shortcontents and @contents commands if you
+ command; move your @shortcontents and @contents commands if you
want the contents after the title page.}}%
\parseargdef\shorttitlepage{%
@@ -3785,7 +3785,7 @@ $$%
% don't worry much about spacing, ragged right. This should be used
% inside a \vbox, and fonts need to be set appropriately first. \par should
% be specified before the end of the \vbox, since a vbox is a group.
-%
+%
\def\raggedtitlesettings{%
\rm
\hyphenpenalty=10000
@@ -4611,7 +4611,7 @@ $$%
% Like \expandablevalue, but completely expandable (the \message in the
% definition above operates at the execution level of TeX). Used when
% writing to auxiliary files, due to the expansion that \write does.
-% If flag is undefined, pass through an unexpanded @value command: maybe it
+% If flag is undefined, pass through an unexpanded @value command: maybe it
% will be set by the time it is read back in.
%
% NB flag names containing - or _ may not work here.
@@ -4635,7 +4635,7 @@ $$%
% @ifset VAR ... @end ifset reads the `...' iff VAR has been defined
% with @set.
-%
+%
% To get the special treatment we need for `@end ifset,' we call
% \makecond and then redefine.
%
@@ -4668,7 +4668,7 @@ $$%
% without the @) is in fact defined. We can only feasibly check at the
% TeX level, so something like `mathcode' is going to considered
% defined even though it is not a Texinfo command.
-%
+%
\makecond{ifcommanddefined}
\def\ifcommanddefined{\parsearg{\doifcmddefined{\let\next=\ifcmddefinedfail}}}
%
@@ -4774,7 +4774,7 @@ $$%
\def\docodeindex#1{\edef\indexname{#1}\parsearg\docodeindexxxx}
\def\docodeindexxxx #1{\docind{\indexname}{#1}}
-
+
% \definedummyword defines \#1 as \string\#1\space, thus effectively
% preventing its expansion. This is used only for control words,
% not control letters, because the \space would be incorrect for
@@ -4791,7 +4791,7 @@ $$%
\def\definedummyword #1{\def#1{\string#1\space}}%
\def\definedummyletter#1{\def#1{\string#1}}%
-% Used for the aux, toc and index files to prevent expansion of Texinfo
+% Used for the aux, toc and index files to prevent expansion of Texinfo
% commands. Most of the commands are controlled through the
% \ifdummies conditional.
%
@@ -5081,7 +5081,7 @@ $$%
\let\value\indexnofontsvalue
}
-
+
% #1 is the index name, #2 is the entry text.
@@ -5122,7 +5122,7 @@ $$%
\ifx\suffix\indexisfl\def\suffix{f1}\fi
% Open the file
\immediate\openout\csname#1indfile\endcsname \jobname.\suffix
- % Using \immediate above here prevents an object entering into the current
+ % Using \immediate above here prevents an object entering into the current
% box, which could confound checks such as those in \safewhatsit for
% preceding skips.
\typeout{Writing index file \jobname.\suffix}%
@@ -5174,7 +5174,7 @@ $$%
\ifx\segment\isfinish
\else
%
- % Fully expand the segment, throwing away any @sortas directives, and
+ % Fully expand the segment, throwing away any @sortas directives, and
% trim spaces.
\edef\trimmed{\segment}%
\edef\trimmed{\expandafter\eatspaces\expandafter{\trimmed}}%
@@ -5238,12 +5238,12 @@ $$%
% the current value of \escapechar.
\def\escapeisbackslash{\escapechar=`\\}
-% Use \ in index files by default. texi2dvi didn't support @ as the escape
-% character (as it checked for "\entry" in the files, and not "@entry"). When
-% the new version of texi2dvi has had a chance to become more prevalent, then
-% the escape character can change back to @ again. This should be an easy
-% change to make now because both @ and \ are only used as escape characters in
-% index files, never standing for themselves.
+% Use \ in index files by default. texi2dvi didn't support @ as the escape
+% character (as it checked for "\entry" in the files, and not "@entry"). When
+% the new version of texi2dvi has had a chance to become more prevalent, then
+% the escape character can change back to @ again. This should be an easy
+% change to make now because both @ and \ are only used as escape characters
in
+% index files, never standing for themselves.
%
\set txiindexescapeisbackslash
@@ -5266,7 +5266,7 @@ $$%
\def\}{\rbracechar{}}%
\uccode`\~=`\\ \uppercase{\def~{\backslashchar{}}}%
%
- % Split the entry into primary entry and any subentries, and get the index
+ % Split the entry into primary entry and any subentries, and get the index
% sort key.
\splitindexentry\indextext
%
@@ -5447,18 +5447,18 @@ $$%
\uccode`\~=`\\ \uppercase{\if\noexpand~}\noexpand#1
\ifflagclear{txiskipindexfileswithbackslash}{%
\errmessage{%
-ERROR: A sorted index file in an obsolete format was skipped.
+ERROR: A sorted index file in an obsolete format was skipped.
To fix this problem, please upgrade your version of 'texi2dvi'
or 'texi2pdf' to that at <https://ftp.gnu.org/gnu/texinfo>.
-If you are using an old version of 'texindex' (part of the Texinfo
+If you are using an old version of 'texindex' (part of the Texinfo
distribution), you may also need to upgrade to a newer version (at least 6.0).
You may be able to typeset the index if you run
'texindex \jobname.\indexname' yourself.
-You could also try setting the 'txiindexescapeisbackslash' flag by
+You could also try setting the 'txiindexescapeisbackslash' flag by
running a command like
-'texi2dvi -t "@set txiindexescapeisbackslash" \jobname.texi'. If you do
+'texi2dvi -t "@set txiindexescapeisbackslash" \jobname.texi'. If you do
this, Texinfo will try to use index files in the old format.
-If you continue to have problems, deleting the index files and starting again
+If you continue to have problems, deleting the index files and starting again
might help (with 'rm \jobname.?? \jobname.??s')%
}%
}{%
@@ -5531,7 +5531,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% bottom of a column to reduce an increase in inter-line spacing.
\nobreak
\vskip 0pt plus 5\baselineskip
- \penalty -300
+ \penalty -300
\vskip 0pt plus -5\baselineskip
%
% Typeset the initial. Making this add up to a whole number of
@@ -5851,7 +5851,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\newbox\balancedcolumns
\setbox\balancedcolumns=\vbox{shouldnt see this}%
%
-% Only called for the last of the double column material. \doublecolumnout
+% Only called for the last of the double column material. \doublecolumnout
% does the others.
\def\balancecolumns{%
\setbox0 = \vbox{\unvbox\PAGE}% like \box255 but more efficient, see p.120.
@@ -5879,7 +5879,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}%
% Now the left column is in box 1, and the right column in box 3.
%
- % Check whether the left column has come out higher than the page itself.
+ % Check whether the left column has come out higher than the page itself.
% (Note that we have doubled \vsize for the double columns, so
% the actual height of the page is 0.5\vsize).
\ifdim2\ht1>\vsize
@@ -6176,7 +6176,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\let\top\unnumbered
% Sections.
-%
+%
\outer\parseargdef\numberedsec{\numhead1{#1}} % normally calls seczzz
\def\seczzz#1{%
\global\subsecno=0 \global\subsubsecno=0 \global\advance\secno by 1
@@ -6199,7 +6199,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}
% Subsections.
-%
+%
% normally calls numberedsubseczzz:
\outer\parseargdef\numberedsubsec{\numhead2{#1}}
\def\numberedsubseczzz#1{%
@@ -6224,7 +6224,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}
% Subsubsections.
-%
+%
% normally numberedsubsubseczzz:
\outer\parseargdef\numberedsubsubsec{\numhead3{#1}}
\def\numberedsubsubseczzz#1{%
@@ -7409,7 +7409,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% @indentedblock is like @quotation, but indents only on the left and
% has no optional argument.
-%
+%
\makedispenvdef{indentedblock}{\indentedblockstart}
%
\def\indentedblockstart{%
@@ -7723,7 +7723,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% @deftypefnnewline on|off says whether the return type of typed functions
% are printed on their own line. This affects @deftypefn, @deftypefun,
% @deftypeop, and @deftypemethod.
-%
+%
\parseargdef\deftypefnnewline{%
\def\temp{#1}%
\ifx\temp\onword
@@ -7893,7 +7893,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\tclose{\temp}% typeset the return type
\ifrettypeownline
% put return type on its own line; prohibit line break following:
- \hfil\vadjust{\nobreak}\break
+ \hfil\vadjust{\nobreak}\break
\else
\space % type on same line, so just followed by a space
\fi
@@ -8043,7 +8043,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\scantokens{#1@comment}%
%
% The \comment is to remove the \newlinechar added by \scantokens, and
- % can be noticed by \parsearg. Note \c isn't used because this means cedilla
+ % can be noticed by \parsearg. Note \c isn't used because this means
cedilla
% in math mode.
}
@@ -8238,7 +8238,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% list to some hook where the argument is to be expanded. If there are
% less than 10 arguments that hook is to be replaced by ##N where N
% is the position in that list, that is to say the macro arguments are to be
-% defined `a la TeX in the macro body.
+% defined `a la TeX in the macro body.
%
% That gets used by \mbodybackslash (above).
%
@@ -8272,7 +8272,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
%
% Read recursive and nonrecursive macro bodies. (They're different since
% rec and nonrec macros end differently.)
-%
+%
% We are in \macrobodyctxt, and the \xdef causes backslashes in the macro
% body to be transformed.
% Set \macrobody to the body of the macro, and call \macrodef.
@@ -8307,7 +8307,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% twice the \macarg.BLAH macros does not cost too much processing power.
\def\parsemmanyargdef@@#1,{%
\if#1;\let\next=\relax
- \else
+ \else
\let\next=\parsemmanyargdef@@
\edef\tempb{\eatspaces{#1}}%
\expandafter\def\expandafter\tempa
@@ -8392,7 +8392,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% Replace arguments by their values in the macro body, and place the result
% in macro \@tempa.
-%
+%
\def\macvalstoargs@{%
% To do this we use the property that token registers that are \the'ed
% within an \edef expand only once. So we are going to place all argument
@@ -8416,9 +8416,9 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\expandafter\def\expandafter\@tempa\expandafter{\@tempc}%
}
-% Define the named-macro outside of this group and then close this group.
-%
-\def\macargexpandinbody@{%
+% Define the named-macro outside of this group and then close this group.
+%
+\def\macargexpandinbody@{%
\expandafter
\endgroup
\macargdeflist@
@@ -8456,7 +8456,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}
% Trailing missing arguments are set to empty.
-%
+%
\def\setemptyargvalues@{%
\ifx\paramlist\nilm@
\let\next\macargexpandinbody@
@@ -8534,7 +8534,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\else % at most 9
\ifnum\paramno<10\relax
% @MACNAME sets the context for reading the macro argument
- % @MACNAME@@ gets the argument, processes backslashes and appends a
+ % @MACNAME@@ gets the argument, processes backslashes and appends a
% comma.
% @MACNAME@@@ removes braces surrounding the argument list.
% @MACNAME@@@@ scans the macro body with arguments substituted.
@@ -8578,11 +8578,11 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% Call #1 with a list of tokens #2, with any doubled backslashes in #2
% compressed to one.
%
-% This implementation works by expansion, and not execution (so we cannot use
-% \def or similar). This reduces the risk of this failing in contexts where
-% complete expansion is done with no execution (for example, in writing out to
+% This implementation works by expansion, and not execution (so we cannot use
+% \def or similar). This reduces the risk of this failing in contexts where
+% complete expansion is done with no execution (for example, in writing out to
% an auxiliary file for an index entry).
-%
+%
% State is kept in the input stream: the argument passed to
% @look_ahead, @gobble_and_check_finish and @add_segment is
%
@@ -8604,11 +8604,11 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% #3 - NEXT_TOKEN
% #4 used to look ahead
%
-% If the next token is not a backslash, process the rest of the argument;
+% If the next token is not a backslash, process the rest of the argument;
% otherwise, remove the next token.
@gdef@look_ahead#1!#2#3#4{%
@ifx#4\%
- @expandafter@gobble_and_check_finish
+ @expandafter@gobble_and_check_finish
@else
@expandafter@add_segment
@fi#1!{#2}#4#4%
@@ -8632,9 +8632,9 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% #3 - NEXT_TOKEN
% #4 is input stream until next backslash
%
-% Input stream is either at the start of the argument, or just after a
-% backslash sequence, either a lone backslash, or a doubled backslash.
-% NEXT_TOKEN contains the first token in the input stream: if it is \finish,
+% Input stream is either at the start of the argument, or just after a
+% backslash sequence, either a lone backslash, or a doubled backslash.
+% NEXT_TOKEN contains the first token in the input stream: if it is \finish,
% finish; otherwise, append to ARG_RESULT the segment of the argument up until
% the next backslash. PENDING_BACKSLASH contains a backslash to represent
% a backslash just before the start of the input stream that has not been
@@ -8646,13 +8646,13 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% append the pending backslash to the result, followed by the next segment
@expandafter@is_fi@look_ahead#1#2#4!{\}@fi
% this @fi is discarded by @look_ahead.
- % we can't get rid of it with \expandafter because we don't know how
+ % we can't get rid of it with \expandafter because we don't know how
% long #4 is.
}
% #1 - THE_MACRO
% #2 - ARG_RESULT
-% #3 discards the res of the conditional in @add_segment, and @is_fi ends the
+% #3 discards the res of the conditional in @add_segment, and @is_fi ends the
% conditional.
@gdef@call_the_macro#1#2!#3@fi{@is_fi #1{#2}}
@@ -8664,7 +8664,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% for reading the argument (slightly different in the two cases). Then,
% to read the argument, in the whole-line case, it then calls the regular
% \parsearg MAC; in the lbrace case, it calls \passargtomacro MAC.
-%
+%
\def\braceorline#1{\let\macnamexxx=#1\futurelet\nchar\braceorlinexxx}
\def\braceorlinexxx{%
\ifx\nchar\bgroup
@@ -8787,7 +8787,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% Used so that the @top node doesn't have to be wrapped in an @ifnottex
% conditional.
-% \doignore goes to more effort to skip nested conditionals but we don't need
+% \doignore goes to more effort to skip nested conditionals but we don't need
% that here.
\def\omittopnode{%
\ifx\lastnode\wordTop
@@ -8869,7 +8869,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% automatically in xrefs, if the third arg is not explicitly specified.
% This was provided as a "secret" @set xref-automatic-section-title
% variable, now it's official.
-%
+%
\parseargdef\xrefautomaticsectiontitle{%
\def\temp{#1}%
\ifx\temp\onword
@@ -8885,7 +8885,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\fi\fi
}
-%
+%
% @xref, @pxref, and @ref generate cross-references. For \xrefX, #1 is
% the node name, #2 the name of the Info cross-reference, #3 the printed
% node name, #4 the name of the Info file, #5 the name of the printed
@@ -9083,20 +9083,20 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\space\putwordpage\tie\refx{#1-pg}}
% Output a cross-manual xref to #1. Used just above (twice).
-%
+%
% Only include the text "Section ``foo'' in" if the foo is neither
% missing or Top. Thus, @xref{,,,foo,The Foo Manual} outputs simply
% "see The Foo Manual", the idea being to refer to the whole manual.
-%
+%
% But, this being TeX, we can't easily compare our node name against the
% string "Top" while ignoring the possible spaces before and after in
% the input. By adding the arbitrary 7sp below, we make it much less
% likely that a real node name would have the same width as "Top" (e.g.,
% in a monospaced font). Hopefully it will never happen in practice.
-%
+%
% For the same basic reason, we retypeset the "Top" at every
% reference, since the current font is indeterminate.
-%
+%
\def\crossmanualxref#1{%
\setbox\toprefbox = \hbox{Top\kern7sp}%
\setbox2 = \hbox{\ignorespaces \printedrefname \unskip \kern7sp}%
@@ -9188,9 +9188,9 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\fi
}
-% This is the macro invoked by entries in the aux file. Define a control
-% sequence for a cross-reference target (we prepend XR to the control sequence
-% name to avoid collisions). The value is the page number. If this is a float
+% This is the macro invoked by entries in the aux file. Define a control
+% sequence for a cross-reference target (we prepend XR to the control sequence
+% name to avoid collisions). The value is the page number. If this is a
float
% type, we have more work to do.
%
\def\xrdef#1#2{%
@@ -9206,10 +9206,10 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\bgroup
\expandafter\gdef\csname XR\safexrefname\endcsname{#2}%
\egroup
- % We put the \gdef inside a group to avoid the definitions building up on
- % TeX's save stack, which can cause it to run out of space for aux files with
+ % We put the \gdef inside a group to avoid the definitions building up on
+ % TeX's save stack, which can cause it to run out of space for aux files
with
% thousands of lines. \gdef doesn't use the save stack, but \csname does
- % when it defines an unknown control sequence as \relax.
+ % when it defines an unknown control sequence as \relax.
%
% Was that xref control sequence that we just defined for a float?
\expandafter\iffloat\csname XR\safexrefname\endcsname
@@ -10406,7 +10406,7 @@ directory should work if nowhere else does.}
\uppercase{.}
\endgroup
\else
- \errhelp = \EMsimple
+ \errhelp = \EMsimple
\errmessage{Unicode character U+#1 not supported, sorry}%
\fi
\else
@@ -10439,7 +10439,7 @@ directory should work if nowhere else does.}
\countUTFz = "#1\relax
\begingroup
\parseXMLCharref
-
+
% Give \u8:... its definition. The sequence of seven \expandafter's
% expands after the \gdef three times, e.g.
%
@@ -10451,7 +10451,7 @@ directory should work if nowhere else does.}
\expandafter\expandafter
\expandafter\expandafter
\expandafter\gdef \UTFviiiTmp{#2}%
- %
+ %
\expandafter\ifx\csname uni:#1\endcsname \relax \else
\message{Internal error, already defined: #1}%
\fi
@@ -10490,7 +10490,7 @@ directory should work if nowhere else does.}
\divide\countUTFz by 64
\countUTFy = \countUTFz % Save to be the future value of \countUTFz.
\multiply\countUTFz by 64
-
+
% \countUTFz is now \countUTFx with the last 5 bits cleared. Subtract
% in order to get the last five bits.
\advance\countUTFx by -\countUTFz
@@ -10525,7 +10525,7 @@ directory should work if nowhere else does.}
% U+0080..U+00FF =
https://en.wikipedia.org/wiki/Latin-1_Supplement_(Unicode_block)
% U+0100..U+017F = https://en.wikipedia.org/wiki/Latin_Extended-A
% U+0180..U+024F = https://en.wikipedia.org/wiki/Latin_Extended-B
-%
+%
% Many of our renditions are less than wonderful, and all the missing
% characters are available somewhere. Loading the necessary fonts
% awaits user request. We can't truly support Unicode without
@@ -11770,7 +11770,7 @@ directory should work if nowhere else does.}
\def\texinfochars{%
\let< = \activeless
\let> = \activegtr
- \let~ = \activetilde
+ \let~ = \activetilde
\let^ = \activehat
\setregularquotes
\let\b = \strong
diff --git a/doc/ChangeLog b/doc/ChangeLog
index 931efe69..3baa4282 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,11 @@
+2023-10-19 Arnold D. Robbins <arnold@skeeve.com>
+
+ * gawk.texi: Renamed from gawktexi.in. Sidebars converted to
+ @cartouche for Texinfo 7.1.
+ * sidebar.awk: Removed.
+ * texinfo.tex: Updated from Texinfo 7.1 distribution.
+ * Makefile.am: Converted gawktexi.in to gawk.texi.
+
2023-10-19 Arnold D. Robbins <arnold@skeeve.com>
* gawktexi.in: Update the date, add some indexing, removing FIXMEs.
diff --git a/doc/Makefile.am b/doc/Makefile.am
index 10fafd37..a8d8dfd7 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -43,7 +43,6 @@ EXTRA_DIST = ChangeLog ChangeLog.0 ChangeLog.1 \
awkcard.in awkforai.txt texinfo.tex cardfonts \
$(fig_images) $(txt_images) $(eps_images) $(pdf_images) \
$(html_images) \
- gawktexi.in sidebar.awk \
it \
macros colors no.colors $(man_MANS) \
lflashlight-small.xpic lflashlight.eps lflashlight.pdf \
@@ -75,9 +74,6 @@ AWKCARD = awkcard.ps
# to ensure that awkcard.tr is processed by tbl.
#AWKCARD = awkcard.nc
-gawk.texi: $(srcdir)/gawktexi.in $(srcdir)/sidebar.awk
- awk -f $(srcdir)/sidebar.awk < $(srcdir)/gawktexi.in > gawk.texi
-
postscript: gawk.ps gawkinet.ps gawkworkflow.ps pm-gawk.ps gawk.1.ps
gawkbug.1.ps pm-gawk.1.ps $(AWKCARD)
pdf-local: postscript gawk.pdf gawkinet.pdf awkcard.pdf gawk.1.pdf
gawkbug.1.pdf pm-gawk.1.pdf pm-gawk.pdf
@@ -127,8 +123,8 @@ awkcard.pdf: awkcard.ps
spell: spellmanual spellworkflow spellmanpage spellinet
spellmanual:
- @echo ==== gawktexi.in ====;
- export LC_ALL=C ; spell "$(srcdir)"/gawktexi.in | \
+ @echo ==== gawk.texi ====;
+ export LC_ALL=C ; spell "$(srcdir)"/gawk.texi | \
sort -u | comm -23 - "$(srcdir)"/wordlist
spellworkflow:
diff --git a/doc/Makefile.in b/doc/Makefile.in
index ab9f7429..c6745dfc 100644
--- a/doc/Makefile.in
+++ b/doc/Makefile.in
@@ -380,7 +380,6 @@ EXTRA_DIST = ChangeLog ChangeLog.0 ChangeLog.1 \
awkcard.in awkforai.txt texinfo.tex cardfonts \
$(fig_images) $(txt_images) $(eps_images) $(pdf_images) \
$(html_images) \
- gawktexi.in sidebar.awk \
it \
macros colors no.colors $(man_MANS) \
lflashlight-small.xpic lflashlight.eps lflashlight.pdf \
@@ -933,9 +932,6 @@ uninstall-man: uninstall-man1
# to ensure that awkcard.tr is processed by tbl.
#AWKCARD = awkcard.nc
-gawk.texi: $(srcdir)/gawktexi.in $(srcdir)/sidebar.awk
- awk -f $(srcdir)/sidebar.awk < $(srcdir)/gawktexi.in > gawk.texi
-
postscript: gawk.ps gawkinet.ps gawkworkflow.ps pm-gawk.ps gawk.1.ps
gawkbug.1.ps pm-gawk.1.ps $(AWKCARD)
pdf-local: postscript gawk.pdf gawkinet.pdf awkcard.pdf gawk.1.pdf
gawkbug.1.pdf pm-gawk.1.pdf pm-gawk.pdf
@@ -985,8 +981,8 @@ awkcard.pdf: awkcard.ps
spell: spellmanual spellworkflow spellmanpage spellinet
spellmanual:
- @echo ==== gawktexi.in ====;
- export LC_ALL=C ; spell "$(srcdir)"/gawktexi.in | \
+ @echo ==== gawk.texi ====;
+ export LC_ALL=C ; spell "$(srcdir)"/gawk.texi | \
sort -u | comm -23 - "$(srcdir)"/wordlist
spellworkflow:
diff --git a/doc/gawk.info b/doc/gawk.info
index 84807c15..3f99c67b 100644
--- a/doc/gawk.info
+++ b/doc/gawk.info
@@ -1,23 +1,23 @@
-This is gawk.info, produced by makeinfo version 7.0.1 from gawk.texi.
+This is gawk.info, produced by makeinfo version 7.1 from gawk.texi.
-Copyright © 1989, 1991, 1992, 1993, 1996â2005, 2007, 2009â2023
+Copyright © 1989, 1991, 1992, 1993, 1996-2005, 2007, 2009-2023
Free Software Foundation, Inc.
- This is Edition 5.3 of âGAWK: Effective AWK Programming: A Userâs
+ This is Edition 5.3 of âGAWK: Effective AWK Programming: A User's
Guide for GNU Awkâ, for the 5.3.0 (or later) version of the GNU
implementation of AWK.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
-Invariant Sections being âGNU General Public Licenseâ, with the
-Front-Cover Texts being âA GNU Manualâ, and with the Back-Cover Texts as
+Invariant Sections being "GNU General Public License", with the
+Front-Cover Texts being "A GNU Manual", and with the Back-Cover Texts as
in (a) below. A copy of the license is included in the section entitled
-âGNU Free Documentation Licenseâ.
+"GNU Free Documentation License".
- a. The FSFâs Back-Cover Text is: âYou have the freedom to copy and
- modify this GNU manual.â
+ a. The FSF's Back-Cover Text is: "You have the freedom to copy and
+ modify this GNU manual."
INFO-DIR-SECTION Text creation and manipulation
START-INFO-DIR-ENTRY
* Gawk: (gawk). A text scanning and processing language.
@@ -37,24 +37,24 @@ General Introduction
This file documents âawkâ, a program that you can use to select
particular records in a file and perform operations upon them.
- Copyright © 1989, 1991, 1992, 1993, 1996â2005, 2007, 2009â2023
+ Copyright © 1989, 1991, 1992, 1993, 1996-2005, 2007, 2009-2023
Free Software Foundation, Inc.
- This is Edition 5.3 of âGAWK: Effective AWK Programming: A Userâs
+ This is Edition 5.3 of âGAWK: Effective AWK Programming: A User's
Guide for GNU Awkâ, for the 5.3.0 (or later) version of the GNU
implementation of AWK.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
-Invariant Sections being âGNU General Public Licenseâ, with the
-Front-Cover Texts being âA GNU Manualâ, and with the Back-Cover Texts as
+Invariant Sections being "GNU General Public License", with the
+Front-Cover Texts being "A GNU Manual", and with the Back-Cover Texts as
in (a) below. A copy of the license is included in the section entitled
-âGNU Free Documentation Licenseâ.
+"GNU Free Documentation License".
- a. The FSFâs Back-Cover Text is: âYou have the freedom to copy and
- modify this GNU manual.â
+ a. The FSF's Back-Cover Text is: "You have the freedom to copy and
+ modify this GNU manual."
* Menu:
@@ -160,7 +160,7 @@ in (a) below. A copy of the license is included in the
section entitled
* AWKLIBPATH Variable:: Searching directories for
âawkâ shared libraries.
* Other Environment Variables:: The environment variables.
-* Exit Status:: âgawkââs exit status.
+* Exit Status:: âgawkâ's exit status.
* Include Files:: Including other files into your
program.
* Loading Shared Libraries:: Loading shared libraries into your
@@ -286,7 +286,7 @@ in (a) below. A copy of the license is included in the
section entitled
* Strings And Numbers:: How âawkâ Converts Between
Strings And Numbers.
* Locale influences conversions:: How the locale may affect conversions.
-* All Operators:: âgawkââs operators.
+* All Operators:: âgawkâ's operators.
* Arithmetic Ops:: Arithmetic operations (â+â,
â-â, etc.)
* Concatenation:: Concatenating strings.
@@ -295,8 +295,8 @@ in (a) below. A copy of the license is included in the
section entitled
* Increment Ops:: Incrementing the numeric value of a
variable.
* Truth Values and Conditions:: Testing for true and false.
-* Truth Values:: What is âtrueâ and what is
- âfalseâ.
+* Truth Values:: What is "true" and what is
+ "false".
* Typing and Comparison:: How variables acquire types and how
this affects comparison of numbers and
strings with â<â, etc.
@@ -304,9 +304,9 @@ in (a) below. A copy of the license is included in the
section entitled
* Comparison Operators:: The comparison operators.
* POSIX String Comparison:: String comparison with POSIX rules.
* Boolean Ops:: Combining comparison expressions using
- boolean operators â||â (âorâ),
- â&&â (âandâ) and â!â
- (ânotâ).
+ boolean operators â||â ("or"),
+ â&&â ("and") and â!â
+ ("not").
* Conditional Exp:: Conditional expressions select between
two subexpressions under control of a
third subexpression.
@@ -369,7 +369,7 @@ in (a) below. A copy of the license is included in the
section entitled
* Array Example:: Basic Example of an Array
* Scanning an Array:: A variation of the âforâ
statement. It loops through the
- indices of an arrayâs existing
+ indices of an array's existing
elements.
* Controlling Scanning:: Controlling the order in which arrays
are scanned.
@@ -411,7 +411,7 @@ in (a) below. A copy of the license is included in the
section entitled
* Function Example:: An example function definition and
what it does.
* Function Calling:: Calling user-defined functions.
-* Calling A Function:: Donât use spaces.
+* Calling A Function:: Don't use spaces.
* Variable Scope:: Controlling variable scope.
* Pass By Value/Reference:: Passing parameters.
* Function Caveats:: Other points to know about functions.
@@ -600,7 +600,7 @@ in (a) below. A copy of the license is included in the
section entitled
* Symbol Table Access:: Functions for accessing global
variables.
* Symbol table by name:: Accessing variables by name.
-* Symbol table by cookie:: Accessing variables by âcookieâ.
+* Symbol table by cookie:: Accessing variables by "cookie".
* Cached values:: Creating and using cached values.
* Array Manipulation:: Functions for working with arrays.
* Array Data Types:: Data types for working with arrays.
@@ -614,7 +614,7 @@ in (a) below. A copy of the license is included in the
section entitled
* Extension GMP/MPFR Versioning:: Version information about GMP and
MPFR.
* Extension API Informational Variables:: Variables providing information about
- âgawkââs invocation.
+ âgawkâ's invocation.
* Extension API Boilerplate:: Boilerplate code for using the API.
* Changes from API V1:: Changes from V1 of the API.
* Finding Extensions:: How âgawkâ finds compiled
@@ -650,7 +650,7 @@ in (a) below. A copy of the license is included in the
section entitled
* SVR4:: Minor changes between System V
Releases 3.1 and 4.
* POSIX:: New features from the POSIX standard.
-* BTL:: New features from Brian Kernighanâs
+* BTL:: New features from Brian Kernighan's
version of âawkâ.
* POSIX/GNU:: The extensions in âgawkâ not
in POSIX âawkâ.
@@ -673,7 +673,7 @@ in (a) below. A copy of the license is included in the
section entitled
* Compiling with MPFR:: Building with MPFR.
* Shell Startup Files:: Shell convenience functions.
* Additional Configuration Options:: Other compile-time options.
-* Configuration Philosophy:: How itâs all supposed to work.
+* Configuration Philosophy:: How it's all supposed to work.
* Compiling from Git:: Compiling from Git.
* Building the Documentation:: Building the Documentation.
* Non-Unix Installation:: Installation on Other Operating
@@ -748,7 +748,7 @@ Foreword to the Third Edition
*****************************
Arnold Robbins and I are good friends. We were introduced in 1990 by
-circumstancesâand our favorite programming language, AWK. The
+circumstances--and our favorite programming language, AWK. The
circumstances started a couple of years earlier. I was working at a new
job and noticed an unplugged Unix computer sitting in the corner. No
one knew how to use it, and neither did I. However, a couple of days
@@ -757,15 +757,15 @@ day, I began the transition from statistician to Unix
programmer.
On one of many trips to the library or bookstore in search of books
on Unix, I found the gray AWK book, a.k.a. Alfred V. Aho, Brian W.
-Kernighan, and Peter J. Weinbergerâs âThe AWK Programming Languageâ
-(Addison-Wesley, 1988). âawkââs simple programming paradigmâfind a
-pattern in the input and then perform an actionâoften reduced complex or
-tedious data manipulations to a few lines of code. I was excited to try
-my hand at programming in AWK.
+Kernighan, and Peter J. Weinberger's âThe AWK Programming Languageâ
+(Addison-Wesley, 1988). âawkâ's simple programming paradigm--find a
+pattern in the input and then perform an action--often reduced complex
+or tedious data manipulations to a few lines of code. I was excited to
+try my hand at programming in AWK.
Alas, the âawkâ on my computer was a limited version of the language
-described in the gray book. I discovered that my computer had âold
-âawkââ and the book described ânew âawkâ.â I learned that this
was
+described in the gray book. I discovered that my computer had "old
+âawkâ" and the book described "new âawkâ." I learned that this was
typical; the old version refused to step aside or relinquish its name.
If a system had a new âawkâ, it was invariably called ânawkâ, and few
systems had it. The best way to get a new âawkâ was to âftpâ the
source
@@ -773,7 +773,7 @@ code for âgawkâ from âprep.ai.mit.eduâ. âgawkâ
was a version of new
âawkâ written by David Trueman and Arnold, and available under the GNU
General Public License.
- (Incidentally, itâs no longer difficult to find a new âawkâ.
âgawkâ
+ (Incidentally, it's no longer difficult to find a new âawkâ. âgawkâ
ships with GNU/Linux, and you can download binaries or source code for
almost any system; my wife uses âgawkâ on her VMS box.)
@@ -791,8 +791,8 @@ support language extensions added after publication of
âThe AWK
Programming Languageâ.
Frankly, if our roles had been reversed, I would not have been so
-open and we probably would have never met. Iâm glad we did meet. He is
-an AWK expertâs AWK expert and a genuinely nice person. Arnold
+open and we probably would have never met. I'm glad we did meet. He is
+an AWK expert's AWK expert and a genuinely nice person. Arnold
contributes significant amounts of his expertise and time to the Free
Software Foundation.
@@ -802,10 +802,10 @@ definitive reference to the AWK language as defined by
the 1987 Bell
Laboratories release and codified in the 1992 POSIX Utilities standard.
On the other hand, the novice AWK programmer can study a wealth of
-practical programs that emphasize the power of AWKâs basic idioms:
+practical programs that emphasize the power of AWK's basic idioms:
data-driven control flow, pattern matching with regular expressions, and
associative arrays. Those looking for something new can try out
-âgawkââs interface to network protocols via special â/inetâ files.
+âgawkâ's interface to network protocols via special â/inetâ files.
The programs in this book make clear that an AWK program is typically
much smaller and faster to develop than a counterpart written in C.
@@ -819,7 +819,7 @@ counts. I recently experimented with an algorithm that for
n lines of
input, exhibited ~ C n^2 performance, while theory predicted ~ C n log n
behavior. A few minutes poring over the âawkprof.outâ profile
pinpointed the problem to a single line of code. âpgawkâ is a welcome
-addition to my programmerâs toolbox.
+addition to my programmer's toolbox.
Arnold has distilled over a decade of experience writing and using
AWK programs, and developing âgawkâ, into this book. If you use AWK or
@@ -835,8 +835,8 @@ File: gawk.info, Node: Foreword4, Next: Preface, Prev:
Foreword3, Up: Top
Foreword to the Fourth Edition
******************************
-Some things donât change. Thirteen years ago I wrote: âIf you use AWK
-or want to learn how, then read this book.â True then, and still true
+Some things don't change. Thirteen years ago I wrote: "If you use AWK
+or want to learn how, then read this book." True then, and still true
today.
Learning to use a programming language is about more than mastering
@@ -884,7 +884,7 @@ with the proper options or environment variables, it is
fully compatible
with the POSIX(1) specification of the âawkâ language and with the Unix
version of âawkâ maintained by Brian Kernighan. This means that all
properly written âawkâ programs should work with âgawkâ. So most of
the
-time, we donât distinguish between âgawkâ and other âawkâ
+time, we don't distinguish between âgawkâ and other âawkâ
implementations.
Using âawkâ you can:
@@ -920,7 +920,7 @@ such as input/output (I/O) redirection and pipes.
Implementations of the âawkâ language are available for many
different computing environments. This Info file, while describing the
âawkâ language in general, also describes the particular implementation
-of âawkâ called âgawkâ (which stands for âGNU âawkââ).
âgawkâ runs on a
+of âawkâ called âgawkâ (which stands for "GNU âawkâ"). âgawkâ
runs on a
broad range of Unix systems, ranging from Intel-architecture PC-based
computers up through large-scale systems. âgawkâ has also been ported
to macOS, z/OS, Microsoft Windows (all versions), and OpenVMS.(3)
@@ -979,8 +979,8 @@ version made the programming language more powerful,
introducing
user-defined functions, multiple input streams, and computed regular
expressions. This new version became widely available with Unix System
V Release 3.1 (1987). The version in System V Release 4 (1989) added
-some new features and cleaned up the behavior in some of the âdark
-cornersâ of the language. The specification for âawkâ in the POSIX
+some new features and cleaned up the behavior in some of the "dark
+corners" of the language. The specification for âawkâ in the POSIX
Command Language and Utilities standard further clarified the language.
Both the âgawkâ designers and the original âawkâ designers at Bell
Laboratories provided feedback for the POSIX specification.
@@ -1015,11 +1015,11 @@ A Rose by Any Other Name
The âawkâ language has evolved over the years. Full details are
provided in *note Language History::. The language described in this
-Info file is often referred to as ânew âawkâ.â By analogy, the original
-version of âawkâ is referred to as âold âawkâ.â
+Info file is often referred to as "new âawkâ." By analogy, the original
+version of âawkâ is referred to as "old âawkâ."
On most current systems, when you run the âawkâ utility you get some
-version of new âawkâ.(1) If your systemâs standard âawkâ is the old
+version of new âawkâ.(1) If your system's standard âawkâ is the old
one, you will see something like this if you try the following test
program:
@@ -1048,10 +1048,10 @@ Using This Book
The term âawkâ refers to a particular program as well as to the language
you use to tell this program what to do. When we need to be careful, we
-call the language âthe âawkâ language,â and the program âthe
âawkâ
-utility.â This Info file explains both how to write programs in the
-âawkâ language and how to run the âawkâ utility. The term ââawkâ
-programâ refers to a program written by you in the âawkâ programming
+call the language "the âawkâ language," and the program "the âawkâ
+utility." This Info file explains both how to write programs in the
+âawkâ language and how to run the âawkâ utility. The term "âawkâ
+program" refers to a program written by you in the âawkâ programming
language.
Primarily, this Info file explains the features of âawkâ as defined
@@ -1064,7 +1064,7 @@ it notes any âgawkâ features that are not in the
POSIX standard for
There are sidebars scattered throughout the Info file. They add a
more complete explanation of points that are relevant, but not likely to
be of interest on first reading. All appear in the index, under the
-heading âsidebar.â
+heading "sidebar."
Most of the time, the examples use complete âawkâ programs. Some of
the more advanced minor nodes show only the part of the âawkâ program
@@ -1109,7 +1109,7 @@ in *note Sample Programs::, should be of interest.
record is matched, and the predefined variables âawkâ and
âgawkâ use.
- â *note Arrays::, covers âawkââs one-and-only data structure:
+ â *note Arrays::, covers âawkâ's one-and-only data structure:
the associative array. Deleting array elements and whole
arrays is described, as well as sorting arrays in âgawkâ. The
major node also describes how âgawkâ provides arrays of
@@ -1171,7 +1171,7 @@ in *note Sample Programs::, should be of interest.
to report bugs in âgawkâ and where to get other freely
available âawkâ implementations.
- â *note Notes::, describes how to disable âgawkââs extensions,
+ â *note Notes::, describes how to disable âgawkâ's extensions,
as well as how to contribute new code to âgawkâ, and some
possible future directions for âgawkâ development.
@@ -1181,7 +1181,7 @@ in *note Sample Programs::, should be of interest.
â The *note Glossary::, defines most, if not all, of the
significant terms used throughout the Info file. If you find
- terms that you arenât familiar with, try looking them up here.
+ terms that you aren't familiar with, try looking them up here.
â *note Copying::, and *note GNU Free Documentation License::,
present the licenses that cover the âgawkâ source code and
@@ -1190,7 +1190,7 @@ in *note Sample Programs::, should be of interest.
---------- Footnotes ----------
(1) All such differences appear in the index under the entry
-âdifferences in âawkâ and âgawkâ.â
+"differences in âawkâ and âgawkâ."
File: gawk.info, Node: Conventions, Next: Manual History, Prev: This
Manual, Up: Preface
@@ -1207,9 +1207,9 @@ node briefly documents the typographical conventions used
in Texinfo.
Examples you would type at the command line are preceded by the
common shell primary and secondary prompts, â$â and â>â, respectively.
Input that you type is shown âlike thisâ. Output from the command is
-preceded by the glyph ââ£â. This typically represents the commandâs
-standard output. Error messages and other output on the commandâs
-standard error are preceded by the glyph âerrorââ. For example:
+preceded by the glyph "â£". This typically represents the command's
+standard output. Error messages and other output on the command's
+standard error are preceded by the glyph "errorâ". For example:
$ echo hi on stdout
⣠hi on stdout
@@ -1217,35 +1217,35 @@ standard error are preceded by the glyph
âerrorââ. For example:
errorâ hello on stderr
Characters that you type at the keyboard look âlike thisâ. In
-particular, there are special characters called âcontrol characters.â
+particular, there are special characters called "control characters."
These are characters that you type by holding down both the âCONTROLâ
key and another key, at the same time. For example, a âCtrl-dâ is typed
by first pressing and holding the âCONTROLâ key, next pressing the âdâ
key, and finally releasing both keys.
For the sake of brevity, throughout this Info file, we refer to Brian
-Kernighanâs version of âawkâ as âBWK âawkâ.â (*Note Other
Versions:: for
-information on his and other versions.)
+Kernighan's version of âawkâ as "BWK âawkâ." (*Note Other Versions::
+for information on his and other versions.)
Dark Corners
------------
- Dark corners are basically fractalâno matter how much you
- illuminate, thereâs always a smaller but darker one.
- â _Brian Kernighan_
+ Dark corners are basically fractal--no matter how much you
+ illuminate, there's always a smaller but darker one.
+ -- _Brian Kernighan_
Until the POSIX standard (and âGAWK: Effective AWK Programmingâ),
many features of âawkâ were either poorly documented or not documented
-at all. Descriptions of such features (often called âdark cornersâ) are
-noted in this Info file with â(d.c.).â They also appear in the index
-under the heading âdark corner.â
+at all. Descriptions of such features (often called "dark corners") are
+noted in this Info file with "(d.c.)." They also appear in the index
+under the heading "dark corner."
But, as noted by the opening quote, any coverage of dark corners is
by definition incomplete.
Extensions to the standard âawkâ language that are supported by more
-than one âawkâ implementation are marked â(c.e.),â and listed in the
-index under âcommon extensionsâ and âextensions, common.â
+than one âawkâ implementation are marked "(c.e.)," and listed in the
+index under "common extensions" and "extensions, common."
File: gawk.info, Node: Manual History, Next: How To Contribute, Prev:
Conventions, Up: Preface
@@ -1261,12 +1261,12 @@ editor. GNU Emacs is the most widely used version of
Emacs today.
The GNU(1) Project is an ongoing effort on the part of the Free
Software Foundation to create a complete, freely distributable,
POSIX-compliant computing environment. The FSF uses the GNU General
-Public License (GPL) to ensure that its softwareâs source code is always
+Public License (GPL) to ensure that its software's source code is always
available to the end user. A copy of the GPL is included for your
reference (*note Copying::). The GPL applies to the C language source
code for âgawkâ. To find out more about the FSF and the GNU Project
-online, see the GNU Projectâs home page (https://www.gnu.org). This
-Info file may also be read from GNUâs website
+online, see the GNU Project's home page (https://www.gnu.org). This
+Info file may also be read from GNU's website
(https://www.gnu.org/software/gawk/manual/).
A shell, an editor (Emacs), highly portable optimizing C, C++, and
@@ -1285,12 +1285,12 @@ from the Internet.
Paul Rubin wrote the very first draft of âThe GAWK Manualâ; it was
around 40 pages long. Diane Close and Richard Stallman improved it,
yielding a version that was around 90 pages and barely described the
-original, âoldâ version of âawkâ.
+original, "old" version of âawkâ.
I started working with that version in the fall of 1988. As work on
it progressed, the FSF published several preliminary versions (numbered
0.X). In 1996, edition 1.0 was released with âgawkâ 3.0.0. The FSF
-published the first two editions under the title âThe GNU Awk Userâs
+published the first two editions under the title âThe GNU Awk User's
Guideâ.
This edition maintains the basic structure of the previous editions.
@@ -1308,9 +1308,9 @@ on submitting problem reports electronically.
---------- Footnotes ----------
- (1) GNU stands for âGNUâs Not Unix.â
+ (1) GNU stands for "GNU's Not Unix."
- (2) The terminology âGNU/Linuxâ is explained in the *note Glossary::.
+ (2) The terminology "GNU/Linux" is explained in the *note Glossary::.
File: gawk.info, Node: How To Contribute, Next: Acknowledgments, Prev:
Manual History, Up: Preface
@@ -1331,7 +1331,7 @@ domain. Late in 2017, a volunteer took on the task of
managing it.
If you have written an interesting âawkâ program that you would like
to share with the rest of the world, please see <http://www.awklang.org>
-and use the âContactâ link.
+and use the "Contact" link.
If you have written a âgawkâ extension, please see *note
gawkextlib::.
@@ -1364,7 +1364,7 @@ acknowledgements:
The following people (in alphabetical order) provided helpful
comments on various versions of this book: Rick Adams, Dr. Nelson
H.F. Beebe, Karl Berry, Dr. Michael Brennan, Rich Burridge, Claire
- Cloutier, Diane Close, Scott Deifik, Christopher (âTopherâ) Eliot,
+ Cloutier, Diane Close, Scott Deifik, Christopher ("Topher") Eliot,
Jeffrey Friedl, Dr. Darrel Hankerson, Michal Jaegermann, Dr.
Richard J. LeBlanc, Michael Lijewski, Pat Rankin, Miriam Robbins,
Mary Sheehan, and Chuck Toporek.
@@ -1392,7 +1392,7 @@ acknowledgements:
Ulrich Drepper, provided invaluable help and feedback for the
design of the internationalization features.
- Chuck Toporek, Mary Sheehan, and Claire Cloutier of OâReilly &
+ Chuck Toporek, Mary Sheehan, and Claire Cloutier of O'Reilly &
Associates contributed significant editorial help for this Info
file for the 3.1 release of âgawkâ.
@@ -1401,7 +1401,7 @@ Colombo, Stephen Davies, Scott Deifik, Akim Demaille,
Daniel Richard G.,
Juan Manuel Guerrero, Darrel Hankerson, Michal Jaegermann, Jürgen Kahrs,
Stepan Kasal, John Malmberg, Chet Ramey, Pat Rankin, Andrew Schorr,
Corinna Vinschen, and Eli Zaretskii (in alphabetical order) make up the
-current âgawkâ âcrack portability team.â Without their hard work and
+current âgawkâ "crack portability team." Without their hard work and
help, âgawkâ would not be nearly the robust, portable program it is
today. It has been and continues to be a pleasure working with this
team of fine people.
@@ -1547,7 +1547,7 @@ earlier.
This command format instructs the âshellâ, or command interpreter, to
start âawkâ and use the PROGRAM to process records in the input file(s).
-There are single quotes around PROGRAM so the shell wonât interpret any
+There are single quotes around PROGRAM so the shell won't interpret any
âawkâ characters as special shell characters. The quotes also cause the
shell to treat all of PROGRAM as a single argument for âawkâ, and allow
PROGRAM to be more than one line long.
@@ -1557,7 +1557,7 @@ programs from shell scripts, because it avoids the need
for a separate
file for the âawkâ program. A self-contained shell script is more
reliable because there are no other files to misplace.
- Later in this chapter, in *note Very Simple::, weâll see examples of
+ Later in this chapter, in *note Very Simple::, we'll see examples of
several short, self-contained programs.
@@ -1577,7 +1577,7 @@ end-of-file by typing âCtrl-dâ. (On non-POSIX
operating systems, the
end-of-file character may be different.)
As an example, the following program prints a friendly piece of
-advice (from Douglas Adamsâs âThe Hitchhikerâs Guide to the Galaxyâ),
to
+advice (from Douglas Adams's âThe Hitchhiker's Guide to the Galaxyâ), to
keep you from worrying about the complexities of computer programming:
$ awk 'BEGIN { print "Don\47t Panic!" }'
@@ -1585,7 +1585,7 @@ keep you from worrying about the complexities of computer
programming:
âawkâ executes statements associated with âBEGINâ before reading any
input. If there are no other statements in your program, as is the case
-here, âawkâ just stops, instead of trying to read input it doesnât know
+here, âawkâ just stops, instead of trying to read input it doesn't know
how to process. The â\47â is a magic way (explained later) of getting a
single quote into the program, without having to engage in ugly shell
quoting tricks.
@@ -1637,9 +1637,9 @@ does the same thing as this one:
awk 'BEGIN { print "Don\47t Panic!" }'
-This was explained earlier (*note Read Terminal::). Note that you donât
+This was explained earlier (*note Read Terminal::). Note that you don't
usually need single quotes around the file name that you specify with
-â-fâ, because most file names donât contain any of the shellâs special
+â-fâ, because most file names don't contain any of the shell's special
characters. Notice that in âadviceâ, the âawkâ program did not have
single quotes around it. The quotes are only needed for programs that
are provided on the âawkâ command line. (Also, placing the program in a
@@ -1647,8 +1647,8 @@ file allows us to use a literal single quote in the
program text,
instead of the magic â\47â.)
If you want to clearly identify an âawkâ program file as such, you
-can add the extension â.awkâ to the file name. This doesnât affect the
-execution of the âawkâ program but it does make âhousekeepingâ easier.
+can add the extension â.awkâ to the file name. This doesn't affect the
+execution of the âawkâ program but it does make "housekeeping" easier.
File: gawk.info, Node: Executable Scripts, Next: Comments, Prev: Long, Up:
Running gawk
@@ -1683,7 +1683,7 @@ written in âawkâ.
utility reads your program and then processes your data according to the
instructions in your program. (This is different from a âcompiledâ
language such as C, where your program is first compiled into machine
-code that is executed directly by your systemâs processor.) The âawkâ
+code that is executed directly by your system's processor.) The âawkâ
utility is thus termed an âinterpreterâ. Many modern languages are
interpreted.
@@ -1702,13 +1702,13 @@ characters. Often, this can be dealt with by using a
symbolic link.
You should not put more than one argument on the â#!â line after the
path to âawkâ. It does not work. The operating system treats the rest
of the line as a single argument and passes it to âawkâ. Doing this
-leads to confusing behaviorâmost likely a usage diagnostic of some sort
+leads to confusing behavior--most likely a usage diagnostic of some sort
from âawkâ.
Finally, the value of âARGV[0]â (*note Built-in Variables::) varies
depending upon your operating system. Some systems put âawkâ there,
some put the full pathname of âawkâ (such as â/bin/awkâ), and some put
-the name of your script (âadviceâ). (d.c.) Donât rely on the value of
+the name of your script (âadviceâ). (d.c.) Don't rely on the value of
âARGV[0]â to provide your script name.
---------- Footnotes ----------
@@ -1739,13 +1739,13 @@ put the following into âadviceâ:
BEGIN { print "Don't Panic!" }
You can put comment lines into keyboard-composed throwaway âawkâ
-programs, but this usually isnât very useful; the purpose of a comment
+programs, but this usually isn't very useful; the purpose of a comment
is to help you or another person understand the program when reading it
at a later time.
CAUTION: As mentioned in *note One-shot::, you can enclose short to
medium-sized programs in single quotes, in order to keep your shell
- scripts self-contained. When doing so, _donât_ put an apostrophe
+ scripts self-contained. When doing so, _don't_ put an apostrophe
(i.e., a single quote) into a comment (or anywhere else in your
program). The shell interprets the quote as the closing quote for
the entire program. As a result, usually the shell prints a
@@ -1766,9 +1766,9 @@ at a later time.
errorâ awk: can't open file be
errorâ source line number 1
- Putting a backslash before the single quote in âlet'sâ wouldnât
+ Putting a backslash before the single quote in âlet'sâ wouldn't
help, because backslashes are not special inside single quotes.
- The next node describes the shellâs quoting rules.
+ The next node describes the shell's quoting rules.
File: gawk.info, Node: Quoting, Prev: Comments, Up: Running gawk
@@ -1791,7 +1791,7 @@ it as part of a larger shell script:
Once you are working with the shell, it is helpful to have a basic
knowledge of shell quoting rules. The following rules apply only to
POSIX-compliant, Bourne-style shells (such as Bash, the GNU Bourne-Again
-Shell). If you use the C shell, youâre on your own.
+Shell). If you use the C shell, you're on your own.
Before diving into the rules, we introduce a concept that appears
throughout this Info file, which is that of the ânullâ, or empty,
@@ -1852,7 +1852,7 @@ the quoting rules:
awk -F "" 'PROGRAM' FILES # correct
- Donât use this:
+ Don't use this:
awk -F"" 'PROGRAM' FILES # wrong!
@@ -1870,7 +1870,7 @@ shell quoting tricks, like this:
This program consists of three concatenated quoted strings. The first
and the third are single-quoted, and the second is double-quoted.
- This can be âsimplifiedâ to:
+ This can be "simplified" to:
$ awk 'BEGIN { print "Here is a single quote <'\''>" }'
⣠Here is a single quote <'>
@@ -1909,7 +1909,7 @@ concatenated into a single string that is printed by
âprintâ.)
If you really need both single and double quotes in your âawkâ
program, it is probably best to move it into a separate file, where the
-shell wonât be part of the picture and you can say what you mean.
+shell won't be part of the picture and you can say what you mean.
File: gawk.info, Node: DOS Quoting, Up: Quoting
@@ -1921,7 +1921,7 @@ Although this Info file generally only worries about
POSIX systems and
the POSIX shell, the following issue arises often enough for many users
that it is worth addressing.
- The âshellsâ on Microsoft Windows systems use the double-quote
+ The "shells" on Microsoft Windows systems use the double-quote
character for quoting, and make it difficult or impossible to include an
escaped double-quote character in a command-line script. The following
example, courtesy of Jeroen Brink, shows how to escape the double quotes
@@ -1961,7 +1961,7 @@ the previous example you would do it this way:
However, the use of â\042â instead of â\\\"â is also possible and
easier
to read, because backslashes that are not followed by a double-quote
-donât need duplication.
+don't need duplication.
File: gawk.info, Node: Sample Data Files, Next: Very Simple, Prev: Running
gawk, Up: Getting Started
@@ -1970,7 +1970,7 @@ File: gawk.info, Node: Sample Data Files, Next: Very
Simple, Prev: Running ga
===============================
Many of the examples in this Info file take their input from two sample
-data files. The first, âmail-listâ, represents a list of peoplesâ names
+data files. The first, âmail-listâ, represents a list of peoples' names
together with their email addresses and information about those people.
The second data file, called âinventory-shippedâ, contains information
about monthly shipments. In both files, each line is considered to be
@@ -2033,8 +2033,8 @@ File: gawk.info, Node: Very Simple, Next: Two Rules,
Prev: Sample Data Files,
The following command runs a simple âawkâ program that searches the
input file âmail-listâ for the character string âliâ (a grouping of
characters is usually called a âstringâ; the term âstringâ is based on
-similar usage in English, such as âa string of pearlsâ or âa string of
-cars in a trainâ):
+similar usage in English, such as "a string of pearls" or "a string of
+cars in a train"):
awk '/li/ { print $0 }' mail-list
@@ -2047,7 +2047,7 @@ the same thing, so we could have written that instead.)
for. This type of pattern is called a âregular expressionâ, which is
covered in more detail later (*note Regexp::). The pattern is allowed
to match parts of words. There are single quotes around the âawkâ
-program so that the shell wonât interpret any of it as special shell
+program so that the shell won't interpret any of it as special shell
characters.
Here is what this program prints:
@@ -2071,16 +2071,16 @@ does nothing (i.e., no lines are printed).
Many practical âawkâ programs are just a line or two long. Following
is a collection of useful, short programs to get you started. Some of
-these programs contain constructs that havenât been covered yet. (The
+these programs contain constructs that haven't been covered yet. (The
description of the program will give you a good idea of what is going
-on, but youâll need to read the rest of the Info file to become an âawkâ
+on, but you'll need to read the rest of the Info file to become an âawkâ
expert!) Most of the examples use a data file named âdataâ. This is
just a placeholder; if you use these programs yourself, substitute your
own file names for âdataâ.
Some of the following examples use the output of âls -lâ as input.
âlsâ is a system command that gives you a listing of the files in a
-directory. With the â-lâ option, this listing includes each fileâs size
+directory. With the â-lâ option, this listing includes each file's size
and the date the file was last modified. Its output looks like this:
-rw-r--r-- 1 arnold user 1933 Nov 7 13:05 Makefile
@@ -2094,8 +2094,8 @@ and the date the file was last modified. Its output
looks like this:
The first field contains read-write permissions, the second field
contains the number of links to the file, and the third field identifies
-the fileâs owner. The fourth field identifies the fileâs group. The
-fifth field contains the fileâs size in bytes. The sixth, seventh, and
+the file's owner. The fourth field identifies the file's group. The
+fifth field contains the file's size in bytes. The sixth, seventh, and
eighth fields contain the month, day, and time, respectively, that the
file was last modified. Finally, the ninth field contains the file
name.
@@ -2110,7 +2110,7 @@ things shown here:
awk 'length($0) > 80' data
The sole rule has a relational expression as its pattern and has no
- actionâso it uses the default action, printing the record.
+ action--so it uses the default action, printing the record.
⢠Print the length of the longest input line:
@@ -2118,7 +2118,7 @@ things shown here:
END { print max }' data
The code associated with âENDâ executes after all input has been
- read; itâs the other side of the coin to âBEGINâ.
+ read; it's the other side of the coin to âBEGINâ.
⢠Print the length of the longest line in âdataâ:
@@ -2190,7 +2190,7 @@ contains two rules:
The first rule has the string â12â as the pattern and âprint $0â as the
action. The second rule has the string â21â as the pattern and also has
-âprint $0â as the action. Each ruleâs action is enclosed in its own
+âprint $0â as the action. Each rule's action is enclosed in its own
pair of braces.
This program prints every line that contains the string â12â _or_ the
@@ -2219,10 +2219,10 @@ File: gawk.info, Node: More Complex, Next:
Statements/Lines, Prev: Two Rules,
1.5 A More Complex Example
==========================
-Now that weâve mastered some simple tasks, letâs look at what typical
+Now that we've mastered some simple tasks, let's look at what typical
âawkâ programs do. This example shows how âawkâ can be used to
summarize, select, and rearrange the output of another utility. It uses
-features that havenât been covered yet, so donât worry if you donât
+features that haven't been covered yet, so don't worry if you don't
understand all the details:
ls -l | awk '$6 == "Nov" { sum += $5 }
@@ -2232,11 +2232,11 @@ understand all the details:
current directory that were last modified in November (of any year).
As a reminder, the output of âls -lâ gives you a listing of the files
-in a directory, including each fileâs size and the date the file was
+in a directory, including each file's size and the date the file was
last modified. The first field contains read-write permissions, the
second field contains the number of links to the file, and the third
-field identifies the fileâs owner. The fourth field identifies the
-fileâs group. The fifth field contains the fileâs size in bytes. The
+field identifies the file's owner. The fourth field identifies the
+file's group. The fifth field contains the file's size in bytes. The
sixth, seventh, and eighth fields contain the month, day, and time,
respectively, that the file was last modified. Finally, the ninth field
contains the file name.
@@ -2244,7 +2244,7 @@ contains the file name.
The â$6 == "Nov"â in our âawkâ program is an expression that tests
whether the sixth field of the output from âls -lâ matches the string
âNovâ. Each time a line has the string âNovâ for its sixth field,
âawkâ
-performs the action âsum += $5â. This adds the fifth field (the fileâs
+performs the action âsum += $5â. This adds the fifth field (the file's
size) to the variable âsumâ. As a result, when âawkâ has finished
reading all the input lines, âsumâ is the total of the sizes of the
files whose lines matched the pattern. (This works because âawkâ
@@ -2321,8 +2321,8 @@ split your lines in the middle of a regular expression or
a string.
? }'
⣠hello, world
- Here, the â%â and â?â are the C shellâs primary and secondary
- prompts, analogous to the standard shellâs â$â and â>â.
+ Here, the â%â and â?â are the C shell's primary and secondary
+ prompts, analogous to the standard shell's â$â and â>â.
Compare the previous example to how it is done with a
POSIX-compliant shell:
@@ -2333,7 +2333,7 @@ split your lines in the middle of a regular expression or
a string.
> }'
⣠hello, world
- âawkâ is a line-oriented language. Each ruleâs action has to begin
+ âawkâ is a line-oriented language. Each rule's action has to begin
on the same line as the pattern. To have the pattern and action on
separate lines, you _must_ use backslash continuation; there is no other
option.
@@ -2350,7 +2350,7 @@ comment, it ignores _everything_ on the rest of the line.
For example:
In this case, it looks like the backslash would continue the comment
onto the next line. However, the backslash-newline combination is never
-even noticed because it is âhiddenâ inside the comment. Thus, the
+even noticed because it is "hidden" inside the comment. Thus, the
âBEGINâ is noted as a syntax error.
Backslash continuation comes into play in an additional, unexpected
@@ -2373,7 +2373,7 @@ In short, the backslash and newline are removed,
assigning â"a"â to
â-vâ option (*note Options::) and to regular command-line variable
assignments (*note Assignment Options::).
- If youâre interested, see
+ If you're interested, see
<https://lists.gnu.org/archive/html/bug-gawk/2022-10/msg00025.html> for
a source code patch that allows lines to be continued when inside
parentheses. This patch was not added to âgawkâ since it would quietly
@@ -2427,7 +2427,7 @@ File: gawk.info, Node: When, Next: Intro Summary,
Prev: Other Features, Up:
1.8 When to Use âawkâ
=====================
-Now that youâve seen some of what âawkâ can do, you might wonder how
+Now that you've seen some of what âawkâ can do, you might wonder how
âawkâ could be useful for you. By using utility programs, advanced
patterns, field separators, arithmetic statements, and other selection
criteria, you can produce much more complex output. The âawkâ language
@@ -2445,7 +2445,7 @@ edit-compile-test-debug cycle of software development.
Complex programs have been written in âawkâ, including a complete
retargetable assembler for eight-bit microprocessors (*note Glossary::,
for more information), and a microcode assembler for a special-purpose
-Prolog computer. The original âawkââs capabilities were strained by
+Prolog computer. The original âawkâ's capabilities were strained by
tasks of such complexity, but modern versions are more capable.
If you find yourself writing âawkâ scripts of more than, say, a few
@@ -2465,7 +2465,7 @@ File: gawk.info, Node: Intro Summary, Prev: When, Up:
Getting Started
1.9 Summary
===========
- ⢠Programs in âawkâ consist of PATTERNâACTION pairs.
+ ⢠Programs in âawkâ consist of PATTERN-ACTION pairs.
⢠An ACTION without a PATTERN always runs. The default ACTION for a
pattern without one is â{ print $0 }â.
@@ -2495,13 +2495,13 @@ File: gawk.info, Node: Invoking Gawk, Next: Regexp,
Prev: Getting Started, U
This major node covers how to run âawkâ, both POSIX-standard and
âgawkâ-specific command-line options, and what âawkâ and âgawkâ do
with
nonoption arguments. It then proceeds to cover how âgawkâ searches for
-source files, reading standard input along with other files, âgawkââs
-environment variables, âgawkââs exit status, using include files, and
+source files, reading standard input along with other files, âgawkâ's
+environment variables, âgawkâ's exit status, using include files, and
obsolete and undocumented options and/or features.
Many of the options and features described here are discussed in more
detail later in the Info file; feel free to skip over things in this
-major node that donât interest you right now.
+major node that don't interest you right now.
* Menu:
@@ -2511,7 +2511,7 @@ major node that donât interest you right now.
* Naming Standard Input:: How to specify standard input with other
files.
* Environment Variables:: The environment variables âgawkâ uses.
-* Exit Status:: âgawkââs exit status.
+* Exit Status:: âgawkâ's exit status.
* Include Files:: Including other files into your program.
* Loading Shared Libraries:: Loading shared libraries into your program.
* Obsolete:: Obsolete Options and/or features.
@@ -2524,7 +2524,7 @@ File: gawk.info, Node: Command Line, Next: Options,
Up: Invoking Gawk
2.1 Invoking âawkâ
==================
-There are two ways to run âawkââwith an explicit program or with one or
+There are two ways to run âawkâ--with an explicit program or with one or
more program files. Here are templates for both of them; items enclosed
in [...] in these templates are optional:
@@ -2553,7 +2553,7 @@ long options consist of two dashes and a keyword. The
keyword can be
abbreviated, as long as the abbreviation allows the option to be
uniquely identified. If the option takes an argument, either the
keyword is immediately followed by an equals sign (â=â) and the
-argumentâs value, or the keyword and the argumentâs value are separated
+argument's value, or the keyword and the argument's value are separated
by whitespace (spaces or TABs). If a particular option with a value is
given more than once, it is (usually) the last value that counts.
@@ -2623,7 +2623,7 @@ The following list describes options mandated by the
POSIX standard:
This can often involve converting multibyte characters into wide
characters (internally), and can lead to problems or confusion if
the input data does not contain valid multibyte characters. This
- option is an easy way to tell âgawkâ, âHands off my data!â
+ option is an easy way to tell âgawkâ, "Hands off my data!"
â-câ
â--traditionalâ
@@ -2647,7 +2647,7 @@ The following list describes options mandated by the
POSIX standard:
Having a list of all global variables is a good way to look for
typographical errors in your programs. You would also use this
option if you have a large program with a lot of functions, and you
- want to be sure that your functions donât inadvertently use global
+ want to be sure that your functions don't inadvertently use global
variables that you meant to be local. (This is a particularly easy
mistake to make with simple variable names like âiâ, âjâ, etc.)
@@ -2669,7 +2669,7 @@ The following list describes options mandated by the
POSIX standard:
programs (*note AWKPATH Variable::).
Note that âgawkâ treats each string as if it ended with a newline
- character (even if it doesnât). This makes building the total
+ character (even if it doesn't). This makes building the total
program easier.
CAUTION: Prior to version 5.0, there was no requirement that
@@ -2717,7 +2717,7 @@ The following list describes options mandated by the
POSIX standard:
â-hâ
â--helpâ
- Print a âusageâ message summarizing the short- and long-style
+ Print a "usage" message summarizing the short- and long-style
options that âgawkâ accepts and then exit.
â-iâ SOURCE-FILE
@@ -2741,7 +2741,7 @@ The following list describes options mandated by the
POSIX standard:
â--traceâ
Print the internal byte code names as they are executed when
running the program. The trace is printed to standard error. Each
- âop codeâ is preceded by a â+â sign in the output.
+ "op code" is preceded by a â+â sign in the output.
â-kâ
â--csvâ
@@ -2795,11 +2795,11 @@ The following list describes options mandated by the
POSIX standard:
libraries (*note Arbitrary Precision Arithmetic::).
As of version 5.2, the arbitrary precision arithmetic features in
- âgawkâ are âon parole.â The primary maintainer is no longer
willing
- to support this feature, but another member of the development team
- has stepped up to take it over. As long as this situation remains
- stable, MPFR will be supported. If it changes, the MPFR support
- will be removed from âgawkâ.
+ âgawkâ are "on parole." The primary maintainer is no longer
+ willing to support this feature, but another member of the
+ development team has stepped up to take it over. As long as this
+ situation remains stable, MPFR will be supported. If it changes,
+ the MPFR support will be removed from âgawkâ.
â-nâ
â--non-decimal-dataâ
@@ -2812,7 +2812,7 @@ The following list describes options mandated by the
POSIX standard:
â-Nâ
â--use-lc-numericâ
- Force the use of the localeâs decimal point character when parsing
+ Force the use of the locale's decimal point character when parsing
numeric input data (*note Locales::).
â-oâ[FILE]
@@ -2828,7 +2828,7 @@ The following list describes options mandated by the
POSIX standard:
â-Oâ
â--optimizeâ
- Enable âgawkââs default optimizations on the internal
+ Enable âgawkâ's default optimizations on the internal
representation of the program. At the moment, this includes just
simple constant folding.
@@ -2862,7 +2862,7 @@ The following list describes options mandated by the
POSIX standard:
⢠Specifying â-Ftâ on the command line does not set the value of
âFSâ to be a single TAB character (*note Field Separators::).
- ⢠The localeâs decimal point character is used for parsing input
+ ⢠The locale's decimal point character is used for parsing input
data (*note Locales::).
If you supply both â--traditionalâ and â--posixâ on the command
@@ -2872,12 +2872,12 @@ The following list describes options mandated by the
POSIX standard:
â-râ
â--re-intervalâ
Allow interval expressions (*note Regexp Operators::) in regexps.
- This is now âgawkââs default behavior. Nevertheless, this option
+ This is now âgawkâ's default behavior. Nevertheless, this option
remains for backward compatibility.
â-sâ
â--no-optimizeâ
- Disable âgawkââs default optimizations on the internal
+ Disable âgawkâ's default optimizations on the internal
representation of the program.
â-Sâ
@@ -2887,7 +2887,7 @@ The following list describes options mandated by the
POSIX standard:
extensions. Also, disallow adding file names to âARGVâ that were
not there when âgawkâ started running. This is particularly useful
when you want to run âawkâ scripts from questionable sources and
- need to make sure the scripts canât access your system (other than
+ need to make sure the scripts can't access your system (other than
the specified input data files).
â-tâ
@@ -2953,7 +2953,7 @@ and behaves in strict POSIX mode. If â--lintâ is
supplied on the
command line and âgawkâ turns on POSIX mode because of
âPOSIXLY_CORRECTâ, then it issues a warning message indicating that
POSIX mode is in effect. You would typically set this variable in your
-shellâs startup file. For a Bourne-compatible shell (such as Bash), you
+shell's startup file. For a Bourne-compatible shell (such as Bash), you
would add these lines to the â.profileâ file in your home directory:
POSIXLY_CORRECT=true
@@ -2986,7 +2986,7 @@ File: gawk.info, Node: Other Arguments, Next: Naming
Standard Input, Prev: Op
Any additional arguments on the command line are normally treated as
input files to be processed in the order specified. However, an
argument that has the form âVAR=VALUEâ, assigns the value VALUE to the
-variable VARâit does not specify a file at all. (See *note Assignment
+variable VAR--it does not specify a file at all. (See *note Assignment
Options::.) In the following example, âcount=1â is a variable
assignment, not a file name:
@@ -3028,10 +3028,10 @@ escape sequences (*note Escape Sequences::). (d.c.)
In some very early implementations of âawkâ, when a variable
assignment occurred before any file names, the assignment would happen
-_before_ the âBEGINâ rule was executed. âawkââs behavior was thus
+_before_ the âBEGINâ rule was executed. âawkâ's behavior was thus
inconsistent; some command-line assignments were available inside the
âBEGINâ rule, while others were not. Unfortunately, some applications
-came to depend upon this âfeature.â When âawkâ was changed to be more
+came to depend upon this "feature." When âawkâ was changed to be more
consistent, the â-vâ option was added to accommodate applications that
depended upon the old behavior.
@@ -3051,7 +3051,7 @@ compatibility.
Quoting Shell Variables On The âawkâ Command Line
Small âawkâ programs are often embedded in larger shell scripts, so
-itâs worthwhile to understand some shell basics. Consider the
+it's worthwhile to understand some shell basics. Consider the
following:
f=""
@@ -3061,8 +3061,8 @@ following:
open any command line files. To the unwary, this looks like âawkâ is
hanging.
- However âawkâ doesnât see an explicit empty string. When a variable
-expansion is the null string, _and_ itâs not quoted, the shell simply
+ However âawkâ doesn't see an explicit empty string. When a variable
+expansion is the null string, _and_ it's not quoted, the shell simply
removes it from the command line. To demonstrate:
$ f=""
@@ -3150,7 +3150,7 @@ true for both â--traditionalâ and â--posixâ.
*Note Options::.
If the source code file is not found after the initial search, the
path is searched again after adding the suffix â.awkâ to the file name.
- âgawkââs path search mechanism is similar to the shellâs. (See
âThe
+ âgawkâ's path search mechanism is similar to the shell's. (See âThe
Bourne-Again SHell manualâ (https://www.gnu.org/software/bash/manual/).)
It treats a null entry in the path as indicating the current directory.
(A null entry is indicated by starting or ending the path with a colon
@@ -3178,7 +3178,7 @@ to manipulate the âAWKPATHâ variable.
value from within an âawkâ program.
Although you can change âENVIRON["AWKPATH"]â within your âawkâ
-program, this has no effect on the running programâs behavior. This
+program, this has no effect on the running program's behavior. This
makes sense: the âAWKPATHâ environment variable is used to find the
program source files. Once your program is running, all the files have
been found, and âgawkâ no longer needs to use âAWKPATHâ.
@@ -3191,7 +3191,7 @@ been found, and âgawkâ no longer needs to use
âAWKPATHâ.
depend upon how âgawkâ was built and installed. The actual directory is
the value of â$(pkgdatadir)â generated when âgawkâ was configured.
(For
more detail, see the âINSTALLâ file in the source distribution, and see
-*note Quick Installation::. You probably donât need to worry about
+*note Quick Installation::. You probably don't need to worry about
this, though.)
@@ -3222,7 +3222,7 @@ to manipulate the âAWKLIBPATHâ variable.
value from within an âawkâ program.
Although you can change âENVIRON["AWKLIBPATH"]â within your âawkâ
-program, this has no effect on the running programâs behavior. This
+program, this has no effect on the running program's behavior. This
makes sense: the âAWKLIBPATHâ environment variable is used to find any
requested extensions, and they are loaded before the program starts to
run. Once your program is running, all the extensions have been found,
@@ -3234,7 +3234,7 @@ and âgawkâ no longer needs to use âAWKLIBPATHâ.
depend upon how âgawkâ was built and installed. The actual directory is
the value of â$(pkgextensiondir)â generated when âgawkâ was configured.
(For more detail, see the âINSTALLâ file in the source distribution, and
-see *note Quick Installation::. You probably donât need to worry about
+see *note Quick Installation::. You probably don't need to worry about
this, though.)
@@ -3243,7 +3243,7 @@ File: gawk.info, Node: Other Environment Variables,
Prev: AWKLIBPATH Variable,
2.5.3 Other Environment Variables
---------------------------------
-A number of other environment variables affect âgawkââs behavior, but
+A number of other environment variables affect âgawkâ's behavior, but
they are more specialized. Those in the following list are meant to be
used by regular users:
@@ -3254,7 +3254,7 @@ used by regular users:
âGAWK_PERSIST_FILEâ
Specifies the backing file to use for persistent storage of
- âgawkââs variables and arrays. *Note Persistent Memory::.
+ âgawkâ's variables and arrays. *Note Persistent Memory::.
âGAWK_READ_TIMEOUTâ
Specifies the time, in milliseconds, for âgawkâ to wait for input
@@ -3284,8 +3284,8 @@ change. The variables are:
size of the memory buffer to allocate for I/O. Otherwise, the value
should be a number, and âgawkâ uses that number as the size of the
buffer to allocate. (When this variable is not set, âgawkâ uses
- the smaller of the fileâs size and the âdefaultâ blocksize, which
- is usually the filesystemâs I/O blocksize.)
+ the smaller of the file's size and the "default" blocksize, which
+ is usually the filesystem's I/O blocksize.)
âAWK_HASHâ
If this variable exists with a value of âgstâ, âgawkâ switches to
@@ -3314,11 +3314,11 @@ change. The variables are:
âGAWK_NO_DFAâ
If this variable exists, âgawkâ does not use the DFA regexp matcher
- for âdoes it matchâ kinds of tests. This can cause âgawkâ to be
+ for "does it match" kinds of tests. This can cause âgawkâ to be
slower. Its purpose is to help isolate differences between the two
- regexp matchers that âgawkâ uses internally. (There arenât
+ regexp matchers that âgawkâ uses internally. (There aren't
supposed to be differences, but occasionally theory and practice
- donât coordinate with each other.)
+ don't coordinate with each other.)
âGAWK_STACKSIZEâ
This specifies the amount by which âgawkâ should grow its internal
@@ -3340,7 +3340,7 @@ change. The variables are:
File: gawk.info, Node: Exit Status, Next: Include Files, Prev: Environment
Variables, Up: Invoking Gawk
-2.6 âgawkââs Exit Status
+2.6 âgawkâ's Exit Status
========================
If the âexitâ statement is used with a value (*note Exit Statement::),
@@ -3373,7 +3373,7 @@ files. These files can be used just like function
libraries, using the
variable. Note that source files may also be included using the â-iâ
option.
- Letâs see an example. Weâll start with two (trivial) âawkâ scripts,
+ Let's see an example. We'll start with two (trivial) âawkâ scripts,
namely âtest1â and âtest2â. Here is the âtest1â script:
BEGIN {
@@ -3433,7 +3433,7 @@ Variable::) apply to â@includeâ also.
This is very helpful in constructing âgawkâ function libraries. If
you have a large script with useful, general-purpose âawkâ functions,
you can break it down into library files and put those files in a
-special directory. You can then include those âlibraries,â either by
+special directory. You can then include those "libraries," either by
using the full pathnames of the files, or by setting the âAWKPATHâ
environment variable accordingly and then using â@includeâ with just the
file part of the full pathname. Of course, you can keep library files
@@ -3474,7 +3474,7 @@ to extended capabilities not supported by the âawkâ
language. The
â@loadâ is completely equivalent to using the â-lâ command-line option.
If the extension is not initially found in âAWKLIBPATHâ, another
-search is conducted after appending the platformâs default shared
+search is conducted after appending the platform's default shared
library suffix to the file name. For example, on GNU/Linux systems, the
suffix â.soâ is used:
@@ -3506,7 +3506,7 @@ version or are still supported but deprecated (meaning
that they will
_not_ be in a future release).
As of âgawkâ version 5.2. the arbitrary precision arithmetic feature
-is âon parole.â This feature is now being supported by a volunteer in
+is "on parole." This feature is now being supported by a volunteer in
the development team and not by the primary maintainer. If this
situation changes, then the feature will be removed. For more
information see *note MPFR On Parole::.
@@ -3518,7 +3518,7 @@ File: gawk.info, Node: Undocumented, Next: Invoking
Summary, Prev: Obsolete,
======================================
Use the Source, Luke!
- â _Obi-Wan_
+ -- _Obi-Wan_
This minor node intentionally left blank.
@@ -3575,7 +3575,7 @@ File: gawk.info, Node: Invoking Summary, Prev:
Undocumented, Up: Invoking Gaw
âAWKPATHâ, âAWKLIBPATHâ, and âPOSIXLY_CORRECTâ are the most
important ones.
- ⢠âgawkââs exit status conveys information to the program that
+ ⢠âgawkâ's exit status conveys information to the program that
invoked it. Use the âexitâ statement from within an âawkâ program
to set the exit status.
@@ -3714,7 +3714,7 @@ sequences apply to both string constants and regexp
constants:
A literal backslash, â\â.
â\aâ
- The âalertâ character, âCtrl-gâ, ASCII code 7 (BEL). (This often
+ The "alert" character, âCtrl-gâ, ASCII code 7 (BEL). (This often
makes some sort of audible noise.)
â\bâ
@@ -3742,7 +3742,7 @@ sequences apply to both string constants and regexp
constants:
â\xHH...â
The hexadecimal value HH, where HH stands for a sequence of
- hexadecimal digits (â0âââ9â, and either âAâââFâ or
âaâââfâ). A
+ hexadecimal digits (â0â-â9â, and either âAâ-âFâ or
âaâ-âfâ). A
maximum of two digits are allowed after the â\xâ. Any further
hexadecimal digits are treated as simple letters or numbers.
(c.e.) (The â\xâ escape sequence is not allowed in POSIX awk.)
@@ -3757,18 +3757,18 @@ sequences apply to both string constants and regexp
constants:
â\uHH...â
The hexadecimal value HH, where HH stands for a sequence of one or
- more hexadecimal digits (â0âââ9â, and either âAâââFâ
or âaâââfâ).
+ more hexadecimal digits (â0â-â9â, and either âAâ-âFâ or
âaâ-âfâ).
A maximum of eight digits are allowed after the â\uâ. Any further
hexadecimal digits are treated as simple letters or numbers.
(c.e.) (The â\uâ escape sequence is not allowed in POSIX awk.)
This escape sequence is intended for designating a character in the
- current localeâs character set.(1) âgawkâ first converts the given
- digits into an integer and then translates the given âwide
- characterâ value into the current localeâs multibyte encoding. If
+ current locale's character set.(1) âgawkâ first converts the given
+ digits into an integer and then translates the given "wide
+ character" value into the current locale's multibyte encoding. If
the wide character value does not represent a valid character, or
if the character is valid but cannot be encoded into the current
- localeâs multibyte encoding, the value becomes â"?"â. âgawkâ
+ locale's multibyte encoding, the value becomes â"?"â. âgawkâ
issues a warning message when this happens.
â\/â
@@ -3847,7 +3847,7 @@ Thus, â/a\52b/â is equivalent to â/a\*b/â.
---------- Footnotes ----------
- (1) Typically, this is a Unicode-based locale, but it doesnât have to
+ (1) Typically, this is a Unicode-based locale, but it doesn't have to
be.
@@ -4008,14 +4008,13 @@ concatenation, and finally by â|â. As in
arithmetic, parentheses can
change how operators are grouped.
According to the POSIX specification, when â*â, â+â, â?â, or
â{â are
-not preceded by a character, the behavior is âundefined.â In practice,
+not preceded by a character, the behavior is "undefined." In practice,
for âgawkâ, the â*â, â+â, â?â and â{â operators stand for
themselves
when there is nothing in the regexp that precedes them. For example,
â/+/â matches a literal plus sign. However, many other versions of
âawkâ treat such a usage as a syntax error.
What About The Empty Regexp?
-
We describe here an advanced regexp usage. Feel free to skip it upon
first reading.
@@ -4081,7 +4080,7 @@ stand for themselves.
As mentioned, interval expressions were not traditionally available
in âawkâ. In March of 2019, BWK âawkâ (finally) acquired them.
-Starting with version 5.2, âgawkââs â--traditionalâ option no longer
+Starting with version 5.2, âgawkâ's â--traditionalâ option no longer
disables interval expressions in regular expressions.
POSIX says that interval expressions containing repetition counts
@@ -4103,7 +4102,7 @@ This same caveat applies to âgawkâ.
---------- Footnotes ----------
- (1) Use two backslashes if youâre using a string constant with a
+ (1) Use two backslashes if you're using a string constant with a
regexp operator or function.
@@ -4117,7 +4116,7 @@ those listed between the opening and closing square
brackets.
Within a bracket expression, a ârange expressionâ consists of two
characters separated by a hyphen. It matches any single character that
-sorts between the two characters, based upon the systemâs native
+sorts between the two characters, based upon the system's native
character set. For example, â[0-9]â is equivalent to â[0123456789]â.
(See *note Ranges and Locales:: for an explanation of how the POSIX
standard and âgawkâ have changed over time. This is mainly of
@@ -4127,7 +4126,7 @@ historical interest.)
(http://www.unicode.org), there is an additional wrinkle to consider.
Octal and hexadecimal escape sequences inside bracket expressions are
taken to represent only single-byte characters (characters whose values
-fit within the range 0â256). To match a range of characters where the
+fit within the range 0-256). To match a range of characters where the
endpoints of the range are larger than 256, enter the multibyte
encodings of the characters directly.
@@ -4158,7 +4157,6 @@ a bracket expression. Character classes consist of
â[:â, a keyword
denoting the class, and â:]â. *note Table 3.1: table-char-classes.
lists the character classes defined by the POSIX standard.
-
Class Meaning
--------------------------------------------------------------------------
â[:alnum:]â Alphanumeric characters
@@ -4202,7 +4200,7 @@ These apply to non-ASCII character sets, which can have
single symbols
(called âcollating elementsâ) that are represented with more than one
character. They can also have several characters that are equivalent
for âcollatingâ, or sorting, purposes. (For example, in French, a plain
-âeâ and a grave-accented âèâ are equivalent.) These sequences are:
+"e" and a grave-accented "è" are equivalent.) These sequences are:
Collating symbols
Multicharacter collating elements enclosed between â[.â and â.]â.
@@ -4213,7 +4211,7 @@ Collating symbols
Equivalence classes
Locale-specific names for a list of characters that are equal. The
name is enclosed between â[=â and â=]â. For example, the name
âeâ
- might be used to represent all of âe,â âê,â âè,â and
âé.â In this
+ might be used to represent all of "e," "ê," "è," and "é." In this
case, â[[=e=]]â is a regexp that matches any of âeâ, âêâ,
âéâ, or
âèâ.
@@ -4241,8 +4239,8 @@ Consider the following:
This example uses the âsub()â function to make a change to the input
record. (âsub()â replaces the first instance of any text matched by the
first argument with the string provided as the second argument; *note
-String Functions::.) Here, the regexp â/a+/â indicates âone or more
âaâ
-characters,â and the replacement text is â<A>â.
+String Functions::.) Here, the regexp â/a+/â indicates "one or more
âaâ
+characters," and the replacement text is â<A>â.
The input contains four âaâ characters. âawkâ (and POSIX) regular
expressions always match the leftmost, _longest_ sequence of input
@@ -4300,8 +4298,8 @@ type â"\\*"â. The first backslash escapes the second
one so that the
string actually contains the two characters â\â and â*â.
Given that you can use both regexp and string constants to describe
-regular expressions, which should you use? The answer is âregexp
-constants,â for several reasons:
+regular expressions, which should you use? The answer is "regexp
+constants," for several reasons:
⢠String constants are more complicated to write and more difficult
to read. Using regexp constants makes your programs less
@@ -4336,8 +4334,8 @@ used inside a bracket expression for a dynamic regexp:
⣠here is a sample line
Ctrl-d
- âgawkâ does not have this problem, and it isnât likely to occur often
-in practice, but itâs worth noting for future reference.
+ âgawkâ does not have this problem, and it isn't likely to occur often
+in practice, but it's worth noting for future reference.
File: gawk.info, Node: GNU Regexp Operators, Next: Case-sensitivity, Prev:
Computed Regexps, Up: Regexp
@@ -4361,7 +4359,7 @@ letters, digits, or underscores (â_â):
current locale. Think of it as shorthand for â[^[:space:]]â.
â\wâ
- Matches any word-constituent characterâthat is, it matches any
+ Matches any word-constituent character--that is, it matches any
letter, digit, or underscore. Think of it as shorthand for
â[[:alnum:]_]â.
@@ -4387,7 +4385,7 @@ letters, digits, or underscores (â_â):
characters. For example, â/\Brat\B/â matches âcrateâ, but it does
not match âdirty ratâ. â\Bâ is essentially the opposite of
â\yâ.
Another way to think of this is that â\Bâ matches the empty string
- provided itâs not at the edge of a word.
+ provided it's not at the edge of a word.
There are two other operators that work on buffers. In Emacs, a
âbufferâ is, naturally, an Emacs buffer. Other GNU programs, including
@@ -4401,11 +4399,11 @@ operators are:
Matches the empty string at the end of a buffer (string)
Because â^â and â$â always work in terms of the beginning and end of
-strings, these operators donât add any new capabilities for âawkâ. They
+strings, these operators don't add any new capabilities for âawkâ. They
are provided for compatibility with other GNU software.
In other GNU software, the word-boundary operator is â\bâ. However,
-that conflicts with the âawkâ languageâs definition of â\bâ as
+that conflicts with the âawkâ language's definition of â\bâ as
backspace, so âgawkâ uses a different letter. An alternative method
would have been to require two backslashes in the GNU operators, but
this was deemed too confusing. The current method of using â\yâ for the
@@ -4447,13 +4445,13 @@ expressions. Thus, a âwâ in a regular expression
matches only a
lowercase âwâ and not an uppercase âWâ.
The simplest way to do a case-independent match is to use a bracket
-expressionâfor example, â[Ww]â. However, this can be cumbersome if you
+expression--for example, â[Ww]â. However, this can be cumbersome if you
need to use it often, and it can make the regular expressions harder to
read. There are two alternatives that you might prefer.
One way to perform a case-insensitive match at a particular point in
the program is to convert the data to a single case, using the
-âtolower()â or âtoupper()â built-in string functions (which we
havenât
+âtolower()â or âtoupper()â built-in string functions (which we haven't
discussed yet; *note String Functions::). For example:
tolower($1) ~ /foo/ { ... }
@@ -4489,11 +4487,11 @@ dynamically turn case sensitivity on or off for all the
rules at once.
insensitive without having to edit it.
In multibyte locales, the equivalences between upper- and lowercase
-characters are tested based on the wide-character values of the localeâs
+characters are tested based on the wide-character values of the locale's
character set. Prior to version 5.0, single-byte characters were tested
based on the ISO-8859-1 (ISO Latin-1) character set. However, as of
version 5.0, single-byte characters are also tested based on the values
-of the localeâs character set.(2)
+of the locale's character set.(2)
The value of âIGNORECASEâ has no effect if âgawkâ is in
compatibility
mode (*note Options::). Case is always significant in compatibility
@@ -4504,9 +4502,9 @@ mode.
(1) Experienced C and C++ programmers will note that it is possible,
using something like âIGNORECASE = 1 && /foObAr/ { ... }â and
âIGNORECASE = 0 || /foobar/ { ... }â. However, this is somewhat obscure
-and we donât recommend it.
+and we don't recommend it.
- (2) If you donât understand this, donât worry about it; it just means
+ (2) If you don't understand this, don't worry about it; it just means
that âgawkâ does the right thing.
@@ -4542,7 +4540,7 @@ File: gawk.info, Node: Regexp Summary, Prev:
Case-sensitivity, Up: Regexp
⢠Matching expressions may use dynamic regexps (i.e., string values
treated as regular expressions).
- ⢠âgawkââs âIGNORECASEâ variable lets you control the case
+ ⢠âgawkâ's âIGNORECASEâ variable lets you control the case
sensitivity of regexp matching. In other âawkâ versions, use
âtolower()â or âtoupper()â.
@@ -4646,8 +4644,8 @@ BEGIN/END::). For example:
{ print $0 }' mail-list
changes the value of âRSâ to âuâ, before reading any input. The new
-value is a string whose first character is the letter âuâ; as a result,
-records are separated by the letter âuâ. Then the input file is read,
+value is a string whose first character is the letter "u"; as a result,
+records are separated by the letter "u". Then the input file is read,
and the second rule in the âawkâ program (the action with no pattern)
prints each record. Because each âprintâ statement adds a newline at
the end of its output, this âawkâ program copies the input with each
âuâ
@@ -4789,11 +4787,10 @@ text, such as âRS = "abc(XYZ)?"â, it is possible,
due to implementation
constraints, that âgawkâ may match the leading part of the regular
expression, but not the trailing part, particularly if the input text
that could match the trailing part is fairly long. âgawkâ attempts to
-avoid this problem, but currently, thereâs no guarantee that this will
+avoid this problem, but currently, there's no guarantee that this will
never happen.
Caveats When Using Regular Expressions for âRSâ
-
Remember that in âawkâ, the â^â and â$â anchor metacharacters
match
the beginning and end of a _string_, and not the beginning and end of a
_line_. As a result, something like âRS = "^[[:upper:]]"â can only
@@ -4818,10 +4815,9 @@ value of âRSâ determines the end of the record.
however.
âRS = "\0"â Is Not Portable
-
There are times when you might want to treat an entire data file as a
single record. The only way to make this happen is to give âRSâ a value
-that you know doesnât occur in the input file. This is hard to do in a
+that you know doesn't occur in the input file. This is hard to do in a
general way, such that a program always works for arbitrary input files.
You might think that for text files, the NUL character, which
@@ -4869,8 +4865,8 @@ languages (such as formfeed, vertical tab, etc.) are
_not_ considered
whitespace by âawkâ.
The purpose of fields is to make it more convenient for you to refer
-to these pieces of the record. You donât have to use themâyou can
-operate on the whole record if you wantâbut fields are what make simple
+to these pieces of the record. You don't have to use them--you can
+operate on the whole record if you want--but fields are what make simple
âawkâ programs so powerful.
You use a dollar sign (â$â) to refer to a field in an âawkâ program,
@@ -4895,7 +4891,7 @@ field in a record can be represented by â$NFâ. So,
â$NFâ is the same as
last one (such as â$8â when the record has only seven fields), you get
the empty string. If used in a numeric operation, you get zero.(1)
- The use of â$0â, which looks like a reference to the âzerothâ field,
+ The use of â$0â, which looks like a reference to the "zeroth" field,
is a special case: it represents the whole input record. Use it when
you are not interested in specific fields. Here are some more examples:
@@ -4959,11 +4955,11 @@ not allowed; trying to reference one usually terminates
the program.
negative field number. âgawkâ notices this and terminates your program.
Other âawkâ implementations may behave differently.)
- As mentioned in *note Fields::, âawkâ stores the current recordâs
+ As mentioned in *note Fields::, âawkâ stores the current record's
number of fields in the built-in variable âNFâ (also *note Built-in
-Variables::). Thus, the expression â$NFâ is not a special featureâit is
-the direct consequence of evaluating âNFâ and using its value as a field
-number.
+Variables::). Thus, the expression â$NFâ is not a special feature--it
+is the direct consequence of evaluating âNFâ and using its value as a
+field number.
---------- Footnotes ----------
@@ -5024,12 +5020,12 @@ range. For example:
⣠301
...
-Weâve just created â$6â, whose value is the sum of fields â$2â,
â$3â,
+We've just created â$6â, whose value is the sum of fields â$2â,
â$3â,
â$4â, and â$5â. The â+â sign represents addition. For the file
âinventory-shippedâ, â$6â represents the total number of parcels
shipped
for a particular month.
- Creating a new field changes âawkââs internal copy of the current
+ Creating a new field changes âawkâ's internal copy of the current
input record, which is the value of â$0â. Thus, if you do âprint $0â
after adding a field, the record printed includes the new field, with
the appropriate number of field separators between it and the previously
@@ -5052,7 +5048,7 @@ out-of-range field only produces an empty string. For
example:
print "everything is normal"
should print âeverything is normalâ, because âNF+1â is certain to be
out
-of range. (*Note If Statement:: for more information about âawkââs
+of range. (*Note If Statement:: for more information about âawkâ's
âif-elseâ statements. *Note Typing and Comparison:: for more
information about the â!=â operator.)
@@ -5086,7 +5082,7 @@ value of âNFâ and recomputes â$0â. (d.c.) Here
is an example:
⣠NF = 6
⣠a b c
- CAUTION: Some versions of âawkâ donât rebuild â$0â when
âNFâ is
+ CAUTION: Some versions of âawkâ don't rebuild â$0â when âNFâ
is
decremented. Until August, 2018, this included BWK âawkâ;
fortunately his version now handles this correctly.
@@ -5098,7 +5094,7 @@ rebuild the entire record, using the current values of
the fields and
print $0 # or whatever else with $0
This forces âawkâ to rebuild the record. It does help to add a comment,
-as weâve shown here.
+as we've shown here.
There is a flip side to the relationship between â$0â and the fields.
Any assignment to â$0â causes the record to be reparsed into fields
@@ -5172,9 +5168,9 @@ Given the input line:
this âawkâ program extracts and prints the string ââ¢29â¢Oakâ¢St.â.
- Sometimes the input data contains separator characters that donât
+ Sometimes the input data contains separator characters that don't
separate fields the way you thought they would. For instance, the
-personâs name in the example we just used might have a title or suffix
+person's name in the example we just used might have a title or suffix
attached, such as:
John Q. Smith: LXIX: 29 Oak St.: Walamazoo: MI 42139
@@ -5199,7 +5195,7 @@ containing a single space, â" "â. If âawkâ
interpreted this value in
the usual way, each space character would separate fields, so two spaces
in a row would make an empty field between them. The reason this does
not happen is that a single space as the value of âFSâ is a special
-caseâit is taken to specify the default manner of delimiting fields.
+case--it is taken to specify the default manner of delimiting fields.
If âFSâ is any other single character, such as â","â, then each
occurrence of that character separates two fields. Two consecutive
@@ -5330,7 +5326,7 @@ although RFC 4180 (http://www.ietf.org/rfc/rfc4180) lists
the common
practices.
For decades, anyone wishing to work with CSV files and âawkâ had to
-âroll their ownâ solution. (For an example, *note Splitting By
+"roll their own" solution. (For an example, *note Splitting By
Content::). In 2023, Brian Kernighan decided to add CSV support to his
version of âawkâ. In order to keep up, âgawkâ too provides the same
support as his version. To use CSV data, invoke âgawkâ with either of
@@ -5344,7 +5340,6 @@ quotes represent an actual double quote. The double
quote that starts a
quoted field must be the first character after the comma. *note Table
4.1: table-csv-examples. shows some examples.
-
Input Field Contents
----------------------------------------------
âabc defâ âabc defâ
@@ -5355,7 +5350,7 @@ Input Field Contents
Table 4.1: Examples of CSV data
- Additionally, and hereâs where it gets messy, newlines are also
+ Additionally, and here's where it gets messy, newlines are also
allowed inside double-quoted fields! In order to deal with such things,
when processing CSV files, âgawkâ scans the input data looking for
newlines that are not enclosed in double quotes. Thus, use of the
@@ -5363,13 +5358,12 @@ newlines that are not enclosed in double quotes. Thus,
use of the
(*note Records::), as well as field splitting with any of âFSâ,
âFIELDWIDTHSâ, or âFPATâ.
- Carriage-ReturnâLine-Feed Line Endings In CSV Files
-
+ Carriage-Return-Line-Feed Line Endings In CSV Files
â\r\nâ is the invention of the devil.
- â _Brian Kernighan_
+ -- _Brian Kernighan_
Many CSV files are imported from systems where the line terminator
-for text files is a carriage-returnâline-feed pair (CR-LF, â\râ followed
+for text files is a carriage-return-line-feed pair (CR-LF, â\râ followed
by â\nâ). For ease of use, when processing CSV files, âgawkâ converts
CR-LF pairs into a single newline. That is, the â\râ is removed.
@@ -5431,12 +5425,12 @@ and not âtâs. Use â-v FS="t"â or â-F"[t]"â
on the command line if y
really do want to separate your fields with âtâs. Use â-F '\t'â when
not in compatibility mode to specify that TABs separate fields.
- As an example, letâs use an âawkâ program file called âedu.awkâ
that
+ As an example, let's use an âawkâ program file called âedu.awkâ that
contains the pattern â/edu/â and the action âprint $1â:
/edu/ { print $1 }
- Letâs also set âFSâ to be the â-â character and run the program on
+ Let's also set âFSâ to be the â-â character and run the program on
the file âmail-listâ. The following command prints a list of the names
of the people that work at or attend a university, and the first three
digits of their phone numbers:
@@ -5451,7 +5445,7 @@ looked like this:
Jean-Paul 555-2127 jeanpaul.campanorum@nyu.edu R
- The â-â as part of the personâs name was used as the field separator,
+ The â-â as part of the person's name was used as the field separator,
instead of the â-â in the phone number that was originally intended.
This demonstrates why you have to be careful in choosing your field and
record separators.
@@ -5460,8 +5454,8 @@ record separators.
separator occurs when processing the Unix system password file. On many
Unix systems, each user has a separate entry in the system password
file, with one line per user. The information in these lines is
-separated by colons. The first field is the userâs login name and the
-second is the userâs encrypted or shadow password. (A shadow password
+separated by colons. The first field is the user's login name and the
+second is the user's encrypted or shadow password. (A shadow password
is indicated by the presence of a single âxâ in the second field.) A
password file entry might look like this:
@@ -5478,7 +5472,7 @@ File: gawk.info, Node: Full Line Fields, Next: Field
Splitting Summary, Prev:
4.5.6 Making the Full Line Be a Single Field
--------------------------------------------
-Occasionally, itâs useful to treat the whole input line as a single
+Occasionally, it's useful to treat the whole input line as a single
field. This can be done easily and portably simply by setting âFSâ to
â"\n"â (a newline):(1)
@@ -5517,7 +5511,7 @@ first line of the file, something like:
(1) Thanks to Andrew Schorr for this tip.
- (2) The âsedâ utility is a âstream editor.â Its behavior is also
+ (2) The âsedâ utility is a "stream editor." Its behavior is also
defined by the POSIX standard.
@@ -5530,12 +5524,12 @@ It is important to remember that when you assign a
string constant as
the value of âFSâ, it undergoes normal âawkâ string processing. For
example, with Unix âawkâ and âgawkâ, the assignment âFS = "\.."â
assigns
the character string â".."â to âFSâ (the backslash is stripped). This
-creates a regexp meaning âfields are separated by occurrences of any two
-characters.â If instead you want fields to be separated by a literal
+creates a regexp meaning "fields are separated by occurrences of any two
+characters." If instead you want fields to be separated by a literal
period followed by any single character, use âFS = "\\.."â.
The following list summarizes how fields are split, based on the
-value of âFSâ (â==â means âis equal toâ):
+value of âFSâ (â==â means "is equal to"):
âgawk was invoked with --csvâ
Field splitting follows the rules given in *note Comma Separated
@@ -5610,7 +5604,7 @@ did not anticipate the use of their output as input for
other programs.
An example of the latter is a table where all the columns are lined
up by the use of a variable number of spaces and _empty fields are just
-spaces_. Clearly, âawkââs normal field splitting based on âFSâ does
not
+spaces_. Clearly, âawkâ's normal field splitting based on âFSâ does
not
work well in this case. Although a portable âawkâ program can use a
series of âsubstr()â calls on â$0â (*note String Functions::), this is
awkward and inefficient for a large number of fields.
@@ -5658,7 +5652,7 @@ calculated idle time:
}
NOTE: The preceding program uses a number of âawkâ features that
- havenât been introduced yet.
+ haven't been introduced yet.
Running the program on the data produces the following results:
@@ -5715,8 +5709,8 @@ There are times when fixed-width data may be followed by
additional data
that has no fixed length. Such data may or may not be present, but if
it is, it should be possible to get at it from an âawkâ program.
- Starting with version 4.2, in order to provide a way to say âanything
-else in the record after the defined fields,â âgawkâ allows you to add a
+ Starting with version 4.2, in order to provide a way to say "anything
+else in the record after the defined fields," âgawkâ allows you to add a
final â*â character to the value of âFIELDWIDTHSâ. There can only be
one such character, and it must be the final non-whitespace character in
âFIELDWIDTHSâ. For example:
@@ -5735,7 +5729,7 @@ File: gawk.info, Node: Fields with fixed data, Prev:
Allowing trailing data,
4.6.4 Field Values With Fixed-Width Data
----------------------------------------
-So far, so good. But what happens if there isnât as much data as there
+So far, so good. But what happens if there isn't as much data as there
should be based on the contents of âFIELDWIDTHSâ? Or, what happens if
there is more data than expected?
@@ -5749,7 +5743,7 @@ Enough data for some fields
Not enough data for a field
For example, if âFIELDWIDTHSâ is set to â"2 3 4"â and the input
record is âaabâ. In this case, âNFâ is set to two and â$2â
has the
- value â"b"â. The idea is that even though there arenât as many
+ value â"b"â. The idea is that even though there aren't as many
characters as were expected, there are some, so the data should be
made available to the program.
@@ -5791,7 +5785,7 @@ what they are, and not by what they are not.
The most notorious such case is comma-separated values (CSV) data.
Many spreadsheet programs, for example, can export their data into text
files, where each record is terminated with a newline, and fields are
-separated by commas. If commas only separated the data, there wouldnât
+separated by commas. If commas only separated the data, there wouldn't
be an issue. The problem comes when one of the fields contains an
_embedded_ comma. In such cases, most programs embed the field in
double quotes.(1) So, we might have data like this:
@@ -5803,10 +5797,10 @@ of âFPATâ should be a string that provides a
regular expression. This
regular expression describes the contents of each field.
In the case of CSV data as presented here, each field is either
-âanything that is not a comma,â or âa double quote, anything that is not
-a double quote, and a closing double quote.â (There are more complicated
-definitions of CSV data, treated shortly.) If written as a regular
-expression constant (*note Regexp::), we would have
+"anything that is not a comma," or "a double quote, anything that is not
+a double quote, and a closing double quote." (There are more
+complicated definitions of CSV data, treated shortly.) If written as a
+regular expression constant (*note Regexp::), we would have
â/([^,]+)|("[^"]+")/â. Writing this as a string requires us to escape
the double quotes, leading to:
@@ -5850,7 +5844,7 @@ would be to remove the quotes when they occur, with
something like this:
NOTE: Some programs export CSV data that contains embedded newlines
between the double quotes. âgawkâ provides no way to deal with
this. Even though a formal specification for CSV data exists,
- there isnât much more to be done; the âFPATâ mechanism provides an
+ there isn't much more to be done; the âFPATâ mechanism provides an
elegant solution for the majority of cases, and the âgawkâ
developers are satisfied with that.
@@ -5933,9 +5927,9 @@ And here is his test program:
⣠NF = 3 <p><><s>
In general, using âFPATâ to do your own CSV parsing is like having a
-bed with a blanket thatâs not quite big enough. Thereâs always a corner
-that isnât covered. We recommend, instead, that you use Manuel
-Colladoâs âCSVMODEâ library for âgawkâ
(http://mcollado.z15.es/xgawk/).
+bed with a blanket that's not quite big enough. There's always a corner
+that isn't covered. We recommend, instead, that you use Manuel
+Collado's âCSVMODEâ library for âgawkâ (http://mcollado.z15.es/xgawk/).
File: gawk.info, Node: FS versus FPAT, Prev: More CSV, Up: Splitting By
Content
@@ -5943,14 +5937,14 @@ File: gawk.info, Node: FS versus FPAT, Prev: More
CSV, Up: Splitting By Conte
4.7.2 âFSâ Versus âFPATâ: A Subtle Difference
---------------------------------------------
-As we discussed earlier, âFSâ describes the data between fields (âwhat
-fields are notâ) and âFPATâ describes the fields themselves (âwhat
-fields areâ). This leads to a subtle difference in how fields are found
+As we discussed earlier, âFSâ describes the data between fields ("what
+fields are not") and âFPATâ describes the fields themselves ("what
+fields are"). This leads to a subtle difference in how fields are found
when using regexps as the value for âFSâ or âFPATâ.
In order to distinguish one field from another, there must be a
non-empty separator between each field. This makes intuitive
-senseâotherwise one could not distinguish fields from separators.
+sense--otherwise one could not distinguish fields from separators.
Thus, regular expression matching as done when splitting fields with
âFSâ is not allowed to match the null string; it must always match at
@@ -5970,9 +5964,9 @@ File: gawk.info, Node: Testing field creation, Next:
Multiple Line, Prev: Spl
4.8 Checking How âgawkâ Is Splitting Records
============================================
-As weâve seen, âgawkâ provides three independent methods to split input
+As we've seen, âgawkâ provides three independent methods to split input
records into fields. The mechanism used is based on which of the three
-variablesââFSâ, âFIELDWIDTHSâ, or âFPATââwas last assigned to.
In
+variables--âFSâ, âFIELDWIDTHSâ, or âFPATâ--was last assigned to.
In
addition, an API input parser may choose to override the record parsing
mechanism; please refer to *note Input Parsers:: for further information
about this feature.
@@ -6018,13 +6012,13 @@ records. For example, you could use the formfeed
character (written
â\fâ in âawkâ, as in C) to separate them, making each record a page of
the file. To do this, just set the variable âRSâ to â"\f"â (a string
containing the formfeed character). Any other character could equally
-well be used, as long as it wonât be part of the data in a record.
+well be used, as long as it won't be part of the data in a record.
Another technique is to have blank lines separate records. By a
special dispensation, an empty string as the value of âRSâ indicates
that records are separated by one or more blank lines. When âRSâ is set
to the empty string, each record always ends at the first blank line
-encountered. The next record doesnât start until the first nonblank
+encountered. The next record doesn't start until the first nonblank
line that follows. No matter how many blank lines appear in a row, they
all act as one record separator. (Blank lines must be completely empty;
lines that contain only whitespace do not count.)
@@ -6034,7 +6028,7 @@ lines that contain only whitespace do not count.)
record and one or more blank lines after the record. In addition, a
regular expression always matches the longest possible sequence when
there is a choice (*note Leftmost Longest::). So, the next record
-doesnât start until the first nonblank line that followsâno matter how
+doesn't start until the first nonblank line that follows--no matter how
many blank lines appear in a row, they are considered one record
separator.
@@ -6063,7 +6057,7 @@ whatever field separations result from âFSâ.
The original motivation for this special exception was probably to
provide useful behavior in the default case (i.e., âFSâ is equal to
-â" "â). This feature can be a problem if you really donât want the
+â" "â). This feature can be a problem if you really don't want the
newline character to separate fields, because there is no way to prevent
it. However, you can work around this by using the âsplit()â function
to break up the record manually (*note String Functions::). If you have
@@ -6118,7 +6112,7 @@ A simple program to process this file is as follows:
*Note Labels Program:: for a more realistic program dealing with
address lists. The following list summarizes how records are split,
-based on the value of âRSâ. (â==â means âis equal to.â)
+based on the value of âRSâ. (â==â means "is equal to.")
âRS == "\n"â
Records are separated by the newline character (â\nâ). In effect,
@@ -6152,8 +6146,8 @@ File: gawk.info, Node: Getline, Next: Read Timeout,
Prev: Multiple Line, Up:
4.10 Explicit Input with âgetlineâ
==================================
-So far we have been getting our input data from âawkââs main input
-streamâeither the standard input (usually your keyboard, sometimes the
+So far we have been getting our input data from âawkâ's main input
+stream--either the standard input (usually your keyboard, sometimes the
output from another program) or the files specified on the command line.
The âawkâ language has a special built-in command called âgetlineâ that
can be used to read input under your explicit control.
@@ -6206,7 +6200,7 @@ File: gawk.info, Node: Plain Getline, Next:
Getline/Variable, Up: Getline
The âgetlineâ command can be used without arguments to read input from
the current input file. All it does in this case is read the next input
-record and split it up into fields. This is useful if youâve finished
+record and split it up into fields. This is useful if you've finished
processing the current record, but want to do some special processing on
the next record _right now_. For example:
@@ -6232,7 +6226,7 @@ the next record _right now_. For example:
}
This âawkâ program deletes C-style comments (â/* ... */â) from the
-input. It uses a number of features we havenât covered yet, including
+input. It uses a number of features we haven't covered yet, including
string concatenation (*note Concatenation::) and the âindex()â and
âsubstr()â built-in functions (*note String Functions::). By replacing
the âprint $0â with other statements, you could perform more complicated
@@ -6273,7 +6267,7 @@ File: gawk.info, Node: Getline/Variable, Next:
Getline/File, Prev: Plain Getl
4.10.2 Using âgetlineâ into a Variable
--------------------------------------
-You can use âgetline VARâ to read the next record from âawkââs input
+You can use âgetline VARâ to read the next record from âawkâ's input
into the variable VAR. No other processing is done. For example,
suppose the next line is a comment or a special string, and you want to
read it without triggering any rules. This form of âgetlineâ allows you
@@ -6393,7 +6387,7 @@ File: gawk.info, Node: Getline/Pipe, Next:
Getline/Variable/Pipe, Prev: Getli
Omniscience has much to recommend it. Failing that, attention to
details would be useful.
- â _Brian Kernighan_
+ -- _Brian Kernighan_
The output of a command can also be piped into âgetlineâ, using
âCOMMAND | getlineâ. In this case, the string COMMAND is run as a shell
@@ -6442,7 +6436,7 @@ value of âNFâ, and recomputes the value of â$0â.
The values of âNRâ
âFNRâ are not changed. âRTâ is set.
According to POSIX, âEXPRESSION | getlineâ is ambiguous if EXPRESSION
-contains unparenthesized operators other than â$ââfor example, â"echo "
+contains unparenthesized operators other than â$â--for example, â"echo "
"date" | getlineâ is ambiguous because the concatenation operator is not
parenthesized. You should write it as â("echo " "date") | getlineâ if
you want your program to be portable to all âawkâ implementations.
@@ -6453,7 +6447,7 @@ you want your program to be portable to all âawkâ
implementations.
"date") | getlineâ. (This is also how BWK âawkâ behaves.) Some
versions instead treat it as â"echo " ("date" | getline)â. (This
is how âmawkâ behaves.) In short, _always_ use explicit
- parentheses, and then you wonât have to worry.
+ parentheses, and then you won't have to worry.
File: gawk.info, Node: Getline/Variable/Pipe, Next: Getline/Coprocess,
Prev: Getline/Pipe, Up: Getline
@@ -6560,8 +6554,8 @@ in mind:
⢠Using âFILENAMEâ with âgetlineâ (âgetline < FILENAMEâ) is
likely to
be a source of confusion. âawkâ opens a separate input stream from
the current input file. However, by not using a variable, â$0â and
- âNFâ are still updated. If youâre doing this, itâs probably by
- accident, and you should reconsider what it is youâre trying to
+ âNFâ are still updated. If you're doing this, it's probably by
+ accident, and you should reconsider what it is you're trying to
accomplish.
⢠*note Getline Summary::, presents a table summarizing the âgetlineâ
@@ -6572,7 +6566,7 @@ in mind:
⢠If the variable being assigned is an expression with side effects,
different versions of âawkâ behave differently upon encountering
- end-of-file. Some versions donât evaluate the expression; many
+ end-of-file. Some versions don't evaluate the expression; many
versions (including âgawkâ) do. Here is an example, courtesy of
Duncan Moore:
@@ -6601,7 +6595,6 @@ of âgetlineâ, listing which predefined variables are
set by each one,
and whether the variant is standard or a âgawkâ extension. Note: for
each variant, âgawkâ sets the âRTâ predefined variable.
-
Variant Effect âawkâ / âgawkâ
-------------------------------------------------------------------------
âgetlineâ Sets â$0â, âNFâ, âFNRâ, âawkâ
@@ -6686,7 +6679,7 @@ input to arrive:
NOTE: You should not assume that the read operation will block
exactly after the tenth record has been printed. It is possible
- that âgawkâ will read and buffer more than one recordâs worth of
+ that âgawkâ will read and buffer more than one record's worth of
data the first time. Because of this, changing the value of
timeout like in the preceding example is not very useful.
@@ -6844,7 +6837,7 @@ File: gawk.info, Node: Input Exercises, Prev: Input
Summary, Up: Reading File
1. Using the âFIELDWIDTHSâ variable (*note Constant Size::), write a
program to read election data, where each record represents one
- voterâs votes. Come up with a way to define which columns are
+ voter's votes. Come up with a way to define which columns are
associated with each ballot item, and print the total votes,
including abstentions, for each item.
@@ -6858,11 +6851,11 @@ One of the most common programming actions is to
âprintâ, or output,
some or all of the input. Use the âprintâ statement for simple output,
and the âprintfâ statement for fancier formatting. The âprintâ
statement is not limited when computing _which_ values to print.
-However, with two exceptions, you cannot specify _how_ to print themâhow
-many columns, whether to use exponential notation or not, and so on.
-(For the exceptions, *note Output Separators:: and *note OFMT::.) For
-printing with specifications, you need the âprintfâ statement (*note
-Printf::).
+However, with two exceptions, you cannot specify _how_ to print
+them--how many columns, whether to use exponential notation or not, and
+so on. (For the exceptions, *note Output Separators:: and *note
+OFMT::.) For printing with specifications, you need the âprintfâ
+statement (*note Printf::).
Besides basic and formatted printing, this major node also covers I/O
redirections to files and pipes, introduces the special file names that
@@ -6919,7 +6912,7 @@ probably get an error. Keep in mind that a space is
printed between any
two items.
Note that the âprintâ statement is a statement and not an
-expressionâyou canât use it in the pattern part of a patternâaction
+expression--you can't use it in the pattern part of a pattern-action
statement, for example.
@@ -6929,7 +6922,7 @@ File: gawk.info, Node: Print Examples, Next: Output
Separators, Prev: Print,
==============================
Each âprintâ statement makes at least one line of output. However, it
-isnât limited to only one line. If an item value is a string containing
+isn't limited to only one line. If an item value is a string containing
a newline, the newline is output along with the rest of the string. A
single âprintâ statement can make any number of lines this way.
@@ -6965,8 +6958,8 @@ Here is the same program, without the comma:
...
To someone unfamiliar with the âinventory-shippedâ file, neither
-exampleâs output makes much sense. A heading line at the beginning
-would make it clearer. Letâs add some headings to our table of months
+example's output makes much sense. A heading line at the beginning
+would make it clearer. Let's add some headings to our table of months
(â$1â) and green crates shipped (â$2â). We do this using a
âBEGINâ rule
(*note BEGIN/END::) so that the headings are only printed once:
@@ -6983,7 +6976,7 @@ When run, the program prints the following:
Mar 15
...
-The only problem, however, is that the headings and the table data donât
+The only problem, however, is that the headings and the table data don't
line up! We can fix this by printing some spaces between the two
fields:
@@ -7009,7 +7002,7 @@ File: gawk.info, Node: Output Separators, Next: OFMT,
Prev: Print Examples,
As mentioned previously, a âprintâ statement contains a list of items
separated by commas. In the output, the items are normally separated by
-single spaces. However, this doesnât need to be the case; a single
+single spaces. However, this doesn't need to be the case; a single
space is simply the default. Any string of characters may be used as
the âoutput field separatorâ by setting the predefined variable âOFSâ.
The initial value of this variable is the string â" "â (i.e., a single
@@ -7055,7 +7048,7 @@ with a blank line added after each newline:
⣠Jean-Paul;555-2127
â£
- If the value of âORSâ does not contain a newline, the programâs
+ If the value of âORSâ does not contain a newline, the program's
output runs together on a single line.
@@ -7090,7 +7083,7 @@ provided in *note Strings And Numbers::. In particular,
for âprintâ,
âawkâ uses the value of âOFMTâ instead of that of âCONVFMTâ, but
otherwise behaves exactly the same as described in that minor node.
-According to the POSIX standard, âawkââs behavior is undefined if
âOFMTâ
+According to the POSIX standard, âawkâ's behavior is undefined if
âOFMTâ
contains anything but a floating-point conversion specification. (d.c.)
@@ -7134,7 +7127,7 @@ stringâ.
The format string is very similar to that in the ISO C library
function âprintf()â. Most of FORMAT is text to output verbatim.
-Scattered among this text are âformat specifiersââone per item. Each
+Scattered among this text are âformat specifiersâ--one per item. Each
format specifier says to output the next item in the argument list at
that place in the format.
@@ -7160,7 +7153,7 @@ File: gawk.info, Node: Control Letters, Next: Format
Modifiers, Prev: Basic P
----------------------------
A format specifier starts with the character â%â and ends with a
-âformat-control letterââit tells the âprintfâ statement how to output
+âformat-control letterâ--it tells the âprintfâ statement how to output
one item. The format-control letter specifies what _kind_ of value to
print. The rest of the format specifier is made up of optional
âmodifiersâ that control _how_ to print the value, such as the field
@@ -7174,7 +7167,7 @@ width. Here is a list of the format-control letters:
NOTE: The current POSIX standard requires support for â%aâ and
â%Aâ in âawkâ. As far as we know, besides âgawkâ, the
only
other version of âawkâ that actually implements it is BWK
- âawkâ. Itâs use is thus highly nonportable!
+ âawkâ. It's use is thus highly nonportable!
Furthermore, these formats are not available on any system
where the underlying C library âprintf()â function does not
@@ -7198,7 +7191,7 @@ width. Here is a list of the format-control letters:
Other âawkâ versions generally restrict themselves to printing
the first byte of a string or to numeric values within the
- range of a single byte (0â255). (d.c.)
+ range of a single byte (0-255). (d.c.)
â%dâ, â%iâ
Print a decimal integer. The two control letters are equivalent.
@@ -7226,15 +7219,15 @@ width. Here is a list of the format-control letters:
On systems supporting IEEE 754 floating-point format, values
representing negative infinity are formatted as â-infâ or
â-infinityâ, and positive infinity as âinfâ or âinfinityâ.
The
- special ânot a numberâ value formats as â-nanâ or ânanâ (*note
+ special "not a number" value formats as â-nanâ or ânanâ (*note
Strange values::).
â%Fâ
- Like â%fâ, but the infinity and ânot a numberâ values are spelled
+ Like â%fâ, but the infinity and "not a number" values are spelled
using uppercase letters.
The â%Fâ format is a POSIX extension to ISO C; not all systems
- support it. On those that donât, âgawkâ uses â%fâ instead.
+ support it. On those that don't, âgawkâ uses â%fâ instead.
â%gâ, â%Gâ
Print a number in either scientific notation or in floating-point
@@ -7269,8 +7262,8 @@ width. Here is a list of the format-control letters:
entirely. (d.c.)
NOTE: The IEEE 754 standard for floating-point arithmetic allows
- for special values that represent âinfinityâ (positive and
- negative) and values that are ânot a numberâ (NaN).
+ for special values that represent "infinity" (positive and
+ negative) and values that are "not a number" (NaN).
Input and output of these values occurs as text strings. This is
somewhat problematic for the âawkâ language, which predates the
@@ -7284,9 +7277,9 @@ File: gawk.info, Node: Format Modifiers, Next: Printf
Examples, Prev: Control
------------------------------------
A format specification can also include âmodifiersâ that can control how
-much of the itemâs value is printed, as well as how much space it gets.
+much of the item's value is printed, as well as how much space it gets.
The modifiers come between the â%â and the format-control letter. We
-use the bullet symbol ââ¢â in the following examples to represent spaces
+use the bullet symbol "â¢" in the following examples to represent spaces
in the output. Here are the possible modifiers, in the order in which
they may appear:
@@ -7303,7 +7296,7 @@ they may appear:
prints the famous friendly message twice.
- At first glance, this feature doesnât seem to be of much use. It
+ At first glance, this feature doesn't seem to be of much use. It
is in fact a âgawkâ extension, intended for use in translating
messages at runtime. *Note Printf Ordering::, which describes how
and why to use positional specifiers. For now, we ignore them.
@@ -7329,7 +7322,7 @@ SPACE
modifier.
â#â
- Use an âalternative formâ for certain control letters. For â%oâ,
+ Use an "alternative form" for certain control letters. For â%oâ,
supply a leading zero. For â%xâ and â%Xâ, supply a leading
â0xâ or
â0Xâ for a nonzero result. For â%eâ, â%Eâ, â%fâ, and
â%Fâ, the
result always contains a decimal point. For â%gâ and â%Gâ,
@@ -7408,7 +7401,7 @@ WIDTH
prints âfoobâ.
- The C library âprintfââs dynamic WIDTH and PREC capability (e.g.,
+ The C library âprintfâ's dynamic WIDTH and PREC capability (e.g.,
â"%*.*s"â) is supported. Instead of supplying explicit WIDTH and/or
PREC values in the format string, they are passed in the argument list.
For example:
@@ -7474,8 +7467,8 @@ the numbers are separated by dashes. Printing the phone
numbers as
numbers would have produced just the first three digits: â555â. This
would have been pretty confusing.
- It wasnât necessary to specify a width for the phone numbers because
-they are last on their lines. They donât need to have spaces after
+ It wasn't necessary to specify a width for the phone numbers because
+they are last on their lines. They don't need to have spaces after
them.
The table could be made to look even nicer by adding headings to the
@@ -7540,7 +7533,7 @@ work identically for âprintfâ:
same OUTPUT-FILE do not erase OUTPUT-FILE, but append to it. (This
is different from how you use redirections in shell scripts.) If
OUTPUT-FILE does not exist, it is created. For example, here is
- how an âawkâ program can write a list of peoplesâ names to one file
+ how an âawkâ program can write a list of peoples' names to one file
named âname-listâ, and a list of phone numbers to another file
named âphone-listâ:
@@ -7573,7 +7566,7 @@ work identically for âprintfâ:
The redirection argument COMMAND is actually an âawkâ expression.
Its value is converted to a string whose contents give the shell
command to be run. For example, the following produces two files,
- one unsorted list of peoplesâ names, and one list sorted in reverse
+ one unsorted list of peoples' names, and one list sorted in reverse
alphabetical order:
awk '{ print $1 > "names.unsorted"
@@ -7593,12 +7586,12 @@ work identically for âprintfâ:
print("at record number", FNR, "of", FILENAME) | report
close(report)
- The âclose()â function is called here because itâs a good idea to
+ The âclose()â function is called here because it's a good idea to
close the pipe as soon as all the intended output has been sent to
it. *Note Close Files And Pipes:: for more information.
This example also illustrates the use of a variable to represent a
- FILE or COMMANDâit is not necessary to always use a string
+ FILE or COMMAND--it is not necessary to always use a string
constant. Using a variable is generally a good idea, because (if
you mean to refer to that same file or command) âawkâ requires that
the string value be written identically every time.
@@ -7629,7 +7622,7 @@ a file, and then to use â>>â for subsequent output:
print "Avoid improbability generators" >> "guide.txt"
This is indeed how redirections must be used from the shell. But in
-âawkâ, it isnât necessary. In this kind of case, a program should use
+âawkâ, it isn't necessary. In this kind of case, a program should use
â>â for all the âprintâ statements, because the output file is only
opened once. (It happens that if you mix â>â and â>>â output is
produced in the expected order. However, mixing the operators for the
@@ -7688,13 +7681,13 @@ error message to standard error in an âawkâ program
is as follows:
This works by opening a pipeline to a shell command that can access the
standard error stream that it inherits from the âawkâ process. This is
far from elegant, and it also requires a separate process. So people
-writing âawkâ programs often donât do this. Instead, they send the
+writing âawkâ programs often don't do this. Instead, they send the
error messages to the screen, like this:
print "Serious error detected!" > "/dev/tty"
(â/dev/ttyâ is a special file supplied by the operating system that is
-connected to your keyboard and screen. It represents the âterminal,â(1)
+connected to your keyboard and screen. It represents the "terminal,"(1)
which on modern systems is a keyboard and screen, not a serial console.)
This generally has the same effect, but not always: although the
standard error stream is usually the screen, it can be redirected; when
@@ -7734,7 +7727,7 @@ option (*note Options::).
---------- Footnotes ----------
- (1) The âttyâ in â/dev/ttyâ stands for âTeletype,â a serial
terminal.
+ (1) The "tty" in â/dev/ttyâ stands for "Teletype," a serial terminal.
File: gawk.info, Node: Special Files, Next: Close Files And Pipes, Prev:
Special FD, Up: Printing
@@ -7855,7 +7848,7 @@ or:
The argument FILENAME or COMMAND can be any expression. Its value
must _exactly_ match the string that was used to open the file or start
-the command (spaces and other âirrelevantâ characters included). For
+the command (spaces and other "irrelevant" characters included). For
example, if you open a pipe with this:
"sort -r names" | getline foo
@@ -7885,7 +7878,7 @@ programs. Here are some of the reasons for closing an
output file:
with âgetlineâ.
⢠To write numerous files, successively, in the same âawkâ program.
- If the files arenât closed, eventually âawkâ may exceed a system
+ If the files aren't closed, eventually âawkâ may exceed a system
limit on the number of open files in one process. It is best to
close each one when the program has finished writing it.
@@ -7907,7 +7900,7 @@ programs. Here are some of the reasons for closing an
output file:
If you use more files than the system allows you to have open, âgawkâ
attempts to multiplex the available open files among your data files.
-âgawkââs ability to do this depends upon the facilities of your
+âgawkâ's ability to do this depends upon the facilities of your
operating system, so it may not always work. It is therefore both good
practice and good portability advice to always use âclose()â on your
files when you are done with them. In fact, if you are using a lot of
@@ -7938,7 +7931,7 @@ represent a file, pipe, or coprocess that was opened with
a redirection.
In such a case, it returns a negative value, indicating an error. In
addition, âgawkâ sets âERRNOâ to a string indicating the error.
- Note also that âclose(FILENAME)â has no âmagicâ effects on the
+ Note also that âclose(FILENAME)â has no "magic" effects on the
implicit loop that reads through the files named on the command line.
It is, more likely, a close of a file that was never opened with a
redirection, so âawkâ silently does nothing, except return a negative
@@ -7957,13 +7950,13 @@ more detail and gives an example.
---------- Footnotes ----------
(1) The technical terminology is rather morbid. The finished child
-is called a âzombie,â and cleaning up after it is referred to as
-âreaping.â
+is called a "zombie," and cleaning up after it is referred to as
+"reaping."
File: gawk.info, Node: Close Return Value, Up: Close Files And Pipes
-5.9.1 Using âclose()ââs Return Value
+5.9.1 Using âclose()â's Return Value
------------------------------------
In many older versions of Unix âawkâ, the âclose()â function is
actually
@@ -7984,15 +7977,14 @@ problem.
coprocess (input or output), the return value is the exit status of the
command, as described in *note Table 5.1:
table-close-pipe-return-values.(1) Otherwise, it is the return value
-from the systemâs âclose()â or âfclose()â C functions when closing
input
+from the system's âclose()â or âfclose()â C functions when closing
input
or output files, respectively. This value is zero if the close
succeeds, or â1 if it fails. Recent versions of BWK âawkâ also return
the same values from âclose()â.
-
Situation Return value from âclose()â
--------------------------------------------------------------------------
-Normal exit of command Commandâs exit status
+Normal exit of command Command's exit status
Death by signal of command 256 + number of murderous signal
Death by signal of command with 512 + number of murderous signal
core dump
@@ -8023,7 +8015,7 @@ This minor node describes a âgawkâ-specific feature.
Normally, when you send data down a pipeline to a command with
âprintâ or âprintfâ, âgawkâ âflushesâ the output down the
pipe. That
is, output is not buffered, but written directly. This assures, that
-pipeline output intermixed with âgawkââs output comes out in the
+pipeline output intermixed with âgawkâ's output comes out in the
expected order:
print "something" # goes to standard output
@@ -8040,7 +8032,7 @@ expensive.
âgawkâ will buffer data for all pipelines.
⢠Set âPROCINFO["COMMAND", "BUFFERPIPE"]â to any value. In this
- case, only COMMANDâs data will be fully buffered.
+ case, only COMMAND's data will be fully buffered.
You _must_ create one or the other of these elements in âPROCINFOâ
before the first âprintâ or âprintfâ to the pipeline. Doing so after
@@ -8105,7 +8097,7 @@ For standard output, you may use âPROCINFO["-",
"NONFATAL"]â or
When attempting to open a TCP/IP socket (*note TCP/IP Networking::),
âgawkâ tries multiple times. The âGAWK_SOCK_RETRIESâ environment
variable (*note Other Environment Variables::) allows you to override
-âgawkââs builtin default number of attempts. However, once nonfatal I/O
+âgawkâ's builtin default number of attempts. However, once nonfatal I/O
is enabled for a given socket, âgawkâ only retries once, relying on
âawkâ-level code to notice that there was a problem.
@@ -8183,7 +8175,7 @@ operators.
* Menu:
* Values:: Constants, Variables, and Regular Expressions.
-* All Operators:: âgawkââs operators.
+* All Operators:: âgawkâ's operators.
* Truth Values and Conditions:: Testing for true and false.
* Function Calls:: A function call is an expression.
* Precedence:: How various operators nest.
@@ -8219,7 +8211,7 @@ same value. There are three types of constants: numeric,
string, and
regular expression.
Each is used in the appropriate context when you need a data value
-that isnât going to change. Numeric constants can have different forms,
+that isn't going to change. Numeric constants can have different forms,
but are internally stored in an identical manner.
* Menu:
@@ -8281,7 +8273,7 @@ an error if you try to do so. For example:
⣠gawk: cmd. line:1: BEGIN { print "hello,
⣠gawk: cmd. line:1: ^ syntax error
- Although POSIX doesnât define what happens if you use an escaped
+ Although POSIX doesn't define what happens if you use an escaped
newline, as in the previous C example, all known versions of âawkâ allow
you to do so. Unfortunately, what each one does with such a string
varies. (d.c.) âgawkâ, âmawkâ, and the OpenSolaris POSIX âawkâ
(*note
@@ -8323,12 +8315,12 @@ octal (base 8) and hexadecimal (base 16). In octal,
the numbers go 0,
1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on. Just as â11â in decimal is
1 times 10 plus 1, so â11â in octal is 1 times 8 plus 1. This equals 9
in decimal. In hexadecimal, there are 16 digits. Because the everyday
-decimal number system only has ten digits (â0âââ9â), the letters
âaâ
+decimal number system only has ten digits (â0â-â9â), the letters
âaâ
through âfâ represent the rest. (Case in the letters is usually
irrelevant; hexadecimal âaâ and âAâ have the same value.) Thus,
â11â in
hexadecimal is 1 times 16 plus 1, which equals 17 in decimal.
- Just by looking at plain â11â, you canât tell what base itâs in.
So,
+ Just by looking at plain â11â, you can't tell what base it's in. So,
in C, C++, and other languages derived from C, there is a special
notation to signify the base. Octal numbers start with a leading â0â,
and hexadecimal numbers start with a leading â0xâ or â0Xâ:
@@ -8374,7 +8366,7 @@ octal constants. For example, âgawkâ treats
â018â as decimal 18:
If âgawkâ is in compatibility mode (*note Options::), they are not
available.
- A Constantâs Base Does Not Affect Its Value
+ A Constant's Base Does Not Affect Its Value
Once a numeric constant has been converted internally into a number,
âgawkâ no longer remembers what the original form of the constant was;
@@ -8442,7 +8434,7 @@ author probably intended:
# Note that /foo/ is on the left of the ~
if (/foo/ ~ $1) print "found foo"
-This code is âobviouslyâ testing â$1â for a match against the regexp
+This code is "obviously" testing â$1â for a match against the regexp
â/foo/â. But in fact, the expression â/foo/ ~ $1â really means â($0
~
/foo/) ~ $1â. In other words, first match the input record against the
regexp â/foo/â. The result is either zero or one, depending upon the
@@ -8504,9 +8496,9 @@ This minor node describes a âgawkâ-specific feature.
As we saw in the previous minor node, regexp constants (â/.../â) hold
a strange position in the âawkâ language. In most contexts, they act
like an expression: â$0 ~ /.../â. In other contexts, they denote only a
-regexp to be matched. In no case are they really a âfirst class
-citizenâ of the language. That is, you cannot define a scalar variable
-whose type is âregexpâ in the same sense that you can define a variable
+regexp to be matched. In no case are they really a "first class
+citizen" of the language. That is, you cannot define a scalar variable
+whose type is "regexp" in the same sense that you can define a variable
to be a number or a string:
num = 42 Numeric variable
@@ -8617,10 +8609,10 @@ names. Case is significant in variable names; âaâ
and âAâ are distinct
variables.
A variable name is a valid expression by itself; it represents the
-variableâs current value. Variables are given new values with
+variable's current value. Variables are given new values with
âassignment operatorsâ, âincrement operatorsâ, and âdecrement
operatorsâ
(*note Assignment Ops::). In addition, the âsub()â and âgsub()â
-functions can change a variableâs value, and the âmatch()â,
âsplit()â,
+functions can change a variable's value, and the âmatch()â, âsplit()â,
and âpatsplit()â functions can change the contents of their array
parameters (*note String Functions::).
@@ -8629,7 +8621,7 @@ field separator) and âNFâ (the number of fields in
the current input
record). *Note Built-in Variables:: for a list of the predefined
variables. These predefined variables can be used and assigned just
like all other variables, but their values are also used or changed
-automatically by âawkâ. All predefined variablesâ names are entirely
+automatically by âawkâ. All predefined variables' names are entirely
uppercase.
Variables in âawkâ can be assigned either numeric or string values.
@@ -8662,7 +8654,7 @@ execute. The â-vâ option and its assignment must
precede all the file
name arguments, as well as the program text. (*Note Options:: for more
information about the â-vâ option.) Otherwise, the variable assignment
is performed at a time determined by its position among the input file
-argumentsâafter the processing of the preceding input file argument.
+arguments--after the processing of the preceding input file argument.
For example:
awk '{ print $n }' n=4 inventory-shipped n=2 mail-list
@@ -8689,10 +8681,10 @@ processes the values of command-line assignments for
escape sequences
Normally, variables assigned on the command line (with or without the
â-vâ option) are treated as strings. When such variables are used as
-numbers, âawkââs normal automatic conversion of strings to numbers takes
-place, and everything âjust works.â
+numbers, âawkâ's normal automatic conversion of strings to numbers takes
+place, and everything "just works."
- However, âgawkâ supports variables whose types are âregexpâ. You
can
+ However, âgawkâ supports variables whose types are "regexp". You can
assign variables of this type using the following syntax:
gawk -v 're1=@/foo|bar/' '...' /path/to/file1 're2=@/baz|quux/'
/path/to/file2
@@ -8742,7 +8734,7 @@ string, concatenate that number with the empty string,
â""â. To force a
string to be converted to a number, add zero to that string. A string
is converted to a number by interpreting any numeric prefix of the
string as numerals: â"2.5"â converts to 2.5, â"1e3"â converts to 1,000,
-and â"25fix"â has a numeric value of 25. Strings that canât be
+and â"25fix"â has a numeric value of 25. Strings that can't be
interpreted as valid numbers convert to zero.
The exact manner in which numbers are converted into strings is
@@ -8750,13 +8742,13 @@ controlled by the âawkâ predefined variable
âCONVFMTâ (*note Built-in
Variables::). Numbers are converted using the âsprintf()â function with
âCONVFMTâ as the format specifier (*note String Functions::).
- âCONVFMTââs default value is â"%.6g"â, which creates a value with
at
+ âCONVFMTâ's default value is â"%.6g"â, which creates a value with at
most six significant digits. For some applications, you might want to
change it to specify more precision. On most modern machines, 17 digits
-is usually enough to capture a floating-point numberâs value exactly.(1)
+is usually enough to capture a floating-point number's value exactly.(1)
Strange results can occur if you set âCONVFMTâ to a string that
-doesnât tell âsprintf()â how to format floating-point numbers in a
+doesn't tell âsprintf()â how to format floating-point numbers in a
useful way. For example, if you forget the â%â in the format, âawkâ
converts all numbers to the same constant string.
@@ -8771,7 +8763,6 @@ value of âCONVFMTâ may be. Given the following code
fragment:
âbâ has the value â"12"â, not â"12.00"â. (d.c.)
Pre-POSIX âawkâ Used âOFMTâ for String Conversion
-
Prior to the POSIX standard, âawkâ used the value of âOFMTâ for
converting numbers to strings. âOFMTâ specifies the output format to
use when printing numbers with âprintâ. âCONVFMTâ was introduced in
@@ -8793,11 +8784,11 @@ File: gawk.info, Node: Locale influences conversions,
Prev: Strings And Number
........................................
Where you are can matter when it comes to converting between numbers and
-strings. The local character set and languageâthe âlocaleââcan affect
+strings. The local character set and language--the âlocaleâ--can affect
numeric formats. In particular, for âawkâ programs, it affects the
decimal point character and the thousands-separator character. The
â"C"â locale, and most English-language locales, use the period
-character (â.â) as the decimal point and donât have a thousands
+character (â.â) as the decimal point and don't have a thousands
separator. However, many (if not most) European and non-English locales
use the comma (â,â) as the decimal point character. European locales
often use either a space or a period as the thousands separator, if they
@@ -8824,7 +8815,7 @@ difference in behavior, on a GNU/Linux system:
The âen_DK.utf-8â locale is for English in Denmark, where the comma acts
as the decimal point separator. In the normal â"C"â locale, âgawkâ
-treats â4,321â as 4, while in the Danish locale, itâs treated as the
+treats â4,321â as 4, while in the Danish locale, it's treated as the
full number including the fractional part, 4.321.
Some earlier versions of âgawkâ fully complied with this aspect of
@@ -8832,16 +8823,15 @@ the standard. However, many users in non-English
locales complained
about this behavior, because their data used a period as the decimal
point, so the default behavior was restored to use a period as the
decimal point character. You can use the â--use-lc-numericâ option
-(*note Options::) to force âgawkâ to use the localeâs decimal point
-character. (âgawkâ also uses the localeâs decimal point character when
+(*note Options::) to force âgawkâ to use the locale's decimal point
+character. (âgawkâ also uses the locale's decimal point character when
in POSIX mode, either via â--posixâ or the âPOSIXLY_CORRECTâ
environment
variable, as shown previously.)
*note Table 6.1: table-locale-affects. describes the cases in which
-the localeâs decimal point character is used and when a period is used.
+the locale's decimal point character is used and when a period is used.
Some of these features have not been described yet.
-
Feature Default â--posixâ or
â--use-lc-numericâ
------------------------------------------------------------
@@ -8885,7 +8875,7 @@ expressions. All of these arithmetic operators follow
normal precedence
rules and work as you would expect them to.
The following example uses a file named âgradesâ, which contains a
-list of student names as well as three test scores per student (itâs a
+list of student names as well as three test scores per student (it's a
small class):
Pat 100 97 58
@@ -8920,7 +8910,7 @@ order from the highest precedence to the lowest:
âX / Yâ
Division; because all numbers in âawkâ are floating-point numbers,
- the result is _not_ rounded to an integerââ3 / 4â has the value
+ the result is _not_ rounded to an integer--â3 / 4â has the value
0.75. (It is a common mistake, especially for C programmers, to
forget that _all_ numbers in âawkâ are floating point, and that
division of integer-looking constants produces a real number, not
@@ -8942,8 +8932,8 @@ have the same precedence.
When computing the remainder of âX % Yâ, the quotient is rounded
toward zero to an integer and multiplied by Y. This result is
-subtracted from X; this operation is sometimes known as âtrunc-mod.â The
-following relation always holds:
+subtracted from X; this operation is sometimes known as "trunc-mod."
+The following relation always holds:
b * int(a / b) + (a % b) == a
@@ -8970,7 +8960,7 @@ File: gawk.info, Node: Concatenation, Next: Assignment
Ops, Prev: Arithmetic
--------------------------
It seemed like a good idea at the time.
- â _Brian Kernighan_
+ -- _Brian Kernighan_
There is only one string operation: concatenation. It does not have
a specific operator to represent it. Instead, concatenation is
@@ -9025,16 +9015,16 @@ often counter-intuitive. Consider this example:
$ awk 'BEGIN { print -12 " " -24 }'
⣠-12-24
- This âobviouslyâ is concatenating â12, a space, and â24. But where
+ This "obviously" is concatenating â12, a space, and â24. But where
did the space disappear to? The answer lies in the combination of
-operator precedences and âawkââs automatic conversion rules. To get the
+operator precedences and âawkâ's automatic conversion rules. To get the
desired result, write the program this way:
$ awk 'BEGIN { print -12 " " (-24) }'
⣠-12 -24
This forces âawkâ to treat the â-â on the â-24â as unary.
Otherwise,
-itâs parsed as follows:
+it's parsed as follows:
â12 (â" "â â 24)
â â12 (0 â 24)
@@ -9042,11 +9032,11 @@ itâs parsed as follows:
â â12â24
As mentioned earlier, when mixing concatenation with other operators,
-_parenthesize_. Otherwise, youâre never quite sure what youâll get.
+_parenthesize_. Otherwise, you're never quite sure what you'll get.
---------- Footnotes ----------
- (1) It happens that BWK âawkâ, âgawkâ, and âmawkâ all âget it
right,â
+ (1) It happens that BWK âawkâ, âgawkâ, and âmawkâ all "get it
right,"
but you should not rely on this.
@@ -9056,7 +9046,7 @@ File: gawk.info, Node: Assignment Ops, Next: Increment
Ops, Prev: Concatenati
----------------------------
An âassignmentâ is an expression that stores a (usually different) value
-into a variable. For example, letâs assign the value one to the
+into a variable. For example, let's assign the value one to the
variable âzâ:
z = 1
@@ -9075,7 +9065,7 @@ This also illustrates string concatenation. The â=â
sign is called an
âassignment operatorâ. It is the simplest assignment operator because
the value of the righthand operand is stored unchanged. Most operators
(addition, concatenation, and so on) have no effect except to compute a
-value. If the value isnât used, thereâs no reason to use the operator.
+value. If the value isn't used, there's no reason to use the operator.
An assignment operator is different; it does produce a value, but even
if you ignore it, the assignment still makes itself felt through the
alteration of the variable. We call this a âside effectâ.
@@ -9089,7 +9079,7 @@ that the assignment stores in the specified variable,
field, or array
element. (Such values are called ârvaluesâ.)
It is important to note that variables do _not_ have permanent types.
-A variableâs type is simply the type of whatever value was last assigned
+A variable's type is simply the type of whatever value was last assigned
to it. In the following program fragment, the variable âfooâ has a
numeric value at first, and a string value later on:
@@ -9112,10 +9102,10 @@ zero. After executing the following code, the value of
âfooâ is five:
examples illustrate how âawkâ works, _not_ how you should write
your programs!
- An assignment is an expression, so it has a valueâthe same value that
-is assigned. Thus, âz = 1â is an expression with the value one. One
-consequence of this is that you can write multiple assignments together,
-such as:
+ An assignment is an expression, so it has a value--the same value
+that is assigned. Thus, âz = 1â is an expression with the value one.
+One consequence of this is that you can write multiple assignments
+together, such as:
x = y = z = 5
@@ -9161,7 +9151,7 @@ expression. For example:
The indices of âbarâ are practically guaranteed to be different, because
ârand()â returns different values each time it is called. (Arrays and
-the ârand()â function havenât been covered yet. *Note Arrays::, and
+the ârand()â function haven't been covered yet. *Note Arrays::, and
*note Numeric Functions:: for more information.) This example
illustrates an important fact about assignment operators: the lefthand
expression is only evaluated _once_.
@@ -9178,7 +9168,6 @@ The value of âa[3]â could be either two or four.
operators. In each case, the righthand operand is an expression whose
value is converted to a number.
-
Operator Effect
--------------------------------------------------------------------------
LVALUE â+=â Add INCREMENT to the value of LVALUE.
@@ -9229,11 +9218,11 @@ are convenient abbreviations for very common operations.
The operator used for adding one is written â++â. It can be used to
increment a variable either before or after taking its value. To
âpre-incrementâ a variable âvâ, write â++vâ. This adds one to the
value
-of âvââthat new value is also the value of the expression. (The
+of âvâ--that new value is also the value of the expression. (The
assignment expression âv += 1â is completely equivalent.) Writing the
â++â after the variable specifies âpost-incrementâ. This increments
the
variable value just the same; the difference is that the value of the
-increment expression itself is the variableâs _old_ value. Thus, if
+increment expression itself is the variable's _old_ value. Thus, if
âfooâ has the value four, then the expression âfoo++â has the value
four, but it changes the value of âfooâ to five. In other words, the
operator returns the old value of the variable, but with the side effect
@@ -9241,7 +9230,7 @@ of incrementing it.
The post-increment âfoo++â is nearly the same as writing â(foo += 1)
- 1â. It is not perfectly equivalent because all numbers in âawkâ are
-floating pointâin floating point, âfoo + 1 - 1â does not necessarily
+floating point--in floating point, âfoo + 1 - 1â does not necessarily
equal âfooâ. But the difference is minute as long as you stick to
numbers that are fairly small (less than 10e12).
@@ -9274,10 +9263,9 @@ a summary of increment and decrement expressions:
instead of adding, it subtracts.)
Operator Evaluation Order
-
Doctor, it hurts when I do this!
- Then donât do that!
- â _Groucho Marx_
+ Then don't do that!
+ -- _Groucho Marx_
What happens for something like the following?
@@ -9306,20 +9294,20 @@ File: gawk.info, Node: Truth Values and Conditions,
Next: Function Calls, Pre
6.3 Truth Values and Conditions
===============================
-In certain contexts, expression values also serve as âtruth valuesâ;
+In certain contexts, expression values also serve as "truth values";
i.e., they determine what should happen next as the program runs. This
-minor node describes how âawkâ defines âtrueâ and âfalseâ and how
values
+minor node describes how âawkâ defines "true" and "false" and how values
are compared.
* Menu:
-* Truth Values:: What is âtrueâ and what is âfalseâ.
+* Truth Values:: What is "true" and what is "false".
* Typing and Comparison:: How variables acquire types and how this
affects comparison of numbers and strings with
â<â, etc.
* Boolean Ops:: Combining comparison expressions using boolean
- operators â||â (âorâ), â&&â
- (âandâ) and â!â (ânotâ).
+ operators â||â ("or"), â&&â
+ ("and") and â!â ("not").
* Conditional Exp:: Conditional expressions select between two
subexpressions under control of a third
subexpression.
@@ -9331,7 +9319,7 @@ File: gawk.info, Node: Truth Values, Next: Typing and
Comparison, Up: Truth V
-----------------------------
Many programming languages have a special representation for the
-concepts of âtrueâ and âfalse.â Such languages usually use the special
+concepts of "true" and "false." Such languages usually use the special
constants âtrueâ and âfalseâ, or perhaps their uppercase equivalents.
However, âawkâ is different. It borrows a very simple concept of true
and false from C. In âawkâ, any nonzero numeric value _or_ any nonempty
@@ -9348,7 +9336,7 @@ times:
print "A strange truth value"
}
- There is a surprising consequence of the ânonzero or non-nullâ rule:
+ There is a surprising consequence of the "nonzero or non-null" rule:
the string constant â"0"â is actually true, because it is non-null.
(d.c.)
@@ -9359,7 +9347,7 @@ File: gawk.info, Node: Typing and Comparison, Next:
Boolean Ops, Prev: Truth
------------------------------------------------
The Guide is definitive. Reality is frequently inaccurate.
- â _Douglas Adams, âThe Hitchhikerâs Guide to the Galaxyâ_
+ -- _Douglas Adams, âThe Hitchhiker's Guide to the Galaxyâ_
Unlike in other programming languages, in âawkâ variables do not have
a fixed type. Instead, they can be either a number or a string,
@@ -9382,14 +9370,14 @@ Scalar objects in âawkâ (variables, array elements,
and fields) are
_dynamically_ typed. This means their type can change as the program
runs, from âuntypedâ before any use,(1) to string or number, and then
from string to number or number to string, as the program progresses.
-(âgawkâ also provides regexp-typed scalars, but letâs ignore that for
+(âgawkâ also provides regexp-typed scalars, but let's ignore that for
now; *note Strong Regexp Constants::.)
- You canât do much with untyped variables, other than tell that they
+ You can't do much with untyped variables, other than tell that they
are untyped. The following program tests âaâ against â""â and
â0â; the
test succeeds when âaâ has never been assigned a value. It also uses
the built-in âtypeof()â function (not presented yet; *note Type
-Functions::) to show âaââs type:
+Functions::) to show âaâ's type:
$ gawk 'BEGIN { print (a == "" && a == 0 ?
> "a is untyped" : "a has a type!") ; print typeof(a) }'
@@ -9413,7 +9401,7 @@ such as from a string constant, or from another scalar
with string type:
string
So far, this is all simple and straightforward. What happens,
-though, when âawkâ has to process data from a user? Letâs start with
+though, when âawkâ has to process data from a user? Let's start with
field data. What should the following command produce as output?
echo hello | awk '{ printf("%s %s < 42\n", $1,
@@ -9421,7 +9409,7 @@ field data. What should the following command produce as
output?
Since âhelloâ is alphabetic data, âawkâ can only do a string
comparison.
Internally, it converts â42â into â"42"â and compares the two string
-values â"hello"â and â"42"â. Hereâs the result:
+values â"hello"â and â"42"â. Here's the result:
$ echo hello | awk '{ printf("%s %s < 42\n", $1,
> ($1 < 42 ? "is" : "is not")) }'
@@ -9488,14 +9476,14 @@ NUMERIC | string numeric numeric
STRNUM | string numeric numeric
--------+----------------------------------------------
- The basic idea is that user input that looks numericâand _only_ user
-inputâshould be treated as numeric, even though it is actually made of
+ The basic idea is that user input that looks numeric--and _only_ user
+input--should be treated as numeric, even though it is actually made of
characters and is therefore also a string. Thus, for example, the
string constant â" +3.14"â, when it appears in program source code, is a
-stringâeven though it looks numericâand is _never_ treated as a number
+string--even though it looks numeric--and is _never_ treated as a number
for comparison purposes.
- In short, when one operand is a âpureâ string, such as a string
+ In short, when one operand is a "pure" string, such as a string
constant, then a string comparison is performed. Otherwise, a numeric
comparison is performed. (The primary difference between a number and a
strnum is that for strnums âgawkâ preserves the original string value
@@ -9537,7 +9525,7 @@ program text comprise a string constant. The following
examples print
(1) âgawkâ calls this âunassignedâ, as the following example shows.
- (2) Thus, a POSIX numeric string and âgawkââs strnum are the same
+ (2) Thus, a POSIX numeric string and âgawkâ's strnum are the same
thing.
@@ -9551,7 +9539,6 @@ such as equality. They are written using ârelational
operatorsâ, which
are a superset of those in C. *note Table 6.3: table-relational-ops.
describes them.
-
Expression Result
--------------------------------------------------------------------------
X â<â Y True if X is less than Y
@@ -9621,10 +9608,10 @@ comparison is:
⣠false
the result is âfalseâ because both â$1â and â$2â are user input.
They
-are numeric stringsâtherefore both have the strnum attribute, dictating
+are numeric strings--therefore both have the strnum attribute, dictating
a numeric comparison. The purpose of the comparison rules and the use
-of numeric strings is to attempt to produce the behavior that is âleast
-surprising,â while still âdoing the right thing.â
+of numeric strings is to attempt to produce the behavior that is "least
+surprising," while still "doing the right thing."
String comparisons and regular expression comparisons are very
different. For example:
@@ -9661,7 +9648,7 @@ File: gawk.info, Node: POSIX String Comparison, Prev:
Comparison Operators, U
.........................................................
The POSIX standard used to say that all string comparisons are performed
-based on the localeâs âcollating orderâ. This is the order in which
+based on the locale's âcollating orderâ. This is the order in which
characters sort, as defined by the locale (for more discussion, *note
Locales::). This order is usually very different from the results
obtained when doing straight byte-by-byte comparison.(1)
@@ -9706,8 +9693,8 @@ File: gawk.info, Node: Boolean Ops, Next: Conditional
Exp, Prev: Typing and C
-------------------------
A âBoolean expressionâ is a combination of comparison expressions or
-matching expressions, using the Boolean operators âorâ (â||â),
âandâ
-(â&&â), and ânotâ (â!â), along with parentheses to control
nesting. The
+matching expressions, using the Boolean operators "or" (â||â), "and"
+(â&&â), and "not" (â!â), along with parentheses to control nesting.
The
truth value of the Boolean expression is computed by combining the truth
values of the component expressions. Boolean expressions are also
referred to as âlogical expressionsâ. The terms are equivalent.
@@ -9745,7 +9732,7 @@ operators are:
The subexpression BOOLEAN2 is evaluated only if BOOLEAN1 is false.
This can make a difference when BOOLEAN2 contains expressions that
have side effects. (Thus, this test never really distinguishes
- records that contain both âeduâ and âliââas soon as âeduâ is
+ records that contain both âeduâ and âliâ--as soon as âeduâ is
matched, the full test succeeds.)
â! BOOLEANâ
@@ -9760,7 +9747,7 @@ operators are:
The â&&â and â||â operators are called âshort-circuitâ operators
because of the way they work. Evaluation of the full expression is
-âshort-circuitedâ if the result can be determined partway through its
+"short-circuited" if the result can be determined partway through its
evaluation.
Statements that end with â&&â or â||â can be continued simply by
@@ -9797,7 +9784,7 @@ in the negative:
NOTE: The ânextâ statement is discussed in *note Next Statement::.
ânextâ tells âawkâ to skip the rest of the rules, get the next
record, and start processing the rules over again at the top. The
- reason itâs there is to avoid printing the bracketing âSTARTâ and
+ reason it's there is to avoid printing the bracketing âSTARTâ and
âENDâ lines.
---------- Footnotes ----------
@@ -9812,14 +9799,14 @@ File: gawk.info, Node: Conditional Exp, Prev: Boolean
Ops, Up: Truth Values a
-----------------------------
A âconditional expressionâ is a special kind of expression that has
-three operands. It allows you to use one expressionâs value to select
+three operands. It allows you to use one expression's value to select
one of two other expressions. The conditional expression in âawkâ is
the same as in the C language, as shown here:
SELECTOR ? IF-TRUE-EXP : IF-FALSE-EXP
There are three subexpressions. The first, SELECTOR, is always computed
-first. If it is âtrueâ (not zero or not null), then IF-TRUE-EXP is
+first. If it is "true" (not zero or not null), then IF-TRUE-EXP is
computed next, and its value becomes the value of the whole expression.
Otherwise, IF-FALSE-EXP is computed next, and its value becomes the
value of the whole expression. For example, the following expression
@@ -9866,7 +9853,7 @@ from your program (*note Dynamic Extensions::).
The way to use a function is with a âfunction callâ expression, which
consists of the function name followed immediately by a list of
âargumentsâ in parentheses. The arguments are expressions that provide
-the raw materials for the functionâs calculations. When there is more
+the raw materials for the function's calculations. When there is more
than one argument, they are separated by commas. If there are no
arguments, just write â()â after the function name. The following
examples show function calls with and without arguments:
@@ -9877,7 +9864,7 @@ examples show function calls with and without arguments:
CAUTION: Do not put any space between the function name and the
opening parenthesis! A user-defined function name looks just like
- the name of a variableâa space would make the expression look like
+ the name of a variable--a space would make the expression look like
concatenation of a variable with an expression inside parentheses.
With built-in functions, space before the parenthesis is harmless,
but it is best not to get into the habit of using space to avoid
@@ -9976,7 +9963,7 @@ rules; for example, â$$0++--â is not a valid
expression because the
first â$â has higher precedence than the â++â; to avoid the problem the
expression can be rewritten as â$($0++)--â.
- This list presents âawkââs operators, in order of highest to lowest
+ This list presents âawkâ's operators, in order of highest to lowest
precedence:
â(â...â)â
@@ -9992,7 +9979,7 @@ precedence:
Exponentiation. These operators group right to left.
â+ - !â
- Unary plus, minus, logical ânot.â
+ Unary plus, minus, logical "not."
â* / %â
Multiplication, division, remainder.
@@ -10026,10 +10013,10 @@ String concatenation
Array membership.
â&&â
- Logical âand.â
+ Logical "and."
â||â
- Logical âor.â
+ Logical "or."
â?:â
Conditional. This operator groups right to left.
@@ -10063,8 +10050,8 @@ terminator.
Locales can affect how dates and times are formatted (*note Time
Functions::). For example, a common way to abbreviate the date
-September 4, 2015, in the United States is â9/4/15.â In many countries
-in Europe, however, it is abbreviated â4.9.15.â Thus, the â%xâ
+September 4, 2015, in the United States is "9/4/15." In many countries
+in Europe, however, it is abbreviated "4.9.15." Thus, the â%xâ
specification in a â"US"â locale might produce â9/4/15â, while in a
â"EUROPE"â locale, it might produce â4.9.15â.
@@ -10107,7 +10094,7 @@ File: gawk.info, Node: Expressions Summary, Prev:
Locales, Up: Expressions
an array membership testing operator, and regexp matching
operators. String concatenation is accomplished by placing two
expressions next to each other; there is no explicit operator. The
- three-operand â?:â operator provides an âif-elseâ test within
+ three-operand â?:â operator provides an "if-else" test within
expressions.
⢠Assignment operators provide convenient shorthands for common
@@ -10116,7 +10103,7 @@ File: gawk.info, Node: Expressions Summary, Prev:
Locales, Up: Expressions
⢠In âawkâ, a value is considered to be true if it is nonzero _or_
non-null. Otherwise, the value is false.
- ⢠A variableâs type is set upon each assignment and may change over
+ ⢠A variable's type is set upon each assignment and may change over
its lifetime. The type determines how it behaves in comparisons
(string or numeric).
@@ -10126,7 +10113,7 @@ File: gawk.info, Node: Expressions Summary, Prev:
Locales, Up: Expressions
and user-defined functions; this is described in *note Functions::.
⢠Operator precedence specifies the order in which operations are
- performed, unless explicitly overridden by parentheses. âawkââs
+ performed, unless explicitly overridden by parentheses. âawkâ's
operator precedence is compatible with that of C.
⢠Locales can affect the format of data as output by an âawkâ
@@ -10141,12 +10128,12 @@ File: gawk.info, Node: Patterns and Actions, Next:
Arrays, Prev: Expressions,
As you have already seen, each âawkâ statement consists of a pattern
with an associated action. This major node describes how you build
patterns and actions, what kinds of things you can do within actions,
-and âawkââs predefined variables.
+and âawkâ's predefined variables.
- The patternâaction rules and the statements available for use within
+ The pattern-action rules and the statements available for use within
actions form the core of âawkâ programming. In a sense, everything
covered up to here has been the foundation that programs are built on
-top of. Now itâs time to start building something useful.
+top of. Now it's time to start building something useful.
* Menu:
@@ -10173,8 +10160,8 @@ File: gawk.info, Node: Pattern Overview, Next: Using
Shell Variables, Up: Pat
* BEGINFILE/ENDFILE:: Two special patterns for advanced control.
* Empty:: The empty pattern, which matches every record.
-Patterns in âawkâ control the execution of rulesâa rule is executed when
-its pattern matches the current input record. The following is a
+Patterns in âawkâ control the execution of rules--a rule is executed
+when its pattern matches the current input record. The following is a
summary of the types of âawkâ patterns:
â/REGULAR EXPRESSION/â
@@ -10224,10 +10211,10 @@ File: gawk.info, Node: Expression Patterns, Next:
Ranges, Prev: Regexp Patter
-----------------------------
Any âawkâ expression is valid as an âawkâ pattern. The pattern matches
-if the expressionâs value is nonzero (if a number) or non-null (if a
+if the expression's value is nonzero (if a number) or non-null (if a
string). The expression is reevaluated each time the rule is tested
against a new input record. If the expression uses fields such as â$1â,
-the value depends directly on the new input recordâs text; otherwise, it
+the value depends directly on the new input record's text; otherwise, it
depends on only what has happened so far in the execution of the âawkâ
program.
@@ -10323,8 +10310,8 @@ following record. Then the range pattern goes back to
checking BEGPAT
against each record.
The record that turns on the range pattern and the one that turns it
-off both match the range pattern. If you donât want to operate on these
-records, you can write âifâ statements in the ruleâs action to
+off both match the range pattern. If you don't want to operate on these
+records, you can write âifâ statements in the rule's action to
distinguish them from the records you are interested in.
It is possible for a pattern to be turned on and off by the same
@@ -10375,7 +10362,7 @@ All the patterns described so far are for matching
input records. The
and cleanup actions for âawkâ programs. âBEGINâ and âENDâ rules
must
have actions; there is no default action for these rules because there
is no current record when they run. âBEGINâ and âENDâ rules are often
-referred to as ââBEGINâ and âENDâ blocksâ by longtime âawkâ
programmers.
+referred to as "âBEGINâ and âENDâ blocks" by longtime âawkâ
programmers.
* Menu:
@@ -10427,7 +10414,7 @@ functions, because each library file can have its own
âBEGINâ and/or
which library functions are named on the command line controls the order
in which their âBEGINâ and âENDâ rules are executed. Therefore, you
have to be careful when writing such rules in library files so that the
-order in which they are executed doesnât matter. *Note Options:: for
+order in which they are executed doesn't matter. *Note Options:: for
more information on using library functions. *Note Library Functions::,
for a number of useful library functions.
@@ -10494,7 +10481,7 @@ File: gawk.info, Node: BEGINFILE/ENDFILE, Next:
Empty, Prev: BEGIN/END, Up:
This minor node describes a âgawkâ-specific feature.
Two special kinds of rule, âBEGINFILEâ and âENDFILEâ, give you
-âhooksâ into âgawkââs command-line file processing loop. As with the
+"hooks" into âgawkâ's command-line file processing loop. As with the
âBEGINâ and âENDâ rules (*note BEGIN/END::), âBEGINFILEâ rules in a
program execute in the order they are read by âgawkâ. Similarly, all
âENDFILEâ rules also execute in the order they are read.
@@ -10524,7 +10511,7 @@ tasks that would otherwise be difficult or impossible
to perform:
entirely. Otherwise, âgawkâ exits with the usual fatal error.
⢠If you have written extensions that modify the record handling (by
- inserting an âinput parserâ; *note Input Parsers::), you can invoke
+ inserting an "input parser"; *note Input Parsers::), you can invoke
them at this point, before âgawkâ has started processing the file.
(This is a _very_ advanced feature, currently used only by the
âgawkextlibâ project
@@ -10578,7 +10565,7 @@ hold a pattern that the âawkâ program searches for.
There are two ways
to get the value of the shell variable into the body of the âawkâ
program.
- A common method is to use shell quoting to substitute the variableâs
+ A common method is to use shell quoting to substitute the variable's
value into the program inside the script. For example, consider the
following program:
@@ -10593,12 +10580,12 @@ double-quoted, which allows substitution of the
âpatternâ shell variable
inside the quotes. The second part is single-quoted.
Variable substitution via quoting works, but can potentially be
-messy. It requires a good understanding of the shellâs quoting rules
-(*note Quoting::), and itâs often difficult to correctly match up the
+messy. It requires a good understanding of the shell's quoting rules
+(*note Quoting::), and it's often difficult to correctly match up the
quotes when reading the program.
- A better method is to use âawkââs variable assignment feature (*note
-Assignment Options::) to assign the shell variableâs value to an âawkâ
+ A better method is to use âawkâ's variable assignment feature (*note
+Assignment Options::) to assign the shell variable's value to an âawkâ
variable. Then use dynamic regexps to match the pattern (*note Computed
Regexps::). The following shows how to redo the previous example using
this technique:
@@ -10613,9 +10600,9 @@ Now, the âawkâ program is just one single-quoted
string. The assignment
whitespace in the value of â$patternâ. The âawkâ variable âpatâ
could
be named âpatternâ too, but that would be more confusing. Using a
variable also provides more flexibility, as the variable can be used
-anywhere inside the programâfor printing, as an array subscript, or for
-any other useâwithout requiring the quoting tricks at every point in the
-program.
+anywhere inside the program--for printing, as an array subscript, or for
+any other use--without requiring the quoting tricks at every point in
+the program.
File: gawk.info, Node: Action Overview, Next: Statements, Prev: Using Shell
Variables, Up: Patterns and Actions
@@ -10683,7 +10670,7 @@ File: gawk.info, Node: Statements, Next: Built-in
Variables, Prev: Action Ove
=================================
âControl statementsâ, such as âifâ, âwhileâ, and so on, control
the flow
-of execution in âawkâ programs. Most of âawkââs control statements
are
+of execution in âawkâ programs. Most of âawkâ's control statements are
patterned after similar statements in C.
All the control statements start with special keywords, such as âifâ
@@ -10718,7 +10705,7 @@ File: gawk.info, Node: If Statement, Next: While
Statement, Up: Statements
7.4.1 The âifâ-âelseâ Statement
-------------------------------
-The âifâ-âelseâ statement is âawkââs decision-making statement.
It
+The âifâ-âelseâ statement is âawkâ's decision-making statement. It
looks like this:
âif (CONDITION) THEN-BODYâ [âelse ELSE-BODYâ]
@@ -10745,8 +10732,8 @@ illustrate this, the previous example can be rewritten
as:
if (x % 2 == 0) print "x is even"; else
print "x is odd"
-If the â;â is left out, âawkâ canât interpret the statement and it
-produces a syntax error. Donât actually write programs this way,
+If the â;â is left out, âawkâ can't interpret the statement and it
+produces a syntax error. Don't actually write programs this way,
because a human reader might fail to see the âelseâ if it is not the
first thing on its line.
@@ -10830,7 +10817,7 @@ false to begin with. The following is an example of a
âdoâ statement:
} while (i <= 10)
}
-This program prints each input record 10 times. However, it isnât a
+This program prints each input record 10 times. However, it isn't a
very realistic example, because in this case an ordinary âwhileâ would
do just as well. This situation reflects actual experience; only
occasionally is there a real use for a âdoâ statement.
@@ -10877,7 +10864,7 @@ are workarounds, but they are nonobvious and can lead
to code that is
difficult to read and understand. It is best, therefore, to simply
write additional initializations as separate statements preceding the
âforâ loop and to place additional increment statements at the end of
-the loopâs body.
+the loop's body.
Most often, INCREMENT is an increment expression, as in the earlier
example. But this is not required; it can be any expression whatsoever.
@@ -10937,7 +10924,7 @@ checked for a match in the order they are defined. If
no suitable
âcaseâ is found, the âdefaultâ section is executed, if supplied.
Each âcaseâ contains a single constant, be it numeric, string, or
-regexp. The âswitchâ expression is evaluated, and then each âcaseââs
+regexp. The âswitchâ expression is evaluated, and then each âcaseâ's
constant is compared against the result in turn. The type of constant
determines the comparison: numeric or string do the usual comparisons.
A regexp constant (either regular, â/foo/â, or strongly typed,
â@/foo/â)
@@ -11070,10 +11057,10 @@ illustrates this fact:
print ""
}
-This program prints all the numbers from 0 to 20âexcept for 5, for which
-the âprintfâ is skipped. Because the increment âx++â is not skipped,
-âxâ does not remain stuck at 5. Contrast the âforâ loop from the
-previous example with the following âwhileâ loop:
+This program prints all the numbers from 0 to 20--except for 5, for
+which the âprintfâ is skipped. Because the increment âx++â is not
+skipped, âxâ does not remain stuck at 5. Contrast the âforâ loop from
+the previous example with the following âwhileâ loop:
BEGIN {
x = 0
@@ -11106,7 +11093,7 @@ File: gawk.info, Node: Next Statement, Next: Nextfile
Statement, Prev: Contin
The ânextâ statement forces âawkâ to immediately stop processing the
current record and go on to the next record. This means that no further
rules are executed for the current record, and the rest of the current
-ruleâs action isnât executed.
+rule's action isn't executed.
Contrast this with the effect of the âgetlineâ function (*note
Getline::). That also causes âawkâ to read the next record immediately,
@@ -11114,15 +11101,15 @@ but it does not alter the flow of control in any way
(i.e., the rest of
the current action executes with a new input record).
At the highest level, âawkâ program execution is a loop that reads an
-input record and then tests each ruleâs pattern against it. If you
+input record and then tests each rule's pattern against it. If you
think of this loop as a âforâ statement whose body contains the rules,
then the ânextâ statement is analogous to a âcontinueâ statement. It
skips to the end of the body of this implicit loop and executes the
increment (which reads another record).
For example, suppose an âawkâ program works only on records with four
-fields, and it shouldnât fail when given bad input. To avoid
-complicating the rest of the program, write a âweed outâ rule near the
+fields, and it shouldn't fail when given bad input. To avoid
+complicating the rest of the program, write a "weed out" rule near the
beginning, in the following manner:
NF != 4 {
@@ -11130,7 +11117,7 @@ beginning, in the following manner:
next
}
-Because of the ânextâ statement, the programâs subsequent rules wonât
+Because of the ânextâ statement, the program's subsequent rules won't
see the bad record. The error message is redirected to the standard
error output stream, as error messages should be. For more detail, see
*note Special Files::.
@@ -11144,7 +11131,7 @@ rules. *Note BEGINFILE/ENDFILE::.
According to the POSIX standard, the behavior is undefined if the
ânextâ statement is used in a âBEGINâ or âENDâ rule. âgawkâ
treats it
as a syntax error. Although POSIX does not disallow it, most other
-âawkâ implementations donât allow the ânextâ statement inside
function
+âawkâ implementations don't allow the ânextâ statement inside function
bodies (*note User-defined::). Just as with any other ânextâ statement,
a ânextâ statement inside a function body reads the next record and
starts processing it with the first rule in the program.
@@ -11169,7 +11156,7 @@ an âENDâ rule; in this case, it causes the program
to stop immediately.
*Note BEGIN/END::.
The ânextfileâ statement is useful when there are many data files to
-process but it isnât necessary to process every record in every file.
+process but it isn't necessary to process every record in every file.
Without ânextfileâ, in order to move on to the next data file, a program
would have to continue scanning the unwanted records. The ânextfileâ
statement accomplishes this much more efficiently.
@@ -11177,7 +11164,7 @@ statement accomplishes this much more efficiently.
In âgawkâ, execution of ânextfileâ causes additional things to
happen: any âENDFILEâ rules are executed if âgawkâ is not currently in
an âENDâ rule, âARGINDâ is incremented, and any âBEGINFILEâ rules
are
-executed. (âARGINDâ hasnât been introduced yet. *Note Built-in
+executed. (âARGINDâ hasn't been introduced yet. *Note Built-in
Variables::.)
There is an additional, special, use case with âgawkâ. ânextfileâ
is
@@ -11186,7 +11173,7 @@ otherwise cause âgawkâ to exit with a fatal error.
In this special
case, âENDFILEâ rules are not executed. *Note BEGINFILE/ENDFILE::.
Although it might seem that âclose(FILENAME)â would accomplish the
-same as ânextfileâ, this isnât true. âclose()â is reserved for
closing
+same as ânextfileâ, this isn't true. âclose()â is reserved for closing
files, pipes, and coprocesses that are opened with redirections. It is
not related to the main processing that âawkâ does with the files listed
in âARGVâ.
@@ -11197,7 +11184,7 @@ in âARGVâ.
(http://austingroupbugs.net/view.php?id=607).
The current version of BWK âawkâ and âmawkâ also support
ânextfileâ.
-However, they donât allow the ânextfileâ statement inside function
+However, they don't allow the ânextfileâ statement inside function
bodies (*note User-defined::). âgawkâ does; a ânextfileâ inside a
function body reads the first record from the next file and starts
processing it with the first rule in the program, just as any other
@@ -11228,14 +11215,14 @@ skips reading any remaining input records, and
executes the âENDâ rule
if there is one. âgawkâ also skips any âENDFILEâ rules; they do not
execute.
- In such a case, if you donât want the âENDâ rule to do its job, set a
+ In such a case, if you don't want the âENDâ rule to do its job, set a
variable to a nonzero value before the âexitâ statement and check that
variable in the âENDâ rule. *Note Assert Function:: for an example that
does this.
If an argument is supplied to âexitâ, its value is used as the exit
status code for the âawkâ process. If no argument is supplied, âexitâ
-causes âawkâ to return a âsuccessâ status. In the case where an
+causes âawkâ to return a "success" status. In the case where an
argument is supplied to a first âexitâ statement, and then âexitâ is
called a second time from an âENDâ rule with no argument, âawkâ uses
the
previously supplied exit value. (d.c.) *Note Exit Status:: for more
@@ -11273,7 +11260,7 @@ of these automatically, so that they enable you to tell
âawkâ how to do
certain things. Others are set automatically by âawkâ, so that they
carry information from the internal workings of âawkâ to your program.
- This minor node documents all of âgawkââs predefined variables, most
+ This minor node documents all of âgawkâ's predefined variables, most
of which are also documented in the major nodes describing their areas
of activity.
@@ -11389,7 +11376,7 @@ each variable.)
changing âLINTâ does affect the production of lint warnings, even
if âgawkâ is in compatibility mode. Much as the â--lintâ and
â--traditionalâ options independently control different aspects of
- âgawkââs behavior, the control of lint warnings during program
+ âgawkâ's behavior, the control of lint warnings during program
execution is independent of the flavor of âawkâ being executed.
âOFMTâ
@@ -11431,7 +11418,7 @@ each variable.)
The ability for âRSâ to be a regular expression is a âgawkâ
extension. In most other âawkâ implementations, or if âgawkâ is
in
compatibility mode (*note Options::), just the first character of
- âRSââs value is used.
+ âRSâ's value is used.
âSUBSEPâ
The subscript separator. It has the default value of â"\034"â and
@@ -11483,12 +11470,12 @@ they are not special:
elements are numbered from zero.
The names âARGCâ and âARGVâ, as well as the convention of indexing
- the array from 0 to âARGCâ â 1, are derived from the C languageâs
+ the array from 0 to âARGCâ â 1, are derived from the C language's
method of accessing command-line arguments.
The value of âARGV[0]â can vary from system to system. Also, you
should note that the program text is _not_ included in âARGVâ, nor
- are any of âawkââs command-line options. *Note ARGC and ARGV:: for
+ are any of âawkâ's command-line options. *Note ARGC and ARGV:: for
information about how âawkâ uses these variables. (d.c.)
âARGIND #â
@@ -11576,7 +11563,7 @@ they are not special:
â$0â changes (*note Fields::).
Unlike most of the variables described in this node, assigning a
- value to âNFâ has the potential to affect âawkââs internal
+ value to âNFâ has the potential to affect âawkâ's internal
workings. In particular, assignments to âNFâ can be used to create
fields in or remove fields from the current record. *Note Changing
Fields::.
@@ -11592,7 +11579,7 @@ they are not special:
âNRâ
The number of input records âawkâ has processed since the beginning
- of the programâs execution (*note Records::). âawkâ increments
+ of the program's execution (*note Records::). âawkâ increments
âNRâ each time it reads a new record.
âPROCINFO #â
@@ -11661,7 +11648,7 @@ they are not special:
â"untyped"â
The identifier is untyped (could be used as a scalar or
- an array; âgawkâ doesnât know yet).
+ an array; âgawkâ doesn't know yet).
â"user"â
The identifier is a user-defined function.
@@ -11744,7 +11731,7 @@ they are not special:
groups that the process has. Use the âinâ operator to test for
these elements (*note Reference to Elements::).
- The following elements allow you to change âgawkââs behavior:
+ The following elements allow you to change âgawkâ's behavior:
âPROCINFO["BUFFERPIPE"]â
If this element exists, all output to pipelines becomes
@@ -11808,7 +11795,7 @@ they are not special:
âSYMTAB #â
An array whose indices are the names of all defined global
- variables and arrays in the program. âSYMTABâ makes âgawkââs
+ variables and arrays in the program. âSYMTABâ makes âgawkâ's
symbol table visible to the âawkâ programmer. It is built as
âgawkâ parses the program and is complete before the program starts
to run.
@@ -11862,7 +11849,6 @@ they are not special:
within the âSYMTABâ array.
Changing âNRâ and âFNRâ
-
âawkâ increments âNRâ and âFNRâ each time it reads a record,
instead
of setting them to the absolute value of the number of records read.
This means that a program can change these variables and their new
@@ -11946,7 +11932,7 @@ program can treat the eliminated arguments as something
other than file
names.
To eliminate a file from the middle of the list, store the null
-string (â""â) into âARGVâ in place of the fileâs name. As a special
+string (â""â) into âARGVâ in place of the file's name. As a special
feature, âawkâ ignores file names that have been replaced with the null
string. Another option is to use the âdeleteâ statement to remove
elements from âARGVâ (*note Delete::).
@@ -11956,7 +11942,7 @@ actual processing of the input begins. *Note Split
Program:: and *note
Tee Program:: for examples of each way of removing elements from âARGVâ.
To actually get options into an âawkâ program, end the âawkâ options
-with â--â and then supply the âawkâ programâs options, in the
following
+with â--â and then supply the âawkâ program's options, in the following
manner:
awk -f myprog.awk -- -v -q file1 file2 ...
@@ -11980,7 +11966,7 @@ remove, the previously mentioned command-line options:
}
}
- Ending the âawkâ options with â--â isnât necessary in âgawkâ.
Unless
+ Ending the âawkâ options with â--â isn't necessary in âgawkâ.
Unless
â--posixâ has been specified, âgawkâ silently puts any unrecognized
options into âARGVâ for the âawkâ program to deal with. As soon as it
sees an unknown option, âgawkâ stops looking for other options that it
@@ -11993,8 +11979,8 @@ Because â-qâ is not a valid âgawkâ option, it
and the following â-vâ
passed on to the âawkâ program. (*Note Getopt Function:: for an âawkâ
library function that parses command-line options.)
- When designing your program, you should choose options that donât
-conflict with âgawkââs, because it will process any options that it
+ When designing your program, you should choose options that don't
+conflict with âgawkâ's, because it will process any options that it
accepts before passing the rest of the command line on to your program.
Using â#!â with the â-Eâ option may help (*note Executable Scripts::
and
*note Options::).
@@ -12005,7 +11991,7 @@ File: gawk.info, Node: Pattern Action Summary, Prev:
Built-in Variables, Up:
7.6 Summary
===========
- ⢠Patternâaction pairs make up the basic elements of an âawkâ
+ ⢠Pattern-action pairs make up the basic elements of an âawkâ
program. Patterns are either normal expressions, range
expressions, or regexp constants; one of the special keywords
âBEGINâ, âENDâ, âBEGINFILEâ, or âENDFILEâ; or empty. The
action
@@ -12014,7 +12000,7 @@ File: gawk.info, Node: Pattern Action Summary, Prev:
Built-in Variables, Up:
⢠I/O from âBEGINâ and âENDâ rules has certain constraints. This
is
also true, only more so, for âBEGINFILEâ and âENDFILEâ rules. The
- latter two give you âhooksâ into âgawkââs file processing,
allowing
+ latter two give you "hooks" into âgawkâ's file processing, allowing
you to recover from a file that otherwise would cause a fatal error
(such as a file that cannot be opened).
@@ -12041,7 +12027,7 @@ File: gawk.info, Node: Pattern Action Summary, Prev:
Built-in Variables, Up:
⢠The âexitâ statement terminates your program. When executed from
an action (or function body), it transfers control to the âENDâ
statements. From an âENDâ statement body, it exits immediately.
- You may pass an optional numeric value to be used as âawkââs exit
+ You may pass an optional numeric value to be used as âawkâ's exit
status.
⢠Some predefined variables provide control over âawkâ, mainly for
@@ -12065,8 +12051,8 @@ numbers or strings.
elements, how to scan through every element in an array, and how to
remove array elements. It also describes how âawkâ simulates
multidimensional arrays, as well as some of the less obvious points
-about array usage. The major node moves on to discuss âgawkââs facility
-for sorting arrays, and ends with a brief description of âgawkââs
+about array usage. The major node moves on to discuss âgawkâ's facility
+for sorting arrays, and ends with a brief description of âgawkâ's
ability to support true arrays of arrays.
* Menu:
@@ -12098,7 +12084,7 @@ at a time, and traversing all of the elements in an
array.
* Assigning Elements:: How to change an element of an array.
* Array Example:: Basic Example of an Array
* Scanning an Array:: A variation of the âforâ statement. It
- loops through the indices of an arrayâs
+ loops through the indices of an array's
existing elements.
* Controlling Scanning:: Controlling the order in which arrays are
scanned.
@@ -12111,7 +12097,7 @@ File: gawk.info, Node: Array Intro, Next: Reference
to Elements, Up: Array Ba
Doing linear scans over an associative array is like trying to club
someone to death with a loaded Uzi.
- â _Larry Wall_
+ -- _Larry Wall_
The âawkâ language provides one-dimensional arrays for storing groups
of related strings or numbers. Every âawkâ array must have a name.
@@ -12120,7 +12106,7 @@ name would also be a valid array name. But one name
cannot be used in
both ways (as an array and as a variable) in the same âawkâ program.
Arrays in âawkâ superficially resemble arrays in other programming
-languages, but there are fundamental differences. In âawkâ, it isnât
+languages, but there are fundamental differences. In âawkâ, it isn't
necessary to specify the size of an array before starting to use it.
Additionally, any number or string, not just consecutive integers, may
be used as an array index.
@@ -12135,15 +12121,14 @@ the beginning of the block of memory. Index one
specifies the second
element, which is stored in memory right after the first element, and so
on. It is impossible to add more elements to the array, because it has
room only for as many elements as given in the declaration. (Some
-languages allow arbitrary starting and ending indicesâe.g., â15 ..
-27ââbut the size of the array is still fixed when the array is
+languages allow arbitrary starting and ending indices--e.g., â15 ..
+27â--but the size of the array is still fixed when the array is
declared.)
A contiguous array of four elements might look like *note Figure 8.1:
figure-array-elements, conceptually, if the element values are eight,
â"foo"â, â""â, and 30.
-
[image src="gawk_array-elements.png" alt="A Contiguous Array"
text="+---------+---------+--------+---------+
| 8 | \"foo\" | \"\" | 30 | Value
+---------+---------+--------+---------+
@@ -12155,8 +12140,8 @@ Only the values are stored; the indices are implicit
from the order of
the values. Here, eight is the value at index zero, because eight
appears in the position with zero elements before it.
- Arrays in âawkâ are differentâthey are âassociativeâ. This means
-that each array is a collection of pairsâan index and its corresponding
+ Arrays in âawkâ are different--they are âassociativeâ. This means
+that each array is a collection of pairs--an index and its corresponding
array element value:
Index Value
@@ -12183,10 +12168,10 @@ whose value is â"number ten"â. The result is:
â2â â""â
Now the array is âsparseâ, which just means some indices are missing.
-It has elements 0â3 and 10, but doesnât have elements 4, 5, 6, 7, 8, or
+It has elements 0-3 and 10, but doesn't have elements 4, 5, 6, 7, 8, or
9.
- Another consequence of associative arrays is that the indices donât
+ Another consequence of associative arrays is that the indices don't
have to be nonnegative integers. Any number, or even a string, can be
an index. For example, the following is an array that translates words
from English to French:
@@ -12199,20 +12184,20 @@ from English to French:
â1â â"un"â
Here we decided to translate the number one in both spelled-out and
-numeric formâthus illustrating that a single array can have both numbers
-and strings as indices. (In fact, array subscripts are always strings.
-There are some subtleties to how numbers work when used as array
-subscripts; this is discussed in more detail in *note Numeric Array
-Subscripts::.) Here, the number â1â isnât double-quoted, because
âawkâ
-automatically converts it to a string.
+numeric form--thus illustrating that a single array can have both
+numbers and strings as indices. (In fact, array subscripts are always
+strings. There are some subtleties to how numbers work when used as
+array subscripts; this is discussed in more detail in *note Numeric
+Array Subscripts::.) Here, the number â1â isn't double-quoted, because
+âawkâ automatically converts it to a string.
The value of âIGNORECASEâ has no effect upon array subscripting. The
identical string value used to store an array element must be used to
retrieve it. When âawkâ creates an array (e.g., with the âsplit()â
-built-in function), that arrayâs indices are consecutive integers
+built-in function), that array's indices are consecutive integers
starting at one. (*Note String Functions::.)
- âawkââs arrays are efficientâthe time to access an element is
+ âawkâ's arrays are efficient--the time to access an element is
independent of the number of elements in the array.
---------- Footnotes ----------
@@ -12255,7 +12240,7 @@ been assigned any value as well as elements that have
been deleted
if (a["foo"] != "") ...
This is incorrect for two reasons. First, it _creates_ âa["foo"]â
- if it didnât exist before! Second, it is valid (if a bit unusual)
+ if it didn't exist before! Second, it is valid (if a bit unusual)
to set an array element equal to the empty string.
To determine whether an element exists in an array at a certain
@@ -12303,11 +12288,11 @@ File: gawk.info, Node: Array Example, Next:
Scanning an Array, Prev: Assignin
The following program takes a list of lines, each beginning with a line
number, and prints them out in order of line number. The line numbers
-are not in order when they are first readâinstead, they are scrambled.
+are not in order when they are first read--instead, they are scrambled.
This program sorts the lines by making an array using the line numbers
as subscripts. The program then prints out the lines in sorted order of
their numbers. It is a very simple program and gets confused upon
-encountering repeated numbers, gaps, or lines that donât begin with a
+encountering repeated numbers, gaps, or lines that don't begin with a
number:
{
@@ -12323,7 +12308,7 @@ number:
The first rule keeps track of the largest line number seen so far; it
also stores each line into the array âarrâ, at an index that is the
-lineâs number. The second rule runs after all the input has been read,
+line's number. The second rule runs after all the input has been read,
to print out all the lines. When this program is run with the following
input:
@@ -12343,7 +12328,7 @@ Its output is:
If a line number is repeated, the last line with a given number
overrides the others. Gaps in the line numbers can be handled with an
-easy improvement to the programâs âENDâ rule, as follows:
+easy improvement to the program's âENDâ rule, as follows:
END {
for (x = 1; x <= max; x++)
@@ -12365,7 +12350,7 @@ In programs that use arrays, it is often necessary to
use a loop that
executes once for each element of an array. In other languages, where
arrays are contiguous and indices are limited to nonnegative integers,
this is easy: all the valid indices can be found by counting from the
-lowest index up to the highest. This technique wonât do the job in
+lowest index up to the highest. This technique won't do the job in
âawkâ, because any number or string can be an array index. So âawkâ
has
a special kind of âforâ statement for scanning an array:
@@ -12458,9 +12443,9 @@ which the array is traversed. This order is usually
based on the
internal implementation of arrays and will vary from one version of
âawkâ to the next.
- Often, though, you may wish to do something simple, such as âtraverse
-the array by comparing the indices in ascending order,â or âtraverse the
-array by comparing the values in descending order.â âgawkâ provides two
+ Often, though, you may wish to do something simple, such as "traverse
+the array by comparing the indices in ascending order," or "traverse the
+array by comparing the values in descending order." âgawkâ provides two
mechanisms that give you this control:
⢠Set âPROCINFO["sorted_in"]â to one of a set of predefined values.
@@ -12581,7 +12566,7 @@ traversal:
⢠The value of âPROCINFO["sorted_in"]â is global. That is, it
affects all array traversal âforâ loops. If you need to change it
- within your own code, you should see if itâs defined and save and
+ within your own code, you should see if it's defined and save and
restore the value:
...
@@ -12597,7 +12582,7 @@ traversal:
represented by â"@unsorted"â. You can also get the default
behavior by assigning the null string to âPROCINFO["sorted_in"]â or
by just deleting the â"sorted_in"â element from the âPROCINFOâ
- array with the âdeleteâ statement. (The âdeleteâ statement
hasnât
+ array with the âdeleteâ statement. (The âdeleteâ statement hasn't
been described yet; *note Delete::.)
In addition, âgawkâ provides built-in functions for sorting arrays;
@@ -12638,8 +12623,8 @@ string value â"12.153"â (using the default
conversion value of
âCONVFMTâ, â"%.6g"â). Thus, the array element âdata["12.153"]â is
assigned the value one. The program then changes the value of
âCONVFMTâ. The test â(xyz in data)â generates a new string value from
-âxyzââthis time â"12.15"ââbecause the value of âCONVFMTâ only
allows two
-significant digits. This test fails, because â"12.15"â is different
+âxyzâ--this time â"12.15"â--because the value of âCONVFMTâ only
allows
+two significant digits. This test fails, because â"12.15"â is different
from â"12.153"â.
According to the rules for conversions (*note Conversion::), integer
@@ -12650,7 +12635,7 @@ works:
for (i = 1; i <= maxsub; i++)
do something with array[i]
- The âinteger values always convert to strings as integersâ rule has
+ The "integer values always convert to strings as integers" rule has
an additional consequence for array indexing. Octal and hexadecimal
constants (*note Nondecimal-numbers::) are converted internally into
numbers, and their original form is forgotten. This means, for example,
@@ -12668,7 +12653,7 @@ File: gawk.info, Node: Uninitialized Subscripts,
Next: Delete, Prev: Numeric
8.3 Using Uninitialized Variables as Subscripts
===============================================
-Suppose itâs necessary to write a program to print the input data in
+Suppose it's necessary to write a program to print the input data in
reverse order. A reasonable attempt to do so (with some test data)
might look like this:
@@ -12701,8 +12686,8 @@ following version of the program works correctly:
print l[i]
}
- Here, the â++â forces âlinesâ to be numeric, thus making the âold
-valueâ numeric zero. This is then converted to â"0"â as the array
+ Here, the â++â forces âlinesâ to be numeric, thus making the "old
+value" numeric zero. This is then converted to â"0"â as the array
subscript.
Even though it is somewhat unusual, the null string (â""â) is a valid
@@ -12777,7 +12762,7 @@ Because there is no data to split out, the function
simply clears the
array and then returns.
CAUTION: Deleting all the elements from an array does not change
- its type; you cannot clear an array and then use the arrayâs name
+ its type; you cannot clear an array and then use the array's name
as a scalar (i.e., a regular variable). For example, the following
does not work:
@@ -12818,7 +12803,7 @@ when the value of âSUBSEPâ is â"@"â. The
numbers 5 and 12 are converted
to strings and concatenated with an â@â between them, yielding
â"5@12"â;
thus, the array element âfoo["5@12"]â is set to â"value"â.
- Once the elementâs value is stored, âawkâ has no record of whether it
+ Once the element's value is stored, âawkâ has no record of whether it
was stored with a single index or a sequence of indices. The two
expressions âfoo[5,12]â and âfoo[5 SUBSEP 12]â are always equivalent.
@@ -12880,9 +12865,9 @@ File: gawk.info, Node: Multiscanning, Up:
Multidimensional
8.5.1 Scanning Multidimensional Arrays
--------------------------------------
-There is no special âforâ statement for scanning a âmultidimensionalâ
+There is no special âforâ statement for scanning a "multidimensional"
array. There cannot be one, because, in truth, âawkâ does not have
-multidimensional arrays or elementsâthere is only a multidimensional
+multidimensional arrays or elements--there is only a multidimensional
_way of accessing_ an array.
However, if your program has an array that is always accessed as
@@ -12920,7 +12905,7 @@ File: gawk.info, Node: Arrays of Arrays, Next: Arrays
Summary, Prev: Multidim
8.6 Arrays of Arrays
====================
-âgawkâ goes beyond standard âawkââs multidimensional array access and
+âgawkâ goes beyond standard âawkâ's multidimensional array access and
provides true arrays of arrays. Elements of a subarray are referred to
by their own indices enclosed in square brackets, just like the elements
of the main array. For example, the following creates a two-element
@@ -12948,7 +12933,7 @@ itself an array and not a scalar:
a[4] = "An element in a jagged array"
The terms âdimensionâ, ârowâ, and âcolumnâ are meaningless when
-applied to such an array, but we will use âdimensionâ henceforth to
+applied to such an array, but we will use "dimension" henceforth to
imply the maximum number of indices needed to refer to an existing
element. The type of any element that has already been assigned cannot
be changed by assigning a value of a different type. You have to first
@@ -13022,7 +13007,7 @@ following code prints the elements of our main array
âaâ:
}
}
-*Note Walking Arrays:: for a user-defined function that âwalksâ an
+*Note Walking Arrays:: for a user-defined function that "walks" an
arbitrarily dimensioned array of arrays.
Recall that a reference to an uninitialized array element yields a
@@ -13057,7 +13042,7 @@ File: gawk.info, Node: Arrays Summary, Prev: Arrays
of Arrays, Up: Arrays
⢠Use âfor (INDX in ARRAY) ...â to scan through all the individual
elements of an array. In the body of the loop, INDX takes on the
- value of each elementâs index in turn.
+ value of each element's index in turn.
⢠The order in which a âfor (INDX in ARRAY)â loop traverses an array
is undefined in POSIX âawkâ and varies among implementations.
@@ -13092,7 +13077,7 @@ File: gawk.info, Node: Functions, Next: Library
Functions, Prev: Arrays, Up:
9 Functions
***********
-This major node describes âawkââs built-in functions, which fall into
+This major node describes âawkâ's built-in functions, which fall into
three categories: numeric, string, and I/O. âgawkâ provides additional
groups of functions to work with values that represent time, do bit
manipulation, sort arrays, provide type information, and
@@ -13143,7 +13128,7 @@ File: gawk.info, Node: Calling Built-in, Next:
Boolean Functions, Up: Built-i
9.1.1 Calling Built-in Functions
--------------------------------
-To call one of âawkââs built-in functions, write the name of the
+To call one of âawkâ's built-in functions, write the name of the
function followed by arguments in parentheses. For example, âatan2(y +
z, 1)â is a call to the function âatan2()â and has two arguments.
@@ -13151,7 +13136,7 @@ z, 1)â is a call to the function âatan2()â and
has two arguments.
opening parenthesis, but nonetheless it is good practice to avoid using
whitespace there. User-defined functions do not permit whitespace in
this way, and it is easier to avoid mistakes by following a simple
-convention that always worksâno whitespace after a function name.
+convention that always works--no whitespace after a function name.
Each built-in function accepts a certain number of arguments. In
some cases, arguments can be omitted. The defaults for omitted
@@ -13160,7 +13145,7 @@ individual functions. In some âawkâ
implementations, extra arguments
given to built-in functions are ignored. However, in âgawkâ, it is a
fatal error to give extra arguments to a built-in function.
- When a function is called, expressions that create the functionâs
+ When a function is called, expressions that create the function's
actual parameters are evaluated completely before the call is performed.
For example, in the following code fragment:
@@ -13169,7 +13154,7 @@ For example, in the following code fragment:
the variable âiâ is incremented to the value five before âsqrt()â is
called with a value of four for its actual parameter. The order of
-evaluation of the expressions used for the functionâs parameters is
+evaluation of the expressions used for the function's parameters is
undefined. Thus, avoid writing programs that assume that parameters are
evaluated from left to right or from right to left. For example:
@@ -13192,8 +13177,8 @@ compatibility mode (*note Options::):
âmkbool(EXPRESSION)â
Return a Boolean-typed value based on the regular Boolean value of
- EXPRESSION. Boolean âtrueâ values have numeric value one. Boolean
- âfalseâ values have numeric zero. This is discussed in more detail
+ EXPRESSION. Boolean "true" values have numeric value one. Boolean
+ "false" values have numeric zero. This is discussed in more detail
in *note Boolean Typed Values::.
@@ -13216,7 +13201,7 @@ brackets ([ ]):
âexp(X)â
Return the exponential of X (âe ^ Xâ) or report an error if X is
out of range. The range of values X can have depends on your
- machineâs floating-point representation.
+ machine's floating-point representation.
âint(X)â
Return the nearest integer to X, located between X and zero and
@@ -13225,7 +13210,7 @@ brackets ([ ]):
âlog(X)â
Return the natural logarithm of X, if X is positive; otherwise,
- return NaN (ânot a numberâ) on IEEE 754 systems. Additionally,
+ return NaN ("not a number") on IEEE 754 systems. Additionally,
âgawkâ prints a warning message when âxâ is negative.
ârand()â
@@ -13285,7 +13270,7 @@ brackets ([ ]):
time, the same sequence of random numbers is produced again.
CAUTION: Different âawkâ implementations use different
- random-number generators internally. Donât expect the same
+ random-number generators internally. Don't expect the same
âawkâ program to produce the same series of random numbers
when executed by different versions of âawkâ.
@@ -13414,13 +13399,13 @@ Options::):
actual sorting.
You are allowed to use the same array for both the SOURCE and DEST
- arguments, but doing so only makes sense if youâre also supplying
+ arguments, but doing so only makes sense if you're also supplying
the third argument.
âgensub(REGEXP, REPLACEMENT, HOWâ [â, TARGETâ]â) #â
Search the target string TARGET for matches of the regular
expression REGEXP. If HOW is a string beginning with âgâ or âGâ
- (short for âglobalâ), then replace all matches of REGEXP with
+ (short for "global"), then replace all matches of REGEXP with
REPLACEMENT. Otherwise, treat HOW as a number indicating which
match of REGEXP to replace. Treat numeric values less than one as
if they were one. If no TARGET is supplied, use â$0â. Return the
@@ -13468,7 +13453,7 @@ Options::):
one substitution is performed. If HOW is zero, âgawkâ issues a
warning message.
- If REGEXP does not match TARGET, âgensub()ââs return value is the
+ If REGEXP does not match TARGET, âgensub()â's return value is the
original unchanged value of TARGET. Note that, as mentioned above,
the returned value is a string, even if TARGET was not.
@@ -13480,7 +13465,7 @@ Options::):
âgsub(REGEXP, REPLACEMENTâ [â, TARGETâ]â)â
Search TARGET for _all_ of the longest, leftmost, _nonoverlapping_
matching substrings it can find and replace them with REPLACEMENT.
- The âgâ in âgsub()â stands for âglobal,â which means replace
+ The âgâ in âgsub()â stands for "global," which means replace
everywhere. For example:
{ gsub(/Britain/, "United Kingdom"); print }
@@ -13635,7 +13620,7 @@ Options::):
fatal error.
âpatsplit(STRING, ARRAYâ [â, FIELDPATâ [â, SEPSâ ] ]â) #â
- Divide STRING into pieces (or âfieldsâ) defined by FIELDPAT and
+ Divide STRING into pieces (or "fields") defined by FIELDPAT and
store the pieces in ARRAY and the separator strings in the SEPS
array. The first piece is stored in âARRAY[1]â, the second piece
in âARRAY[2]â, and so forth. The third argument, FIELDPAT, is a
@@ -13754,7 +13739,7 @@ Options::):
a string value; the automatic coercion of strings to numbers works
only for decimal data, not for octal or hexadecimal.(1)
- Note also that âstrtonum()â uses the current localeâs decimal point
+ Note also that âstrtonum()â uses the current locale's decimal point
for recognizing numbers (*note Locales::).
âsub(REGEXP, REPLACEMENTâ [â, TARGETâ]â)â
@@ -13771,7 +13756,7 @@ Options::):
implications for writing your program correctly.
This function is peculiar because TARGET is not simply used to
- compute a value, and not just any expression will doâit must be a
+ compute a value, and not just any expression will do--it must be a
variable, field, or array element so that âsub()â can store a
modified value there. If this argument is omitted, then the
default is to use and alter â$0â.(2) For example:
@@ -13800,7 +13785,7 @@ Options::):
⣠dCaaCbaaa
This shows how â&â can represent a nonconstant string and also
- illustrates the âleftmost, longestâ rule in regexp matching (*note
+ illustrates the "leftmost, longest" rule in regexp matching (*note
Leftmost Longest::).
The effect of this special character (â&â) can be turned off by
@@ -13843,7 +13828,7 @@ Options::):
remaining in the string, counting from character START.
If START is less than one, âsubstr()â treats it as if it was one.
- (POSIX doesnât specify what to do in this case: BWK âawkâ acts this
+ (POSIX doesn't specify what to do in this case: BWK âawkâ acts this
way, and therefore âgawkâ does too.) If START is greater than the
number of characters in the string, âsubstr()â returns the null
string. Similarly, if LENGTH is present but less than or equal to
@@ -13906,13 +13891,13 @@ Although this makes a certain amount of sense, it can
be surprising.
---------- Footnotes ----------
- (1) Unless you use the â--non-decimal-dataâ option, which isnât
+ (1) Unless you use the â--non-decimal-dataâ option, which isn't
recommended. *Note Nondecimal Data:: for more information.
(2) Note that this means that the record will first be regenerated
using the value of âOFSâ if any fields have been changed, and that the
fields will be updated after the substitution, even if the operation is
-a âno-opâ such as âsub(/^/, "")â.
+a "no-op" such as âsub(/^/, "")â.
(3) This is different from C and C++, in which the first character is
number zero.
@@ -13924,7 +13909,7 @@ File: gawk.info, Node: Gory Details, Up: String
Functions
.....................................................................
I collect spores, molds, and fungus.
- â _Dr. Egon Spengler (âGhostbusters,â 1984)_
+ -- _Dr. Egon Spengler ("Ghostbusters," 1984)_
CAUTION: This subsubsection has been reported to cause headaches.
You might want to skip it upon first reading.
@@ -13956,9 +13941,8 @@ generated text with a single â&â. Any other
â\â within the REPLACEMENT
string that did not precede an â&â was passed through unchanged. This
is illustrated in *note Table 9.1: table-sub-escapes.
-
You type âsub()â sees âsub()â generates
- âââ âââ- âââââ
+ ----- ------- ----------
â\&â â&â The matched text
â\\&â â\&â A literal â&â
â\\\&â â\&â A literal â&â
@@ -13980,7 +13964,7 @@ backslashes entered at the lexical level.)
get a literal â\â followed by the matched text.
Several editions of the POSIX standard attempted to fix this problem
-but werenât successful. The details are irrelevant at this point in
+but weren't successful. The details are irrelevant at this point in
time.
At one point, the âgawkâ maintainer submitted proposed text for a
@@ -13989,9 +13973,8 @@ the original existing practice. The proposed rules
have special cases
that make it possible to produce a â\â preceding the matched text. This
is shown in *note Table 9.2: table-sub-proposed.
-
You type âsub()â sees âsub()â generates
- âââ âââ- âââââ
+ ----- ------- ----------
â\\\\\\&â â\\\&â A literal â\&â
â\\\\&â â\\&â A literal â\â, followed
by the matched text
â\\&â â\&â A literal â&â
@@ -14008,7 +13991,7 @@ the output literally.
âgawkâ 3.0 and 3.1 follow these rules for âsub()â and âgsub()â.
The
POSIX standard took much longer to be revised than was expected. In
-addition, the âgawkâ maintainerâs proposal was lost during the
+addition, the âgawkâ maintainer's proposal was lost during the
standardization process. The final rules are somewhat simpler. The
results are similar except for one case.
@@ -14017,9 +14000,8 @@ literal â&â, â\\â produces a literal â\â,
and â\â followed by an
else is not special; the â\â is placed straight into the output. These
rules are presented in *note Table 9.3: table-posix-sub.
-
You type âsub()â sees âsub()â generates
- âââ âââ- âââââ
+ ----- ------- ----------
â\\\\\\&â â\\\&â A literal â\&â
â\\\\&â â\\&â A literal â\â, followed
by the matched text
â\\&â â\&â A literal â&â
@@ -14036,7 +14018,7 @@ Table 9.3: POSIX rules for âsub()â and âgsub()â
follow the proposed rules, as that had been its behavior for many years.
When version 4.0.0 was released, the âgawkâ maintainer made the POSIX
-rules the default, breaking well over a decadeâs worth of backward
+rules the default, breaking well over a decade's worth of backward
compatibility.(1) Needless to say, this was a bad idea, and as of
version 4.0.1, âgawkâ resumed its historical behavior, and only follows
the POSIX rules when â--posixâ is given.
@@ -14048,9 +14030,8 @@ subexpression is placed in the generated output.
Otherwise, no matter
what character follows the â\â, it appears in the generated text and the
â\â does not, as shown in *note Table 9.4: table-gensub-escapes.
-
You type âgensub()â sees âgensub()â generates
- âââ ââââ- ââââââ
+ ----- --------- ------------
â&â â&â The matched text
â\\&â â\&â A literal â&â
â\\\\â â\\â A literal â\â
@@ -14110,7 +14091,7 @@ parameters are enclosed in square brackets ([ ]):
sometimes it is necessary to force a program to âflushâ its buffers
(i.e., write the information to its destination, even if a buffer
is not full). This is the purpose of the âfflush()â
- functionââgawkâ also buffers its output, and the âfflush()â
+ function--âgawkâ also buffers its output, and the âfflush()â
function forces âgawkâ to flush its buffers.
Brian Kernighan added âfflush()â to his âawkâ in April 1992. For
@@ -14176,7 +14157,7 @@ is all buffered and sent down the pipe to âcatâ in
one shot.
âsystem(COMMAND)â
Execute the operating system command COMMAND and then return to the
- âawkâ program. Return COMMANDâs exit status (see further on).
+ âawkâ program. Return COMMAND's exit status (see further on).
For example, if the following fragment of code is put in your âawkâ
program:
@@ -14205,27 +14186,26 @@ is all buffered and sent down the pipe to âcatâ
in one shot.
NOTE: When â--sandboxâ is specified, the âsystem()â function
is disabled (*note Options::).
- On POSIX systems, a commandâs exit status is a 16-bit number. The
+ On POSIX systems, a command's exit status is a 16-bit number. The
exit value passed to the C âexit()â function is held in the
high-order eight bits. The low-order bits indicate if the process
was killed by a signal (bit 7) and if so, the guilty signal number
- (bits 0â6).
+ (bits 0-6).
- Traditionally, âawkââs âsystem()â function has simply returned
the
+ Traditionally, âawkâ's âsystem()â function has simply returned the
exit status value divided by 256. In the normal case this gives
the exit status but in the case of death-by-signal it yields a
- fractional floating-point value.(2) POSIX states that âawkââs
+ fractional floating-point value.(2) POSIX states that âawkâ's
âsystem()â should return the full 16-bit value.
âgawkâ steers a middle ground. The return values are summarized in
*note Table 9.5: table-system-return-values.
-
Situation Return value from âsystem()â
--------------------------------------------------------------------------
- â--traditionalâ C âsystem()ââs value divided by
256
- â--posixâ C âsystem()ââs value
- Normal exit of command Commandâs exit status
+ â--traditionalâ C âsystem()â's value divided by 256
+ â--posixâ C âsystem()â's value
+ Normal exit of command Command's exit status
Death by signal of command 256 + number of murderous signal
Death by signal of command 512 + number of murderous signal
with core dump
@@ -14233,7 +14213,7 @@ is all buffered and sent down the pipe to âcatâ in
one shot.
Table 9.5: Return values from âsystem()â
- As of August, 2018, BWK âawkâ now follows âgawkââs behavior for
the
+ As of August, 2018, BWK âawkâ now follows âgawkâ's behavior for the
return value of âsystem()â.
Controlling Output Buffering with âsystem()â
@@ -14363,7 +14343,7 @@ enclosed in square brackets ([ ]):
The âsystime()â function allows you to compare a timestamp from a log
file with the current time of day. In particular, it is easy to
determine how long ago a particular record was logged. It also allows
-you to produce log records using the âseconds since the epochâ format.
+you to produce log records using the "seconds since the epoch" format.
The âmktime()â function allows you to convert a textual
representation of a date and time into a timestamp. This makes it easy
@@ -14382,19 +14362,19 @@ FORMAT string.
the following date format specifications:
â%aâ
- The localeâs abbreviated weekday name.
+ The locale's abbreviated weekday name.
â%Aâ
- The localeâs full weekday name.
+ The locale's full weekday name.
â%bâ
- The localeâs abbreviated month name.
+ The locale's abbreviated month name.
â%Bâ
- The localeâs full month name.
+ The locale's full month name.
â%câ
- The localeâs âappropriateâ date and time representation. (This is
+ The locale's "appropriate" date and time representation. (This is
â%A %B %d %T %Yâ in the â"C"â locale.)
â%Câ
@@ -14402,7 +14382,7 @@ the following date format specifications:
100 and truncated to the next lower integer.
â%dâ
- The day of the month as a decimal number (01â31).
+ The day of the month as a decimal number (01-31).
â%Dâ
Equivalent to specifying â%m/%d/%yâ.
@@ -14416,7 +14396,7 @@ the following date format specifications:
â%gâ
The year modulo 100 of the ISO 8601 week number, as a decimal
- number (00â99). For example, January 1, 2012, is in week 53 of
+ number (00-99). For example, January 1, 2012, is in week 53 of
2011. Thus, the year of its ISO 8601 week number is 2011, even
though its year is 2012. Similarly, December 31, 2012, is in week
1 of 2013. Thus, the year of its ISO week number is 2013, even
@@ -14429,36 +14409,36 @@ the following date format specifications:
Equivalent to â%bâ.
â%Hâ
- The hour (24-hour clock) as a decimal number (00â23).
+ The hour (24-hour clock) as a decimal number (00-23).
â%Iâ
- The hour (12-hour clock) as a decimal number (01â12).
+ The hour (12-hour clock) as a decimal number (01-12).
â%jâ
- The day of the year as a decimal number (001â366).
+ The day of the year as a decimal number (001-366).
â%mâ
- The month as a decimal number (01â12).
+ The month as a decimal number (01-12).
â%Mâ
- The minute as a decimal number (00â59).
+ The minute as a decimal number (00-59).
â%nâ
A newline character (ASCII LF).
â%pâ
- The localeâs equivalent of the AM/PM designations associated with a
+ The locale's equivalent of the AM/PM designations associated with a
12-hour clock.
â%râ
- The localeâs 12-hour clock time. (This is â%I:%M:%S %pâ in the
+ The locale's 12-hour clock time. (This is â%I:%M:%S %pâ in the
â"C"â locale.)
â%Râ
Equivalent to specifying â%H:%Mâ.
â%Sâ
- The second as a decimal number (00â60).
+ The second as a decimal number (00-60).
â%tâ
A TAB character.
@@ -14467,37 +14447,37 @@ the following date format specifications:
Equivalent to specifying â%H:%M:%Sâ.
â%uâ
- The weekday as a decimal number (1â7). Monday is day one.
+ The weekday as a decimal number (1-7). Monday is day one.
â%Uâ
The week number of the year (with the first Sunday as the first day
- of week one) as a decimal number (00â53).
+ of week one) as a decimal number (00-53).
â%Vâ
The week number of the year (with the first Monday as the first day
- of week one) as a decimal number (01â53). The method for
+ of week one) as a decimal number (01-53). The method for
determining the week number is as specified by ISO 8601. (To wit:
if the week containing January 1 has four or more days in the new
year, then it is week one; otherwise it is the last week [52 or 53]
of the previous year and the next week is week one.)
â%wâ
- The weekday as a decimal number (0â6). Sunday is day zero.
+ The weekday as a decimal number (0-6). Sunday is day zero.
â%Wâ
The week number of the year (with the first Monday as the first day
- of week one) as a decimal number (00â53).
+ of week one) as a decimal number (00-53).
â%xâ
- The localeâs âappropriateâ date representation. (This is â%A %B
%d
+ The locale's "appropriate" date representation. (This is â%A %B %d
%Yâ in the â"C"â locale.)
â%Xâ
- The localeâs âappropriateâ time representation. (This is â%Tâ
in
+ The locale's "appropriate" time representation. (This is â%Tâ in
the â"C"â locale.)
â%yâ
- The year modulo 100 as a decimal number (00â99).
+ The year modulo 100 as a decimal number (00-99).
â%Yâ
The full year as a decimal number (e.g., 2015).
@@ -14512,7 +14492,7 @@ the following date format specifications:
â%Ec %EC %Ex %EX %Ey %EY %Od %Oe %OHâ
â%OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oyâ
- âAlternative representationsâ for the specifications that use only
+ "Alternative representations" for the specifications that use only
the second letter (â%câ, â%Câ, and so on).(5) (These facilitate
compliance with the POSIX âdateâ utility.)
@@ -14529,11 +14509,11 @@ compile âgawkâ (*note Installation::), then the
following additional
format specifications are available:
â%kâ
- The hour (24-hour clock) as a decimal number (0â23). Single-digit
+ The hour (24-hour clock) as a decimal number (0-23). Single-digit
numbers are padded with a space.
â%lâ
- The hour (12-hour clock) as a decimal number (1â12). Single-digit
+ The hour (12-hour clock) as a decimal number (1-12). Single-digit
numbers are padded with a space.
â%sâ
@@ -14553,7 +14533,7 @@ format specifiers in the string. For example:
⣠Today is Monday, September 22, 2014.
Here is the âgawkâ version of the âdateâ utility. It has a shell
-âwrapperâ to handle the â-uâ option, which requires that âdateâ
run as
+"wrapper" to handle the â-uâ option, which requires that âdateâ run as
if the time zone is set to UTC:
#! /bin/sh
@@ -14583,7 +14563,7 @@ if the time zone is set to UTC:
---------- Footnotes ----------
- (1) *Note Glossary::, especially the entries âEpochâ and âUTC.â
+ (1) *Note Glossary::, especially the entries "Epoch" and "UTC."
(2) The GNU âdateâ utility can also do many of the things described
here. Its use may be preferable for simple time-related operations in
@@ -14592,17 +14572,17 @@ shell scripts.
(3) Occasionally there are minutes in a year with a leap second,
which is why the seconds can go up to 60.
- (4) Unfortunately, not every systemâs âstrftime()â necessarily
+ (4) Unfortunately, not every system's âstrftime()â necessarily
supports all of the conversions listed here.
- (5) If you donât understand any of this, donât worry about it; these
-facilities are meant to make it easier to âinternationalizeâ programs.
+ (5) If you don't understand any of this, don't worry about it; these
+facilities are meant to make it easier to "internationalize" programs.
Other internationalization features are described in *note
Internationalization::.
(6) This is because ISO C leaves the behavior of the C version of
-âstrftime()â undefined and âgawkâ uses the systemâs version of
-âstrftime()â if itâs there. Typically, the conversion specifier either
+âstrftime()â undefined and âgawkâ uses the system's version of
+âstrftime()â if it's there. Typically, the conversion specifier either
does not appear in the returned string or appears literally.
@@ -14611,8 +14591,8 @@ File: gawk.info, Node: Bitwise Functions, Next: Type
Functions, Prev: Time Fu
9.1.7 Bit-Manipulation Functions
--------------------------------
- I can explain it for you, but I canât understand it for you.
- â _Anonymous_
+ I can explain it for you, but I can't understand it for you.
+ -- _Anonymous_
Many languages provide the ability to perform âbitwiseâ operations on
two integer numbers. In other words, the operation is performed on each
@@ -14620,7 +14600,6 @@ successive pair of bits in the operands. Three common
operations are
bitwise AND, OR, and XOR. The operations are described in *note Table
9.6: table-bitwise-ops.
-
Bit operator
| AND | OR | XOR
|---+---+---+---+---+---
@@ -14635,14 +14614,14 @@ Table 9.6: Bitwise operations
bits are 1. The result of an OR operation is 1 if _either_ bit is 1.
The result of an XOR operation is 1 if either bit is 1, but not both.
The next operation is the âcomplementâ; the complement of 1 is 0 and the
-complement of 0 is 1. Thus, this operation âflipsâ all the bits of a
+complement of 0 is 1. Thus, this operation "flips" all the bits of a
given value.
Finally, two other common operations are to shift the bits left or
right. For example, if you have a bit string â10111001â and you shift
it right by three bits, you end up with â00010111â.(1) If you start
over again with â10111001â and shift it left by three bits, you end up
-with â11001000â. The following list describes âgawkââs built-in
+with â11001000â. The following list describes âgawkâ's built-in
functions that implement the bitwise operations. Optional parameters
are enclosed in square brackets ([ ]):
@@ -14669,8 +14648,8 @@ are enclosed in square brackets ([ ]):
CAUTION: Beginning with âgawkâ version 4.2, negative operands are
not allowed for any of these functions. A negative operand
- produces a fatal error. See the sidebar âBeware The Smoke and
- Mirrors!â for more information as to why.
+ produces a fatal error. See the sidebar "Beware The Smoke and
+ Mirrors!" for more information as to why.
Here is a user-defined function (*note User-defined::) that
illustrates the use of these functions:
@@ -14759,7 +14738,7 @@ This is particularly noticeable with the âcompl()â
function:
$ gawk -M 'BEGIN { print compl(42) }'
⣠-43
- Whatâs going on becomes clear when printing the results in
+ What's going on becomes clear when printing the results in
hexadecimal:
$ gawk 'BEGIN { printf "%#x\n", compl(42) }'
@@ -14781,10 +14760,10 @@ operations is probably a bad idea; caveat emptor!
---------- Footnotes ----------
(1) This example shows that zeros come in on the left side. For
-âgawkâ, this is always true, but in some languages, itâs possible to
+âgawkâ, this is always true, but in some languages, it's possible to
have the left side fill with ones.
- (2) If you donât understand this paragraph, the upshot is that âgawkâ
+ (2) If you don't understand this paragraph, the upshot is that âgawkâ
can only store a particular range of integer values; numbers outside
that range are reduced to fit within the range.
@@ -14907,9 +14886,9 @@ story. Optional parameters are enclosed in square
brackets ([ ]):
âbindtextdomain(DIRECTORYâ [â,â DOMAIN]â)â
Set the directory in which âgawkâ will look for message translation
- files, in case they will not or cannot be placed in the âstandardâ
+ files, in case they will not or cannot be placed in the "standard"
locations (e.g., during testing). It returns the directory in
- which DOMAIN is âbound.â
+ which DOMAIN is "bound."
The default DOMAIN is the value of âTEXTDOMAINâ. If DIRECTORY is
the null string (â""â), then âbindtextdomain()â returns the
current
@@ -14955,9 +14934,9 @@ File: gawk.info, Node: Definition Syntax, Next:
Function Example, Up: User-de
9.2.1 Function Definition Syntax
--------------------------------
- Itâs entirely fair to say that the awk syntax for local variable
+ It's entirely fair to say that the awk syntax for local variable
definitions is appallingly awful.
- â _Brian Kernighan_
+ -- _Brian Kernighan_
Definitions of functions can appear anywhere between the rules of an
âawkâ program. Thus, the general form of an âawkâ program is extended
@@ -14975,12 +14954,12 @@ starting to execute any of it.
Here, NAME is the name of the function to define. A valid function name
is like a valid variable name: a sequence of letters, digits, and
-underscores that doesnât start with a digit. Here too, only the 52
+underscores that doesn't start with a digit. Here too, only the 52
upper- and lowercase English letters may be used in a function name.
Within a single âawkâ program, any particular name can only be used as a
variable, array, or function.
- PARAMETER-LIST is an optional list of the functionâs arguments and
+ PARAMETER-LIST is an optional list of the function's arguments and
local variable names, separated by commas. When the function is called,
the argument names are used to hold the argument values given in the
call.
@@ -15032,7 +15011,7 @@ in the rest of the program. The shadowed variables are
not accessible
in the function definition, because there is no way to name them while
their names have been taken away for the arguments and local variables.
All other variables used in the âawkâ program can be referenced or set
-normally in the functionâs body.
+normally in the function's body.
The arguments and local variables last only as long as the function
body is executing. Once the body finishes, you can once again access
@@ -15068,7 +15047,7 @@ keyword âfunctionâ when defining a function.
---------- Footnotes ----------
- (1) This program wonât actually run, because âfoo()â is undefined.
+ (1) This program won't actually run, because âfoo()â is undefined.
File: gawk.info, Node: Function Example, Next: Function Calling, Prev:
Definition Syntax, Up: User-defined
@@ -15178,7 +15157,7 @@ the function.
* Menu:
-* Calling A Function:: Donât use spaces.
+* Calling A Function:: Don't use spaces.
* Variable Scope:: Controlling variable scope.
* Pass By Value/Reference:: Passing parameters.
* Function Caveats:: Other points to know about functions.
@@ -15343,14 +15322,14 @@ argument is passed by value.
Passing an argument by value means that when a function is called, it
is given a _copy_ of the value of this argument. The caller may use a
variable as the expression for the argument, but the called function
-does not know thisâit only knows what value the argument had. For
+does not know this--it only knows what value the argument had. For
example, if you write the following code:
foo = "bar"
z = myfunc(foo)
-then you should not think of the argument to âmyfunc()â as being âthe
-variable âfooâ.â Instead, think of the argument as the string value
+then you should not think of the argument to âmyfunc()â as being "the
+variable âfooâ." Instead, think of the argument as the string value
â"bar"â. If the function âmyfunc()â alters the values of its local
variables, this has no effect on any other variables. Thus, if
âmyfunc()â does this:
@@ -15447,13 +15426,13 @@ with more parameters than it accepts gives the false
impression that
those values are important to the function, when in fact they are not.
Because this is such a bad practice, âgawkâ _unconditionally_ issues
-a warning whenever it executes such a function call. (If you donât like
-the warning, fix your code! Itâs incorrect, after all.)
+a warning whenever it executes such a function call. (If you don't like
+the warning, fix your code! It's incorrect, after all.)
---------- Footnotes ----------
(1) Said person might even be you, sometime in the future, at which
-point you will wonder, âwhat was I thinking?!?â
+point you will wonder, "what was I thinking?!?"
File: gawk.info, Node: Return Statement, Next: Dynamic Typing, Prev:
Function Calling, Up: User-defined
@@ -15546,11 +15525,11 @@ File: gawk.info, Node: Dynamic Typing, Prev: Return
Statement, Up: User-defin
9.2.5 Functions and Their Effects on Variable Typing
----------------------------------------------------
- Itâs a desert topping!
- Itâs a floor wax!
- â _Saturday Night Live (back when it used to be funny)_
+ It's a desert topping!
+ It's a floor wax!
+ -- _Saturday Night Live (back when it used to be funny)_
- âawkâ is a very fluid language. It is possible that âawkâ canât
tell
+ âawkâ is a very fluid language. It is possible that âawkâ can't
tell
if an identifier represents a scalar variable or an array until runtime.
Here is an annotated sample program:
@@ -15591,7 +15570,7 @@ call, though, then âawkâ does report the second
error.
Here, the function uses its parameter differently depending upon the
value of the global variable âAâ. If âAâ is zero, the parameter
âarrâ
-is treated as a scalar. Otherwise itâs treated as an array.
+is treated as a scalar. Otherwise it's treated as an array.
There are two ways this program might behave. âawkâ could notice
that in the main program, âaâ is subscripted, and so mark it as an array
@@ -15632,12 +15611,12 @@ which should be processed differently.
Normally, you would have to use a series of âifâ-âelseâ statements
to
decide which function to call. By using âindirectâ function calls, you
can specify the name of the function to call as a string variable, and
-then call the function. Letâs look at an example.
+then call the function. Let's look at an example.
Suppose you have a file with your test scores for the classes you are
taking, and you wish to get the sum and the average of your test scores.
The first field is the class name. The following fields are the
-functions to call to process the data, up to a âmarkerâ field âdata:â.
+functions to call to process the data, up to a "marker" field âdata:â.
Following the marker, to the end of the record, are the various numeric
test scores.
@@ -15751,10 +15730,10 @@ to force it to be a string value.)
⣠average: <94.025>
The ability to use indirect function calls is more powerful than you
-may think at first. The C and C++ languages provide âfunction
-pointers,â which are a mechanism for calling a function chosen at
+may think at first. The C and C++ languages provide "function
+pointers," which are a mechanism for calling a function chosen at
runtime. One of the most well-known uses of this ability is the C
-âqsort()â function, which sorts an array using the famous âquicksortâ
+âqsort()â function, which sorts an array using the famous "quicksort"
algorithm (see the Wikipedia article
(https://en.wikipedia.org/wiki/Quicksort) for more information). To use
this function, you supply a pointer to a comparison function. This
@@ -15794,7 +15773,7 @@ mechanism allows you to sort arbitrary data in an
arbitrary fashion.
The âquicksort()â function receives the âdataâ array, the starting
and ending indices to sort (âleftâ and ârightâ), and the name of a
-function that performs a âless thanâ comparison. It then implements the
+function that performs a "less than" comparison. It then implements the
quicksort algorithm.
To make use of the sorting function, we return to our previous
@@ -15815,7 +15794,7 @@ example. The first thing to do is write some
comparison functions:
}
The ânum_ge()â function is needed to perform a descending sort; when
-used to perform a âless thanâ test, it actually does the opposite
+used to perform a "less than" test, it actually does the opposite
(greater than or equal to), which yields data sorted in descending
order.
@@ -15919,7 +15898,7 @@ functions indirectly, as follows.
arguments for that function causes a fatal error. For example,
calling âlength()â with two arguments. These errors are found at
runtime instead of when âgawkâ parses your program, since âgawkâ
- doesnât know until runtime if you have passed the correct number of
+ doesn't know until runtime if you have passed the correct number of
arguments or not.
âgawkâ does its best to make indirect function calls efficient. For
@@ -15953,7 +15932,7 @@ File: gawk.info, Node: Functions Summary, Prev:
Indirect Calls, Up: Functions
not defined. The return value can be ignored.
⢠The handling of backslash in âsub()â and âgsub()â is not simple.
- It is more straightforward in âgawkââs âgensub()â function, but
+ It is more straightforward in âgawkâ's âgensub()â function, but
that function still requires care in its use.
⢠User-defined functions provide important capabilities but come with
@@ -15966,7 +15945,7 @@ File: gawk.info, Node: Functions Summary, Prev:
Indirect Calls, Up: Functions
⢠User-defined functions may call other user-defined (and built-in)
functions and may call themselves recursively. Function parameters
- âhideâ any global variables of the same names. You cannot use the
+ "hide" any global variables of the same names. You cannot use the
name of a reserved variable (such as âARGCâ) as the name of a
parameter in user-defined functions.
@@ -15976,7 +15955,7 @@ File: gawk.info, Node: Functions Summary, Prev:
Indirect Calls, Up: Functions
has returned.
⢠Use the âreturnâ statement to return from a user-defined function.
- An optional expression becomes the functionâs return value. Only
+ An optional expression becomes the function's return value. Only
scalar values may be returned by a function.
⢠If a variable that has never been used is passed to a user-defined
@@ -16085,25 +16064,25 @@ function). There is no intermediate state analogous
to âstaticâ
variables in C.
Library functions often need to have global variables that they can
-use to preserve state information between calls to the functionâfor
-example, âgetopt()ââs variable â_optiâ (*note Getopt Function::).
Such
+use to preserve state information between calls to the function--for
+example, âgetopt()â's variable â_optiâ (*note Getopt Function::). Such
variables are called âprivateâ, as the only functions that need to use
them are the ones in the library.
When writing a library function, you should try to choose names for
your private variables that will not conflict with any variables used by
-either another library function or a userâs main program. For example,
+either another library function or a user's main program. For example,
a name like âiâ or âjâ is not a good choice, because user programs
often
use variable names like these for their own purposes.
The example programs shown in this major node all start the names of
-their private variables with an underscore (â_â). Users generally donât
+their private variables with an underscore (â_â). Users generally don't
use leading underscores in their variable names, so this convention
immediately decreases the chances that the variable names will be
-accidentally shared with the userâs program.
+accidentally shared with the user's program.
In addition, several of the library functions use a prefix that helps
-indicate what function or set of functions use the variablesâfor
+indicate what function or set of functions use the variables--for
example, â_pw_byname()â in the user database routines (*note Passwd
Functions::). This convention is recommended, as it even further
decreases the chance of inadvertent conflict among variable names. Note
@@ -16112,15 +16091,15 @@ private function names.(1)
As a final note on variable naming, if a function makes global
variables available for use by a main program, it is a good convention
-to start those variablesâ names with a capital letterâfor example,
-âgetopt()ââs âOpterrâ and âOptindâ variables (*note Getopt
Function::).
+to start those variables' names with a capital letter--for example,
+âgetopt()â's âOpterrâ and âOptindâ variables (*note Getopt
Function::).
The leading capital letter indicates that it is global, while the fact
that the variable name is not all capital letters indicates that the
-variable is not one of âawkââs predefined variables, such as âFSâ.
+variable is not one of âawkâ's predefined variables, such as âFSâ.
It is also important that _all_ variables in library functions that
do not need to save state are, in fact, declared local.(2) If this is
-not done, the variables could accidentally be used in the userâs
+not done, the variables could accidentally be used in the user's
program, leading to bugs that are very difficult to track down:
function lib_func(x, y, l1, l2)
@@ -16133,7 +16112,7 @@ program, leading to bugs that are very difficult to
track down:
A different convention, common in the Tcl community, is to use a
single associative array to hold the values needed by the library
-function(s), or âpackage.â This significantly decreases the number of
+function(s), or "package." This significantly decreases the number of
actual global names in use. For example, the functions described in
*note Passwd Functions:: might have used array elements
âPW_data["inited"]â, âPW_data["total"]â, âPW_data["count"]â, and
@@ -16141,7 +16120,7 @@ actual global names in use. For example, the functions
described in
and â_pw_countâ.
The conventions presented in this minor node are exactly that:
-conventions. You are not required to write your programs this wayâwe
+conventions. You are not required to write your programs this way--we
merely recommend that you do so.
Beginning with version 5.0, âgawkâ provides a powerful mechanism for
@@ -16155,7 +16134,7 @@ use this convention, this was not done, in order to
show how our own
âawkâ programming style has evolved and to provide some basis for this
discussion.
- (2) âgawkââs â--dump-variablesâ command-line option is useful for
+ (2) âgawkâ's â--dump-variablesâ command-line option is useful for
verifying this.
@@ -16331,7 +16310,7 @@ statement jumps to the âENDâ rule. If the
âENDâ rule finds
The purpose of the test in the âENDâ rule is to keep any other âENDâ
rules from running. When an assertion fails, the program should exit
immediately. If no assertions fail, then â_assert_exitâ is still false
-when the âENDâ rule is run normally, and the rest of the programâs
âENDâ
+when the âENDâ rule is run normally, and the rest of the program's
âENDâ
rules execute. For all of this to work correctly, âassert.awkâ must be
the first source file read by âawkâ. The function can be used in a
program in the following way:
@@ -16364,14 +16343,14 @@ File: gawk.info, Node: Round Function, Next: Cliff
Random Function, Prev: Ass
-----------------------
The way âprintfâ and âsprintf()â (*note Printf::) perform rounding
often
-depends upon the systemâs C âsprintf()â subroutine. On many machines,
-âsprintf()â rounding is âunbiasedâ, which means it doesnât always
round
+depends upon the system's C âsprintf()â subroutine. On many machines,
+âsprintf()â rounding is âunbiasedâ, which means it doesn't always round
a trailing .5 up, contrary to naive expectations. In unbiased rounding,
.5 rounds to even, rather than always up, so 1.5 rounds to 2 but 4.5
rounds to 4. This means that if you are using a format that does
rounding (e.g., â"%.0f"â), you should check what your system does. The
following function does traditional rounding; it might be useful if your
-âawkââs âprintfâ does unbiased rounding:
+âawkâ's âprintfâ does unbiased rounding:
# round.awk --- do normal rounding
@@ -16410,8 +16389,8 @@ File: gawk.info, Node: Cliff Random Function, Next:
Ordinal Functions, Prev:
The Cliff random number generator
(http://mathworld.wolfram.com/CliffRandomNumberGenerator.html) is a very
-simple random number generator that âpasses the noise sphere test for
-randomness by showing no structure.â It is easily programmed, in less
+simple random number generator that "passes the noise sphere test for
+randomness by showing no structure." It is easily programmed, in less
than 10 lines of âawkâ code:
# cliff_rand.awk --- generate Cliff random numbers
@@ -16426,9 +16405,9 @@ than 10 lines of âawkâ code:
return _cliff_seed
}
- This algorithm requires an initial âseedâ of 0.1. Each new value
+ This algorithm requires an initial "seed" of 0.1. Each new value
uses the current seed as input for the calculation. If the built-in
-ârand()â function (*note Numeric Functions::) isnât random enough, you
+ârand()â function (*note Numeric Functions::) isn't random enough, you
might try using this function instead.
@@ -16439,7 +16418,7 @@ File: gawk.info, Node: Ordinal Functions, Next: Join
Function, Prev: Cliff Ra
One commercial implementation of âawkâ supplies a built-in function,
âord()â, which takes a character and returns the numeric value for that
-character in the machineâs character set. If the string passed to
+character in the machine's character set. If the string passed to
âord()â has more than one character, only the first one is used.
The inverse of this function is âchr()â (from the function of the
@@ -16512,7 +16491,7 @@ on some older systems, but they are not really worth
worrying about:
An obvious improvement to these functions is to move the code for the
â_ord_initâ function into the body of the âBEGINâ rule. It was written
-this way initially for ease of development. There is a âtest programâ
+this way initially for ease of development. There is a "test program"
in a âBEGINâ rule, to test the function. It is commented out for
production use.
@@ -16542,7 +16521,7 @@ application programs (*note Sample Programs::).
but it should also have a reasonable default behavior. It is called
with an array as well as the beginning and ending indices of the
elements in the array to be merged. This assumes that the array indices
-are numericâa reasonable assumption, as the array was likely created
+are numeric--a reasonable assumption, as the array was likely created
with âsplit()â (*note String Functions::):
# join.awk --- join an array into a string
@@ -16564,7 +16543,7 @@ the strings back together. If the caller supplies a
nonempty value,
âjoin()â uses it; if it is not supplied, it has a null value. In this
case, âjoin()â uses a single space as a default separator for the
strings. If the value is equal to âSUBSEPâ, then âjoin()â joins the
-strings with no separator between them. âSUBSEPâ serves as a âmagicâ
+strings with no separator between them. âSUBSEPâ serves as a "magic"
value to indicate that there should be no separation between the
component strings.(1)
@@ -16813,7 +16792,7 @@ File: gawk.info, Node: To CSV Function, Prev:
Isnumeric Function, Up: General
10.2.11 Producing CSV Data
--------------------------
-âgawkââs â--csvâ option causes âgawkâ to process CSV data (*note
Comma
+âgawkâ's â--csvâ option causes âgawkâ to process CSV data (*note
Comma
Separated Fields::).
But what if you have regular data that you want to output in CSV
@@ -16905,7 +16884,7 @@ add new special patterns to âgawkâ, named
âBEGIN_FILEâ and âEND_FILE
that would have the desired behavior. He even supplied us the code to
do so.
- Adding these special patterns to âgawkâ wasnât necessary; the job can
+ Adding these special patterns to âgawkâ wasn't necessary; the job can
be done cleanly in âawkâ itself, as illustrated by the following library
program. It arranges to call two user-supplied functions, âbeginfile()â
and âendfile()â, at the beginning and end of each data file. Besides
@@ -16929,10 +16908,10 @@ _portably_; this works with any implementation of
âawkâ:
END { endfile(FILENAME) }
- This file must be loaded before the userâs âmainâ program, so that
+ This file must be loaded before the user's "main" program, so that
the rule it supplies is executed first.
- This rule relies on âawkââs âFILENAMEâ variable, which
automatically
+ This rule relies on âawkâ's âFILENAMEâ variable, which automatically
changes for each new data file. The current file name is saved in a
private variable, â_oldfilenameâ. If âFILENAMEâ does not equal
â_oldfilenameâ, then a new data file is being processed and it is
@@ -16946,7 +16925,7 @@ correctly even for the first data file.
The program also supplies an âENDâ rule to do the final processing
for the last file. Because this âENDâ rule comes before any âENDâ
rules
-supplied in the âmainâ program, âendfile()â is called first. Once
+supplied in the "main" program, âendfile()â is called first. Once
again, the value of multiple âBEGINâ and âENDâ rules should be clear.
If the same data file occurs twice in a row on the command line, then
@@ -16980,7 +16959,7 @@ patterns?
immediate fatal error. In this case, there is no way for a user-defined
function to deal with the problem, as the mechanism for calling it
relies on the file being open and at the first record. Thus, the main
-reason for âBEGINFILEâ is to give you a âhookâ to catch files that
+reason for âBEGINFILEâ is to give you a "hook" to catch files that
cannot be processed. âENDFILEâ exists for symmetry, and because it
provides an easy way to do per-file cleanup processing. For more
information, refer to *note BEGINFILE/ENDFILE::.
@@ -16993,11 +16972,11 @@ File: gawk.info, Node: Rewind Function, Next: File
Checking, Prev: Filetrans
Another request for a new built-in function was for a function that
would make it possible to reread the current file. The requesting user
-didnât want to have to use âgetlineâ (*note Getline::) inside a loop.
+didn't want to have to use âgetlineâ (*note Getline::) inside a loop.
However, as long as you are not in the âENDâ rule, it is quite easy
to arrange to immediately close the current input file and then start
-over with it from the top. For lack of a better name, weâll call the
+over with it from the top. For lack of a better name, we'll call the
function ârewind()â:
# rewind.awk --- rewind the current file and start over
@@ -17021,12 +17000,12 @@ function ârewind()â:
The ârewind()â function relies on the âARGINDâ variable (*note
Auto-set::), which is specific to âgawkâ. It also relies on the
ânextfileâ keyword (*note Nextfile Statement::). Because of this, you
-should not call it from an âENDFILEâ rule. (This isnât necessary
+should not call it from an âENDFILEâ rule. (This isn't necessary
anyway, because âgawkâ goes to the next file as soon as an âENDFILEâ
rule finishes!)
You need to be careful calling ârewind()â. You can end up causing
-infinite recursion if you donât pay attention. Here is an example use:
+infinite recursion if you don't pay attention. Here is an example use:
$ cat data
⣠a
@@ -17058,7 +17037,7 @@ File: gawk.info, Node: File Checking, Next: Empty
Files, Prev: Rewind Functio
10.3.3 Checking for Readable Data files
---------------------------------------
-Normally, if you give âawkâ a data file that isnât readable, it stops
+Normally, if you give âawkâ a data file that isn't readable, it stops
with a fatal error. There are times when you might want to just ignore
such files and keep going.(1) You can do this by prepending the
following program to your âawkâ program:
@@ -17077,8 +17056,8 @@ following program to your âawkâ program:
}
}
- This works, because the âgetlineâ wonât be fatal. Removing the
-element from âARGVâ with âdeleteâ skips the file (because itâs no
longer
+ This works, because the âgetlineâ won't be fatal. Removing the
+element from âARGVâ with âdeleteâ skips the file (because it's no
longer
in the list). See also *note ARGC and ARGV::.
Because âawkâ variable names only allow the English letters, the
@@ -17088,7 +17067,7 @@ as â[:alpha:]â and â[:alnum:]â (*note Bracket
Expressions::).
---------- Footnotes ----------
(1) The âBEGINFILEâ special pattern (*note BEGINFILE/ENDFILE::)
-provides an alternative mechanism for dealing with files that canât be
+provides an alternative mechanism for dealing with files that can't be
opened. However, the code here provides a portable solution.
@@ -17098,13 +17077,13 @@ File: gawk.info, Node: Empty Files, Next: Ignoring
Assigns, Prev: File Checki
-------------------------------------
All known âawkâ implementations silently skip over zero-length files.
-This is a by-product of âawkââs implicit
+This is a by-product of âawkâ's implicit
read-a-record-and-match-against-the-rules loop: when âawkâ tries to read
a record from an empty file, it immediately receives an end-of-file
indication, closes the file, and proceeds on to the next command-line
data file, _without_ executing any user-level âawkâ program code.
- Using âgawkââs âARGINDâ variable (*note Built-in Variables::), it
is
+ Using âgawkâ's âARGINDâ variable (*note Built-in Variables::), it is
possible to detect when an empty data file has been skipped. Similar to
the library file presented in *note Filetrans Function::, the following
library file calls a function named âzerofile()â that the user must
@@ -17194,7 +17173,7 @@ Most utilities on POSIX-compatible systems take options
on the command
line that can be used to change the way a program behaves. âawkâ is an
example of such a program (*note Options::). Often, options take
âargumentsâ (i.e., data that the program needs to correctly obey the
-command-line option). For example, âawkââs â-Fâ option requires a
+command-line option). For example, âawkâ's â-Fâ option requires a
string to use as the field separator. The first occurrence on the
command line of either â--â or a string that does not begin with â-â
ends the options.
@@ -17224,7 +17203,7 @@ following are valid ways of invoking the program:
prog -acbfoo data1 data2 data3
Notice that when the argument is grouped with its option, the rest of
-the argument is considered to be the optionâs argument. In this
+the argument is considered to be the option's argument. In this
example, â-acbfooâ indicates that all of the â-aâ, â-bâ, and
â-câ
options were supplied, and that âfooâ is the argument to the â-bâ
option.
@@ -17279,7 +17258,7 @@ command-line arguments for âawkâ:
...
}
- The GNU projectâs version of the original Unix utilities popularized
+ The GNU project's version of the original Unix utilities popularized
the use of long command line options. For example, â--helpâ in addition
to â-hâ. Arguments to long options are either provided as separate
command line arguments (â--source 'PROGRAM-TEXT'â) or separated from the
@@ -17320,7 +17299,7 @@ individual characters (*note String Functions::).(1)
The function starts out with comments presenting a list of the global
variables it uses, what the return values are, what they mean, and any
-global variables that are âprivateâ to this library function. Such
+global variables that are "private" to this library function. Such
documentation is essential for any program, and particularly for library
functions.
@@ -17494,7 +17473,7 @@ long option (minus its leading dashes).
The âBEGINâ rule initializes both âOpterrâ and âOptindâ to one.
âOpterrâ is set to one, because the default behavior is for âgetopt()â
to print a diagnostic message upon seeing an invalid option. âOptindâ
-is set to one, because thereâs no reason to look at the program name,
+is set to one, because there's no reason to look at the program name,
which is in âARGV[0]â:
BEGIN {
@@ -17553,7 +17532,7 @@ that it does not try to interpret the â-aâ, etc.,
as its own options.
not try to process the command-line options as file names.
Using â#!â with the â-Eâ option may help avoid conflicts between
your
-programâs options and âgawkââs options, as â-Eâ causes âgawkâ
to abandon
+program's options and âgawkâ's options, as â-Eâ causes âgawkâ to
abandon
processing of further options (*note Executable Scripts:: and *note
Options::).
@@ -17573,8 +17552,8 @@ File: gawk.info, Node: Passwd Functions, Next: Group
Functions, Prev: Getopt
==============================
The âPROCINFOâ array (*note Built-in Variables::) provides access to the
-current userâs real and effective user and group ID numbers, and, if
-available, the userâs supplementary group set. However, because these
+current user's real and effective user and group ID numbers, and, if
+available, the user's supplementary group set. However, because these
are numbers, they do not provide very useful information to the average
user. There needs to be some way to find the user information
associated with the user and group ID numbers. This minor node presents
@@ -17585,19 +17564,19 @@ from the group database.
The POSIX standard does not define the file where user information is
kept. Instead, it provides the â<pwd.h>â header file and several C
language subroutines for obtaining user information. The primary
-function is âgetpwent()â, for âget password entry.â The âpasswordâ
comes
-from the original user database file, â/etc/passwdâ, which stores user
-information along with the encrypted passwords (hence the name).
+function is âgetpwent()â, for "get password entry." The "password"
+comes from the original user database file, â/etc/passwdâ, which stores
+user information along with the encrypted passwords (hence the name).
Although an âawkâ program could simply read â/etc/passwdâ directly,
-this file may not contain complete information about the systemâs set of
+this file may not contain complete information about the system's set of
users.(1) To be sure you are able to produce a readable and complete
version of the user database, it is necessary to write a small C program
that calls âgetpwent()â. âgetpwent()â is defined as returning a
pointer
to a âstruct passwdâ. Each time it is called, it returns the next entry
in the database. When there are no more entries, it returns âNULLâ, the
null pointer. When this happens, the C program should call âendpwent()â
-to close the database. Following is âpwcatâ, a C program that âcatsâ
+to close the database. Following is âpwcatâ, a C program that "cats"
the password database:
/*
@@ -17622,39 +17601,39 @@ the password database:
return 0;
}
- If you donât understand C, donât worry about it. The output from
+ If you don't understand C, don't worry about it. The output from
âpwcatâ is the user database, in the traditional â/etc/passwdâ format
of
colon-separated fields. The fields are:
Login name
- The userâs login name.
+ The user's login name.
Encrypted password
- The userâs encrypted password. This may not be available on some
+ The user's encrypted password. This may not be available on some
systems.
User-ID
- The userâs numeric user ID number. (On some systems, itâs a C
+ The user's numeric user ID number. (On some systems, it's a C
âlongâ, and not an âintâ. Thus, we cast it to âlongâ for all
cases.)
Group-ID
- The userâs numeric group ID number. (Similar comments about âlongâ
+ The user's numeric group ID number. (Similar comments about âlongâ
versus âintâ apply here.)
Full name
- The userâs full name, and perhaps other information associated with
+ The user's full name, and perhaps other information associated with
the user.
Home directory
- The userâs login (or âhomeâ) directory (familiar to shell
+ The user's login (or "home") directory (familiar to shell
programmers as â$HOMEâ).
Login shell
The program that is run when the user logs in. This is usually a
shell, such as Bash.
- A few lines representative of âpwcatââs output are as follows:
+ A few lines representative of âpwcatâ's output are as follows:
$ pwcat
⣠root:x:0:1:Operator:/:/bin/sh
@@ -17724,7 +17703,7 @@ efficiency, as â_pw_init()â needs to be called only
once.
âpwcatâ, it first saves the values of âFSâ, âRSâ, and â$0â.
It notes in
the variable âusing_fwâ whether field splitting with âFIELDWIDTHSâ is
in
effect or not. Doing so is necessary, as these functions could be
-called from anywhere within a userâs program, and the user may have his
+called from anywhere within a user's program, and the user may have his
or her own way of splitting records and fields. This makes it possible
to restore the correct field-splitting mechanism later. The test can
only be true for âgawkâ. It is false if using âFSâ or âFPATâ, or
on
@@ -17784,8 +17763,8 @@ subsequent calls to âgetpwent()â start over again:
A conscious design decision in this suite is that each subroutine
calls â_pw_init()â to initialize the database arrays. The overhead of
running a separate process to generate the user database, and the I/O to
-scan it, are only incurred if the userâs main program actually calls one
-of these functions. If this library file is loaded along with a userâs
+scan it, are only incurred if the user's main program actually calls one
+of these functions. If this library file is loaded along with a user's
program, but none of the routines are ever called, then there is no
extra runtime overhead. (The alternative is move the body of
â_pw_init()â into a âBEGINâ rule, which always runs âpwcatâ. This
@@ -17819,7 +17798,7 @@ standard only provides a set of C library routines
(â<grp.h>â and
âgetgrent()â) for accessing the information. Even though this file may
exist, it may not have complete information. Therefore, as with the
user database, it is necessary to have a small C program that generates
-the group database as its output. âgrcatâ, a C program that âcatsâ the
+the group database as its output. âgrcatâ, a C program that "cats" the
group database, is as follows:
/*
@@ -17854,15 +17833,15 @@ group database, is as follows:
separated with colons and represent the following information:
Group Name
- The groupâs name.
+ The group's name.
Group Password
- The groupâs encrypted password. In practice, this field is never
+ The group's encrypted password. In practice, this field is never
used; it is usually empty or set to â*â.
Group ID Number
- The groupâs numeric group ID number; the association of name to
- number must be unique within the file. (On some systems itâs a C
+ The group's numeric group ID number; the association of name to
+ number must be unique within the file. (On some systems it's a C
âlongâ, and not an âintâ. Thus, we cast it to âlongâ for all
cases.)
@@ -18032,7 +18011,7 @@ body of â_gr_init()â into a âBEGINâ rule).
Most of the work is in scanning the database and building the various
associative arrays. The functions that the user calls are themselves
-very simple, relying on âawkââs associative arrays to do work.
+very simple, relying on âawkâ's associative arrays to do work.
The âidâ program in *note Id Program:: uses these functions.
@@ -18040,7 +18019,7 @@ very simple, relying on âawkââs associative
arrays to do work.
(1) There is a subtle problem with the code just presented. Suppose
that the first time there were no names. This code adds the names with
-a leading comma. It also doesnât check that there is a â$4â.
+a leading comma. It also doesn't check that there is a â$4â.
File: gawk.info, Node: Walking Arrays, Next: Library Functions Summary,
Prev: Group Functions, Up: Library Functions
@@ -18069,7 +18048,7 @@ representing the name of the array:
It works by looping over each element of the array. If any given
element is itself an array, the function calls itself recursively,
passing the subarray and a new string representing the current index.
-Otherwise, the function simply prints the elementâs name, index, and
+Otherwise, the function simply prints the element's name, index, and
value. Here is a main program to demonstrate:
BEGIN {
@@ -18159,8 +18138,8 @@ File: gawk.info, Node: Library Functions Summary,
Next: Library Exercises, Pr
are intended to serve that purpose.
⢠When writing general-purpose library functions, put some thought
- into how to name any global variables so that they wonât conflict
- with variables from a userâs program.
+ into how to name any global variables so that they won't conflict
+ with variables from a user's program.
⢠The functions presented here fit into the following categories:
@@ -18191,7 +18170,7 @@ File: gawk.info, Node: Library Exercises, Prev:
Library Functions Summary, Up
==============
1. In *note Empty Files::, we presented the âzerofile.awkâ program,
- which made use of âgawkââs âARGINDâ variable. Can this problem
be
+ which made use of âgawkâ's âARGINDâ variable. Can this problem be
solved without relying on âARGINDâ? If so, how?
2. As a related challenge, revise that code to handle the case where
@@ -18258,7 +18237,7 @@ you.
to replace the installed versions on your system. Nor may all of these
programs be fully compliant with the most recent POSIX standard. This
is not a problem; their purpose is to illustrate âawkâ language
-programming for âreal-worldâ tasks.
+programming for "real-world" tasks.
The programs are presented in alphabetical order.
@@ -18278,11 +18257,11 @@ File: gawk.info, Node: Cut Program, Next: Egrep
Program, Up: Clones
11.2.1 Cutting Out Fields and Columns
-------------------------------------
-The âcutâ utility selects, or âcuts,â characters or fields from its
+The âcutâ utility selects, or "cuts," characters or fields from its
standard input and sends them to its standard output. Fields are
separated by TABs by default, but you may supply a command-line option
to change the field âdelimiterâ (i.e., the field-separator character).
-âcutââs definition of fields is less general than âawkââs.
+âcutâ's definition of fields is less general than âawkâ's.
A common use of âcutâ might be to pull out just the login names of
logged-on users from the output of âwhoâ. For example, the following
@@ -18340,7 +18319,7 @@ supplied:
}
Next comes a âBEGINâ rule that parses the command-line options. It
-sets âFSâ to a single TAB character, because that is âcutââs default
+sets âFSâ to a single TAB character, because that is âcutâ's default
field separator. The rule then sets the output field separator to be
the same as the input field separator. A loop using âgetopt()â steps
through the command-line options. Exactly one of the variables
@@ -18380,11 +18359,11 @@ by characters, the output field separator is set to
the null string:
ARGV[i] = ""
The code must take special care when the field delimiter is a space.
-Using a single space (â" "â) for the value of âFSâ is
incorrectââawkâ
+Using a single space (â" "â) for the value of âFSâ is
incorrect--âawkâ
would separate fields with runs of spaces, TABs, and/or newlines, and we
want them to be separated with individual spaces. To this end, we save
the original space character in the variable âfsâ for later use; after
-setting âFSâ to â"[ ]"â we canât use it directly to see if the field
+setting âFSâ to â"[ ]"â we can't use it directly to see if the field
delimiter character is in the string.
Also remember that after âgetopt()â is through (as described in *note
@@ -18445,7 +18424,7 @@ splitting:
}
The âset_charlist()â function is more complicated than
-âset_fieldlist()â. The idea here is to use âgawkââs
âFIELDWIDTHSâ
+âset_fieldlist()â. The idea here is to use âgawkâ's âFIELDWIDTHSâ
variable (*note Constant Size::), which describes constant-width input.
When using a character list, that is exactly what we have.
@@ -18527,7 +18506,7 @@ out between the fields:
print ""
}
- This version of âcutâ relies on âgawkââs âFIELDWIDTHSâ
variable to do
+ This version of âcutâ relies on âgawkâ's âFIELDWIDTHSâ variable
to do
the character-based cutting. It is possible in other âawkâ
implementations to use âsubstr()â (*note String Functions::), but it is
also extremely painful. The âFIELDWIDTHSâ variable supplies an elegant
@@ -18549,7 +18528,7 @@ There was also âfgrepâ (Fast âgrepâ), which
searched for matches of one
more fixed strings.
POSIX chose to combine these three programs into one, simply named
-âgrepâ. On a POSIX system, âgrepââs default behavior is to search
using
+âgrepâ. On a POSIX system, âgrepâ's default behavior is to search
using
BREs. You use â-Eâ to specify the use of EREs, and â-Fâ to specify
searching for fixed strings.
@@ -18601,7 +18580,7 @@ line, each output line is preceded by the name of the
file and a colon.
having succeeded.
This version uses the âgetopt()â library function (*note Getopt
-Function::) and âgawkââs âBEGINFILEâ and âENDFILEâ special
patterns
+Function::) and âgawkâ's âBEGINFILEâ and âENDFILEâ special patterns
(*note BEGINFILE/ENDFILE::).
The program begins with descriptive comments and then a âBEGINâ rule
@@ -18651,15 +18630,15 @@ that processes the command-line arguments with
âgetopt()â. The â-iâ
}
Note the comment about invocation: Because several of the options
-overlap with âgawkââs, a â--â is needed to tell âgawkâ to stop
looking
+overlap with âgawkâ's, a â--â is needed to tell âgawkâ to stop
looking
for options.
Next comes the code that handles the âegrepâ-specific behavior.
âegrepâ uses the first nonoption on the command line if no pattern is
supplied with â-eâ. If the pattern is empty, that means no pattern was
-supplied, so itâs necessary to print an error message and exit. The
+supplied, so it's necessary to print an error message and exit. The
âawkâ command-line arguments up to âARGV[Optind]â are cleared, so that
-âawkâ wonât try to process them as files. If no files are specified,
+âawkâ won't try to process them as files. If no files are specified,
the standard input is used, and if multiple files are specified, we make
sure to note this so that the file names can precede the matched lines
in the output:
@@ -18686,7 +18665,7 @@ zero. âfcountâ tracks how many lines in the
current file matched the
pattern.
Here also is where we implement the â-sâ option. We check if
âERRNOâ
-has been set, and if â-sâ was supplied. In that case, itâs necessary to
+has been set, and if â-sâ was supplied. In that case, it's necessary to
move on to the next file. Otherwise âgawkâ would exit with an error:
BEGINFILE {
@@ -18792,8 +18771,8 @@ File: gawk.info, Node: Id Program, Next: Split
Program, Prev: Egrep Program,
11.2.3 Printing Out User Information
------------------------------------
-The âidâ utility lists a userâs real and effective user ID numbers, real
-and effective group ID numbers, and the userâs group set, if any. âidâ
+The âidâ utility lists a user's real and effective user ID numbers, real
+and effective group ID numbers, and the user's group set, if any. âidâ
only prints the effective user ID and group ID if they are different
from the real ones. If possible, âidâ also supplies the corresponding
user and group names. The output might look like this:
@@ -18801,12 +18780,12 @@ user and group names. The output might look like
this:
$ id
⣠uid=1000(arnold) gid=1000(arnold)
groups=1000(arnold),4(adm),7(lp),27(sudo)
- This information is part of what is provided by âgawkââs
âPROCINFOâ
+ This information is part of what is provided by âgawkâ's âPROCINFOâ
array (*note Built-in Variables::). However, the âidâ utility provides
a more palatable output than just individual numbers.
The POSIX version of âidâ takes several options that give you control
-over the outputâs format, such as printing only real ids, or printing
+over the output's format, such as printing only real ids, or printing
only numbers or only names. Additionally, you can print the information
for a specific user, instead of that of the current user.
@@ -18877,7 +18856,7 @@ more than one user name on the command line:
The user and group ID numbers are obtained from âPROCINFOâ for the
current user, or from the user and password databases for a user
supplied on the command line. In the latter case, âreal_ids_onlyâ is
-set, since itâs not possible to print information about the effective
+set, since it's not possible to print information about the effective
user and group IDs:
if (ARGC - Optind == 0) {
@@ -18896,7 +18875,7 @@ user and group IDs:
The test in the âforâ loop is worth noting. Any supplementary groups
in the âPROCINFOâ array have the indices â"group1"â through
â"groupN"â
for some N (i.e., the total number of supplementary groups). However,
-we donât know in advance how many of these groups there are.
+we don't know in advance how many of these groups there are.
This loop works by starting at one, concatenating the value with
â"group"â, and then using âinâ to see if that value is in the array
@@ -18904,7 +18883,7 @@ we donât know in advance how many of these groups
there are.
last group in the array and the loop exits.
The loop is also correct if there are _no_ supplementary groups; then
-the condition is false the first time itâs tested, and the loop body
+the condition is false the first time it's tested, and the loop body
never executes.
Now, based on the options, we decide what information to print. For
@@ -18969,8 +18948,8 @@ combined with â-râ and â-nâ:
exit 0
}
- At this point, we havenât exited yet, so we print the regular,
-default output, based either on the current userâs information, or that
+ At this point, we haven't exited yet, so we print the regular,
+default output, based either on the current user's information, or that
of the user whose name was provided on the command line. We start with
the real user ID:
@@ -18978,7 +18957,7 @@ the real user ID:
pw = getpwuid(uid)
print_first_field(pw)
- The âprint_first_field()â function prints the userâs login name from
+ The âprint_first_field()â function prints the user's login name from
the password file entry, surrounded by parentheses. It is shown soon.
Printing the effective user ID is next:
@@ -19044,7 +19023,7 @@ particular, moving the check for the empty string into
Finally, âfill_info_for_user()â fetches user, group, and group set
information for the user named on the command. The code is fairly
-straightforward, merely requiring that we exit if the given user doesnât
+straightforward, merely requiring that we exit if the given user doesn't
exist:
function fill_info_for_user(user,
@@ -19123,7 +19102,7 @@ character.(1)
The program begins with a standard descriptive comment and then a
âusage()â function describing the options. The variable âcommonâ keeps
-the functionâs lines short so that they look nice on the page:
+the function's lines short so that they look nice on the page:
# split.awk --- do split in awk
#
@@ -19207,10 +19186,10 @@ the way to âzzxâ, âzzyâ, and finally
âzzzâ. There are two important
aspects to this:
⢠We have to be able to easily generate these suffixes, and in
- particular easily handle ârolling overâ; for example, going from
+ particular easily handle "rolling over"; for example, going from
âabzâ to âacaâ.
- ⢠We have to tell when weâve finished with the last file, so that if
+ ⢠We have to tell when we've finished with the last file, so that if
we still have more input data we can print an error message and
exit. The trick is to handle this _after_ using the last suffix,
and not when the final suffix is created.
@@ -19232,16 +19211,16 @@ been used up. The logical steps are as follows:
2. Prepare the data structures for the next time âcompute_suffix()â is
called. To do this, we loop over âSuffix_indâ, _backwards_. If
- the current element is less than 26, itâs incremented and the loop
+ the current element is less than 26, it's incremented and the loop
breaks (âabqâ goes to âabrâ). Otherwise, the element is reset to
one and we move down the list (âabzâ to âacaâ). Thus, the
- âSuffix_indâ array is always âone step aheadâ of the actual file
+ âSuffix_indâ array is always "one step ahead" of the actual file
name suffix to be returned.
- 3. Check if weâve gone past the limit of possible file names. If
+ 3. Check if we've gone past the limit of possible file names. If
âReached_lastâ is true, print a message and exit. Otherwise, check
if âSuffix_indâ describes a suffix where all the letters are âzâ.
- If thatâs the case weâre about to return the final suffix. If so,
+ If that's the case we're about to return the final suffix. If so,
we set âReached_lastâ to true so that the _next_ call to
âcompute_suffix()â will cause a failure.
@@ -19305,7 +19284,7 @@ mutually exclusive, we simply use two separate rules,
one for when
greater than zero.
The variable âtcountâ counts how many lines have been processed so
-far. When it exceeds âLine_countâ, itâs time to close the previous file
+far. When it exceeds âLine_countâ, it's time to close the previous file
and switch to a new one:
Line_count > 0 {
@@ -19355,7 +19334,7 @@ new file. The logic here does all that:
---------- Footnotes ----------
- (1) Using â-bâ twice requires separating âgawkââs options from
those
+ (1) Using â-bâ twice requires separating âgawkâ's options from those
of the program. For example: âgawk -f getopt.awk -f split.awk -b -- -b
42m large-file.txt split-â.
@@ -19365,7 +19344,7 @@ File: gawk.info, Node: Tee Program, Next: Uniq
Program, Prev: Split Program,
11.2.5 Duplicating Output into Multiple Files
---------------------------------------------
-The âteeâ program is known as a âpipe fitting.â âteeâ copies its
+The âteeâ program is known as a "pipe fitting." âteeâ copies its
standard input to its standard output and also duplicates it to the
files named on the command line. Its usage is as follows:
@@ -19453,8 +19432,8 @@ File: gawk.info, Node: Uniq Program, Next: Wc
Program, Prev: Tee Program, Up
The âuniqâ utility reads sorted lines of data on its standard input, and
by default removes duplicate lines. In other words, it only prints
-unique linesâhence the name. âuniqâ has a number of options. The usage
-is as follows:
+unique lines--hence the name. âuniqâ has a number of options. The
+usage is as follows:
âuniqâ [â-udcâ [â-f Nâ] [â-s Nâ]] [INPUTFILE [OUTPUTFILE]]
@@ -19472,7 +19451,7 @@ is as follows:
â-f Nâ
Skip N fields before comparing lines. The definition of fields is
- similar to âawkââs default: nonwhitespace characters separated by
+ similar to âawkâ's default: nonwhitespace characters separated by
runs of spaces and/or TABs.
â-s Nâ
@@ -19614,7 +19593,7 @@ to â$0â, so that subsequent lines of text have
something to be compared
to.
The second rule does the work. The variable âequalâ is one or zero,
-depending upon the results of âare_equal()ââs comparison. If âuniqâ
is
+depending upon the results of âare_equal()â's comparison. If âuniqâ is
counting repeated lines, and the lines are equal, then it increments the
âcountâ variable. Otherwise, it prints the line and resets âcountâ,
because the two lines are not equal.
@@ -19702,7 +19681,7 @@ punctuation and control characters.
ASCII is a pure subset). Unicode provides tens of thousands of unique
characters (called âcode pointsâ) to cover most existing human languages
(living and dead) and a number of nonhuman ones as well (such as Klingon
-and J.R.R. Tolkienâs elvish languages).
+and J.R.R. Tolkien's elvish languages).
To save space in files, Unicode code points are âencodedâ, where each
character takes from one to four bytes in the file. UTF-8 is possibly
@@ -19730,7 +19709,7 @@ Loadable extensions are presented in full detail in
*note Dynamic
Extensions::. They provide a way to add functions to âgawkâ which can
call out to other facilities written in C or C++.
- For the purposes of âwc.awkâ, itâs enough to know that the extension
+ For the purposes of âwc.awkâ, it's enough to know that the extension
is loaded with the â@loadâ directive, and the additional function we
will use is called âmbs_length()â. This function returns the number of
bytes in a string, not the number of characters.
@@ -19755,7 +19734,7 @@ follows:
â-câ
Count only bytes. Once upon a time, the âcâ in this option stood
- for âcharacters.â But, as explained earlier, bytes and character
+ for "characters." But, as explained earlier, bytes and character
are no longer synonymous with each other.
â-lâ
@@ -19765,7 +19744,7 @@ follows:
Count only characters.
â-wâ
- Count only words. A âwordâ is a contiguous sequence of
+ Count only words. A "word" is a contiguous sequence of
nonwhitespace characters, separated by spaces and/or TABs.
Luckily, this is the normal way âawkâ separates fields in its input
data.
@@ -19837,7 +19816,7 @@ name in âfnameâ:
fname = FILENAME
}
- The âendfile()â function adds the current fileâs numbers to the
+ The âendfile()â function adds the current file's numbers to the
running totals of lines, words, and characters. It then prints out
those numbers for the file that was just read. It relies on
âbeginfile()â to reset the numbers for the following data file:
@@ -19866,7 +19845,7 @@ is needed because the newline character separating
records (the value of
length. Similarly, it adds the length of the record in bytes, plus one,
to âbytesâ. Next, âlinesâ is incremented for each line read, and
âwordsâ is incremented by the value of âNFâ, which is the number of
-âwordsâ on this line:
+"words" on this line:
# do per line
{
@@ -19898,7 +19877,7 @@ File: gawk.info, Node: Miscellaneous Programs, Next:
Programs Summary, Prev:
11.3 A Grab Bag of âawkâ Programs
=================================
-This minor node is a large âgrab bagâ of miscellaneous programs. We
+This minor node is a large "grab bag" of miscellaneous programs. We
hope you find them both interesting and enjoyable.
* Menu:
@@ -19927,7 +19906,7 @@ File: gawk.info, Node: Dupword Program, Next: Alarm
Program, Up: Miscellaneou
A common error when writing large amounts of prose is to accidentally
duplicate words. Typically you will see this in text as something like
-âthe the program does the following...â When the text is online, often
+"the the program does the following..." When the text is online, often
the duplicated words occur at the end of one line and at the beginning
of another, making them very difficult to spot.
@@ -19937,11 +19916,11 @@ last word on a line (in the variable âprevâ) for
comparison with the
first word on the next line.
The first two statements make sure that the line is all lowercase, so
-that, for example, âTheâ and âtheâ compare equal to each other. The
+that, for example, "The" and "the" compare equal to each other. The
next statement replaces nonalphanumeric and nonwhitespace characters
with spaces, so that punctuation does not affect the comparison either.
The characters are replaced with spaces so that formatting controls
-donât create nonsense words (e.g., the Texinfo â@code{NF}â becomes
+don't create nonsense words (e.g., the Texinfo â@code{NF}â becomes
âcodeNFâ if punctuation is simply deleted). The record is then resplit
into fields, yielding just the actual words on the line, and ensuring
that there are no empty fields.
@@ -19974,11 +19953,11 @@ File: gawk.info, Node: Alarm Program, Next:
Translate Program, Prev: Dupword
-----------------------------
Nothing cures insomnia like a ringing alarm clock.
- â _Arnold Robbins_
+ -- _Arnold Robbins_
Sleep is for web developers.
- â _Erik Quanstrom_
+ -- _Erik Quanstrom_
- The following program is a simple âalarm clockâ program. You give it
+ The following program is a simple "alarm clock" program. You give it
a time of day and an optional message. At the specified time, it prints
the message on the standard output. In addition, you can give it the
number of times to repeat the message as well as a delay between
@@ -19990,7 +19969,7 @@ Getlocaltime Function::.
All the work is done in the âBEGINâ rule. The first part is argument
checking and setting of defaults: the delay, the count, and the message
to print. If the user supplied a message without the ASCII BEL
-character (known as the âalertâ character, â"\a"â), then it is added to
+character (known as the "alert" character, â"\a"â), then it is added to
the message. (On many systems, printing the ASCII BEL generates an
audible alert. Thus, when the alarm goes off, the system calls
attention to itself in case the user is not looking at the computer.)
@@ -20116,9 +20095,9 @@ processing:
the first character in the first list is replaced with the first
character in the second list, the second character in the first list is
replaced with the second character in the second list, and so on. If
-there are more characters in the âfromâ list than in the âtoâ list, the
-last character of the âtoâ list is used for the remaining characters in
-the âfromâ list.
+there are more characters in the "from" list than in the "to" list, the
+last character of the "to" list is used for the remaining characters in
+the "from" list.
Once upon a time, a user proposed adding a transliteration function
to âgawkâ. The following program was written to prove that character
@@ -20142,7 +20121,7 @@ functions. The first, âstranslate()â, takes three
arguments:
The string on which to do the translation
Associative arrays make the translation part fairly easy. ât_arâ
-holds the âtoâ characters, indexed by the âfromâ characters. Then a
+holds the "to" characters, indexed by the "from" characters. Then a
simple loop goes through âfromâ, one character at a time. For each
character in âfromâ, if the character appears in âtargetâ, it is
replaced with the corresponding âtoâ character.
@@ -20214,7 +20193,7 @@ alone.
An obvious improvement to this program would be to set up the ât_arâ
array only once, in a âBEGINâ rule. However, this assumes that the
-âfromâ and âtoâ lists will never change throughout the lifetime of the
+"from" and "to" lists will never change throughout the lifetime of the
program.
Another obvious improvement is to enable the use of ranges, such as
@@ -20234,13 +20213,13 @@ File: gawk.info, Node: Labels Program, Next: Word
Sorting, Prev: Translate Pr
11.3.4 Printing Mailing Labels
------------------------------
-Here is a âreal-worldâ(1) program. This script reads lists of names and
+Here is a "real-world"(1) program. This script reads lists of names and
addresses and generates mailing labels. Each page of labels has 20
labels on it, two across and 10 down. The addresses are guaranteed to
be no more than five lines of data. Each address is separated from the
next by a blank line.
- The basic idea is to read 20 labelsâ worth of data. Each line of
+ The basic idea is to read 20 labels' worth of data. Each line of
each label is stored in the âlineâ array. The single rule takes care of
filling the âlineâ array and printing the page when 20 labels have been
read.
@@ -20331,8 +20310,8 @@ not have been an even multiple of 20 labels in the data:
---------- Footnotes ----------
- (1) âReal worldâ is defined as âa program actually used to get
-something done.â
+ (1) "Real world" is defined as "a program actually used to get
+something done."
File: gawk.info, Node: Word Sorting, Next: History Sorting, Prev: Labels
Program, Up: Miscellaneous Programs
@@ -20361,8 +20340,8 @@ useful format.
printf "%s\t%d\n", word, freq[word]
}
- The program relies on âawkââs default field-splitting mechanism to
-break each line up into âwordsâ and uses an associative array named
+ The program relies on âawkâ's default field-splitting mechanism to
+break each line up into "words" and uses an associative array named
âfreqâ, indexed by each word, to count the number of times the word
occurs. In the âENDâ rule, it prints the counts.
@@ -20370,17 +20349,17 @@ occurs. In the âENDâ rule, it prints the counts.
on real text files:
⢠The âawkâ language considers upper- and lowercase characters to be
- distinct. Therefore, âbartenderâ and âBartenderâ are not treated
+ distinct. Therefore, "bartender" and "Bartender" are not treated
as the same word. This is undesirable, because words are
capitalized if they begin sentences in normal text, and a frequency
analyzer should not be sensitive to capitalization.
⢠Words are detected using the âawkâ convention that fields are
separated just by whitespace. Other characters in the input
- (except newlines) donât have any special meaning to âawkâ. This
+ (except newlines) don't have any special meaning to âawkâ. This
means that punctuation characters count as part of words.
- ⢠The output does not come out in any useful order. Youâre more
+ ⢠The output does not come out in any useful order. You're more
likely to be interested in which words occur most frequently or in
having an alphabetized table of how frequently each word occurs.
@@ -20418,7 +20397,7 @@ produces a table of the words appearing in âfile1â
in order of
decreasing frequency.
The âawkâ program suitably massages the data and produces a word
-frequency table, which is not ordered. The âawkâ scriptâs output is
+frequency table, which is not ordered. The âawkâ script's output is
then sorted by the âsortâ utility and printed on the screen.
The options given to âsortâ specify a sort that uses the second field
@@ -20497,7 +20476,7 @@ too obscure:
awk '! seen[$0]++'
-This version uses the expression as a pattern, relying on âawkââs
+This version uses the expression as a pattern, relying on âawkâ's
default action of printing the line when the pattern is true.
@@ -20513,7 +20492,7 @@ hand. Here we present a program that can extract parts
of a Texinfo
input file into separate files.
This Info file is written in Texinfo
-(https://www.gnu.org/software/texinfo/), the GNU Projectâs document
+(https://www.gnu.org/software/texinfo/), the GNU Project's document
formatting language. A single Texinfo source file can be used to
produce both printed documentation, with TeX, and online documentation.
(The Texinfo language is described fully, starting with *note Texinfo:
@@ -20522,7 +20501,7 @@ produce both printed documentation, with TeX, and
online documentation.
For our purposes, it is enough to know three things about Texinfo
input files:
- ⢠The âatâ symbol (â@â) is special in Texinfo, much as the
backslash
+ ⢠The "at" symbol (â@â) is special in Texinfo, much as the backslash
(â\â) is in C or âawkâ. Literal â@â symbols are represented
in
Texinfo source files as â@@â.
@@ -20532,7 +20511,7 @@ input files:
⢠Lines containing â@groupâ and â@end groupâ commands bracket
example
text that should not be split across a page boundary.
- (Unfortunately, TeX isnât always smart enough to do things exactly
+ (Unfortunately, TeX isn't always smart enough to do things exactly
right, so we have to give it some help.)
The following program, âextract.awkâ, reads through a Texinfo source
@@ -20573,7 +20552,7 @@ looks something like this:
...
âextract.awkâ begins by setting âIGNORECASEâ to one, so that mixed
-upper- and lowercase letters in the directives wonât matter.
+upper- and lowercase letters in the directives won't matter.
The first rule handles calling âsystem()â, checking that a command is
given (âNFâ is at least three) and also checking that the command exits
@@ -20611,7 +20590,7 @@ simple.
The âforâ loop does the work. It reads lines using âgetlineâ (*note
Getline::). For an unexpected end-of-file, it calls the
-âunexpected_eof()â function. If the line is an âendfileâ line, then it
+âunexpected_eof()â function. If the line is an "endfile" line, then it
breaks out of the loop. If the line is an â@groupâ or â@end groupâ
line, then it ignores it and goes on to the next line. Similarly,
comments within examples are also ignored.
@@ -20717,7 +20696,7 @@ middle of a pipeline:
Here, âs/old/new/gâ tells âsedâ to look for the regexp âoldâ on
each
input line and globally replace it with the text ânewâ (i.e., all the
-occurrences on a line). This is similar to âawkââs âgsub()â function
+occurrences on a line). This is similar to âawkâ's âgsub()â function
(*note String Functions::).
The following program, âawksed.awkâ, accepts at least two
@@ -20754,7 +20733,7 @@ process. If none are provided, the standard input is
used:
print
}
- The program relies on âgawkââs ability to have âRSâ be a regexp,
as
+ The program relies on âgawkâ's ability to have âRSâ be a regexp, as
well as on the setting of âRTâ to the actual text that terminates the
record (*note Records::).
@@ -20765,7 +20744,7 @@ to the replacement text, a simple âprintâ statement
outputs the text we
want to keep, followed by the replacement text.
There is one wrinkle to this scheme, which is what to do if the last
-record doesnât end with text that matches âRSâ. Using a âprintâ
+record doesn't end with text that matches âRSâ. Using a âprintâ
statement unconditionally prints the replacement text, which is not
correct. However, if the file did not end in text that matches âRSâ,
âRTâ is set to the null string. In this case, we can print â$0â using
@@ -20815,21 +20794,21 @@ to be able to write programs in the following manner:
}
The following program, âigawk.shâ, provides this service. It
-simulates âgawkââs searching of the âAWKPATHâ variable and also
allows
+simulates âgawkâ's searching of the âAWKPATHâ variable and also allows
ânestedâ includes (i.e., a file that is included with â@includeâ can
contain further â@includeâ statements). âigawkâ makes an effort to
only
-include files once, so that nested includes donât accidentally include a
+include files once, so that nested includes don't accidentally include a
library function twice.
âigawkâ should behave just like âgawkâ externally. This means it
-should accept all of âgawkââs command-line arguments, including the
+should accept all of âgawkâ's command-line arguments, including the
ability to have multiple source files specified via â-fâ and the ability
to mix command-line and library source files.
The program is written using the POSIX Shell (âshâ) command
language.(1) It works as follows:
- 1. Loop through the arguments, saving anything that doesnât represent
+ 1. Loop through the arguments, saving anything that doesn't represent
âawkâ source code for later, when the expanded program is run.
2. For any arguments that do represent âawkâ text, put the arguments
@@ -20839,12 +20818,12 @@ language.(1) It works as follows:
just appended directly.
b. Source file names, provided with â-fâ. We use a neat trick
- and append â@include FILENAMEâ to the shell variableâs
+ and append â@include FILENAMEâ to the shell variable's
contents. Because the file-inclusion program works the way
âgawkâ does, this gets the text of the file included in the
program at the correct point.
- 3. Run an âawkâ program (naturally) over the shell variableâs contents
+ 3. Run an âawkâ program (naturally) over the shell variable's contents
to expand â@includeâ statements. The expanded program is placed in
a second shell variable.
@@ -20854,7 +20833,7 @@ language.(1) It works as follows:
This program uses shell variables extensively: for storing
command-line arguments and the text of the âawkâ program that will
-expand the userâs program, for the userâs original program, and for the
+expand the user's program, for the user's original program, and for the
expanded program. Doing so removes some potential problems that might
arise were we to use temporary files instead, at the cost of making the
script somewhat more complicated.
@@ -20867,13 +20846,13 @@ are several cases of interest:
â--â
This ends the arguments to âigawkâ. Anything else should be passed
- on to the userâs âawkâ program without being evaluated.
+ on to the user's âawkâ program without being evaluated.
â-Wâ
This indicates that the next option is specific to âgawkâ. To make
argument processing easier, the â-Wâ is appended to the front of
the remaining arguments and the loop continues. (This is an âshâ
- programming trick. Donât worry about it if you are not familiar
+ programming trick. Don't worry about it if you are not familiar
with âshâ.)
â-vâ, â-Fâ
@@ -20983,17 +20962,17 @@ the original âawkâ program.
The âawkâ program to process â@includeâ directives is stored in the
shell variable âexpand_progâ. Doing this keeps the shell script
-readable. The âawkâ program reads through the userâs program, one line
+readable. The âawkâ program reads through the user's program, one line
at a time, using âgetlineâ (*note Getline::). The input file names and
â@includeâ statements are managed using a stack. As each â@includeâ is
-encountered, the current file name is âpushedâ onto the stack and the
+encountered, the current file name is "pushed" onto the stack and the
file named in the â@includeâ directive becomes the current file name.
-As each file is finished, the stack is âpopped,â and the previous input
+As each file is finished, the stack is "popped," and the previous input
file becomes the current input file again. The process is started by
making the original file the first one on the stack.
The âpathto()â function does the work of finding the full path to a
-file. It simulates âgawkââs behavior when searching the âAWKPATHâ
+file. It simulates âgawkâ's behavior when searching the âAWKPATHâ
environment variable (*note AWKPATH Variable::). If a file name has a
â/â in it, no path search is done. Similarly, if the file name is
â"-"â, then that string is used as-is. Otherwise, the file name is
@@ -21098,12 +21077,12 @@ command line. Because the result is used in a
variable assignment, it
is saved as a single string, even if the results contain whitespace.
The expanded program is saved in the variable âprocessed_programâ.
-Itâs done in these steps:
+It's done in these steps:
1. Run âgawkâ with the â@includeâ-processing program (the value of
the
âexpand_progâ shell variable) reading standard input.
- 2. Standard input is the contents of the userâs program, from the
+ 2. Standard input is the contents of the user's program, from the
shell variable âprogramâ. Feed its contents to âgawkâ via a here
document.
@@ -21115,7 +21094,7 @@ the original options and command-line arguments that
the user supplied:
eval gawk $opts -- '"$processed_program"' '"$@"'
- The âevalâ command is a shell construct that reruns the shellâs
+ The âevalâ command is a shell construct that reruns the shell's
parsing process. This keeps things properly quoted.
This version of âigawkâ represents the fifth version of this program.
@@ -21126,7 +21105,7 @@ There are four key simplifications that make the
program work better:
â@includeâ processing can be done once.
⢠Not trying to save the line read with âgetlineâ in the
âpathto()â
- function when testing for the fileâs accessibility for use with the
+ function when testing for the file's accessibility for use with the
main program simplifies things considerably.
⢠Using a âgetlineâ loop in the âBEGINâ rule does it all in one
@@ -21137,7 +21116,7 @@ There are four key simplifications that make the
program work better:
it in a shell variable avoids some potential security problems.
This has the disadvantage that the script relies upon more features
of the âshâ language, making it harder to follow for those who
- arenât familiar with âshâ.
+ aren't familiar with âshâ.
Also, this program illustrates that it is often worthwhile to combine
âshâ and âawkâ programming together. You can usually accomplish quite
a
@@ -21150,8 +21129,8 @@ features to a program; they can often be layered on
top.(3)
Before âgawkâ acquired its built-in â@includeâ mechanism,
âigawkâ and
its manual page were installed as part of the regular âgawkâ
-installation (âmake installâ). This is no longer done, because itâs no
-longer necessary. But weâve kept the program in this Info file for its
+installation (âmake installâ). This is no longer done, because it's no
+longer necessary. But we've kept the program in this Info file for its
educational value.
---------- Footnotes ----------
@@ -21175,9 +21154,9 @@ File: gawk.info, Node: Anagram Program, Next:
Signature Program, Prev: Igawk
An interesting programming challenge is to search for âanagramsâ in a
word list (such as â/usr/share/dict/wordsâ on many GNU/Linux systems).
One word is an anagram of another if both words contain the same letters
-(e.g., âbabblingâ and âblabbingâ).
+(e.g., "babbling" and "blabbing").
- Column 2, Problem C, of Jon Bentleyâs âProgramming Pearlsâ, Second
+ Column 2, Problem C, of Jon Bentley's âProgramming Pearlsâ, Second
Edition, presents an elegant algorithm. The idea is to give words that
are anagrams a common signature, sort all the words together by their
signatures, and then print them. Dr. Bentley observes that taking the
@@ -21281,7 +21260,7 @@ supplies the following copyright terms:
O+X*(o*(o+O)+O),+x+O+X*o,x*(x-o),(o+X+x)*o*o-(x-O-O),O+(X-x)*(X+O),x-O}'
We leave it to you to determine what the program does. (If you are
-truly desperate to understand it, see Chris Johansenâs explanation,
+truly desperate to understand it, see Chris Johansen's explanation,
which is embedded in the Texinfo source file for this Info file.)
@@ -21297,11 +21276,11 @@ File: gawk.info, Node: Programs Summary, Next:
Programs Exercises, Prev: Misc
easier to use. Otherwise, invoke the program using âawk -f ...â.
⢠Reimplementing standard POSIX programs in âawkâ is a pleasant
- exercise; âawkââs expressive power lets you write such programs in
+ exercise; âawkâ's expressive power lets you write such programs in
relatively few lines of code, yet they are functionally complete
and usable.
- ⢠One of standard âawkââs weaknesses is working with individual
+ ⢠One of standard âawkâ's weaknesses is working with individual
characters. The ability to use âsplit()â with the empty string as
the separator can considerably simplify such tasks.
@@ -21334,22 +21313,22 @@ File: gawk.info, Node: Programs Exercises, Prev:
Programs Summary, Up: Sample
way.
4. The âsplit.awkâ program (*note Split Program::) assumes that
- letters are contiguous in the character set, which isnât true for
+ letters are contiguous in the character set, which isn't true for
EBCDIC systems. Fix this problem. (Hint: Consider a different way
to work through the alphabet, without relying on âord()â and
âchr()â.)
5. In âuniq.awkâ (*note Uniq Program::, the logic for choosing which
- lines to print represents a âstate machineâ, which is âa device
+ lines to print represents a âstate machineâ, which is "a device
which can be in one of a set number of stable conditions depending
on its previous condition and on the present values of its
- inputs.â(1) Brian Kernighan suggests that âan alternative approach
+ inputs."(1) Brian Kernighan suggests that "an alternative approach
to state machines is to just read the input into an array, then use
- indexing. Itâs almost always easier code, and for most inputs
- where you would use this, just as fast.â Rewrite the logic to
+ indexing. It's almost always easier code, and for most inputs
+ where you would use this, just as fast." Rewrite the logic to
follow this suggestion.
- 6. Why canât the âwc.awkâ program (*note Wc Program::) just use the
+ 6. Why can't the âwc.awkâ program (*note Wc Program::) just use the
value of âFNRâ in âendfile()â? Hint: Examine the code in *note
Filetrans Function::.
@@ -21379,7 +21358,7 @@ File: gawk.info, Node: Programs Exercises, Prev:
Programs Summary, Up: Sample
11. In *note Igawk Program::, we mentioned that not trying to save the
line read with âgetlineâ in the âpathto()â function when testing
- for the fileâs accessibility for use with the main program
+ for the file's accessibility for use with the main program
simplifies things considerably. What problem does this engender
though?
@@ -21421,20 +21400,20 @@ File: gawk.info, Node: Advanced Features, Next:
Internationalization, Prev: S
Write documentation as if whoever reads it is a violent psychopath
who knows where you live.
- â _Steve English, as quoted by Peter Langston_
+ -- _Steve English, as quoted by Peter Langston_
- This major node discusses advanced features in âgawkâ. Itâs a bit of
-a âgrab bagâ of items that are otherwise unrelated to each other.
+ This major node discusses advanced features in âgawkâ. It's a bit of
+a "grab bag" of items that are otherwise unrelated to each other.
First, we look at a command-line option that allows âgawkâ to recognize
nondecimal numbers in input data, not just in âawkâ programs. Then,
-âgawkââs special features for sorting arrays are presented. Next,
+âgawkâ's special features for sorting arrays are presented. Next,
two-way I/O, discussed briefly in earlier parts of this Info file, is
described in full detail, along with the basics of TCP/IP networking.
We then see how âgawkâ can âprofileâ an âawkâ program, making it
possible to tune it for performance. Next, we present an experimental
feature that allows you to preserve the values of âawkâ variables and
arrays between runs of âgawkâ. Finally, we discuss the philosophy
-behind âgawkââs extension mechanism.
+behind âgawkâ's extension mechanism.
Additional advanced features are discussed in separate major nodes of
their own:
@@ -21443,7 +21422,7 @@ their own:
your âawkâ programs, so that they can speak multiple national
languages.
- ⢠*note Debugger::, describes âgawkââs built-in command-line
debugger
+ ⢠*note Debugger::, describes âgawkâ's built-in command-line debugger
for debugging âawkâ programs.
⢠*note Arbitrary Precision Arithmetic::, describes how you can use
@@ -21517,9 +21496,9 @@ File: gawk.info, Node: Boolean Typed Values, Next:
Array Sorting, Prev: Nonde
Scalar values in âawkâ are either numbers or strings. âgawkâ also
supports values of type âregexpâ (*note Strong Regexp Constants::).
- As described in *note Truth Values::, Boolean values in âawkâ donât
-have a separate type: a value counts as âtrueâ if it is nonzero or
-non-null, and as âfalseâ otherwise.
+ As described in *note Truth Values::, Boolean values in âawkâ don't
+have a separate type: a value counts as "true" if it is nonzero or
+non-null, and as "false" otherwise.
When interchanging data with languages that do have a real Boolean
type, using a standard format such as JSON or XML, the lack of a true
@@ -21527,9 +21506,9 @@ Boolean type in âawkâ is problematic. (See, for
example, the âjsonâ
extension provided by the âgawkextlibâ project
(https://sourceforge.net/projects/gawkextlib).)
- Itâs easy to import Boolean data into âawkâ, but then the fact that
+ It's easy to import Boolean data into âawkâ, but then the fact that
it was originally Boolean is lost. Exporting data is even harder;
-thereâs no way to indicate that a value is really Boolean.
+there's no way to indicate that a value is really Boolean.
To solve this problem, âgawkâ provides a function named âmkbool()â.
It takes one argument, which is any âawkâ expression, and it returns a
@@ -21548,7 +21527,7 @@ desired.
While it would have been possible to add two new built-in variables
of Boolean type named âTRUEâ and âFALSEâ, doing so would undoubtedly
-have broken many existing âawkâ programs. Instead, having a
âgeneratorâ
+have broken many existing âawkâ programs. Instead, having a "generator"
function that creates Boolean values gives flexibility, without breaking
as much existing code.
@@ -21732,7 +21711,7 @@ specific field position and can be used for this
purpose:
}
}
- The first field in each entry of the password file is the userâs
+ The first field in each entry of the password file is the user's
login name, and the fields are separated by colons. Each record defines
a subarray, with each field as an element in the subarray. Running the
program produces the following output:
@@ -21787,7 +21766,7 @@ traversal, and the sky is really the limit when it
comes to designing
such a function.
When string comparisons are made during a sort, either for element
-values where one or both arenât numbers, or for element indices handled
+values where one or both aren't numbers, or for element indices handled
as strings, the value of âIGNORECASEâ (*note Built-in Variables::)
controls whether the comparisons treat corresponding upper- and
lowercase letters as equivalent or distinct.
@@ -21818,7 +21797,7 @@ File: gawk.info, Node: Array Sorting Functions, Prev:
Controlling Array Traver
In most âawkâ implementations, sorting an array requires writing a
âsort()â function. This can be educational for exploring different
-sorting algorithms, but usually thatâs not the point of the program.
+sorting algorithms, but usually that's not the point of the program.
âgawkâ provides the built-in âasort()â and âasorti()â functions
(*note
String Functions::) for sorting arrays. For example:
@@ -21829,13 +21808,13 @@ String Functions::) for sorting arrays. For example:
After the call to âasort()â, the array âdataâ is indexed from 1 to
some number N, the total number of elements in âdataâ. (This count is
-âasort()ââs return value.) âdata[1]â <= âdata[2]â <=
âdata[3]â, and so
+âasort()â's return value.) âdata[1]â <= âdata[2]â <=
âdata[3]â, and so
on. The default comparison is based on the type of the elements (*note
Typing and Comparison::). All numeric values come before all string
values, which in turn come before all subarrays.
- An important side effect of calling âasort()â is that _the arrayâs
-original indices are irrevocably lost_. As this isnât always desirable,
+ An important side effect of calling âasort()â is that _the array's
+original indices are irrevocably lost_. As this isn't always desirable,
âasort()â accepts a second argument:
POPULATE THE ARRAY source
@@ -21847,7 +21826,7 @@ original indices are irrevocably lost_. As this
isnât always desirable,
and then sorts âdestâ, destroying its indices. However, the âsourceâ
array is not affected.
- Often, whatâs needed is to sort on the values of the _indices_
+ Often, what's needed is to sort on the values of the _indices_
instead of the values of the elements. To do that, use the âasorti()â
function. The interface and behavior are identical to that of
âasort()â, except that the index values are used for sorting and become
@@ -21887,20 +21866,20 @@ order and uses them to fill in the result array,
whereas âasorti()â
takes the _indices_ in their final order and uses them to fill in the
result array.
- NOTE: Copying array indices and elements isnât expensive in terms
+ NOTE: Copying array indices and elements isn't expensive in terms
of memory. Internally, âgawkâ maintains âreference countsâ to
data. For example, when âasort()â copies the first array to the
- second one, there is only one copy of the original array elementsâ
+ second one, there is only one copy of the original array elements'
data, even though both arrays use the values.
You may use the same array for both the first and second arguments to
âasort()â and âasorti()â. Doing so only makes sense if you are also
-supplying the third argument, since âawkâ doesnât provide a way to pass
+supplying the third argument, since âawkâ doesn't provide a way to pass
that third argument without also passing the first and second ones.
Because âIGNORECASEâ affects string comparisons, the value of
âIGNORECASEâ also affects sorting for both âasort()â and
âasorti()â.
-Note also that the localeâs sorting order does _not_ come into play;
+Note also that the locale's sorting order does _not_ come into play;
comparisons are based on character values only.(1)
The following example demonstrates the use of a comparison function
@@ -21949,7 +21928,7 @@ both values to lowercase in order to compare them
ignoring case.
⣠A a B b c C D d e E F f g G H h i I J j k K l L M m
⣠n N O o p P Q q r R S s t T u U V v w W X x y Y z Z
- NOTE: âUnder the hood,â âgawkâ uses the C library âqsort()â
+ NOTE: "Under the hood," âgawkâ uses the C library âqsort()â
function to manage the sorting. âqsort()â can call itself
recursively. This means that when you write a comparison function,
you should be careful to avoid the use of global variables and
@@ -22005,22 +21984,22 @@ in parallel with âgawkâ. The two-way connection
is created using the
The first time an I/O operation is executed using the â|&â operator,
âgawkâ creates a two-way pipeline to a child process that runs the other
program. Output created with âprintâ or âprintfâ is written to the
-programâs standard input, and output from the programâs standard output
+program's standard input, and output from the program's standard output
can be read by the âgawkâ program using âgetlineâ. As is the case with
processes started by â|â, the subprogram can be any program, or pipeline
of programs, that can be started by the shell.
There are some cautionary items to be aware of:
- ⢠As the code inside âgawkâ currently stands, the coprocessâs
- standard error goes to the same place that the parent âgawkââs
- standard error goes. It is not possible to read the childâs
+ ⢠As the code inside âgawkâ currently stands, the coprocess's
+ standard error goes to the same place that the parent âgawkâ's
+ standard error goes. It is not possible to read the child's
standard error separately.
⢠I/O buffering may be a problem. âgawkâ automatically flushes all
output down the pipe to the coprocess. However, if the coprocess
does not flush its output, âgawkâ may hang when doing a âgetlineâ
- in order to read the coprocessâs results. This could lead to a
+ in order to read the coprocess's results. This could lead to a
situation known as âdeadlockâ, where each process is waiting for
the other one to do something.
@@ -22061,7 +22040,7 @@ the coprocess and exits.
As a side note, the assignment âLC_ALL=Câ in the âsortâ command
ensures traditional Unix (ASCII) sorting from âsortâ. This is not
-strictly necessary here, but itâs good to know how to do this.
+strictly necessary here, but it's good to know how to do this.
Be careful when closing the â"from"â end of a two-way pipe; in this
case âgawkâ waits for the child process to exit, which may cause your
@@ -22088,7 +22067,7 @@ Auto-set::), like so:
print ... |& command # start two-way pipe
...
-If your system does not have ptys, or if all the systemâs ptys are in
+If your system does not have ptys, or if all the system's ptys are in
use, âgawkâ automatically falls back to using regular pipes.
Using ptys usually avoids the buffer deadlock issues described
@@ -22104,9 +22083,9 @@ driver and not passed through.
CAUTION: Finally, coprocesses open up the possibility of âdeadlockâ
between âgawkâ and the program running in the coprocess. This can
- occur if you send âtoo muchâ data to the coprocess before reading
+ occur if you send "too much" data to the coprocess before reading
any back; each process is blocked writing data with no one
- available to read what theyâve already written. There is no
+ available to read what they've already written. There is no
workaround for deadlock; careful programming and knowledge of the
behavior of the coprocess are required.
@@ -22114,7 +22093,7 @@ driver and not passed through.
ptys can help deal with buffering deadlocks.
Suppose âgawkâ were unable to add numbers. You could use a coprocess
-to do it. Hereâs an exceedingly simple program written for that
+to do it. Here's an exceedingly simple program written for that
purpose:
$ cat add.c
@@ -22167,10 +22146,10 @@ File: gawk.info, Node: TCP/IP Networking, Next:
Profiling, Prev: Two-way I/O,
âEMREDâ:
A host is a host from coast to coast,
- and nobody talks to a host thatâs close,
- unless the host that isnât close
+ and nobody talks to a host that's close,
+ unless the host that isn't close
is busy, hung, or dead.
- â _Mike OâBrien (aka Mr. Protocol)_
+ -- _Mike O'Brien (aka Mr. Protocol)_
In addition to being able to open a two-way pipeline to a coprocess
on the same system (*note Two-way I/O::), it is possible to make a
@@ -22211,7 +22190,7 @@ REMOTE-HOST
REMOTE-PORT
The TCP or UDP port number to use on the given REMOTE-HOST. Again,
- use â0â if you donât care, or else a well-known service name.
+ use â0â if you don't care, or else a well-known service name.
NOTE: Failure in opening a two-way socket will result in a nonfatal
error being returned to the calling code. The value of âERRNOâ
@@ -22226,7 +22205,7 @@ REMOTE-PORT
close(Service)
}
- This program reads the current date and time from the local systemâs
+ This program reads the current date and time from the local system's
TCP âdaytimeâ server. It then prints the results and closes the
connection.
@@ -22352,26 +22331,26 @@ profiler on this program and data (this example also
illustrates that
output. They are as follows:
⢠The program is printed in the order âBEGINâ rules, âBEGINFILEâ
- rules, patternâaction rules, âENDFILEâ rules, âENDâ rules, and
+ rules, pattern-action rules, âENDFILEâ rules, âENDâ rules, and
functions, listed alphabetically. Multiple âBEGINâ and âENDâ
rules
retain their separate identities, as do multiple âBEGINFILEâ and
âENDFILEâ rules.
- ⢠Patternâaction rules have two counts. The first count, to the left
- of the rule, shows how many times the ruleâs pattern was _tested_.
- The second count, to the right of the ruleâs opening left brace in
- a comment, shows how many times the ruleâs action was _executed_.
- The difference between the two indicates how many times the ruleâs
+ ⢠Pattern-action rules have two counts. The first count, to the left
+ of the rule, shows how many times the rule's pattern was _tested_.
+ The second count, to the right of the rule's opening left brace in
+ a comment, shows how many times the rule's action was _executed_.
+ The difference between the two indicates how many times the rule's
pattern evaluated to false.
⢠Similarly, the count for an âifâ-âelseâ statement shows how many
times the condition was tested. To the right of the opening left
- brace for the âifââs body is a count showing how many times the
+ brace for the âifâ's body is a count showing how many times the
condition was true. The count for the âelseâ indicates how many
times the test failed.
⢠The count for a loop header (such as âforâ or âwhileâ) shows how
- many times the loop test was executed. (Because of this, you canât
+ many times the loop test was executed. (Because of this, you can't
just look at the count on the first statement in a rule to
determine how many times the rule was executed. If the first
statement is a loop, the count is misleading.)
@@ -22381,7 +22360,7 @@ output. They are as follows:
counts next to the statements in the body show how many times those
statements were executed.
- ⢠The layout uses âK&Râ style with TABs. Braces are used everywhere,
+ ⢠The layout uses "K&R" style with TABs. Braces are used everywhere,
even when the body of an âifâ, âelseâ, or loop is only a single
statement.
@@ -22394,11 +22373,11 @@ output. They are as follows:
⢠Parentheses are used around the arguments to âprintâ and
âprintfâ
only when the âprintâ or âprintfâ statement is followed by a
- redirection. Similarly, if the target of a redirection isnât a
+ redirection. Similarly, if the target of a redirection isn't a
scalar, it gets parenthesized.
⢠âgawkâ supplies leading comments in front of the âBEGINâ and
âENDâ
- rules, the âBEGINFILEâ and âENDFILEâ rules, the patternâaction
+ rules, the âBEGINFILEâ and âENDFILEâ rules, the pattern-action
rules, and the functions.
⢠Functions are listed alphabetically. All functions in the âawkâ
@@ -22409,7 +22388,7 @@ output. They are as follows:
The profiled version of your program may not look exactly like what
you typed when you wrote it. This is because âgawkâ creates the
-profiled version by âpretty-printingâ its internal representation of the
+profiled version by "pretty-printing" its internal representation of the
program. The advantage to this is that âgawkâ can produce a standard
representation. Also, things such as:
@@ -22461,14 +22440,14 @@ produces the profile and the function call trace and
then exits.
When âgawkâ runs on MS-Windows systems, it uses the âINTâ and
âQUITâ
signals for producing the profile, and in the case of the âINTâ signal,
-âgawkâ exits. This is because these systems donât support the âkillâ
+âgawkâ exits. This is because these systems don't support the âkillâ
command, so the only signals you can deliver to a program are those
generated by the keyboard. The âINTâ signal is generated by the
âCtrl-câ or âCtrl-BREAKâ key, while the âQUITâ signal is generated
by
the âCtrl-\â key.
Finally, âgawkâ also accepts another option, â--pretty-printâ. When
-called this way, âgawkâ âpretty-printsâ the program into
âawkprof.outâ,
+called this way, âgawkâ "pretty-prints" the program into âawkprof.outâ,
without any execution counts.
NOTE: Once upon a time, the â--pretty-printâ option would also run
@@ -22480,11 +22459,11 @@ preserves the original comments that were in the
program, although their
placement may not correspond exactly to their original locations in the
source code. However, no comments should be lost. Also, âgawkâ does
the best it can to preserve the distinction between comments at the end
-of a statement and comments on lines by themselves. This isnât always
+of a statement and comments on lines by themselves. This isn't always
perfect, though.
However, as a deliberate design decision, profiling output _omits_
-the original programâs comments. This allows you to focus on the
+the original program's comments. This allows you to focus on the
execution count data and helps you avoid the temptation to use the
profiler for pretty-printing.
@@ -22495,7 +22474,7 @@ result as the final version of your program.
Because the internal representation of your program is formatted to
recreate an âawkâ program, profiling and pretty-printing automatically
-disable âgawkââs default optimizations.
+disable âgawkâ's default optimizations.
Profiling and pretty-printing also preserve the original format of
numeric constants; if you used an octal or hexadecimal value in your
@@ -22508,10 +22487,10 @@ File: gawk.info, Node: Persistent Memory, Next:
Extension Philosophy, Prev: P
=================================
Starting with version 5.2, âgawkâ supports âpersistent memoryâ. This
-experimental feature stores the values of all of âgawkââs variables,
+experimental feature stores the values of all of âgawkâ's variables,
arrays and user-defined functions in a persistent heap, which resides in
a file in the filesystem. When persistent memory is not in use (the
-normal case), âgawkââs data resides in ephemeral system memory.
+normal case), âgawkâ's data resides in ephemeral system memory.
Persistent memory is enabled on certain 64-bit systems supporting the
âmmap()â and âmunmap()â system calls. âgawkâ must be compiled as a
@@ -22528,7 +22507,7 @@ so:
⣠Copyright (C) 1989, 1991-2023 Free Software Foundation.
...
-If you see the âPMAâ with a version indicator, then itâs supported.
+If you see the âPMAâ with a version indicator, then it's supported.
As of this writing, persistent memory has only been tested on
GNU/Linux, Cygwin, Solaris 2.11, Intel architecture macOS systems,
@@ -22567,13 +22546,13 @@ the tests pass, please let the maintainer know.
3
As shown, in subsequent runs using the same data file, the values
- of âgawkââs variables are preserved. However, âgawkââs
special
+ of âgawkâ's variables are preserved. However, âgawkâ's special
variables, such as âNRâ, are reset upon each run. Only the
variables defined by the program are preserved across runs.
Interestingly, the program that you execute need not be the same from
run to run; the persistent store only maintains the values of variables,
-arrays, and user-defined functions, not the totality of âgawkââs
+arrays, and user-defined functions, not the totality of âgawkâ's
internal state. This lets you share data between unrelated programs,
eliminating the need for scripts to communicate via text files.
@@ -22582,11 +22561,11 @@ uses, provides the following advice about the backing
file:
Regarding backing file size, I recommend making it far larger than
all of the data that will ever reside in it, assuming that the file
- system supports sparse files. The âpay only for what you useâ
+ system supports sparse files. The "pay only for what you use"
aspect of sparse files ensures that the actual storage resource
- footprint of the backing file will meet the applicationâs needs but
+ footprint of the backing file will meet the application's needs but
will be as small as possible. If the file system does _not_
- support sparse files, thereâs a dilemma: Making the backing file
+ support sparse files, there's a dilemma: Making the backing file
too large is wasteful, but making it too small risks memory
exhaustion, i.e., âpma_malloc()â returns âNULLâ. But persistent
âgawkâ should still work even without sparse files.
@@ -22605,7 +22584,7 @@ the different verbosity levels are.
⢠If you use MPFR mode (the â-Mâ option) on the first run of a
program using persistent memory, you _must_ continue to use it on
- all subsequent runs. Similarly, if you donât use â-Mâ on the first
+ all subsequent runs. Similarly, if you don't use â-Mâ on the first
run, do not use it on any subsequent runs.
Mixing and matching MPFR mode and regular mode with the same
@@ -22613,14 +22592,14 @@ the different verbosity levels are.
issues a fatal error message.
⢠The GNU/Linux CIFS filesystem is known to not work well with the
- PMA allocator. Donât use a backing file on a CIFS filesystem.
+ PMA allocator. Don't use a backing file on a CIFS filesystem.
⢠If âgawkâ is run by the ârootâ user, then persistent memory is
not
allowed. This is to avoid the possibility of private data
- âleakingâ into the backing file and being recovered later by an
+ "leaking" into the backing file and being recovered later by an
attacker.
- ⢠Over time, the backing file will be filled with memory âleakedâ by
+ ⢠Over time, the backing file will be filled with memory "leaked" by
âgawkâ as it runs. Most notably this is the memory used to compile
your program into an internal form before running it, which happens
each time, but there are other leakages as well. (For an extreme
@@ -22636,11 +22615,11 @@ Manualâ document, which is included in the
âgawkâ distribution. It is
worth reading. *Note General Introduction: (pm-gawk)Top.
Here are additional articles and web links that provide more
-information about persistent memory and why itâs useful in a scripting
+information about persistent memory and why it's useful in a scripting
language like âgawkâ.
<https://web.eecs.umich.edu/~tpkelly/pma/>
- This is the canonical source for Terence Kellyâs Persistent Memory
+ This is the canonical source for Terence Kelly's Persistent Memory
Allocator (PMA). The latest source code and user manual will always
be available at this location. Kelly may be reached directly at
any of the following email addresses: <tpkelly@acm.org>,
@@ -22678,7 +22657,7 @@ language like âgawkâ.
Terence Kelly, ACM âQueueâ magazine Vol. 19 No. 4 (July/Aug
2021), PDF (https://dl.acm.org/doi/pdf/10.1145/3487019.3487353),
HTML (https://queue.acm.org/detail.cfm?id=3487353). This paper
- describes a crash-tolerance feature added to GNU DBMâ (âgdbmâ).
+ describes a crash-tolerance feature added to GNU DBM' (âgdbmâ).
When Terence Kelly published his papers, his collaborators produced a
prototype integration of PMA with âgawkâ. That version used a
@@ -22709,7 +22688,7 @@ As this and subsequent major nodes show, âgawkâ has
a large number of
extensions over standard âawkâ built-in to the program. These have
developed over time. More recently, the focus has moved to using the
extension mechanism (*note Dynamic Extensions::) for adding features.
-This minor node discusses the âguiding philosophyâ behind what should be
+This minor node discusses the "guiding philosophy" behind what should be
added to the interpreter as a built-in feature versus what should be
done in extensions.
@@ -22732,7 +22711,7 @@ done in extensions.
the sample extensions demonstrate this.
Loading extensions and library files should not be done
-automatically, because then thereâs overhead that most users donât want
+automatically, because then there's overhead that most users don't want
or need.
@@ -22774,7 +22753,7 @@ File: gawk.info, Node: Advanced Features Summary,
Prev: Extension Philosophy,
âUSR1â signal while profiling causes âgawkâ to dump the profile
and
keep going, including a function call stack.
- ⢠You can also just âpretty-printâ the program.
+ ⢠You can also just "pretty-print" the program.
⢠Persistent memory allows you to preserve the values of variables
and arrays between runs of âgawkâ. This feature is currently
@@ -22791,10 +22770,10 @@ File: gawk.info, Node: Internationalization, Next:
Debugger, Prev: Advanced F
***********************************
Moon... Gorgeous... MEDITATION!
- â _Pretty Guardian Sailor Moon Eternal, The Movie_
+ -- _Pretty Guardian Sailor Moon Eternal, The Movie_
It probably sounded better in Japanese.
- â _Malka Robbins_
+ -- _Malka Robbins_
Once upon a time, computer makers wrote software that worked only in
English. Eventually, hardware and software vendors noticed that if
@@ -22808,8 +22787,8 @@ largely restricted to programs written in C and C++.
This major node
describes the underlying library âgawkâ uses for internationalization,
as well as how âgawkâ makes internationalization features available at
the âawkâ program level. Having internationalization available at the
-âawkâ level gives software developers additional flexibilityâthey are no
-longer forced to write in C or C++ when internationalization is a
+âawkâ level gives software developers additional flexibility--they are
+no longer forced to write in C or C++ when internationalization is a
requirement.
* Menu:
@@ -22851,21 +22830,21 @@ program, either directly or via formatting with
âprintfâ or
When using GNU âgettextâ, each application has its own âtext
domainâ.
This is a unique name, such as âkpilotâ or âgawkâ, that identifies the
application. A complete application may have multiple
-componentsâprograms written in C or C++, as well as scripts written in
+components--programs written in C or C++, as well as scripts written in
âshâ or âawkâ. All of the components use the same text domain.
- To make the discussion concrete, assume weâre writing an application
+ To make the discussion concrete, assume we're writing an application
named âguideâ. Internationalization consists of the following steps, in
this order:
- 1. The programmer reviews the source for all of âguideââs components
+ 1. The programmer reviews the source for all of âguideâ's components
and marks each string that is a candidate for translation. For
example, â"`-F': option required"â is a good candidate for
translation. A table with strings of option names is not (e.g.,
- âgawkââs â--profileâ option should remain the same, no matter
what
+ âgawkâ's â--profileâ option should remain the same, no matter what
the local language).
- 2. The programmer indicates the applicationâs text domain (â"guide"â)
+ 2. The programmer indicates the application's text domain (â"guide"â)
to the âgettextâ library, by calling the âtextdomain()â function.
3. Messages from the application are extracted from the source code
@@ -22879,7 +22858,7 @@ this order:
shipped with the application. For example, there might be a
âfr.poâ for a French translation.
- 5. Each languageâs â.poâ file is converted into a binary message
+ 5. Each language's â.poâ file is converted into a binary message
object (â.gmoâ) file. A message object file contains the original
messages and their translations in a binary format that allows fast
lookup of translations at runtime.
@@ -22897,7 +22876,7 @@ this order:
9. If necessary, it is possible to access messages from a different
text domain than the one belonging to the application, without
- having to switch the applicationâs default text domain back and
+ having to switch the application's default text domain back and
forth.
In C (or C++), the string marking and dynamic translation lookup are
@@ -22959,14 +22938,14 @@ are:
NOTE: As described in *note Locales::, environment variables with
the same name as the locale categories (âLC_CTYPEâ, âLC_ALLâ,
etc.)
- influence âgawkââs behavior (and that of other utilities).
+ influence âgawkâ's behavior (and that of other utilities).
Normally, these variables also affect how the âgettextâ library
finds translations. However, the âLANGUAGEâ environment variable
overrides the âLC_XXXâ variables. Many GNU/Linux systems may
define this variable without your knowledge, causing âgawkâ to not
find the correct translations. If this happens to you, look to see
- if âLANGUAGEâ is defined, and if so, use the shellâs âunsetâ
+ if âLANGUAGEâ is defined, and if so, use the shell's âunsetâ
command to remove it.
For testing translations of âgawkâ itself, you can set the
@@ -22976,7 +22955,7 @@ Variables::.
---------- Footnotes ----------
- (1) For some operating systems, the âgawkâ port doesnât support GNU
+ (1) For some operating systems, the âgawkâ port doesn't support GNU
âgettextâ. Therefore, these features are not available if you are using
one of those operating systems. Sorry.
@@ -22993,7 +22972,7 @@ File: gawk.info, Node: Programmer i18n, Next:
Translator i18n, Prev: Explaini
âgawkâ provides the following variables for internationalization:
âTEXTDOMAINâ
- This variable indicates the applicationâs text domain. For
+ This variable indicates the application's text domain. For
compatibility with GNU âgettextâ, the default value is
â"messages"â.
@@ -23017,7 +22996,7 @@ File: gawk.info, Node: Programmer i18n, Next:
Translator i18n, Prev: Explaini
CAUTION: The order of arguments to the âawkâ version of the
âdcgettext()â function is purposely different from the order
- for the C version. The âawkâ versionâs order was chosen to be
+ for the C version. The âawkâ version's order was chosen to be
simple and to allow for reasonable âawkâ-style default
arguments.
@@ -23036,7 +23015,7 @@ File: gawk.info, Node: Programmer i18n, Next:
Translator i18n, Prev: Explaini
Change the directory in which âgettextâ looks for â.gmoâ files, in
case they will not or cannot be placed in the standard locations
(e.g., during testing). Return the directory in which DOMAIN is
- âbound.â
+ "bound."
The default DOMAIN is the value of âTEXTDOMAINâ. If DIRECTORY is
the null string (â""â), then âbindtextdomain()â returns the
current
@@ -23115,13 +23094,13 @@ File: gawk.info, Node: Translator i18n, Next: I18N
Example, Prev: Programmer
13.4 Translating âawkâ Programs
===============================
-Once a programâs translatable strings have been marked, they must be
+Once a program's translatable strings have been marked, they must be
extracted to create the initial â.potâ file. As part of translation, it
is often helpful to rearrange the order in which arguments to âprintfâ
are output.
- âgawkââs â--gen-potâ command-line option extracts the messages
and is
-discussed next. After that, âprintfââs ability to rearrange the order
+ âgawkâ's â--gen-potâ command-line option extracts the messages and
is
+discussed next. After that, âprintfâ's ability to rearrange the order
for âprintfâ arguments at runtime is covered.
* Menu:
@@ -23137,7 +23116,7 @@ File: gawk.info, Node: String Extraction, Next:
Printf Ordering, Up: Translat
--------------------------------
Once your âawkâ program is working, and all the strings have been marked
-and youâve set (and perhaps bound) the text domain, it is time to
+and you've set (and perhaps bound) the text domain, it is time to
produce translations. First, use the â--gen-potâ command-line option to
create the initial â.potâ file:
@@ -23224,7 +23203,7 @@ with positional specifiers in the same string:
NOTE: There are some pathological cases that âgawkâ may fail to
diagnose. In such cases, the output may not be what you expect.
- Itâs still a bad idea to try mixing them, even if âgawkâ doesnât
+ It's still a bad idea to try mixing them, even if âgawkâ doesn't
detect it.
Although positional specifiers can be used directly in âawkâ
@@ -23242,7 +23221,7 @@ File: gawk.info, Node: I18N Portability, Prev: Printf
Ordering, Up: Translato
13.4.3 âawkâ Portability Issues
-------------------------------
-âgawkââs internationalization features were purposely chosen to have as
+âgawkâ's internationalization features were purposely chosen to have as
little impact as possible on the portability of âawkâ programs that use
them to other versions of âawkâ. Consider this program:
@@ -23253,10 +23232,10 @@ them to other versions of âawkâ. Consider this
program:
print _"don't panic!"
}
-As written, it wonât work on other versions of âawkâ. However, it is
+As written, it won't work on other versions of âawkâ. However, it is
actually almost portable, requiring very little change:
- ⢠Assignments to âTEXTDOMAINâ wonât have any effect, because
+ ⢠Assignments to âTEXTDOMAINâ won't have any effect, because
âTEXTDOMAINâ is not special in other âawkâ implementations.
⢠Non-GNU versions of âawkâ treat marked strings as the concatenation
@@ -23264,7 +23243,7 @@ actually almost portable, requiring very little change:
Typically, the variable â_â has the null string (â""â) as its
value, leaving the original string constant as the result.
- ⢠By defining âdummyâ functions to replace âdcgettext()â,
+ ⢠By defining "dummy" functions to replace âdcgettext()â,
âdcngettext()â, and âbindtextdomain()â, the âawkâ program can
be
made to run, but all the messages are output in the original
language. For example:
@@ -23286,12 +23265,12 @@ actually almost portable, requiring very little
change:
⢠The use of positional specifications in âprintfâ or âsprintf()â
is
_not_ portable. To support âgettext()â at the C level, many
- systemsâ C versions of âsprintf()â do support positional
+ systems' C versions of âsprintf()â do support positional
specifiers. But it works only if enough arguments are supplied in
the function call. Many versions of âawkâ pass âprintfâ formats
and arguments unchanged to the underlying C library version of
âsprintf()â, but only one format and argument at a time. What
- happens if a positional specification is used is anybodyâs guess.
+ happens if a positional specification is used is anybody's guess.
However, because the positional specifications are primarily for
use in _translated_ format strings, and because non-GNU âawkâs
never retrieve the translated string, this should not be a problem
@@ -23299,7 +23278,7 @@ actually almost portable, requiring very little change:
---------- Footnotes ----------
- (1) This is good fodder for an âObfuscated âawkââ contest.
+ (1) This is good fodder for an "Obfuscated âawkâ" contest.
File: gawk.info, Node: I18N Example, Next: Gawk I18N, Prev: Translator
i18n, Up: Internationalization
@@ -23307,7 +23286,7 @@ File: gawk.info, Node: I18N Example, Next: Gawk I18N,
Prev: Translator i18n,
13.5 A Simple Internationalization Example
==========================================
-Now letâs look at a step-by-step example of how to internationalize and
+Now let's look at a step-by-step example of how to internationalize and
localize a simple âawkâ program, using âguide.awkâ as our original
source:
@@ -23342,7 +23321,7 @@ the original string and the âmsgstrâ is the
translation.
the âguide.potâ file.
Next, the messages must be translated. Here is a translation to a
-hypothetical dialect of English, called âMellowâ:(1)
+hypothetical dialect of English, called "Mellow":(1)
$ cp guide.pot guide-mellow.po
ADD TRANSLATIONS TO guide-mellow.po ...
@@ -23406,7 +23385,7 @@ and âbindtextdomain()â (*note I18N Portability::)
are in a file named
---------- Footnotes ----------
- (1) Perhaps it would be better if it were called âHippy.â Ah, well.
+ (1) Perhaps it would be better if it were called "Hippy." Ah, well.
(2) Well, sort of. It seems that if â$LC_ALLâ is set to âCâ, then
no
translations are done. Go figure.
@@ -23423,7 +23402,7 @@ package. (GNU âgettextâ is described in complete
detail in *Note GNU
version of GNU âgettextâ is version 0.19.8.1
(ftp://ftp.gnu.org/gnu/gettext/gettext-0.19.8.1.tar.gz).
- If a translation of âgawkââs messages exists, then âgawkâ produces
+ If a translation of âgawkâ's messages exists, then âgawkâ produces
usage messages, warnings, and fatal errors in the local language.
@@ -23438,10 +23417,10 @@ File: gawk.info, Node: I18N Summary, Prev: Gawk
I18N, Up: Internationalizatio
internationalized program to work in a particular language.
⢠âgawkâ uses GNU âgettextâ to let you internationalize and
localize
- âawkâ programs. A programâs text domain identifies the program for
+ âawkâ programs. A program's text domain identifies the program for
grouping all messages and other data together.
- ⢠You mark a programâs strings for translation by preceding them with
+ ⢠You mark a program's strings for translation by preceding them with
an underscore. Once that is done, the strings are extracted into a
â.potâ file. This file is copied for each language into a â.poâ
file, and the â.poâ files are compiled into â.gmoâ files for use
at
@@ -23467,7 +23446,7 @@ File: gawk.info, Node: Debugger, Next: Namespaces,
Prev: Internationalization
It would be nice if computer programs worked perfectly the first time
they were run, but in real life, this rarely happens for programs of any
complexity. Thus, most programming languages have facilities available
-for âdebuggingâ programs, and âawkâ is no exception.
+for "debugging" programs, and âawkâ is no exception.
The âgawkâ debugger is purposely modeled after the GNU Debugger (GDB)
(https://www.gnu.org/software/gdb/) command-line debugger. If you are
@@ -23508,8 +23487,8 @@ File: gawk.info, Node: Debugging Concepts, Next:
Debugging Terms, Up: Debuggi
ahead to *note Awk Debugging::.)
Of course, a debugging program cannot remove bugs for you, because it
-has no way of knowing what you or your users consider a âbugâ versus a
-âfeature.â (Sometimes, we humans have a hard time with this ourselves.)
+has no way of knowing what you or your users consider a "bug" versus a
+"feature." (Sometimes, we humans have a hard time with this ourselves.)
In that case, what can you expect from such a tool? The answer to that
depends on the language being debugged, but in general, you can expect
at least the following:
@@ -23529,7 +23508,7 @@ at least the following:
to look at internal data structures besides the variables you
actually defined in your code.)
- ⢠The ability to obtain additional information about your programâs
+ ⢠The ability to obtain additional information about your program's
state or even its internal structure.
All of these tools provide a great amount of help in using your own
@@ -23558,8 +23537,8 @@ defines terms used throughout the rest of this major
node:
stackâ.
For each function on the call stack, the system maintains a data
- area that contains the functionâs parameters, local variables, and
- return value, as well as any other âbookkeepingâ information needed
+ area that contains the function's parameters, local variables, and
+ return value, as well as any other "bookkeeping" information needed
to manage the call stack. This data area is termed a âstack
frameâ.
@@ -23575,7 +23554,7 @@ defines terms used throughout the rest of this major
node:
statement (or instruction) at a time. The way to do this is to set
a âbreakpointâ within the program. A breakpoint is where the
execution of the program should break off (stop), so that you can
- take over control of the programâs execution. You can add and
+ take over control of the program's execution. You can add and
remove as many breakpoints as you like.
âWatchpointâ
@@ -23584,7 +23563,7 @@ defines terms used throughout the rest of this major
node:
in the code is reached. A watchpoint, however, specifies that
program execution should stop when a _data value_ is changed. This
is useful, as sometimes it happens that a variable receives an
- erroneous value, and itâs hard to track down where this happens
+ erroneous value, and it's hard to track down where this happens
just by looking at the code. By using a watchpoint, you can stop
whenever a variable is assigned to, and usually find the errant
code quite quickly.
@@ -23606,14 +23585,14 @@ treated almost like a function call, with its own
specific block of
instructions.
In addition, because âawkâ is by design a very concise language, it
-is easy to lose sight of everything that is going on âinsideâ each line
+is easy to lose sight of everything that is going on "inside" each line
of âawkâ code. The debugger provides the opportunity to look at the
individual primitive instructions carried out by the higher-level âawkâ
commands.(1)
---------- Footnotes ----------
- (1) The âprimitive instructionsâ are defined by âgawkâ itself; the
+ (1) The "primitive instructions" are defined by âgawkâ itself; the
debugger does not work at the level of machine instructions.
@@ -23622,7 +23601,7 @@ File: gawk.info, Node: Sample Debugging Session,
Next: List of Debugger Comman
14.2 Sample âgawkâ Debugging Session
====================================
-In order to illustrate the use of âgawkâ as a debugger, letâs look at a
+In order to illustrate the use of âgawkâ as a debugger, let's look at a
sample debugging session. We will use the âawkâ implementation of the
POSIX âuniqâ command presented earlier (*note Uniq Program::) as our
example.
@@ -23653,7 +23632,7 @@ users of GDB or similar debuggers should note that this
syntax is
slightly different from what you are used to. With the âgawkâ debugger,
you give the arguments for running the program in the command line to
the debugger rather than as part of the ârunâ command at the debugger
-prompt.) The â--â ends âgawkââs command line options. Itâs not
+prompt.) The â--â ends âgawkâ's command line options. It's not
strictly necessary here, but it is needed if an option to the âawkâ
program conflicts with a âgawkâ option. The â-1â is an option to
âuniq.awkâ.
@@ -23673,8 +23652,8 @@ File: gawk.info, Node: Finding The Bug, Prev:
Debugger Invocation, Up: Sample
14.2.2 Finding the Bug
----------------------
-Letâs say that we are having a problem using (a faulty version of)
-âuniq.awkâ in âfield-skippingâ mode, and it doesnât seem to be
catching
+Let's say that we are having a problem using (a faulty version of)
+âuniq.awkâ in "field-skipping" mode, and it doesn't seem to be catching
lines which should be identical when skipping the first field, such as:
awk is a wonderful program!
@@ -23714,9 +23693,9 @@ breakpoint for the first time:
⣠63 if (fcount == 0 && charcount == 0)
gawk>
- Now we can look at whatâs going on inside our program. First of all,
-letâs see how we got to where we are. At the prompt, we type âbtâ
-(short for âbacktraceâ), and the debugger responds with a listing of the
+ Now we can look at what's going on inside our program. First of all,
+let's see how we got to where we are. At the prompt, we type âbtâ
+(short for "backtrace"), and the debugger responds with a listing of the
current stack frames:
gawk> bt
@@ -23730,8 +23709,8 @@ only call to âare_equal()â in the program, but in
more complex programs,
knowing who called a function and with what parameters can be the key to
finding the source of the problem.)
- Now that weâre in âare_equal()â, we can start looking at the values
-of some variables. Letâs say we type âp nâ (âpâ is short for
âprintâ).
+ Now that we're in âare_equal()â, we can start looking at the values
+of some variables. Let's say we type âp nâ (âpâ is short for "print").
We would expect to see the value of ânâ, a parameter to âare_equal()â.
Actually, the debugger gives us:
@@ -23747,7 +23726,7 @@ function was called without arguments (*note Function
Calls::).
⣠$0 = "gawk is a wonderful program!"
This might be a bit puzzling at first, as this is the second line of our
-test input. Letâs look at âNRâ:
+test input. Let's look at âNRâ:
gawk> p NR
⣠NR = 2
@@ -23761,7 +23740,7 @@ of the file. Of course, this is because our program
contains a rule for
next
}
- OK, letâs just check that that rule worked correctly:
+ OK, let's just check that that rule worked correctly:
gawk> p last
⣠last = "awk is a wonderful program!"
@@ -23769,14 +23748,14 @@ of the file. Of course, this is because our program
contains a rule for
Everything we have done so far has verified that the program has
worked as planned, up to and including the call to âare_equal()â, so the
problem must be inside this function. To investigate further, we must
-begin âstepping throughâ the lines of âare_equal()â. We start by
typing
-ânâ (for ânextâ):
+begin "stepping through" the lines of âare_equal()â. We start by typing
+ânâ (for "next"):
gawk> n
⣠66 if (fcount > 0) {
This tells us that âgawkâ is now ready to execute line 66, which
-decides whether to give the lines the special âfield-skippingâ treatment
+decides whether to give the lines the special "field-skipping" treatment
indicated by the â-1â command-line option. (Notice that we skipped from
where we were before, at line 63, to here, because the condition in line
63, âif (fcount == 0 && charcount == 0)â, was false.)
@@ -23798,12 +23777,12 @@ split into, so we try to look:
⣠alast = array, 5 elements
⣠aline = untyped variable
-(The âpâ command can take more than one argument, similar to âawkââs
+(The âpâ command can take more than one argument, similar to âawkâ's
âprintâ statement.)
This is kind of disappointing, though. All we found out is that
-there are five elements in âalastâ; âmâ and âalineâ donât have
values
-because we are at line 68 but havenât executed it yet. This information
+there are five elements in âalastâ; âmâ and âalineâ don't have
values
+because we are at line 68 but haven't executed it yet. This information
is useful enough (we now know that none of the words were accidentally
left out), but what if we want to see inside the array?
@@ -23828,7 +23807,7 @@ mentioned):
⣠alast["4"] = "wonderful"
⣠alast["5"] = "program!"
- It looks like we got this far OK. Letâs take another step or two:
+ It looks like we got this far OK. Let's take another step or two:
gawk> n
⣠69 clast = join(alast, fcount, n)
@@ -23838,13 +23817,13 @@ mentioned):
Well, here we are at our error (sorry to spoil the suspense). What
we had in mind was to join the fields starting from the second one to
make the virtual record to compare, and if the first field were numbered
-zero, this would work. Letâs look at what weâve got:
+zero, this would work. Let's look at what we've got:
gawk> p cline clast
⣠cline = "gawk is a wonderful program!"
⣠clast = "awk is a wonderful program!"
- Hey, those look pretty familiar! Theyâre just our original,
+ Hey, those look pretty familiar! They're just our original,
unaltered input records. A little thinking (the human brain is still
the best debugging tool), and we realize that we were off by one!
@@ -23963,17 +23942,17 @@ The commands for controlling breakpoints are:
not specified, any existing condition is removed (i.e., the
breakpoint or watchpoint is made unconditional).
-âdeleteâ [N1 N2 ...] [NâM]
-âdâ [N1 N2 ...] [NâM]
+âdeleteâ [N1 N2 ...] [N-M]
+âdâ [N1 N2 ...] [N-M]
Delete specified breakpoints or a range of breakpoints. Delete all
defined breakpoints if no argument is supplied.
-âdisableâ [N1 N2 ... | NâM]
+âdisableâ [N1 N2 ... | N-M]
Disable specified breakpoints or a range of breakpoints. Without
any argument, disable all breakpoints.
-âenableâ [âdelâ | âonceâ] [N1 N2 ...] [NâM]
-âeâ [âdelâ | âonceâ] [N1 N2 ...] [NâM]
+âenableâ [âdelâ | âonceâ] [N1 N2 ...] [N-M]
+âeâ [âdelâ | âonceâ] [N1 N2 ...] [N-M]
Enable specified breakpoints or a range of breakpoints. Without
any argument, enable all breakpoints. Optionally, you can specify
how to enable the breakpoints:
@@ -24050,7 +24029,7 @@ execution of the program than we saw in our earlier
example:
âreturnâ [VALUE]
Cancel execution of a function call. If VALUE (either a string or
- a number) is specified, it is used as the functionâs return value.
+ a number) is specified, it is used as the function's return value.
If used in a frame other than the innermost one (the currently
executing function; i.e., frame number 0), discard all inner frames
in addition to the selected one, and the caller of that frame
@@ -24072,7 +24051,7 @@ execution of the program than we saw in our earlier
example:
âstepiâ [COUNT]
âsiâ [COUNT]
Execute one (or COUNT) instruction(s), stepping inside function
- calls. (For illustration of what is meant by an âinstructionâ in
+ calls. (For illustration of what is meant by an "instruction" in
âgawkâ, see the output shown under âdumpâ in *note Miscellaneous
Debugger Commands::.)
@@ -24118,8 +24097,8 @@ The commands for viewing and changing variables inside
of âgawkâ are:
âevalâ PARAM, ...
AWK STATEMENTS
âendâ
- This form of âevalâ is similar, but it allows you to define âlocal
- variablesâ that exist in the context of the AWK STATEMENTS, instead
+ This form of âevalâ is similar, but it allows you to define "local
+ variables" that exist in the context of the AWK STATEMENTS, instead
of using variables or function parameters defined by the program.
âprintâ VAR1[â,â VAR2 ...]
@@ -24268,7 +24247,7 @@ know:
List all items in the watch list.
Additional commands give you control over the debugger, the ability
-to save the debuggerâs state, and the ability to run debugger commands
+to save the debugger's state, and the ability to run debugger commands
from a file. The commands are:
âoptionâ [NAME[â=âVALUE]]
@@ -24314,7 +24293,7 @@ from a file. The commands are:
Run command(s) from a file; an error in any command does not
terminate execution of subsequent commands. Comments (lines
starting with â#â) are allowed in a command file. Empty lines are
- ignored; they do _not_ repeat the last command. You canât restart
+ ignored; they do _not_ repeat the last command. You can't restart
the program by having more than one ârunâ command in the file.
Also, the list of commands may include additional âsourceâ
commands; however, the âgawkâ debugger will not source the same
@@ -24338,7 +24317,7 @@ categories, as follows:
named in FILENAME. This prints a representation of the internal
instructions that âgawkâ executes to implement the âawkâ commands
in a program. This can be very enlightening, as the following
- partial dump of Davide Briniâs obfuscated code (*note Signature
+ partial dump of Davide Brini's obfuscated code (*note Signature
Program::) demonstrates:
gawk> dump
@@ -24397,8 +24376,8 @@ categories, as follows:
summary of their usage. âhelp COMMANDâ prints the information
about the command COMMAND.
-âlistâ [â-â | â+â | N | FILENAMEâ:âN | NâM | FUNCTION]
-âlâ [â-â | â+â | N | FILENAMEâ:âN | NâM | FUNCTION]
+âlistâ [â-â | â+â | N | FILENAMEâ:âN | N-M | FUNCTION]
+âlâ [â-â | â+â | N | FILENAMEâ:âN | N-M | FUNCTION]
Print the specified lines (default 15) from the current source file
or the file named FILENAME. The possible arguments to âlistâ are
as follows:
@@ -24413,7 +24392,7 @@ categories, as follows:
N
Print lines centered around line number N.
- NâM
+ N-M
Print lines from N to M.
FILENAMEâ:âN
@@ -24437,7 +24416,7 @@ categories, as follows:
about to be executed, along with the âawkâ lines they implement.
The default is âoffâ.
- It is to be hoped that most of the âopcodesâ in these instructions
+ It is to be hoped that most of the "opcodes" in these instructions
are fairly self-explanatory, and using âstepiâ and ânextiâ while
âtraceâ is on will make them into familiar friends.
@@ -24449,7 +24428,7 @@ File: gawk.info, Node: Readline Support, Next:
Limitations, Prev: List of Deb
If âgawkâ is compiled with the GNU Readline library
(http://cnswww.cns.cwru.edu/php/chet/readline/readline.html), you can
-take advantage of that libraryâs command completion and history
+take advantage of that library's command completion and history
expansion features. The following types of completion are available:
Command completion
@@ -24476,36 +24455,36 @@ File: gawk.info, Node: Limitations, Next: Debugging
Summary, Prev: Readline S
We hope you find the âgawkâ debugger useful and enjoyable to work with,
but as with any program, especially in its early releases, it still has
-some limitations. A few that itâs worth being aware of are:
+some limitations. A few that it's worth being aware of are:
⢠At this point, the debugger does not give a detailed explanation of
- what you did wrong when you type in something it doesnât like.
+ what you did wrong when you type in something it doesn't like.
Rather, it just responds âsyntax errorâ. When you do figure out
- what your mistake was, though, youâll feel like a real guru.
+ what your mistake was, though, you'll feel like a real guru.
⢠If you perused the dump of opcodes in *note Miscellaneous Debugger
Commands:: (or if you are already familiar with âgawkâ internals),
you will realize that much of the internal manipulation of data in
âgawkâ, as in many interpreters, is done on a stack. âOp_pushâ,
- âOp_popâ, and the like are the âbread and butterâ of most
âgawkâ
+ âOp_popâ, and the like are the "bread and butter" of most âgawkâ
code.
Unfortunately, as of now, the âgawkâ debugger does not allow you to
- examine the stackâs contents. That is, the intermediate results of
+ examine the stack's contents. That is, the intermediate results of
expression evaluation are on the stack, but cannot be printed.
Rather, only variables that are defined in the program can be
printed. Of course, a workaround for this is to use more explicit
variables at the debugging stage and then change back to obscure,
perhaps more optimal code later.
- ⢠There is no way to look âinsideâ the process of compiling regular
+ ⢠There is no way to look "inside" the process of compiling regular
expressions to see if you got it right. As an âawkâ programmer,
you are expected to know the meaning of â/[^[:alnum:][:blank:]]/â.
⢠The âgawkâ debugger is designed to be used by running a program
(with all its parameters) on the command line, as described in
*note Debugger Invocation::. There is no way (as of now) to attach
- or âbreak intoâ a running program. This seems reasonable for a
+ or "break into" a running program. This seems reasonable for a
language that is used mainly for quickly executing, short programs.
⢠The âgawkâ debugger only accepts source code supplied with the
â-fâ
@@ -24580,7 +24559,7 @@ This major node describes a feature that is specific to
âgawkâ.
File: gawk.info, Node: Global Namespace, Next: Qualified Names, Up:
Namespaces
-15.1 Standard âawkââs Single Namespace
+15.1 Standard âawkâ's Single Namespace
======================================
In standard âawkâ, there is a single, global, ânamespaceâ. This means
@@ -24593,11 +24572,11 @@ and as an array in the other.
lines, or even a few thousand, but it prevents the development of
reusable libraries of âawkâ functions, and can inadvertently cause
independently-developed library files to accidentally step on each
-otherâs âprivateâ global variables (*note Library Names::).
+other's "private" global variables (*note Library Names::).
Most other programming languages solve this issue by providing some
-kind of namespace control: a way to say âthis function is in namespace
-XXX, and that function is in namespace YYY.â (Of course, there is then
+kind of namespace control: a way to say "this function is in namespace
+XXX, and that function is in namespace YYY." (Of course, there is then
still a single namespace for the namespaces, but the hope is that there
are much fewer namespaces in use by any given program, and thus much
less chance for collisions.) These facilities are sometimes referred to
@@ -24642,7 +24621,7 @@ have qualified names like âawk::ARGCâ,
âawk::NFâ, and so on.
current source file (*note Changing The Namespace::), âgawkâ forces
unqualified identifiers whose names are all uppercase letters to be in
the âawkâ namespace. This makes it possible for you to easily reference
-âgawkââs global variables from different namespaces. It also keeps your
+âgawkâ's global variables from different namespaces. It also keeps your
code looking natural.
@@ -24667,15 +24646,15 @@ file, although this is likely to become confusing if
you do it too much.
NOTE: Association of unqualified identifiers to a namespace is
handled while âgawkâ parses your program, _before_ it starts to
- run. There is no concept of a âcurrentâ namespace once your
+ run. There is no concept of a "current" namespace once your
program starts executing. Be sure you understand this.
Each source file for â-iâ and â-fâ starts out with an implicit
â@namespace "awk"â. Similarly, each chunk of command-line code supplied
with â-eâ has such an implicit initial statement (*note Options::).
- Files included with â@includeâ (*note Include Files::) âpushâ and
-âpopâ the current namespace. That is, each â@includeâ saves the
current
+ Files included with â@includeâ (*note Include Files::) "push" and
+"pop" the current namespace. That is, each â@includeâ saves the current
namespace and starts over with an implicit â@namespace "awk"â which
remains in effect until an explicit â@namespaceâ directive is seen.
When âgawkâ finishes processing the included file, the saved namespace
@@ -24855,7 +24834,7 @@ namespace.
*note Library Names::, whereby global variable and function names start
with a capital letter.
- Here is a simple test program. Since itâs in a separate file,
+ Here is a simple test program. Since it's in a separate file,
unadorned identifiers are sought for in the âawkâ namespace:
BEGIN {
@@ -24863,7 +24842,7 @@ unadorned identifiers are sought for in the âawkâ
namespace:
print p
}
- Hereâs what happens when itâs run:
+ Here's what happens when it's run:
$ gawk -f ns_passwd.awk -f testpasswd.awk
⣠root:x:0:0:root:/root:/bin/bash
@@ -24891,7 +24870,7 @@ everywhere.
Interaction with the debugger (*note Debugging::) has not had to
change (at least as of this writing). Some of the internal byte codes
-changed in order to accommodate namespaces, and the debuggerâs âdumpâ
+changed in order to accommodate namespaces, and the debugger's âdumpâ
command was adjusted to match.
The extension API (*note Dynamic Extensions::) has always allowed for
@@ -24931,7 +24910,7 @@ File: gawk.info, Node: Namespace Summary, Prev:
Namespace And Features, Up: N
the extension facility (*note Dynamic Extensions::).
⢠Overall, the namespace facility was designed and implemented such
- that backwards compatibility is paramount. Programs that donât use
+ that backwards compatibility is paramount. Programs that don't use
namespaces should see absolutely no difference in behavior when run
by a namespace-capable version of âgawkâ.
@@ -25002,7 +24981,7 @@ Decimal arithmetic
decimal arithmetic,(1) it does not do so.
Integer arithmetic
- In school, integer values were referred to as âwholeâ numbersâthat
+ In school, integer values were referred to as "whole" numbers--that
is, numbers without any fractional part, such as 1, 42, or â17.
The advantage to integer numbers is that they represent values
exactly. The disadvantage is that their range is limited.
@@ -25016,7 +24995,7 @@ Integer arithmetic
than floating-point arithmetic.
Floating-point arithmetic
- Floating-point numbers represent what were called in school ârealâ
+ Floating-point numbers represent what were called in school "real"
numbers (i.e., those that have a fractional part, such as
3.1415927). The advantage to floating-point numbers is that they
can represent a much larger range of values than can integers. The
@@ -25043,7 +25022,6 @@ values are always signed. The possible ranges of
values are shown in
*note Table 16.1: table-numeric-ranges. and *note Table 16.2:
table-floating-point-ranges.
-
Representation Minimum value Maximum value
---------------------------------------------------------------------------
32-bit signed integer â2,147,483,648 2,147,483,647
@@ -25055,7 +25033,6 @@ integer
Table 16.1: Value ranges for integer representations
-
Representation Minimum Minimum finite Maximum finite
positive value value
nonzero value
@@ -25072,7 +25049,7 @@ representations
---------- Footnotes ----------
- (1) We donât know why they expect this, but they do.
+ (1) We don't know why they expect this, but they do.
File: gawk.info, Node: Math Definitions, Next: MPFR features, Prev:
Computer Arithmetic, Up: Arbitrary Precision Arithmetic
@@ -25085,11 +25062,11 @@ informal definitions that should help you work your
way through the
material here:
âAccuracyâ
- A floating-point calculationâs accuracy is how close it comes to
+ A floating-point calculation's accuracy is how close it comes to
the real (paper and pencil) value.
âErrorâ
- The difference between what the result of a computation âshould beâ
+ The difference between what the result of a computation "should be"
and what it actually is. It is best to minimize error as much as
possible.
@@ -25102,7 +25079,7 @@ material here:
another number and infinity produce infinity.
âNaNâ
- âNot a number.â A special value that results from attempting a
+ "Not a number." A special value that results from attempting a
calculation that has no answer as a real number. *Note Strange
values::, for more information about infinity and not-a-number
values.
@@ -25134,9 +25111,9 @@ material here:
âStabilityâ
From the Wikipedia article on numerical stability
- (https://en.wikipedia.org/wiki/Numerical_stability): âCalculations
+ (https://en.wikipedia.org/wiki/Numerical_stability): "Calculations
that can be proven not to magnify approximation errors are called
- ânumerically stableâ.â
+ ânumerically stableâ."
See the Wikipedia article on accuracy and precision
(https://en.wikipedia.org/wiki/Accuracy_and_precision) for more
@@ -25152,7 +25129,6 @@ ranges. (âawkâ uses only the 64-bit
double-precision format.)
*note Table 16.3: table-ieee-formats. lists the precision and
exponent field values for the basic IEEE 754 binary formats.
-
Name Total bits Precision Minimum Maximum
exponent exponent
---------------------------------------------------------------------------
@@ -25185,8 +25161,8 @@ File: gawk.info, Node: MPFR On Parole, Next: MPFR
Intro, Up: MPFR features
16.3.1 Arbitrary Precision Arithmetic is On Parole!
---------------------------------------------------
-As of version 5.2, arbitrary precision arithmetic in âgawkâ is âon
-parole.â The primary âgawkâ maintainer is no longer maintaining it.
+As of version 5.2, arbitrary precision arithmetic in âgawkâ is "on
+parole." The primary âgawkâ maintainer is no longer maintaining it.
Fortunately, a volunteer from the development team has agreed to take it
over.
@@ -25224,8 +25200,8 @@ see if MPFR support is available like so:
⣠Copyright (C) 1989, 1991-2022 Free Software Foundation.
...
-(You may see different version numbers than whatâs shown here. Thatâs
-OK; whatâs important is to see that GNU MPFR and GNU MP are listed in
+(You may see different version numbers than what's shown here. That's
+OK; what's important is to see that GNU MPFR and GNU MP are listed in
the output.)
Additionally, there are a few elements available in the âPROCINFOâ
@@ -25251,7 +25227,7 @@ File: gawk.info, Node: FP Math Caution, Next:
Arbitrary Precision Integers, P
==============================================
Math class is tough!
- â _Teen Talk Barbie, July 1992_
+ -- _Teen Talk Barbie, July 1992_
This minor node provides a high-level overview of the issues involved
when doing lots of floating-point arithmetic.(1) The discussion applies
@@ -25272,8 +25248,8 @@ to both hardware and arbitrary-precision floating-point
arithmetic.
---------- Footnotes ----------
(1) There is a very nice paper on floating-point arithmetic
-(http://www.validlab.com/goldberg/paper.pdf) by David Goldberg, âWhat
-Every Computer Scientist Should Know About Floating-Point Arithmetic,â
+(http://www.validlab.com/goldberg/paper.pdf) by David Goldberg, "What
+Every Computer Scientist Should Know About Floating-Point Arithmetic,"
âACM Computing Surveysâ *23*, 1 (1991-03): 5-48. This is worth reading
if you are interested in the details, but it does require a background
in computer science.
@@ -25307,7 +25283,7 @@ File: gawk.info, Node: Inexact representation, Next:
Comparing FP Values, Up:
...................................................
So, before you start to write any code, you should think about what you
-really want and whatâs really happening. Consider the two numbers in
+really want and what's really happening. Consider the two numbers in
the following example:
x = 0.875 # 1/2 + 1/4 + 1/8
@@ -25369,7 +25345,7 @@ File: gawk.info, Node: Errors accumulate, Next:
Strange values, Prev: Compari
..........................
The loss of accuracy during a single computation with floating-point
-numbers usually isnât enough to worry about. However, if you compute a
+numbers usually isn't enough to worry about. However, if you compute a
value that is the result of a sequence of floating-point operations, the
error can accumulate and greatly affect the computation itself. Here is
an attempt to compute the value of pi using one of its many series
@@ -25413,11 +25389,11 @@ representations yield an unexpected result:
File: gawk.info, Node: Strange values, Prev: Errors accumulate, Up:
Inexactness of computations
-16.4.1.4 Floating Point Values They Didnât Talk About In School
+16.4.1.4 Floating Point Values They Didn't Talk About In School
...............................................................
Both IEEE 754 floating-point hardware, and MPFR, support two kinds of
-values that you probably didnât learn about in school. The first is
+values that you probably didn't learn about in school. The first is
âinfinityâ, a special value, that can be either negative or positive,
and which is either smaller than any other value (negative infinity), or
larger than any other value (positive infinity). When such values are
@@ -25429,7 +25405,7 @@ floating-point values internally.
Otherwise, operations (addition, subtraction, etc.) involving another
number and infinity produce mathematically reasonable results.
- The second kind of value is ânot a numberâ, or NaN for short.(1)
+ The second kind of value is "not a number", or NaN for short.(1)
This is a special value that results from attempting a calculation that
has no answer as a real number. In such a case, programs can either
receive a floating-point exception, or get NaN back as the result. The
@@ -25443,8 +25419,8 @@ IEEE 754 standard recommends that systems return NaN.
Some examples:
â8 is out of the domain of âlog()â, so the result is NaN.
NaN values are strange. In particular, they cannot be compared with
-other floating point values; any such comparison, except for âis not
-equal toâ, returns false. NaN values are so much unequal to other
+other floating point values; any such comparison, except for "is not
+equal to", returns false. NaN values are so much unequal to other
values that even comparing two identical NaN values with â!=â returns
true!
@@ -25571,7 +25547,6 @@ set the value to one of the predefined case-insensitive
strings shown in
*note Table 16.4: table-predefined-precision-strings, to emulate an IEEE
754 binary format.
-
âPRECâ IEEE 754 binary format
---------------------------------------------------
â"half"â 16-bit half-precision
@@ -25624,7 +25599,6 @@ The âROUNDMODEâ variable provides program-level
control over the
rounding mode. The correspondence between âROUNDMODEâ and the IEEE
rounding modes is shown in *note Table 16.5: table-gawk-rounding-modes.
-
Rounding mode IEEE name âROUNDMODEâ
---------------------------------------------------------------------------
Round to nearest, ties to even âroundTiesToEvenâ â"N"â or
â"n"â
@@ -25662,7 +25636,7 @@ example:
}
}
-produces the following output when run on the authorâs system:(1)
+produces the following output when run on the author's system:(1)
-3.5 => -4
-2.5 => -2
@@ -25681,8 +25655,7 @@ the default rounding mode for IEEE 754 computing
functions and
operators.
Rounding Modes and Conversion
-
- Itâs important to understand that, along with âCONVFMTâ and
âOFMTâ,
+ It's important to understand that, along with âCONVFMTâ and âOFMTâ,
the rounding mode affects how numbers are converted to strings. For
example, consider the following program:
@@ -25754,7 +25727,7 @@ correct output (using the formula âprec = 3.322 *
dpsâ) would be 3.322 x
The result from an arithmetic operation with an integer and a
floating-point value is a floating-point value with a precision equal to
the working precision. The following program calculates the eighth term
-in Sylvesterâs sequence(1) using a recurrence:
+in Sylvester's sequence(1) using a recurrence:
$ gawk -M 'BEGIN {
> s = 2.0
@@ -25799,7 +25772,7 @@ the following:
---------- Footnotes ----------
- (1) Weisstein, Eric W. âSylvesterâs Sequenceâ. From MathWorldâA
+ (1) Weisstein, Eric W. âSylvester's Sequenceâ. From MathWorld--A
Wolfram Web Resource
(<http://mathworld.wolfram.com/SylvestersSequence.html>).
@@ -25864,9 +25837,9 @@ These features are:
hexadecimal notation (e.g., â0xDEADBEEFâ). (Note: data values,
_not_ source code constants.)
- ⢠Support for the special IEEE 754 floating-point values ânot a
- numberâ (NaN), positive infinity (âinfâ), and negative infinity
- (ââinfâ). In particular, the format for these values is as
+ ⢠Support for the special IEEE 754 floating-point values "not a
+ number" (NaN), positive infinity ("inf"), and negative infinity
+ ("âinf"). In particular, the format for these values is as
specified by the ISO 1999 C standard, which ignores case and can
allow implementation-dependent additional characters after the
ânanâ and allow either âinfâ or âinfinityâ.
@@ -25883,14 +25856,14 @@ historical practice:
The second problem is that the âgawkâ maintainer feels that this
interpretation of the standard, which required a certain amount of
-âlanguage lawyeringâ to arrive at in the first place, was not even
-intended by the standard developers. In other words, âWe see how you
-got where you are, but we donât think that thatâs where you want to be.â
+"language lawyering" to arrive at in the first place, was not even
+intended by the standard developers. In other words, "We see how you
+got where you are, but we don't think that that's where you want to be."
Recognizing these issues, but attempting to provide compatibility
with the earlier versions of the standard, the 2008 POSIX standard added
explicit wording to allow, but not require, that âawkâ support
-hexadecimal floating-point values and special values for ânot a numberâ
+hexadecimal floating-point values and special values for "not a number"
and infinity.
Although the âgawkâ maintainer continues to feel that providing those
@@ -25898,10 +25871,10 @@ features is inadvisable, nevertheless, on systems
that support IEEE
floating point, it seems reasonable to provide _some_ way to support NaN
and infinity values. The solution implemented in âgawkâ is as follows:
- ⢠With the â--posixâ command-line option, âgawkâ becomes âhands
off.â
- String values are passed directly to the system libraryâs
+ ⢠With the â--posixâ command-line option, âgawkâ becomes "hands
off."
+ String values are passed directly to the system library's
âstrtod()â function, and if it successfully returns a numeric
- value, that is whatâs used.(1) By definition, the results are not
+ value, that is what's used.(1) By definition, the results are not
portable across different systems. They are also a little
surprising:
@@ -25927,16 +25900,16 @@ and infinity values. The solution implemented in
âgawkâ is as follows:
âgawkâ ignores case in the four special values. Thus, â+nanâ and
â+NaNâ are the same.
- Besides handling input, âgawkâ also needs to print âcorrectâ values
+ Besides handling input, âgawkâ also needs to print "correct" values
on output when a value is either NaN or infinity. Starting with version
4.2.2, for such values âgawkâ prints one of the four strings just
described: â+infâ, â-infâ, â+nanâ, or â-nanâ. Similarly, in
POSIX mode,
-âgawkâ prints the result of the systemâs C âprintf()â function using
the
+âgawkâ prints the result of the system's C âprintf()â function using
the
â%gâ format string for the value, whatever that may be.
NOTE: The sign used for NaN values can vary! The result depends
upon both the underlying system architecture and the underlying
- library used to format NaN values. In particular, itâs possible to
+ library used to format NaN values. In particular, it's possible to
get different results for the same function call depending upon
whether or not âgawkâ is running in MPFR mode (â-Mâ) or not.
Caveat Emptor!
@@ -25955,8 +25928,8 @@ File: gawk.info, Node: Floating point summary, Prev:
POSIX Floating Point Prob
floating-point values. Standard âawkâ uses double-precision
floating-point values.
- ⢠In the early 1990s Barbie mistakenly said, âMath class is tough!â
- Although math isnât tough, floating-point arithmetic isnât the same
+ ⢠In the early 1990s Barbie mistakenly said, "Math class is tough!"
+ Although math isn't tough, floating-point arithmetic isn't the same
as pencil-and-paper math, and care must be taken:
â Not all numbers can be represented exactly.
@@ -26009,7 +25982,7 @@ dynamically loaded libraries. This facility is
available on systems
that support the C âdlopen()â and âdlsym()â functions. This major node
describes how to create extensions using code written in C or C++.
- If you donât know anything about C programming, you can safely skip
+ If you don't know anything about C programming, you can safely skip
this major node, although you may wish to review the documentation on
the extensions that come with âgawkâ (*note Extension Samples::), and
the information on the âgawkextlibâ project (*note gawkextlib::). The
@@ -26044,10 +26017,10 @@ functionality, over and above the built-in
capabilities described in the
rest of this Info file.
Extensions are useful because they allow you (of course) to extend
-âgawkââs functionality. For example, they can provide access to system
+âgawkâ's functionality. For example, they can provide access to system
calls (such as âchdir()â to change directory) and to other C library
-routines that could be of use. As with most software, âthe sky is the
-limitâ; if you can imagine something that you might want to do and can
+routines that could be of use. As with most software, "the sky is the
+limit"; if you can imagine something that you might want to do and can
write in C or C++, you can write an extension to do it!
Extensions are written in C or C++, using the âapplication
@@ -26090,7 +26063,6 @@ an extension is loaded, âgawkâ passes it a pointer
to a âstructâ whose
fields are function pointers. This is shown in *note Figure 17.1:
figure-load-extension.
-
[image src="gawk_api-figure1.png" alt="Loading the extension" text="
API
Struct
+---+
@@ -26119,12 +26091,11 @@ figure-load-extension.
Figure 17.1: Loading the extension
The extension can call functions inside âgawkâ through these function
-pointers, at runtime, without needing (link-time) access to âgawkââs
+pointers, at runtime, without needing (link-time) access to âgawkâ's
symbols. One of these function pointers is to a function for
-âregisteringâ new functions. This is shown in *note Figure 17.2:
+"registering" new functions. This is shown in *note Figure 17.2:
figure-register-new-function.
-
[image src="gawk_api-figure2.png" alt="Registering a new Function" text="
register_ext_func({ \"chdir\", do_chdir, 1 });
+--------------------------------------------+
@@ -26147,7 +26118,6 @@ function pointer with a name and can then call it,
using a defined
calling convention. This is shown in *note Figure 17.3:
figure-call-new-function.
-
[image src="gawk_api-figure3.png" alt="Calling the new function" text="
BEGIN {
chdir(\"/path\") (*fnptr)(1);
}
@@ -26179,7 +26149,7 @@ Example::) and also in the âtestext.câ code for
testing the APIs.
Some other bits and pieces:
- ⢠The API provides access to âgawkââs âdo_XXXâ values,
reflecting
+ ⢠The API provides access to âgawkâ's âdo_XXXâ values, reflecting
command-line options, like âdo_lintâ, âdo_profilingâ, and so on
(*note Extension API Variables::). These are informational: an
extension cannot affect their values inside âgawkâ. In addition,
@@ -26187,7 +26157,7 @@ Example::) and also in the âtestext.câ code for
testing the APIs.
⢠The API also provides major and minor version numbers, so that an
extension can check if the âgawkâ it is loaded with supports the
- facilities it was compiled with. (Version mismatches âshouldnâtâ
+ facilities it was compiled with. (Version mismatches "shouldn't"
happen, but we all know how _that_ goes.) *Note Extension
Versioning:: for details.
@@ -26249,7 +26219,7 @@ operations:
All of these are discussed in detail later in this major node.
- ⢠Printing fatal, warning, and âlintâ warning messages.
+ ⢠Printing fatal, warning, and "lint" warning messages.
⢠Updating âERRNOâ, or unsetting it.
@@ -26286,7 +26256,6 @@ operations:
The list of macros and related header files is shown in *note Table
17.1: table-api-std-headers.
-
C entity Header file
-------------------------------------------
âEOFâ â<stdio.h>â
@@ -26314,7 +26283,7 @@ operations:
effect. Doing so, however, is poor coding practice.
⢠Although the API only uses ISO C 90 features, there is an
- exception; the âconstructorâ functions use the âinlineâ keyword.
+ exception; the "constructor" functions use the âinlineâ keyword.
If your compiler does not support this keyword, you should either
place â-Dinline=''â on your command line or use the GNU Autotools
and include a âconfig.hâ file in your extensions.
@@ -26356,14 +26325,14 @@ operations:
⢠When retrieving a value (such as a parameter or that of a global
variable or array element), the extension requests a specific type
- (number, string, scalar, value cookie, array, or âundefinedâ).
- When the request is âundefined,â the returned value will have the
+ (number, string, scalar, value cookie, array, or "undefined").
+ When the request is "undefined," the returned value will have the
real underlying type.
- However, if the request and actual type donât match, the access
- function returns âfalseâ and fills in the type of the actual value
+ However, if the request and actual type don't match, the access
+ function returns "false" and fills in the type of the actual value
that is there, so that the extension can, e.g., print an error
- message (such as âscalar passed where array expectedâ).
+ message (such as "scalar passed where array expected").
You may call the API functions by using the function pointers
directly, but the interface is not so pretty. To make extension code
@@ -26378,11 +26347,11 @@ File: gawk.info, Node: General Data Types, Next:
Memory Allocation Functions,
---------------------------------
I have a true love/hate relationship with unions.
- â _Arnold Robbins_
+ -- _Arnold Robbins_
- Thatâs the thing about unions: the compiler will arrange things so
+ That's the thing about unions: the compiler will arrange things so
they can accommodate both love and hate.
- â _Chet Ramey_
+ -- _Chet Ramey_
The extension API defines a number of simple types and structures for
general-purpose use. Additional, more specialized, data structures are
@@ -26445,7 +26414,7 @@ use them.
â awk_bool_t b;â
â } u;â
â} awk_value_t;â
- An ââawkâ value.â The âval_typeâ member indicates what kind of
+ An "âawkâ value." The âval_typeâ member indicates what kind of
value the âunionâ holds, and each member is of the appropriate
type.
@@ -26491,7 +26460,7 @@ use them.
CAUTION: Any MPFR or MPZ values that you create and pass to
âgawkâ to save are _copied_. This means you are responsible
- to release the storage once youâre done with it. See the
+ to release the storage once you're done with it. See the
sample âintdivâ extension for some example code.
âtypedef void *awk_scalar_t;â
@@ -26501,7 +26470,7 @@ use them.
in more detail in *note Symbol table by cookie::.
âtypedef void *awk_value_cookie_t;â
- A âvalue cookieâ is an opaque type representing a cached value.
+ A "value cookie" is an opaque type representing a cached value.
This is also discussed in a general fashion in the text following
this list, and in more detail in *note Cached values::.
@@ -26509,7 +26478,7 @@ use them.
regexps. The âawk_value_tâ struct represents values. The âval_typeâ
member indicates what is in the âunionâ.
- Representing numbers is easyâthe API uses a C âdoubleâ. Strings
+ Representing numbers is easy--the API uses a C âdoubleâ. Strings
require more work. Because âgawkâ allows embedded NUL bytes in string
values, a string must be represented as a pair containing a data pointer
and length. This is the âawk_string_tâ type.
@@ -26529,7 +26498,7 @@ The PostgreSQL âPQgetvalue()â function, for
example, returns a string
that may be numeric or textual depending on the contents.
Typed regexp values (*note Strong Regexp Constants::) are not of much
-use to extension functions. Extension functions can tell that theyâve
+use to extension functions. Extension functions can tell that they've
received them, and create them for scalar values. Otherwise, they can
examine the text of the regexp through âregex_value.strâ and
âregex_value.lenâ.
@@ -26549,7 +26518,7 @@ correctly reflects the type of the value in the
âawk_value_tâ struct.
Conceptually, the first three members of the âunionâ (number, string,
and array) are all that is needed for working with âawkâ values.
However, because the API provides routines for accessing and changing
-the value of a global scalar variable only by using the variableâs name,
+the value of a global scalar variable only by using the variable's name,
there is a performance penalty: âgawkâ must find the variable each time
it is accessed and changed. This turns out to be a real issue, not just
a theoretical one.
@@ -26557,8 +26526,8 @@ a theoretical one.
Thus, if you know that your extension will spend considerable time
reading and/or changing the value of one or more scalar variables, you
can obtain a âscalar cookieâ(1) object for that variable, and then use
-the cookie for getting the variableâs value or for changing the
-variableâs value. The âawk_scalar_tâ type holds a scalar cookie, and
+the cookie for getting the variable's value or for changing the
+variable's value. The âawk_scalar_tâ type holds a scalar cookie, and
the âscalar_cookieâ macro provides access to the value of that type in
the âawk_value_tâ struct. Given a scalar cookie, âgawkâ can directly
retrieve or modify the value, as required, without having to find it
@@ -26573,11 +26542,11 @@ running âgawkâ process and reduces the time
needed to create the value.
---------- Footnotes ----------
- (1) See the âcookieâ entry in the Jargon file
+ (1) See the "cookie" entry in the Jargon file
(http://catb.org/jargon/html/C/cookie.html) for a definition of
-âcookieâ, and the âmagic cookieâ entry in the Jargon file
+âcookieâ, and the "magic cookie" entry in the Jargon file
(http://catb.org/jargon/html/M/magic-cookie.html) for a nice example.
-See also the entry for âCookieâ in the *note Glossary::.
+See also the entry for "Cookie" in the *note Glossary::.
File: gawk.info, Node: Memory Allocation Functions, Next: Constructor
Functions, Prev: General Data Types, Up: Extension API Description
@@ -26670,13 +26639,13 @@ The functions are:
âvoid *get_mpfr_ptr();â
Allocate and initialize an MPFR object and return a pointer to it.
- If the allocation fails, âgawkâ exits with a fatal âout of memoryâ
+ If the allocation fails, âgawkâ exits with a fatal "out of memory"
error. If âgawkâ was compiled without MPFR support, calling this
function causes a fatal error.
âvoid *get_mpz_ptr();â
Allocate and initialize a GMP object and return a pointer to it.
- If the allocation fails, âgawkâ exits with a fatal âout of memoryâ
+ If the allocation fails, âgawkâ exits with a fatal "out of memory"
error. If âgawkâ was compiled without MPFR support, calling this
function causes a fatal error.
@@ -26724,7 +26693,7 @@ code would use them:
âstatic inline awk_value_t *â
âmake_null_string(awk_value_t *result);â
- This specialized function creates a null string (the âundefinedâ
+ This specialized function creates a null string (the "undefined"
value) in the âawk_value_tâ variable pointed to by âresultâ. It
returns âresultâ.
@@ -26781,7 +26750,7 @@ File: gawk.info, Node: API Ownership of MPFR and GMP
Values, Next: Registratio
-----------------------------------
MPFR and GMP values are different from string values, where you can
-âtake ownershipâ of the value simply by assigning pointers. For
+"take ownership" of the value simply by assigning pointers. For
example:
char *p = gawk_malloc(42); p ``owns'' the memory
@@ -26791,7 +26760,7 @@ example:
MPFR and GMP objects are indeed allocated on the stack or
dynamically, but the MPFR and GMP libraries treat these objects as
values, the same way that you would pass an âintâ or a âdoubleâ by
-value. There is no way to âtransfer ownershipâ of MPFR and GMP objects.
+value. There is no way to "transfer ownership" of MPFR and GMP objects.
The final results of an MPFR or GMP calculation should be passed back
to âgawkâ, by value, as you would a string or a âdoubleâ. âgawkâ
will
@@ -26864,7 +26833,7 @@ Extension functions are described by the following
record:
âawk_value_t *(*const function)(int num_actual_args,â
â awk_value_t *result,â
â struct awk_ext_func *finfo);â
- This is a pointer to the C function that provides the extensionâs
+ This is a pointer to the C function that provides the extension's
functionality. The function must fill in â*resultâ with either a
number, a string, or a regexp. âgawkâ takes ownership of any
string memory. As mentioned earlier, string memory _must_ come
@@ -26953,7 +26922,7 @@ File: gawk.info, Node: Exit Callback Functions, Next:
Extension Version String
..............................................
An âexit callbackâ function is a function that âgawkâ calls before it
-exits. Such functions are useful if you have general âcleanupâ tasks
+exits. Such functions are useful if you have general "cleanup" tasks
that should be performed in your extension (such as closing database
connections or other resource deallocations). You can register such a
function with âgawkâ using the following function:
@@ -26973,7 +26942,7 @@ function with âgawkâ using the following function:
to the function pointed to by âfuncpâ.
Exit callback functions are called in last-in, first-out (LIFO)
-orderâthat is, in the reverse order in which they are registered with
+order--that is, in the reverse order in which they are registered with
âgawkâ.
@@ -27006,7 +26975,7 @@ Files::). Additionally, it sets the value of âRTâ
(*note Built-in
Variables::).
If you want, you can provide your own custom input parser. An input
-parserâs job is to return a record to the âgawkâ record-processing code,
+parser's job is to return a record to the âgawkâ record-processing code,
along with indicators for the value and length of the data to be used
for âRTâ, if any.
@@ -27092,10 +27061,10 @@ as follows:
the file, then âfdâ will _not_ be equal to âINVALID_HANDLEâ.
Otherwise, it will.
- An extension can decide that it doesnât want to use the open file
+ An extension can decide that it doesn't want to use the open file
descriptor provided by âgawkâ. In such a case it can close the
file and set âfdâ to âINVALID_HANDLEâ, or it can leave it alone
and
- keep itâs own file descriptor in private data pointed to by the
+ keep it's own file descriptor in private data pointed to by the
âopaqueâ pointer (see further in this list). In any case, if the
file descriptor is valid, it should _not_ just overwrite the value
with something else; doing so would cause a resource leak.
@@ -27106,14 +27075,14 @@ as follows:
if the âlstat()â system call is available, it will use that. If
âlstat()â is not available, then it uses âstat()â.
- Getting the fileâs information allows extensions to check the type
+ Getting the file's information allows extensions to check the type
of the file even if it could not be opened. This occurs, for
example, on Windows systems when trying to use âopen()â on a
directory.
If âgawkâ was not able to get the file information, then âsbufâ
will be zeroed out. In particular, extension code can check if
- âsbuf.st_mode == 0â. If thatâs true, then there is no information
+ âsbuf.st_mode == 0â. If that's true, then there is no information
in âsbufâ.
The âXXX_can_take_file()â function should examine these fields and
@@ -27132,7 +27101,7 @@ may be filled by âXXX_take_control_of()â:
âvoid *opaque;â
This is used to hold any state information needed by the input
- parser for this file. It is âopaqueâ to âgawkâ. The input parser
+ parser for this file. It is "opaque" to âgawkâ. The input parser
is not required to use this pointer.
âint (*get_record)(char **out,â
@@ -27153,14 +27122,14 @@ may be filled by âXXX_take_control_of()â:
âvoid (*close_func)(struct awk_input *iobuf);â
This function pointer should point to a function that does the
- âteardown.â It should release any resources allocated by
+ "teardown." It should release any resources allocated by
âXXX_take_control_of()â. It may also close the file. If it does
so, it should set the âfdâ field to âINVALID_HANDLEâ.
If âfdâ is still not âINVALID_HANDLEâ after the call to this
function, âgawkâ calls the regular âclose()â system call.
- Having a âteardownâ function is optional. If your input parser
+ Having a "teardown" function is optional. If your input parser
does not need it, do not set this field. Then, âgawkâ calls the
regular âclose()â system call on the file descriptor, so it should
be valid.
@@ -27184,7 +27153,7 @@ records. The parameters are as follows:
âchar **rt_startâ
âsize_t *rt_lenâ
- If the concept of a ârecord terminatorâ makes sense, then
+ If the concept of a "record terminator" makes sense, then
â*rt_startâ should be set to point to the data to be used for
âRTâ,
and â*rt_lenâ should be set to the length of the data. Otherwise,
â*rt_lenâ should be set to zero. Here too, âgawkâ makes its own
@@ -27381,7 +27350,7 @@ in the âawk_output_buf_tâ. The data members are as
follows:
These pointers should be set to point to functions that perform the
equivalent function as the â<stdio.h>â functions do, if
appropriate. âgawkâ uses these function pointers for all output.
- âgawkâ initializes the pointers to point to internal
âpass-throughâ
+ âgawkâ initializes the pointers to point to internal "pass-through"
functions that just call the regular â<stdio.h>â functions, so an
extension only needs to redefine those functions that are
appropriate for what it does.
@@ -27393,7 +27362,7 @@ file for writing. The âfpâ member will be
âNULLâ only if it fails.
When âgawkâ calls âXXX_take_control_of()â, that function should fill
in the other fields as appropriate, except for âfpâ, which it should
-just use normally if itâs not âNULLâ.
+just use normally if it's not âNULLâ.
You register your output wrapper with the following function:
@@ -27445,8 +27414,8 @@ structures as described earlier.
This is for use by âgawkâ; therefore it is marked âawk_constâ so
that the extension cannot modify it.
- As with the input parser and output processor, you provide âyes I can
-take thisâ and âtake over for thisâ functions,
âXXX_can_take_two_way()â
+ As with the input parser and output processor, you provide "yes I can
+take this" and "take over for this" functions, âXXX_can_take_two_way()â
and âXXX_take_control_of()â.
You register your two-way processor with the following function:
@@ -27475,7 +27444,7 @@ extension ID received from âgawkâ when the
extension was loaded:(1)
Print a warning message.
âvoid lintwarn(awk_ext_id_t id, const char *format, ...);â
- Print a âlint warning.â Normally this is the same as printing a
+ Print a "lint warning." Normally this is the same as printing a
warning message, but if âgawkâ was invoked with â--lint=fatalâ,
then lint warnings become fatal error messages.
@@ -27486,7 +27455,7 @@ characters and formatting codes intermixed.
---------- Footnotes ----------
(1) Because the API uses only ISO C 90 features, it cannot make use
-of the ISO C 99 variadic macro feature to hide that parameter. Moreâs
+of the ISO C 99 variadic macro feature to hide that parameter. More's
the pity.
@@ -27525,7 +27494,6 @@ of the actual value. You may then print an error
message or reissue the
request for the actual value type, as appropriate. This behavior is
summarized in *note Table 17.2: table-value-types-returned.
-
Type of Actual Value
--------------------------------------------------------------------------
String Strnum Number Regex Bool Array
Undefined
@@ -27559,14 +27527,14 @@ your extension function. They are:
âcountâth argument. Return true if the actual type matches
âwantedâ, and false otherwise. In the latter case,
âresult->val_typeâ indicates the actual type (*note Table 17.2:
- table-value-types-returned.). Counts are zero-basedâthe first
+ table-value-types-returned.). Counts are zero-based--the first
argument is numbered zero, the second one, and so on. âwantedâ
indicates the type of value expected.
âawk_bool_t set_argument(size_t count, awk_array_t array);â
Convert a parameter that was undefined into an array; this provides
call by reference for arrays. Return false if âcountâ is too big,
- or if the argumentâs type is not undefined. *Note Array
+ or if the argument's type is not undefined. *Note Array
Manipulation:: for more information on creating arrays.
@@ -27581,7 +27549,7 @@ allows you to create and release cached values.
* Menu:
* Symbol table by name:: Accessing variables by name.
-* Symbol table by cookie:: Accessing variables by âcookieâ.
+* Symbol table by cookie:: Accessing variables by "cookie".
* Cached values:: Creating and using cached values.
@@ -27592,7 +27560,7 @@ File: gawk.info, Node: Symbol table by name, Next:
Symbol table by cookie, Up
The following routines provide the ability to access and update global
âawkâ-level variables by name. In compiler terminology, identifiers of
-different kinds are termed âsymbolsâ, thus the âsymâ in the routinesâ
+different kinds are termed âsymbolsâ, thus the "sym" in the routines'
names. The data structure that stores information about symbols is
termed a âsymbol tableâ. The functions are as follows:
@@ -27620,7 +27588,7 @@ termed a âsymbol tableâ. The functions are as
follows:
âawk_bool_t sym_update(const char *name, awk_value_t *value);â
Update the variable named by the string ânameâ, which is a regular
- C string. The variable is added to âgawkââs symbol table if it is
+ C string. The variable is added to âgawkâ's symbol table if it is
not there. Return true if everything worked, and false otherwise.
Changing types (scalar to array or vice versa) of an existing
@@ -27634,7 +27602,7 @@ termed a âsymbol tableâ. The functions are as
follows:
cannot be âNULLâ. If it is â""â or â"awk"â, then ânameâ
is
searched for in the default âawkâ namespace.
- An extension can look up the value of âgawkââs special variables.
+ An extension can look up the value of âgawkâ's special variables.
However, with the exception of the âPROCINFOâ array, an extension cannot
change any of those variables.
@@ -27656,7 +27624,7 @@ File: gawk.info, Node: Symbol table by cookie, Next:
Cached values, Prev: Sym
A âscalar cookieâ is an opaque handle that provides access to a global
variable or array. It is an optimization that avoids looking up
-variables in âgawkââs symbol table every time access is needed. This
+variables in âgawkâ's symbol table every time access is needed. This
was discussed earlier, in *note General Data Types::.
The following functions let you work with scalar cookies:
@@ -27676,7 +27644,7 @@ was discussed earlier, in *note General Data Types::.
may not be updated.
It is not obvious at first glance how to work with scalar cookies or
-what their raison dâêtre really is. In theory, the âsym_lookup()â and
+what their raison d'être really is. In theory, the âsym_lookup()â and
âsym_update()â routines are all you really need to work with variables.
For example, you might have code that looks up the value of a variable,
evaluates a condition, and then possibly changes the value of the
@@ -27698,7 +27666,7 @@ variable based on the result of that evaluation, like
so:
return make_number(0.0, result);
}
-This code looks (and is) simple and straightforward. So whatâs the
+This code looks (and is) simple and straightforward. So what's the
problem?
Well, consider what happens if âawkâ-level code associated with your
@@ -27709,10 +27677,10 @@ symbol table once or twice per function call!
The symbol table lookup is really pure overhead; it is considerably
more efficient to get a cookie that represents the variable, and use
-that to get the variableâs value and update it as needed.(1)
+that to get the variable's value and update it as needed.(1)
Thus, the way to use cookies is as follows. First, install your
-extensionâs variable in âgawkââs symbol table using
âsym_update()â, as
+extension's variable in âgawkâ's symbol table using âsym_update()â, as
usual. Then get a scalar cookie for the variable using âsym_lookup()â:
static awk_scalar_t magic_var_cookie; /* cookie for MAGIC_VAR */
@@ -27775,7 +27743,7 @@ necessary. You can create numbers and strings using
the functions in
variables using âsym_update()â or âsym_update_scalar()â, as you like.
However, you can understand the point of cached values if you
-remember that _every_ string valueâs storage _must_ come from
+remember that _every_ string value's storage _must_ come from
âgawk_malloc()â, âgawk_calloc()â, or âgawk_realloc()â. If you
have 20
variables, all of which have the same string value, you must create 20
identical copies of the string.(1)
@@ -27839,14 +27807,14 @@ of variables:
Using value cookies in this way saves considerable storage, as all of
âVAR1â through âVAR100â share the same value.
- You might be wondering, âIs this sharing problematic? What happens
+ You might be wondering, "Is this sharing problematic? What happens
if âawkâ code assigns a new value to âVAR1â; are all the others changed
-too?â
+too?"
- Thatâs a great question. The answer is that no, itâs not a problem.
+ That's a great question. The answer is that no, it's not a problem.
Internally, âgawkâ uses âreference-counted stringsâ. This means that
many variables can share the same string value, and âgawkâ keeps track
-of the usage. When a variableâs value changes, âgawkâ simply decrements
+of the usage. When a variable's value changes, âgawkâ simply decrements
the reference count on the old value and updates the variable to use the
new value.
@@ -27870,7 +27838,7 @@ The primary data structure(1) in âawkâ is the
associative array (*note
Arrays::). Extensions need to be able to manipulate âawkâ arrays. The
API provides a number of data structures for working with arrays,
functions for working with individual elements, and functions for
-working with arrays as a whole. This includes the ability to âflattenâ
+working with arrays as a whole. This includes the ability to "flatten"
an array so that it is easy for C code to traverse every element in an
array. The array data structures integrate nicely with the data
structures for values to make it easy to both work with and create true
@@ -27913,7 +27881,7 @@ The data types associated with arrays are as follows:
â awk_value_t index;â
â awk_value_t value;â
â} awk_element_t;â
- The âawk_element_tâ is a âflattenedâ array element. âawkâ
produces
+ The âawk_element_tâ is a "flattened" array element. âawkâ
produces
an array of these inside the âawk_flat_array_tâ (see the next
item). Individual elements may be marked for deletion. New
elements must be added individually, one at a time, using the
@@ -27951,7 +27919,7 @@ The data types associated with arrays are as follows:
---------- Footnotes ----------
- (1) It is also a âcookie,â but the âgawkâ developers did not wish to
+ (1) It is also a "cookie," but the âgawkâ developers did not wish to
overuse this term.
@@ -28167,7 +28135,7 @@ second argument is numbered one:
goto out;
}
- The fifth step is where the âreal workâ is done. The function loops
+ The fifth step is where the "real work" is done. The function loops
over every element in the array, printing the index and element values.
In addition, upon finding the element with the index that is supposed to
be deleted, the function sets the âAWK_ELEMENT_DELETEâ bit in the
@@ -28237,7 +28205,7 @@ and manipulate them.
There are two important points about creating arrays from extension
code:
- ⢠You must install a new array into âgawkââs symbol table
immediately
+ ⢠You must install a new array into âgawkâ's symbol table immediately
upon creating it. Once you have done so, you can then populate the
array.
@@ -28245,8 +28213,8 @@ code:
array, you must add the new array to its parent before adding any
elements to it.
- Thus, the correct way to build an array is to work âtop down.â
- Create the array, and immediately install it in âgawkââs symbol
+ Thus, the correct way to build an array is to work "top down."
+ Create the array, and immediately install it in âgawkâ's symbol
table using âsym_update()â, or install it as an element in a
previously existing array using âset_array_element()â. We show
example code shortly.
@@ -28378,7 +28346,7 @@ redirections.
â int fd,â
â const awk_input_buf_t **ibufp,â
â const awk_output_buf_t **obufp);â
- Look up file ânameâ in âgawkââs internal redirection table. If
+ Look up file ânameâ in âgawkâ's internal redirection table. If
ânameâ is âNULLâ or âname_lenâ is zero, return data for the
currently open input file corresponding to âFILENAMEâ. (This does
not access the âfiletypeâ argument, so that may be undefined). If
@@ -28417,7 +28385,7 @@ redirections.
and the âfdâ argument is nonnegative, âgawkâ will use that file
descriptor instead of opening the file in the usual way. If âfdâ
is nonnegative, but the file exists already, âgawkâ ignores âfdâ
- and returns the existing file. It is the callerâs responsibility
+ and returns the existing file. It is the caller's responsibility
to notice that neither the âfdâ in the returned âawk_input_buf_tâ
nor the âfdâ in the returned âawk_output_buf_tâ matches the
requested value.
@@ -28449,7 +28417,7 @@ information about how âgawkâ was invoked.
* Extension Versioning:: API Version information.
* Extension GMP/MPFR Versioning:: Version information about GMP and MPFR.
* Extension API Informational Variables:: Variables providing information about
- âgawkââs invocation.
+ âgawkâ's invocation.
File: gawk.info, Node: Extension Versioning, Next: Extension GMP/MPFR
Versioning, Up: Extension API Variables
@@ -28457,12 +28425,11 @@ File: gawk.info, Node: Extension Versioning, Next:
Extension GMP/MPFR Versioni
17.4.14.1 API Version Constants and Variables
.............................................
-The API provides both a âmajorâ and a âminorâ version number. The API
+The API provides both a "major" and a "minor" version number. The API
versions are available at compile time as C preprocessor defines to
support conditional compilation, and as enum constants to facilitate
debugging:
-
API Version C Preprocessor Define enum constant
--------------------------------------------------------------------
Major âgawk_api_major_versionâ âGAWK_API_MAJOR_VERSIONâ
@@ -28540,7 +28507,7 @@ match those of âgawkâ with the following macro:
If you have included that file, then this macro compares the MPFR
and GMP major and minor versions against those of the library you
- are compiling against. If your libraries are newer than âgawkââs,
+ are compiling against. If your libraries are newer than âgawkâ's,
it produces a fatal error message.
The âdl_load_func()â macro (*note Extension API Boilerplate::)
@@ -28661,7 +28628,7 @@ the âgawkapi.hâ header file:
function should return âawk_falseâ upon failure, or âawk_trueâ if
everything goes well.
- If you donât need to do any initialization, define the pointer and
+ If you don't need to do any initialization, define the pointer and
initialize it to âNULLâ.
âdl_load_func(func_table, some_name, "name_space_in_quotes")â
@@ -28673,8 +28640,8 @@ function (from the âdl_load_func()â macro) do all
the standard work. It
does the following:
1. Check the API versions. If the extension major version does not
- match âgawkââs, or if the extension minor version is greater than
- âgawkââs, it prints a fatal error message and exits.
+ match âgawkâ's, or if the extension minor version is greater than
+ âgawkâ's, it prints a fatal error message and exits.
2. Check the MPFR and GMP versions. If there is a mismatch, it prints
a fatal error message and exits.
@@ -28699,7 +28666,7 @@ You will have to recompile your extensions in order to
use them with the
current version of âgawkâ.
Fortunately, at the possible expense of some compile-time warnings,
-the API remains source-codeâcompatible with the previous API. The major
+the API remains source-code-compatible with the previous API. The major
differences are the additional members in the âawk_ext_func_tâ
structure, and the addition of the third argument to the C
implementation function (*note Extension Functions::).
@@ -28749,7 +28716,7 @@ File: gawk.info, Node: Extension Example, Next:
Extension Samples, Prev: Find
=================================
No matter where you go, there you are.
- â _Buckaroo Banzai_
+ -- _Buckaroo Banzai_
Two useful functions that are not in âawkâ are âchdir()â (so that an
âawkâ program can change its directory) and âstat()â (so that an
âawkâ
@@ -28770,7 +28737,7 @@ File: gawk.info, Node: Internal File Description,
Next: Internal File Ops, Up
-----------------------------------
This minor node shows how to use the new functions at the âawkâ level
-once theyâve been integrated into the running âgawkâ interpreter. Using
+once they've been integrated into the running âgawkâ interpreter. Using
âchdir()â is very straightforward. It takes one argument, the new
directory to change to:
@@ -28809,10 +28776,10 @@ appropriate information:
â"dev"â
â"ino"â
- The fileâs device and inode numbers, respectively.
+ The file's device and inode numbers, respectively.
â"mode"â
- The fileâs mode, as a numeric value. This includes both the fileâs
+ The file's mode, as a numeric value. This includes both the file's
type and its permissions.
â"nlink"â
@@ -28820,34 +28787,34 @@ appropriate information:
â"uid"â
â"gid"â
- The numeric user and group ID numbers of the fileâs owner.
+ The numeric user and group ID numbers of the file's owner.
â"size"â
The size in bytes of the file.
â"blocks"â
The number of disk blocks the file actually occupies. This may not
- be a function of the fileâs size if the file has holes.
+ be a function of the file's size if the file has holes.
â"atime"â
â"mtime"â
â"ctime"â
- The fileâs last access, modification, and inode update times,
+ The file's last access, modification, and inode update times,
respectively. These are numeric timestamps, suitable for
formatting with âstrftime()â (*note Time Functions::).
â"pmode"â
- The fileâs âprintable mode.â This is a string representation of the
- fileâs type and permissions, such as is produced by âls -lââfor
- example, â"drwxr-xr-x"â.
+ The file's "printable mode." This is a string representation of
+ the file's type and permissions, such as is produced by âls
+ -lâ--for example, â"drwxr-xr-x"â.
â"type"â
- A printable string representation of the fileâs type. The value is
+ A printable string representation of the file's type. The value is
one of the following:
â"blockdev"â
â"chardev"â
- The file is a block or character device (âspecial fileâ).
+ The file is a block or character device ("special file").
â"directory"â
The file is a directory.
@@ -28859,7 +28826,7 @@ appropriate information:
The file is just a regular file.
â"socket"â
- The file is an âAF_UNIXâ (âUnix domainâ) socket in the
+ The file is an âAF_UNIXâ ("Unix domain") socket in the
filesystem.
â"symlink"â
@@ -29196,7 +29163,7 @@ done, the function returns the result from
âfill_stat_array()â:
return make_number(ret, result);
}
- Finally, itâs necessary to provide the âglueâ that loads the new
+ Finally, it's necessary to provide the "glue" that loads the new
function(s) into âgawkâ.
The âfilefuncsâ extension also provides an âfts()â function, which
we
@@ -29228,7 +29195,7 @@ everything that needs to be loaded. It is simplest to
use the
dl_load_func(func_table, filefuncs, "")
- And thatâs it!
+ And that's it!
---------- Footnotes ----------
@@ -29400,7 +29367,7 @@ follows. The usage is:
â"linkval"â The value of the symbolic link Symbolic
links
â"type"â The type of the file as a All
- stringâone of â"file"â,
+ string--one of â"file"â,
â"blockdev"â, â"chardev"â,
â"directory"â, â"socket"â,
â"fifo"â, â"symlink"â, â"door"â,
@@ -29433,13 +29400,13 @@ requested hierarchies.
value and sets âERRNOâ. The flags are:
âFTS_LOGICALâ
- Do a âlogicalâ file traversal, where the information returned
+ Do a "logical" file traversal, where the information returned
for a symbolic link refers to the linked-to file, and not to
the symbolic link itself. This flag is mutually exclusive
with âFTS_PHYSICALâ.
âFTS_PHYSICALâ
- Do a âphysicalâ file traversal, where the information returned
+ Do a "physical" file traversal, where the information returned
for a symbolic link refers to the symbolic link itself. This
flag is mutually exclusive with âFTS_LOGICALâ.
@@ -29473,7 +29440,7 @@ requested hierarchies.
In this case, the array contains two or three elements:
â"path"â
- The full path to this file, starting from the ârootâ that
+ The full path to this file, starting from the "root" that
was given in the âpathlistâ array.
â"stat"â
@@ -29611,8 +29578,8 @@ File: gawk.info, Node: Extension Sample Inplace,
Next: Extension Sample Ord,
17.7.4 Enabling In-Place File Editing
-------------------------------------
-The âinplaceâ extension emulates GNU âsedââs â-iâ option, which
performs
-âin-placeâ editing of each input file. It uses the bundled
+The âinplaceâ extension emulates GNU âsedâ's â-iâ option, which
performs
+"in-place" editing of each input file. It uses the bundled
âinplace.awkâ include file to invoke the extension properly. This
extension makes use of the namespace facility to place all the variables
and functions in the âinplaceâ namespace (*note Namespaces::):
@@ -29743,7 +29710,6 @@ the third field is a single letter indicating the type
of the file. The
letters and their corresponding file types are shown in *note Table
17.4: table-readdir-file-types.
-
Letter File type
--------------------------------------------------------------------------
âbâ Block device
@@ -29760,7 +29726,7 @@ Table 17.4: File types returned by the âreaddirâ
extension
third field is filled in from that information. On systems without the
file type information, the extension falls back to calling the âstat()â
system call in order to provide the information. Thus the third field
-should never be âuâ (for âunknownâ).
+should never be âuâ (for "unknown").
Normally, when reading directories, you should set âFSâ equal to
â"/"â. However, you may instead chose to create
@@ -29968,7 +29934,7 @@ The âtimeâ extension adds three functions, named
âgettimeofday()â
âmktime()â function, and its result is returned, expressing the
time in seconds since the epoch in the current local timezone,
regardless of any timezone specified in the string arguments.
- (This is the same as âgawkââs built-in âsystime()â function.)
+ (This is the same as âgawkâ's built-in âsystime()â function.)
Otherwise it returns â1 upon error. In the latter case,
Note that the underlying âstrptime()â C library routine apparently
@@ -30010,7 +29976,7 @@ are:
C.
⢠MPFR library extension. This provides access to a number of MPFR
- functions that âgawkââs native MPFR support does not.
+ functions that âgawkâ's native MPFR support does not.
⢠Select extension. It provides functionality based on the
âselect()â system call.
@@ -30054,7 +30020,7 @@ upon how your system works.
If you write an extension that you wish to share with other âgawkâ
users, consider doing so through the âgawkextlibâ project. See the
-projectâs website for more information.
+project's website for more information.
File: gawk.info, Node: Extension summary, Next: Extension Exercises, Prev:
gawkextlib, Up: Dynamic Extensions
@@ -30076,7 +30042,7 @@ File: gawk.info, Node: Extension summary, Next:
Extension Exercises, Prev: ga
âgawkâ via the supplied function pointers to accomplish certain
tasks.
- ⢠One of these tasks is to âregisterâ the name and implementation of
+ ⢠One of these tasks is to "register" the name and implementation of
new âawkâ-level functions with âgawkâ. The implementation takes
the form of a C function pointer with a defined signature. By
convention, implementation functions are named âdo_XXXX()â for some
@@ -30095,7 +30061,7 @@ File: gawk.info, Node: Extension summary, Next:
Extension Exercises, Prev: ga
exit callbacks, a version string, input parsers, output
wrappers, and two-way processors)
- ⢠Printing fatal, nonfatal, warning, and âlintâ warning messages
+ ⢠Printing fatal, nonfatal, warning, and "lint" warning messages
⢠Updating âERRNOâ, or unsetting it
@@ -30127,7 +30093,7 @@ File: gawk.info, Node: Extension summary, Next:
Extension Exercises, Prev: ga
read-only by the extension.
⢠_All_ memory passed from an extension to âgawkâ must come from the
- APIâs memory allocation functions. âgawkâ takes responsibility for
+ API's memory allocation functions. âgawkâ takes responsibility for
the memory and releases it when appropriate.
⢠The API provides information about the running version of âgawkâ so
@@ -30155,7 +30121,7 @@ File: gawk.info, Node: Extension Exercises, Prev:
Extension summary, Up: Dyna
in *note Internal File Ops::.
2. Write an input parser that prints a prompt if the input is a from a
- âterminalâ device. You can use the âisatty()â function to tell if
+ "terminal" device. You can use the âisatty()â function to tell if
the input file is a terminal. (Hint: this function is usually
expensive to call; try to call it just once.) The content of the
prompt should come from a variable settable by âawkâ-level code.
@@ -30169,7 +30135,7 @@ File: gawk.info, Node: Extension Exercises, Prev:
Extension summary, Up: Dyna
the one to get a record, or the one to read raw bytes?
3. Write a wrapper script that provides an interface similar to âsed
- -iâ for the âinplaceâ extension presented in *note Extension Sample
+ -iâ for the "inplace" extension presented in *note Extension Sample
Inplace::.
@@ -30195,7 +30161,7 @@ where you can find more information.
* SVR4:: Minor changes between System V Releases 3.1
and 4.
* POSIX:: New features from the POSIX standard.
-* BTL:: New features from Brian Kernighanâs version
of
+* BTL:: New features from Brian Kernighan's version of
âawkâ.
* POSIX/GNU:: The extensions in âgawkâ not in POSIX
âawkâ.
@@ -30353,7 +30319,7 @@ permitted by the POSIX standard.
File: gawk.info, Node: BTL, Next: POSIX/GNU, Prev: POSIX, Up: Language
History
-A.4 Extensions in Brian Kernighanâs âawkâ
+A.4 Extensions in Brian Kernighan's âawkâ
=========================================
Brian Kernighan has made his version available via his home page (*note
@@ -30452,7 +30418,7 @@ current version of âgawkâ.
â Positional specifiers in âprintfâ formats for making
translations easier (*note Printf Ordering::)
- â The âsplit()â functionâs additional optional fourth argument,
+ â The âsplit()â function's additional optional fourth argument,
which is an array to hold the text of the field separators
(*note String Functions::)
@@ -30673,7 +30639,7 @@ POSIX âawkâ, in the order they were added to
âgawkâ.
â âPROCINFOâ, an array for providing process-related
information.
- â âTEXTDOMAINâ, for setting an applicationâs
+ â âTEXTDOMAINâ, for setting an application's
internationalization text domain (*note
Internationalization::).
@@ -30738,13 +30704,13 @@ POSIX âawkâ, in the order they were added to
âgawkâ.
(*note Profiling::).
â The â--use-lc-numericâ option to force âgawkâ to use the
- localeâs decimal point for parsing input data (*note
+ locale's decimal point for parsing input data (*note
Conversion::).
⢠The use of GNU Automake to help in standardizing the configuration
process (*note Quick Installation::).
- ⢠The use of GNU âgettextâ for âgawkââs own message output
(*note
+ ⢠The use of GNU âgettextâ for âgawkâ's own message output (*note
Gawk I18N::).
⢠BeOS support. This was later removed.
@@ -30943,7 +30909,7 @@ POSIX âawkâ, in the order they were added to
âgawkâ.
Version 4.2 of âgawkâ introduced the following changes:
- ⢠Changes to âENVIRONâ are reflected into âgawkââs environment
and
+ ⢠Changes to âENVIRONâ are reflected into âgawkâ's environment and
that of programs that it runs. *Note Auto-set::.
⢠âFIELDWIDTHSâ was enhanced to allow skipping characters before
@@ -31038,7 +31004,7 @@ unfortunately. It added the following features:
⢠Several example programs in the manual were updated to their modern
POSIX equivalents.
- ⢠The âno effectâ lint warnings from â--lintâ were fixed up and
now
+ ⢠The "no effect" lint warnings from â--lintâ were fixed up and now
behave more sanely (*note Options::).
⢠Handling of Infinity and NaN values were improved. *Note Math
@@ -31056,7 +31022,7 @@ unfortunately. It added the following features:
⢠The âgawkbugâ script for reporting bugs (*note Bug address::).
- ⢠Terence Kellyâs persistent memory allocator (PMA) was added,
+ ⢠Terence Kelly's persistent memory allocator (PMA) was added,
allowing the use of persistent data on certain systems (*note
Persistent Memory::).
@@ -31090,7 +31056,7 @@ A.7 Common Extensions Summary
=============================
The following table summarizes the common extensions supported by
-âgawkâ, Brian Kernighanâs âawkâ, and âmawkâ, the three most
widely used
+âgawkâ, Brian Kernighan's âawkâ, and âmawkâ, the three most widely
used
freely available versions of âawkâ (*note Other Versions::).
Feature BWK âawkâ âmawkâ âgawkâ Now
standard
@@ -31126,7 +31092,7 @@ different versions of âgawkâ.
character ranges (such as â[a-z]â) to match any character between the
first character in the range and the last character in the range,
inclusive. Ordering was based on the numeric value of each character in
-the machineâs native character set. Thus, on ASCII-based systems,
+the machine's native character set. Thus, on ASCII-based systems,
â[a-z]â matched all the lowercase letters, and only the lowercase
letters, as the numeric values for the letters from âaâ through âzâ
were
contiguous. (On an EBCDIC system, the range â[a-z]â includes additional
@@ -31134,8 +31100,8 @@ nonalphabetic characters as well.)
Almost all introductory Unix literature explained range expressions
as working in this fashion, and in particular, would teach that the
-âcorrectâ way to match lowercase letters was with â[a-z]â, and that
-â[A-Z]â was the âcorrectâ way to match uppercase letters. And indeed,
+"correct" way to match lowercase letters was with â[a-z]â, and that
+â[A-Z]â was the "correct" way to match uppercase letters. And indeed,
this was true.(1)
The 1992 POSIX standard introduced the idea of locales (*note
@@ -31183,12 +31149,12 @@ locale-aware, so ranges had their traditional
interpretation.
When âgawkâ switched to using locale-aware regexp matchers, the
problems began; especially as both GNU/Linux and commercial Unix vendors
started implementing non-ASCII locales, _and making them the default_.
-Perhaps the most frequently asked question became something like, âWhy
-does â[A-Z]â match lowercase letters?!?â
+Perhaps the most frequently asked question became something like, "Why
+does â[A-Z]â match lowercase letters?!?"
This situation existed for close to 10 years, if not more, and the
âgawkâ maintainer grew weary of trying to explain that âgawkâ was being
-nicely standards-compliant, and that the issue was in the userâs locale.
+nicely standards-compliant, and that the issue was in the user's locale.
During the development of version 4.0, he modified âgawkâ to always
treat ranges in the original, pre-POSIX fashion, unless â--posixâ was
used (*note Options::).(2)
@@ -31210,8 +31176,8 @@ In all cases âgawkâ remains POSIX-compliant.
(2) And thus was born the Campaign for Rational Range Interpretation
(or RRI). A number of GNU tools have already implemented this change, or
-will soon. Thanks to Karl Berry for coining the phrase âRational Range
-Interpretation.â
+will soon. Thanks to Karl Berry for coining the phrase "Rational Range
+Interpretation."
(3) See the standard
(https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05)
@@ -31225,7 +31191,7 @@ A.9 Major Contributors to âgawkâ
================================
Always give credit where credit is due.
- â _Anonymous_
+ -- _Anonymous_
This minor node names the major contributors to âgawkâ and/or this
Info file, in approximate chronological order:
@@ -31250,7 +31216,7 @@ Info file, in approximate chronological order:
initial version of âgawkâ.
⢠In 1988, David Trueman took over primary maintenance of âgawkâ,
- making it compatible with ânewâ âawkâ, and greatly improving its
+ making it compatible with "new" âawkâ, and greatly improving its
performance.
⢠Conrad Kwok, Scott Garfinkle, and Kent Williams did the initial
@@ -31270,7 +31236,7 @@ Info file, in approximate chronological order:
sure âgawkâ works on non-32-bit systems.
⢠Fred Fish provided the port to Amiga systems and its documentation.
- (With Fredâs sad passing, this is no longer supported.)
+ (With Fred's sad passing, this is no longer supported.)
⢠Scott Deifik formerly maintained the MS-DOS port using DJGPP.
@@ -31300,7 +31266,7 @@ Info file, in approximate chronological order:
the work enabling the pretty-printer to preserve and output
comments.
- ⢠Matthew Woehlke provided improvements for Tandemâs POSIX-compliant
+ ⢠Matthew Woehlke provided improvements for Tandem's POSIX-compliant
systems.
⢠Martin Brown provided the port to BeOS and its documentation.
@@ -31370,7 +31336,7 @@ Info file, in approximate chronological order:
⢠Juan Manuel Guerrero took over maintenance of the DJGPP port.
- ⢠âJannickâ provided support for MSYS2.
+ ⢠"Jannick" provided support for MSYS2.
⢠Arnold Robbins has been working on âgawkâ since 1988, at first
helping David Trueman, and as the primary maintainer since around
@@ -31389,7 +31355,7 @@ A.10 Summary
1989. Since then, further minor changes have happened under the
auspices of the POSIX standard.
- ⢠Brian Kernighanâs âawkâ provides a small number of extensions that
+ ⢠Brian Kernighan's âawkâ provides a small number of extensions that
are implemented in common with other versions of âawkâ.
⢠âgawkâ provides a large number of extensions over POSIX âawkâ.
@@ -31399,7 +31365,7 @@ A.10 Summary
⢠The interaction of POSIX locales and regexp matching in âgawkâ has
been confusing over the years. Today, âgawkâ implements Rational
Range Interpretation, where ranges of the form â[a-z]â match _only_
- the characters numerically between âaâ through âzâ in the
machineâs
+ the characters numerically between âaâ through âzâ in the
machine's
native character set. Usually this is ASCII, but it can be EBCDIC
on IBM S/390 systems.
@@ -31502,8 +31468,8 @@ release of version V, and the P represents a âpatch
levelâ, meaning that
minor bugs have been fixed in the release. The current patch level is
0, but when retrieving distributions, you should get the version with
the highest version, release, and patch level. (Note, however, that
-patch levels greater than or equal to 60 denote âbetaâ or nonproduction
-software; you might not want to retrieve such a version unless you donât
+patch levels greater than or equal to 60 denote "beta" or nonproduction
+software; you might not want to retrieve such a version unless you don't
mind experimenting.) If you are not on a Unix or GNU/Linux system, you
need to make other arrangements for getting and extracting the âgawkâ
distribution. You should consult a local expert.
@@ -31578,7 +31544,7 @@ Various â.câ, â.yâ, and â.hâ files
programming.
âdoc/bc_notesâ
- A brief description of âgawkââs âbyte codeâ internals.
+ A brief description of âgawkâ's "byte code" internals.
âdoc/README.cardâ
âdoc/ad.blockâ
@@ -31738,7 +31704,7 @@ for your system yourself.
* Quick Installation:: Compiling âgawkâ under Unix.
* Shell Startup Files:: Shell convenience functions.
* Additional Configuration Options:: Other compile-time options.
-* Configuration Philosophy:: How itâs all supposed to work.
+* Configuration Philosophy:: How it's all supposed to work.
* Compiling from Git:: Compiling from Git.
* Building the Documentation:: Building the Documentation.
@@ -31787,13 +31753,13 @@ type:
make
Shortly thereafter, you should have an executable version of âgawkâ.
-Thatâs all there is to it! To verify that âgawkâ is working properly,
+That's all there is to it! To verify that âgawkâ is working properly,
run âmake checkâ. All of the tests should succeed. If these steps do
not work, or if any of the tests fail, check the files in the âREADME_dâ
-directory to see if youâve found a known problem. If the failure is not
+directory to see if you've found a known problem. If the failure is not
described there, send in a bug report (*note Bugs::).
- Of course, once youâve built âgawkâ, it is likely that you will wish
+ Of course, once you've built âgawkâ, it is likely that you will wish
to install it. To do so, you need to run the command âmake installâ, as
a user with the appropriate permissions. How to do this varies by
system, but on many systems you can use the âsudoâ command to do so.
@@ -31877,7 +31843,7 @@ command line when compiling âgawkâ from scratch,
including:
do nothing. Similarly, setting the âLINTâ variable (*note
User-modified::) has no effect on the running âawkâ program.
- When used with the GNU Compiler Collectionâs (GCCâs) automatic
+ When used with the GNU Compiler Collection's (GCC's) automatic
dead-code-elimination, this option cuts almost 23K bytes off the
size of the âgawkâ executable on GNU/Linux x86_64 systems. Results
on other systems and with other compilers are likely to vary.
@@ -31941,7 +31907,7 @@ undefined.
so by not exiting with an error when a library function is not
available. To get around this, edit the âcustom.hâ file. Use an
â#ifdefâ that is appropriate for your system, and either â#defineâ any
-constants that âconfigureâ should have defined but didnât, or
â#undefâ
+constants that âconfigureâ should have defined but didn't, or â#undefâ
any constants that âconfigureâ defined and should not have. The
âcustom.hâ file is automatically included by the âconfig.hâ file.
@@ -32028,7 +31994,7 @@ B.3.1 Installation on MS-Windows
This minor node covers installation and usage of âgawkâ on Intel
architecture machines running any version of MS-Windows. In this minor
-node, the term âWindows32â refers to any of Microsoft Windows
+node, the term "Windows32" refers to any of Microsoft Windows
95/98/ME/NT/2000/XP/Vista/7/8/10/11.
See also the âREADME_d/README.pcâ file in the distribution.
@@ -32049,15 +32015,15 @@ B.3.1.1 Installing a Prepared Distribution for
MS-Windows Systems
.................................................................
The only supported binary distribution for MS-Windows systems is that
-provided by Eli Zaretskiiâs âezwinportsâ
+provided by Eli Zaretskii's "ezwinports"
(https://sourceforge.net/projects/ezwinports/) project. Install the
compiled âgawkâ from there. Note that to run that port, you need to
have the âlibgcc_s_dw2-1.dllâ file installed on your system. This file
is part of the GCC distribution, and should reside either in the same
-directory where you install âgawk.exeâ or somewhere on your systemâs
+directory where you install âgawk.exeâ or somewhere on your system's
âPathâ. You can download this file from the MinGW site
-(https://osdn.net/projects/mingw/releases); look under the âMinGW.org
-Compiler Collection (GCC)â for the âLibGCC-1.DLLâ download.
+(https://osdn.net/projects/mingw/releases); look under the "MinGW.org
+Compiler Collection (GCC)" for the âLibGCC-1.DLLâ download.
File: gawk.info, Node: PC Compiling, Next: PC Using, Prev: PC Binary
Installation, Up: PC Installation
@@ -32125,7 +32091,7 @@ accomplished by using an appropriate â-v BINMODE=Nâ
option on the
command line. âBINMODEâ is set at the time a file or pipe is opened and
cannot be changed midstream.
- On POSIX-compatible systems, this variableâs value has no effect.
+ On POSIX-compatible systems, this variable's value has no effect.
Thus, if you think your program will run on multiple different systems
and that you may need to use âBINMODEâ, you should simply set it (in the
program or on the command line) unconditionally, and not worry about the
@@ -32136,14 +32102,14 @@ Versions::). âmawkâ and âgawkâ handle
âBINMODEâ similarly; however,
âmawkâ adds a â-W BINMODE=Nâ option and an environment variable that
can
set âBINMODEâ, âRSâ, and âORSâ. The files âbinmode[1-3].awkâ
(under
âgnu/lib/awkâ in some of the prepared binary distributions) have been
-chosen to match âmawkââs â-W BINMODE=Nâ option. These can be
changed or
+chosen to match âmawkâ's â-W BINMODE=Nâ option. These can be changed
or
discarded; in particular, the setting of âRSâ giving the fewest
-âsurprisesâ is open to debate. âmawkâ uses âRS = "\r\n"â if
binary mode
+"surprises" is open to debate. âmawkâ uses âRS = "\r\n"â if binary
mode
is set on read, which is appropriate for files with the MS-DOS-style
end-of-line.
To illustrate, the following examples set binary mode on writes for
-standard output and other files, and set âORSâ as the âusualâ
+standard output and other files, and set âORSâ as the "usual"
MS-DOS-style end-of-line:
gawk -v BINMODE=2 -v ORS="\r\n" ...
@@ -32171,7 +32137,7 @@ File: gawk.info, Node: Cygwin, Next: MSYS, Prev: PC
Using, Up: PC Installati
B.3.1.4 Using âgawkâ In The Cygwin Environment
..............................................
-âgawkâ can be built and used âout of the boxâ under MS-Windows if you
+âgawkâ can be built and used "out of the box" under MS-Windows if you
are using the Cygwin environment (http://www.cygwin.com). This
environment provides an excellent simulation of GNU/Linux, using Bash,
GCC, GNU Make, and other GNU programs. Compilation and installation for
@@ -32209,10 +32175,10 @@ use the âBINMODEâ variable.
This can cause problems with other Unix-like components that have
been ported to MS-Windows that expect âgawkâ to do automatic translation
-of â"\r\n"â, because it wonât.
+of â"\r\n"â, because it won't.
Under MSYS2, compilation using the standard â./configure && makeâ
-recipe works âout of the box.â
+recipe works "out of the box."
File: gawk.info, Node: OpenVMS Installation, Prev: PC Installation, Up:
Non-Unix Installation
@@ -32277,7 +32243,7 @@ that is compatible with the GNV product.
---------- Footnotes ----------
- (1) The IA64 architecture is also known as âItanium.â
+ (1) The IA64 architecture is also known as "Itanium."
File: gawk.info, Node: OpenVMS Dynamic Extensions, Next: OpenVMS
Installation Details, Prev: OpenVMS Compilation, Up: OpenVMS Installation
@@ -32331,7 +32297,7 @@ File: gawk.info, Node: OpenVMS Installation Details,
Next: OpenVMS Running, P
B.3.2.3 Installing âgawkâ on OpenVMS
....................................
-To use âgawkâ, all you need is a âforeignâ command, which is a
âDCLâ
+To use âgawkâ, all you need is a "foreign" command, which is a âDCLâ
symbol whose value begins with a dollar sign. For example:
$ GAWK :== $disk1:[gnubin]gawk
@@ -32504,7 +32470,7 @@ B.4 Reporting Problems and Bugs
===============================
There is nothing more dangerous than a bored archaeologist.
- â _Douglas Adams, âThe Hitchhikerâs Guide to the Galaxyâ_
+ -- _Douglas Adams, âThe Hitchhiker's Guide to the Galaxyâ_
If you have problems with âgawkâ or think that you have found a bug,
report it to the developers; we cannot promise to do anything, but we
@@ -32526,16 +32492,16 @@ File: gawk.info, Node: Bug definition, Next: Bug
address, Up: Bugs
B.4.1 Defining What Is and What Is Not A Bug
--------------------------------------------
-Before talking about reporting bugs, letâs define what is a bug, and
+Before talking about reporting bugs, let's define what is a bug, and
what is not.
A bug is:
- ⢠When âgawkâ behaves differently from whatâs described in the POSIX
+ ⢠When âgawkâ behaves differently from what's described in the POSIX
standard, and that difference is not mentioned in this Info file as
being done on purpose.
- ⢠When âgawkâ behaves differently from whatâs described in this Info
+ ⢠When âgawkâ behaves differently from what's described in this Info
file.
⢠When âgawkâ behaves differently from other âawkâ
implementations in
@@ -32545,13 +32511,13 @@ what is not.
⢠Something that is obviously wrong, such as a core dump.
⢠When this Info file is unclear or ambiguous about a particular
- featureâs behavior.
+ feature's behavior.
The following things are _not_ bugs, and should not be reported to
-the bug mailing list. You can ask about them on the âhelpâ mailing list
-(*note Asking for help::), but donât be surprised if you get an answer
-of the form âthatâs how âgawkâ behaves and it isnât going to
change.â
-Hereâs the list:
+the bug mailing list. You can ask about them on the "help" mailing list
+(*note Asking for help::), but don't be surprised if you get an answer
+of the form "that's how âgawkâ behaves and it isn't going to change."
+Here's the list:
⢠Missing features, for any definition of âfeatureâ. For example,
additional built-in arithmetic functions, or additional ways to
@@ -32559,15 +32525,15 @@ Hereâs the list:
The number of features that âgawkâ does _not_ have is by definition
infinite. It cannot be all things to all people. In short, just
- because âgawkâ doesnât do what _you_ think it should, itâs not
+ because âgawkâ doesn't do what _you_ think it should, it's not
necessarily a bug.
⢠Behaviors that are defined by the POSIX standard and/or for
historical compatibility with Unix âawkâ. Even if you happen to
- dislike those behaviors, theyâre not going to change: changing them
+ dislike those behaviors, they're not going to change: changing them
would break millions of existing âawkâ programs.
- ⢠Behaviors that differ from how itâs done in other languages.
âawkâ
+ ⢠Behaviors that differ from how it's done in other languages. âawkâ
and âgawkâ stand on their own and do not have to follow the crowd.
This is particularly true when the requested behavior change would
break backwards compatibility.
@@ -32577,22 +32543,21 @@ Hereâs the list:
detailed descriptions of what the problem is when a syntax error is
encountered.
- ⢠Documentation issues of the form âthe manual doesnât tell me how to
- do XYZ.â The manual is not a cookbook to solve every little problem
+ ⢠Documentation issues of the form "the manual doesn't tell me how to
+ do XYZ." The manual is not a cookbook to solve every little problem
you may have. Its purpose is to teach you how to solve your
problems on your own.
⢠General questions and discussion about âawkâ programming or why
- âgawkâ behaves the way it does. For that use the âhelpâ mailing
+ âgawkâ behaves the way it does. For that use the "help" mailing
list: see *note Asking for help::.
- For more information, see âFork My Code, Please!âAn Open Letter To
+ For more information, see âFork My Code, Please!--An Open Letter To
Those of You Who Are Unhappyâ (http://www.skeeve.com/fork-my-code.html),
by Arnold Robbins and Chet Ramey.
A Note About Fuzzers
-
- In recent years, people have been running âfuzzersâ to generate
+ In recent years, people have been running "fuzzers" to generate
invalid âawkâ programs in order to find and report (so-called) bugs in
âgawkâ.
@@ -32601,7 +32566,7 @@ they create are not realistic and the bugs found are
generally from some
kind of memory corruption that is fatal anyway.
So, if you want to run a fuzzer against âgawkâ and report the
-results, you may do so, but be aware that such reports donât carry the
+results, you may do so, but be aware that such reports don't carry the
same weight as reports of real bugs do.
@@ -32616,19 +32581,19 @@ Before reporting a bug, make sure you have really
found a genuine bug.
make both your life and the lives of the maintainers much easier.
1. Make sure that what you want to report is appropriate. *Note Bug
- definition::. If itâs not, you are wasting your time and ours.
+ definition::. If it's not, you are wasting your time and ours.
2. Verify that you have the latest version of âgawkâ. Many bugs
(usually subtle ones) are fixed at each release, and if yours is
out-of-date, the problem may already have been solved.
3. Please see if setting the environment variable âLC_ALLâ to
- âLC_ALL=Câ causes things to behave as you expect. If so, itâs a
+ âLC_ALL=Câ causes things to behave as you expect. If so, it's a
locale issue, and may or may not really be a bug.
4. Carefully reread the documentation and see if it says you can do
- what youâre trying to do. If itâs not clear whether you should be
- able to do something or not, report that too; itâs a bug in the
+ what you're trying to do. If it's not clear whether you should be
+ able to do something or not, report that too; it's a bug in the
documentation!
5. Before reporting a bug or trying to fix it yourself, try to isolate
@@ -32664,19 +32629,19 @@ directly; the bug reporting address is preferred
because the email list
is archived at the GNU Project.
If you are using OpenVMS or the MinGW build of âgawkâ, the âgawkbugâ
-script wonât be available. Please send the previously listed
+script won't be available. Please send the previously listed
information directly in an email to the bug list. Please send any test
program or data files as attachments, instead of inline in the email, to
avoid their being mangled by various mail systems.
NOTE: Many distributions of GNU/Linux and the various BSD-based
operating systems have their own bug reporting systems. If you
- report a bug using your distributionâs bug reporting system, you
+ report a bug using your distribution's bug reporting system, you
should also send a copy to <bug-gawk@gnu.org>.
This is for two reasons. First, although some distributions
- forward bug reports âupstreamâ to the GNU mailing list, many donât,
- so there is a good chance that the âgawkâ maintainers wonât even
+ forward bug reports "upstream" to the GNU mailing list, many don't,
+ so there is a good chance that the âgawkâ maintainers won't even
see the bug report! Second, mail to the GNU list is archived, and
having everything at the GNU Project keeps things self-contained
and not dependent on other organizations.
@@ -32688,27 +32653,27 @@ correspondence on the list (as well as off of it).
File: gawk.info, Node: Usenet, Next: Performance bugs, Prev: Bug address,
Up: Bugs
-B.4.3 Please Donât Post Bug Reports to USENET
+B.4.3 Please Don't Post Bug Reports to USENET
---------------------------------------------
- I gave up on Usenet a couple of years ago and havenât really looked
- back. Itâs like sports talk radioâyou feel smarter for not having
+ I gave up on Usenet a couple of years ago and haven't really looked
+ back. It's like sports talk radio--you feel smarter for not having
read it.
- â _Chet Ramey_
+ -- _Chet Ramey_
Please do _not_ try to report bugs in âgawkâ by posting to the
Usenet/Internet newsgroup âcomp.lang.awkâ. Although some of the âgawkâ
developers occasionally read this news group, the primary âgawkâ
-maintainer no longer does. Thus itâs virtually guaranteed that he will
+maintainer no longer does. Thus it's virtually guaranteed that he will
_not_ see your posting.
- If you really donât care about the previous paragraph and continue to
-post bug reports in âcomp.lang.awkâ, then understand that youâre not
-reporting bugs, youâre just whining.
+ If you really don't care about the previous paragraph and continue to
+post bug reports in âcomp.lang.awkâ, then understand that you're not
+reporting bugs, you're just whining.
Similarly, posting bug reports or questions in web forums (such as
Stack Overflow (https://stackoverflow.com/)) may get you an answer, but
-it wonât be from the âgawkâ maintainers, who do not spend their time in
+it won't be from the âgawkâ maintainers, who do not spend their time in
web forums. The steps described here are the only officially recognized
way for reporting bugs. Really.
@@ -32730,7 +32695,7 @@ to follow:
something for every file that only needs to be done once per run of
the program. (Use a âBEGINâ rule; *note BEGIN/END::.)
- 2. If profiling at the âawkâ level doesnât help, then you will need to
+ 2. If profiling at the âawkâ level doesn't help, then you will need to
compile âgawkâ itself for profiling at the C language level.
To do that, start with the latest released version of âgawkâ.
@@ -32810,7 +32775,7 @@ Proulx:
_Subscribe by email_
Send an email message to <help-gawk-request@gnu.org> with
- âsubscribeâ in the body of the message. The subject does not
+ "subscribe" in the body of the message. The subject does not
matter and is not used.
_Subscribe by web form_
@@ -32863,9 +32828,9 @@ File: gawk.info, Node: Other Versions, Next:
Installation summary, Prev: Bugs
B.5 Other Freely Available âawkâ Implementations
================================================
- Itâs kind of fun to put comments like this in your awk code:
+ It's kind of fun to put comments like this in your awk code:
â// Do C++ comments work? answer: yes! of courseâ
- â _Michael Brennan_
+ -- _Michael Brennan_
There are a number of other freely available âawkâ implementations.
This minor node briefly describes where to get them:
@@ -32893,7 +32858,7 @@ Unix âawkâ
that are not in POSIX âawkâ.
As a side note, Dan Bornstein has created a Git repository tracking
- all the versions of BWK âawkâ that he could find. Itâs available
+ all the versions of BWK âawkâ that he could find. It's available
at <https://github.com/danfuzz/one-true-awk>.
âmawkâ
@@ -32906,19 +32871,19 @@ Unix âawkâ
<http://www.skeeve.com/gawk/mawk1.3.3.tar.gz>.
In 2009, Thomas Dickey took on âmawkâ maintenance. Basic
- information is available on the projectâs web page
+ information is available on the project's web page
(http://www.invisible-island.net/mawk). The download URL is
<http://invisible-island.net/datafiles/release/mawk.tar.gz>.
Once you have it, âgunzipâ may be used to decompress this file.
- Installation is similar to âgawkââs (*note Unix Installation::).
+ Installation is similar to âgawkâ's (*note Unix Installation::).
*Note Common Extensions:: for a list of extensions in âmawkâ that
are not in POSIX âawkâ.
âmawkâ 2.0
In 2016, Michael Brennan resumed âmawkâ development. His
- development snapshots are available via Git from the projectâs
+ development snapshots are available via Git from the project's
GitHub page (https://github.com/mikebrennan000/mawk-2).
âawkaâ
@@ -32954,14 +32919,14 @@ BusyBox âawkâ
systems. It includes a full implementation of POSIX âawkâ. When
building it, be careful not to do âmake installâ as it will
overwrite copies of other applications in your â/usr/local/binâ.
- For more information, see the projectâs home page
+ For more information, see the project's home page
(https://busybox.net).
The OpenSolaris POSIX âawkâ
The versions of âawkâ in â/usr/xpg4/binâ and â/usr/xpg6/binâ
on
Solaris are more or less POSIX-compliant. They are based on the
âawkâ from Mortice Kern Systems for PCs. We were able to make this
- code compile and work under GNU/Linux with 1â2 hours of work.
+ code compile and work under GNU/Linux with 1-2 hours of work.
Making it more generally portable (using GNU Autoconf and/or
Automake) would take more work, and this has not been done, at
least to our knowledge.
@@ -32975,10 +32940,10 @@ The OpenSolaris POSIX âawkâ
<https://github.com/joyent/illumos-joyent/blob/master/usr/src/cmd/awk_xpg4>.
âfrawkâ
- This is a language for writing short programs. âTo a first
+ This is a language for writing short programs. "To a first
approximation, it is an implementation of the AWK language; many
common âawkâ programs produce equivalent output when passed to
- âfrawkâ.â However, it has a number of important additional
+ âfrawkâ." However, it has a number of important additional
features. The code is available at
<https://github.com/ezrosent/frawk>.
@@ -32994,17 +32959,17 @@ The OpenSolaris POSIX âawkâ
This is an âawkâ to Go translator. It was written by the author of
âgoawkâ. (See the previous entry in this list.) Source code is
available from
- <https://github.com/benhoyt/goawk/tree/master/awkgo>. The authorâs
+ <https://github.com/benhoyt/goawk/tree/master/awkgo>. The author's
article about it is at <https://benhoyt.com/writings/awkgo/>.
âjawkâ
This is an interpreter for âawkâ written in Java. It claims to be
a full interpreter, although because it uses Java facilities for
I/O and for regexp matching, the language it supports is different
- from POSIX âawkâ. More information is available on the projectâs
+ from POSIX âawkâ. More information is available on the project's
home page (http://jawk.sourceforge.net).
-Hoijuiâs âjawkâ
+Hoijui's âjawkâ
This project, available at <https://github.com/hoijui/Jawk>, is
another âawkâ interpreter written in Java. It uses modern Java
build tools.
@@ -33013,20 +32978,20 @@ Libmawk
This is an embeddable âawkâ interpreter derived from âmawkâ. For
more information, see <http://repo.hu/projects/libmawk/>.
-Mircea Neacsuâs Embeddable âawkâ
+Mircea Neacsu's Embeddable âawkâ
Mircea Neacsu has created an embeddable âawkâ interpreter, based on
- BWK awk. Itâs available at <https://github.com/neacsum/awk>.
+ BWK awk. It's available at <https://github.com/neacsum/awk>.
âpawkâ
This is a Python module that claims to bring âawkâ-like features to
Python. See <https://github.com/alecthomas/pawk> for more
- information. (This is not related to Nelson Beebeâs modified
+ information. (This is not related to Nelson Beebe's modified
version of BWK âawkâ, described earlier.)
âawkccâ
This is an early adaptation of Unix âawkâ that translates âawkâ
into C code. It was done by J. Christopher Ramming at Bell Labs,
- circa 1988. Itâs available at <https://github.com/nokia/awkcc>.
+ circa 1988. It's available at <https://github.com/nokia/awkcc>.
Bringing this up to date would be an interesting software
engineering exercise.
@@ -33047,15 +33012,15 @@ QSE âawkâ
since approximately 2014.
âcppawkâ
- Quoting from the web page, ââcppawkâ is a tiny shell script that is
+ Quoting from the web page, "âcppawkâ is a tiny shell script that is
used like âawkâ. It invokes the C preprocessor (GNU âcppâ) on the
- Awk code and calls Awk on the result.â This program may be of use
- if the way âgawkââs â@includeâ facility works doesnât suit
your
+ Awk code and calls Awk on the result." This program may be of use
+ if the way âgawkâ's â@includeâ facility works doesn't suit your
needs. For more information, see
<https://www.kylheku.com/cgit/cppawk/>.
Other versions
- See also the âVersions and implementationsâ section of the
+ See also the "Versions and implementations" section of the
Wikipedia article
(https://en.wikipedia.org/wiki/Awk_language#Versions_and_implementations)
on âawkâ for information on additional versions.
@@ -33072,7 +33037,7 @@ File: gawk.info, Node: Installation summary, Prev:
Other Versions, Up: Instal
B.6 Summary
===========
- ⢠The âgawkâ distribution is available from the GNU Projectâs main
+ ⢠The âgawkâ distribution is available from the GNU Project's main
distribution site, âftp.gnu.orgâ. The canonical build recipe is:
wget https://ftp.gnu.org/gnu/gawk/gawk-5.3.0.tar.gz
@@ -33183,7 +33148,7 @@ changes, you will probably wish to work with the
development version.
To do so, you will need to access the âgawkâ source code repository.
The code is maintained using the Git distributed version control system
(https://git-scm.com). You will need to install it if your system
-doesnât have it. Once you have done so, use the command:
+doesn't have it. Once you have done so, use the command:
git clone git://git.savannah.gnu.org/gawk.git
@@ -33199,7 +33164,7 @@ the repository using:
patch, and send that to the âgawkâ maintainer; see *note Bugs::, for how
to do that.
- Once upon a time there was GitâCVS gateway for use by people who
+ Once upon a time there was Git-CVS gateway for use by people who
could not install Git. However, this gateway no longer works, so you
may have better luck using a more modern version control system like
Bazaar, that has a Git plug-in for working with Git repositories.
@@ -33216,12 +33181,12 @@ there are several steps that you need to take in
order to make it
possible to include them:
1. Discuss the proposed new feature with the âgawkâ maintainer. The
- bug list may be used for this. Even if I donât wish to include
+ bug list may be used for this. Even if I don't wish to include
your feature, be aware that you are still free to add it and
- distribute your own âforkâ of âgawkâ.
+ distribute your own "fork" of âgawkâ.
2. Before building the new feature into âgawkâ itself, consider
- writing it as an extension (*note Dynamic Extensions::). If thatâs
+ writing it as an extension (*note Dynamic Extensions::). If that's
not possible, continue with the rest of the steps in this list.
3. Be prepared to sign the appropriate paperwork. In order for the
@@ -33240,15 +33205,15 @@ possible to include them:
information on getting the latest version of âgawkâ.)
5. *Note Version: (standards)Top. This document describes how GNU
- software should be written. If you havenât read it, please do so,
+ software should be written. If you haven't read it, please do so,
preferably _before_ starting to modify âgawkâ. (The âGNU Coding
- Standardsâ are available from the GNU Projectâs website
+ Standardsâ are available from the GNU Project's website
(https://www.gnu.org/prep/standards/). Texinfo, Info, and DVI
versions are also available.)
6. Use the âgawkâ coding style. The C code for âgawkâ follows the
instructions in the âGNU Coding Standardsâ, with minor exceptions.
- The code is formatted using the traditional âK&Râ style,
+ The code is formatted using the traditional "K&R" style,
particularly as regards to the placement of braces and the use of
TABs. In brief, the coding rules for âgawkâ are as follows:
@@ -33280,7 +33245,7 @@ possible to include them:
⢠Use real TABs for indenting, not spaces.
- ⢠Use the âK&Râ brace layout style.
+ ⢠Use the "K&R" brace layout style.
⢠Use comparisons against âNULLâ and â'\0'â in the
conditions of
âifâ, âwhileâ, and âforâ statements, as well as in the
âcaseâs
@@ -33305,8 +33270,8 @@ possible to include them:
Instead, use âmalloc()â and âfree()â.
⢠Do not use comparisons of the form â! strcmp(a, b)â or
- similar. As Henry Spencer once said, ââstrcmp()â is not a
- boolean!â Instead, use âstrcmp(a, b) == 0â.
+ similar. As Henry Spencer once said, "âstrcmp()â is not a
+ boolean!" Instead, use âstrcmp(a, b) == 0â.
⢠If adding new bit flag values, use explicit hexadecimal
constants (â0x001â, â0x002â, â0x004â, and so on) instead
of
@@ -33348,7 +33313,7 @@ possible to include them:
Although this sounds like a lot of work, please remember that while
you may write the new code, I have to maintain it and support it. If it
-isnât possible for me to do that with a minimum of extra work, then I
+isn't possible for me to do that with a minimum of extra work, then I
probably will not.
@@ -33408,11 +33373,11 @@ steps:
includes the appropriate âgawkmisc.???â file from each
subdirectory. Be sure to update it as well.
- Each portâs âgawkmisc.???â file has a suffix reminiscent of the
- machine or operating system for the portâfor example,
+ Each port's âgawkmisc.???â file has a suffix reminiscent of the
+ machine or operating system for the port--for example,
âpc/gawkmisc.pcâ and âvms/gawkmisc.vmsâ. The use of separate
suffixes, instead of plain âgawkmisc.câ, makes it possible to move
- files from a portâs subdirectory into the main subdirectory,
+ files from a port's subdirectory into the main subdirectory,
without accidentally destroying the real âgawkmisc.câ file.
(Currently, this is only an issue for the PC operating system
ports.)
@@ -33432,7 +33397,7 @@ steps:
needed to compile and/or install âgawkâ for your system.
Following these steps makes it much easier to integrate your changes
-into âgawkâ and have them coexist happily with other operating systemsâ
+into âgawkâ and have them coexist happily with other operating systems'
code that is already there.
In the code that you supply and maintain, feel free to use a coding
@@ -33467,18 +33432,18 @@ have to bootstrap the V7 âyaccâ to do so, but you
also need the V7
âlexâ. And the latter is pretty much impossible to bring up on a modern
GNU/Linux system.(1)
- (Or, letâs say âgawkâ 1.2 required âbisonâ whatever-it-was in 1989
+ (Or, let's say âgawkâ 1.2 required âbisonâ whatever-it-was in 1989
and that there was no âawkgram.câ file in the repository. Is there a
guarantee that we could find that âbisonâ version? Or that _it_ would
build?)
- If the repository has all the generated files, then itâs easy to just
+ If the repository has all the generated files, then it's easy to just
check them out and build. (Or _easier_, depending upon how far back we
go.)
And that brings us to the second (and stronger) reason why all the
files really need to be in Git. It boils down to who do you cater
-toâthe âgawkâ developer(s), or the user who just wants to check out a
+to--the âgawkâ developer(s), or the user who just wants to check out a
version and try it out?
The âgawkâ maintainer wants it to be possible for any interested
@@ -33496,16 +33461,16 @@ will _just work_.
This is extremely important for the âmasterâ and âgawk-X.Y-stableâ
branches.
- Further, the âgawkâ maintainer would argue that itâs also important
+ Further, the âgawkâ maintainer would argue that it's also important
for the âgawkâ developers. When he tried to check out the âxgawkâ
-branch(3) to build it, he couldnât. (No âltmain.shâ file, and he had no
+branch(3) to build it, he couldn't. (No âltmain.shâ file, and he had no
idea how to create it, and that was not the only problem.)
He felt _extremely_ frustrated. With respect to that branch, the
maintainer is no different than Jane User who wants to try to build
âgawk-4.1-stableâ or âmasterâ from the repository.
- Thus, the maintainer thinks that itâs not just important, but
+ Thus, the maintainer thinks that it's not just important, but
critical, that for any given branch, the above incantation _just works_.
A third reason to have all the files is that without them, using âgit
@@ -33517,14 +33482,14 @@ on; it was really painful. When the repository is
self-contained, using
What are some of the consequences and/or actions to take?
- 1. We donât mind that there are differing files in the different
+ 1. We don't mind that there are differing files in the different
branches as a result of different versions of the autotools.
- A. Itâs the maintainerâs job to merge them and he will deal with
+ A. It's the maintainer's job to merge them and he will deal with
it.
B. He is really good at âgit diff x y > /tmp/diff1 ; gvim
- /tmp/diff1â to remove the diffs that arenât of interest in
+ /tmp/diff1â to remove the diffs that aren't of interest in
order to review code.
2. It would certainly help if everyone used the same versions of the
@@ -33532,7 +33497,7 @@ on; it was really painful. When the repository is
self-contained, using
versions of Automake, Autoconf, âbisonâ, GNU âgettextâ, and
Libtool.
- Installing from source is quite easy. Itâs how the maintainer
+ Installing from source is quite easy. It's how the maintainer
worked for years (and still works). He had â/usr/local/binâ at the
front of his âPATHâ and just did:
@@ -33548,17 +33513,17 @@ on; it was really painful. When the repository is
self-contained, using
Most of the above was originally written by the maintainer to other
âgawkâ developers. It raised the objection from one of the developers
-â... that anybody pulling down the source from Git is not an end user.â
+"... that anybody pulling down the source from Git is not an end user."
- However, this is not true. There are âpower âawkâ usersâ who can
+ However, this is not true. There are "power âawkâ users" who can
build âgawkâ (using the magic incantation shown previously) but who
-canât program in C. Thus, the major branches should be kept buildable
+can't program in C. Thus, the major branches should be kept buildable
all the time.
It was then suggested that there be a âcronâ job to create nightly
-tarballs of âthe source.â Here, the problem is that there are source
+tarballs of "the source." Here, the problem is that there are source
trees, corresponding to the various branches! So, nightly tarballs
-arenât the answer, especially as the repository can go for weeks without
+aren't the answer, especially as the repository can go for weeks without
significant change being introduced.
Fortunately, the Git server can meet this need. For any given branch
@@ -33574,10 +33539,10 @@ to retrieve a snapshot of the given branch.
(2) There is one GNU program that is (in our opinion) severely
difficult to bootstrap from the Git repository. For example, on the
-authorâs old (but still working) PowerPC Macintosh with macOS 10.5, it
+author's old (but still working) PowerPC Macintosh with macOS 10.5, it
was necessary to bootstrap a ton of software, starting with Git itself,
-in order to try to work with the latest code. Itâs not pleasant, and
-especially on older systems, itâs a big waste of time.
+in order to try to work with the latest code. It's not pleasant, and
+especially on older systems, it's a big waste of time.
Starting with the latest tarball was no picnic either. The
maintainers had dropped â.gzâ and â.bz2â files and only distribute
@@ -33593,10 +33558,10 @@ C.3 Probable Future Extensions
==============================
AWK is a language similar to PERL, only considerably more elegant.
- â _Arnold Robbins_
+ -- _Arnold Robbins_
Hey!
- â _Larry Wall_
+ -- _Larry Wall_
The âTODOâ file in the âmasterâ branch of the âgawkâ Git
repository
lists possible future enhancements. Some of these relate to the source
@@ -33654,7 +33619,7 @@ mechanisms and design remained unchanged for close to
15 years, until
2012.
The old extension mechanism used data types and functions from âgawkâ
-itself, with a âclever hackâ to install extension functions.
+itself, with a "clever hack" to install extension functions.
âgawkâ included some sample extensions, of which a few were really
useful. However, it was clear from the outset that the extension
@@ -33678,7 +33643,7 @@ The old extension mechanism had several problems:
⢠It depended heavily upon âgawkâ internals. Any time the âNODEâ
structure(1) changed, an extension would have to be recompiled.
Furthermore, to really write extensions required understanding
- something about âgawkââs internal functions. There was some
+ something about âgawkâ's internal functions. There was some
documentation in this Info file, but it was quite minimal.
⢠Being able to call into âgawkâ from an extension required linker
@@ -33692,7 +33657,7 @@ The old extension mechanism had several problems:
Despite the drawbacks, the âxgawkâ project developers forked âgawkâ
and developed several significant extensions. They also enhanced
-âgawkââs facilities relating to file inclusion and shared object access.
+âgawkâ's facilities relating to file inclusion and shared object access.
A new API was desired for a long time, but only in 2012 did the
âgawkâ maintainer and the âxgawkâ developers finally start working on
it
@@ -33719,7 +33684,7 @@ Some goals for the new API were:
releases as long as the API itself does not change.
⢠The API should enable extensions written in C or C++ to have
- roughly the same âappearanceâ to âawkâ-level code as âawkâ
+ roughly the same "appearance" to âawkâ-level code as âawkâ
functions do. This means that extensions should have:
â The ability to access function parameters.
@@ -33729,11 +33694,11 @@ Some goals for the new API were:
â The ability to create, access and update global variables.
- â Easy access to all the elements of an array at once (âarray
- flatteningâ) in order to loop over all the element in an easy
+ â Easy access to all the elements of an array at once ("array
+ flattening") in order to loop over all the element in an easy
fashion for C code.
- â The ability to create arrays (including âgawkââs true arrays
+ â The ability to create arrays (including âgawkâ's true arrays
of arrays).
Some additional important goals were:
@@ -33746,7 +33711,7 @@ Some goals for the new API were:
constructors and destructors, as âgawkâ is a C program. As of this
writing, this has not been tested.)
- ⢠The API mechanism should not require access to âgawkââs symbols(1)
+ ⢠The API mechanism should not require access to âgawkâ's symbols(1)
by the compile-time or dynamic linker, in order to enable creation
of extensions that also work on MS-Windows.
@@ -33754,20 +33719,20 @@ Some goals for the new API were:
that should be available to extensions, which were also subsequently
provided:
- ⢠Extensions should have the ability to hook into âgawkââs I/O
+ ⢠Extensions should have the ability to hook into âgawkâ's I/O
redirection mechanism. In particular, the âxgawkâ developers
- provided a so-called âopen hookâ to take over reading records.
+ provided a so-called "open hook" to take over reading records.
During development, this was generalized to allow extensions to
hook into input processing, output processing, and two-way I/O.
- ⢠An extension should be able to provide a âcall backâ function to
+ ⢠An extension should be able to provide a "call back" function to
perform cleanup actions when âgawkâ exits.
⢠An extension should be able to provide a version string so that
- âgawkââs â--versionâ option can provide information about
+ âgawkâ's â--versionâ option can provide information about
extensions as well.
- The requirement to avoid access to âgawkââs symbols is, at first
+ The requirement to avoid access to âgawkâ's symbols is, at first
glance, a difficult one to meet.
One design, apparently used by Perl and Ruby and maybe others, would
@@ -33818,7 +33783,7 @@ with the simplest, most basic features that are still
truly useful.
MPFR, and arrays indexed internally by integers, these features are not
being brought out to the API in order to keep things simple and close to
traditional âawkâ semantics. (In fact, arrays indexed internally by
-integers are so transparent that they arenât even documented!)
+integers are so transparent that they aren't even documented!)
Additionally, all functions in the API check that their pointer input
parameters are not âNULLâ. If they are, they return an error. (It is a
@@ -33840,7 +33805,7 @@ C.5.4 Room For Future Growth
The API can later be expanded, in at least the following way:
- ⢠âgawkâ passes an âextension idâ into the extension when it first
+ ⢠âgawkâ passes an "extension id" into the extension when it first
loads the extension. The extension then passes this id back to
âgawkâ with each function call. This mechanism allows âgawkâ to
identify the extension calling into it, should it need to know.
@@ -33854,7 +33819,7 @@ File: gawk.info, Node: Notes summary, Prev: Extension
Design, Up: Notes
C.6 Summary
===========
- ⢠âgawkââs extensions can be disabled with either the
â--traditionalâ
+ ⢠âgawkâ's extensions can be disabled with either the
â--traditionalâ
option or with the â--posixâ option. The â--parsedebugâ option is
available if âgawkâ is compiled with â-DDEBUGâ.
@@ -33866,7 +33831,7 @@ C.6 Summary
contributions into the code base. This applies both to new feature
contributions and to ports to additional operating systems.
- ⢠âgawkâ has some limitsâgenerally those that are imposed by the
+ ⢠âgawkâ has some limits--generally those that are imposed by the
machine architecture.
⢠The extension API design was intended to solve a number of problems
@@ -33904,7 +33869,6 @@ D.1 What a Program Does
At the most basic level, the job of a program is to process some input
data and produce results. See *note Figure D.1: figure-general-flow.
-
[image src="gawk_general-program.png" alt="General program flow" text="
_______
+------+ / \\ +---------+
| Data | -----> < Program > -----> | Results |
@@ -33912,7 +33876,7 @@ data and produce results. See *note Figure D.1:
figure-general-flow.
Figure D.1: General Program Flow
- The âprogramâ in the figure can be either a compiled program(1) (such
+ The "program" in the figure can be either a compiled program(1) (such
as âlsâ), or it may be âinterpretedâ. In the latter case, a
machine-executable program such as âawkâ reads your program, and then
uses the instructions in your program to process the data.
@@ -33920,7 +33884,6 @@ uses the instructions in your program to process the
data.
When you write a program, it usually consists of the following, very
basic set of steps, as shown in *note Figure D.2: figure-process-flow.:
-
[image src="gawk_process-flow.png" alt="Basic Program Stages" text="
______
+----------------+ / More \\ No +----------+
| Initialization | -------> < Data > -------> | Clean Up |
@@ -33938,7 +33901,7 @@ Figure D.2: Basic Program Steps
Initialization
These are the things you do before actually starting to process
data, such as checking arguments, initializing any data you need to
- work with, and so on. This step corresponds to âawkââs âBEGINâ
+ work with, and so on. This step corresponds to âawkâ's âBEGINâ
rule (*note BEGIN/END::).
If you were baking a cake, this might consist of laying out all the
@@ -33951,7 +33914,7 @@ Processing
In most programming languages, you have to manually manage the
reading of data, checking to see if there is more each time you
- read a chunk. âawkââs pattern-action paradigm (*note Getting
+ read a chunk. âawkâ's pattern-action paradigm (*note Getting
Started::) handles the mechanics of this for you.
In baking a cake, the processing corresponds to the actual labor:
@@ -33959,8 +33922,8 @@ Processing
then putting the cake into the oven.
Clean Up
- Once youâve processed all the data, you may have things you need to
- do before exiting. This step corresponds to âawkââs âENDâ rule
+ Once you've processed all the data, you may have things you need to
+ do before exiting. This step corresponds to âawkâ's âENDâ rule
(*note BEGIN/END::).
After the cake comes out of the oven, you still have to wrap it in
@@ -33972,7 +33935,7 @@ accomplish a task, or process data. It is much the
same as a recipe for
baking a cake. Programs implement algorithms. Often, it is up to you
to design the algorithm and implement it, simultaneously.
- The âlogical chunksâ we talked about previously are called
ârecordsâ,
+ The "logical chunks" we talked about previously are called ârecordsâ,
similar to the records a company keeps on employees, a school keeps for
students, or a doctor keeps for patients. Each record has many
component parts, such as first and last names, date of birth, address,
@@ -33981,11 +33944,11 @@ record.
The act of reading data is termed âinputâ, and that of generating
results, not too surprisingly, is termed âoutputâ. They are often
-referred to together as âinput/output,â and even more often, as âI/Oâ
-for short. (You will also see âinputâ and âoutputâ used as verbs.)
+referred to together as "input/output," and even more often, as "I/O"
+for short. (You will also see "input" and "output" used as verbs.)
âawkâ manages the reading of data for you, as well as the breaking it
-up into records and fields. Your programâs job is to tell âawkâ what to
+up into records and fields. Your program's job is to tell âawkâ what to
do with the data. You do this by describing âpatternsâ in the data to
look for, and âactionsâ to execute when those patterns are seen. This
âdata-drivenâ nature of âawkâ programs usually makes them both easier
to
@@ -34012,7 +33975,7 @@ associated values under one name, as an array.
Data, particularly in âawkâ, consists of either numeric values, such
as 42 or 3.1415927, or string values. String values are essentially
-anything thatâs not a number, such as a name. Strings are sometimes
+anything that's not a number, such as a name. Strings are sometimes
referred to as âcharacter dataâ, since they store the individual
characters that comprise them. Individual variables, as well as numeric
and string variables, are referred to as âscalarâ values. Groups of
@@ -34031,7 +33994,7 @@ value. In other words, it is empty. It is written in
âawkâ programs
like this: â""â.
Humans are used to working in decimal; i.e., base 10. In base 10,
-numbers go from 0 to 9, and then âroll overâ into the next column.
+numbers go from 0 to 9, and then "roll over" into the next column.
(Remember grade school? 42 = 4 x 10 + 2.)
There are other number bases though. Computers commonly use base 2
@@ -34052,7 +34015,7 @@ the C programming language. The C language had a very
strong influence
on the design of the âawkâ language.
There have been several versions of C. The first is often referred to
-as âK&Râ C, after the initials of Brian Kernighan and Dennis Ritchie,
+as "K&R" C, after the initials of Brian Kernighan and Dennis Ritchie,
the authors of the first book on C. (Dennis Ritchie created the
language, and Brian Kernighan was one of the creators of âawkâ.)
@@ -34069,8 +34032,8 @@ Glossary
********
Action
- A series of âawkâ statements attached to a rule. If the ruleâs
- pattern matches an input record, âawkâ executes the ruleâs action.
+ A series of âawkâ statements attached to a rule. If the rule's
+ pattern matches an input record, âawkâ executes the rule's action.
Actions are always enclosed in braces. (*Note Action Overview::.)
Ada
@@ -34098,7 +34061,7 @@ ANSI
The American National Standards Institute. This organization
produces many standards, among them the standards for the C and C++
programming languages. These standards often become international
- standards as well. See also âISO.â
+ standards as well. See also "ISO."
Argument
An argument can be two different things. It can be an option or a
@@ -34113,7 +34076,7 @@ Argument
function itself; or it is given by reference, i.e., a pointer to
the interested variable is passed to the function, which can then
directly modify it. In âawkâ scalars are passed by value, and
- arrays are passed by reference. See âPass By Value/Reference.â
+ arrays are passed by reference. See "Pass By Value/Reference."
Array
A grouping of multiple values under the same name. Most languages
@@ -34140,7 +34103,7 @@ Associative Array
âawkâ Program
An âawkâ program consists of a series of âpatternsâ and
âactionsâ,
collectively known as ârulesâ. For each input record given to the
- program, the programâs rules are all processed in turn. âawkâ
+ program, the program's rules are all processed in turn. âawkâ
programs may also contain function definitions.
âawkâ Script
@@ -34148,11 +34111,11 @@ Associative Array
Bash
The GNU version of the standard shell (the Bourne-Again SHell).
- See also âBourne Shell.â
+ See also "Bourne Shell."
Binary
- Base-two notation, where the digits are â0âââ1â. Since
electronic
- circuitry works ânaturallyâ in base 2 (just think of Off/On),
+ Base-two notation, where the digits are â0â-â1â. Since electronic
+ circuitry works "naturally" in base 2 (just think of Off/On),
everything inside a computer is calculated using base 2. Each
digit represents the presence (or absence) of a power of 2 and is
called a âbitâ. So, for example, the base-two number â10101â is
@@ -34170,9 +34133,9 @@ Binary
numbers in their registers, but 32-bit, 16-bit and 8-bit registers
have been widely used in the past. *Note Nondecimal-numbers::.
Bit
- Short for âBinary Digit.â All values in computer memory ultimately
+ Short for "Binary Digit." All values in computer memory ultimately
reduce to binary digits: values that are either zero or one.
- Groups of bits may be interpreted differentlyâas integers,
+ Groups of bits may be interpreted differently--as integers,
floating-point numbers, character data, addresses of other memory
objects, or other data. âawkâ lets you work with floating-point
numbers and strings. âgawkâ lets you manipulate bit values with
@@ -34184,8 +34147,8 @@ Bit
essentially disappeared.
Boolean Expression
- Named after the English mathematician Boole. See also âLogical
- Expression.â
+ Named after the English mathematician Boole. See also "Logical
+ Expression."
Bourne Shell
The standard shell (â/bin/shâ) on Unix and Unix-like systems,
@@ -34207,8 +34170,8 @@ Bracket Expression
expression enclosed between â:â is independent of the underlying
representation of the character themselves, which could utilize the
ASCII, EBCDIC, or Unicode codesets, depending on the architecture
- of the computer system, and on localization. See also âRegular
- Expression.â
+ of the computer system, and on localization. See also "Regular
+ Expression."
Built-in Function
The âawkâ language provides built-in functions that perform various
@@ -34225,7 +34188,7 @@ Built-in Variable
addition, âARGINDâ, âBINMODEâ, âERRNOâ, âFIELDWIDTHSâ,
âFPATâ,
âIGNORECASEâ, âLINTâ, âPROCINFOâ, âRTâ, and
âTEXTDOMAINâ are the
variables that have special meaning to âgawkâ. Changing some of
- them affects âawkââs running environment. (*Note Built-in
+ them affects âawkâ's running environment. (*Note Built-in
Variables::.)
C
@@ -34245,16 +34208,16 @@ C Shell
compatible with the Bourne Shell, so special attention is required
when converting scripts written for other Unix shells to the C
shell, especially with regard to the management of shell variables.
- See also âBourne Shell.â
+ See also "Bourne Shell."
C++
A popular object-oriented programming language derived from C.
Character Class
- See âBracket Expression.â
+ See "Bracket Expression."
Character List
- See âBracket Expression.â
+ See "Bracket Expression."
Character Set
The set of numeric codes used by a computer system to represent the
@@ -34281,22 +34244,22 @@ Comparison Expression
Compiler
A program that translates human-readable source code into
machine-executable object code. The object code is then executed
- directly by the computer. See also âInterpreter.â
+ directly by the computer. See also "Interpreter."
Complemented Bracket Expression
The negation of a âbracket expressionâ. All that is _not_
described by a given bracket expression. The symbol â^â precedes
the negated bracket expression. E.g.: â[^[:digit:]]â designates
whatever character is not a digit. â[^bad]â designates whatever
- character is not one of the letters âbâ, âaâ, or âdâ. See
âBracket
- Expression.â
+ character is not one of the letters âbâ, âaâ, or âdâ. See
"Bracket
+ Expression."
Compound Statement
A series of âawkâ statements, enclosed in curly braces. Compound
statements may be nested. (*Note Statements::.)
Computed Regexps
- See âDynamic Regular Expressions.â
+ See "Dynamic Regular Expressions."
Concatenation
Concatenating two strings means sticking them together, one after
@@ -34326,13 +34289,13 @@ Coprocess
possible.
Curly Braces
- See âBraces.â
+ See "Braces."
Dark Corner
An area in the language where specifications often were (or still
are) not clear, leading to unexpected or undesirable behavior.
- Such areas are marked in this Info file with â(d.c.)â in the text
- and are indexed under the heading âdark corner.â
+ Such areas are marked in this Info file with "(d.c.)" in the text
+ and are indexed under the heading "dark corner."
Data Driven
A description of âawkâ programs, where you specify the data you are
@@ -34347,7 +34310,7 @@ Deadlock
for the other to perform an action.
Debugger
- A program used to help developers remove âbugsâ from (de-bug) their
+ A program used to help developers remove "bugs" from (de-bug) their
programs.
Double Precision
@@ -34364,7 +34327,7 @@ Dynamic Regular Expression
(*Note Computed Regexps::.)
Empty String
- See âNull String.â
+ See "Null String."
Environment
A collection of strings, of the form âNAME=VALâ, that each program
@@ -34373,13 +34336,13 @@ Environment
Typical examples are the environment variables âHOMEâ and âPATHâ.
Epoch
- The date used as the âbeginning of timeâ for timestamps. Time
+ The date used as the "beginning of time" for timestamps. Time
values in most systems are represented as seconds since the epoch,
with library functions available for converting these values into
standard date and time formats.
The epoch on Unix and POSIX systems is 1970-01-01 00:00:00 UTC. See
- also âGMTâ and âUTC.â
+ also "GMT" and "UTC."
Escape Sequences
A special sequence of characters used for describing nonprinting
@@ -34388,11 +34351,11 @@ Escape Sequences
Extension
An additional feature or change to a programming language or
- utility not defined by that languageâs or utilityâs standard.
+ utility not defined by that language's or utility's standard.
âgawkâ has (too) many extensions over POSIX âawkâ.
FDL
- See âFree Documentation License.â
+ See "Free Documentation License."
Field
When âawkâ reads an input record, it splits the record into pieces
@@ -34410,9 +34373,9 @@ Flag
nonexistence of some condition.
Floating-Point Number
- Often referred to in mathematical terms as a ârationalâ or real
+ Often referred to in mathematical terms as a "rational" or real
number, this is just a number that can have a fractional part. See
- also âDouble Precisionâ and âSingle Precision.â
+ also "Double Precision" and "Single Precision."
Format
Format strings control the appearance of output in the âstrftime()â
@@ -34439,7 +34402,7 @@ Free Software Foundation
Emacs is the most widely used version of Emacs today.
FSF
- See âFree Software Foundation.â
+ See "Free Software Foundation."
Function
A part of an âawkâ program that can be invoked from every point of
@@ -34461,18 +34424,18 @@ General Public License
code may be distributed. (*Note Copying::.)
GMT
- âGreenwich Mean Time.â This is the old term for UTC. It is the time
- of day used internally for Unix and POSIX systems. See also
- âEpochâ and âUTC.â
+ "Greenwich Mean Time." This is the old term for UTC. It is the
+ time of day used internally for Unix and POSIX systems. See also
+ "Epoch" and "UTC."
GNU
- âGNUâs not Unixâ. An on-going project of the Free Software
+ "GNU's not Unix". An on-going project of the Free Software
Foundation to create a complete, freely distributable,
POSIX-compliant computing environment.
GNU/Linux
A variant of the GNU system using the Linux kernel, instead of the
- Free Software Foundationâs Hurd kernel. The Linux kernel is a
+ Free Software Foundation's Hurd kernel. The Linux kernel is a
stable, efficient, full-featured clone of Unix that has been ported
to a variety of architectures. It is most popular on PC-class
systems, but runs well on a variety of other systems too. The
@@ -34480,17 +34443,17 @@ GNU/Linux
General Public License, which is perhaps its most important aspect.
GPL
- See âGeneral Public License.â
+ See "General Public License."
Hexadecimal
- Base 16 notation, where the digits are â0âââ9â and
âAâââFâ, with
+ Base 16 notation, where the digits are â0â-â9â and
âAâ-âFâ, with
âAâ representing 10, âBâ representing 11, and so on, up to
âFâ for
15. Hexadecimal numbers are written in C using a leading â0xâ, to
indicate their base. Thus, â0x12â is 18 ((1 x 16) + 2). *Note
Nondecimal-numbers::.
I/O
- Abbreviation for âInput/Output,â the act of moving data into and/or
+ Abbreviation for "Input/Output," the act of moving data into and/or
out of a running program.
Input Record
@@ -34509,7 +34472,7 @@ Interpreter
A program that reads human-readable source code directly, and uses
the instructions in it to process data and produce results. âawkâ
is typically (but not always) implemented as an interpreter. See
- also âCompiler.â
+ also "Compiler."
Interval Expression
A component of a regular expression that lets you specify repeated
@@ -34522,7 +34485,7 @@ ISO
including programming languages, such as C and C++. In the
computer arena, important standards like those for C, C++, and
POSIX become both American national and ISO international standards
- simultaneously. This Info file refers to Standard C as âISO Câ
+ simultaneously. This Info file refers to Standard C as "ISO C"
throughout. See the ISO website
(https://www.iso.org/iso/home/about.htm) for more information about
the name of the organization and its language-independent
@@ -34540,7 +34503,7 @@ Keyword
meaning. Keywords are reserved and may not be used as variable
names.
- âgawkââs keywords are: âBEGINâ, âBEGINFILEâ, âENDâ,
âENDFILEâ,
+ âgawkâ's keywords are: âBEGINâ, âBEGINFILEâ, âENDâ,
âENDFILEâ,
âbreakâ, âcaseâ, âcontinueâ, âdefaultâ, âdeleteâ,
âdo...whileâ,
âelseâ, âexitâ, âfor...inâ, âforâ, âfunctionâ,
âfuncâ, âifâ,
ânextâ, ânextfileâ, âswitchâ, and âwhileâ.
@@ -34549,7 +34512,7 @@ Korn Shell
The Korn Shell (âkshâ) is a Unix shell which was developed by David
Korn at Bell Laboratories in the early 1980s. The Korn Shell is
backward-compatible with the Bourne shell and includes many
- features of the C shell. See also âBourne Shell.â
+ features of the C shell. See also "Bourne Shell."
Lesser General Public License
This document describes the terms under which binary library
@@ -34557,10 +34520,10 @@ Lesser General Public License
distributed.
LGPL
- See âLesser General Public License.â
+ See "Lesser General Public License."
Linux
- See âGNU/Linux.â
+ See "GNU/Linux."
Localization
The process of providing the data necessary for an
@@ -34591,7 +34554,7 @@ Metacharacters
Nesting
Nesting is where information is organized in layers, or where
objects contain other similar objects. In âgawkâ the â@includeâ
- directive can be nested. The ânaturalâ nesting of arithmetic and
+ directive can be nested. The "natural" nesting of arithmetic and
logical operations can be changed using parentheses (*note
Precedence::).
@@ -34610,7 +34573,7 @@ Number
âawkâ implementations used single precision floating-point.
Octal
- Base-eight notation, where the digits are â0âââ7â. Octal
numbers
+ Base-eight notation, where the digits are â0â-â7â. Octal numbers
are written in C using a leading â0â, to indicate their base.
Thus, â013â is 11 ((1 x 8) + 3). *Note Nondecimal-numbers::.
@@ -34635,11 +34598,11 @@ PEBKAC
Chair.)
Plug-in
- See âExtensions.â
+ See "Extensions."
POSIX
The name for a series of standards that specify a Portable
- Operating System interface. The âIXâ denotes the Unix heritage of
+ Operating System interface. The "IX" denotes the Unix heritage of
these standards. The main standard of interest for âawkâ users is
âIEEE Standard for Information Technology, Standard
1003.1^{TM}-2017 (Revision of IEEE Std 1003.1-2008)â. The 2018
@@ -34662,12 +34625,12 @@ Range (of input lines)
specify single lines. (*Note Pattern Overview::.)
Record
- See âInput recordâ and âOutput record.â
+ See "Input record" and "Output record."
Recursion
When a function calls itself, either directly or indirectly. If
this is clear, stop, and proceed to the next entry. Otherwise,
- refer to the entry for ârecursion.â
+ refer to the entry for "recursion."
Redirection
Redirection means performing input from something other than the
@@ -34691,10 +34654,10 @@ Reference Counts
the value of the variable is freed.
Regexp
- See âRegular Expression.â
+ See "Regular Expression."
Regular Expression
- A regular expression (âregexpâ for short) is a pattern that denotes
+ A regular expression ("regexp" for short) is a pattern that denotes
a set of strings, possibly an infinite set. For example, the
regular expression âR.*xpâ matches any string starting with the
letter âRâ and ending with the letters âxpâ. In âawkâ,
regular
@@ -34709,7 +34672,7 @@ Regular Expression Constant
execution. (*Note Regexp Usage::.)
Regular Expression Operators
- See âMetacharacters.â
+ See "Metacharacters."
Rounding
Rounding the result of an arithmetic operation can be tricky. More
@@ -34721,7 +34684,7 @@ Rule
A segment of an âawkâ program that specifies how to process single
input records. A rule consists of a âpatternâ and an âactionâ.
âawkâ reads an input record; then, for each rule, if the input
- record satisfies the ruleâs pattern, âawkâ executes the ruleâs
+ record satisfies the rule's pattern, âawkâ executes the rule's
action. Otherwise, the rule does nothing for that input record.
Rvalue
@@ -34739,7 +34702,7 @@ Search Path
executable programs.
âsedâ
- See âStream Editor.â
+ See "Stream Editor."
Seed
The initial value, or starting point, for a sequence of random
@@ -34775,12 +34738,12 @@ Space
Special File
A file name interpreted internally by âgawkâ, instead of being
- handed directly to the underlying operating systemâfor example,
+ handed directly to the underlying operating system--for example,
â/dev/stderrâ. (*Note Special Files::.)
Statement
An expression inside an âawkâ program in the action part of a
- patternâaction rule, or inside an âawkâ function. A statement can
+ pattern-action rule, or inside an âawkâ function. A statement can
be a variable assignment, an array operation, a loop, etc.
Stream Editor
@@ -34805,13 +34768,13 @@ Text Domain
messages that are translated at runtime into the local language.
Timestamp
- A value in the âseconds since the epochâ format used by Unix and
+ A value in the "seconds since the epoch" format used by Unix and
POSIX systems. Used for the âgawkâ functions âmktime()â,
- âstrftime()â, and âsystime()â. See also âEpoch,â âGMT,â
and âUTC.â
+ âstrftime()â, and âsystime()â. See also "Epoch," "GMT," and
"UTC."
Unix
A computer operating system originally developed in the early
- 1970âs at AT&T Bell Laboratories. It initially became popular in
+ 1970's at AT&T Bell Laboratories. It initially became popular in
universities around the world and later moved into commercial
environments as a software development system and network server
system. There are many commercial versions of Unix, as well as
@@ -34820,9 +34783,10 @@ Unix
(https://www.freebsd.org), and OpenBSD (http://www.openbsd.org)).
UTC
- The accepted abbreviation for âUniversal Coordinated Time.â This is
- standard time in Greenwich, England, which is used as a reference
- time for day and date calculations. See also âEpochâ and âGMT.â
+ The accepted abbreviation for "Universal Coordinated Time." This
+ is standard time in Greenwich, England, which is used as a
+ reference time for day and date calculations. See also "Epoch" and
+ "GMT."
Variable
A name for a value. In âawkâ, variables may be either scalars or
@@ -34854,7 +34818,7 @@ and other kinds of works.
The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
the GNU General Public License is intended to guarantee your freedom to
-share and change all versions of a programâto make sure it remains free
+share and change all versions of a program--to make sure it remains free
software for all its users. We, the Free Software Foundation, use the
GNU General Public License for most of our software; it applies also to
any other work released this way by its authors. You can apply it to
@@ -34882,16 +34846,16 @@ know their rights.
(1) assert copyright on the software, and (2) offer you this License
giving you legal permission to copy, distribute and/or modify it.
- For the developersâ and authorsâ protection, the GPL clearly explains
-that there is no warranty for this free software. For both usersâ and
-authorsâ sake, the GPL requires that modified versions be marked as
+ For the developers' and authors' protection, the GPL clearly explains
+that there is no warranty for this free software. For both users' and
+authors' sake, the GPL requires that modified versions be marked as
changed, so that their problems will not be attributed erroneously to
authors of previous versions.
Some devices are designed to deny users access to install or run
modified versions of the software inside them, although the manufacturer
can do so. This is fundamentally incompatible with the aim of
-protecting usersâ freedom to change the software. The systematic
+protecting users' freedom to change the software. The systematic
pattern of such abuse occurs in the area of products for individuals to
use, which is precisely where it is most unacceptable. Therefore, we
have designed this version of the GPL to prohibit the practice for those
@@ -34914,25 +34878,25 @@ TERMS AND CONDITIONS
0. Definitions.
- âThis Licenseâ refers to version 3 of the GNU General Public
+ "This License" refers to version 3 of the GNU General Public
License.
- âCopyrightâ also means copyright-like laws that apply to other
+ "Copyright" also means copyright-like laws that apply to other
kinds of works, such as semiconductor masks.
- âThe Programâ refers to any copyrightable work licensed under this
- License. Each licensee is addressed as âyouâ. âLicenseesâ and
- ârecipientsâ may be individuals or organizations.
+ "The Program" refers to any copyrightable work licensed under this
+ License. Each licensee is addressed as "you". "Licensees" and
+ "recipients" may be individuals or organizations.
- To âmodifyâ a work means to copy from or adapt all or part of the
+ To "modify" a work means to copy from or adapt all or part of the
work in a fashion requiring copyright permission, other than the
- making of an exact copy. The resulting work is called a âmodified
- versionâ of the earlier work or a work âbased onâ the earlier work.
+ making of an exact copy. The resulting work is called a "modified
+ version" of the earlier work or a work "based on" the earlier work.
- A âcovered workâ means either the unmodified Program or a work
+ A "covered work" means either the unmodified Program or a work
based on the Program.
- To âpropagateâ a work means to do anything with it that, without
+ To "propagate" a work means to do anything with it that, without
permission, would make you directly or secondarily liable for
infringement under applicable copyright law, except executing it on
a computer or modifying a private copy. Propagation includes
@@ -34940,12 +34904,12 @@ TERMS AND CONDITIONS
available to the public, and in some countries other activities as
well.
- To âconveyâ a work means any kind of propagation that enables other
+ To "convey" a work means any kind of propagation that enables other
parties to make or receive copies. Mere interaction with a user
through a computer network, with no transfer of a copy, is not
conveying.
- An interactive user interface displays âAppropriate Legal Noticesâ
+ An interactive user interface displays "Appropriate Legal Notices"
to the extent that it includes a convenient and prominently visible
feature that (1) displays an appropriate copyright notice, and (2)
tells the user that there is no warranty for the work (except to
@@ -34957,33 +34921,33 @@ TERMS AND CONDITIONS
1. Source Code.
- The âsource codeâ for a work means the preferred form of the work
- for making modifications to it. âObject codeâ means any non-source
+ The "source code" for a work means the preferred form of the work
+ for making modifications to it. "Object code" means any non-source
form of a work.
- A âStandard Interfaceâ means an interface that either is an
+ A "Standard Interface" means an interface that either is an
official standard defined by a recognized standards body, or, in
the case of interfaces specified for a particular programming
language, one that is widely used among developers working in that
language.
- The âSystem Librariesâ of an executable work include anything,
+ The "System Libraries" of an executable work include anything,
other than the work as a whole, that (a) is included in the normal
form of packaging a Major Component, but which is not part of that
Major Component, and (b) serves only to enable use of the work with
that Major Component, or to implement a Standard Interface for
which an implementation is available to the public in source code
- form. A âMajor Componentâ, in this context, means a major
+ form. A "Major Component", in this context, means a major
essential component (kernel, window system, and so on) of the
specific operating system (if any) on which the executable work
runs, or a compiler used to produce the work, or an object code
interpreter used to run it.
- The âCorresponding Sourceâ for a work in object code form means all
+ The "Corresponding Source" for a work in object code form means all
the source code needed to generate, install, and (for an executable
work) run the object code and to modify the work, including scripts
to control those activities. However, it does not include the
- workâs System Libraries, or general-purpose tools or generally
+ work's System Libraries, or general-purpose tools or generally
available free programs which are used unmodified in performing
those activities but which are not part of the work. For example,
Corresponding Source includes interface definition files associated
@@ -35027,7 +34991,7 @@ TERMS AND CONDITIONS
the conditions stated below. Sublicensing is not allowed; section
10 makes it unnecessary.
- 3. Protecting Usersâ Legal Rights From Anti-Circumvention Law.
+ 3. Protecting Users' Legal Rights From Anti-Circumvention Law.
No covered work shall be deemed part of an effective technological
measure under any applicable law fulfilling obligations under
@@ -35040,12 +35004,12 @@ TERMS AND CONDITIONS
circumvention is effected by exercising rights under this License
with respect to the covered work, and you disclaim any intention to
limit operation or modification of the work as a means of
- enforcing, against the workâs users, your or third partiesâ legal
+ enforcing, against the work's users, your or third parties' legal
rights to forbid circumvention of technological measures.
4. Conveying Verbatim Copies.
- You may convey verbatim copies of the Programâs source code as you
+ You may convey verbatim copies of the Program's source code as you
receive it, in any medium, provided that you conspicuously and
appropriately publish on each copy an appropriate copyright notice;
keep intact all notices stating that this License and any
@@ -35069,7 +35033,7 @@ TERMS AND CONDITIONS
b. The work must carry prominent notices stating that it is
released under this License and any conditions added under
section 7. This requirement modifies the requirement in
- section 4 to âkeep intact all noticesâ.
+ section 4 to "keep intact all notices".
c. You must license the entire work, as a whole, under this
License to anyone who comes into possession of a copy. This
@@ -35089,9 +35053,9 @@ TERMS AND CONDITIONS
works, which are not by their nature extensions of the covered
work, and which are not combined with it such as to form a larger
program, in or on a volume of a storage or distribution medium, is
- called an âaggregateâ if the compilation and its resulting
+ called an "aggregate" if the compilation and its resulting
copyright are not used to limit the access or legal rights of the
- compilationâs users beyond what the individual works permit.
+ compilation's users beyond what the individual works permit.
Inclusion of a covered work in an aggregate does not cause this
License to apply to the other parts of the aggregate.
@@ -35149,13 +35113,13 @@ TERMS AND CONDITIONS
excluded from the Corresponding Source as a System Library, need
not be included in conveying the object code work.
- A âUser Productâ is either (1) a âconsumer productâ, which means
+ A "User Product" is either (1) a "consumer product", which means
any tangible personal property which is normally used for personal,
family, or household purposes, or (2) anything designed or sold for
incorporation into a dwelling. In determining whether a product is
a consumer product, doubtful cases shall be resolved in favor of
coverage. For a particular product received by a particular user,
- ânormally usedâ refers to a typical or common use of that class of
+ "normally used" refers to a typical or common use of that class of
product, regardless of the status of the particular user or of the
way in which the particular user actually uses, or expects or is
expected to use, the product. A product is a consumer product
@@ -35163,7 +35127,7 @@ TERMS AND CONDITIONS
industrial or non-consumer uses, unless such uses represent the
only significant mode of use of the product.
- âInstallation Informationâ for a User Product means any methods,
+ "Installation Information" for a User Product means any methods,
procedures, authorization keys, or other information required to
install and execute modified versions of a covered work in that
User Product from a modified version of its Corresponding Source.
@@ -35199,7 +35163,7 @@ TERMS AND CONDITIONS
7. Additional Terms.
- âAdditional permissionsâ are terms that supplement the terms of
+ "Additional permissions" are terms that supplement the terms of
this License by making exceptions from one or more of its
conditions. Additional permissions that are applicable to the
entire Program shall be treated as though they were included in
@@ -35244,8 +35208,8 @@ TERMS AND CONDITIONS
the recipient, for any liability that these contractual
assumptions directly impose on those licensors and authors.
- All other non-permissive additional terms are considered âfurther
- restrictionsâ within the meaning of section 10. If the Program as
+ All other non-permissive additional terms are considered "further
+ restrictions" within the meaning of section 10. If the Program as
you received it, or any part of it, contains a notice stating that
it is governed by this License along with a term that is a further
restriction, you may remove that term. If a license document
@@ -35311,12 +35275,12 @@ TERMS AND CONDITIONS
responsible for enforcing compliance by third parties with this
License.
- An âentity transactionâ is a transaction transferring control of an
+ An "entity transaction" is a transaction transferring control of an
organization, or substantially all assets of one, or subdividing an
organization, or merging organizations. If propagation of a
covered work results from an entity transaction, each party to that
transaction who receives a copy of the work also receives whatever
- licenses to the work the partyâs predecessor in interest had or
+ licenses to the work the party's predecessor in interest had or
could give under the previous paragraph, plus a right to possession
of the Corresponding Source of the work from the predecessor in
interest, if the predecessor has it or can get it with reasonable
@@ -35333,31 +35297,31 @@ TERMS AND CONDITIONS
11. Patents.
- A âcontributorâ is a copyright holder who authorizes use under this
+ A "contributor" is a copyright holder who authorizes use under this
License of the Program or a work on which the Program is based.
- The work thus licensed is called the contributorâs âcontributor
- versionâ.
+ The work thus licensed is called the contributor's "contributor
+ version".
- A contributorâs âessential patent claimsâ are all patent claims
+ A contributor's "essential patent claims" are all patent claims
owned or controlled by the contributor, whether already acquired or
hereafter acquired, that would be infringed by some manner,
permitted by this License, of making, using, or selling its
contributor version, but do not include claims that would be
infringed only as a consequence of further modification of the
- contributor version. For purposes of this definition, âcontrolâ
+ contributor version. For purposes of this definition, "control"
includes the right to grant patent sublicenses in a manner
consistent with the requirements of this License.
Each contributor grants you a non-exclusive, worldwide,
- royalty-free patent license under the contributorâs essential
+ royalty-free patent license under the contributor's essential
patent claims, to make, use, sell, offer for sale, import and
otherwise run, modify and propagate the contents of its contributor
version.
- In the following three paragraphs, a âpatent licenseâ is any
+ In the following three paragraphs, a "patent license" is any
express agreement or commitment, however denominated, not to
enforce a patent (such as an express permission to practice a
- patent or covenant not to sue for patent infringement). To âgrantâ
+ patent or covenant not to sue for patent infringement). To "grant"
such a patent license to a party means to make such an agreement or
commitment not to enforce a patent against the party.
@@ -35370,9 +35334,9 @@ TERMS AND CONDITIONS
yourself of the benefit of the patent license for this particular
work, or (3) arrange, in a manner consistent with the requirements
of this License, to extend the patent license to downstream
- recipients. âKnowingly relyingâ means you have actual knowledge
+ recipients. "Knowingly relying" means you have actual knowledge
that, but for the patent license, your conveying the covered work
- in a country, or your recipientâs use of the covered work in a
+ in a country, or your recipient's use of the covered work in a
country, would infringe one or more identifiable patents in that
country that you have reason to believe are valid.
@@ -35384,7 +35348,7 @@ TERMS AND CONDITIONS
patent license you grant is automatically extended to all
recipients of the covered work and works based on it.
- A patent license is âdiscriminatoryâ if it does not include within
+ A patent license is "discriminatory" if it does not include within
the scope of its coverage, prohibits the exercise of, or is
conditioned on the non-exercise of one or more of the rights that
are specifically granted under this License. You may not convey a
@@ -35404,7 +35368,7 @@ TERMS AND CONDITIONS
any implied license or other defenses to infringement that may
otherwise be available to you under applicable patent law.
- 12. No Surrender of Othersâ Freedom.
+ 12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement
or otherwise) that contradict the conditions of this License, they
@@ -35437,7 +35401,7 @@ TERMS AND CONDITIONS
Each version is given a distinguishing version number. If the
Program specifies that a certain numbered version of the GNU
- General Public License âor any later versionâ applies to it, you
+ General Public License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that numbered version or of any later version published by the Free
Software Foundation. If the Program does not specify a version
@@ -35446,7 +35410,7 @@ TERMS AND CONDITIONS
If the Program specifies that a proxy can decide which future
versions of the GNU General Public License can be used, that
- proxyâs public statement of acceptance of a version permanently
+ proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Program.
Later license versions may give you additional or different
@@ -35458,7 +35422,7 @@ TERMS AND CONDITIONS
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE
- COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM âAS ISâ
+ COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE
@@ -35502,7 +35466,7 @@ terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least the
-âcopyrightâ line and a pointer to where the full notice is found.
+"copyright" line and a pointer to where the full notice is found.
ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
Copyright (C) YEAR NAME OF AUTHOR
@@ -35533,11 +35497,11 @@ notice like this when it starts in an interactive
mode:
The hypothetical commands âshow wâ and âshow câ should show the
appropriate parts of the General Public License. Of course, your
-programâs commands might be different; for a GUI interface, you would
-use an âabout boxâ.
+program's commands might be different; for a GUI interface, you would
+use an "about box".
You should also get your employer (if you work as a programmer) or
-school, if any, to sign a âcopyright disclaimerâ for the program, if
+school, if any, to sign a "copyright disclaimer" for the program, if
necessary. For more information on this, and how to apply and follow
the GNU GPL, see <https://www.gnu.org/licenses/>.
@@ -35572,7 +35536,7 @@ GNU Free Documentation License
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.
- This License is a kind of âcopyleftâ, which means that derivative
+ This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
@@ -35593,18 +35557,18 @@ GNU Free Documentation License
be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
- âDocumentâ, below, refers to any such manual or work. Any member
- of the public is a licensee, and is addressed as âyouâ. You accept
+ "Document", below, refers to any such manual or work. Any member
+ of the public is a licensee, and is addressed as "you". You accept
the license if you copy, modify or distribute the work in a way
requiring permission under copyright law.
- A âModified Versionâ of the Document means any work containing the
+ A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
- A âSecondary Sectionâ is a named appendix or a front-matter section
+ A "Secondary Section" is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
- publishers or authors of the Document to the Documentâs overall
+ publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could
fall directly within that overall subject. (Thus, if the Document
is in part a textbook of mathematics, a Secondary Section may not
@@ -35613,7 +35577,7 @@ GNU Free Documentation License
of legal, commercial, philosophical, ethical or political position
regarding them.
- The âInvariant Sectionsâ are certain Secondary Sections whose
+ The "Invariant Sections" are certain Secondary Sections whose
titles are designated, as being those of Invariant Sections, in the
notice that says that the Document is released under this License.
If a section does not fit the above definition of Secondary then it
@@ -35621,13 +35585,13 @@ GNU Free Documentation License
contain zero Invariant Sections. If the Document does not identify
any Invariant Sections then there are none.
- The âCover Textsâ are certain short passages of text that are
+ The "Cover Texts" are certain short passages of text that are
listed, as Front-Cover Texts or Back-Cover Texts, in the notice
that says that the Document is released under this License. A
Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
- A âTransparentâ copy of the Document means a machine-readable copy,
+ A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed
@@ -35639,7 +35603,7 @@ GNU Free Documentation License
been arranged to thwart or discourage subsequent modification by
readers is not Transparent. An image format is not Transparent if
used for any substantial amount of text. A copy that is not
- âTransparentâ is called âOpaqueâ.
+ "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format,
@@ -35652,23 +35616,23 @@ GNU Free Documentation License
the machine-generated HTML, PostScript or PDF produced by some word
processors for output purposes only.
- The âTitle Pageâ means, for a printed book, the title page itself,
+ The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the
material this License requires to appear in the title page. For
- works in formats which do not have any title page as such, âTitle
- Pageâ means the text near the most prominent appearance of the
- workâs title, preceding the beginning of the body of the text.
+ works in formats which do not have any title page as such, "Title
+ Page" means the text near the most prominent appearance of the
+ work's title, preceding the beginning of the body of the text.
- The âpublisherâ means any person or entity that distributes copies
+ The "publisher" means any person or entity that distributes copies
of the Document to the public.
- A section âEntitled XYZâ means a named subunit of the Document
+ A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
- âAcknowledgementsâ, âDedicationsâ, âEndorsementsâ, or
âHistoryâ.)
- To âPreserve the Titleâ of such a section when you modify the
- Document means that it remains a section âEntitled XYZâ according
+ "Acknowledgements", "Dedications", "Endorsements", or "History".)
+ To "Preserve the Title" of such a section when you modify the
+ Document means that it remains a section "Entitled XYZ" according
to this definition.
The Document may include Warranty Disclaimers next to the notice
@@ -35698,7 +35662,7 @@ GNU Free Documentation License
If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and
- the Documentâs license notice requires Cover Texts, you must
+ the Document's license notice requires Cover Texts, you must
enclose the copies in covers that carry, clearly and legibly, all
these Cover Texts: Front-Cover Texts on the front cover, and
Back-Cover Texts on the back cover. Both covers must also clearly
@@ -35770,15 +35734,15 @@ GNU Free Documentation License
the Addendum below.
G. Preserve in that license notice the full lists of Invariant
- Sections and required Cover Texts given in the Documentâs
+ Sections and required Cover Texts given in the Document's
license notice.
H. Include an unaltered copy of this License.
- I. Preserve the section Entitled âHistoryâ, Preserve its Title,
+ I. Preserve the section Entitled "History", Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on the
- Title Page. If there is no section Entitled âHistoryâ in the
+ Title Page. If there is no section Entitled "History" in the
Document, create one stating the title, year, authors, and
publisher of the Document as given on its Title Page, then add
an item describing the Modified Version as stated in the
@@ -35788,12 +35752,12 @@ GNU Free Documentation License
for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for
previous versions it was based on. These may be placed in the
- âHistoryâ section. You may omit a network location for a work
+ "History" section. You may omit a network location for a work
that was published at least four years before the Document
itself, or if the original publisher of the version it refers
to gives permission.
- K. For any section Entitled âAcknowledgementsâ or âDedicationsâ,
+ K. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, and preserve in the section
all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
@@ -35802,11 +35766,11 @@ GNU Free Documentation License
in their text and in their titles. Section numbers or the
equivalent are not considered part of the section titles.
- M. Delete any section Entitled âEndorsementsâ. Such a section
+ M. Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled
- âEndorsementsâ or to conflict in title with any Invariant
+ "Endorsements" or to conflict in title with any Invariant
Section.
O. Preserve any Warranty Disclaimers.
@@ -35815,15 +35779,15 @@ GNU Free Documentation License
appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option designate
some or all of these sections as invariant. To do this, add their
- titles to the list of Invariant Sections in the Modified Versionâs
+ titles to the list of Invariant Sections in the Modified Version's
license notice. These titles must be distinct from any other
section titles.
- You may add a section Entitled âEndorsementsâ, provided it contains
+ You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
- partiesâfor example, statements of peer review or that the text has
- been approved by an organization as the authoritative definition of
- a standard.
+ parties--for example, statements of peer review or that the text
+ has been approved by an organization as the authoritative
+ definition of a standard.
You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end of
@@ -35861,10 +35825,10 @@ GNU Free Documentation License
combined work.
In the combination, you must combine any sections Entitled
- âHistoryâ in the various original documents, forming one section
- Entitled âHistoryâ; likewise combine any sections Entitled
- âAcknowledgementsâ, and any sections Entitled âDedicationsâ. You
- must delete all sections Entitled âEndorsements.â
+ "History" in the various original documents, forming one section
+ Entitled "History"; likewise combine any sections Entitled
+ "Acknowledgements", and any sections Entitled "Dedications". You
+ must delete all sections Entitled "Endorsements."
6. COLLECTIONS OF DOCUMENTS
@@ -35885,16 +35849,16 @@ GNU Free Documentation License
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of a
- storage or distribution medium, is called an âaggregateâ if the
+ storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
- legal rights of the compilationâs users beyond what the individual
+ legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
- of the entire aggregate, the Documentâs Cover Texts may be placed
+ of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
@@ -35916,8 +35880,8 @@ GNU Free Documentation License
this License or a notice or disclaimer, the original version will
prevail.
- If a section in the Document is Entitled âAcknowledgementsâ,
- âDedicationsâ, or âHistoryâ, the requirement (section 4) to
+ If a section in the Document is Entitled "Acknowledgements",
+ "Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
@@ -35958,7 +35922,7 @@ GNU Free Documentation License
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
- version of this License âor any later versionâ applies to it, you
+ version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If the
@@ -35966,29 +35930,29 @@ GNU Free Documentation License
choose any version ever published (not as a draft) by the Free
Software Foundation. If the Document specifies that a proxy can
decide which future versions of this License can be used, that
- proxyâs public statement of acceptance of a version permanently
+ proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
11. RELICENSING
- âMassive Multiauthor Collaboration Siteâ (or âMMC Siteâ) means any
+ "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
- A âMassive Multiauthor Collaborationâ (or âMMCâ) contained in the
+ A "Massive Multiauthor Collaboration" (or "MMC") contained in the
site means any set of copyrightable works thus published on the MMC
site.
- âCC-BY-SAâ means the Creative Commons Attribution-Share Alike 3.0
+ "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
- âIncorporateâ means to publish or republish a Document, in whole or
+ "Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.
- An MMC is âeligible for relicensingâ if it is licensed under this
+ An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
@@ -36015,7 +35979,7 @@ notices just after the title page:
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
-Texts, replace the âwith...Texts.â line with this:
+Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
@@ -36039,81 +36003,22 @@ Index
[index ]
* Menu:
-* ! (exclamation point), !~ operator: Regexp Usage. (line 19)
-* ! (exclamation point), !~ operator <1>: Computed Regexps. (line 6)
-* ! (exclamation point), !~ operator <2>: Case-sensitivity. (line 26)
-* ! (exclamation point), !~ operator <3>: Regexp Constants. (line 6)
-* ! (exclamation point), != operator: Comparison Operators.
- (line 11)
-* ! (exclamation point), !~ operator <4>: Comparison Operators.
- (line 11)
-* ! (exclamation point), !~ operator <5>: Comparison Operators.
- (line 99)
-* ! (exclamation point), ! operator: Boolean Ops. (line 69)
-* ! (exclamation point), ! operator <1>: Precedence. (line 51)
-* ! (exclamation point), != operator <1>: Precedence. (line 64)
-* ! (exclamation point), !~ operator <6>: Precedence. (line 79)
-* ! (exclamation point), !~ operator <7>: Expression Patterns.
- (line 24)
-* ! (exclamation point), ! operator <2>: Ranges. (line 47)
-* ! (exclamation point), ! operator <3>: Egrep Program. (line 204)
-* " (double quote), in shell commands: Quoting. (line 54)
-* " (double quote), in regexp constants: Computed Regexps. (line 30)
-* # (number sign), #! (executable scripts): Executable Scripts.
- (line 6)
-* # (number sign), commenting: Comments. (line 6)
-* $ (dollar sign), regexp operator: Regexp Operator Details.
- (line 31)
-* $ (dollar sign), $ field operator: Fields. (line 19)
-* $ (dollar sign), incrementing fields and arrays: Increment Ops.
- (line 30)
-* $ (dollar sign), $ field operator <1>: Precedence. (line 42)
-* % (percent sign), %= operator: Assignment Ops. (line 129)
-* % (percent sign), % operator: Precedence. (line 54)
-* % (percent sign), %= operator <1>: Precedence. (line 94)
-* & (ampersand), && operator: Boolean Ops. (line 59)
-* & (ampersand), && operator <1>: Precedence. (line 85)
-* & (ampersand), gsub()/gensub()/sub() functions and: Gory Details.
- (line 6)
-* ' (single quote): One-shot. (line 15)
-* ' (single quote), in gawk command lines: Long. (line 35)
-* ' (single quote), vs. apostrophe: Comments. (line 27)
-* ' (single quote), in shell commands: Quoting. (line 48)
-* ' (single quote), with double quotes: Quoting. (line 73)
-* () (parentheses), regexp operator: Regexp Operator Details.
- (line 77)
-* () (parentheses), in a profile: Profiling. (line 146)
-* * (asterisk), * operator, as regexp operator: Regexp Operator Details.
- (line 91)
-* * (asterisk), ** operator: Arithmetic Ops. (line 85)
-* * (asterisk), *= operator: Assignment Ops. (line 129)
-* * (asterisk), **= operator: Assignment Ops. (line 129)
-* * (asterisk), ** operator <1>: Precedence. (line 48)
-* * (asterisk), * operator, as multiplication operator: Precedence.
- (line 54)
-* * (asterisk), *= operator <1>: Precedence. (line 94)
-* * (asterisk), **= operator <1>: Precedence. (line 94)
-* * (asterisk), * operator, null strings, matching: String Functions.
- (line 575)
-* + (plus sign), regexp operator: Regexp Operator Details.
- (line 107)
-* + (plus sign), += operator: Assignment Ops. (line 81)
-* + (plus sign), ++ operator: Increment Ops. (line 11)
-* + (plus sign), ++ operator <1>: Increment Ops. (line 40)
-* + (plus sign), ++ operator <2>: Precedence. (line 45)
-* + (plus sign), + operator: Precedence. (line 51)
-* + (plus sign), + operator <1>: Precedence. (line 57)
-* + (plus sign), += operator <1>: Precedence. (line 94)
-* , (comma), in range patterns: Ranges. (line 6)
-* - (hyphen), file names beginning with: Options. (line 63)
+* _ (underscore), C macro: Explaining gettext. (line 71)
+* _ (underscore), in names of private variables: Library Names.
+ (line 29)
+* _ (underscore), translatable strings: Programmer i18n. (line 69)
+* _gr_init() user-defined function: Group Functions. (line 83)
+* _ord_init() user-defined function: Ordinal Functions. (line 16)
+* _pw_init() user-defined function: Passwd Functions. (line 105)
+* - (hyphen), - operator: Precedence. (line 51)
+* - (hyphen), - operator <1>: Precedence. (line 57)
* - (hyphen), -- end of options marker: Options. (line 360)
-* - (hyphen), in bracket expressions: Bracket Expressions. (line 25)
-* - (hyphen), -= operator: Assignment Ops. (line 129)
* - (hyphen), -- operator: Increment Ops. (line 48)
* - (hyphen), -- operator <1>: Precedence. (line 45)
-* - (hyphen), - operator: Precedence. (line 51)
-* - (hyphen), - operator <1>: Precedence. (line 57)
+* - (hyphen), -= operator: Assignment Ops. (line 129)
* - (hyphen), -= operator <1>: Precedence. (line 94)
+* - (hyphen), file names beginning with: Options. (line 63)
+* - (hyphen), in bracket expressions: Bracket Expressions. (line 25)
* --assign option: Options. (line 36)
* --bignum option: Options. (line 248)
* --characters-as-bytes option: Options. (line 72)
@@ -36158,11 +36063,11 @@ Index
* --profile option <1>: Profiling. (line 12)
* --re-interval option: Options. (line 329)
* --sandbox option: Options. (line 340)
+* --sandbox option, disabling system() function: I/O Functions.
+ (line 127)
* --sandbox option, input redirection with getline: Getline. (line 19)
* --sandbox option, output redirection with print, printf: Redirection.
(line 6)
-* --sandbox option, disabling system() function: I/O Functions.
- (line 127)
* --source option: Options. (line 120)
* --trace option: Options. (line 197)
* --traditional option: Options. (line 85)
@@ -36181,9 +36086,9 @@ Index
* -F option: Options. (line 21)
* -f option <1>: Options. (line 25)
* -F option, -Ft sets FS to TAB: Options. (line 368)
-* -f option, multiple uses: Options. (line 373)
* -F option, command-line: Command Line Field Separator.
(line 6)
+* -f option, multiple uses: Options. (line 373)
* -g option: Options. (line 168)
* -h option: Options. (line 175)
* -i option: Options. (line 180)
@@ -36206,161 +36111,214 @@ Index
* -V option: Options. (line 355)
* -v option <1>: Assignment Options. (line 12)
* -W option: Options. (line 50)
-* . (period), regexp operator: Regexp Operator Details.
- (line 40)
-* .gmo files: Explaining gettext. (line 42)
-* .gmo files, specifying directory of: Explaining gettext. (line 54)
-* .gmo files, specifying directory of <1>: Programmer i18n. (line 48)
-* .mo files, converting from .po: I18N Example. (line 80)
-* .po files: Explaining gettext. (line 37)
-* .po files <1>: Translator i18n. (line 6)
-* .po files, converting to .mo: I18N Example. (line 80)
-* .pot files: Explaining gettext. (line 31)
-* / (forward slash), to enclose regular expressions: Regexp. (line 10)
-* / (forward slash), /= operator: Assignment Ops. (line 129)
-* / (forward slash), /= operator, vs. /=.../ regexp constant: Assignment Ops.
- (line 150)
-* / (forward slash), / operator: Precedence. (line 54)
-* / (forward slash), /= operator <1>: Precedence. (line 94)
-* / (forward slash), patterns and: Expression Patterns. (line 24)
-* /= operator vs. /=.../ regexp constant: Assignment Ops. (line 150)
-* /dev/... special files: Special FD. (line 48)
-* /dev/fd/N special files (gawk): Special FD. (line 48)
-* /inet/... special files (gawk): TCP/IP Networking. (line 6)
-* /inet4/... special files (gawk): TCP/IP Networking. (line 6)
-* /inet6/... special files (gawk): TCP/IP Networking. (line 6)
-* : (colon), ?: operator: Precedence. (line 91)
-* : (colon), :: namespace separator: Qualified Names. (line 6)
+* , (comma), in range patterns: Ranges. (line 6)
+* ; (semicolon), AWKPATH variable and: PC Using. (line 12)
+* ; (semicolon), separating rules: Statements/Lines. (line 118)
* ; (semicolon), separating statements in actions: Statements/Lines.
(line 118)
-* ; (semicolon), separating rules: Statements/Lines. (line 118)
* ; (semicolon), separating statements in actions <1>: Action Overview.
(line 19)
* ; (semicolon), separating statements in actions <2>: Statements.
(line 10)
-* ; (semicolon), AWKPATH variable and: PC Using. (line 12)
-* < (left angle bracket), < operator (I/O): Getline/File. (line 6)
-* < (left angle bracket), < operator: Comparison Operators.
- (line 11)
-* < (left angle bracket), <= operator: Comparison Operators.
- (line 11)
-* < (left angle bracket), < operator <1>: Precedence. (line 64)
-* < (left angle bracket), <= operator <1>: Precedence. (line 64)
-* = (equals sign), = operator: Assignment Ops. (line 6)
-* = (equals sign), == operator: Comparison Operators.
- (line 11)
-* = (equals sign), == operator <1>: Precedence. (line 64)
-* > (right angle bracket), > operator (I/O): Redirection. (line 22)
-* > (right angle bracket), >> operator (I/O): Redirection. (line 50)
-* > (right angle bracket), >= operator: Comparison Operators.
+* : (colon), :: namespace separator: Qualified Names. (line 6)
+* : (colon), ?: operator: Precedence. (line 91)
+* ! (exclamation point), ! operator: Boolean Ops. (line 69)
+* ! (exclamation point), ! operator <1>: Precedence. (line 51)
+* ! (exclamation point), ! operator <2>: Ranges. (line 47)
+* ! (exclamation point), ! operator <3>: Egrep Program. (line 204)
+* ! (exclamation point), != operator: Comparison Operators.
(line 11)
-* > (right angle bracket), > operator: Comparison Operators.
+* ! (exclamation point), != operator <1>: Precedence. (line 64)
+* ! (exclamation point), !~ operator: Regexp Usage. (line 19)
+* ! (exclamation point), !~ operator <1>: Computed Regexps. (line 6)
+* ! (exclamation point), !~ operator <2>: Case-sensitivity. (line 26)
+* ! (exclamation point), !~ operator <3>: Regexp Constants. (line 6)
+* ! (exclamation point), !~ operator <4>: Comparison Operators.
(line 11)
-* > (right angle bracket), >= operator <1>: Precedence. (line 64)
-* > (right angle bracket), > operator <1>: Precedence. (line 64)
-* > (right angle bracket), >> operator (I/O) <1>: Precedence. (line 64)
+* ! (exclamation point), !~ operator <5>: Comparison Operators.
+ (line 98)
+* ! (exclamation point), !~ operator <6>: Precedence. (line 79)
+* ! (exclamation point), !~ operator <7>: Expression Patterns.
+ (line 24)
+* ? (question mark), ?: operator: Precedence. (line 91)
* ? (question mark), regexp operator: Regexp Operator Details.
(line 113)
* ? (question mark), regexp operator <1>: GNU Regexp Operators.
(line 61)
-* ? (question mark), ?: operator: Precedence. (line 91)
+* . (period), regexp operator: Regexp Operator Details.
+ (line 40)
+* .gmo files: Explaining gettext. (line 42)
+* .gmo files, specifying directory of: Explaining gettext. (line 54)
+* .gmo files, specifying directory of <1>: Programmer i18n. (line 48)
+* .mo files, converting from .po: I18N Example. (line 80)
+* .po files: Explaining gettext. (line 37)
+* .po files <1>: Translator i18n. (line 6)
+* .po files, converting to .mo: I18N Example. (line 80)
+* .pot files: Explaining gettext. (line 31)
+* ' (single quote): One-shot. (line 15)
+* ' (single quote), in gawk command lines: Long. (line 35)
+* ' (single quote), in shell commands: Quoting. (line 48)
+* ' (single quote), vs. apostrophe: Comments. (line 27)
+* ' (single quote), with double quotes: Quoting. (line 73)
+* " (double quote), in regexp constants: Computed Regexps. (line 30)
+* " (double quote), in shell commands: Quoting. (line 54)
+* () (parentheses), in a profile: Profiling. (line 146)
+* () (parentheses), regexp operator: Regexp Operator Details.
+ (line 77)
+* [] (square brackets), regexp operator: Regexp Operator Details.
+ (line 52)
+* {} (braces): Profiling. (line 142)
+* {} (braces), actions and: Action Overview. (line 19)
+* {} (braces), regexp operator: Regexp Operator Details.
+ (line 118)
+* {} (braces), statements, grouping: Statements. (line 10)
+* @ (at-sign), @-notation for indirect function calls: Indirect Calls.
+ (line 47)
* @ (at-sign), @include directive: Include Files. (line 8)
* @ (at-sign), @load directive: Loading Shared Libraries.
(line 8)
-* @ (at-sign), @-notation for indirect function calls: Indirect Calls.
- (line 47)
* @ (at-sign), @namespace directive: Changing The Namespace.
(line 6)
* @ (at-sign), @namespace directive, BEGIN, BEGINFILE, END, ENDFILE and:
Changing The Namespace.
(line 37)
-* [] (square brackets), regexp operator: Regexp Operator Details.
- (line 52)
+* * (asterisk), * operator, as multiplication operator: Precedence.
+ (line 54)
+* * (asterisk), * operator, as regexp operator: Regexp Operator Details.
+ (line 91)
+* * (asterisk), * operator, null strings, matching: String Functions.
+ (line 574)
+* * (asterisk), ** operator: Arithmetic Ops. (line 85)
+* * (asterisk), ** operator <1>: Precedence. (line 48)
+* * (asterisk), **= operator: Assignment Ops. (line 129)
+* * (asterisk), **= operator <1>: Precedence. (line 94)
+* * (asterisk), *= operator: Assignment Ops. (line 129)
+* * (asterisk), *= operator <1>: Precedence. (line 94)
+* / (forward slash), / operator: Precedence. (line 54)
+* / (forward slash), /= operator: Assignment Ops. (line 129)
+* / (forward slash), /= operator <1>: Precedence. (line 94)
+* / (forward slash), /= operator, vs. /=.../ regexp constant: Assignment Ops.
+ (line 148)
+* / (forward slash), patterns and: Expression Patterns. (line 24)
+* / (forward slash), to enclose regular expressions: Regexp. (line 10)
+* /= operator vs. /=.../ regexp constant: Assignment Ops. (line 149)
+* /dev/... special files: Special FD. (line 48)
+* /dev/fd/N special files (gawk): Special FD. (line 48)
+* /inet/... special files (gawk): TCP/IP Networking. (line 6)
+* /inet4/... special files (gawk): TCP/IP Networking. (line 6)
+* /inet6/... special files (gawk): TCP/IP Networking. (line 6)
* \ (backslash): Comments. (line 50)
-* \ (backslash), in shell commands: Quoting. (line 48)
-* \ (backslash), continuing lines and: Statements/Lines. (line 19)
-* \ (backslash), continuing lines and, in csh: Statements/Lines.
- (line 45)
-* \ (backslash), continuing lines and, comments and: Statements/Lines.
- (line 77)
-* \ (backslash), in escape sequences: Escape Sequences. (line 6)
+* \ (backslash), \' operator (gawk): GNU Regexp Operators.
+ (line 58)
+* \ (backslash), \" escape sequence: Escape Sequences. (line 101)
+* \ (backslash), \/ escape sequence: Escape Sequences. (line 92)
+* \ (backslash), \` operator (gawk): GNU Regexp Operators.
+ (line 56)
+* \ (backslash), \< operator (gawk): GNU Regexp Operators.
+ (line 30)
+* \ (backslash), \> operator (gawk): GNU Regexp Operators.
+ (line 34)
* \ (backslash), \a escape sequence: Escape Sequences. (line 34)
* \ (backslash), \b escape sequence: Escape Sequences. (line 38)
+* \ (backslash), \B operator (gawk): GNU Regexp Operators.
+ (line 43)
* \ (backslash), \f escape sequence: Escape Sequences. (line 41)
* \ (backslash), \n escape sequence: Escape Sequences. (line 44)
-* \ (backslash), \r escape sequence: Escape Sequences. (line 47)
-* \ (backslash), \t escape sequence: Escape Sequences. (line 50)
-* \ (backslash), \v escape sequence: Escape Sequences. (line 53)
* \ (backslash), \NNN escape sequence: Escape Sequences. (line 56)
-* \ (backslash), \x escape sequence: Escape Sequences. (line 61)
-* \ (backslash), \u escape sequence: Escape Sequences. (line 76)
-* \ (backslash), \/ escape sequence: Escape Sequences. (line 92)
-* \ (backslash), \" escape sequence: Escape Sequences. (line 101)
-* \ (backslash), in escape sequences <1>: Escape Sequences. (line 119)
-* \ (backslash), in escape sequences, POSIX and: Escape Sequences.
- (line 124)
-* \ (backslash), regexp operator: Regexp Operator Details.
- (line 14)
-* \ (backslash), in bracket expressions: Bracket Expressions. (line 25)
-* \ (backslash), in regexp constants: Computed Regexps. (line 30)
+* \ (backslash), \r escape sequence: Escape Sequences. (line 47)
* \ (backslash), \s operator (gawk): GNU Regexp Operators.
(line 13)
* \ (backslash), \S operator (gawk): GNU Regexp Operators.
(line 17)
+* \ (backslash), \t escape sequence: Escape Sequences. (line 50)
+* \ (backslash), \u escape sequence: Escape Sequences. (line 76)
+* \ (backslash), \v escape sequence: Escape Sequences. (line 53)
* \ (backslash), \w operator (gawk): GNU Regexp Operators.
(line 21)
* \ (backslash), \W operator (gawk): GNU Regexp Operators.
(line 26)
-* \ (backslash), \< operator (gawk): GNU Regexp Operators.
- (line 30)
-* \ (backslash), \> operator (gawk): GNU Regexp Operators.
- (line 34)
+* \ (backslash), \x escape sequence: Escape Sequences. (line 61)
* \ (backslash), \y operator (gawk): GNU Regexp Operators.
(line 38)
-* \ (backslash), \B operator (gawk): GNU Regexp Operators.
- (line 43)
-* \ (backslash), \` operator (gawk): GNU Regexp Operators.
- (line 56)
-* \ (backslash), \' operator (gawk): GNU Regexp Operators.
- (line 58)
* \ (backslash), as field separator: Command Line Field Separator.
(line 24)
+* \ (backslash), continuing lines and: Statements/Lines. (line 19)
+* \ (backslash), continuing lines and, comments and: Statements/Lines.
+ (line 77)
+* \ (backslash), continuing lines and, in csh: Statements/Lines.
+ (line 45)
* \ (backslash), gsub()/gensub()/sub() functions and: Gory Details.
(line 6)
+* \ (backslash), in bracket expressions: Bracket Expressions. (line 25)
+* \ (backslash), in escape sequences: Escape Sequences. (line 6)
+* \ (backslash), in escape sequences <1>: Escape Sequences. (line 119)
+* \ (backslash), in escape sequences, POSIX and: Escape Sequences.
+ (line 123)
+* \ (backslash), in regexp constants: Computed Regexps. (line 30)
+* \ (backslash), in shell commands: Quoting. (line 48)
+* \ (backslash), regexp operator: Regexp Operator Details.
+ (line 14)
+* & (ampersand), && operator: Boolean Ops. (line 59)
+* & (ampersand), && operator <1>: Precedence. (line 85)
+* & (ampersand), gsub()/gensub()/sub() functions and: Gory Details.
+ (line 6)
+* # (number sign), #! (executable scripts): Executable Scripts.
+ (line 6)
+* # (number sign), commenting: Comments. (line 6)
+* % (percent sign), % operator: Precedence. (line 54)
+* % (percent sign), %= operator: Assignment Ops. (line 129)
+* % (percent sign), %= operator <1>: Precedence. (line 94)
+* ^ (caret), ^ operator: Precedence. (line 48)
+* ^ (caret), ^= operator: Assignment Ops. (line 129)
+* ^ (caret), ^= operator <1>: Precedence. (line 94)
+* ^ (caret), in bracket expressions: Bracket Expressions. (line 25)
+* ^ (caret), in FS: Regexp Field Splitting.
+ (line 58)
* ^ (caret), regexp operator: Regexp Operator Details.
(line 18)
-* ^ (caret), in bracket expressions: Bracket Expressions. (line 25)
* ^ (caret), regexp operator <1>: GNU Regexp Operators.
(line 61)
-* ^ (caret), in FS: Regexp Field Splitting.
- (line 58)
-* ^ (caret), ^= operator: Assignment Ops. (line 129)
-* ^ (caret), ^ operator: Precedence. (line 48)
-* ^ (caret), ^= operator <1>: Precedence. (line 94)
-* _ (underscore), in names of private variables: Library Names.
- (line 29)
-* _ (underscore), C macro: Explaining gettext. (line 71)
-* _ (underscore), translatable strings: Programmer i18n. (line 69)
-* _gr_init() user-defined function: Group Functions. (line 83)
-* _ord_init() user-defined function: Ordinal Functions. (line 16)
-* _pw_init() user-defined function: Passwd Functions. (line 105)
-* {} (braces), regexp operator: Regexp Operator Details.
- (line 118)
-* {} (braces), actions and: Action Overview. (line 19)
-* {} (braces), statements, grouping: Statements. (line 10)
-* {} (braces): Profiling. (line 142)
+* + (plus sign), + operator: Precedence. (line 51)
+* + (plus sign), + operator <1>: Precedence. (line 57)
+* + (plus sign), ++ operator: Increment Ops. (line 11)
+* + (plus sign), ++ operator <1>: Increment Ops. (line 40)
+* + (plus sign), ++ operator <2>: Precedence. (line 45)
+* + (plus sign), += operator: Assignment Ops. (line 81)
+* + (plus sign), += operator <1>: Precedence. (line 94)
+* + (plus sign), regexp operator: Regexp Operator Details.
+ (line 107)
+* < (left angle bracket), < operator: Comparison Operators.
+ (line 11)
+* < (left angle bracket), < operator <1>: Precedence. (line 64)
+* < (left angle bracket), < operator (I/O): Getline/File. (line 6)
+* < (left angle bracket), <= operator: Comparison Operators.
+ (line 11)
+* < (left angle bracket), <= operator <1>: Precedence. (line 64)
+* = (equals sign), = operator: Assignment Ops. (line 6)
+* = (equals sign), == operator: Comparison Operators.
+ (line 11)
+* = (equals sign), == operator <1>: Precedence. (line 64)
+* > (right angle bracket), > operator: Comparison Operators.
+ (line 11)
+* > (right angle bracket), > operator <1>: Precedence. (line 64)
+* > (right angle bracket), > operator (I/O): Redirection. (line 22)
+* > (right angle bracket), >= operator: Comparison Operators.
+ (line 11)
+* > (right angle bracket), >= operator <1>: Precedence. (line 64)
+* > (right angle bracket), >> operator (I/O): Redirection. (line 50)
+* > (right angle bracket), >> operator (I/O) <1>: Precedence. (line 64)
* | (vertical bar): Regexp Operator Details.
(line 66)
* | (vertical bar), | operator (I/O): Getline/Pipe. (line 10)
-* | (vertical bar), |& operator (I/O): Getline/Coprocess. (line 6)
* | (vertical bar), | operator (I/O) <1>: Redirection. (line 57)
+* | (vertical bar), | operator (I/O) <2>: Precedence. (line 64)
+* | (vertical bar), |& operator (I/O): Getline/Coprocess. (line 6)
* | (vertical bar), |& operator (I/O) <1>: Redirection. (line 96)
+* | (vertical bar), |& operator (I/O) <2>: Precedence. (line 64)
+* | (vertical bar), |& operator (I/O) <3>: Two-way I/O. (line 27)
* | (vertical bar), |& operator (I/O), pipes, closing: Close Files And Pipes.
(line 124)
* | (vertical bar), || operator: Boolean Ops. (line 59)
-* | (vertical bar), | operator (I/O) <2>: Precedence. (line 64)
-* | (vertical bar), |& operator (I/O) <2>: Precedence. (line 64)
* | (vertical bar), || operator <1>: Precedence. (line 88)
-* | (vertical bar), |& operator (I/O) <3>: Two-way I/O. (line 27)
* ~ (tilde), ~ operator: Regexp Usage. (line 19)
* ~ (tilde), ~ operator <1>: Computed Regexps. (line 6)
* ~ (tilde), ~ operator <2>: Case-sensitivity. (line 26)
@@ -36368,56 +36326,62 @@ Index
* ~ (tilde), ~ operator <4>: Comparison Operators.
(line 11)
* ~ (tilde), ~ operator <5>: Comparison Operators.
- (line 99)
+ (line 98)
* ~ (tilde), ~ operator <6>: Precedence. (line 79)
* ~ (tilde), ~ operator <7>: Expression Patterns. (line 24)
+* $ (dollar sign), $ field operator: Fields. (line 19)
+* $ (dollar sign), $ field operator <1>: Precedence. (line 42)
+* $ (dollar sign), incrementing fields and arrays: Increment Ops.
+ (line 30)
+* $ (dollar sign), regexp operator: Regexp Operator Details.
+ (line 31)
* aaa (amazing awk assembler) program: Glossary. (line 16)
* accessing fields: Fields. (line 6)
* accessing global variables from extensions: Symbol Table Access.
(line 6)
* account information: Passwd Functions. (line 16)
* account information <1>: Group Functions. (line 6)
-* actions, default: Very Simple. (line 34)
-* actions, empty: Very Simple. (line 39)
* actions: Action Overview. (line 6)
* actions, control statements in: Statements. (line 6)
+* actions, default: Very Simple. (line 34)
+* actions, empty: Very Simple. (line 39)
* Ada programming language: Glossary. (line 11)
-* adding, fields: Changing Fields. (line 53)
* adding, features to gawk: Adding Code. (line 6)
+* adding, fields: Changing Fields. (line 53)
* advanced features, fixed-width data: Constant Size. (line 6)
-* advanced features, specifying field content: Splitting By Content.
- (line 17)
* advanced features, gawk: Advanced Features. (line 6)
+* advanced features, network programming: TCP/IP Networking. (line 6)
* advanced features, nondecimal input data: Nondecimal Data. (line 6)
* advanced features, processes, communicating with: Two-way I/O.
(line 6)
-* advanced features, network programming: TCP/IP Networking. (line 6)
+* advanced features, specifying field content: Splitting By Content.
+ (line 17)
* Aho, Alfred: History. (line 21)
* Aho, Alfred <1>: Contributors. (line 12)
* alarm clock example program: Alarm Program. (line 11)
* alarm.awk program: Alarm Program. (line 31)
-* algorithms: Basic High Level. (line 59)
+* algorithms: Basic High Level. (line 70)
* all source files, show in debugger: Debugger Info. (line 45)
* allocating memory for extensions: Memory Allocation Functions.
(line 6)
* amazing awk assembler (aaa): Glossary. (line 16)
* amazingly workable formatter (awf): Glossary. (line 23)
* ambiguity, syntactic: /= operator vs. /=.../ regexp constant: Assignment Ops.
- (line 150)
+ (line 149)
* ampersand (&), && operator: Boolean Ops. (line 59)
* ampersand (&), && operator <1>: Precedence. (line 85)
* ampersand (&), gsub()/gensub()/sub() functions and: Gory Details.
(line 6)
* anagram.awk program: Anagram Program. (line 21)
* anagrams, finding: Anagram Program. (line 6)
-* and: Bitwise Functions. (line 41)
+* and: Bitwise Functions. (line 40)
* AND bitwise operation: Bitwise Functions. (line 6)
* and Boolean-logic operator: Boolean Ops. (line 6)
* ANSI: Glossary. (line 32)
-* API, version: Extension Versioning.
- (line 6)
* API, informational variables: Extension API Informational Variables.
(line 6)
+* API, version: Extension Versioning.
+ (line 6)
* API, ownership of MPFR and GMP values: API Ownership of MPFR and GMP Values.
(line 6)
* arbitrary precision: Arbitrary Precision Arithmetic.
@@ -36427,18 +36391,18 @@ Index
(line 6)
* archaeologists: Bugs. (line 6)
* arctangent: Numeric Functions. (line 11)
-* ARGC/ARGV variables, portability and: Executable Scripts. (line 55)
+* ARGC/ARGV variables: Auto-set. (line 15)
* ARGC/ARGV variables, command-line arguments: Other Arguments.
(line 21)
-* ARGC/ARGV variables: Auto-set. (line 15)
* ARGC/ARGV variables, how to use: ARGC and ARGV. (line 6)
-* ARGIND variable, command-line arguments: Other Arguments. (line 21)
+* ARGC/ARGV variables, portability and: Executable Scripts. (line 55)
* ARGIND variable: Auto-set. (line 44)
-* arguments, command-line, invoking awk: Command Line. (line 6)
+* ARGIND variable, command-line arguments: Other Arguments. (line 21)
* arguments, command-line: Other Arguments. (line 6)
-* arguments, in function calls: Function Calls. (line 18)
* arguments, command-line <1>: Auto-set. (line 15)
* arguments, command-line <2>: ARGC and ARGV. (line 6)
+* arguments, command-line, invoking awk: Command Line. (line 6)
+* arguments, in function calls: Function Calls. (line 18)
* arguments, processing: Getopt Function. (line 6)
* ARGV array: Options. (line 340)
* ARGV array, indexing into: Other Arguments. (line 21)
@@ -36448,52 +36412,52 @@ Index
(line 6)
* array scanning order, controlling: Controlling Scanning.
(line 14)
-* array subscripts, numbers as: Numeric Array Subscripts.
- (line 6)
* array subscripts, null string as: Uninitialized Subscripts.
(line 43)
-* arrays: Arrays. (line 6)
-* arrays, indexing: Array Intro. (line 49)
-* arrays, associative: Array Intro. (line 49)
-* arrays, sparse: Array Intro. (line 76)
-* arrays, IGNORECASE variable and: Array Intro. (line 100)
-* arrays, referencing elements: Reference to Elements.
+* array subscripts, numbers as: Numeric Array Subscripts.
(line 6)
-* arrays, unassigned elements: Reference to Elements.
- (line 18)
-* arrays, elements, that donât exist: Reference to Elements.
- (line 23)
+* arrays: Arrays. (line 6)
+* arrays, arrays of arrays: Arrays of Arrays. (line 6)
+* arrays, as parameters to functions: Pass By Value/Reference.
+ (line 44)
+* arrays, associative: Array Intro. (line 51)
+* arrays, associative, library functions and: Library Names. (line 58)
+* arrays, deleting entire contents: Delete. (line 39)
* arrays, elements, assigning values: Assigning Elements. (line 6)
-* arrays, example of using: Array Example. (line 6)
-* arrays, scanning: Scanning an Array. (line 6)
-* arrays, for statement and: Scanning an Array. (line 20)
+* arrays, elements, deleting: Delete. (line 6)
* arrays, elements, order of access by in operator: Scanning an Array.
(line 48)
-* arrays, numeric subscripts: Numeric Array Subscripts.
- (line 6)
-* arrays, subscripts, uninitialized variables as: Uninitialized Subscripts.
- (line 6)
-* arrays, elements, deleting: Delete. (line 6)
-* arrays, deleting entire contents: Delete. (line 39)
+* arrays, elements, retrieving number of: String Functions. (line 41)
+* arrays, elements, that don't exist: Reference to Elements.
+ (line 23)
+* arrays, example of using: Array Example. (line 6)
+* arrays, for statement and: Scanning an Array. (line 20)
+* arrays, IGNORECASE variable and: Array Intro. (line 102)
+* arrays, indexing: Array Intro. (line 51)
+* arrays, merging into strings: Join Function. (line 6)
* arrays, multidimensional: Multidimensional. (line 10)
* arrays, multidimensional, scanning: Multiscanning. (line 11)
-* arrays, arrays of arrays: Arrays of Arrays. (line 6)
-* arrays, elements, retrieving number of: String Functions. (line 41)
* arrays, number of elements: String Functions. (line 219)
-* arrays, as parameters to functions: Pass By Value/Reference.
- (line 44)
-* arrays, associative, library functions and: Library Names. (line 58)
-* arrays, merging into strings: Join Function. (line 6)
+* arrays, numeric subscripts: Numeric Array Subscripts.
+ (line 6)
+* arrays, referencing elements: Reference to Elements.
+ (line 6)
+* arrays, scanning: Scanning an Array. (line 6)
* arrays, sorting, asort() function (gawk): Array Sorting Functions.
(line 6)
* arrays, sorting, asorti() function (gawk): Array Sorting Functions.
(line 6)
* arrays, sorting, IGNORECASE variable and: Array Sorting Functions.
(line 88)
+* arrays, sparse: Array Intro. (line 78)
+* arrays, subscripts, uninitialized variables as: Uninitialized Subscripts.
+ (line 6)
+* arrays, unassigned elements: Reference to Elements.
+ (line 18)
* artificial intelligence, gawk and: Distribution contents.
(line 64)
* ASCII: Escape Sequences. (line 31)
-* ASCII <1>: Bracket Expressions. (line 80)
+* ASCII <1>: Bracket Expressions. (line 79)
* ASCII <2>: Scalar Constants. (line 20)
* ASCII <3>: Ordinal Functions. (line 45)
* ASCII <4>: Alarm Program. (line 20)
@@ -36523,27 +36487,27 @@ Index
* assign values to variables, in debugger: Viewing And Changing Data.
(line 62)
* assignment operators: Assignment Ops. (line 6)
-* assignment operators, lvalues/rvalues: Assignment Ops. (line 31)
* assignment operators, evaluation order: Assignment Ops. (line 110)
+* assignment operators, lvalues/rvalues: Assignment Ops. (line 31)
* assignments as file names: Ignoring Assigns. (line 6)
-* associative arrays: Array Intro. (line 49)
+* associative arrays: Array Intro. (line 51)
+* asterisk (*), * operator, as multiplication operator: Precedence.
+ (line 54)
* asterisk (*), * operator, as regexp operator: Regexp Operator Details.
(line 91)
+* asterisk (*), * operator, null strings, matching: String Functions.
+ (line 574)
* asterisk (*), ** operator: Arithmetic Ops. (line 85)
-* asterisk (*), *= operator: Assignment Ops. (line 129)
-* asterisk (*), **= operator: Assignment Ops. (line 129)
* asterisk (*), ** operator <1>: Precedence. (line 48)
-* asterisk (*), * operator, as multiplication operator: Precedence.
- (line 54)
-* asterisk (*), *= operator <1>: Precedence. (line 94)
+* asterisk (*), **= operator: Assignment Ops. (line 129)
* asterisk (*), **= operator <1>: Precedence. (line 94)
-* asterisk (*), * operator, null strings, matching: String Functions.
- (line 575)
+* asterisk (*), *= operator: Assignment Ops. (line 129)
+* asterisk (*), *= operator <1>: Precedence. (line 94)
+* at-sign (@), @-notation for indirect function calls: Indirect Calls.
+ (line 47)
* at-sign (@), @include directive: Include Files. (line 8)
* at-sign (@), @load directive: Loading Shared Libraries.
(line 8)
-* at-sign (@), @-notation for indirect function calls: Indirect Calls.
- (line 47)
* at-sign (@), @namespace directive: Changing The Namespace.
(line 6)
* at-sign (@), @namespace directive, BEGIN, BEGINFILE, END, ENDFILE and:
Changing The Namespace.
@@ -36552,25 +36516,15 @@ Index
* automatic displays, in debugger: Debugger Info. (line 24)
* awf (amazingly workable formatter) program: Glossary. (line 23)
* awk: Preface. (line 6)
-* awk, POSIX and: Preface. (line 21)
-* awk, POSIX and <1>: Preface. (line 21)
+* awk, function of: Getting Started. (line 6)
* awk, gawk and: Preface. (line 21)
-* awk, uses for: Preface. (line 21)
-* awk, history of: History. (line 21)
-* awk, new vs. old: Names. (line 6)
-* awk, terms describing: This Manual. (line 6)
* awk, gawk and <1>: This Manual. (line 14)
-* awk, function of: Getting Started. (line 6)
-* awk, uses for <1>: Getting Started. (line 12)
-* awk, uses for <2>: When. (line 6)
-* awk, invoking: Command Line. (line 6)
-* awk, profiling, enabling: Options. (line 296)
-* awk, implementations, limits: Getline Notes. (line 14)
+* awk, history of: History. (line 21)
* awk, implementation issues, pipes: Redirection. (line 129)
-* awk, new vs. old, OFMT variable: Strings And Numbers. (line 56)
-* awk, language, POSIX version: Assignment Ops. (line 139)
-* awk, regexp constants and: Comparison Operators.
- (line 104)
+* awk, implementations: Other Versions. (line 6)
+* awk, implementations, limits: Getline Notes. (line 14)
+* awk, invoking: Command Line. (line 6)
+* awk, language, POSIX version: Assignment Ops. (line 138)
* awk, language, POSIX version <1>: Next Statement. (line 44)
* awk, language, POSIX version <2>: Definition Syntax. (line 99)
* awk, namespace: Default Namespace. (line 6)
@@ -36578,39 +36532,51 @@ Index
(line 6)
* awk, namespace, use for indirect function calls: Internal Name Management.
(line 6)
+* awk, new vs. old: Names. (line 6)
+* awk, new vs. old, OFMT variable: Strings And Numbers. (line 55)
+* awk, POSIX and: Preface. (line 21)
+* awk, POSIX and <1>: Preface. (line 21)
+* awk, profiling, enabling: Options. (line 296)
+* awk, regexp constants and: Comparison Operators.
+ (line 103)
+* awk, terms describing: This Manual. (line 6)
+* awk, uses for: Preface. (line 21)
+* awk, uses for <1>: Getting Started. (line 12)
+* awk, uses for <2>: When. (line 6)
* awk, versions of: V7/SVR3.1. (line 6)
-* awk, versions of, changes between V7 and SVR3.1: V7/SVR3.1. (line 6)
+* awk, versions of <1>: BTL. (line 6)
+* awk, versions of <2>: Other Versions. (line 13)
* awk, versions of, changes between SVR3.1 and SVR4: SVR4. (line 6)
* awk, versions of, changes between SVR4 and POSIX awk: POSIX.
(line 6)
-* awk, versions of <1>: BTL. (line 6)
-* awk, implementations: Other Versions. (line 6)
-* awk, versions of <2>: Other Versions. (line 13)
+* awk, versions of, changes between V7 and SVR3.1: V7/SVR3.1. (line 6)
* awk programs: Getting Started. (line 12)
-* awk programs, running: Running gawk. (line 6)
-* awk programs, running, from shell scripts: One-shot. (line 22)
-* awk programs, running, without input files: Read Terminal. (line 16)
-* awk programs, running <1>: Long. (line 6)
-* awk programs, lengthy: Long. (line 6)
* awk programs <1>: Executable Scripts. (line 6)
-* awk programs, documenting: Comments. (line 6)
-* awk programs, one-line examples: Very Simple. (line 45)
* awk programs <2>: Two Rules. (line 6)
* awk programs, complex: When. (line 27)
-* awk programs, location of: Options. (line 25)
* awk programs, debugging, enabling: Options. (line 111)
-* awk programs, location of <1>: Options. (line 146)
-* awk programs, location of <2>: Options. (line 180)
-* awk programs, shell variables in: Using Shell Variables.
- (line 6)
+* awk programs, documenting: Comments. (line 6)
+* awk programs, documenting <1>: Library Names. (line 6)
+* awk programs, examples of: Sample Programs. (line 6)
* awk programs, execution of: Next Statement. (line 16)
* awk programs, internationalizing: I18N Functions. (line 6)
-* awk programs, documenting <1>: Library Names. (line 6)
+* awk programs, internationalizing <1>: Programmer i18n. (line 6)
+* awk programs, lengthy: Long. (line 6)
* awk programs, lengthy, assertions: Assert Function. (line 6)
-* awk programs, examples of: Sample Programs. (line 6)
+* awk programs, location of: Options. (line 25)
+* awk programs, location of <1>: Options. (line 146)
+* awk programs, location of <2>: Options. (line 180)
+* awk programs, one-line examples: Very Simple. (line 45)
* awk programs, profiling: Profiling. (line 6)
-* awk programs, internationalizing <1>: Programmer i18n. (line 6)
+* awk programs, running: Running gawk. (line 6)
+* awk programs, running <1>: Long. (line 6)
+* awk programs, running, from shell scripts: One-shot. (line 22)
+* awk programs, running, without input files: Read Terminal. (line 16)
+* awk programs, shell variables in: Using Shell Variables.
+ (line 6)
* awk to Go translator: Other Versions. (line 133)
+* AWK_HASH environment variable: Other Environment Variables.
+ (line 50)
* awka compiler for awk: Other Versions. (line 64)
* AWKBUFSIZE environment variable: Other Environment Variables.
(line 41)
@@ -36646,92 +36612,90 @@ Index
(line 57)
* awksed.awk program: Simple Sed. (line 25)
* awkvars.out file: Options. (line 97)
-* AWK_HASH environment variable: Other Environment Variables.
- (line 50)
* b debugger command (alias for break): Breakpoint Control. (line 11)
* backslash (\): Comments. (line 50)
-* backslash (\), in shell commands: Quoting. (line 48)
-* backslash (\), continuing lines and: Statements/Lines. (line 19)
-* backslash (\), continuing lines and, in csh: Statements/Lines.
- (line 45)
-* backslash (\), continuing lines and, comments and: Statements/Lines.
- (line 77)
-* backslash (\), in escape sequences: Escape Sequences. (line 6)
+* backslash (\), \' operator (gawk): GNU Regexp Operators.
+ (line 58)
+* backslash (\), \" escape sequence: Escape Sequences. (line 101)
+* backslash (\), \/ escape sequence: Escape Sequences. (line 92)
+* backslash (\), \` operator (gawk): GNU Regexp Operators.
+ (line 56)
+* backslash (\), \< operator (gawk): GNU Regexp Operators.
+ (line 30)
+* backslash (\), \> operator (gawk): GNU Regexp Operators.
+ (line 34)
* backslash (\), \a escape sequence: Escape Sequences. (line 34)
* backslash (\), \b escape sequence: Escape Sequences. (line 38)
+* backslash (\), \B operator (gawk): GNU Regexp Operators.
+ (line 43)
* backslash (\), \f escape sequence: Escape Sequences. (line 41)
* backslash (\), \n escape sequence: Escape Sequences. (line 44)
-* backslash (\), \r escape sequence: Escape Sequences. (line 47)
-* backslash (\), \t escape sequence: Escape Sequences. (line 50)
-* backslash (\), \v escape sequence: Escape Sequences. (line 53)
* backslash (\), \NNN escape sequence: Escape Sequences. (line 56)
-* backslash (\), \x escape sequence: Escape Sequences. (line 61)
-* backslash (\), \u escape sequence: Escape Sequences. (line 76)
-* backslash (\), \/ escape sequence: Escape Sequences. (line 92)
-* backslash (\), \" escape sequence: Escape Sequences. (line 101)
-* backslash (\), in escape sequences <1>: Escape Sequences. (line 119)
-* backslash (\), in escape sequences, POSIX and: Escape Sequences.
- (line 124)
-* backslash (\), regexp operator: Regexp Operator Details.
- (line 14)
-* backslash (\), in bracket expressions: Bracket Expressions. (line 25)
-* backslash (\), in regexp constants: Computed Regexps. (line 30)
+* backslash (\), \r escape sequence: Escape Sequences. (line 47)
* backslash (\), \s operator (gawk): GNU Regexp Operators.
(line 13)
* backslash (\), \S operator (gawk): GNU Regexp Operators.
(line 17)
+* backslash (\), \t escape sequence: Escape Sequences. (line 50)
+* backslash (\), \u escape sequence: Escape Sequences. (line 76)
+* backslash (\), \v escape sequence: Escape Sequences. (line 53)
* backslash (\), \w operator (gawk): GNU Regexp Operators.
(line 21)
* backslash (\), \W operator (gawk): GNU Regexp Operators.
(line 26)
-* backslash (\), \< operator (gawk): GNU Regexp Operators.
- (line 30)
-* backslash (\), \> operator (gawk): GNU Regexp Operators.
- (line 34)
+* backslash (\), \x escape sequence: Escape Sequences. (line 61)
* backslash (\), \y operator (gawk): GNU Regexp Operators.
(line 38)
-* backslash (\), \B operator (gawk): GNU Regexp Operators.
- (line 43)
-* backslash (\), \` operator (gawk): GNU Regexp Operators.
- (line 56)
-* backslash (\), \' operator (gawk): GNU Regexp Operators.
- (line 58)
* backslash (\), as field separator: Command Line Field Separator.
(line 24)
+* backslash (\), continuing lines and: Statements/Lines. (line 19)
+* backslash (\), continuing lines and, comments and: Statements/Lines.
+ (line 77)
+* backslash (\), continuing lines and, in csh: Statements/Lines.
+ (line 45)
* backslash (\), gsub()/gensub()/sub() functions and: Gory Details.
(line 6)
+* backslash (\), in bracket expressions: Bracket Expressions. (line 25)
+* backslash (\), in escape sequences: Escape Sequences. (line 6)
+* backslash (\), in escape sequences <1>: Escape Sequences. (line 119)
+* backslash (\), in escape sequences, POSIX and: Escape Sequences.
+ (line 123)
+* backslash (\), in regexp constants: Computed Regexps. (line 30)
+* backslash (\), in shell commands: Quoting. (line 48)
+* backslash (\), regexp operator: Regexp Operator Details.
+ (line 14)
* backtrace debugger command: Execution Stack. (line 13)
* Beebe, Nelson H.F.: Acknowledgments. (line 60)
* Beebe, Nelson H.F. <1>: Numeric Functions. (line 32)
* Beebe, Nelson H.F. <2>: Other Versions. (line 82)
* BEGIN pattern: Field Separators. (line 45)
-* BEGIN pattern, getline and: Getline Notes. (line 19)
-* BEGIN pattern, headings, adding: Print Examples. (line 42)
-* BEGIN pattern, OFS/ORS variables, assigning values to: Output Separators.
- (line 20)
-* BEGIN pattern, Boolean patterns and: Expression Patterns. (line 70)
* BEGIN pattern <1>: BEGIN/END. (line 6)
* BEGIN pattern <2>: Using BEGIN/END. (line 6)
-* BEGIN pattern, operators and: Using BEGIN/END. (line 17)
-* BEGIN pattern, print statement and: I/O And BEGIN/END. (line 15)
+* BEGIN pattern, @namespace directive and: Changing The Namespace.
+ (line 37)
+* BEGIN pattern, assert() user-defined function and: Assert Function.
+ (line 83)
+* BEGIN pattern, Boolean patterns and: Expression Patterns. (line 70)
+* BEGIN pattern, exit statement and: Exit Statement. (line 12)
+* BEGIN pattern, getline and: Getline Notes. (line 19)
+* BEGIN pattern, headings, adding: Print Examples. (line 42)
* BEGIN pattern, next/nextfile statements and: I/O And BEGIN/END.
(line 36)
* BEGIN pattern, next/nextfile statements and <1>: Next Statement.
(line 44)
-* BEGIN pattern, exit statement and: Exit Statement. (line 12)
-* BEGIN pattern, assert() user-defined function and: Assert Function.
- (line 83)
+* BEGIN pattern, OFS/ORS variables, assigning values to: Output Separators.
+ (line 20)
+* BEGIN pattern, operators and: Using BEGIN/END. (line 17)
+* BEGIN pattern, print statement and: I/O And BEGIN/END. (line 15)
+* BEGIN pattern, profiling and: Profiling. (line 62)
* BEGIN pattern, pwcat program: Passwd Functions. (line 143)
* BEGIN pattern, running awk programs and: Cut Program. (line 67)
-* BEGIN pattern, profiling and: Profiling. (line 62)
* BEGIN pattern, TEXTDOMAIN variable and: Programmer i18n. (line 60)
-* BEGIN pattern, @namespace directive and: Changing The Namespace.
- (line 37)
-* BEGINFILE pattern, Boolean patterns and: Expression Patterns.
- (line 70)
* BEGINFILE pattern: BEGINFILE/ENDFILE. (line 6)
* BEGINFILE pattern, @namespace directive and: Changing The Namespace.
(line 37)
+* BEGINFILE pattern, Boolean patterns and: Expression Patterns.
+ (line 70)
* beginfile() user-defined function: Filetrans Function. (line 62)
* Bentley, Jon: Glossary. (line 204)
* Benzinger, Michael: Contributors. (line 100)
@@ -36747,52 +36711,52 @@ Index
* BINMODE variable: User-modified. (line 15)
* BINMODE variable <1>: PC Using. (line 18)
* bit-manipulation functions: Bitwise Functions. (line 6)
-* bits2str() user-defined function: Bitwise Functions. (line 70)
+* bits2str() user-defined function: Bitwise Functions. (line 69)
+* bitwise, AND: Bitwise Functions. (line 40)
+* bitwise, complement: Bitwise Functions. (line 25)
+* bitwise, complement <1>: Bitwise Functions. (line 44)
* bitwise, operations: Bitwise Functions. (line 6)
-* bitwise, complement: Bitwise Functions. (line 26)
-* bitwise, shift: Bitwise Functions. (line 33)
-* bitwise, AND: Bitwise Functions. (line 41)
-* bitwise, complement <1>: Bitwise Functions. (line 45)
-* bitwise, OR: Bitwise Functions. (line 51)
-* bitwise, XOR: Bitwise Functions. (line 58)
+* bitwise, OR: Bitwise Functions. (line 50)
+* bitwise, shift: Bitwise Functions. (line 32)
+* bitwise, XOR: Bitwise Functions. (line 57)
* body, in actions: Statements. (line 10)
* body, in loops: While Statement. (line 14)
* Boolean expressions: Boolean Ops. (line 6)
* Boolean expressions, as patterns: Expression Patterns. (line 39)
* boolean function: Boolean Functions. (line 6)
* Bourne shell, quoting rules for: Quoting. (line 18)
+* braces ({}): Profiling. (line 142)
+* braces ({}), actions and: Action Overview. (line 19)
* braces ({}), regexp operator: Regexp Operator Details.
(line 118)
-* braces ({}), actions and: Action Overview. (line 19)
* braces ({}), statements, grouping: Statements. (line 10)
-* braces ({}): Profiling. (line 142)
* bracket expressions: Regexp Operator Details.
(line 52)
-* bracket expressions, complemented: Regexp Operator Details.
- (line 60)
* bracket expressions <1>: Bracket Expressions. (line 6)
-* bracket expressions, range expressions: Bracket Expressions.
- (line 6)
-* bracket expressions, character lists: Bracket Expressions. (line 6)
* bracket expressions, character classes: Bracket Expressions.
(line 40)
+* bracket expressions, character lists: Bracket Expressions. (line 6)
* bracket expressions, collating elements: Bracket Expressions.
- (line 91)
-* bracket expressions, non-ASCII: Bracket Expressions. (line 91)
+ (line 90)
* bracket expressions, collating symbols: Bracket Expressions.
- (line 98)
+ (line 97)
+* bracket expressions, complemented: Regexp Operator Details.
+ (line 60)
* bracket expressions, equivalence classes: Bracket Expressions.
- (line 104)
+ (line 103)
+* bracket expressions, non-ASCII: Bracket Expressions. (line 90)
+* bracket expressions, range expressions: Bracket Expressions.
+ (line 6)
* break debugger command: Breakpoint Control. (line 11)
* break statement: Break Statement. (line 6)
* breakpoint: Debugging Terms. (line 33)
-* breakpoint, setting: Breakpoint Control. (line 11)
* breakpoint, at location, how to delete: Breakpoint Control. (line 36)
+* breakpoint, commands to execute at: Debugger Execution Control.
+ (line 10)
* breakpoint, condition: Breakpoint Control. (line 54)
* breakpoint, delete by number: Breakpoint Control. (line 64)
* breakpoint, how to disable or enable: Breakpoint Control. (line 69)
-* breakpoint, commands to execute at: Debugger Execution Control.
- (line 10)
+* breakpoint, setting: Breakpoint Control. (line 11)
* breakpoint, show all in debugger: Debugger Info. (line 21)
* Brennan, Michael: Foreword3. (line 84)
* Brennan, Michael <1>: Foreword4. (line 33)
@@ -36801,25 +36765,25 @@ Index
* Brennan, Michael <4>: Simple Sed. (line 25)
* Brennan, Michael <5>: Other Versions. (line 6)
* Brennan, Michael <6>: Other Versions. (line 39)
-* Brian Kernighanâs awk: When. (line 21)
-* Brian Kernighanâs awk <1>: Escape Sequences. (line 128)
-* Brian Kernighanâs awk <2>: GNU Regexp Operators.
+* Brian Kernighan's awk: When. (line 21)
+* Brian Kernighan's awk <1>: Escape Sequences. (line 128)
+* Brian Kernighan's awk <2>: GNU Regexp Operators.
(line 84)
-* Brian Kernighanâs awk <3>: gawk split records. (line 71)
-* Brian Kernighanâs awk <4>: Regexp Field Splitting.
+* Brian Kernighan's awk <3>: gawk split records. (line 70)
+* Brian Kernighan's awk <4>: Regexp Field Splitting.
(line 66)
-* Brian Kernighanâs awk <5>: Getline/Pipe. (line 62)
-* Brian Kernighanâs awk <6>: Concatenation. (line 36)
-* Brian Kernighanâs awk <7>: I/O And BEGIN/END. (line 15)
-* Brian Kernighanâs awk <8>: Break Statement. (line 51)
-* Brian Kernighanâs awk <9>: Continue Statement. (line 44)
-* Brian Kernighanâs awk <10>: Nextfile Statement. (line 47)
-* Brian Kernighanâs awk <11>: Delete. (line 51)
-* Brian Kernighanâs awk <12>: String Functions. (line 522)
-* Brian Kernighanâs awk <13>: Gory Details. (line 22)
-* Brian Kernighanâs awk <14>: I/O Functions. (line 43)
-* Brian Kernighanâs awk, extensions: BTL. (line 6)
-* Brian Kernighanâs awk, source code: Other Versions. (line 13)
+* Brian Kernighan's awk <5>: Getline/Pipe. (line 62)
+* Brian Kernighan's awk <6>: Concatenation. (line 36)
+* Brian Kernighan's awk <7>: I/O And BEGIN/END. (line 15)
+* Brian Kernighan's awk <8>: Break Statement. (line 51)
+* Brian Kernighan's awk <9>: Continue Statement. (line 44)
+* Brian Kernighan's awk <10>: Nextfile Statement. (line 47)
+* Brian Kernighan's awk <11>: Delete. (line 51)
+* Brian Kernighan's awk <12>: String Functions. (line 522)
+* Brian Kernighan's awk <13>: Gory Details. (line 22)
+* Brian Kernighan's awk <14>: I/O Functions. (line 43)
+* Brian Kernighan's awk, extensions: BTL. (line 6)
+* Brian Kernighan's awk, source code: Other Versions. (line 13)
* Brini, Davide: Signature Program. (line 6)
* Brink, Jeroen: DOS Quoting. (line 10)
* Broder, Alan J.: Contributors. (line 91)
@@ -36829,13 +36793,13 @@ Index
* Buening, Andreas: Acknowledgments. (line 60)
* Buening, Andreas <1>: Contributors. (line 95)
* Buening, Andreas <2>: Maintainers. (line 14)
-* buffering, interactive vs. noninteractive: I/O Functions. (line 75)
-* buffering, input/output: I/O Functions. (line 168)
+* buffering, input/output: I/O Functions. (line 166)
* buffering, input/output <1>: Two-way I/O. (line 53)
+* buffering, interactive vs. noninteractive: I/O Functions. (line 74)
+* buffers, flushing: I/O Functions. (line 32)
+* buffers, flushing <1>: I/O Functions. (line 166)
* buffers, operators for: GNU Regexp Operators.
(line 50)
-* buffers, flushing: I/O Functions. (line 32)
-* buffers, flushing <1>: I/O Functions. (line 168)
* bug reports, email address, <bug-gawk@gnu.org>: Bug address.
(line 52)
* <bug-gawk@gnu.org> bug reporting address: Bug address. (line 52)
@@ -36846,51 +36810,51 @@ Index
(line 27)
* bytes, counting: Wc Program. (line 6)
* C library functions, assert(): Assert Function. (line 6)
-* C library functions, getopt(): Getopt Function. (line 15)
-* C library functions, getpwent(): Passwd Functions. (line 16)
-* C library functions, getpwnam(): Passwd Functions. (line 174)
-* C library functions, getpwuid(): Passwd Functions. (line 185)
-* C library functions, getpwent() <1>: Passwd Functions. (line 195)
+* C library functions, bindtextdomain(): Explaining gettext. (line 50)
+* C library functions, endgrent(): Group Functions. (line 211)
* C library functions, endpwent(): Passwd Functions. (line 207)
+* C library functions, getaddrinfo(): TCP/IP Networking. (line 39)
* C library functions, getgrent(): Group Functions. (line 6)
-* C library functions, getgrnam(): Group Functions. (line 171)
+* C library functions, getgrent() <1>: Group Functions. (line 200)
* C library functions, getgrgid(): Group Functions. (line 182)
+* C library functions, getgrnam(): Group Functions. (line 171)
* C library functions, getgruser(): Group Functions. (line 191)
-* C library functions, getgrent() <1>: Group Functions. (line 200)
-* C library functions, endgrent(): Group Functions. (line 211)
-* C library functions, getaddrinfo(): TCP/IP Networking. (line 39)
-* C library functions, textdomain(): Explaining gettext. (line 28)
-* C library functions, bindtextdomain(): Explaining gettext. (line 50)
+* C library functions, getopt(): Getopt Function. (line 15)
+* C library functions, getpwent(): Passwd Functions. (line 16)
+* C library functions, getpwent() <1>: Passwd Functions. (line 195)
+* C library functions, getpwnam(): Passwd Functions. (line 174)
+* C library functions, getpwuid(): Passwd Functions. (line 185)
* C library functions, gettext(): Explaining gettext. (line 63)
+* C library functions, textdomain(): Explaining gettext. (line 28)
* call by reference: Pass By Value/Reference.
(line 44)
* call by value: Pass By Value/Reference.
(line 15)
-* call stack, explanation of: Debugging Terms. (line 10)
* call stack, display in debugger: Execution Stack. (line 13)
+* call stack, explanation of: Debugging Terms. (line 10)
+* caret (^), ^ operator: Precedence. (line 48)
+* caret (^), ^= operator: Assignment Ops. (line 129)
+* caret (^), ^= operator <1>: Precedence. (line 94)
+* caret (^), in bracket expressions: Bracket Expressions. (line 25)
* caret (^), regexp operator: Regexp Operator Details.
(line 18)
-* caret (^), in bracket expressions: Bracket Expressions. (line 25)
* caret (^), regexp operator <1>: GNU Regexp Operators.
(line 61)
-* caret (^), ^= operator: Assignment Ops. (line 129)
-* caret (^), ^ operator: Precedence. (line 48)
-* caret (^), ^= operator <1>: Precedence. (line 94)
* case keyword: Switch Statement. (line 6)
-* case sensitivity, regexps and: Case-sensitivity. (line 6)
-* case sensitivity, gawk: Case-sensitivity. (line 26)
-* case sensitivity, string comparisons and: User-modified. (line 79)
-* case sensitivity, regexps and <1>: User-modified. (line 79)
-* case sensitivity, array indices and: Array Intro. (line 100)
+* case sensitivity, array indices and: Array Intro. (line 102)
* case sensitivity, converting case: String Functions. (line 552)
* case sensitivity, example programs: Library Functions. (line 50)
+* case sensitivity, gawk: Case-sensitivity. (line 26)
+* case sensitivity, regexps and: Case-sensitivity. (line 6)
+* case sensitivity, regexps and <1>: User-modified. (line 79)
+* case sensitivity, string comparisons and: User-modified. (line 79)
* CGI, awk scripts for: Options. (line 146)
* character sets (machine character encodings): Ordinal Functions.
(line 45)
* character sets (machine character encodings) <1>: Glossary. (line 194)
-* characters, values of as numbers: Ordinal Functions. (line 6)
* characters, counting: Wc Program. (line 6)
* characters, transliterating: Translate Program. (line 6)
+* characters, values of as numbers: Ordinal Functions. (line 6)
* Chassell, Robert J.: Acknowledgments. (line 33)
* chdir() extension function: Extension Sample File Functions.
(line 12)
@@ -36908,93 +36872,93 @@ Index
(line 22)
* close <1>: I/O Functions. (line 10)
* close file or coprocess: I/O Functions. (line 10)
+* Close, Diane: Manual History. (line 34)
+* Close, Diane <1>: Contributors. (line 21)
* close() function, portability: Close Files And Pipes.
(line 85)
* close() function, return value: Close Return Value. (line 6)
* close() function, two-way pipes and: Two-way I/O. (line 60)
-* Close, Diane: Manual History. (line 34)
-* Close, Diane <1>: Contributors. (line 21)
* Collado, Manuel: Acknowledgments. (line 60)
* Collado, Manuel <1>: More CSV. (line 6)
* Collado, Manuel <2>: More CSV. (line 52)
-* collating elements: Bracket Expressions. (line 91)
-* collating symbols: Bracket Expressions. (line 98)
+* collating elements: Bracket Expressions. (line 90)
+* collating symbols: Bracket Expressions. (line 97)
* Colombo, Antonio: Acknowledgments. (line 60)
* Colombo, Antonio <1>: Contributors. (line 143)
-* colon (:), ?: operator: Precedence. (line 91)
* colon (:), :: namespace separator: Qualified Names. (line 6)
+* colon (:), ?: operator: Precedence. (line 91)
* columns, aligning: Print Examples. (line 69)
* columns, cutting: Cut Program. (line 6)
* comma (,), in range patterns: Ranges. (line 6)
-* comma separated values (CSV) data, -k option: Options. (line 203)
* comma separated values (CSV) data, --csv option: Options. (line 203)
-* comma separated values (CSV) data, records and fields: Comma Separated
Fields.
+* comma separated values (CSV) data, -k option: Options. (line 203)
+* comma separated values (CSV) data, generating CSV data: To CSV Function.
(line 6)
* Comma separated values (CSV) data, parsing with FPAT: Splitting By Content.
(line 23)
* Comma separated values (CSV) data, parsing with FPAT library: More CSV.
(line 52)
-* comma separated values (CSV) data, generating CSV data: To CSV Function.
+* comma separated values (CSV) data, records and fields: Comma Separated
Fields.
(line 6)
* command completion, in debugger: Readline Support. (line 6)
-* command line, formats: Running gawk. (line 12)
-* command line, option -f: Long. (line 12)
-* command line, invoking awk from: Command Line. (line 6)
-* command line, options: Options. (line 6)
-* command line, options, end of: Options. (line 58)
* command line, arguments: Other Arguments. (line 6)
-* command line, FS on, setting: Command Line Field Separator.
- (line 6)
-* command line, directories on: Command-line directories.
- (line 6)
-* command line, variables, assigning on: Assignment Options. (line 6)
* command line, arguments <1>: Auto-set. (line 15)
* command line, arguments <2>: Auto-set. (line 154)
* command line, arguments <3>: ARGC and ARGV. (line 6)
+* command line, directories on: Command-line directories.
+ (line 6)
+* command line, formats: Running gawk. (line 12)
+* command line, FS on, setting: Command Line Field Separator.
+ (line 6)
+* command line, invoking awk from: Command Line. (line 6)
+* command line, option -f: Long. (line 12)
+* command line, options: Options. (line 6)
+* command line, options, end of: Options. (line 58)
* command line, options, processing: Getopt Function. (line 6)
* command line, options, string extraction: String Extraction.
(line 6)
+* command line, variables, assigning on: Assignment Options. (line 6)
* commands debugger command: Debugger Execution Control.
(line 10)
* commands to execute at breakpoint: Debugger Execution Control.
(line 10)
* commenting: Comments. (line 6)
* commenting, backslash continuation and: Statements/Lines. (line 77)
-* common extensions, \x escape sequence: Escape Sequences. (line 61)
-* common extensions, \u escape sequence: Escape Sequences. (line 76)
-* common extensions, RS as a regexp: gawk split records. (line 6)
-* common extensions, single character fields: Single Character Fields.
- (line 6)
+* common extensions, ** operator: Arithmetic Ops. (line 30)
+* common extensions, **= operator: Assignment Ops. (line 138)
+* common extensions, /dev/stderr special file: Special FD. (line 48)
* common extensions, /dev/stdin special file: Special FD. (line 48)
* common extensions, /dev/stdout special file: Special FD. (line 48)
-* common extensions, /dev/stderr special file: Special FD. (line 48)
-* common extensions, ** operator: Arithmetic Ops. (line 30)
-* common extensions, **= operator: Assignment Ops. (line 139)
+* common extensions, \u escape sequence: Escape Sequences. (line 76)
+* common extensions, \x escape sequence: Escape Sequences. (line 61)
+* common extensions, BINMODE variable: PC Using. (line 18)
* common extensions, delete to delete entire arrays: Delete. (line 39)
+* common extensions, func keyword: Definition Syntax. (line 99)
* common extensions, length() applied to an array: String Functions.
(line 219)
-* common extensions, func keyword: Definition Syntax. (line 99)
-* common extensions, BINMODE variable: PC Using. (line 18)
+* common extensions, RS as a regexp: gawk split records. (line 6)
+* common extensions, single character fields: Single Character Fields.
+ (line 6)
* comp.lang.awk newsgroup: Usenet. (line 11)
* comparison expressions: Typing and Comparison.
(line 9)
-* comparison expressions, string vs. regexp: Comparison Operators.
- (line 80)
* comparison expressions, as patterns: Expression Patterns. (line 14)
-* compatibility mode (gawk), specifying: Options. (line 85)
+* comparison expressions, string vs. regexp: Comparison Operators.
+ (line 79)
+* compatibility mode (gawk), extensions: POSIX/GNU. (line 6)
* compatibility mode (gawk), file names: Special Caveats. (line 9)
-* compatibility mode (gawk), octal numbers: Nondecimal-numbers.
- (line 59)
* compatibility mode (gawk), hexadecimal numbers: Nondecimal-numbers.
(line 59)
-* compatibility mode (gawk), extensions: POSIX/GNU. (line 6)
-* compiled programs: Basic High Level. (line 14)
+* compatibility mode (gawk), octal numbers: Nondecimal-numbers.
+ (line 59)
+* compatibility mode (gawk), specifying: Options. (line 85)
+* compiled programs: Basic High Level. (line 16)
* compiled programs <1>: Glossary. (line 216)
-* compiling gawk, for MS-Windows: PC Compiling. (line 11)
* compiling gawk, for Cygwin: Cygwin. (line 6)
+* compiling gawk, for MS-Windows: PC Compiling. (line 11)
* compiling gawk, for OpenVMS: OpenVMS Compilation. (line 6)
-* compl: Bitwise Functions. (line 45)
-* complement, bitwise: Bitwise Functions. (line 26)
+* compl: Bitwise Functions. (line 44)
+* complement, bitwise: Bitwise Functions. (line 25)
* component name: Qualified Names. (line 6)
* component name, naming rules: Naming Rules. (line 6)
* compound statements, control statements and: Statements. (line 10)
@@ -37013,11 +36977,11 @@ Index
(line 46)
* configuration options, gawk: Additional Configuration Options.
(line 6)
-* constants, regexp: Regexp Usage. (line 57)
-* constants, types of: Constants. (line 6)
+* constants, nondecimal: Nondecimal Data. (line 6)
* constants, numeric: Scalar Constants. (line 6)
+* constants, regexp: Regexp Usage. (line 57)
* constants, string: Scalar Constants. (line 15)
-* constants, nondecimal: Nondecimal Data. (line 6)
+* constants, types of: Constants. (line 6)
* continue debugger command: Debugger Execution Control.
(line 33)
* continue program, in debugger: Debugger Execution Control.
@@ -37026,42 +36990,42 @@ Index
* control statements: Statements. (line 6)
* controlling array scanning order: Controlling Scanning.
(line 14)
-* converting, string to numbers: Strings And Numbers. (line 6)
-* converting, numbers to strings: Strings And Numbers. (line 6)
+* converting, dates to timestamps: Time Functions. (line 77)
* converting, integer array subscripts to strings: Numeric Array Subscripts.
(line 31)
-* converting, string to numbers <1>: String Functions. (line 420)
+* converting, numbers to strings: Strings And Numbers. (line 6)
+* converting, numbers to strings <1>: Bitwise Functions. (line 109)
* converting, string to lower case: String Functions. (line 553)
+* converting, string to numbers: Strings And Numbers. (line 6)
+* converting, string to numbers <1>: String Functions. (line 420)
+* converting, string to numbers <2>: Bitwise Functions. (line 109)
* converting, string to upper case: String Functions. (line 559)
-* converting, dates to timestamps: Time Functions. (line 77)
-* converting, string to numbers <2>: Bitwise Functions. (line 110)
-* converting, numbers to strings <1>: Bitwise Functions. (line 110)
* CONVFMT variable: Strings And Numbers. (line 29)
* CONVFMT variable <1>: User-modified. (line 30)
* CONVFMT variable, array subscripts and: Numeric Array Subscripts.
(line 6)
* cookie: Glossary. (line 255)
-* coprocesses, getline from: Getline/Coprocess. (line 6)
* coprocesses: Redirection. (line 96)
+* coprocesses <1>: Two-way I/O. (line 27)
* coprocesses, closing: Close Files And Pipes.
(line 6)
-* coprocesses <1>: Two-way I/O. (line 27)
+* coprocesses, getline from: Getline/Coprocess. (line 6)
* cos: Numeric Functions. (line 15)
* cosine: Numeric Functions. (line 15)
* counting words, lines, characters, and bytes: Wc Program. (line 6)
* cppawk: Other Versions. (line 190)
* csh utility: Statements/Lines. (line 45)
-* csh utility, POSIXLY_CORRECT environment variable: Options. (line 417)
* csh utility, |& operator, comparison with: Two-way I/O. (line 27)
-* CSV (comma separated values) data, -k option: Options. (line 203)
+* csh utility, POSIXLY_CORRECT environment variable: Options. (line 417)
* CSV (comma separated values) data, --csv option: Options. (line 203)
-* CSV (comma separated values) data, records and fields: Comma Separated
Fields.
+* CSV (comma separated values) data, -k option: Options. (line 203)
+* CSV (comma separated values) data, generating CSV data: To CSV Function.
(line 6)
-* CSV (comma separated values) data, parsing with FPAT: Splitting By Content.
- (line 23)
* CSV (comma separated values) data, parsing with CSVMODE library: More CSV.
(line 52)
-* CSV (comma separated values) data, generating CSV data: To CSV Function.
+* CSV (comma separated values) data, parsing with FPAT: Splitting By Content.
+ (line 23)
+* CSV (comma separated values) data, records and fields: Comma Separated
Fields.
(line 6)
* CSVMODE library for gawk: More CSV. (line 52)
* ctime() user-defined function: Function Example. (line 74)
@@ -37081,65 +37045,65 @@ Index
* cut.awk program: Cut Program. (line 49)
* d debugger command (alias for delete): Breakpoint Control. (line 64)
* dark corner: Conventions. (line 42)
+* dark corner <1>: Glossary. (line 266)
+* dark corner, "0" is actually true: Truth Values. (line 24)
+* dark corner, /= operator vs. /=.../ regexp constant: Assignment Ops.
+ (line 149)
+* dark corner, ^, in FS: Regexp Field Splitting.
+ (line 58)
* dark corner, ARGV variable, value of: Executable Scripts. (line 55)
+* dark corner, array subscripts: Uninitialized Subscripts.
+ (line 43)
* dark corner, backslash continuation on command line: Statements/Lines.
(line 92)
+* dark corner, break statement: Break Statement. (line 51)
+* dark corner, close() function: Close Return Value. (line 6)
* dark corner, command line, backslash continuation on: Statements/Lines.
(line 92)
-* dark corner, invoking awk: Command Line. (line 16)
+* dark corner, command-line arguments: Assignment Options. (line 43)
+* dark corner, continue statement: Continue Statement. (line 44)
+* dark corner, CONVFMT variable: Strings And Numbers. (line 39)
* dark corner, empty programs: Command Line. (line 20)
* dark corner, escape sequences: Other Arguments. (line 46)
* dark corner, escape sequences, for metacharacters: Escape Sequences.
(line 159)
-* dark corner, input files: awk split records. (line 104)
-* dark corner, strings, storing: gawk split records. (line 94)
-* dark corner, NF variable, decrementing: Changing Fields. (line 107)
-* dark corner, ^, in FS: Regexp Field Splitting.
- (line 58)
-* dark corner, FS as null string: Single Character Fields.
- (line 20)
+* dark corner, exit statement: Exit Statement. (line 30)
* dark corner, field separators: Full Line Fields. (line 22)
-* dark corner, multiline records: Multiple Line. (line 35)
* dark corner, FILENAME variable: Getline Notes. (line 19)
-* dark corner, OFMT variable: OFMT. (line 32)
+* dark corner, FILENAME variable <1>: Auto-set. (line 108)
+* dark corner, FNR/NR variables: Auto-set. (line 415)
* dark corner, format-control characters: Control Letters. (line 33)
* dark corner, format-control characters <1>: Control Letters.
(line 108)
-* dark corner, close() function: Close Return Value. (line 6)
-* dark corner, string continuation: Scalar Constants. (line 53)
-* dark corner, regexp constants: Standard Regexp Constants.
- (line 6)
-* dark corner, regexp constants, as arguments to user-defined functions:
Standard Regexp Constants.
- (line 43)
-* dark corner, command-line arguments: Assignment Options. (line 43)
-* dark corner, CONVFMT variable: Strings And Numbers. (line 39)
-* dark corner, localeâs decimal point character: Locale influences
conversions.
+* dark corner, FS as null string: Single Character Fields.
+ (line 20)
+* dark corner, input files: awk split records. (line 104)
+* dark corner, invoking awk: Command Line. (line 16)
+* dark corner, length() function: String Functions. (line 205)
+* dark corner, locale's decimal point character: Locale influences conversions.
(line 17)
-* dark corner, regexp constants, /= operator and: Assignment Ops.
- (line 150)
-* dark corner, /= operator vs. /=.../ regexp constant: Assignment Ops.
- (line 150)
-* dark corner, "0" is actually true: Truth Values. (line 24)
+* dark corner, multiline records: Multiple Line. (line 35)
+* dark corner, NF variable, decrementing: Changing Fields. (line 107)
+* dark corner, OFMT variable: OFMT. (line 32)
+* dark corner, parameter name restrictions: Definition Syntax.
+ (line 44)
* dark corner, range patterns, line continuation and: Ranges. (line 64)
-* dark corner, break statement: Break Statement. (line 51)
-* dark corner, continue statement: Continue Statement. (line 44)
-* dark corner, exit statement: Exit Statement. (line 30)
-* dark corner, value of ARGV[0]: Auto-set. (line 39)
-* dark corner, FILENAME variable <1>: Auto-set. (line 108)
-* dark corner, FNR/NR variables: Auto-set. (line 416)
-* dark corner, array subscripts: Uninitialized Subscripts.
- (line 43)
* dark corner, regexp as second argument to index(): String Functions.
(line 183)
-* dark corner, length() function: String Functions. (line 205)
+* dark corner, regexp constants: Standard Regexp Constants.
+ (line 6)
+* dark corner, regexp constants, /= operator and: Assignment Ops.
+ (line 148)
+* dark corner, regexp constants, as arguments to user-defined functions:
Standard Regexp Constants.
+ (line 43)
* dark corner, split() function: String Functions. (line 391)
-* dark corner, parameter name restrictions: Definition Syntax.
- (line 44)
-* dark corner <1>: Glossary. (line 266)
+* dark corner, string continuation: Scalar Constants. (line 53)
+* dark corner, strings, storing: gawk split records. (line 92)
+* dark corner, value of ARGV[0]: Auto-set. (line 39)
+* data-driven languages: Basic High Level. (line 87)
* data, fixed-width: Constant Size. (line 6)
-* data-driven languages: Basic High Level. (line 76)
-* database, users, reading: Passwd Functions. (line 6)
* database, group, reading: Group Functions. (line 6)
+* database, users, reading: Passwd Functions. (line 6)
* date utility, GNU: Time Functions. (line 17)
* date utility, POSIX: Time Functions. (line 254)
* dates, converting to timestamps: Time Functions. (line 77)
@@ -37158,136 +37122,136 @@ Index
(line 33)
* deadlocks: Two-way I/O. (line 53)
* debugger, capabilities: Debugging Concepts. (line 16)
-* debugger, concepts: Debugging Terms. (line 6)
-* debugger, how to start: Debugger Invocation. (line 6)
-* debugger, prompt: Debugger Invocation. (line 26)
-* debugger, setting a breakpoint: Finding The Bug. (line 32)
-* debugger, commands, breakpoint: Finding The Bug. (line 32)
-* debugger, commands, break: Finding The Bug. (line 32)
+* debugger, command completion: Readline Support. (line 6)
* debugger, commands, b (break): Finding The Bug. (line 32)
-* debugger, running the program: Finding The Bug. (line 39)
-* debugger, commands, run: Finding The Bug. (line 39)
-* debugger, stack frames, showing: Finding The Bug. (line 52)
-* debugger, commands, bt (backtrace): Finding The Bug. (line 52)
-* debugger, commands, backtrace: Finding The Bug. (line 52)
-* debugger, commands, print: Finding The Bug. (line 68)
-* debugger, commands, p (print): Finding The Bug. (line 68)
-* debugger, commands, n (next): Finding The Bug. (line 105)
-* debugger, commands, next: Finding The Bug. (line 105)
-* debugger, printing single array elements: Finding The Bug. (line 140)
-* debugger, printing all array elements: Finding The Bug. (line 154)
-* debugger, repeating commands: List of Debugger Commands.
- (line 21)
* debugger, commands, b (break) <1>: Breakpoint Control. (line 11)
+* debugger, commands, backtrace: Finding The Bug. (line 52)
+* debugger, commands, backtrace <1>: Execution Stack. (line 13)
+* debugger, commands, break: Finding The Bug. (line 32)
* debugger, commands, break <1>: Breakpoint Control. (line 11)
+* debugger, commands, breakpoint: Finding The Bug. (line 32)
+* debugger, commands, bt (backtrace): Finding The Bug. (line 52)
+* debugger, commands, bt (backtrace) <1>: Execution Stack. (line 13)
+* debugger, commands, c (continue): Debugger Execution Control.
+ (line 33)
* debugger, commands, clear: Breakpoint Control. (line 36)
+* debugger, commands, commands: Debugger Execution Control.
+ (line 10)
* debugger, commands, condition: Breakpoint Control. (line 54)
+* debugger, commands, continue: Debugger Execution Control.
+ (line 33)
* debugger, commands, d (delete): Breakpoint Control. (line 64)
* debugger, commands, delete: Breakpoint Control. (line 64)
* debugger, commands, disable: Breakpoint Control. (line 69)
+* debugger, commands, display: Viewing And Changing Data.
+ (line 8)
+* debugger, commands, down: Execution Stack. (line 23)
+* debugger, commands, dump: Miscellaneous Debugger Commands.
+ (line 9)
* debugger, commands, e (enable): Breakpoint Control. (line 73)
* debugger, commands, enable: Breakpoint Control. (line 73)
-* debugger, commands, ignore: Breakpoint Control. (line 87)
-* debugger, commands, t (tbreak): Breakpoint Control. (line 90)
-* debugger, commands, tbreak: Breakpoint Control. (line 90)
-* debugger, commands, commands: Debugger Execution Control.
- (line 10)
-* debugger, commands, silent: Debugger Execution Control.
- (line 10)
* debugger, commands, end: Debugger Execution Control.
(line 10)
-* debugger, commands, c (continue): Debugger Execution Control.
- (line 33)
-* debugger, commands, continue: Debugger Execution Control.
- (line 33)
+* debugger, commands, eval: Viewing And Changing Data.
+ (line 23)
+* debugger, commands, f (frame): Execution Stack. (line 27)
* debugger, commands, finish: Debugger Execution Control.
(line 39)
+* debugger, commands, frame: Execution Stack. (line 27)
+* debugger, commands, h (help): Miscellaneous Debugger Commands.
+ (line 67)
+* debugger, commands, help: Miscellaneous Debugger Commands.
+ (line 67)
+* debugger, commands, i (info): Debugger Info. (line 13)
+* debugger, commands, ignore: Breakpoint Control. (line 87)
+* debugger, commands, info: Debugger Info. (line 13)
+* debugger, commands, l (list): Miscellaneous Debugger Commands.
+ (line 73)
+* debugger, commands, list: Miscellaneous Debugger Commands.
+ (line 73)
+* debugger, commands, n (next): Finding The Bug. (line 105)
* debugger, commands, n (next) <1>: Debugger Execution Control.
(line 43)
+* debugger, commands, next: Finding The Bug. (line 105)
* debugger, commands, next <1>: Debugger Execution Control.
(line 43)
-* debugger, commands, ni (nexti): Debugger Execution Control.
- (line 49)
* debugger, commands, nexti: Debugger Execution Control.
(line 49)
-* debugger, commands, return: Debugger Execution Control.
- (line 54)
+* debugger, commands, ni (nexti): Debugger Execution Control.
+ (line 49)
+* debugger, commands, o (option): Debugger Info. (line 57)
+* debugger, commands, option: Debugger Info. (line 57)
+* debugger, commands, p (print): Finding The Bug. (line 68)
+* debugger, commands, p (print) <1>: Viewing And Changing Data.
+ (line 39)
+* debugger, commands, print: Finding The Bug. (line 68)
+* debugger, commands, print <1>: Viewing And Changing Data.
+ (line 39)
+* debugger, commands, printf: Viewing And Changing Data.
+ (line 57)
+* debugger, commands, q (quit): Miscellaneous Debugger Commands.
+ (line 100)
+* debugger, commands, quit: Miscellaneous Debugger Commands.
+ (line 100)
* debugger, commands, r (run): Debugger Execution Control.
(line 62)
+* debugger, commands, return: Debugger Execution Control.
+ (line 54)
+* debugger, commands, run: Finding The Bug. (line 39)
* debugger, commands, run <1>: Debugger Execution Control.
(line 62)
* debugger, commands, s (step): Debugger Execution Control.
(line 68)
-* debugger, commands, step: Debugger Execution Control.
- (line 68)
+* debugger, commands, set: Viewing And Changing Data.
+ (line 62)
* debugger, commands, si (stepi): Debugger Execution Control.
(line 75)
+* debugger, commands, silent: Debugger Execution Control.
+ (line 10)
+* debugger, commands, step: Debugger Execution Control.
+ (line 68)
* debugger, commands, stepi: Debugger Execution Control.
(line 75)
+* debugger, commands, t (tbreak): Breakpoint Control. (line 90)
+* debugger, commands, tbreak: Breakpoint Control. (line 90)
+* debugger, commands, trace: Miscellaneous Debugger Commands.
+ (line 108)
* debugger, commands, u (until): Debugger Execution Control.
(line 82)
+* debugger, commands, undisplay: Viewing And Changing Data.
+ (line 83)
* debugger, commands, until: Debugger Execution Control.
(line 82)
-* debugger, commands, display: Viewing And Changing Data.
- (line 8)
-* debugger, commands, eval: Viewing And Changing Data.
- (line 23)
-* debugger, commands, p (print) <1>: Viewing And Changing Data.
- (line 39)
-* debugger, commands, print <1>: Viewing And Changing Data.
- (line 39)
-* debugger, commands, printf: Viewing And Changing Data.
- (line 57)
-* debugger, commands, set: Viewing And Changing Data.
- (line 62)
+* debugger, commands, unwatch: Viewing And Changing Data.
+ (line 87)
+* debugger, commands, up: Execution Stack. (line 36)
* debugger, commands, w (watch): Viewing And Changing Data.
(line 70)
* debugger, commands, watch: Viewing And Changing Data.
(line 70)
-* debugger, commands, undisplay: Viewing And Changing Data.
- (line 83)
-* debugger, commands, unwatch: Viewing And Changing Data.
- (line 87)
-* debugger, commands, bt (backtrace) <1>: Execution Stack. (line 13)
-* debugger, commands, backtrace <1>: Execution Stack. (line 13)
* debugger, commands, where (backtrace): Execution Stack. (line 13)
-* debugger, commands, down: Execution Stack. (line 23)
-* debugger, commands, f (frame): Execution Stack. (line 27)
-* debugger, commands, frame: Execution Stack. (line 27)
-* debugger, commands, up: Execution Stack. (line 36)
-* debugger, commands, i (info): Debugger Info. (line 13)
-* debugger, commands, info: Debugger Info. (line 13)
-* debugger, commands, o (option): Debugger Info. (line 57)
-* debugger, commands, option: Debugger Info. (line 57)
-* debugger, options: Debugger Info. (line 57)
-* debugger, history size: Debugger Info. (line 65)
+* debugger, concepts: Debugging Terms. (line 6)
* debugger, default list amount: Debugger Info. (line 69)
-* debugger, prompt <1>: Debugger Info. (line 78)
+* debugger, history expansion: Readline Support. (line 6)
* debugger, history file: Debugger Info. (line 81)
+* debugger, history size: Debugger Info. (line 65)
+* debugger, how to start: Debugger Invocation. (line 6)
* debugger, instruction tracing: Debugger Info. (line 90)
-* debugger, save commands to a file: Debugger Info. (line 92)
-* debugger, read commands from a file: Debugger Info. (line 97)
-* debugger, commands, dump: Miscellaneous Debugger Commands.
- (line 9)
-* debugger, commands, h (help): Miscellaneous Debugger Commands.
- (line 67)
-* debugger, commands, help: Miscellaneous Debugger Commands.
- (line 67)
-* debugger, commands, l (list): Miscellaneous Debugger Commands.
- (line 73)
-* debugger, commands, list: Miscellaneous Debugger Commands.
- (line 73)
-* debugger, commands, q (quit): Miscellaneous Debugger Commands.
- (line 100)
-* debugger, commands, quit: Miscellaneous Debugger Commands.
- (line 100)
-* debugger, commands, trace: Miscellaneous Debugger Commands.
- (line 108)
-* debugger, command completion: Readline Support. (line 6)
-* debugger, history expansion: Readline Support. (line 6)
-* debugger, limitations: Limitations. (line 6)
* debugger, interaction with namespaces: Namespace And Features.
(line 17)
+* debugger, limitations: Limitations. (line 6)
+* debugger, options: Debugger Info. (line 57)
+* debugger, printing all array elements: Finding The Bug. (line 154)
+* debugger, printing single array elements: Finding The Bug. (line 140)
+* debugger, prompt: Debugger Invocation. (line 26)
+* debugger, prompt <1>: Debugger Info. (line 78)
+* debugger, read commands from a file: Debugger Info. (line 97)
+* debugger, repeating commands: List of Debugger Commands.
+ (line 21)
+* debugger, running the program: Finding The Bug. (line 39)
+* debugger, save commands to a file: Debugger Info. (line 92)
+* debugger, setting a breakpoint: Finding The Bug. (line 32)
+* debugger, stack frames, showing: Finding The Bug. (line 52)
* debugging, awk programs: Debugger. (line 6)
* debugging, example session: Sample Debugging Session.
(line 6)
@@ -37308,94 +37272,94 @@ Index
* deleting, entire arrays: Delete. (line 39)
* Demaille, Akim: Acknowledgments. (line 60)
* describe call stack frame, in debugger: Debugger Info. (line 27)
-* differences in awk and gawk, AWKPATH environment variable: AWKPATH Variable.
- (line 6)
+* differences in awk and gawk, ARGC/ARGV variables: ARGC and ARGV.
+ (line 89)
+* differences in awk and gawk, ARGIND variable: Auto-set. (line 44)
+* differences in awk and gawk, array elements, deleting: Delete.
+ (line 39)
* differences in awk and gawk, AWKLIBPATH environment variable: AWKLIBPATH
Variable.
(line 6)
-* differences in awk and gawk, regular expressions: Case-sensitivity.
- (line 26)
-* differences in awk and gawk, record separators: awk split records.
- (line 118)
-* differences in awk and gawk, RS/RT variables: awk split records.
- (line 118)
-* differences in awk and gawk, RS/RT variables <1>: gawk split records.
- (line 66)
-* differences in awk and gawk, strings, storing: gawk split records.
- (line 88)
-* differences in awk and gawk, single-character fields: Single Character
Fields.
- (line 6)
-* differences in awk and gawk, RS/RT variables <2>: Multiple Line.
- (line 138)
-* differences in awk and gawk, getline command: Getline. (line 19)
-* differences in awk and gawk, input/output operators: Getline/Coprocess.
- (line 6)
-* differences in awk and gawk, implementation limitations: Getline Notes.
- (line 14)
-* differences in awk and gawk, read timeouts: Read Timeout. (line 6)
-* differences in awk and gawk, retrying input: Retrying Input.
- (line 6)
-* differences in awk and gawk, command-line directories: Command-line
directories.
- (line 6)
-* differences in awk and gawk, print/printf statements: Format Modifiers.
- (line 13)
-* differences in awk and gawk, input/output operators <1>: Redirection.
- (line 96)
-* differences in awk and gawk, implementation limitations <1>: Redirection.
- (line 129)
-* differences in awk and gawk, error messages: Special FD. (line 19)
-* differences in awk and gawk, close() function: Close Files And Pipes.
- (line 85)
-* differences in awk and gawk, close() function <1>: Close Return Value.
+* differences in awk and gawk, AWKPATH environment variable: AWKPATH Variable.
(line 6)
-* differences in awk and gawk, strings: Scalar Constants. (line 20)
-* differences in awk and gawk, strings <1>: Scalar Constants. (line 53)
-* differences in awk and gawk, regexp constants: Standard Regexp Constants.
- (line 43)
-* differences in awk and gawk, trunc-mod operation: Arithmetic Ops.
- (line 66)
-* differences in awk and gawk, line continuations: Conditional Exp.
- (line 34)
* differences in awk and gawk, BEGIN/END patterns: I/O And BEGIN/END.
(line 15)
* differences in awk and gawk, BEGINFILE/ENDFILE patterns: BEGINFILE/ENDFILE.
(line 6)
* differences in awk and gawk, BINMODE variable: User-modified.
(line 15)
+* differences in awk and gawk, BINMODE variable <1>: PC Using.
+ (line 18)
+* differences in awk and gawk, close() function: Close Files And Pipes.
+ (line 85)
+* differences in awk and gawk, close() function <1>: Close Return Value.
+ (line 6)
+* differences in awk and gawk, command-line directories: Command-line
directories.
+ (line 6)
+* differences in awk and gawk, ERRNO variable: Auto-set. (line 87)
+* differences in awk and gawk, error messages: Special FD. (line 19)
* differences in awk and gawk, FIELDWIDTHS variable: User-modified.
(line 37)
* differences in awk and gawk, FPAT variable: User-modified. (line 46)
-* differences in awk and gawk, IGNORECASE variable: User-modified.
- (line 79)
-* differences in awk and gawk, LINT variable: User-modified. (line 90)
-* differences in awk and gawk, TEXTDOMAIN variable: User-modified.
- (line 154)
-* differences in awk and gawk, ARGIND variable: Auto-set. (line 44)
-* differences in awk and gawk, ERRNO variable: Auto-set. (line 87)
* differences in awk and gawk, FUNCTAB variable: Auto-set. (line 134)
-* differences in awk and gawk, PROCINFO array: Auto-set. (line 148)
-* differences in awk and gawk, RS/RT variables <3>: Auto-set. (line 355)
-* differences in awk and gawk, SYMTAB variable: Auto-set. (line 359)
-* differences in awk and gawk, ARGC/ARGV variables: ARGC and ARGV.
- (line 89)
-* differences in awk and gawk, array elements, deleting: Delete.
- (line 39)
* differences in awk and gawk, function arguments: Calling Built-in.
(line 16)
+* differences in awk and gawk, getline command: Getline. (line 19)
+* differences in awk and gawk, IGNORECASE variable: User-modified.
+ (line 79)
+* differences in awk and gawk, implementation limitations: Getline Notes.
+ (line 14)
+* differences in awk and gawk, implementation limitations <1>: Redirection.
+ (line 129)
+* differences in awk and gawk, indirect function calls: Indirect Calls.
+ (line 6)
+* differences in awk and gawk, input/output operators: Getline/Coprocess.
+ (line 6)
+* differences in awk and gawk, input/output operators <1>: Redirection.
+ (line 96)
* differences in awk and gawk, length() function: String Functions.
(line 219)
+* differences in awk and gawk, line continuations: Conditional Exp.
+ (line 34)
+* differences in awk and gawk, LINT variable: User-modified. (line 90)
* differences in awk and gawk, match() function: String Functions.
(line 281)
+* differences in awk and gawk, print/printf statements: Format Modifiers.
+ (line 13)
+* differences in awk and gawk, PROCINFO array: Auto-set. (line 148)
+* differences in awk and gawk, read timeouts: Read Timeout. (line 6)
+* differences in awk and gawk, record separators: awk split records.
+ (line 118)
+* differences in awk and gawk, regexp constants: Standard Regexp Constants.
+ (line 43)
+* differences in awk and gawk, regular expressions: Case-sensitivity.
+ (line 26)
+* differences in awk and gawk, retrying input: Retrying Input.
+ (line 6)
+* differences in awk and gawk, RS/RT variables: awk split records.
+ (line 118)
+* differences in awk and gawk, RS/RT variables <1>: gawk split records.
+ (line 65)
+* differences in awk and gawk, RS/RT variables <2>: Multiple Line.
+ (line 138)
+* differences in awk and gawk, RS/RT variables <3>: Auto-set. (line 355)
+* differences in awk and gawk, single-character fields: Single Character
Fields.
+ (line 6)
* differences in awk and gawk, split() function: String Functions.
(line 376)
-* differences in awk and gawk, indirect function calls: Indirect Calls.
+* differences in awk and gawk, strings: Scalar Constants. (line 20)
+* differences in awk and gawk, strings <1>: Scalar Constants. (line 53)
+* differences in awk and gawk, strings, storing: gawk split records.
+ (line 86)
+* differences in awk and gawk, SYMTAB variable: Auto-set. (line 359)
+* differences in awk and gawk, TEXTDOMAIN variable: User-modified.
+ (line 154)
+* differences in awk and gawk, trunc-mod operation: Arithmetic Ops.
+ (line 66)
+* directories, command-line: Command-line directories.
(line 6)
-* differences in awk and gawk, BINMODE variable <1>: PC Using.
- (line 18)
-* directories, searching, for source files: AWKPATH Variable. (line 6)
* directories, searching, for loadable extensions: AWKLIBPATH Variable.
(line 6)
-* directories, command-line: Command-line directories.
- (line 6)
+* directories, searching, for source files: AWKPATH Variable. (line 6)
* directories, searching, for source files <1>: Programs Exercises.
(line 70)
* disable breakpoint: Breakpoint Control. (line 69)
@@ -37404,25 +37368,25 @@ Index
(line 8)
* display debugger options: Debugger Info. (line 57)
* division: Arithmetic Ops. (line 44)
-* do-while statement, use of regexps in: Regexp Usage. (line 19)
* do-while statement: Do Statement. (line 6)
-* documentation, online: Manual History. (line 11)
-* documentation, of awk programs: Library Names. (line 6)
+* do-while statement, use of regexps in: Regexp Usage. (line 19)
+* documentation, building, HTML: Building the Documentation.
+ (line 28)
* documentation, building, Info files: Building the Documentation.
(line 6)
* documentation, building, PDF: Building the Documentation.
(line 12)
-* documentation, building, HTML: Building the Documentation.
- (line 28)
+* documentation, of awk programs: Library Names. (line 6)
+* documentation, online: Manual History. (line 11)
* documents, searching: Dupword Program. (line 6)
-* dollar sign ($), regexp operator: Regexp Operator Details.
- (line 31)
* dollar sign ($), $ field operator: Fields. (line 19)
+* dollar sign ($), $ field operator <1>: Precedence. (line 42)
* dollar sign ($), incrementing fields and arrays: Increment Ops.
(line 30)
-* dollar sign ($), $ field operator <1>: Precedence. (line 42)
-* double quote ("), in shell commands: Quoting. (line 54)
+* dollar sign ($), regexp operator: Regexp Operator Details.
+ (line 31)
* double quote ("), in regexp constants: Computed Regexps. (line 30)
+* double quote ("), in shell commands: Quoting. (line 54)
* double-precision: Computer Arithmetic. (line 61)
* down debugger command: Execution Stack. (line 23)
* Drepper, Ulrich: Acknowledgments. (line 52)
@@ -37447,41 +37411,41 @@ Index
* elements in arrays: Reference to Elements.
(line 6)
* elements in arrays, assigning values: Assigning Elements. (line 6)
-* elements in arrays, scanning: Scanning an Array. (line 6)
+* elements in arrays, deleting: Delete. (line 6)
* elements in arrays, order of access by in operator: Scanning an Array.
(line 48)
-* elements in arrays, deleting: Delete. (line 6)
+* elements in arrays, scanning: Scanning an Array. (line 6)
* email address for bug reports, <bug-gawk@gnu.org>: Bug address.
(line 52)
* empty array elements: Reference to Elements.
(line 18)
* empty pattern: Empty. (line 6)
* empty regexps: Regexp Operator Details.
- (line 151)
+ (line 150)
* EMRED: TCP/IP Networking. (line 6)
* enable breakpoint: Breakpoint Control. (line 73)
* enable debugger command: Breakpoint Control. (line 73)
* end debugger command: Debugger Execution Control.
(line 10)
-* END pattern, Boolean patterns and: Expression Patterns. (line 70)
* END pattern: BEGIN/END. (line 6)
* END pattern <1>: Using BEGIN/END. (line 6)
-* END pattern, operators and: Using BEGIN/END. (line 17)
-* END pattern, print statement and: I/O And BEGIN/END. (line 15)
+* END pattern, @namespace directive and: Changing The Namespace.
+ (line 37)
+* END pattern, assert() user-defined function and: Assert Function.
+ (line 75)
+* END pattern, Boolean patterns and: Expression Patterns. (line 70)
+* END pattern, exit statement and: Exit Statement. (line 12)
* END pattern, next/nextfile statements and: I/O And BEGIN/END.
(line 36)
* END pattern, next/nextfile statements and <1>: Next Statement.
(line 44)
-* END pattern, exit statement and: Exit Statement. (line 12)
-* END pattern, assert() user-defined function and: Assert Function.
- (line 75)
+* END pattern, operators and: Using BEGIN/END. (line 17)
+* END pattern, print statement and: I/O And BEGIN/END. (line 15)
* END pattern, profiling and: Profiling. (line 62)
-* END pattern, @namespace directive and: Changing The Namespace.
- (line 37)
-* ENDFILE pattern, Boolean patterns and: Expression Patterns. (line 70)
* ENDFILE pattern: BEGINFILE/ENDFILE. (line 6)
* ENDFILE pattern, @namespace directive and: Changing The Namespace.
(line 37)
+* ENDFILE pattern, Boolean patterns and: Expression Patterns. (line 70)
* endfile() user-defined function: Filetrans Function. (line 62)
* endgrent() function (C library): Group Functions. (line 211)
* endgrent() user-defined function: Group Functions. (line 214)
@@ -37489,92 +37453,92 @@ Index
* endpwent() user-defined function: Passwd Functions. (line 210)
* English, Steve: Advanced Features. (line 6)
* ENVIRON array: Auto-set. (line 59)
+* environment variables, AWK_HASH: Other Environment Variables.
+ (line 50)
+* environment variables, AWKBUFSIZE: Other Environment Variables.
+ (line 41)
* environment variables, AWKLIBPATH: Options. (line 209)
-* environment variables, POSIXLY_CORRECT: Options. (line 402)
-* environment variables, used by gawk: Environment Variables.
- (line 6)
-* environment variables, AWKPATH: AWKPATH Variable. (line 6)
* environment variables, AWKLIBPATH <1>: AWKLIBPATH Variable. (line 6)
+* environment variables, AWKLIBPATH <2>: Loading Shared Libraries.
+ (line 8)
+* environment variables, AWKLIBPATH <3>: Invoking Summary. (line 49)
+* environment variables, AWKLIBPATH <4>: Creating Arrays. (line 129)
+* environment variables, AWKLIBPATH <5>: Using Internal File Ops.
+ (line 44)
+* environment variables, AWKLIBPATH <6>: POSIX/GNU. (line 108)
+* environment variables, AWKLIBPATH <7>: Distribution contents.
+ (line 192)
+* environment variables, AWKLIBPATH <8>: Shell Startup Files. (line 6)
+* environment variables, AWKPATH: AWKPATH Variable. (line 6)
+* environment variables, AWKPATH <1>: Include Files. (line 8)
+* environment variables, AWKPATH <2>: Invoking Summary. (line 49)
+* environment variables, AWKPATH <3>: Igawk Program. (line 12)
+* environment variables, AWKPATH <4>: Igawk Program. (line 211)
+* environment variables, AWKPATH <5>: Debugger Invocation. (line 16)
+* environment variables, AWKPATH <6>: POSIX/GNU. (line 105)
+* environment variables, AWKPATH <7>: Feature History. (line 11)
+* environment variables, AWKPATH <8>: Distribution contents.
+ (line 192)
+* environment variables, AWKPATH <9>: Shell Startup Files. (line 6)
+* environment variables, AWKPATH <10>: PC Using. (line 12)
+* environment variables, AWKPATH <11>: OpenVMS Running. (line 50)
+* environment variables, AWKREADFUNC: Other Environment Variables.
+ (line 57)
+* environment variables, GAWK_LOCALE_DIR: Other Environment Variables.
+ (line 70)
+* environment variables, GAWK_LOCALE_DIR <1>: Explaining gettext.
+ (line 132)
* environment variables, GAWK_MSEC_SLEEP: Other Environment Variables.
(line 10)
+* environment variables, GAWK_MSG_SRC: Other Environment Variables.
+ (line 63)
+* environment variables, GAWK_NO_DFA: Other Environment Variables.
+ (line 75)
* environment variables, GAWK_PERSIST_FILE: Other Environment Variables.
(line 15)
+* environment variables, GAWK_PERSIST_FILE <1>: Persistent Memory.
+ (line 50)
* environment variables, GAWK_READ_TIMEOUT: Other Environment Variables.
(line 19)
+* environment variables, GAWK_READ_TIMEOUT <1>: Read Timeout. (line 71)
* environment variables, GAWK_SOCK_RETRIES: Other Environment Variables.
(line 23)
-* environment variables, PMA_VERBOSITY: Other Environment Variables.
- (line 29)
-* environment variables, POSIXLY_CORRECT <1>: Other Environment Variables.
- (line 33)
-* environment variables, AWKBUFSIZE: Other Environment Variables.
- (line 41)
-* environment variables, AWK_HASH: Other Environment Variables.
- (line 50)
-* environment variables, AWKREADFUNC: Other Environment Variables.
- (line 57)
-* environment variables, GAWK_MSG_SRC: Other Environment Variables.
- (line 63)
-* environment variables, GAWK_LOCALE_DIR: Other Environment Variables.
- (line 70)
-* environment variables, GAWK_NO_DFA: Other Environment Variables.
- (line 75)
+* environment variables, GAWK_SOCK_RETRIES <1>: Nonfatal. (line 53)
* environment variables, GAWK_STACKSIZE: Other Environment Variables.
(line 83)
+* environment variables, in ENVIRON array: Auto-set. (line 59)
* environment variables, INT_CHAIN_MAX: Other Environment Variables.
(line 87)
-* environment variables, STR_CHAIN_MAX: Other Environment Variables.
- (line 91)
-* environment variables, TIDYMEM: Other Environment Variables.
- (line 95)
-* environment variables, AWKPATH <1>: Include Files. (line 8)
-* environment variables, AWKLIBPATH <2>: Loading Shared Libraries.
- (line 8)
-* environment variables, AWKPATH <2>: Invoking Summary. (line 49)
-* environment variables, AWKLIBPATH <3>: Invoking Summary. (line 49)
-* environment variables, POSIXLY_CORRECT <2>: Invoking Summary.
- (line 49)
-* environment variables, GAWK_READ_TIMEOUT <1>: Read Timeout. (line 71)
-* environment variables, GAWK_SOCK_RETRIES <1>: Nonfatal. (line 53)
-* environment variables, POSIXLY_CORRECT <3>: Locale influences conversions.
- (line 41)
-* environment variables, in ENVIRON array: Auto-set. (line 59)
-* environment variables, TZ: Auto-set. (line 76)
-* environment variables, LC_ALL: Split Program. (line 39)
-* environment variables, AWKPATH <3>: Igawk Program. (line 12)
-* environment variables, AWKPATH <4>: Igawk Program. (line 211)
-* environment variables, REALLY_USE_PERSIST_MALLOC: Persistent Memory.
- (line 29)
-* environment variables, GAWK_PERSIST_FILE <1>: Persistent Memory.
- (line 50)
-* environment variables, PMA_VERBOSITY <1>: Persistent Memory.
- (line 94)
+* environment variables, LANG: I18N Example. (line 68)
* environment variables, LANGUAGE: Explaining gettext. (line 120)
-* environment variables, GAWK_LOCALE_DIR <1>: Explaining gettext.
- (line 132)
* environment variables, LANGUAGE <1>: I18N Example. (line 68)
+* environment variables, LC_ALL: Split Program. (line 39)
* environment variables, LC_ALL <1>: I18N Example. (line 68)
-* environment variables, LANG: I18N Example. (line 68)
+* environment variables, LC_ALL <2>: Bug address. (line 18)
* environment variables, LC_MESSAGES: I18N Example. (line 68)
-* environment variables, AWKPATH <5>: Debugger Invocation. (line 16)
-* environment variables, AWKLIBPATH <4>: Creating Arrays. (line 129)
-* environment variables, AWKLIBPATH <5>: Using Internal File Ops.
- (line 44)
-* environment variables, AWKPATH <6>: POSIX/GNU. (line 105)
-* environment variables, AWKLIBPATH <6>: POSIX/GNU. (line 108)
-* environment variables, AWKPATH <7>: Feature History. (line 11)
-* environment variables, AWKPATH <8>: Distribution contents.
- (line 192)
-* environment variables, AWKLIBPATH <7>: Distribution contents.
- (line 192)
-* environment variables, AWKPATH <9>: Shell Startup Files. (line 6)
-* environment variables, AWKLIBPATH <8>: Shell Startup Files. (line 6)
* environment variables, Path: PC Binary Installation.
(line 6)
-* environment variables, AWKPATH <10>: PC Using. (line 12)
-* environment variables, AWKPATH <11>: OpenVMS Running. (line 50)
-* environment variables, LC_ALL <2>: Bug address. (line 18)
* environment variables, PATH: Derived Files. (line 94)
+* environment variables, PMA_VERBOSITY: Other Environment Variables.
+ (line 29)
+* environment variables, PMA_VERBOSITY <1>: Persistent Memory.
+ (line 94)
+* environment variables, POSIXLY_CORRECT: Options. (line 402)
+* environment variables, POSIXLY_CORRECT <1>: Other Environment Variables.
+ (line 33)
+* environment variables, POSIXLY_CORRECT <2>: Invoking Summary.
+ (line 49)
+* environment variables, POSIXLY_CORRECT <3>: Locale influences conversions.
+ (line 41)
+* environment variables, REALLY_USE_PERSIST_MALLOC: Persistent Memory.
+ (line 29)
+* environment variables, STR_CHAIN_MAX: Other Environment Variables.
+ (line 91)
+* environment variables, TIDYMEM: Other Environment Variables.
+ (line 95)
+* environment variables, TZ: Auto-set. (line 76)
+* environment variables, used by gawk: Environment Variables.
+ (line 6)
* environment, definition of: Glossary. (line 304)
* epoch, definition of: Glossary. (line 310)
* equals sign (=), = operator: Assignment Ops. (line 6)
@@ -37582,11 +37546,11 @@ Index
(line 11)
* equals sign (=), == operator <1>: Precedence. (line 64)
* EREs (Extended Regular Expressions): Bracket Expressions. (line 34)
-* ERRNO variable, with getline command: Getline. (line 19)
-* ERRNO variable, with close() function: Close Return Value. (line 14)
-* ERRNO variable, with BEGINFILE pattern: BEGINFILE/ENDFILE. (line 32)
* ERRNO variable: Auto-set. (line 87)
* ERRNO variable <1>: TCP/IP Networking. (line 54)
+* ERRNO variable, with BEGINFILE pattern: BEGINFILE/ENDFILE. (line 32)
+* ERRNO variable, with close() function: Close Return Value. (line 14)
+* ERRNO variable, with getline command: Getline. (line 19)
* error handling: Special FD. (line 19)
* error handling, ERRNO variable and: Auto-set. (line 87)
* error output: Special FD. (line 6)
@@ -37597,29 +37561,29 @@ Index
(line 23)
* evaluate expressions, in debugger: Viewing And Changing Data.
(line 23)
+* evaluation order: Increment Ops. (line 59)
* evaluation order, concatenation: Concatenation. (line 41)
-* evaluation order: Increment Ops. (line 60)
* evaluation order, functions: Calling Built-in. (line 30)
* examining fields: Fields. (line 6)
* example debugging session: Sample Debugging Session.
(line 6)
+* exclamation point (!), ! operator: Boolean Ops. (line 69)
+* exclamation point (!), ! operator <1>: Precedence. (line 51)
+* exclamation point (!), ! operator <2>: Egrep Program. (line 204)
+* exclamation point (!), != operator: Comparison Operators.
+ (line 11)
+* exclamation point (!), != operator <1>: Precedence. (line 64)
* exclamation point (!), !~ operator: Regexp Usage. (line 19)
* exclamation point (!), !~ operator <1>: Computed Regexps. (line 6)
* exclamation point (!), !~ operator <2>: Case-sensitivity. (line 26)
* exclamation point (!), !~ operator <3>: Regexp Constants. (line 6)
-* exclamation point (!), != operator: Comparison Operators.
- (line 11)
* exclamation point (!), !~ operator <4>: Comparison Operators.
(line 11)
* exclamation point (!), !~ operator <5>: Comparison Operators.
- (line 99)
-* exclamation point (!), ! operator: Boolean Ops. (line 69)
-* exclamation point (!), ! operator <1>: Precedence. (line 51)
-* exclamation point (!), != operator <1>: Precedence. (line 64)
+ (line 98)
* exclamation point (!), !~ operator <6>: Precedence. (line 79)
* exclamation point (!), !~ operator <7>: Expression Patterns.
(line 24)
-* exclamation point (!), ! operator <2>: Egrep Program. (line 204)
* exit debugger command: Miscellaneous Debugger Commands.
(line 64)
* exit statement: Exit Statement. (line 6)
@@ -37634,56 +37598,56 @@ Index
* Expat XML parser library: gawkextlib. (line 40)
* exponent: Numeric Functions. (line 18)
* expressions: Expressions. (line 6)
+* expressions, as patterns: Expression Patterns. (line 6)
* expressions, assignment: Assignment Ops. (line 6)
+* expressions, Boolean: Boolean Ops. (line 6)
* expressions, comparison: Typing and Comparison.
(line 9)
-* expressions, Boolean: Boolean Ops. (line 6)
* expressions, conditional: Conditional Exp. (line 6)
* expressions, selecting: Conditional Exp. (line 6)
-* expressions, as patterns: Expression Patterns. (line 6)
* Extended Regular Expressions (EREs): Bracket Expressions. (line 34)
-* extension API, version number: Auto-set. (line 287)
-* extension API, interaction with namespaces: Namespace And Features.
- (line 22)
* extension API: Extension API Description.
(line 6)
-* extension API, version number <1>: Extension Versioning.
- (line 6)
* extension API, informational variables: Extension API Informational
Variables.
(line 6)
-* extensions, loadable, loading, @load directive: Loading Shared Libraries.
- (line 8)
-* extensions, common, \x escape sequence: Escape Sequences. (line 61)
-* extensions, common, \u escape sequence: Escape Sequences. (line 76)
-* extensions, common, RS as a regexp: gawk split records. (line 6)
-* extensions, common, single character fields: Single Character Fields.
+* extension API, interaction with namespaces: Namespace And Features.
+ (line 22)
+* extension API, version number: Auto-set. (line 287)
+* extension API, version number <1>: Extension Versioning.
(line 6)
+* extensions, Brian Kernighan's awk: BTL. (line 6)
+* extensions, Brian Kernighan's awk <1>: Common Extensions. (line 6)
+* extensions, common, ** operator: Arithmetic Ops. (line 30)
+* extensions, common, **= operator: Assignment Ops. (line 138)
+* extensions, common, /dev/stderr special file: Special FD. (line 48)
* extensions, common, /dev/stdin special file: Special FD. (line 48)
* extensions, common, /dev/stdout special file: Special FD. (line 48)
-* extensions, common, /dev/stderr special file: Special FD. (line 48)
-* extensions, common, ** operator: Arithmetic Ops. (line 30)
-* extensions, common, **= operator: Assignment Ops. (line 139)
+* extensions, common, \u escape sequence: Escape Sequences. (line 76)
+* extensions, common, \x escape sequence: Escape Sequences. (line 61)
+* extensions, common, BINMODE variable: PC Using. (line 18)
* extensions, common, delete to delete entire arrays: Delete. (line 39)
-* extensions, common, length() applied to an array: String Functions.
- (line 219)
* extensions, common, fflush() function: I/O Functions. (line 43)
* extensions, common, func keyword: Definition Syntax. (line 99)
-* extensions, loadable, allocating memory: Memory Allocation Functions.
+* extensions, common, length() applied to an array: String Functions.
+ (line 219)
+* extensions, common, RS as a regexp: gawk split records. (line 6)
+* extensions, common, single character fields: Single Character Fields.
(line 6)
-* extensions, loadable, registration: Registration Functions.
+* extensions, in gawk, not in POSIX awk: POSIX/GNU. (line 6)
+* extensions, loadable, allocating memory: Memory Allocation Functions.
(line 6)
* extensions, loadable, array manipulation in: Array Manipulation.
(line 6)
-* extensions, loadable, search path: Finding Extensions. (line 6)
-* extensions, loadable, example: Extension Example. (line 6)
* extensions, loadable, distributed with gawk: Extension Samples.
(line 6)
+* extensions, loadable, example: Extension Example. (line 6)
* extensions, loadable, gawkextlib project: gawkextlib. (line 6)
-* extensions, Brian Kernighanâs awk: BTL. (line 6)
-* extensions, in gawk, not in POSIX awk: POSIX/GNU. (line 6)
-* extensions, Brian Kernighanâs awk <1>: Common Extensions. (line 6)
+* extensions, loadable, loading, @load directive: Loading Shared Libraries.
+ (line 8)
+* extensions, loadable, registration: Registration Functions.
+ (line 6)
+* extensions, loadable, search path: Finding Extensions. (line 6)
* extensions, mawk: Common Extensions. (line 6)
-* extensions, common, BINMODE variable: PC Using. (line 18)
* extract.awk program: Extract Program. (line 79)
* extraction, of marked strings (internationalization): String Extraction.
(line 6)
@@ -37691,9 +37655,9 @@ Index
* false, logical: Truth Values. (line 6)
* FDL (Free Documentation License): GNU Free Documentation License.
(line 8)
+* features, adding to gawk: Adding Code. (line 6)
* features, deprecated: Obsolete. (line 6)
* features, undocumented: Undocumented. (line 6)
-* features, adding to gawk: Adding Code. (line 6)
* Fenlason, Jay: History. (line 34)
* Fenlason, Jay <1>: Contributors. (line 19)
* fflush: I/O Functions. (line 28)
@@ -37701,101 +37665,101 @@ Index
* field operator $: Fields. (line 19)
* field operators, dollar sign as: Fields. (line 19)
* field separator: Field Separators. (line 16)
+* field separator <1>: User-modified. (line 53)
+* field separator <2>: User-modified. (line 116)
+* field separator, backslash (\) as: Command Line Field Separator.
+ (line 24)
* field separator, choice of: Field Separators. (line 51)
-* field separator, regular expression as: Field Separators. (line 51)
-* field separator, whitespace as: Default Field Splitting.
- (line 6)
+* field separator, FIELDWIDTHS variable and: User-modified. (line 37)
+* field separator, FPAT variable and: User-modified. (line 46)
* field separator, FS variable and: Default Field Splitting.
(line 6)
-* field separator, regular expression as <1>: Regexp Field Splitting.
- (line 6)
+* field separator, in multiline records: Multiple Line. (line 41)
* field separator, on command line: Command Line Field Separator.
(line 6)
-* field separator, backslash (\) as: Command Line Field Separator.
- (line 24)
* field separator, POSIX and: Full Line Fields. (line 16)
-* field separator, in multiline records: Multiple Line. (line 41)
-* field separator, FIELDWIDTHS variable and: User-modified. (line 37)
-* field separator, FPAT variable and: User-modified. (line 46)
-* field separator <1>: User-modified. (line 53)
-* field separator <2>: User-modified. (line 116)
+* field separator, regular expression as: Field Separators. (line 51)
+* field separator, regular expression as <1>: Regexp Field Splitting.
+ (line 6)
* field separator, spaces as: Cut Program. (line 107)
+* field separator, whitespace as: Default Field Splitting.
+ (line 6)
* fields: Reading Files. (line 14)
* fields <1>: Fields. (line 6)
+* fields <2>: Basic High Level. (line 75)
+* fields, adding: Changing Fields. (line 53)
+* fields, changing contents of: Changing Fields. (line 6)
+* fields, cutting: Cut Program. (line 6)
* fields, examining: Fields. (line 6)
* fields, number of: Fields. (line 33)
* fields, numbers: Nonconstant Fields. (line 6)
-* fields, changing contents of: Changing Fields. (line 6)
-* fields, adding: Changing Fields. (line 53)
+* fields, printing: Print Examples. (line 20)
* fields, separating: Field Separators. (line 16)
* fields, separating <1>: Field Separators. (line 16)
* fields, single-character: Single Character Fields.
(line 6)
-* fields, printing: Print Examples. (line 20)
-* fields, cutting: Cut Program. (line 6)
-* fields <2>: Basic High Level. (line 64)
* FIELDWIDTHS variable: Fixed width data. (line 17)
* FIELDWIDTHS variable <1>: User-modified. (line 37)
* file descriptors: Special FD. (line 6)
* file inclusion, @include directive: Include Files. (line 8)
-* file names, standard streams in gawk: Special FD. (line 48)
-* file names, in compatibility mode: Special Caveats. (line 9)
-* file names, distinguishing: Auto-set. (line 55)
* file names, assignments as: Ignoring Assigns. (line 6)
+* file names, distinguishing: Auto-set. (line 55)
+* file names, in compatibility mode: Special Caveats. (line 9)
+* file names, standard streams in gawk: Special FD. (line 48)
* FILENAME variable: Reading Files. (line 6)
-* FILENAME variable, getline, setting with: Getline Notes. (line 19)
* FILENAME variable <1>: Auto-set. (line 108)
-* files, input: Read Terminal. (line 16)
+* FILENAME variable, getline, setting with: Getline Notes. (line 19)
+* files, .gmo: Explaining gettext. (line 42)
+* files, .gmo, specifying directory of: Explaining gettext. (line 54)
+* files, .gmo, specifying directory of <1>: Programmer i18n. (line 48)
+* files, .mo, converting from .po: I18N Example. (line 80)
+* files, .po: Explaining gettext. (line 37)
+* files, .po <1>: Translator i18n. (line 6)
+* files, .po, converting to .mo: I18N Example. (line 80)
+* files, .pot: Explaining gettext. (line 31)
+* files, /dev/... special files: Special FD. (line 48)
+* files, /inet/... (gawk): TCP/IP Networking. (line 6)
+* files, /inet4/... (gawk): TCP/IP Networking. (line 6)
+* files, /inet6/... (gawk): TCP/IP Networking. (line 6)
* files, awk programs in: Long. (line 6)
+* files, awkprof.out: Profiling. (line 6)
* files, awkvars.out: Options. (line 97)
-* files, portable object, generating: Options. (line 168)
-* files, multiple passes over: Other Arguments. (line 64)
-* files, reading, multiline records: Multiple Line. (line 6)
-* files, descriptors: Special FD. (line 6)
-* files, /dev/... special files: Special FD. (line 48)
-* files, output: Close Files And Pipes.
- (line 6)
-* files, processing, ARGIND variable and: Auto-set. (line 50)
* files, closing: I/O Functions. (line 10)
+* files, descriptors: Special FD. (line 6)
+* files, group: Group Functions. (line 6)
+* files, initialization and cleanup: Filetrans Function. (line 6)
+* files, input: Read Terminal. (line 16)
* files, log, timestamps in: Time Functions. (line 6)
* files, managing: Data File Management.
(line 6)
* files, managing, data file boundaries: Filetrans Function. (line 6)
-* files, initialization and cleanup: Filetrans Function. (line 6)
-* files, reading: Rewind Function. (line 6)
-* files, skipping: File Checking. (line 6)
-* files, password: Passwd Functions. (line 16)
-* files, group: Group Functions. (line 6)
-* files, searching for regular expressions: Egrep Program. (line 6)
-* files, splitting: Split Program. (line 6)
-* files, multiple, duplicating output into: Tee Program. (line 6)
-* files, Texinfo, extracting programs from: Extract Program. (line 6)
-* files, source, search path for: Programs Exercises. (line 70)
-* files, /inet/... (gawk): TCP/IP Networking. (line 6)
-* files, /inet4/... (gawk): TCP/IP Networking. (line 6)
-* files, /inet6/... (gawk): TCP/IP Networking. (line 6)
-* files, awkprof.out: Profiling. (line 6)
-* files, .pot: Explaining gettext. (line 31)
-* files, portable object, template file (.pot): Explaining gettext.
- (line 31)
-* files, .po: Explaining gettext. (line 37)
-* files, portable object: Explaining gettext. (line 37)
-* files, .gmo: Explaining gettext. (line 42)
* files, message object: Explaining gettext. (line 42)
-* files, .gmo, specifying directory of: Explaining gettext. (line 54)
+* files, message object, converting from portable object files: I18N Example.
+ (line 80)
* files, message object, specifying directory of: Explaining gettext.
(line 54)
-* files, .gmo, specifying directory of <1>: Programmer i18n. (line 48)
* files, message object, specifying directory of <1>: Programmer i18n.
(line 48)
-* files, .po <1>: Translator i18n. (line 6)
+* files, multiple passes over: Other Arguments. (line 64)
+* files, multiple, duplicating output into: Tee Program. (line 6)
+* files, output: Close Files And Pipes.
+ (line 6)
+* files, password: Passwd Functions. (line 16)
+* files, portable object: Explaining gettext. (line 37)
* files, portable object <1>: Translator i18n. (line 6)
-* files, .po, converting to .mo: I18N Example. (line 80)
-* files, .mo, converting from .po: I18N Example. (line 80)
* files, portable object, converting to message object files: I18N Example.
(line 80)
-* files, message object, converting from portable object files: I18N Example.
- (line 80)
+* files, portable object, generating: Options. (line 168)
+* files, portable object, template file (.pot): Explaining gettext.
+ (line 31)
+* files, processing, ARGIND variable and: Auto-set. (line 50)
+* files, reading: Rewind Function. (line 6)
+* files, reading, multiline records: Multiple Line. (line 6)
+* files, searching for regular expressions: Egrep Program. (line 6)
+* files, skipping: File Checking. (line 6)
+* files, source, search path for: Programs Exercises. (line 70)
+* files, splitting: Split Program. (line 6)
+* files, Texinfo, extracting programs from: Extract Program. (line 6)
* find substring in string: String Functions. (line 174)
* finding extensions: Finding Extensions. (line 6)
* finish debugger command: Debugger Execution Control.
@@ -37804,42 +37768,42 @@ Index
* fixed-width data: Constant Size. (line 6)
* flag variables: Boolean Ops. (line 69)
* flag variables <1>: Tee Program. (line 20)
+* floating-point, numbers: Computer Arithmetic. (line 49)
* floating-point, numbers, arbitrary-precision: Arbitrary Precision Arithmetic.
(line 6)
-* floating-point, numbers: Computer Arithmetic. (line 49)
-* floating-point, numbers, single-precision: Computer Arithmetic.
+* floating-point, numbers, arbitrary-precision <1>: Computer Arithmetic.
(line 61)
* floating-point, numbers, double-precision: Computer Arithmetic.
(line 61)
-* floating-point, numbers, arbitrary-precision <1>: Computer Arithmetic.
+* floating-point, numbers, single-precision: Computer Arithmetic.
(line 61)
* flush buffered output: I/O Functions. (line 28)
* fnmatch() extension function: Extension Sample Fnmatch.
(line 12)
* FNR variable: Records. (line 6)
* FNR variable <1>: Auto-set. (line 118)
-* FNR variable, changing: Auto-set. (line 416)
+* FNR variable, changing: Auto-set. (line 415)
* for statement: For Statement. (line 6)
* for statement, looping over arrays: Scanning an Array. (line 20)
* fork() extension function: Extension Sample Fork.
(line 11)
* format specifiers: Basic Printf. (line 15)
+* format specifiers, mixing regular with positional specifiers: Printf
Ordering.
+ (line 57)
* format specifiers, printf statement: Control Letters. (line 6)
* format specifiers, strftime() function (gawk): Time Functions.
(line 90)
-* format specifiers, mixing regular with positional specifiers: Printf
Ordering.
- (line 57)
* format time string: Time Functions. (line 50)
* formats, numeric output: OFMT. (line 6)
* formatting, output: Printf. (line 6)
* formatting, strings: String Functions. (line 413)
-* forward slash (/), to enclose regular expressions: Regexp. (line 10)
-* forward slash (/), /= operator: Assignment Ops. (line 129)
-* forward slash (/), /= operator, vs. /=.../ regexp constant: Assignment Ops.
- (line 150)
* forward slash (/), / operator: Precedence. (line 54)
+* forward slash (/), /= operator: Assignment Ops. (line 129)
* forward slash (/), /= operator <1>: Precedence. (line 94)
+* forward slash (/), /= operator, vs. /=.../ regexp constant: Assignment Ops.
+ (line 148)
* forward slash (/), patterns and: Expression Patterns. (line 24)
+* forward slash (/), to enclose regular expressions: Regexp. (line 10)
* FPAT variable: Splitting By Content.
(line 33)
* FPAT variable <1>: User-modified. (line 46)
@@ -37852,19 +37816,19 @@ Index
* Free Software Foundation (FSF) <2>: Glossary. (line 370)
* Free Software Foundation (FSF) <3>: Glossary. (line 403)
* FreeBSD: Glossary. (line 747)
-* FS variable, --field-separator option and: Options. (line 21)
-* FS variable, TAB character as: Options. (line 317)
* FS variable: Field Separators. (line 16)
+* FS variable <1>: User-modified. (line 53)
+* FS variable, --field-separator option and: Options. (line 21)
* FS variable, changing value of: Field Separators. (line 35)
* FS variable, containing ^: Regexp Field Splitting.
(line 58)
+* FS variable, in multiline records: Multiple Line. (line 41)
* FS variable, null string as: Single Character Fields.
(line 20)
+* FS variable, running awk programs and: Cut Program. (line 67)
* FS variable, setting from command line: Command Line Field Separator.
(line 6)
-* FS variable, in multiline records: Multiple Line. (line 41)
-* FS variable <1>: User-modified. (line 53)
-* FS variable, running awk programs and: Cut Program. (line 67)
+* FS variable, TAB character as: Options. (line 317)
* FSF (Free Software Foundation): Manual History. (line 6)
* FSF (Free Software Foundation) <1>: Getting. (line 10)
* FSF (Free Software Foundation) <2>: Glossary. (line 370)
@@ -37879,155 +37843,147 @@ Index
* function definition example: Function Example. (line 6)
* function definitions, list in debugger: Debugger Info. (line 30)
* function pointers: Indirect Calls. (line 6)
-* functions, built-in: Function Calls. (line 10)
-* functions, user-defined, next/nextfile statements and: Next Statement.
+* functions, arrays as parameters to: Pass By Value/Reference.
(line 44)
-* functions, user-defined, next/nextfile statements and <1>: Nextfile
Statement.
- (line 47)
+* functions, built-in: Function Calls. (line 10)
* functions, built-in <1>: Functions. (line 6)
* functions, built-in, evaluation order: Calling Built-in. (line 30)
-* functions, string-translation: I18N Functions. (line 6)
-* functions, user-defined: User-defined. (line 6)
* functions, defining: Definition Syntax. (line 10)
-* functions, names of: Definition Syntax. (line 24)
-* functions, recursive: Definition Syntax. (line 89)
-* functions, user-defined, calling: Function Calling. (line 6)
-* functions, arrays as parameters to: Pass By Value/Reference.
- (line 44)
-* functions, undefined: Function Caveats. (line 6)
* functions, library: Library Functions. (line 6)
-* functions, user-defined, library of: Library Functions. (line 6)
-* functions, library, associative arrays and: Library Names. (line 58)
* functions, library, assertions: Assert Function. (line 6)
-* functions, library, rounding numbers: Round Function. (line 6)
-* functions, library, Cliff random numbers: Cliff Random Function.
- (line 6)
+* functions, library, associative arrays and: Library Names. (line 58)
+* functions, library, C library: Getopt Function. (line 6)
* functions, library, character values as numbers: Ordinal Functions.
(line 6)
-* functions, library, merging arrays into strings: Join Function.
+* functions, library, Cliff random numbers: Cliff Random Function.
(line 6)
-* functions, library, managing time: Getlocaltime Function.
+* functions, library, command-line options: Getopt Function. (line 6)
+* functions, library, example program for using: Igawk Program.
+ (line 6)
+* functions, library, group database, reading: Group Functions.
(line 6)
* functions, library, managing data files: Data File Management.
(line 6)
-* functions, library, command-line options: Getopt Function. (line 6)
-* functions, library, C library: Getopt Function. (line 6)
-* functions, library, user database, reading: Passwd Functions.
+* functions, library, managing time: Getlocaltime Function.
(line 6)
-* functions, library, group database, reading: Group Functions.
+* functions, library, merging arrays into strings: Join Function.
(line 6)
-* functions, library, example program for using: Igawk Program.
+* functions, library, rounding numbers: Round Function. (line 6)
+* functions, library, user database, reading: Passwd Functions.
(line 6)
+* functions, names of: Definition Syntax. (line 24)
+* functions, recursive: Definition Syntax. (line 89)
+* functions, string-translation: I18N Functions. (line 6)
+* functions, undefined: Function Caveats. (line 6)
+* functions, user-defined: User-defined. (line 6)
+* functions, user-defined, calling: Function Calling. (line 6)
* functions, user-defined, counts, in a profile: Profiling. (line 137)
+* functions, user-defined, library of: Library Functions. (line 6)
+* functions, user-defined, next/nextfile statements and: Next Statement.
+ (line 44)
+* functions, user-defined, next/nextfile statements and <1>: Nextfile
Statement.
+ (line 47)
* G-d: Acknowledgments. (line 94)
* G., Daniel Richard: Acknowledgments. (line 60)
* G., Daniel Richard <1>: Maintainers. (line 14)
* Garfinkle, Scott: Contributors. (line 35)
* gawk: Preface. (line 13)
+* gawk, ARGIND variable in: Other Arguments. (line 21)
* gawk, awk and: Preface. (line 21)
-* gawk, uses for: Preface. (line 34)
* gawk, awk and <1>: This Manual. (line 14)
-* gawk, newlines in: Statements/Lines. (line 12)
-* gawk, extensions, disabling: Options. (line 308)
-* gawk, version of, printing information about: Options. (line 355)
-* gawk, ARGIND variable in: Other Arguments. (line 21)
-* gawk, PROCINFO array in: Other Arguments. (line 21)
-* gawk, escape sequences: Escape Sequences. (line 136)
-* gawk, escape sequences <1>: Escape Sequences. (line 136)
-* gawk, regular expressions, precedence: Regexp Operator Details.
- (line 142)
-* gawk, interval expressions and: Interval Expressions.
- (line 10)
-* gawk, character classes and: Bracket Expressions. (line 113)
-* gawk, regular expressions, operators: GNU Regexp Operators.
- (line 6)
-* gawk, word-boundary operator: GNU Regexp Operators.
- (line 65)
+* gawk, bitwise operations in: Bitwise Functions. (line 40)
+* gawk, break statement in: Break Statement. (line 51)
+* gawk, character classes and: Bracket Expressions. (line 112)
+* gawk, coding style in: Adding Code. (line 42)
* gawk, command-line options, regular expressions and: GNU Regexp Operators.
(line 72)
-* gawk, regular expressions, case sensitivity: Case-sensitivity.
- (line 26)
-* gawk, IGNORECASE variable in: Case-sensitivity. (line 26)
-* gawk, RT variable in: awk split records. (line 118)
-* gawk, RT variable in <1>: gawk split records. (line 66)
-* gawk, FIELDWIDTHS variable in: Fixed width data. (line 17)
-* gawk, FPAT variable in: Splitting By Content.
- (line 33)
-* gawk, splitting fields and: Testing field creation.
+* gawk, configuring: Configuration Philosophy.
(line 6)
-* gawk, RT variable in <2>: Multiple Line. (line 138)
+* gawk, configuring, options: Additional Configuration Options.
+ (line 6)
+* gawk, continue statement in: Continue Statement. (line 44)
+* gawk, distribution: Distribution contents.
+ (line 6)
+* gawk, dynamic profiling: Profiling. (line 185)
* gawk, ERRNO variable in: Getline. (line 19)
-* gawk, implementation issues, limits: Getline Notes. (line 14)
-* gawk, format-control characters: Control Letters. (line 33)
-* gawk, format-control characters <1>: Control Letters. (line 108)
-* gawk, implementation issues, pipes: Redirection. (line 129)
-* gawk, file names in: Special Files. (line 6)
* gawk, ERRNO variable in <1>: Close Return Value. (line 14)
-* gawk, octal numbers and: Nondecimal-numbers. (line 41)
-* gawk, hexadecimal numbers and: Nondecimal-numbers. (line 41)
-* gawk, regexp constants and: Standard Regexp Constants.
- (line 28)
-* gawk, line continuation in: Conditional Exp. (line 34)
* gawk, ERRNO variable in <2>: BEGINFILE/ENDFILE. (line 32)
-* gawk, break statement in: Break Statement. (line 51)
-* gawk, continue statement in: Continue Statement. (line 44)
-* gawk, predefined variables and: Built-in Variables. (line 14)
+* gawk, ERRNO variable in <3>: Auto-set. (line 87)
+* gawk, ERRNO variable in <4>: TCP/IP Networking. (line 54)
+* gawk, escape sequences: Escape Sequences. (line 136)
+* gawk, escape sequences <1>: Escape Sequences. (line 136)
+* gawk, extensions, disabling: Options. (line 308)
+* gawk, features, adding: Adding Code. (line 6)
+* gawk, features, advanced: Advanced Features. (line 6)
+* gawk, field separators and: User-modified. (line 74)
+* gawk, FIELDWIDTHS variable in: Fixed width data. (line 17)
* gawk, FIELDWIDTHS variable in <1>: User-modified. (line 37)
+* gawk, file names in: Special Files. (line 6)
+* gawk, format-control characters: Control Letters. (line 33)
+* gawk, format-control characters <1>: Control Letters. (line 108)
+* gawk, FPAT variable in: Splitting By Content.
+ (line 33)
* gawk, FPAT variable in <1>: User-modified. (line 46)
-* gawk, field separators and: User-modified. (line 74)
-* gawk, IGNORECASE variable in <1>: User-modified. (line 79)
-* gawk, LINT variable in: User-modified. (line 90)
-* gawk, TEXTDOMAIN variable in: User-modified. (line 154)
-* gawk, ERRNO variable in <3>: Auto-set. (line 87)
* gawk, FUNCTAB array in: Auto-set. (line 134)
-* gawk, PROCINFO array in <1>: Auto-set. (line 148)
-* gawk, version of: Auto-set. (line 262)
-* gawk, RT variable in <3>: Auto-set. (line 355)
-* gawk, SYMTAB array in: Auto-set. (line 359)
-* gawk, IGNORECASE variable in <2>: Array Intro. (line 100)
* gawk, function arguments and: Calling Built-in. (line 16)
+* gawk, hexadecimal numbers and: Nondecimal-numbers. (line 41)
+* gawk, IGNORECASE variable in: Case-sensitivity. (line 26)
+* gawk, IGNORECASE variable in <1>: User-modified. (line 79)
+* gawk, IGNORECASE variable in <2>: Array Intro. (line 102)
* gawk, IGNORECASE variable in <3>: String Functions. (line 57)
-* gawk, timestamps: Time Functions. (line 6)
-* gawk, PROCINFO array in <2>: Time Functions. (line 49)
-* gawk, bitwise operations in: Bitwise Functions. (line 41)
-* gawk, string-translation functions: I18N Functions. (line 6)
-* gawk, features, advanced: Advanced Features. (line 6)
* gawk, IGNORECASE variable in <4>: Array Sorting Functions.
(line 88)
-* gawk, PROCINFO array in <3>: Two-way I/O. (line 114)
-* gawk, ERRNO variable in <4>: TCP/IP Networking. (line 54)
-* gawk, dynamic profiling: Profiling. (line 185)
-* gawk, profiling programs: Profiling. (line 185)
+* gawk, implementation issues: Notes. (line 6)
+* gawk, implementation issues, debugging: Compatibility Mode. (line 6)
+* gawk, implementation issues, downward compatibility: Compatibility Mode.
+ (line 6)
+* gawk, implementation issues, limits: Getline Notes. (line 14)
+* gawk, implementation issues, pipes: Redirection. (line 129)
+* gawk, installing: Installation. (line 6)
* gawk, internationalization: Internationalization.
(line 19)
* gawk, interpreter, adding code to: Using Internal File Ops.
(line 6)
+* gawk, interval expressions and: Interval Expressions.
+ (line 10)
+* gawk, line continuation in: Conditional Exp. (line 34)
+* gawk, LINT variable in: User-modified. (line 90)
* gawk, list of contributors to: Contributors. (line 6)
-* gawk, installing: Installation. (line 6)
-* gawk, source code, obtaining: Getting. (line 6)
-* gawk, distribution: Distribution contents.
- (line 6)
-* gawk, configuring, options: Additional Configuration Options.
- (line 6)
-* gawk, configuring: Configuration Philosophy.
- (line 6)
* gawk, MS-Windows version of: PC Using. (line 12)
+* gawk, newlines in: Statements/Lines. (line 12)
+* gawk, octal numbers and: Nondecimal-numbers. (line 41)
* gawk, OpenVMS version of: OpenVMS Installation.
(line 6)
-* gawk, implementation issues: Notes. (line 6)
-* gawk, implementation issues, downward compatibility: Compatibility Mode.
+* gawk, predefined variables and: Built-in Variables. (line 14)
+* gawk, PROCINFO array in: Other Arguments. (line 21)
+* gawk, PROCINFO array in <1>: Auto-set. (line 148)
+* gawk, PROCINFO array in <2>: Time Functions. (line 49)
+* gawk, PROCINFO array in <3>: Two-way I/O. (line 114)
+* gawk, profiling programs: Profiling. (line 185)
+* gawk, regexp constants and: Standard Regexp Constants.
+ (line 28)
+* gawk, regular expressions, case sensitivity: Case-sensitivity.
+ (line 26)
+* gawk, regular expressions, operators: GNU Regexp Operators.
(line 6)
-* gawk, implementation issues, debugging: Compatibility Mode. (line 6)
-* gawk, features, adding: Adding Code. (line 6)
-* gawk, coding style in: Adding Code. (line 42)
-* gawkbug utility: Bug address. (line 31)
-* gawkextlib project: gawkextlib. (line 6)
-* gawklibpath_append shell function: Shell Startup Files. (line 29)
-* gawklibpath_default shell function: Shell Startup Files. (line 22)
-* gawklibpath_prepend shell function: Shell Startup Files. (line 25)
-* gawkpath_append shell function: Shell Startup Files. (line 19)
-* gawkpath_default shell function: Shell Startup Files. (line 12)
-* gawkpath_prepend shell function: Shell Startup Files. (line 15)
+* gawk, regular expressions, precedence: Regexp Operator Details.
+ (line 142)
+* gawk, RT variable in: awk split records. (line 118)
+* gawk, RT variable in <1>: gawk split records. (line 65)
+* gawk, RT variable in <2>: Multiple Line. (line 138)
+* gawk, RT variable in <3>: Auto-set. (line 355)
+* gawk, source code, obtaining: Getting. (line 6)
+* gawk, splitting fields and: Testing field creation.
+ (line 6)
+* gawk, string-translation functions: I18N Functions. (line 6)
+* gawk, SYMTAB array in: Auto-set. (line 359)
+* gawk, TEXTDOMAIN variable in: User-modified. (line 154)
+* gawk, timestamps: Time Functions. (line 6)
+* gawk, uses for: Preface. (line 34)
+* gawk, version of: Auto-set. (line 262)
+* gawk, version of, printing information about: Options. (line 355)
+* gawk, word-boundary operator: GNU Regexp Operators.
+ (line 65)
* GAWK_LOCALE_DIR environment variable: Other Environment Variables.
(line 70)
* GAWK_LOCALE_DIR environment variable <1>: Explaining gettext.
@@ -38050,6 +38006,14 @@ Index
* GAWK_SOCK_RETRIES environment variable <1>: Nonfatal. (line 53)
* GAWK_STACKSIZE environment variable: Other Environment Variables.
(line 83)
+* gawkbug utility: Bug address. (line 31)
+* gawkextlib project: gawkextlib. (line 6)
+* gawklibpath_append shell function: Shell Startup Files. (line 29)
+* gawklibpath_default shell function: Shell Startup Files. (line 22)
+* gawklibpath_prepend shell function: Shell Startup Files. (line 25)
+* gawkpath_append shell function: Shell Startup Files. (line 19)
+* gawkpath_default shell function: Shell Startup Files. (line 12)
+* gawkpath_prepend shell function: Shell Startup Files. (line 15)
* generate time values: Time Functions. (line 25)
* gensub: Standard Regexp Constants.
(line 43)
@@ -38067,22 +38031,22 @@ Index
* getgruser() function (C library): Group Functions. (line 191)
* getgruser() user-defined function: Group Functions. (line 194)
* getline command: Reading Files. (line 20)
-* getline command, explicit input with: Getline. (line 6)
-* getline command, return values: Getline. (line 19)
-* getline command, into a variable: Getline/Variable. (line 6)
-* getline command, from a file: Getline/File. (line 6)
+* getline command, _gr_init() user-defined function: Group Functions.
+ (line 83)
+* getline command, _pw_init() function: Passwd Functions. (line 154)
+* getline command, BEGINFILE/ENDFILE patterns and: BEGINFILE/ENDFILE.
+ (line 60)
* getline command, coprocesses, using from: Getline/Coprocess.
(line 6)
-* getline command, FILENAME variable and: Getline Notes. (line 19)
-* getline command, variants: Getline Summary. (line 6)
* getline command, coprocesses, using from <1>: Close Files And Pipes.
(line 6)
-* getline command, BEGINFILE/ENDFILE patterns and: BEGINFILE/ENDFILE.
- (line 60)
-* getline command, _pw_init() function: Passwd Functions. (line 154)
-* getline command, _gr_init() user-defined function: Group Functions.
- (line 83)
* getline command, deadlock and: Two-way I/O. (line 53)
+* getline command, explicit input with: Getline. (line 6)
+* getline command, FILENAME variable and: Getline Notes. (line 19)
+* getline command, from a file: Getline/File. (line 6)
+* getline command, into a variable: Getline/Variable. (line 6)
+* getline command, return values: Getline. (line 19)
+* getline command, variants: Getline Summary. (line 6)
* getlocaltime() user-defined function: Getlocaltime Function.
(line 16)
* getopt() function (C library): Getopt Function. (line 15)
@@ -38127,8 +38091,8 @@ Index
* goawk: Other Versions. (line 125)
* Gordon, Assaf: Contributors. (line 108)
* GPL (General Public License): Manual History. (line 11)
-* GPL (General Public License), printing: Options. (line 92)
* GPL (General Public License) <1>: Glossary. (line 394)
+* GPL (General Public License), printing: Options. (line 92)
* grcat program: Group Functions. (line 16)
* Grigera, Juan: Contributors. (line 58)
* group database, reading: Group Functions. (line 6)
@@ -38147,8 +38111,8 @@ Index
* Hankerson, Darrel: Acknowledgments. (line 60)
* Hankerson, Darrel <1>: Contributors. (line 61)
* Haque, John: Contributors. (line 111)
-* Hartholz, Marshall: Acknowledgments. (line 38)
* Hartholz, Elaine: Acknowledgments. (line 38)
+* Hartholz, Marshall: Acknowledgments. (line 38)
* Hasegawa, Isamu: Contributors. (line 97)
* help debugger command: Miscellaneous Debugger Commands.
(line 67)
@@ -38158,54 +38122,54 @@ Index
* histsort.awk program: History Sorting. (line 25)
* Hughes, Phil: Acknowledgments. (line 43)
* HUP signal, for dynamic profiling: Profiling. (line 217)
-* hyphen (-), file names beginning with: Options. (line 63)
+* hyphen (-), - operator: Precedence. (line 51)
+* hyphen (-), - operator <1>: Precedence. (line 57)
* hyphen (-), -- end of options marker: Options. (line 360)
-* hyphen (-), in bracket expressions: Bracket Expressions. (line 25)
-* hyphen (-), -= operator: Assignment Ops. (line 129)
* hyphen (-), -- operator: Increment Ops. (line 48)
* hyphen (-), -- operator <1>: Precedence. (line 45)
-* hyphen (-), - operator: Precedence. (line 51)
-* hyphen (-), - operator <1>: Precedence. (line 57)
+* hyphen (-), -= operator: Assignment Ops. (line 129)
* hyphen (-), -= operator <1>: Precedence. (line 94)
+* hyphen (-), file names beginning with: Options. (line 63)
+* hyphen (-), in bracket expressions: Bracket Expressions. (line 25)
* i debugger command (alias for info): Debugger Info. (line 13)
* id utility: Id Program. (line 6)
* id.awk program: Id Program. (line 34)
-* if statement, use of regexps in: Regexp Usage. (line 19)
-* if statement, actions, changing: Ranges. (line 25)
* if statement: If Statement. (line 6)
+* if statement, actions, changing: Ranges. (line 25)
+* if statement, use of regexps in: Regexp Usage. (line 19)
* igawk.sh program: Igawk Program. (line 124)
* ignore breakpoint: Breakpoint Control. (line 87)
* ignore debugger command: Breakpoint Control. (line 87)
-* IGNORECASE variable, with ~ and !~ operators: Case-sensitivity.
- (line 26)
* IGNORECASE variable: User-modified. (line 79)
-* IGNORECASE variable, array indices and: Array Intro. (line 100)
-* IGNORECASE variable, in example programs: Library Functions.
- (line 50)
+* IGNORECASE variable, array indices and: Array Intro. (line 102)
* IGNORECASE variable, array sorting functions and: Array Sorting Functions.
(line 88)
+* IGNORECASE variable, in example programs: Library Functions.
+ (line 50)
+* IGNORECASE variable, with ~ and !~ operators: Case-sensitivity.
+ (line 26)
* Illumos, POSIX-compliant awk: Other Versions. (line 109)
-* implementation issues, gawk, limits: Getline Notes. (line 14)
-* implementation issues, gawk, limits <1>: Redirection. (line 129)
* implementation issues, gawk: Notes. (line 6)
* implementation issues, gawk, debugging: Compatibility Mode. (line 6)
+* implementation issues, gawk, limits: Getline Notes. (line 14)
+* implementation issues, gawk, limits <1>: Redirection. (line 129)
* implicit namespace: Changing The Namespace.
(line 25)
* in operator: Comparison Operators.
(line 11)
* in operator <1>: Precedence. (line 82)
* in operator <2>: For Statement. (line 78)
+* in operator, index existence in multidimensional arrays: Multidimensional.
+ (line 41)
+* in operator, order of array access: Scanning an Array. (line 48)
* in operator, testing if array element exists: Reference to Elements.
(line 38)
* in operator, use in loops: Scanning an Array. (line 17)
-* in operator, order of array access: Scanning an Array. (line 48)
-* in operator, index existence in multidimensional arrays: Multidimensional.
- (line 41)
* @include directive: Include Files. (line 8)
* including files, @include directive: Include Files. (line 8)
* increment operators: Increment Ops. (line 6)
* index: String Functions. (line 174)
-* indexing arrays: Array Intro. (line 49)
+* indexing arrays: Array Intro. (line 51)
* indirect function calls: Indirect Calls. (line 6)
* indirect function calls, @-notation: Indirect Calls. (line 47)
* infinite precision: Arbitrary Precision Arithmetic.
@@ -38214,80 +38178,80 @@ Index
* initialization, automatic: More Complex. (line 28)
* inplace extension: Extension Sample Inplace.
(line 6)
-* input, standard: Read Terminal. (line 6)
-* input, splitting into records: Records. (line 6)
-* input, multiline records: Multiple Line. (line 6)
+* input, data, nondecimal: Nondecimal Data. (line 6)
* input, explicit: Getline. (line 6)
+* input, multiline records: Multiple Line. (line 6)
+* input, splitting into records: Records. (line 6)
+* input, standard: Read Terminal. (line 6)
* input, standard <1>: Special FD. (line 6)
-* input, data, nondecimal: Nondecimal Data. (line 6)
-* input files, running awk without: Read Terminal. (line 6)
-* input files, running awk without <1>: Read Terminal. (line 16)
-* input files, examples: Sample Data Files. (line 6)
-* input files, variable assignments and: Other Arguments. (line 34)
-* input files, reading: Reading Files. (line 6)
* input files: Reading Files. (line 6)
* input files, closing: Close Files And Pipes.
(line 6)
* input files, counting elements in: Wc Program. (line 6)
+* input files, examples: Sample Data Files. (line 6)
+* input files, reading: Reading Files. (line 6)
+* input files, running awk without: Read Terminal. (line 6)
+* input files, running awk without <1>: Read Terminal. (line 16)
+* input files, variable assignments and: Other Arguments. (line 34)
* input pipeline: Getline/Pipe. (line 10)
* input record, length of: String Functions. (line 196)
* input redirection: Getline/File. (line 6)
-* input/output, from BEGIN and END: I/O And BEGIN/END. (line 6)
* input/output, binary: User-modified. (line 15)
+* input/output, from BEGIN and END: I/O And BEGIN/END. (line 6)
* input/output, functions: I/O Functions. (line 6)
* input/output, two-way: Two-way I/O. (line 27)
* insomnia, cure for: Alarm Program. (line 6)
* installing gawk: Installation. (line 6)
+* installing gawk, Cygwin: Cygwin. (line 21)
* installing gawk, MS-Windows: PC Binary Installation.
(line 6)
-* installing gawk, Cygwin: Cygwin. (line 21)
* installing gawk, OpenVMS: OpenVMS Installation.
(line 6)
* instruction tracing, in debugger: Debugger Info. (line 90)
* instructions, trace of internal: Options. (line 197)
* int: Numeric Functions. (line 23)
* INT signal (MS-Windows): Profiling. (line 220)
+* INT_CHAIN_MAX environment variable: Other Environment Variables.
+ (line 87)
* integer array indices: Numeric Array Subscripts.
(line 31)
-* integers, unsigned: Computer Arithmetic. (line 41)
* integers, arbitrary precision: Arbitrary Precision Integers.
(line 6)
+* integers, unsigned: Computer Arithmetic. (line 41)
* interacting with other programs: I/O Functions. (line 105)
-* internationalization, localization, character classes: Bracket Expressions.
- (line 113)
-* internationalization, localization: User-modified. (line 154)
* internationalization: I18N Functions. (line 6)
+* internationalization <1>: I18N and L10N. (line 6)
+* internationalization, localization: User-modified. (line 154)
* internationalization, localization <1>: Internationalization.
(line 19)
+* internationalization, localization <2>: I18N and L10N. (line 6)
+* internationalization, localization, character classes: Bracket Expressions.
+ (line 112)
+* internationalization, localization, currency symbols: Explaining gettext.
+ (line 104)
* internationalization, localization, gawk and: Internationalization.
(line 19)
-* internationalization <1>: I18N and L10N. (line 6)
-* internationalization, localization <2>: I18N and L10N. (line 6)
* internationalization, localization, locale categories: Explaining gettext.
(line 81)
-* internationalization, localization, monetary information: Explaining gettext.
- (line 104)
-* internationalization, localization, currency symbols: Explaining gettext.
- (line 104)
* internationalization, localization, marked strings: Programmer i18n.
(line 13)
+* internationalization, localization, monetary information: Explaining gettext.
+ (line 104)
* internationalization, localization, portability and: I18N Portability.
(line 6)
* internationalizing a program: Explaining gettext. (line 6)
-* interpreted programs: Basic High Level. (line 14)
+* interpreted programs: Basic High Level. (line 16)
* interpreted programs <1>: Glossary. (line 443)
* interval expressions, regexp operator: Regexp Operator Details.
(line 118)
-* INT_CHAIN_MAX environment variable: Other Environment Variables.
- (line 87)
* inventory-shipped file: Sample Data Files. (line 32)
* invoke shell command: I/O Functions. (line 105)
* isarray: Type Functions. (line 11)
* isnumeric() user-defined function: Isnumeric Function. (line 11)
+* ISO: Glossary. (line 454)
* ISO, ISO 8601 date and time standard: Time Functions. (line 185)
* ISO, ISO 8859-1 character set: Glossary. (line 194)
* ISO, ISO Latin-1 character set: Glossary. (line 194)
-* ISO: Glossary. (line 454)
* Jacobs, Andrew: Passwd Functions. (line 90)
* Jaegermann, Michal: Acknowledgments. (line 60)
* Jaegermann, Michal <1>: Contributors. (line 46)
@@ -38306,19 +38270,19 @@ Index
* Kelly, Terence <2>: Feature History. (line 510)
* Kenobi, Obi-Wan: Undocumented. (line 6)
* Kernighan, Brian: History. (line 21)
-* Kernighan, Brian, quotes: Conventions. (line 38)
* Kernighan, Brian <1>: Acknowledgments. (line 79)
-* Kernighan, Brian, quotes <1>: Comma Separated Fields.
- (line 46)
-* Kernighan, Brian, quotes <2>: Getline/Pipe. (line 6)
-* Kernighan, Brian, quotes <3>: Concatenation. (line 6)
-* Kernighan, Brian, quotes <4>: Library Functions. (line 12)
-* Kernighan, Brian, quotes <5>: Programs Exercises. (line 26)
* Kernighan, Brian <2>: BTL. (line 6)
* Kernighan, Brian <3>: Contributors. (line 12)
* Kernighan, Brian <4>: Other Versions. (line 13)
* Kernighan, Brian <5>: Basic Data Typing. (line 54)
* Kernighan, Brian <6>: Glossary. (line 204)
+* Kernighan, Brian, quotes: Conventions. (line 38)
+* Kernighan, Brian, quotes <1>: Comma Separated Fields.
+ (line 45)
+* Kernighan, Brian, quotes <2>: Getline/Pipe. (line 6)
+* Kernighan, Brian, quotes <3>: Concatenation. (line 6)
+* Kernighan, Brian, quotes <4>: Library Functions. (line 12)
+* Kernighan, Brian, quotes <5>: Programs Exercises. (line 26)
* kill command, dynamic profiling: Profiling. (line 194)
* knights, jedi: Undocumented. (line 6)
* Kwok, Conrad: Contributors. (line 35)
@@ -38329,7 +38293,7 @@ Index
* Langston, Peter: Advanced Features. (line 6)
* LANGUAGE environment variable: Explaining gettext. (line 120)
* LANGUAGE environment variable <1>: I18N Example. (line 68)
-* languages, data-driven: Basic High Level. (line 76)
+* languages, data-driven: Basic High Level. (line 87)
* LC_ALL environment variable: Split Program. (line 39)
* LC_ALL environment variable <1>: I18N Example. (line 68)
* LC_ALL environment variable <2>: Bug address. (line 18)
@@ -38343,14 +38307,14 @@ Index
* LC_MONETARY locale category: Explaining gettext. (line 104)
* LC_NUMERIC locale category: Explaining gettext. (line 108)
* LC_TIME locale category: Explaining gettext. (line 112)
-* left angle bracket (<), < operator (I/O): Getline/File. (line 6)
* left angle bracket (<), < operator: Comparison Operators.
(line 11)
+* left angle bracket (<), < operator <1>: Precedence. (line 64)
+* left angle bracket (<), < operator (I/O): Getline/File. (line 6)
* left angle bracket (<), <= operator: Comparison Operators.
(line 11)
-* left angle bracket (<), < operator <1>: Precedence. (line 64)
* left angle bracket (<), <= operator <1>: Precedence. (line 64)
-* left shift, bitwise: Bitwise Functions. (line 33)
+* left shift, bitwise: Bitwise Functions. (line 32)
* leftmost longest match: Multiple Line. (line 26)
* length: String Functions. (line 189)
* length of input record: String Functions. (line 196)
@@ -38359,45 +38323,45 @@ Index
* LGPL (Lesser General Public License): Glossary. (line 489)
* libmawk: Other Versions. (line 153)
* libraries of awk functions: Library Functions. (line 6)
+* libraries of awk functions, assertions: Assert Function. (line 6)
* libraries of awk functions, associative arrays and: Library Names.
(line 58)
-* libraries of awk functions, assertions: Assert Function. (line 6)
-* libraries of awk functions, rounding numbers: Round Function.
- (line 6)
* libraries of awk functions, character values as numbers: Ordinal Functions.
(line 6)
-* libraries of awk functions, merging arrays into strings: Join Function.
+* libraries of awk functions, command-line options: Getopt Function.
(line 6)
-* libraries of awk functions, managing, time: Getlocaltime Function.
+* libraries of awk functions, example program for using: Igawk Program.
+ (line 6)
+* libraries of awk functions, group database, reading: Group Functions.
(line 6)
* libraries of awk functions, managing, data files: Data File Management.
(line 6)
-* libraries of awk functions, command-line options: Getopt Function.
+* libraries of awk functions, managing, time: Getlocaltime Function.
(line 6)
-* libraries of awk functions, user database, reading: Passwd Functions.
+* libraries of awk functions, merging arrays into strings: Join Function.
(line 6)
-* libraries of awk functions, group database, reading: Group Functions.
+* libraries of awk functions, rounding numbers: Round Function.
(line 6)
-* libraries of awk functions, example program for using: Igawk Program.
+* libraries of awk functions, user database, reading: Passwd Functions.
(line 6)
* line breaks: Statements/Lines. (line 6)
-* line continuations, with C shell: Statements/Lines. (line 45)
-* line continuations, in print statement: Print Examples. (line 75)
* line continuations: Boolean Ops. (line 64)
* line continuations, gawk: Conditional Exp. (line 34)
+* line continuations, in print statement: Print Examples. (line 75)
+* line continuations, with C shell: Statements/Lines. (line 45)
* lines, blank, printing: Print. (line 22)
-* lines, matching ranges of: Ranges. (line 6)
-* lines, skipping between markers: Ranges. (line 43)
* lines, counting: Wc Program. (line 6)
* lines, duplicate, removing: History Sorting. (line 6)
-* lint checking, empty programs: Command Line. (line 16)
-* lint checking, issuing warnings: Options. (line 221)
-* lint checking, POSIXLY_CORRECT environment variable: Options.
- (line 402)
+* lines, matching ranges of: Ranges. (line 6)
+* lines, skipping between markers: Ranges. (line 43)
* lint checking: User-modified. (line 90)
* lint checking, array subscripts: Uninitialized Subscripts.
(line 43)
* lint checking, array subscripts <1>: Delete. (line 34)
+* lint checking, empty programs: Command Line. (line 16)
+* lint checking, issuing warnings: Options. (line 221)
+* lint checking, POSIXLY_CORRECT environment variable: Options.
+ (line 402)
* lint checking, undefined functions: Function Caveats. (line 23)
* LINT variable: User-modified. (line 90)
* list all global variables, in debugger: Debugger Info. (line 48)
@@ -38421,17 +38385,17 @@ Index
* login information: Passwd Functions. (line 16)
* long options: Command Line. (line 13)
* loops: While Statement. (line 6)
-* loops, while: While Statement. (line 6)
-* loops, do-while: Do Statement. (line 6)
-* loops, for, iterative: For Statement. (line 6)
+* loops, break statement and: Break Statement. (line 6)
* loops, continue statement and: For Statement. (line 67)
+* loops, count for header, in a profile: Profiling. (line 131)
+* loops, do-while: Do Statement. (line 6)
* loops, exiting: Break Statement. (line 6)
-* loops, break statement and: Break Statement. (line 6)
* loops, for, array scanning: Scanning an Array. (line 6)
-* loops, count for header, in a profile: Profiling. (line 131)
+* loops, for, iterative: For Statement. (line 6)
+* loops, while: While Statement. (line 6)
* ls utility: Very Simple. (line 54)
* ls utility <1>: More Complex. (line 15)
-* lshift: Bitwise Functions. (line 48)
+* lshift: Bitwise Functions. (line 47)
* lvalues/rvalues: Assignment Ops. (line 31)
* mail-list file: Sample Data Files. (line 6)
* mailing labels, printing: Labels Program. (line 6)
@@ -38442,16 +38406,16 @@ Index
* mark parity: Ordinal Functions. (line 45)
* marked string extraction (internationalization): String Extraction.
(line 6)
-* Marx, Groucho: Increment Ops. (line 60)
+* Marx, Groucho: Increment Ops. (line 59)
* match: String Functions. (line 229)
* match regexp in string: String Functions. (line 229)
* match() function, RSTART/RLENGTH variables: String Functions.
(line 246)
* match() function, side effects: String Functions. (line 246)
-* matching, leftmost longest: Multiple Line. (line 26)
* matching, expressions: Typing and Comparison.
(line 9)
-* matching, null strings: String Functions. (line 575)
+* matching, leftmost longest: Multiple Line. (line 26)
+* matching, null strings: String Functions. (line 574)
* mawk utility: Escape Sequences. (line 136)
* mawk utility <1>: Getline/Pipe. (line 62)
* mawk utility <2>: Concatenation. (line 36)
@@ -38463,14 +38427,14 @@ Index
* memory, allocating for extensions: Memory Allocation Functions.
(line 6)
* message object files: Explaining gettext. (line 42)
+* message object files, converting from portable object files: I18N Example.
+ (line 80)
* message object files, specifying directory of: Explaining gettext.
(line 54)
* message object files, specifying directory of <1>: Programmer i18n.
(line 48)
-* message object files, converting from portable object files: I18N Example.
- (line 80)
* messages from extensions: Printing Messages. (line 6)
-* metacharacters, escape sequences for: Escape Sequences. (line 155)
+* metacharacters, escape sequences for: Escape Sequences. (line 154)
* metacharacters, in regular expressions: Regexp Operators. (line 6)
* minimum precision required by MPFR library: Auto-set. (line 279)
* Minshall, Greg: Getopt Function. (line 105)
@@ -38494,49 +38458,49 @@ Index
(line 43)
* name management: Internal Name Management.
(line 6)
-* names, functions: Definition Syntax. (line 24)
* names, arrays/variables: Library Names. (line 6)
+* names, functions: Definition Syntax. (line 24)
* names, functions <1>: Library Names. (line 6)
-* namespace, definition of: Global Namespace. (line 6)
-* namespace, standard awk, global: Global Namespace. (line 6)
-* namespace, default: Default Namespace. (line 6)
* namespace, awk: Default Namespace. (line 6)
+* namespace, default: Default Namespace. (line 6)
+* namespace, definition of: Global Namespace. (line 6)
+* namespace, example code: Namespace Example. (line 6)
* namespace, implicit: Changing The Namespace.
(line 25)
* namespace, pushing and popping: Changing The Namespace.
(line 29)
-* namespace, example code: Namespace Example. (line 6)
+* namespace, standard awk, global: Global Namespace. (line 6)
* @namespace directive: Changing The Namespace.
(line 6)
* @namespace directive <1>: Changing The Namespace.
(line 37)
-* namespaces, qualified names: Qualified Names. (line 6)
+* namespaces, backwards compatibility: Namespace Summary. (line 28)
* namespaces, changing: Changing The Namespace.
(line 6)
-* namespaces, naming rules: Naming Rules. (line 6)
-* namespaces, interaction with, profiler: Namespace And Features.
- (line 9)
-* namespaces, interaction with, pretty printer: Namespace And Features.
- (line 9)
* namespaces, interaction with, debugger: Namespace And Features.
(line 17)
* namespaces, interaction with, extension API: Namespace And Features.
(line 22)
-* namespaces, backwards compatibility: Namespace Summary. (line 28)
-* naming issues, functions: Definition Syntax. (line 24)
+* namespaces, interaction with, pretty printer: Namespace And Features.
+ (line 9)
+* namespaces, interaction with, profiler: Namespace And Features.
+ (line 9)
+* namespaces, naming rules: Naming Rules. (line 6)
+* namespaces, qualified names: Qualified Names. (line 6)
* naming issues: Library Names. (line 6)
+* naming issues, functions: Definition Syntax. (line 24)
* naming rules, namespace and component names: Naming Rules. (line 6)
* Neacsu, Mircea: Other Versions. (line 156)
* NetBSD: Glossary. (line 747)
-* networks, support for: Special Network. (line 6)
* networks, programming: TCP/IP Networking. (line 6)
+* networks, support for: Special Network. (line 6)
* newlines: Statements/Lines. (line 6)
* newlines <1>: Options. (line 314)
-* newlines, in dynamic regexps: Computed Regexps. (line 60)
-* newlines, in regexp constants: Computed Regexps. (line 70)
+* newlines <2>: Boolean Ops. (line 69)
* newlines, as record separators: awk split records. (line 12)
+* newlines, in dynamic regexps: Computed Regexps. (line 59)
+* newlines, in regexp constants: Computed Regexps. (line 70)
* newlines, printing: Print Examples. (line 11)
-* newlines <2>: Boolean Ops. (line 69)
* newlines, separating statements in actions: Action Overview.
(line 19)
* newlines, separating statements in actions <1>: Statements. (line 10)
@@ -38544,23 +38508,23 @@ Index
(line 43)
* next file statement: Feature History. (line 170)
* next statement: Boolean Ops. (line 95)
+* next statement <1>: Next Statement. (line 6)
* next statement, BEGIN/END patterns and: I/O And BEGIN/END. (line 36)
* next statement, BEGINFILE/ENDFILE patterns and: BEGINFILE/ENDFILE.
(line 56)
-* next statement <1>: Next Statement. (line 6)
* next statement, user-defined functions and: Next Statement. (line 44)
+* nextfile statement: Nextfile Statement. (line 6)
* nextfile statement, BEGIN/END patterns and: I/O And BEGIN/END.
(line 36)
* nextfile statement, BEGINFILE/ENDFILE patterns and: BEGINFILE/ENDFILE.
(line 32)
-* nextfile statement: Nextfile Statement. (line 6)
* nextfile statement, user-defined functions and: Nextfile Statement.
(line 47)
* nexti debugger command: Debugger Execution Control.
(line 49)
* NF variable: Fields. (line 33)
-* NF variable, decrementing: Changing Fields. (line 107)
* NF variable <1>: Auto-set. (line 123)
+* NF variable, decrementing: Changing Fields. (line 107)
* ni debugger command (alias for nexti): Debugger Execution Control.
(line 49)
* noassign.awk program: Ignoring Assigns. (line 15)
@@ -38570,99 +38534,99 @@ Index
* not Boolean-logic operator: Boolean Ops. (line 6)
* NR variable: Records. (line 6)
* NR variable <1>: Auto-set. (line 143)
-* NR variable, changing: Auto-set. (line 416)
-* null strings, in gawk arguments, quoting and: Quoting. (line 82)
-* null strings, in gawk arguments, quoting and <1>: Other Arguments.
- (line 73)
+* NR variable, changing: Auto-set. (line 415)
* null strings: awk split records. (line 108)
* null strings <1>: Regexp Field Splitting.
(line 42)
-* null strings, converting numbers to strings: Strings And Numbers.
- (line 21)
* null strings <2>: Truth Values. (line 6)
+* null strings <3>: Basic Data Typing. (line 26)
* null strings, as array subscripts: Uninitialized Subscripts.
(line 43)
+* null strings, converting numbers to strings: Strings And Numbers.
+ (line 21)
* null strings, deleting array elements and: Delete. (line 27)
-* null strings, matching: String Functions. (line 575)
-* null strings <3>: Basic Data Typing. (line 26)
+* null strings, in gawk arguments, quoting and: Quoting. (line 82)
+* null strings, in gawk arguments, quoting and <1>: Other Arguments.
+ (line 72)
+* null strings, matching: String Functions. (line 574)
* number of array elements: String Functions. (line 219)
* number sign (#), #! (executable scripts): Executable Scripts.
(line 6)
* number sign (#), commenting: Comments. (line 6)
-* numbers, octal: Nondecimal-numbers. (line 6)
-* numbers, hexadecimal: Nondecimal-numbers. (line 6)
-* numbers, converting: Strings And Numbers. (line 6)
-* numbers, converting, to strings: User-modified. (line 30)
-* numbers, converting, to strings <1>: User-modified. (line 107)
* numbers, as array subscripts: Numeric Array Subscripts.
(line 6)
-* numbers, converting <1>: Bitwise Functions. (line 110)
-* numbers, as string of bits: Bitwise Functions. (line 110)
-* numbers, rounding: Round Function. (line 6)
+* numbers, as string of bits: Bitwise Functions. (line 109)
+* numbers, as values of characters: Ordinal Functions. (line 6)
* numbers, Cliff random: Cliff Random Function.
(line 6)
-* numbers, as values of characters: Ordinal Functions. (line 6)
-* numeric, output format: OFMT. (line 6)
+* numbers, converting: Strings And Numbers. (line 6)
+* numbers, converting <1>: Bitwise Functions. (line 109)
+* numbers, converting, to strings: User-modified. (line 30)
+* numbers, converting, to strings <1>: User-modified. (line 107)
+* numbers, hexadecimal: Nondecimal-numbers. (line 6)
+* numbers, octal: Nondecimal-numbers. (line 6)
+* numbers, rounding: Round Function. (line 6)
* numeric, constants: Scalar Constants. (line 6)
-* numeric, strings: Variable Typing. (line 67)
* numeric, functions: Numeric Functions. (line 6)
+* numeric, output format: OFMT. (line 6)
+* numeric, strings: Variable Typing. (line 67)
* o debugger command (alias for option): Debugger Info. (line 57)
* obsolete features: Obsolete. (line 6)
* octal numbers: Nondecimal-numbers. (line 6)
* octal values, enabling interpretation of: Options. (line 261)
* OFMT variable: OFMT. (line 15)
-* OFMT variable, POSIX awk and: OFMT. (line 32)
-* OFMT variable <1>: Strings And Numbers. (line 56)
+* OFMT variable <1>: Strings And Numbers. (line 55)
* OFMT variable <2>: User-modified. (line 107)
+* OFMT variable, POSIX awk and: OFMT. (line 32)
* OFS variable: Changing Fields. (line 64)
* OFS variable <1>: Output Separators. (line 6)
* OFS variable <2>: User-modified. (line 116)
* op-codes, trace of internal: Options. (line 197)
* OpenBSD: Glossary. (line 747)
* OpenSolaris: Other Versions. (line 100)
-* operating systems, BSD-based: Manual History. (line 28)
* operating systems: Installation. (line 6)
+* operating systems, BSD-based: Manual History. (line 28)
+* operating systems, PC, gawk on: PC Using. (line 6)
* operating systems, PC, gawk on, installing: PC Installation.
(line 6)
-* operating systems, PC, gawk on: PC Using. (line 6)
* operating systems, porting gawk to: New Ports. (line 6)
* operations, bitwise: Bitwise Functions. (line 6)
-* operators, string-matching: Regexp Usage. (line 19)
+* operators, arithmetic: Arithmetic Ops. (line 6)
+* operators, assignment: Assignment Ops. (line 6)
+* operators, assignment <1>: Assignment Ops. (line 31)
+* operators, assignment, evaluation order: Assignment Ops. (line 110)
+* operators, comparison: Comparison Operators.
+ (line 6)
+* operators, decrement/increment: Increment Ops. (line 6)
* operators, GNU-specific: GNU Regexp Operators.
(line 6)
-* operators, string-matching, for buffers: GNU Regexp Operators.
- (line 50)
-* operators, word-boundary (gawk): GNU Regexp Operators.
- (line 65)
* operators, input/output: Getline/File. (line 6)
* operators, input/output <1>: Getline/Pipe. (line 10)
* operators, input/output <2>: Getline/Coprocess. (line 6)
* operators, input/output <3>: Redirection. (line 22)
* operators, input/output <4>: Redirection. (line 96)
-* operators, arithmetic: Arithmetic Ops. (line 6)
-* operators, string: Concatenation. (line 9)
-* operators, assignment: Assignment Ops. (line 6)
-* operators, assignment <1>: Assignment Ops. (line 31)
-* operators, assignment, evaluation order: Assignment Ops. (line 110)
-* operators, decrement/increment: Increment Ops. (line 6)
-* operators, precedence of: Increment Ops. (line 60)
-* operators, comparison: Comparison Operators.
- (line 6)
-* operators, short-circuit: Boolean Ops. (line 59)
-* operators, precedence of <1>: Precedence. (line 6)
* operators, input/output <5>: Precedence. (line 64)
* operators, input/output <6>: Precedence. (line 64)
* operators, input/output <7>: Precedence. (line 64)
+* operators, precedence of: Increment Ops. (line 59)
+* operators, precedence of <1>: Precedence. (line 6)
+* operators, short-circuit: Boolean Ops. (line 59)
+* operators, string: Concatenation. (line 9)
+* operators, string-matching: Regexp Usage. (line 19)
+* operators, string-matching, for buffers: GNU Regexp Operators.
+ (line 50)
+* operators, word-boundary (gawk): GNU Regexp Operators.
+ (line 65)
* option debugger command: Debugger Info. (line 57)
+* options, command-line: Options. (line 6)
+* options, command-line, end of: Options. (line 58)
* options, command-line, invoking awk: Command Line. (line 6)
+* options, command-line, processing: Getopt Function. (line 6)
+* options, deprecated: Obsolete. (line 6)
* options, long: Command Line. (line 13)
-* options, command-line: Options. (line 6)
* options, long <1>: Options. (line 6)
-* options, command-line, end of: Options. (line 58)
* options, printing list of: Options. (line 175)
-* options, deprecated: Obsolete. (line 6)
-* options, command-line, processing: Getopt Function. (line 6)
-* or: Bitwise Functions. (line 51)
+* or: Bitwise Functions. (line 50)
* OR bitwise operation: Bitwise Functions. (line 6)
* or Boolean-logic operator: Boolean Ops. (line 6)
* ord() extension function: Extension Sample Ord.
@@ -38671,16 +38635,16 @@ Index
* order of evaluation, concatenation: Concatenation. (line 41)
* ORS variable: Output Separators. (line 20)
* ORS variable <1>: User-modified. (line 121)
-* output, records: Output Separators. (line 20)
+* output, buffering: I/O Functions. (line 32)
+* output, buffering <1>: I/O Functions. (line 166)
+* output, duplicating into files: Tee Program. (line 6)
+* output, files, closing: Close Files And Pipes.
+ (line 6)
* output, format specifier, OFMT: OFMT. (line 15)
* output, formatted: Printf. (line 6)
* output, pipes: Redirection. (line 57)
+* output, records: Output Separators. (line 20)
* output, standard: Special FD. (line 6)
-* output, files, closing: Close Files And Pipes.
- (line 6)
-* output, buffering: I/O Functions. (line 32)
-* output, buffering <1>: I/O Functions. (line 168)
-* output, duplicating into files: Tee Program. (line 6)
* output redirection: Redirection. (line 6)
* output wrapper: Output Wrappers. (line 6)
* output, nonfatal: Nonfatal. (line 6)
@@ -38689,99 +38653,99 @@ Index
* package, definition of: Global Namespace. (line 18)
* Papadopoulos, Panos: Contributors. (line 131)
* parent process ID of gawk process: Auto-set. (line 251)
+* parentheses (), in a profile: Profiling. (line 146)
* parentheses (), regexp operator: Regexp Operator Details.
(line 77)
-* parentheses (), in a profile: Profiling. (line 146)
* password file: Passwd Functions. (line 16)
* Path environment variable: PC Binary Installation.
(line 6)
* PATH environment variable: Derived Files. (line 94)
* patsplit: String Functions. (line 315)
-* patterns, default: Very Simple. (line 34)
-* patterns, regexp constants as: Regexp Usage. (line 6)
* patterns: Patterns and Actions.
(line 6)
-* patterns, types of: Pattern Overview. (line 15)
-* patterns, regexp constants as <1>: Regexp Patterns. (line 6)
-* patterns, expressions as: Expression Patterns. (line 6)
-* patterns, comparison expressions as: Expression Patterns. (line 14)
-* patterns, regexp constants as <2>: Expression Patterns. (line 34)
* patterns, Boolean expressions as: Expression Patterns. (line 39)
-* patterns, ranges in: Ranges. (line 6)
-* patterns, empty: Empty. (line 6)
+* patterns, comparison expressions as: Expression Patterns. (line 14)
* patterns, counts, in a profile: Profiling. (line 118)
-* pawk (profiling version of Brian Kernighanâs awk): Other Versions.
+* patterns, default: Very Simple. (line 34)
+* patterns, empty: Empty. (line 6)
+* patterns, expressions as: Expression Patterns. (line 6)
+* patterns, ranges in: Ranges. (line 6)
+* patterns, regexp constants as: Regexp Usage. (line 6)
+* patterns, regexp constants as <1>: Regexp Patterns. (line 6)
+* patterns, regexp constants as <2>: Expression Patterns. (line 34)
+* patterns, types of: Pattern Overview. (line 15)
+* pawk (profiling version of Brian Kernighan's awk): Other Versions.
(line 82)
* pawk, awk-like facilities for Python: Other Versions. (line 161)
-* PC operating systems, gawk on, installing: PC Installation. (line 6)
* PC operating systems, gawk on: PC Using. (line 6)
-* percent sign (%), %= operator: Assignment Ops. (line 129)
+* PC operating systems, gawk on, installing: PC Installation. (line 6)
* percent sign (%), % operator: Precedence. (line 54)
+* percent sign (%), %= operator: Assignment Ops. (line 129)
* percent sign (%), %= operator <1>: Precedence. (line 94)
* performance, checking issues: Performance bugs. (line 6)
* period (.), regexp operator: Regexp Operator Details.
(line 40)
* Perl: Future Extensions. (line 6)
-* persistent memory, compiled into gawk: Auto-set. (line 246)
* persistent memory: Persistent Memory. (line 6)
+* persistent memory, compiled into gawk: Auto-set. (line 246)
* Peters, Arno: Contributors. (line 88)
* Peterson, Hal: Contributors. (line 40)
-* pipe, input: Getline/Pipe. (line 10)
-* pipe, output: Redirection. (line 57)
* pipe, closing: Close Files And Pipes.
(line 6)
+* pipe, input: Getline/Pipe. (line 10)
+* pipe, output: Redirection. (line 57)
* pipe output, speeding up: Noflush. (line 6)
* platform running on: Auto-set. (line 224)
* Plauger, P.J.: Library Functions. (line 12)
* plug-in: Extension Intro. (line 6)
-* plus sign (+), regexp operator: Regexp Operator Details.
- (line 107)
-* plus sign (+), += operator: Assignment Ops. (line 81)
+* plus sign (+), + operator: Precedence. (line 51)
+* plus sign (+), + operator <1>: Precedence. (line 57)
* plus sign (+), ++ operator: Increment Ops. (line 11)
* plus sign (+), ++ operator <1>: Increment Ops. (line 40)
* plus sign (+), ++ operator <2>: Precedence. (line 45)
-* plus sign (+), + operator: Precedence. (line 51)
-* plus sign (+), + operator <1>: Precedence. (line 57)
+* plus sign (+), += operator: Assignment Ops. (line 81)
* plus sign (+), += operator <1>: Precedence. (line 94)
+* plus sign (+), regexp operator: Regexp Operator Details.
+ (line 107)
* PMA memory allocator: Auto-set. (line 246)
* PMA memory allocator <1>: Persistent Memory. (line 6)
* PMA_VERBOSITY environment variable: Other Environment Variables.
(line 29)
* PMA_VERBOSITY environment variable <1>: Persistent Memory. (line 94)
* pointers to functions: Indirect Calls. (line 6)
-* portability, #! (executable scripts): Executable Scripts. (line 29)
+* portability: Escape Sequences. (line 119)
+* portability, ** operator and: Arithmetic Ops. (line 85)
+* portability, **= operator and: Assignment Ops. (line 144)
+* portability, #! (executable scripts): Executable Scripts. (line 28)
* portability, ARGV variable: Executable Scripts. (line 55)
* portability, backslash continuation and: Statements/Lines. (line 30)
-* portability, POSIXLY_CORRECT environment variable: Options. (line 422)
-* portability: Escape Sequences. (line 119)
* portability, backslash in escape sequences: Escape Sequences.
- (line 124)
-* portability, data files as single record: gawk split records.
- (line 77)
-* portability, NF variable, decrementing: Changing Fields. (line 115)
+ (line 123)
* portability, close() function and: Close Files And Pipes.
(line 85)
-* portability, new awk vs. old awk: Strings And Numbers. (line 56)
-* portability, ** operator and: Arithmetic Ops. (line 85)
-* portability, **= operator and: Assignment Ops. (line 145)
-* portability, operators: Increment Ops. (line 60)
-* portability, operators, not in POSIX awk: Precedence. (line 97)
+* portability, data files as single record: gawk split records.
+ (line 75)
* portability, deleting array elements: Delete. (line 56)
-* portability, length() function: String Functions. (line 198)
-* portability, substr() function: String Functions. (line 542)
-* portability, functions, defining: Definition Syntax. (line 114)
-* portability, next statement in user-defined functions: Function Caveats.
- (line 26)
* portability, example programs: Library Functions. (line 42)
+* portability, functions, defining: Definition Syntax. (line 114)
+* portability, gawk: New Ports. (line 6)
* portability, gettext library and: Explaining gettext. (line 11)
* portability, internationalization and: I18N Portability. (line 6)
-* portability, gawk: New Ports. (line 6)
-* portable object, files, generating: Options. (line 168)
-* portable object, template files: Explaining gettext. (line 31)
+* portability, length() function: String Functions. (line 198)
+* portability, new awk vs. old awk: Strings And Numbers. (line 55)
+* portability, next statement in user-defined functions: Function Caveats.
+ (line 26)
+* portability, NF variable, decrementing: Changing Fields. (line 115)
+* portability, operators: Increment Ops. (line 59)
+* portability, operators, not in POSIX awk: Precedence. (line 97)
+* portability, POSIXLY_CORRECT environment variable: Options. (line 422)
+* portability, substr() function: String Functions. (line 542)
* portable object, files: Explaining gettext. (line 37)
* portable object, files <1>: Translator i18n. (line 6)
* portable object, files, converting to message object files: I18N Example.
(line 80)
+* portable object, files, generating: Options. (line 168)
+* portable object, template files: Explaining gettext. (line 31)
* porting gawk: New Ports. (line 6)
* positional specifiers, printf statement: Format Modifiers. (line 13)
* positional specifiers, printf statement <1>: Printf Ordering.
@@ -38789,52 +38753,52 @@ Index
* positional specifiers, printf statement, mixing with regular formats: Printf
Ordering.
(line 57)
* POSIX, awk and: Preface. (line 21)
-* POSIX, programs, implementing in awk: Clones. (line 6)
* POSIX, gawk extensions not included in: POSIX/GNU. (line 6)
+* POSIX, programs, implementing in awk: Clones. (line 6)
* POSIX awk: This Manual. (line 14)
-* POSIX awk, GNU long options and: Options. (line 15)
-* POSIX awk, backslashes in string constants: Escape Sequences.
- (line 124)
-* POSIX awk, period (.), using: Regexp Operator Details.
- (line 47)
-* POSIX awk, regular expressions and: Regexp Operator Details.
- (line 142)
-* POSIX awk, interval expressions in: Interval Expressions.
- (line 6)
-* POSIX awk, bracket expressions and: Bracket Expressions. (line 34)
-* POSIX awk, bracket expressions and, character classes: Bracket Expressions.
- (line 40)
-* POSIX awk, bracket expressions and, character classes <1>: Bracket
Expressions.
- (line 113)
-* POSIX awk, field separators and: Full Line Fields. (line 16)
+* POSIX awk <1>: Assignment Ops. (line 138)
+* POSIX awk, ** operator and: Precedence. (line 97)
+* POSIX awk, **= operator and: Assignment Ops. (line 144)
* POSIX awk, < operator and: Getline/File. (line 26)
* POSIX awk, | I/O operator and: Getline/Pipe. (line 56)
-* POSIX awk, OFMT variable and: OFMT. (line 32)
-* POSIX awk, printf format strings and: Format Modifiers. (line 157)
-* POSIX awk, OFMT variable and <1>: Strings And Numbers. (line 56)
* POSIX awk, arithmetic operators and: Arithmetic Ops. (line 30)
-* POSIX awk <1>: Assignment Ops. (line 139)
-* POSIX awk, **= operator and: Assignment Ops. (line 145)
-* POSIX awk, numeric strings and: Variable Typing. (line 67)
-* POSIX awk, ** operator and: Precedence. (line 97)
+* POSIX awk, backslashes in string constants: Escape Sequences.
+ (line 123)
* POSIX awk, BEGIN/END patterns: I/O And BEGIN/END. (line 15)
+* POSIX awk, bracket expressions and: Bracket Expressions. (line 34)
+* POSIX awk, bracket expressions and, character classes: Bracket Expressions.
+ (line 40)
+* POSIX awk, bracket expressions and, character classes <1>: Bracket
Expressions.
+ (line 112)
* POSIX awk, break statement and: Break Statement. (line 51)
+* POSIX awk, changes in awk versions: POSIX. (line 6)
* POSIX awk, continue statement and: Continue Statement. (line 44)
-* POSIX awk, next/nextfile statements and: Next Statement. (line 44)
* POSIX awk, CONVFMT variable and: User-modified. (line 30)
-* POSIX awk, functions and, length(): String Functions. (line 198)
-* POSIX awk, functions and, gsub()/sub(): Gory Details. (line 95)
-* POSIX awk, timestamps and: Time Functions. (line 6)
* POSIX awk, date utility and: Time Functions. (line 254)
+* POSIX awk, field separators and: Full Line Fields. (line 16)
* POSIX awk, function keyword in: Definition Syntax. (line 99)
-* POSIX awk, changes in awk versions: POSIX. (line 6)
+* POSIX awk, functions and, gsub()/sub(): Gory Details. (line 93)
+* POSIX awk, functions and, length(): String Functions. (line 198)
+* POSIX awk, GNU long options and: Options. (line 15)
+* POSIX awk, interval expressions in: Interval Expressions.
+ (line 6)
+* POSIX awk, next/nextfile statements and: Next Statement. (line 44)
+* POSIX awk, numeric strings and: Variable Typing. (line 67)
+* POSIX awk, OFMT variable and: OFMT. (line 32)
+* POSIX awk, OFMT variable and <1>: Strings And Numbers. (line 55)
+* POSIX awk, period (.), using: Regexp Operator Details.
+ (line 47)
+* POSIX awk, printf format strings and: Format Modifiers. (line 157)
+* POSIX awk, regular expressions and: Regexp Operator Details.
+ (line 142)
+* POSIX awk, timestamps and: Time Functions. (line 6)
* POSIX mode: Options. (line 308)
* POSIX mode <1>: Options. (line 402)
* POSIX mode <2>: Regexp Operator Details.
(line 47)
* POSIX mode <3>: Input Summary. (line 69)
* POSIX mode <4>: Special Caveats. (line 9)
-* POSIX mode <5>: Close Return Value. (line 40)
+* POSIX mode <5>: Close Return Value. (line 39)
* POSIX mode <6>: Scalar Constants. (line 63)
* POSIX mode <7>: Locale influences conversions.
(line 41)
@@ -38855,14 +38819,14 @@ Index
* POSIXLY_CORRECT environment variable <3>: Locale influences conversions.
(line 41)
* PREC variable: User-modified. (line 126)
+* precedence: Increment Ops. (line 59)
+* precedence <1>: Precedence. (line 6)
* precedence, regexp operators: Regexp Operator Details.
(line 137)
-* precedence: Increment Ops. (line 60)
-* precedence <1>: Precedence. (line 6)
-* predefined variables, -v option, setting with: Options. (line 44)
* predefined variables: Built-in Variables. (line 6)
-* predefined variables, user-modifiable: User-modified. (line 6)
+* predefined variables, -v option, setting with: Options. (line 44)
* predefined variables, conveying information: Auto-set. (line 6)
+* predefined variables, user-modifiable: User-modified. (line 6)
* pretty printer, interaction with namespaces: Namespace And Features.
(line 9)
* pretty printing: Options. (line 273)
@@ -38871,10 +38835,10 @@ Index
* print debugger command: Viewing And Changing Data.
(line 39)
* print statement: Printing. (line 16)
+* print statement, BEGIN/END patterns and: I/O And BEGIN/END. (line 15)
* print statement, commas, omitting: Print Examples. (line 30)
-* print statement, line continuations and: Print Examples. (line 75)
* print statement, I/O operators in: Precedence. (line 70)
-* print statement, BEGIN/END patterns and: I/O And BEGIN/END. (line 15)
+* print statement, line continuations and: Print Examples. (line 75)
* print statement, OFMT variable and: User-modified. (line 116)
* print statement, sprintf() function and: Round Function. (line 6)
* print variables, in debugger: Viewing And Changing Data.
@@ -38882,43 +38846,43 @@ Index
* printf debugger command: Viewing And Changing Data.
(line 57)
* printf statement: Printing. (line 16)
-* printf statement, columns, aligning: Print Examples. (line 69)
* printf statement <1>: Printf. (line 6)
-* printf statement, syntax of: Basic Printf. (line 6)
+* printf statement, columns, aligning: Print Examples. (line 69)
* printf statement, format-control characters: Control Letters.
(line 6)
+* printf statement, I/O operators in: Precedence. (line 70)
* printf statement, modifiers: Format Modifiers. (line 6)
* printf statement, positional specifiers: Format Modifiers. (line 13)
-* printf statement, I/O operators in: Precedence. (line 70)
-* printf statement, sprintf() function and: Round Function. (line 6)
* printf statement, positional specifiers <1>: Printf Ordering.
(line 6)
* printf statement, positional specifiers, mixing with regular formats: Printf
Ordering.
(line 57)
-* printing, list of options: Options. (line 175)
+* printf statement, sprintf() function and: Round Function. (line 6)
+* printf statement, syntax of: Basic Printf. (line 6)
* printing: Printing. (line 6)
-* printing, user information: Id Program. (line 6)
-* printing, unduplicated lines of text: Uniq Program. (line 6)
+* printing, list of options: Options. (line 175)
* printing, mailing labels: Labels Program. (line 6)
* printing, messages from extensions: Printing Messages. (line 6)
+* printing, unduplicated lines of text: Uniq Program. (line 6)
+* printing, user information: Id Program. (line 6)
* private variables: Library Names. (line 11)
* process group ID of gawk process: Auto-set. (line 240)
* process ID of gawk process: Auto-set. (line 243)
* processes, two-way communications with: Two-way I/O. (line 6)
* processing data: Basic High Level. (line 6)
-* PROCINFO array, not flushing pipe buffers: Noflush. (line 6)
-* PROCINFO array, nonfatal output: Nonfatal. (line 6)
* PROCINFO array: Auto-set. (line 148)
-* PROCINFO array, platform running on: Auto-set. (line 224)
-* PROCINFO array, values of sorted_in: Controlling Scanning.
- (line 26)
* PROCINFO array <1>: Time Functions. (line 49)
* PROCINFO array <2>: Passwd Functions. (line 6)
+* PROCINFO array, communications via ptys and: Two-way I/O. (line 114)
+* PROCINFO array, group membership and: Group Functions. (line 6)
+* PROCINFO array, nonfatal output: Nonfatal. (line 6)
+* PROCINFO array, not flushing pipe buffers: Noflush. (line 6)
+* PROCINFO array, platform running on: Auto-set. (line 224)
* PROCINFO array, testing the field splitting: Passwd Functions.
(line 154)
-* PROCINFO array, group membership and: Group Functions. (line 6)
* PROCINFO array, user and group ID numbers and: Id Program. (line 15)
-* PROCINFO array, communications via ptys and: Two-way I/O. (line 114)
+* PROCINFO array, values of sorted_in: Controlling Scanning.
+ (line 26)
* profiler, interaction with namespaces: Namespace And Features.
(line 9)
* profiling awk programs: Profiling. (line 6)
@@ -38927,29 +38891,29 @@ Index
* profiling, pretty printing, difference with: Profiling. (line 235)
* program identifiers: Auto-set. (line 193)
* program, definition of: Getting Started. (line 21)
+* programming, basic steps: Basic High Level. (line 21)
* programming, concepts: Basic Concepts. (line 6)
* programming, concepts <1>: Basic Concepts. (line 6)
-* programming, basic steps: Basic High Level. (line 19)
-* programming conventions, exit statement: Exit Statement. (line 38)
+* programming conventions, --non-decimal-data option: Nondecimal Data.
+ (line 35)
* programming conventions, ARGC/ARGV variables: Auto-set. (line 35)
+* programming conventions, exit statement: Exit Statement. (line 38)
+* programming conventions, function parameters: Return Statement.
+ (line 44)
* programming conventions, functions, calling: Calling Built-in.
(line 10)
* programming conventions, functions, writing: Definition Syntax.
(line 71)
-* programming conventions, function parameters: Return Statement.
- (line 44)
-* programming conventions, private variable names: Library Names.
- (line 23)
-* programming conventions, --non-decimal-data option: Nondecimal Data.
- (line 35)
* programming conventions, gawk extensions: Internal File Ops.
(line 45)
+* programming conventions, private variable names: Library Names.
+ (line 23)
* programming language, recipe for: History. (line 6)
+* programming languages, Ada: Glossary. (line 11)
* programming languages, data-driven vs. procedural: Getting Started.
(line 12)
* programming languages, Go: Other Versions. (line 125)
* programming languages, Go <1>: Other Versions. (line 133)
-* programming languages, Ada: Glossary. (line 11)
* programming languages, Java: Glossary. (line 466)
* Proulx, Bob: Asking for help. (line 23)
* pwcat program: Passwd Functions. (line 23)
@@ -38959,19 +38923,19 @@ Index
* qualified name, definition of: Qualified Names. (line 6)
* qualified name, use of: Qualified Names. (line 17)
* Quanstrom, Erik: Alarm Program. (line 8)
+* question mark (?), ?: operator: Precedence. (line 91)
* question mark (?), regexp operator: Regexp Operator Details.
(line 113)
* question mark (?), regexp operator <1>: GNU Regexp Operators.
(line 61)
-* question mark (?), ?: operator: Precedence. (line 91)
* QuikTrim Awk: Other Versions. (line 178)
* quit debugger command: Miscellaneous Debugger Commands.
(line 100)
* QUIT signal (MS-Windows): Profiling. (line 220)
-* quoting, in gawk command lines: Long. (line 26)
* quoting, for small awk programs: Comments. (line 27)
+* quoting, in gawk command lines: Long. (line 26)
+* quoting, in gawk command lines <1>: Other Arguments. (line 72)
* quoting, in gawk command lines, tricks for: Quoting. (line 91)
-* quoting, in gawk command lines <1>: Other Arguments. (line 73)
* r debugger command (alias for run): Debugger Execution Control.
(line 62)
* Rakitzis, Byron: History Sorting. (line 25)
@@ -38979,11 +38943,11 @@ Index
* Ramey, Chet <1>: General Data Types. (line 6)
* Ramming, J. Christopher: Other Versions. (line 167)
* rand: Numeric Functions. (line 33)
+* random numbers, Cliff: Cliff Random Function.
+ (line 6)
* random numbers, rand()/srand() functions: Numeric Functions.
(line 33)
* random numbers, seed of: Numeric Functions. (line 63)
-* random numbers, Cliff: Cliff Random Function.
- (line 6)
* range expressions (regexps): Bracket Expressions. (line 6)
* range patterns: Ranges. (line 6)
* range patterns, line continuation and: Ranges. (line 64)
@@ -39007,19 +38971,19 @@ Index
(line 29)
* recipe for a programming language: History. (line 6)
* record separators: awk split records. (line 6)
-* record separators, newlines as: awk split records. (line 12)
+* record separators <1>: User-modified. (line 135)
* record separators, changing: awk split records. (line 85)
+* record separators, newlines as: awk split records. (line 12)
* record separators, regular expressions as: awk split records.
(line 118)
* record separators, with multiline records: Multiple Line. (line 10)
-* record separators <1>: User-modified. (line 135)
* records: Reading Files. (line 14)
-* records, splitting input into: Records. (line 6)
-* records, terminating: awk split records. (line 118)
-* records, treating files as: gawk split records. (line 104)
+* records <1>: Basic High Level. (line 75)
* records, multiline: Multiple Line. (line 6)
* records, printing: Print. (line 22)
-* records <1>: Basic High Level. (line 64)
+* records, splitting input into: Records. (line 6)
+* records, terminating: awk split records. (line 118)
+* records, treating files as: gawk split records. (line 102)
* recursive functions: Definition Syntax. (line 89)
* redirect gawk output, in debugger: Debugger Info. (line 73)
* redirection, of input: Getline/File. (line 6)
@@ -39029,50 +38993,50 @@ Index
(line 77)
* regexp: Regexp. (line 6)
* regexp constants: Regexp Usage. (line 57)
-* regexp constants, slashes vs. quotes: Computed Regexps. (line 30)
-* regexp constants, vs. string constants: Computed Regexps. (line 40)
* regexp constants <1>: Regexp Constants. (line 6)
-* regexp constants, in gawk: Standard Regexp Constants.
- (line 28)
-* regexp constants, /=.../, /= operator and: Assignment Ops. (line 150)
* regexp constants <2>: Comparison Operators.
- (line 104)
+ (line 103)
+* regexp constants, /=.../, /= operator and: Assignment Ops. (line 148)
* regexp constants, as patterns: Expression Patterns. (line 34)
+* regexp constants, in gawk: Standard Regexp Constants.
+ (line 28)
+* regexp constants, slashes vs. quotes: Computed Regexps. (line 30)
+* regexp constants, vs. string constants: Computed Regexps. (line 40)
* regexps, empty: Regexp Operator Details.
- (line 151)
+ (line 150)
* register loadable extension: Registration Functions.
(line 6)
-* regular expressions, interval expressions and: Options. (line 329)
* regular expressions: Regexp. (line 6)
-* regular expressions, as patterns: Regexp Usage. (line 6)
-* regular expressions, operators: Regexp Usage. (line 19)
-* regular expressions, operators <1>: Regexp Operators. (line 6)
* regular expressions, anchors in: Regexp Operator Details.
(line 18)
-* regular expressions, operators, precedence of: Regexp Operator Details.
- (line 137)
-* regular expressions, leftmost longest match: Leftmost Longest.
+* regular expressions, as field separators: Field Separators. (line 51)
+* regular expressions, as field separators <1>: Regexp Field Splitting.
(line 6)
+* regular expressions, as patterns: Regexp Usage. (line 6)
+* regular expressions, as patterns <1>: Regexp Patterns. (line 6)
+* regular expressions, as record separators: awk split records.
+ (line 118)
+* regular expressions, case sensitivity: Case-sensitivity. (line 6)
+* regular expressions, case sensitivity <1>: User-modified. (line 79)
* regular expressions, computed: Computed Regexps. (line 6)
* regular expressions, dynamic: Computed Regexps. (line 6)
* regular expressions, dynamic, with embedded newlines: Computed Regexps.
- (line 60)
-* regular expressions, operators, gawk: GNU Regexp Operators.
- (line 6)
-* regular expressions, operators, for words: GNU Regexp Operators.
+ (line 59)
+* regular expressions, gawk, command-line options: GNU Regexp Operators.
+ (line 72)
+* regular expressions, interval expressions and: Options. (line 329)
+* regular expressions, leftmost longest match: Leftmost Longest.
(line 6)
+* regular expressions, operators: Regexp Usage. (line 19)
+* regular expressions, operators <1>: Regexp Operators. (line 6)
* regular expressions, operators, for buffers: GNU Regexp Operators.
(line 50)
-* regular expressions, gawk, command-line options: GNU Regexp Operators.
- (line 72)
-* regular expressions, case sensitivity: Case-sensitivity. (line 6)
-* regular expressions, as record separators: awk split records.
- (line 118)
-* regular expressions, as field separators: Field Separators. (line 51)
-* regular expressions, as field separators <1>: Regexp Field Splitting.
+* regular expressions, operators, for words: GNU Regexp Operators.
(line 6)
-* regular expressions, as patterns <1>: Regexp Patterns. (line 6)
-* regular expressions, case sensitivity <1>: User-modified. (line 79)
+* regular expressions, operators, gawk: GNU Regexp Operators.
+ (line 6)
+* regular expressions, operators, precedence of: Regexp Operator Details.
+ (line 137)
* regular expressions, searching for: Egrep Program. (line 6)
* replace in string: String Functions. (line 438)
* retrying input: Retrying Input. (line 6)
@@ -39086,36 +39050,36 @@ Index
* revtwoway extension: Extension Sample Rev2way.
(line 12)
* rewind() user-defined function: Rewind Function. (line 15)
+* right angle bracket (>), > operator: Comparison Operators.
+ (line 11)
+* right angle bracket (>), > operator <1>: Precedence. (line 64)
* right angle bracket (>), > operator (I/O): Redirection. (line 22)
-* right angle bracket (>), >> operator (I/O): Redirection. (line 50)
* right angle bracket (>), >= operator: Comparison Operators.
(line 11)
-* right angle bracket (>), > operator: Comparison Operators.
- (line 11)
* right angle bracket (>), >= operator <1>: Precedence. (line 64)
-* right angle bracket (>), > operator <1>: Precedence. (line 64)
+* right angle bracket (>), >> operator (I/O): Redirection. (line 50)
* right angle bracket (>), >> operator (I/O) <1>: Precedence. (line 64)
-* right shift, bitwise: Bitwise Functions. (line 33)
+* right shift, bitwise: Bitwise Functions. (line 32)
* Ritchie, Dennis: Basic Data Typing. (line 54)
* RLENGTH variable: Auto-set. (line 342)
* RLENGTH variable, match() function and: String Functions. (line 246)
-* Robbins, Miriam: Acknowledgments. (line 94)
-* Robbins, Jean: Acknowledgments. (line 94)
-* Robbins, Harry: Acknowledgments. (line 94)
* Robbins, Arnold: Command Line Field Separator.
(line 71)
-* Robbins, Bill: Getline/Pipe. (line 40)
-* Robbins, Miriam <1>: Getline/Pipe. (line 40)
* Robbins, Arnold <1>: Getline/Pipe. (line 40)
* Robbins, Arnold <2>: Passwd Functions. (line 90)
-* Robbins, Miriam <2>: Passwd Functions. (line 90)
* Robbins, Arnold <3>: Alarm Program. (line 6)
-* Robbins, Malka: Internationalization.
- (line 6)
* Robbins, Arnold <4>: General Data Types. (line 6)
* Robbins, Arnold <5>: Contributors. (line 154)
* Robbins, Arnold <6>: Maintainers. (line 14)
* Robbins, Arnold <7>: Future Extensions. (line 6)
+* Robbins, Bill: Getline/Pipe. (line 40)
+* Robbins, Harry: Acknowledgments. (line 94)
+* Robbins, Jean: Acknowledgments. (line 94)
+* Robbins, Malka: Internationalization.
+ (line 6)
+* Robbins, Miriam: Acknowledgments. (line 94)
+* Robbins, Miriam <1>: Getline/Pipe. (line 40)
+* Robbins, Miriam <2>: Passwd Functions. (line 90)
* Rommel, Kai Uwe: Contributors. (line 43)
* round to nearest integer: Numeric Functions. (line 23)
* round() user-defined function: Round Function. (line 16)
@@ -39124,13 +39088,13 @@ Index
* ROUNDMODE variable <1>: Setting the rounding mode.
(line 6)
* RS variable: awk split records. (line 12)
-* RS variable, multiline records and: Multiple Line. (line 17)
* RS variable <1>: User-modified. (line 135)
-* rshift: Bitwise Functions. (line 55)
+* RS variable, multiline records and: Multiple Line. (line 17)
+* rshift: Bitwise Functions. (line 54)
* RSTART variable: Auto-set. (line 348)
* RSTART variable, match() function and: String Functions. (line 246)
* RT variable: awk split records. (line 118)
-* RT variable <1>: gawk split records. (line 66)
+* RT variable <1>: gawk split records. (line 65)
* RT variable <2>: Multiple Line. (line 138)
* RT variable <3>: Auto-set. (line 355)
* Rubin, Paul: History. (line 34)
@@ -39157,13 +39121,13 @@ Index
* Schreiber, Rita: Acknowledgments. (line 38)
* search and replace in strings: String Functions. (line 98)
* search for substring: String Functions. (line 174)
-* search paths, for source files: AWKPATH Variable. (line 6)
-* search paths, for loadable extensions: AWKLIBPATH Variable. (line 6)
* search paths: Programs Exercises. (line 70)
-* search paths, for source files <1>: Programs Exercises. (line 70)
* search paths <1>: PC Using. (line 12)
-* search paths, for source files <2>: PC Using. (line 12)
* search paths <2>: OpenVMS Running. (line 50)
+* search paths, for loadable extensions: AWKLIBPATH Variable. (line 6)
+* search paths, for source files: AWKPATH Variable. (line 6)
+* search paths, for source files <1>: Programs Exercises. (line 70)
+* search paths, for source files <2>: PC Using. (line 12)
* search paths, for source files <3>: OpenVMS Running. (line 50)
* searching, files for regular expressions: Egrep Program. (line 6)
* searching, for words: Dupword Program. (line 6)
@@ -39171,26 +39135,26 @@ Index
* sed utility <1>: Simple Sed. (line 6)
* sed utility <2>: Glossary. (line 16)
* seeding random number generator: Numeric Functions. (line 63)
+* semicolon (;), AWKPATH variable and: PC Using. (line 12)
+* semicolon (;), separating rules: Statements/Lines. (line 118)
* semicolon (;), separating statements in actions: Statements/Lines.
(line 118)
-* semicolon (;), separating rules: Statements/Lines. (line 118)
* semicolon (;), separating statements in actions <1>: Action Overview.
(line 19)
* semicolon (;), separating statements in actions <2>: Statements.
(line 10)
-* semicolon (;), AWKPATH variable and: PC Using. (line 12)
+* separators, field: User-modified. (line 53)
+* separators, field <1>: User-modified. (line 116)
+* separators, field, FIELDWIDTHS variable and: User-modified. (line 37)
+* separators, field, FPAT variable and: User-modified. (line 46)
+* separators, field, FS variable and: Default Field Splitting.
+ (line 6)
* separators, for records: awk split records. (line 6)
* separators, for records <1>: awk split records. (line 85)
+* separators, for records <2>: User-modified. (line 135)
* separators, for records, regular expressions as: awk split records.
(line 118)
-* separators, field, FS variable and: Default Field Splitting.
- (line 6)
* separators, for statements in actions: Action Overview. (line 19)
-* separators, field, FIELDWIDTHS variable and: User-modified. (line 37)
-* separators, field, FPAT variable and: User-modified. (line 46)
-* separators, field: User-modified. (line 53)
-* separators, field <1>: User-modified. (line 116)
-* separators, for records <2>: User-modified. (line 135)
* separators, subscript: User-modified. (line 148)
* set breakpoint: Breakpoint Control. (line 11)
* set debugger command: Viewing And Changing Data.
@@ -39199,100 +39163,100 @@ Index
* set watchpoint: Viewing And Changing Data.
(line 70)
* shadowing of variable values: Definition Syntax. (line 77)
-* shell function, gawkpath_default: Shell Startup Files. (line 12)
-* shell function, gawkpath_prepend: Shell Startup Files. (line 15)
-* shell function, gawkpath_append: Shell Startup Files. (line 19)
+* shell function, gawklibpath_append: Shell Startup Files. (line 29)
* shell function, gawklibpath_default: Shell Startup Files. (line 22)
* shell function, gawklibpath_prepend: Shell Startup Files. (line 25)
-* shell function, gawklibpath_append: Shell Startup Files. (line 29)
+* shell function, gawkpath_append: Shell Startup Files. (line 19)
+* shell function, gawkpath_default: Shell Startup Files. (line 12)
+* shell function, gawkpath_prepend: Shell Startup Files. (line 15)
* shell quoting, rules for: Quoting. (line 6)
-* shell quoting, rules for <1>: Other Arguments. (line 73)
-* shells, scripts: One-shot. (line 22)
+* shell quoting, rules for <1>: Other Arguments. (line 72)
+* shells, piping commands into: Redirection. (line 135)
+* shells, quoting: Using Shell Variables.
+ (line 12)
* shells, quoting, rules for: Quoting. (line 18)
+* shells, scripts: One-shot. (line 22)
* shells, sea: Undocumented. (line 9)
-* shells, piping commands into: Redirection. (line 136)
* shells, variables: Using Shell Variables.
(line 6)
-* shells, quoting: Using Shell Variables.
- (line 12)
-* shift, bitwise: Bitwise Functions. (line 33)
+* shift, bitwise: Bitwise Functions. (line 32)
* short-circuit operators: Boolean Ops. (line 59)
-* show in debugger, function arguments: Debugger Info. (line 18)
+* show in debugger, all source files: Debugger Info. (line 45)
* show in debugger, breakpoints: Debugger Info. (line 21)
+* show in debugger, function arguments: Debugger Info. (line 18)
* show in debugger, local variables: Debugger Info. (line 34)
* show in debugger, name of current source file: Debugger Info.
(line 37)
-* show in debugger, all source files: Debugger Info. (line 45)
* show in debugger, watchpoints: Debugger Info. (line 51)
* si debugger command (alias for stepi): Debugger Execution Control.
(line 75)
-* side effects, FILENAME variable: Getline Notes. (line 19)
* side effects: Concatenation. (line 41)
-* side effects, assignment expressions: Assignment Ops. (line 22)
* side effects <1>: Increment Ops. (line 11)
-* side effects, decrement/increment operators: Increment Ops. (line 11)
-* side effects <2>: Increment Ops. (line 75)
-* side effects, Boolean operators: Boolean Ops. (line 30)
-* side effects, conditional expressions: Conditional Exp. (line 22)
-* side effects, function calls: Function Calls. (line 57)
-* side effects, statements: Action Overview. (line 32)
+* side effects <2>: Increment Ops. (line 74)
* side effects, array indexing: Reference to Elements.
(line 43)
-* side effects, match() function: String Functions. (line 246)
-* side effects, sub() function: String Functions. (line 492)
-* side effects, gsub() function: String Functions. (line 492)
* side effects, asort() function: Array Sorting Functions.
(line 24)
* side effects, asorti() function: Array Sorting Functions.
(line 24)
-* sidebar, Recipe for a Programming Language: History. (line 6)
-* sidebar, Understanding #!: Executable Scripts. (line 27)
-* sidebar, Quoting Shell Variables On The awk Command Line: Other Arguments.
- (line 71)
+* side effects, assignment expressions: Assignment Ops. (line 22)
+* side effects, Boolean operators: Boolean Ops. (line 30)
+* side effects, conditional expressions: Conditional Exp. (line 22)
+* side effects, decrement/increment operators: Increment Ops. (line 11)
+* side effects, FILENAME variable: Getline Notes. (line 19)
+* side effects, function calls: Function Calls. (line 57)
+* side effects, gsub() function: String Functions. (line 492)
+* side effects, match() function: String Functions. (line 246)
+* side effects, statements: Action Overview. (line 32)
+* side effects, sub() function: String Functions. (line 492)
+* sidebar, A Constant's Base Does Not Affect Its Value: Nondecimal-numbers.
+ (line 63)
+* sidebar, A Note About Fuzzers: Bug definition. (line 70)
* sidebar, Backslash Before Regular Characters: Escape Sequences.
(line 122)
-* sidebar, Escape Sequences for Metacharacters: Escape Sequences.
- (line 153)
-* sidebar, What About The Empty Regexp?: Regexp Operator Details.
- (line 149)
-* sidebar, Using \n in Bracket Expressions of Dynamic Regexps: Computed
Regexps.
- (line 58)
+* sidebar, Beware The Smoke and Mirrors!: Bitwise Functions. (line 127)
+* sidebar, Carriage-Return-Line-Feed Line Endings In CSV Files: Comma
Separated Fields.
+ (line 45)
* sidebar, Caveats When Using Regular Expressions for RS: gawk split records.
(line 50)
-* sidebar, RS = "\0" Is Not Portable: gawk split records. (line 75)
-* sidebar, Understanding $0: Changing Fields. (line 135)
-* sidebar, Carriage-ReturnâLine-Feed Line Endings In CSV Files: Comma
Separated Fields.
- (line 46)
* sidebar, Changing FS Does Not Affect the Fields: Full Line Fields.
(line 14)
+* sidebar, Changing NR and FNR: Auto-set. (line 414)
+* sidebar, Controlling Output Buffering with system(): I/O Functions.
+ (line 165)
+* sidebar, Escape Sequences for Metacharacters: Escape Sequences.
+ (line 153)
* sidebar, FS and IGNORECASE: Field Splitting Summary.
(line 41)
+* sidebar, Interactive Versus Noninteractive Buffering: I/O Functions.
+ (line 73)
+* sidebar, Matching the Null String: String Functions. (line 573)
+* sidebar, Operator Evaluation Order: Increment Ops. (line 58)
* sidebar, Piping into sh: Redirection. (line 134)
-* sidebar, A Constantâs Base Does Not Affect Its Value: Nondecimal-numbers.
- (line 63)
* sidebar, Pre-POSIX awk Used OFMT for String Conversion: Strings And Numbers.
(line 54)
-* sidebar, Syntactic Ambiguities Between /= and Regular Expressions:
Assignment Ops.
- (line 148)
-* sidebar, Operator Evaluation Order: Increment Ops. (line 58)
-* sidebar, Changing NR and FNR: Auto-set. (line 414)
-* sidebar, Matching the Null String: String Functions. (line 573)
-* sidebar, Interactive Versus Noninteractive Buffering: I/O Functions.
- (line 73)
-* sidebar, Controlling Output Buffering with system(): I/O Functions.
- (line 166)
-* sidebar, Beware The Smoke and Mirrors!: Bitwise Functions. (line 128)
+* sidebar, Quoting Shell Variables On The awk Command Line: Other Arguments.
+ (line 71)
+* sidebar, Recipe for a Programming Language: History. (line 6)
+* sidebar, Rounding Modes and Conversion: Setting the rounding mode.
+ (line 65)
+* sidebar, RS = "\0" Is Not Portable: gawk split records. (line 74)
* sidebar, So Why Does gawk Have BEGINFILE and ENDFILE?: Filetrans Function.
(line 83)
-* sidebar, Rounding Modes and Conversion: Setting the rounding mode.
- (line 66)
-* sidebar, A Note About Fuzzers: Bug definition. (line 70)
+* sidebar, Syntactic Ambiguities Between /= and Regular Expressions:
Assignment Ops.
+ (line 147)
+* sidebar, Understanding #!: Executable Scripts. (line 27)
+* sidebar, Understanding $0: Changing Fields. (line 135)
+* sidebar, Using \n in Bracket Expressions of Dynamic Regexps: Computed
Regexps.
+ (line 58)
+* sidebar, What About The Empty Regexp?: Regexp Operator Details.
+ (line 149)
* SIGHUP signal, for dynamic profiling: Profiling. (line 217)
* SIGINT signal (MS-Windows): Profiling. (line 220)
-* signals, USR1/SIGUSR1, for profiling: Profiling. (line 194)
* signals, HUP/SIGHUP, for profiling: Profiling. (line 217)
* signals, INT/SIGINT (MS-Windows): Profiling. (line 220)
* signals, QUIT/SIGQUIT (MS-Windows): Profiling. (line 220)
+* signals, USR1/SIGUSR1, for profiling: Profiling. (line 194)
* signature program: Signature Program. (line 6)
* SIGQUIT signal (MS-Windows): Profiling. (line 220)
* SIGUSR1 signal, for dynamic profiling: Profiling. (line 194)
@@ -39302,10 +39266,10 @@ Index
* sine: Numeric Functions. (line 74)
* single quote ('): One-shot. (line 15)
* single quote ('), in gawk command lines: Long. (line 35)
-* single quote ('), vs. apostrophe: Comments. (line 27)
* single quote ('), in shell commands: Quoting. (line 48)
+* single quote ('), vs. apostrophe: Comments. (line 27)
* single quote ('), with double quotes: Quoting. (line 73)
-* single records, treating files as: gawk split records. (line 104)
+* single records, treating files as: gawk split records. (line 102)
* single-character fields: Single Character Fields.
(line 6)
* single-precision: Computer Arithmetic. (line 61)
@@ -39325,37 +39289,37 @@ Index
* sort utility, coprocesses and: Two-way I/O. (line 66)
* sorting characters in different languages: Explaining gettext.
(line 94)
-* source code, mixing: Options. (line 120)
-* source code, gawk: Gawk Distribution. (line 6)
-* source code, Brian Kernighanâs awk: Other Versions. (line 13)
-* source code, mawk: Other Versions. (line 39)
* source code, awka: Other Versions. (line 64)
-* source code, pawk (profiling version of Brian Kernighanâs awk): Other
Versions.
- (line 82)
+* source code, awkcc: Other Versions. (line 167)
+* source code, AWKgo: Other Versions. (line 133)
+* source code, Brian Kernighan's awk: Other Versions. (line 13)
* source code, BusyBox Awk: Other Versions. (line 92)
-* source code, Solaris awk: Other Versions. (line 100)
-* source code, Illumos awk: Other Versions. (line 109)
+* source code, cppawk: Other Versions. (line 190)
+* source code, embeddable awk interpreter: Other Versions. (line 156)
* source code, frawk: Other Versions. (line 117)
+* source code, gawk: Gawk Distribution. (line 6)
* source code, goawk: Other Versions. (line 125)
-* source code, AWKgo: Other Versions. (line 133)
+* source code, Illumos awk: Other Versions. (line 109)
* source code, jawk: Other Versions. (line 140)
* source code, libmawk: Other Versions. (line 153)
-* source code, embeddable awk interpreter: Other Versions. (line 156)
+* source code, mawk: Other Versions. (line 39)
+* source code, mixing: Options. (line 120)
+* source code, pawk (profiling version of Brian Kernighan's awk): Other
Versions.
+ (line 82)
* source code, pawk (Python version): Other Versions. (line 161)
-* source code, awkcc: Other Versions. (line 167)
* source code, QSE awk: Other Versions. (line 174)
* source code, QuikTrim Awk: Other Versions. (line 178)
-* source code, cppawk: Other Versions. (line 190)
+* source code, Solaris awk: Other Versions. (line 100)
* source file, show in debugger: Debugger Info. (line 37)
* source files, search path for: Programs Exercises. (line 70)
-* sparse arrays: Array Intro. (line 76)
+* sparse arrays: Array Intro. (line 78)
* Spencer, Henry: Glossary. (line 16)
* Spengler, Egon: Gory Details. (line 6)
* split: String Functions. (line 336)
* split string into array: String Functions. (line 315)
* split utility: Split Program. (line 6)
-* split() function, array elements, deleting: Delete. (line 61)
* split.awk program: Split Program. (line 51)
+* split() function, array elements, deleting: Delete. (line 61)
* sprintf: OFMT. (line 15)
* sprintf <1>: String Functions. (line 413)
* sprintf() function, print/printf statements and: Round Function.
@@ -39377,63 +39341,63 @@ Index
* starting the debugger: Debugger Invocation. (line 6)
* stat() extension function: Extension Sample File Functions.
(line 18)
-* statements, multiple: Statements/Lines. (line 118)
-* statements, control, in actions: Statements. (line 6)
* statements, compound, control statements and: Statements. (line 10)
+* statements, control, in actions: Statements. (line 6)
+* statements, multiple: Statements/Lines. (line 118)
* step debugger command: Debugger Execution Control.
(line 68)
* stepi debugger command: Debugger Execution Control.
(line 75)
* stop automatic display, in debugger: Viewing And Changing Data.
(line 83)
+* STR_CHAIN_MAX environment variable: Other Environment Variables.
+ (line 91)
* stream editors: Full Line Fields. (line 22)
* stream editors <1>: Simple Sed. (line 6)
* strftime: Time Functions. (line 50)
-* string, constants, vs. regexp constants: Computed Regexps. (line 40)
* string, constants: Scalar Constants. (line 15)
-* string, operators: Concatenation. (line 9)
-* string, length: String Functions. (line 189)
-* string, regular expression match of: String Functions. (line 229)
+* string, constants, vs. regexp constants: Computed Regexps. (line 40)
* string, extraction (internationalization): String Extraction.
(line 6)
+* string, length: String Functions. (line 189)
+* string, operators: Concatenation. (line 9)
+* string, regular expression match of: String Functions. (line 229)
* string-manipulation functions: String Functions. (line 6)
* string-matching operators: Regexp Usage. (line 19)
* string-translation functions: I18N Functions. (line 6)
-* strings, empty: awk split records. (line 108)
-* strings, null: Regexp Field Splitting.
- (line 42)
-* strings, length limitations: Scalar Constants. (line 20)
* strings, continuation across lines: Scalar Constants. (line 53)
* strings, converting: Strings And Numbers. (line 6)
-* strings, numeric: Variable Typing. (line 67)
+* strings, converting <1>: Bitwise Functions. (line 109)
* strings, converting, numbers to: User-modified. (line 30)
* strings, converting, numbers to <1>: User-modified. (line 107)
-* strings, splitting, example: String Functions. (line 355)
* strings, converting letter case: String Functions. (line 552)
-* strings, converting <1>: Bitwise Functions. (line 110)
-* strings, merging arrays into: Join Function. (line 6)
-* strings, for localization: Programmer i18n. (line 13)
+* strings, empty: awk split records. (line 108)
* strings, extracting: String Extraction. (line 6)
+* strings, for localization: Programmer i18n. (line 13)
+* strings, length limitations: Scalar Constants. (line 20)
+* strings, merging arrays into: Join Function. (line 6)
+* strings, null: Regexp Field Splitting.
+ (line 42)
+* strings, numeric: Variable Typing. (line 67)
+* strings, splitting, example: String Functions. (line 355)
* strptime() extension function: Extension Sample Time.
(line 31)
* strtonum: String Functions. (line 420)
* strtonum() function (gawk), --non-decimal-data option and: Nondecimal Data.
(line 35)
-* STR_CHAIN_MAX environment variable: Other Environment Variables.
- (line 91)
* sub: Standard Regexp Constants.
(line 43)
* sub <1>: String Functions. (line 438)
* sub() function, arguments of: String Functions. (line 492)
* sub() function, escape processing: Gory Details. (line 6)
* subscript separators: User-modified. (line 148)
+* subscripts in arrays, multidimensional: Multidimensional. (line 10)
+* subscripts in arrays, multidimensional, scanning: Multiscanning.
+ (line 11)
* subscripts in arrays, numbers as: Numeric Array Subscripts.
(line 6)
* subscripts in arrays, uninitialized variables as: Uninitialized Subscripts.
(line 6)
-* subscripts in arrays, multidimensional: Multidimensional. (line 10)
-* subscripts in arrays, multidimensional, scanning: Multiscanning.
- (line 11)
* SUBSEP variable: User-modified. (line 148)
* SUBSEP variable, multidimensional arrays and: Multidimensional.
(line 16)
@@ -39445,32 +39409,32 @@ Index
* switch statement: Switch Statement. (line 6)
* SYMTAB array: Auto-set. (line 359)
* syntactic ambiguity: /= operator vs. /=.../ regexp constant: Assignment Ops.
- (line 150)
+ (line 149)
* system: I/O Functions. (line 105)
* systime: Time Functions. (line 67)
* t debugger command (alias for tbreak): Breakpoint Control. (line 90)
* tbreak debugger command: Breakpoint Control. (line 90)
* Tcl: Library Names. (line 58)
-* TCP/IP, support for: Special Network. (line 6)
* TCP/IP: TCP/IP Networking. (line 6)
+* TCP/IP, support for: Special Network. (line 6)
* tee utility: Tee Program. (line 6)
* tee.awk program: Tee Program. (line 26)
* temporary breakpoint: Breakpoint Control. (line 90)
* terminating records: awk split records. (line 118)
-* testbits.awk program: Bitwise Functions. (line 70)
+* testbits.awk program: Bitwise Functions. (line 69)
* testext extension: Extension Sample API Tests.
(line 6)
* Texinfo: Conventions. (line 6)
-* Texinfo, chapter beginnings in files: Regexp Operator Details.
- (line 18)
* Texinfo <1>: Library Functions. (line 33)
* Texinfo <2>: Dupword Program. (line 17)
-* Texinfo, extracting programs from source files: Extract Program.
- (line 6)
* Texinfo <3>: Extract Program. (line 12)
* Texinfo <4>: Distribution contents.
(line 89)
* Texinfo <5>: Adding Code. (line 113)
+* Texinfo, chapter beginnings in files: Regexp Operator Details.
+ (line 18)
+* Texinfo, extracting programs from source files: Extract Program.
+ (line 6)
* text, printing: Print. (line 22)
* text, printing, unduplicated lines of: Uniq Program. (line 6)
* TEXTDOMAIN variable: User-modified. (line 154)
@@ -39487,14 +39451,14 @@ Index
* tilde (~), ~ operator <4>: Comparison Operators.
(line 11)
* tilde (~), ~ operator <5>: Comparison Operators.
- (line 99)
+ (line 98)
* tilde (~), ~ operator <6>: Precedence. (line 79)
* tilde (~), ~ operator <7>: Expression Patterns. (line 24)
-* time, retrieving: Time Functions. (line 17)
-* time, managing: Getlocaltime Function.
- (line 6)
* time, alarm clock example program: Alarm Program. (line 11)
* time, localization and: Explaining gettext. (line 112)
+* time, managing: Getlocaltime Function.
+ (line 6)
+* time, retrieving: Time Functions. (line 17)
* time functions: Time Functions. (line 6)
* timeout, reading input: Read Timeout. (line 6)
* timestamps: Time Functions. (line 6)
@@ -39502,8 +39466,8 @@ Index
* timestamps, converting dates to: Time Functions. (line 77)
* timestamps, formatted: Getlocaltime Function.
(line 6)
-* tocsv() user-defined function: To CSV Function. (line 21)
* tocsv_rec() user-defined function: To CSV Function. (line 54)
+* tocsv() user-defined function: To CSV Function. (line 21)
* tolower: String Functions. (line 553)
* toupper: String Functions. (line 559)
* tr utility: Translate Program. (line 6)
@@ -39513,39 +39477,39 @@ Index
* traceback, display in debugger: Execution Stack. (line 13)
* translate string: I18N Functions. (line 21)
* translate.awk program: Translate Program. (line 55)
-* treating files, as single records: gawk split records. (line 104)
-* troubleshooting, typographical errors, global variables: Options.
- (line 102)
+* treating files, as single records: gawk split records. (line 102)
* troubleshooting, --non-decimal-data option: Options. (line 261)
+* troubleshooting, == operator: Comparison Operators.
+ (line 37)
+* troubleshooting, awk uses FS not IFS: Field Separators. (line 30)
* troubleshooting, backslash before nonspecial character: Escape Sequences.
(line 124)
-* troubleshooting, regexp constants vs. string constants: Computed Regexps.
- (line 40)
-* troubleshooting, awk uses FS not IFS: Field Separators. (line 30)
+* troubleshooting, division: Arithmetic Ops. (line 44)
* troubleshooting, fatal errors, field widths, specifying: Fixed width data.
(line 17)
-* troubleshooting, print statement, omitting commas: Print Examples.
- (line 30)
* troubleshooting, fatal errors, printf format strings: Format Modifiers.
(line 157)
-* troubleshooting, printing: Redirection. (line 112)
-* troubleshooting, quotes with file names: Special FD. (line 62)
-* troubleshooting, division: Arithmetic Ops. (line 44)
-* troubleshooting, string concatenation: Concatenation. (line 27)
-* troubleshooting, == operator: Comparison Operators.
- (line 38)
+* troubleshooting, fflush() function: I/O Functions. (line 62)
* troubleshooting, function call syntax: Function Calls. (line 30)
+* troubleshooting, gawk: Compatibility Mode. (line 6)
+* troubleshooting, gawk, bug reports: Bugs. (line 9)
* troubleshooting, gawk, fatal errors, function arguments: Calling Built-in.
(line 16)
-* troubleshooting, match() function: String Functions. (line 310)
+* troubleshooting, getline command: File Checking. (line 25)
* troubleshooting, gsub()/sub() functions: String Functions. (line 502)
+* troubleshooting, match() function: String Functions. (line 310)
+* troubleshooting, print statement, omitting commas: Print Examples.
+ (line 30)
+* troubleshooting, printing: Redirection. (line 112)
+* troubleshooting, quotes with file names: Special FD. (line 62)
+* troubleshooting, readable data files: File Checking. (line 6)
+* troubleshooting, regexp constants vs. string constants: Computed Regexps.
+ (line 40)
+* troubleshooting, string concatenation: Concatenation. (line 27)
* troubleshooting, substr() function: String Functions. (line 529)
-* troubleshooting, fflush() function: I/O Functions. (line 62)
* troubleshooting, system() function: I/O Functions. (line 127)
-* troubleshooting, readable data files: File Checking. (line 6)
-* troubleshooting, getline command: File Checking. (line 25)
-* troubleshooting, gawk, bug reports: Bugs. (line 9)
-* troubleshooting, gawk: Compatibility Mode. (line 6)
+* troubleshooting, typographical errors, global variables: Options.
+ (line 102)
* true, logical: Truth Values. (line 6)
* Trueman, David: History. (line 34)
* Trueman, David <1>: Acknowledgments. (line 47)
@@ -39562,9 +39526,9 @@ Index
* unassigned array elements: Reference to Elements.
(line 18)
* undefined functions: Function Caveats. (line 6)
+* underscore (_), C macro: Explaining gettext. (line 71)
* underscore (_), in names of private variables: Library Names.
(line 29)
-* underscore (_), C macro: Explaining gettext. (line 71)
* underscore (_), translatable strings: Programmer i18n. (line 69)
* undisplay debugger command: Viewing And Changing Data.
(line 83)
@@ -39576,13 +39540,13 @@ Index
(line 6)
* uniq utility: Uniq Program. (line 6)
* uniq.awk program: Uniq Program. (line 51)
-* Unix, awk scripts and: Executable Scripts. (line 6)
* Unix: Glossary. (line 747)
+* Unix, awk scripts and: Executable Scripts. (line 6)
* Unix awk, backslashes in escape sequences: Escape Sequences.
(line 136)
+* Unix awk, close() function and: Close Return Value. (line 6)
* Unix awk, password files, field separators and: Command Line Field Separator.
(line 62)
-* Unix awk, close() function and: Close Return Value. (line 6)
* unsigned integers: Computer Arithmetic. (line 41)
* until debugger command: Debugger Execution Control.
(line 82)
@@ -39591,57 +39555,58 @@ Index
* up debugger command: Execution Stack. (line 36)
* uppercase names, namespace for: Default Namespace. (line 10)
* user database, reading: Passwd Functions. (line 6)
-* user-defined, variables: Variables. (line 6)
-* user-defined, function, bits2str(): Bitwise Functions. (line 70)
-* user-defined, functions: User-defined. (line 6)
-* user-defined, function, rev(): Function Example. (line 54)
-* user-defined, function, ctime(): Function Example. (line 74)
+* user-defined, function, _gr_init(): Group Functions. (line 83)
+* user-defined, function, _ord_init(): Ordinal Functions. (line 16)
+* user-defined, function, _pw_init(): Passwd Functions. (line 105)
* user-defined, function, assert(): Assert Function. (line 28)
-* user-defined, function, round(): Round Function. (line 16)
+* user-defined, function, beginfile(): Filetrans Function. (line 62)
+* user-defined, function, bits2str(): Bitwise Functions. (line 69)
+* user-defined, function, chr(): Ordinal Functions. (line 16)
* user-defined, function, cliff_rand(): Cliff Random Function.
(line 12)
-* user-defined, function, ord(): Ordinal Functions. (line 16)
-* user-defined, function, chr(): Ordinal Functions. (line 16)
-* user-defined, function, _ord_init(): Ordinal Functions. (line 16)
-* user-defined, function, join(): Join Function. (line 18)
+* user-defined, function, ctime(): Function Example. (line 74)
+* user-defined, function, endfile(): Filetrans Function. (line 62)
+* user-defined, function, endgrent(): Group Functions. (line 214)
+* user-defined, function, endpwent(): Passwd Functions. (line 210)
+* user-defined, function, getgrent(): Group Functions. (line 6)
+* user-defined, function, getgrent() <1>: Group Functions. (line 203)
+* user-defined, function, getgrgid(): Group Functions. (line 185)
+* user-defined, function, getgrnam(): Group Functions. (line 176)
+* user-defined, function, getgruser(): Group Functions. (line 194)
* user-defined, function, getlocaltime(): Getlocaltime Function.
(line 16)
-* user-defined, function, readfile(): Readfile Function. (line 30)
-* user-defined, function, isnumeric(): Isnumeric Function. (line 11)
-* user-defined, function, beginfile(): Filetrans Function. (line 62)
-* user-defined, function, endfile(): Filetrans Function. (line 62)
-* user-defined, function, rewind(): Rewind Function. (line 15)
* user-defined, function, getopt(): Getopt Function. (line 117)
* user-defined, function, getopt() <1>: Getopt Function. (line 144)
* user-defined, function, getpwent(): Passwd Functions. (line 16)
-* user-defined, function, _pw_init(): Passwd Functions. (line 105)
+* user-defined, function, getpwent() <1>: Passwd Functions. (line 199)
* user-defined, function, getpwnam(): Passwd Functions. (line 179)
* user-defined, function, getpwuid(): Passwd Functions. (line 189)
-* user-defined, function, getpwent() <1>: Passwd Functions. (line 199)
-* user-defined, function, endpwent(): Passwd Functions. (line 210)
-* user-defined, function, getgrent(): Group Functions. (line 6)
-* user-defined, function, _gr_init(): Group Functions. (line 83)
-* user-defined, function, getgrnam(): Group Functions. (line 176)
-* user-defined, function, getgrgid(): Group Functions. (line 185)
-* user-defined, function, getgruser(): Group Functions. (line 194)
-* user-defined, function, getgrent() <1>: Group Functions. (line 203)
-* user-defined, function, endgrent(): Group Functions. (line 214)
+* user-defined, function, isnumeric(): Isnumeric Function. (line 11)
+* user-defined, function, join(): Join Function. (line 18)
+* user-defined, function, ord(): Ordinal Functions. (line 16)
+* user-defined, function, readfile(): Readfile Function. (line 30)
+* user-defined, function, rev(): Function Example. (line 54)
+* user-defined, function, rewind(): Rewind Function. (line 15)
+* user-defined, function, round(): Round Function. (line 16)
* user-defined, function, walk_array(): Walking Arrays. (line 14)
+* user-defined, functions: User-defined. (line 6)
* user-defined, functions, counts, in a profile: Profiling. (line 137)
+* user-defined, variables: Variables. (line 6)
* user-modifiable variables: User-modified. (line 6)
-* users, information about, retrieving: Passwd Functions. (line 16)
* users, information about, printing: Id Program. (line 6)
+* users, information about, retrieving: Passwd Functions. (line 16)
* USR1 signal, for dynamic profiling: Profiling. (line 194)
+* values, numeric: Basic Data Typing. (line 13)
* values, regexp: Strong Regexp Constants.
(line 24)
-* values, numeric: Basic Data Typing. (line 13)
* values, string: Basic Data Typing. (line 13)
* variable assignments and input files: Other Arguments. (line 34)
* variable type, typeof() function (gawk): Type Functions. (line 14)
* variables: Other Features. (line 6)
-* variables, setting: Options. (line 36)
-* variables, predefined, -v option, setting with: Options. (line 44)
-* variables, global, printing list of: Options. (line 97)
+* variables <1>: Basic Data Typing. (line 6)
+* variables, assigning on command line: Assignment Options. (line 6)
+* variables, built-in: Using Variables. (line 23)
+* variables, flag: Boolean Ops. (line 69)
* variables, getline command into, using: Getline/Variable. (line 6)
* variables, getline command into, using <1>: Getline/Variable/File.
(line 6)
@@ -39649,36 +39614,35 @@ Index
(line 6)
* variables, getline command into, using <3>: Getline/Variable/Coprocess.
(line 6)
-* variables, user-defined: Variables. (line 6)
-* variables, built-in: Using Variables. (line 23)
+* variables, global, for library functions: Library Names. (line 11)
+* variables, global, printing list of: Options. (line 97)
* variables, initializing: Using Variables. (line 23)
-* variables, assigning on command line: Assignment Options. (line 6)
+* variables, local to a function: Variable Scope. (line 6)
+* variables, predefined: Built-in Variables. (line 6)
+* variables, predefined, -v option, setting with: Options. (line 44)
+* variables, predefined, conveying information: Auto-set. (line 6)
+* variables, private: Library Names. (line 11)
+* variables, setting: Options. (line 36)
+* variables, shadowing: Definition Syntax. (line 77)
* variables, types of: Assignment Ops. (line 39)
* variables, types of, comparison expressions and: Typing and Comparison.
(line 9)
-* variables, flag: Boolean Ops. (line 69)
-* variables, predefined: Built-in Variables. (line 6)
-* variables, predefined, conveying information: Auto-set. (line 6)
* variables, uninitialized, as array subscripts: Uninitialized Subscripts.
(line 6)
-* variables, shadowing: Definition Syntax. (line 77)
-* variables, local to a function: Variable Scope. (line 6)
-* variables, global, for library functions: Library Names. (line 11)
-* variables, private: Library Names. (line 11)
-* variables <1>: Basic Data Typing. (line 6)
+* variables, user-defined: Variables. (line 6)
* version of, gawk: Auto-set. (line 262)
+* version of, gawk extension API: Auto-set. (line 287)
* version of, GNU MP library: Auto-set. (line 270)
* version of, GNU MPFR library: Auto-set. (line 272)
-* version of, gawk extension API: Auto-set. (line 287)
* vertical bar (|): Regexp Operator Details.
(line 66)
* vertical bar (|), | operator (I/O): Getline/Pipe. (line 10)
-* vertical bar (|), |& operator (I/O): Getline/Coprocess. (line 6)
-* vertical bar (|), || operator: Boolean Ops. (line 59)
* vertical bar (|), | operator (I/O) <1>: Precedence. (line 64)
+* vertical bar (|), |& operator (I/O): Getline/Coprocess. (line 6)
* vertical bar (|), |& operator (I/O) <1>: Precedence. (line 64)
-* vertical bar (|), || operator <1>: Precedence. (line 88)
* vertical bar (|), |& operator (I/O) <2>: Two-way I/O. (line 27)
+* vertical bar (|), || operator: Boolean Ops. (line 59)
+* vertical bar (|), || operator <1>: Precedence. (line 88)
* Vinschen, Corinna: Acknowledgments. (line 60)
* w debugger command (alias for watch): Viewing And Changing Data.
(line 70)
@@ -39702,22 +39666,22 @@ Index
* Weinberger, Peter <1>: Contributors. (line 12)
* where debugger command (alias for backtrace): Execution Stack.
(line 13)
-* while statement, use of regexps in: Regexp Usage. (line 19)
* while statement: While Statement. (line 6)
-* whitespace, newlines as: Options. (line 314)
-* whitespace, definition of: Fields. (line 6)
+* while statement, use of regexps in: Regexp Usage. (line 19)
* whitespace, as field separators: Default Field Splitting.
(line 6)
+* whitespace, definition of: Fields. (line 6)
* whitespace, functions, calling: Calling Built-in. (line 10)
+* whitespace, newlines as: Options. (line 314)
* Williams, Kent: Contributors. (line 35)
* Woehlke, Matthew: Contributors. (line 82)
* Woods, John: Contributors. (line 28)
* word boundaries, matching: GNU Regexp Operators.
(line 38)
-* word, regexp definition of: GNU Regexp Operators.
- (line 6)
* word-boundary operator (gawk): GNU Regexp Operators.
(line 65)
+* word, regexp definition of: GNU Regexp Operators.
+ (line 6)
* wordfreq.awk program: Word Sorting. (line 56)
* words, counting: Wc Program. (line 6)
* words, duplicate, searching for: Dupword Program. (line 6)
@@ -39727,7 +39691,7 @@ Index
* writeall() extension function: Extension Sample Read write array.
(line 24)
* xgettext utility: String Extraction. (line 13)
-* xor: Bitwise Functions. (line 58)
+* xor: Bitwise Functions. (line 57)
* XOR bitwise operation: Bitwise Functions. (line 6)
* Yawitz, Efraim: Contributors. (line 134)
* Zaretskii, Eli: Acknowledgments. (line 60)
@@ -39739,626 +39703,626 @@ Index
Tag Table:
-Node: Top1229
-Node: Foreword346932
-Node: Foreword451532
-Node: Preface53081
-Ref: Preface-Footnote-156073
-Ref: Preface-Footnote-256182
-Ref: Preface-Footnote-356416
-Node: History56562
-Node: Names59180
-Ref: Names-Footnote-160343
-Node: This Manual60506
-Ref: This Manual-Footnote-167456
-Node: Conventions67568
-Node: Manual History70046
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-Ref: Manual History-Footnote-273130
-Node: How To Contribute73208
-Node: Acknowledgments74158
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-Node: Running gawk81683
-Node: One-shot82901
-Node: Read Terminal84204
-Node: Long86264
-Node: Executable Scripts87845
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-Node: Comments90727
-Node: Quoting93265
-Node: DOS Quoting98914
-Node: Sample Data Files101000
-Node: Very Simple103637
-Node: Two Rules109916
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-Node: When121091
-Ref: When-Footnote-1122897
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-Node: Command Line125488
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-Ref: Options-Footnote-2145951
-Node: Other Arguments145976
-Node: Naming Standard Input150153
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-Node: AWKPATH Variable151997
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-Ref: Regexp Operator Details-Footnote-1192742
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-Node: Bracket Expressions195270
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-Ref: gawk split records-Footnote-1228876
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-Ref: Nonconstant Fields-Footnote-1234268
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-Node: Regexp Field Splitting244808
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-Ref: table-csv-examples251134
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-Ref: Full Line Fields-Footnote-1258409
-Ref: Full Line Fields-Footnote-2258455
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-Node: Fields with fixed data267017
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-Ref: Splitting By Content-Footnote-1272919
-Node: More CSV273082
-Node: FS versus FPAT274735
-Node: Testing field creation275944
-Node: Multiple Line277722
-Node: Getline284204
-Node: Plain Getline286790
-Node: Getline/Variable289440
-Node: Getline/File290637
-Node: Getline/Variable/File292085
-Ref: Getline/Variable/File-Footnote-1293730
-Node: Getline/Pipe293826
-Node: Getline/Variable/Pipe296639
-Node: Getline/Coprocess297822
-Node: Getline/Variable/Coprocess299145
-Node: Getline Notes299911
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-Ref: Read Timeout-Footnote-1308185
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-Node: Command-line directories309510
-Node: Input Summary310448
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-Node: Printing314268
-Node: Print316211
-Node: Print Examples317717
-Node: Output Separators320570
-Node: OFMT322681
-Node: Printf324396
-Node: Basic Printf325201
-Node: Control Letters326837
-Node: Format Modifiers332306
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-Node: Redirection341137
-Node: Special FD348211
-Ref: Special FD-Footnote-1351501
-Node: Special Files351587
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-Node: Close Files And Pipes355152
-Ref: Close Files And Pipes-Footnote-1361288
-Node: Close Return Value361444
-Ref: table-close-pipe-return-values362719
-Ref: Close Return Value-Footnote-1363553
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-Ref: table-locale-affects398481
-Node: All Operators399124
-Node: Arithmetic Ops399765
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-Ref: Concatenation-Footnote-1405545
-Node: Assignment Ops405668
-Ref: table-assign-ops410807
-Node: Increment Ops412189
-Node: Truth Values and Conditions415788
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-Node: Typing and Comparison418005
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-Ref: Variable Typing-Footnote-1425503
-Ref: Variable Typing-Footnote-2425583
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-Node: I/O And BEGIN/END464846
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-Ref: figure-array-elements539583
-Ref: Array Intro-Footnote-1542452
-Node: Reference to Elements542584
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-Node: Array Example545601
-Node: Scanning an Array547570
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-Node: Uninitialized Subscripts559911
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-Node: Arrays Summary574238
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-Node: Built-in577487
-Node: Calling Built-in578676
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-Ref: Numeric Functions-Footnote-1585486
-Ref: Numeric Functions-Footnote-2586170
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-Ref: String Functions-Footnote-2613108
-Ref: String Functions-Footnote-3613368
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-Ref: I/O Functions-Footnote-1630259
-Ref: I/O Functions-Footnote-2630407
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-Ref: Time Functions-Footnote-1641683
-Ref: Time Functions-Footnote-2641759
-Ref: Time Functions-Footnote-3641921
-Ref: Time Functions-Footnote-4642032
-Ref: Time Functions-Footnote-5642150
-Ref: Time Functions-Footnote-6642385
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-Ref: Bitwise Functions-Footnote-2649702
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-Node: User-defined655235
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-Ref: Definition Syntax-Footnote-1661883
-Node: Function Example661960
-Ref: Function Example-Footnote-1664939
-Node: Function Calling664961
-Node: Calling A Function665555
-Node: Variable Scope666525
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-Ref: Library Names-Footnote-2701800
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-Ref: Ordinal Functions-Footnote-1715420
-Ref: Ordinal Functions-Footnote-2715672
-Node: Join Function715886
-Ref: Join Function-Footnote-1717689
-Node: Getlocaltime Function717893
-Node: Readfile Function721667
-Node: Shell Quoting723696
-Node: Isnumeric Function725152
-Node: To CSV Function726588
-Node: Data File Management728664
-Node: Filetrans Function729296
-Node: Rewind Function733590
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-Ref: File Checking-Footnote-1736941
-Node: Empty Files737148
-Node: Ignoring Assigns739215
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-Ref: Getopt Function-Footnote-1756623
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-Ref: Passwd Functions-Footnote-1766017
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-Node: Running Examples780197
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-Ref: Split Program-Footnote-1822328
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-Node: Using extensions835286
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-Ref: Two-way I/O-Footnote-1931280
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-Node: Debugger Invocation992983
-Node: Finding The Bug994612
-Node: List of Debugger Commands1001298
-Node: Breakpoint Control1002675
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-Node: Namespaces1029847
-Node: Global Namespace1030974
-Node: Qualified Names1032419
-Node: Default Namespace1033454
-Node: Changing The Namespace1034229
-Node: Naming Rules1035923
-Node: Internal Name Management1037838
-Node: Namespace Example1038908
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-Node: Namespace Summary1042948
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-Ref: table-numeric-ranges1049797
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-Ref: Computer Arithmetic-Footnote-11050954
-Node: Math Definitions1051013
-Ref: table-ieee-formats1054058
-Node: MPFR features1054632
-Node: MPFR On Parole1055085
-Ref: MPFR On Parole-Footnote-11055929
-Node: MPFR Intro1056088
-Node: FP Math Caution1057778
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-Node: Inexactness of computations1059229
-Node: Inexact representation1060260
-Node: Comparing FP Values1061643
-Node: Errors accumulate1062901
-Node: Strange values1064368
-Ref: Strange values-Footnote-11067034
-Node: Getting Accuracy1067139
-Node: Try To Round1069876
-Node: Setting precision1070783
-Ref: table-predefined-precision-strings1071488
-Node: Setting the rounding mode1073373
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-Ref: Setting the rounding mode-Footnote-11077813
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-Node: Floating point summary1087756
-Node: Dynamic Extensions1090020
-Node: Extension Intro1091619
-Node: Plugin License1092927
-Node: Extension Mechanism Outline1093740
-Ref: figure-load-extension1094191
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-Node: Extension API Description1099010
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-Ref: table-api-std-headers1102637
-Node: General Data Types1107101
-Ref: General Data Types-Footnote-11116269
-Node: Memory Allocation Functions1116584
-Ref: Memory Allocation Functions-Footnote-11121309
-Node: Constructor Functions1121408
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-Node: Registration Functions1126874
-Node: Extension Functions1127578
-Node: Exit Callback Functions1133154
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-Node: Output Wrappers1149812
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-Ref: Printing Messages-Footnote-11158235
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-Ref: table-value-types-returned1159942
-Node: Accessing Parameters1161051
-Node: Symbol Table Access1162335
-Node: Symbol table by name1162851
-Ref: Symbol table by name-Footnote-11166062
-Node: Symbol table by cookie1166194
-Ref: Symbol table by cookie-Footnote-11170475
-Node: Cached values1170539
-Ref: Cached values-Footnote-11174183
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-Ref: Array Manipulation-Footnote-11175443
-Node: Array Data Types1175480
-Ref: Array Data Types-Footnote-11178302
-Node: Array Functions1178402
-Node: Flattening Arrays1183431
-Node: Creating Arrays1190483
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-Node: Extension API Variables1198354
-Node: Extension Versioning1199079
-Ref: gawk-api-version1199516
-Node: Extension GMP/MPFR Versioning1201304
-Node: Extension API Informational Variables1203010
-Node: Extension API Boilerplate1204263
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-Ref: Internal File Ops-Footnote-11227314
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-Ref: Using Internal File Ops-Footnote-11229893
-Node: Extension Samples1230171
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-Node: Extension Sample Fork1241473
-Node: Extension Sample Inplace1242749
-Node: Extension Sample Ord1246421
-Node: Extension Sample Readdir1247297
-Ref: table-readdir-file-types1248086
-Node: Extension Sample Revout1249447
-Node: Extension Sample Rev2way1250044
-Node: Extension Sample Read write array1250796
-Node: Extension Sample Readfile1254070
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-Node: Feature History1280492
-Node: Common Extensions1300308
-Node: Ranges and Locales1301785
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-Ref: Ranges and Locales-Footnote-21306613
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-Node: Contributors1307075
-Node: History summary1313280
-Node: Installation1314726
-Node: Gawk Distribution1315690
-Node: Getting1316182
-Node: Extracting1317181
-Node: Distribution contents1318893
-Node: Unix Installation1326973
-Node: Quick Installation1327795
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-Node: Shell Startup Files1331047
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-Node: Configuration Philosophy1334591
-Node: Compiling from Git1337093
-Node: Building the Documentation1337652
-Node: Non-Unix Installation1339064
-Node: PC Installation1339540
-Node: PC Binary Installation1340413
-Node: PC Compiling1341318
-Node: PC Using1342496
-Node: Cygwin1346224
-Node: MSYS1347480
-Node: OpenVMS Installation1348112
-Node: OpenVMS Compilation1348793
-Ref: OpenVMS Compilation-Footnote-11350276
-Node: OpenVMS Dynamic Extensions1350338
-Node: OpenVMS Installation Details1351974
-Node: OpenVMS Running1354409
-Node: OpenVMS GNV1358546
-Node: Bugs1359301
-Node: Bug definition1360225
-Node: Bug address1363876
-Node: Usenet1367467
-Node: Performance bugs1368698
-Node: Asking for help1371716
-Node: Maintainers1373707
-Node: Other Versions1374734
-Node: Installation summary1384077
-Node: Notes1385461
-Node: Compatibility Mode1386271
-Node: Additions1387093
-Node: Accessing The Source1388038
-Node: Adding Code1389573
-Node: New Ports1396709
-Node: Derived Files1401219
-Ref: Derived Files-Footnote-11407066
-Ref: Derived Files-Footnote-21407101
-Ref: Derived Files-Footnote-31407718
-Node: Future Extensions1407832
-Node: Implementation Limitations1408504
-Node: Extension Design1409746
-Node: Old Extension Problems1410910
-Ref: Old Extension Problems-Footnote-11412486
-Node: Extension New Mechanism Goals1412547
-Ref: Extension New Mechanism Goals-Footnote-11416043
-Node: Extension Other Design Decisions1416244
-Node: Extension Future Growth1418443
-Node: Notes summary1419067
-Node: Basic Concepts1420280
-Node: Basic High Level1420965
-Ref: figure-general-flow1421247
-Ref: figure-process-flow1421954
-Ref: Basic High Level-Footnote-11425355
-Node: Basic Data Typing1425544
-Node: Glossary1428962
-Node: Copying1462084
-Node: GNU Free Documentation License1499845
-Node: Index1525168
+Node: Top1203
+Node: Foreword346844
+Node: Foreword451418
+Node: Preface52962
+Ref: Preface-Footnote-155948
+Ref: Preface-Footnote-256057
+Ref: Preface-Footnote-356291
+Node: History56437
+Node: Names59051
+Ref: Names-Footnote-160205
+Node: This Manual60368
+Ref: This Manual-Footnote-167297
+Node: Conventions67405
+Node: Manual History69834
+Ref: Manual History-Footnote-172859
+Ref: Manual History-Footnote-272900
+Node: How To Contribute72974
+Node: Acknowledgments73920
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+Ref: Ordinal Functions-Footnote-2713983
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+Node: Uniq Program823521
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+Ref: Igawk Program-Footnote-2889149
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+Node: Computer Arithmetic1043420
+Ref: table-numeric-ranges1047228
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+Ref: table-ieee-formats1051472
+Node: MPFR features1052045
+Node: MPFR On Parole1052498
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+Node: FP Math Caution1055182
+Ref: FP Math Caution-Footnote-11056254
+Node: Inexactness of computations1056627
+Node: Inexact representation1057658
+Node: Comparing FP Values1059039
+Node: Errors accumulate1060297
+Node: Strange values1061762
+Ref: Strange values-Footnote-11064416
+Node: Getting Accuracy1064521
+Node: Try To Round1067258
+Node: Setting precision1068165
+Ref: table-predefined-precision-strings1068870
+Node: Setting the rounding mode1070754
+Ref: table-gawk-rounding-modes1071136
+Ref: Setting the rounding mode-Footnote-11075188
+Node: Arbitrary Precision Integers1075371
+Ref: Arbitrary Precision Integers-Footnote-11078581
+Node: Checking for MPFR1078734
+Node: POSIX Floating Point Problems1080224
+Ref: POSIX Floating Point Problems-Footnote-11085044
+Node: Floating point summary1085082
+Node: Dynamic Extensions1087338
+Node: Extension Intro1088935
+Node: Plugin License1090237
+Node: Extension Mechanism Outline1091050
+Ref: figure-load-extension1091501
+Ref: figure-register-new-function1093079
+Ref: figure-call-new-function1094188
+Node: Extension API Description1096303
+Node: Extension API Functions Introduction1098032
+Ref: table-api-std-headers1099926
+Node: General Data Types1104367
+Ref: General Data Types-Footnote-11113513
+Node: Memory Allocation Functions1113816
+Ref: Memory Allocation Functions-Footnote-11118533
+Node: Constructor Functions1118632
+Node: API Ownership of MPFR and GMP Values1122533
+Node: Registration Functions1124086
+Node: Extension Functions1124790
+Node: Exit Callback Functions1130364
+Node: Extension Version String1131678
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+Node: Printing Messages1154187
+Ref: Printing Messages-Footnote-11155398
+Node: Updating ERRNO1155551
+Node: Requesting Values1156350
+Ref: table-value-types-returned1157103
+Node: Accessing Parameters1158211
+Node: Symbol Table Access1159492
+Node: Symbol table by name1160004
+Ref: Symbol table by name-Footnote-11163205
+Node: Symbol table by cookie1163337
+Ref: Symbol table by cookie-Footnote-11167606
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+Node: Flattening Arrays1180538
+Node: Creating Arrays1187586
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+Node: Extension API Variables1195445
+Node: Extension Versioning1196168
+Ref: gawk-api-version1196597
+Node: Extension GMP/MPFR Versioning1198384
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+Node: Changes from API V11205471
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+Node: Extension Example1207678
+Node: Internal File Description1208500
+Node: Internal File Ops1212792
+Ref: Internal File Ops-Footnote-11224342
+Node: Using Internal File Ops1224490
+Ref: Using Internal File Ops-Footnote-11226921
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+Node: Extension Sample File Functions1228768
+Node: Extension Sample Fnmatch1236893
+Node: Extension Sample Fork1238488
+Node: Extension Sample Inplace1239764
+Node: Extension Sample Ord1243430
+Node: Extension Sample Readdir1244306
+Ref: table-readdir-file-types1245095
+Node: Extension Sample Revout1246451
+Node: Extension Sample Rev2way1247048
+Node: Extension Sample Read write array1247800
+Node: Extension Sample Readfile1251074
+Node: Extension Sample Time1252205
+Node: Extension Sample API Tests1254493
+Node: gawkextlib1255001
+Node: Extension summary1258033
+Node: Extension Exercises1261881
+Node: Language History1263151
+Node: V7/SVR3.11264863
+Node: SVR41267213
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+Node: BTL1270170
+Node: POSIX/GNU1270937
+Node: Feature History1277466
+Node: Common Extensions1297268
+Node: Ranges and Locales1298743
+Ref: Ranges and Locales-Footnote-11303528
+Ref: Ranges and Locales-Footnote-21303555
+Ref: Ranges and Locales-Footnote-31303790
+Node: Contributors1304013
+Node: History summary1310204
+Node: Installation1311646
+Node: Gawk Distribution1312610
+Node: Getting1313102
+Node: Extracting1314101
+Node: Distribution contents1315807
+Node: Unix Installation1323881
+Node: Quick Installation1324701
+Node: Compiling with MPFR1327241
+Node: Shell Startup Files1327947
+Node: Additional Configuration Options1329104
+Node: Configuration Philosophy1331487
+Node: Compiling from Git1333987
+Node: Building the Documentation1334546
+Node: Non-Unix Installation1335958
+Node: PC Installation1336434
+Node: PC Binary Installation1337303
+Node: PC Compiling1338196
+Node: PC Using1339374
+Node: Cygwin1343090
+Node: MSYS1344342
+Node: OpenVMS Installation1344968
+Node: OpenVMS Compilation1345649
+Ref: OpenVMS Compilation-Footnote-11347132
+Node: OpenVMS Dynamic Extensions1347190
+Node: OpenVMS Installation Details1348826
+Node: OpenVMS Running1351257
+Node: OpenVMS GNV1355394
+Node: Bugs1356149
+Node: Bug definition1357069
+Node: Bug address1360670
+Node: Usenet1364239
+Node: Performance bugs1365452
+Node: Asking for help1368468
+Node: Maintainers1370455
+Node: Other Versions1371482
+Node: Installation summary1380781
+Node: Notes1382163
+Node: Compatibility Mode1382973
+Node: Additions1383795
+Node: Accessing The Source1384740
+Node: Adding Code1386271
+Node: New Ports1393382
+Node: Derived Files1397885
+Ref: Derived Files-Footnote-11403696
+Ref: Derived Files-Footnote-21403731
+Ref: Derived Files-Footnote-31404342
+Node: Future Extensions1404456
+Node: Implementation Limitations1405126
+Node: Extension Design1406368
+Node: Old Extension Problems1407528
+Ref: Old Extension Problems-Footnote-11409100
+Node: Extension New Mechanism Goals1409161
+Ref: Extension New Mechanism Goals-Footnote-11412631
+Node: Extension Other Design Decisions1412832
+Node: Extension Future Growth1415029
+Node: Notes summary1415649
+Node: Basic Concepts1416859
+Node: Basic High Level1417544
+Ref: figure-general-flow1417826
+Ref: figure-process-flow1418528
+Ref: Basic High Level-Footnote-11421898
+Node: Basic Data Typing1422087
+Node: Glossary1425495
+Node: Copying1458374
+Node: GNU Free Documentation License1495932
+Node: Index1521055
End Tag Table
diff --git a/doc/gawk.texi b/doc/gawk.texi
index f0714c90..eaf88091 100644
--- a/doc/gawk.texi
+++ b/doc/gawk.texi
@@ -1,8 +1,3 @@
-% ****************************************************
-% * DO NOT MODIFY THIS FILE!!!! *
-% * It was generated from gawktexi.in by sidebar.awk *
-% * Edit gawktexi.in instead. *
-% ****************************************************
\input texinfo @c -*-texinfo-*-
@c vim: filetype=texinfo
@c %**start of header (This is for running Texinfo on a region.)
@@ -1488,37 +1483,7 @@ has been removed.}
@cindex recipe for a programming language
@cindex programming language, recipe for
@cindex sidebar @subentry Recipe for a Programming Language
-@ifdocbook
-@docbook
-<sidebar><title>Recipe for a Programming Language</title>
-@end docbook
-
-
-@multitable {2 parts} {1 part @code{egrep}} {1 part @code{snobol}}
-@item @tab 1 part @code{egrep} @tab 1 part @code{snobol}
-@item @tab 2 parts @code{ed} @tab 3 parts C
-@end multitable
-
-Blend all parts well using @code{lex} and @code{yacc}.
-Document minimally and release.
-
-After eight years, add another part @code{egrep} and two
-more parts C. Document very well and release.
-
-After 35 more years, add Unicode and CSV support, sprinkle lightly with
-a few choice features from @command{gawk}, document very well again,
-and release.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Recipe for a Programming Language}
-
-
+@cartouche Recipe for a Programming Language
@multitable {2 parts} {1 part @code{egrep}} {1 part @code{snobol}}
@item @tab 1 part @code{egrep} @tab 1 part @code{snobol}
@@ -1535,7 +1500,6 @@ After 35 more years, add Unicode and CSV support,
sprinkle lightly with
a few choice features from @command{gawk}, document very well again,
and release.
@end cartouche
-@end ifnotdocbook
@cindex Aho, Alfred
@cindex Weinberger, Peter
@@ -2716,62 +2680,7 @@ program that users can invoke without their having to
know that the program is
written in @command{awk}.
@cindex sidebar @subentry Understanding @samp{#!}
-@ifdocbook
-@docbook
-<sidebar><title>Understanding @samp{#!}</title>
-@end docbook
-
-@cindex portability @subentry @code{#!} (executable scripts)
-
-@command{awk} is an @dfn{interpreted} language. This means that the
-@command{awk} utility reads your program and then processes your data
-according to the instructions in your program. (This is different
-from a @dfn{compiled} language such as C, where your program is first
-compiled into machine code that is executed directly by your system's
-processor.) The @command{awk} utility is thus termed an @dfn{interpreter}.
-Many modern languages are interpreted.
-
-The line beginning with @samp{#!} lists the full @value{FN} of an
-interpreter to run and a single optional initial command-line argument
-to pass to that interpreter. The operating system then runs the
-interpreter with the given argument and the full argument list of the
-executed program. The first argument in the list is the full @value{FN}
-of the @command{awk} program. The rest of the argument list contains
-either options to @command{awk}, or @value{DF}s, or both. (Note that on
-many systems @command{awk} is found in @file{/usr/bin} instead of
-in @file{/bin}.)
-
-Some systems limit the length of the interpreter name to 32 characters.
-Often, this can be dealt with by using a symbolic link.
-
-You should not put more than one argument on the @samp{#!}
-line after the path to @command{awk}. It does not work. The operating system
-treats the rest of the line as a single argument and passes it to
@command{awk}.
-Doing this leads to confusing behavior---most likely a usage diagnostic
-of some sort from @command{awk}.
-
-@cindex @code{ARGC}/@code{ARGV} variables @subentry portability and
-@cindex portability @subentry @code{ARGV} variable
-@cindex dark corner @subentry @code{ARGV} variable, value of
-Finally, the value of @code{ARGV[0]}
-(@pxref{Built-in Variables})
-varies depending upon your operating system.
-Some systems put @samp{awk} there, some put the full pathname
-of @command{awk} (such as @file{/bin/awk}), and some put the name
-of your script (@samp{advice}). @value{DARKCORNER}
-Don't rely on the value of @code{ARGV[0]}
-to provide your script name.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Understanding @samp{#!}}
-
-
+@cartouche Understanding @samp{#!}
@cindex portability @subentry @code{#!} (executable scripts)
@command{awk} is an @dfn{interpreted} language. This means that the
@@ -2813,7 +2722,6 @@ of your script (@samp{advice}). @value{DARKCORNER}
Don't rely on the value of @code{ARGV[0]}
to provide your script name.
@end cartouche
-@end ifnotdocbook
@node Comments
@subsection Comments in @command{awk} Programs
@@ -4658,49 +4566,7 @@ the value of @code{FS} is not
strictly necessary. It remains for historical compatibility.
@cindex sidebar @subentry Quoting Shell Variables On The @command{awk} Command
Line
-@ifdocbook
-@docbook
-<sidebar><title>Quoting Shell Variables On The @command{awk} Command
Line</title>
-@end docbook
-
-@cindex quoting @subentry in @command{gawk} command lines
-@cindex shell quoting, rules for
-@cindex null strings @subentry in @command{gawk} arguments, quoting and
-
-Small @command{awk} programs are often embedded in larger shell scripts,
-so it's worthwhile to understand some shell basics. Consider the following:
-
-@example
-f=""
-awk '@{ print("hi") @}' $f
-@end example
-
-In this case, @command{awk} reads from standard input instead of trying
-to open any command line files. To the unwary, this looks like @command{awk}
-is hanging.
-
-However @command{awk} doesn't see an explicit empty string. When a
-variable expansion is the null string, @emph{and} it's not quoted,
-the shell simply removes it from the command line. To demonstrate:
-
-@example
-$ @kbd{f=""}
-$ @kbd{awk 'BEGIN @{ print ARGC @}' $f}
-@print{} 1
-$ @kbd{awk 'BEGIN @{ print ARGC @}' "$f"}
-@print{} 2
-@end example
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Quoting Shell Variables On The @command{awk} Command Line}
-
-
+@cartouche Quoting Shell Variables On The @command{awk} Command Line
@cindex quoting @subentry in @command{gawk} command lines
@cindex shell quoting, rules for
@cindex null strings @subentry in @command{gawk} arguments, quoting and
@@ -4729,7 +4595,6 @@ $ @kbd{awk 'BEGIN @{ print ARGC @}' "$f"}
@print{} 2
@end example
@end cartouche
-@end ifnotdocbook
@node Naming Standard Input
@section Naming Standard Input
@@ -5818,55 +5683,7 @@ shown in the previous list or that is not an operator.
@c 11/2014: Moved so as to not stack sidebars
@cindex sidebar @subentry Backslash Before Regular Characters
-@ifdocbook
-@docbook
-<sidebar><title>Backslash Before Regular Characters</title>
-@end docbook
-
-@cindex portability @subentry backslash in escape sequences
-@cindex POSIX @command{awk} @subentry backslashes in string constants
-@cindex backslash (@code{\}) @subentry in escape sequences @subentry POSIX and
-@cindex @code{\} (backslash) @subentry in escape sequences @subentry POSIX and
-
-@cindex troubleshooting @subentry backslash before nonspecial character
-If you place a backslash in a string constant before something that is
-not one of the characters previously listed, POSIX @command{awk} purposely
-leaves what happens as undefined. There are two choices:
-
-@c @cindex automatic warnings
-@c @cindex warnings, automatic
-@cindex Brian Kernighan's @command{awk}
-@table @asis
-@item Strip the backslash out
-This is what BWK @command{awk} and @command{gawk} both do.
-For example, @code{"a\qc"} is the same as @code{"aqc"}.
-(Because this is such an easy bug both to introduce and to miss,
-@command{gawk} warns you about it.)
-Consider @samp{FS = @w{"[ \t]+\|[ \t]+"}} to use vertical bars
-surrounded by whitespace as the field separator. There should be
-two backslashes in the string: @samp{FS = @w{"[ \t]+\\|[ \t]+"}}.)
-@c I did this! This is why I added the warning.
-
-@cindex @command{gawk} @subentry escape sequences
-@cindex @command{gawk} @subentry escape sequences @seealso{backslash}
-@cindex Unix @command{awk} @subentry backslashes in escape sequences
-@cindex @command{mawk} utility
-@item Leave the backslash alone
-Some other @command{awk} implementations do this.
-In such implementations, typing @code{"a\qc"} is the same as typing
-@code{"a\\qc"}.
-@end table
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Backslash Before Regular Characters}
-
-
+@cartouche Backslash Before Regular Characters
@cindex portability @subentry backslash in escape sequences
@cindex POSIX @command{awk} @subentry backslashes in string constants
@cindex backslash (@code{\}) @subentry in escape sequences @subentry POSIX and
@@ -5901,7 +5718,6 @@ In such implementations, typing @code{"a\qc"} is the same
as typing
@code{"a\\qc"}.
@end table
@end cartouche
-@end ifnotdocbook
To summarize:
@@ -5923,39 +5739,7 @@ literally.
@end itemize
@cindex sidebar @subentry Escape Sequences for Metacharacters
-@ifdocbook
-@docbook
-<sidebar><title>Escape Sequences for Metacharacters</title>
-@end docbook
-
-@cindex metacharacters @subentry escape sequences for
-
-Suppose you use an octal or hexadecimal
-escape to represent a regexp metacharacter.
-(See @ref{Regexp Operators}.)
-Does @command{awk} treat the character as a literal character or as a regexp
-operator?
-
-@cindex dark corner @subentry escape sequences @subentry for metacharacters
-Historically, such characters were taken literally.
-@value{DARKCORNER}
-However, the POSIX standard indicates that they should be treated
-as real metacharacters, which is what @command{gawk} does.
-In compatibility mode (@pxref{Options}),
-@command{gawk} treats the characters represented by octal and hexadecimal
-escape sequences literally when used in regexp constants. Thus,
-@code{/a\52b/} is equivalent to @code{/a\*b/}.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Escape Sequences for Metacharacters}
-
-
+@cartouche Escape Sequences for Metacharacters
@cindex metacharacters @subentry escape sequences for
Suppose you use an octal or hexadecimal
@@ -5974,7 +5758,6 @@ In compatibility mode (@pxref{Options}),
escape sequences literally when used in regexp constants. Thus,
@code{/a\52b/} is equivalent to @code{/a\*b/}.
@end cartouche
-@end ifnotdocbook
@node Regexp Operators
@section Regular Expression Operators
@@ -6200,59 +5983,7 @@ plus sign. However, many other versions of
@command{awk} treat such a
usage as a syntax error.
@cindex sidebar @subentry What About The Empty Regexp?
-@ifdocbook
-@docbook
-<sidebar><title>What About The Empty Regexp?</title>
-@end docbook
-
-@cindex empty regexps
-@cindex regexps, empty
-We describe here an advanced regexp usage. Feel free to skip it
-upon first reading.
-
-You can supply an empty regexp constant (@samp{//}) in all places
-where a regexp is expected. Is this useful? What does it match?
-
-It is useful. It matches the (invisible) empty string at the start
-and end of a string of characters, as well as the empty string
-between characters. This is best illustrated with the @code{gsub()}
-function, which makes global substitutions in a string
-(@pxref{String Functions}). Normal usage of @code{gsub()} is like
-so:
-
-@example
-$ @kbd{awk '}
-> @kbd{BEGIN @{}
-> @kbd{ x = "ABC_CBA"}
-> @kbd{ gsub(/B/, "bb", x)}
-> @kbd{ print x}
-> @kbd{@}'}
-@print{} AbbC_CbbA
-@end example
-
-We can use @code{gsub()} to see where the empty strings
-are that match the empty regexp:
-
-@example
-$ @kbd{awk '}
-> @kbd{BEGIN @{}
-> @kbd{ x = "ABC"}
-> @kbd{ gsub(//, "x", x)}
-> @kbd{ print x}
-> @kbd{@}'}
-@print{} xAxBxCx
-@end example
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{What About The Empty Regexp?}
-
-
+@cartouche What About The Empty Regexp?
@cindex empty regexps
@cindex regexps, empty
We describe here an advanced regexp usage. Feel free to skip it
@@ -6291,7 +6022,6 @@ $ @kbd{awk '}
@print{} xAxBxCx
@end example
@end cartouche
-@end ifnotdocbook
@node Interval Expressions
@subsection Some Notes On Interval Expressions
@@ -6660,49 +6390,7 @@ intend a regexp match.
@end itemize
@cindex sidebar @subentry Using @code{\n} in Bracket Expressions of Dynamic
Regexps
-@ifdocbook
-@docbook
-<sidebar><title>Using @code{\n} in Bracket Expressions of Dynamic
Regexps</title>
-@end docbook
-
-@cindex regular expressions @subentry dynamic @subentry with embedded newlines
-@cindex newlines @subentry in dynamic regexps
-
-Some older versions of @command{awk} do not allow the newline
-character to be used inside a bracket expression for a dynamic regexp:
-
-@example
-$ @kbd{awk '$0 ~ "[ \t\n]"'}
-@error{} awk: newline in character class [
-@error{} ]...
-@error{} source line number 1
-@error{} context is
-@error{} $0 ~ "[ >>> \t\n]" <<<
-@end example
-
-@cindex newlines @subentry in regexp constants
-But a newline in a regexp constant works with no problem:
-
-@example
-$ @kbd{awk '$0 ~ /[ \t\n]/'}
-@kbd{here is a sample line}
-@print{} here is a sample line
-@kbd{Ctrl-d}
-@end example
-
-@command{gawk} does not have this problem, and it isn't likely to
-occur often in practice, but it's worth noting for future reference.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Using @code{\n} in Bracket Expressions of Dynamic Regexps}
-
-
+@cartouche Using @code{\n} in Bracket Expressions of Dynamic Regexps
@cindex regular expressions @subentry dynamic @subentry with embedded newlines
@cindex newlines @subentry in dynamic regexps
@@ -6731,7 +6419,6 @@ $ @kbd{awk '$0 ~ /[ \t\n]/'}
@command{gawk} does not have this problem, and it isn't likely to
occur often in practice, but it's worth noting for future reference.
@end cartouche
-@end ifnotdocbook
@node GNU Regexp Operators
@section @command{gawk}-Specific Regexp Operators
@@ -7350,35 +7037,7 @@ if the input text that could match the trailing part is
fairly long.
no guarantee that this will never happen.
@cindex sidebar @subentry Caveats When Using Regular Expressions for @code{RS}
-@ifdocbook
-@docbook
-<sidebar><title>Caveats When Using Regular Expressions for @code{RS}</title>
-@end docbook
-
-Remember that in @command{awk}, the @samp{^} and @samp{$} anchor
-metacharacters match the beginning and end of a @emph{string}, and not
-the beginning and end of a @emph{line}. As a result, something like
-@samp{RS = "^[[:upper:]]"} can only match at the beginning of a file.
-This is because @command{gawk} views the input file as one long string
-that happens to contain newline characters.
-It is thus best to avoid anchor metacharacters in the value of @code{RS}.
-
-Record splitting with regular expressions works differently than
-regexp matching with the @code{sub()}, @code{gsub()}, and @code{gensub()}
-(@pxref{String Functions}). Those functions allow a regexp to match the empty
string;
-record splitting does not. Thus, for example @samp{RS = "()"} does @emph{not}
-split records between characters.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Caveats When Using Regular Expressions for @code{RS}}
-
-
+@cartouche Caveats When Using Regular Expressions for @code{RS}
Remember that in @command{awk}, the @samp{^} and @samp{$} anchor
metacharacters match the beginning and end of a @emph{string}, and not
the beginning and end of a @emph{line}. As a result, something like
@@ -7393,7 +7052,6 @@ regexp matching with the @code{sub()}, @code{gsub()}, and
@code{gensub()}
record splitting does not. Thus, for example @samp{RS = "()"} does @emph{not}
split records between characters.
@end cartouche
-@end ifnotdocbook
@cindex @command{gawk} @subentry @code{RT} variable in
@cindex @code{RT} variable
@@ -7411,63 +7069,7 @@ As of October, 2019, BWK @command{awk} also supports it.
Neither
version supplies @code{RT}, however.
@cindex sidebar @subentry @code{RS = "\0"} Is Not Portable
-@ifdocbook
-@docbook
-<sidebar><title>@code{RS = "\0"} Is Not Portable</title>
-@end docbook
-
-@cindex portability @subentry data files as single record
-There are times when you might want to treat an entire @value{DF} as a
-single record. The only way to make this happen is to give @code{RS}
-a value that you know doesn't occur in the input file. This is hard
-to do in a general way, such that a program always works for arbitrary
-input files.
-
-You might think that for text files, the @sc{nul} character, which
-consists of a character with all bits equal to zero, is a good
-value to use for @code{RS} in this case:
-
-@example
-BEGIN @{ RS = "\0" @} # whole file becomes one record?
-@end example
-
-@cindex differences in @command{awk} and @command{gawk} @subentry strings
@subentry storing
-@command{gawk} in fact accepts this, and uses the @sc{nul}
-character for the record separator.
-This works for certain special files, such as @file{/proc/environ} on
-GNU/Linux systems, where the @sc{nul} character is in fact the record
separator.
-However, this usage is @emph{not} portable
-to most other @command{awk} implementations.
-
-@cindex dark corner @subentry strings, storing
-Almost all other @command{awk} implementations@footnote{At least that we know
-about.} store strings internally as C-style strings. C strings use the
-@sc{nul} character as the string terminator. In effect, this means that
-@samp{RS = "\0"} is the same as @samp{RS = ""}.
-@value{DARKCORNER}
-
-It happens that recent versions of @command{mawk} can use the @sc{nul}
-character as a record separator. However, this is a special case:
-@command{mawk} does not allow embedded @sc{nul} characters in strings.
-(This may change in a future version of @command{mawk}.)
-
-@cindex records @subentry treating files as
-@cindex treating files, as single records
-@cindex single records, treating files as
-@xref{Readfile Function} for an interesting way to read
-whole files. If you are using @command{gawk}, see @ref{Extension Sample
-Readfile} for another option.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{@code{RS = "\0"} Is Not Portable}
-
-
+@cartouche @code{RS = "\0"} Is Not Portable
@cindex portability @subentry data files as single record
There are times when you might want to treat an entire @value{DF} as a
single record. The only way to make this happen is to give @code{RS}
@@ -7510,7 +7112,6 @@ character as a record separator. However, this is a
special case:
whole files. If you are using @command{gawk}, see @ref{Extension Sample
Readfile} for another option.
@end cartouche
-@end ifnotdocbook
@node Fields
@section Examining Fields
@@ -7836,36 +7437,7 @@ such as @code{sub()} and @code{gsub()}
(@pxref{String Functions}).
@cindex sidebar @subentry Understanding @code{$0}
-@ifdocbook
-@docbook
-<sidebar><title>Understanding @code{$0}</title>
-@end docbook
-
-
-It is important to remember that @code{$0} is the @emph{full}
-record, exactly as it was read from the input. This includes
-any leading or trailing whitespace, and the exact whitespace (or other
-characters) that separates the fields.
-
-It is a common error to try to change the field separators
-in a record simply by setting @code{FS} and @code{OFS}, and then
-expecting a plain @samp{print} or @samp{print $0} to print the
-modified record.
-
-But this does not work, because nothing was done to change the record
-itself. Instead, you must force the record to be rebuilt, typically
-with a statement such as @samp{$1 = $1}, as described earlier.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Understanding @code{$0}}
-
-
+@cartouche Understanding @code{$0}
It is important to remember that @code{$0} is the @emph{full}
record, exactly as it was read from the input. This includes
@@ -7881,7 +7453,6 @@ But this does not work, because nothing was done to
change the record
itself. Instead, you must force the record to be rebuilt, typically
with a statement such as @samp{$1 = $1}, as described earlier.
@end cartouche
-@end ifnotdocbook
@node Field Separators
@@ -8199,37 +7770,7 @@ or @code{FPAT}.
@cindex Kernighan, Brian @subentry quotes
@cindex sidebar @subentry Carriage-Return--Line-Feed Line Endings In CSV Files
-@ifdocbook
-@docbook
-<sidebar><title>Carriage-Return--Line-Feed Line Endings In CSV Files</title>
-@end docbook
-
-@quotation
-@code{\r\n} @i{is the invention of the devil.}
-@author Brian Kernighan
-@end quotation
-
-Many CSV files are imported from systems where the line terminator
-for text files is a carriage-return--line-feed pair
-(CR-LF, @samp{\r} followed by @samp{\n}).
-For ease of use, when processing CSV files, @command{gawk} converts
-CR-LF pairs into a single newline. That is, the @samp{\r} is removed.
-
-This occurs only when a CR is paired with an LF; a standalone CR
-is left alone. This behavior is consistent with Windows systems
-which automatically convert CR-LF in files into a plain LF in memory,
-and also with the commonly available @command{unix2dos} utility program.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Carriage-Return--Line-Feed Line Endings In CSV Files}
-
-
+@cartouche Carriage-Return--Line-Feed Line Endings In CSV Files
@quotation
@code{\r\n} @i{is the invention of the devil.}
@author Brian Kernighan
@@ -8246,7 +7787,6 @@ is left alone. This behavior is consistent with Windows
systems
which automatically convert CR-LF in files into a plain LF in memory,
and also with the commonly available @command{unix2dos} utility program.
@end cartouche
-@end ifnotdocbook
The behavior of the @code{split()} function (not formally discussed
yet, see @ref{String Functions}) differs slightly when processing CSV
@@ -8388,65 +7928,7 @@ awk -F'\n' '@var{program}' @var{files @dots{}}
When you do this, @code{$1} is the same as @code{$0}.
@cindex sidebar @subentry Changing @code{FS} Does Not Affect the Fields
-@ifdocbook
-@docbook
-<sidebar><title>Changing @code{FS} Does Not Affect the Fields</title>
-@end docbook
-
-
-@cindex POSIX @command{awk} @subentry field separators and
-@cindex field separator @subentry POSIX and
-According to the POSIX standard, @command{awk} is supposed to behave
-as if each record is split into fields at the time it is read.
-In particular, this means that if you change the value of @code{FS}
-after a record is read, the values of the fields (i.e., how they were split)
-should reflect the old value of @code{FS}, not the new one.
-
-@cindex dark corner @subentry field separators
-@cindex @command{sed} utility
-@cindex stream editors
-However, many older implementations of @command{awk} do not work this way.
Instead,
-they defer splitting the fields until a field is actually
-referenced. The fields are split
-using the @emph{current} value of @code{FS}!
-@value{DARKCORNER}
-This behavior can be difficult
-to diagnose. The following example illustrates the difference
-between the two methods:
-
-@example
-sed 1q /etc/passwd | awk '@{ FS = ":" ; print $1 @}'
-@end example
-
-@noindent
-which usually prints:
-
-@example
-root
-@end example
-
-@noindent
-on an incorrect implementation of @command{awk}, while @command{gawk}
-prints the full first line of the file, something like:
-
-@example
-root:x:0:0:Root:/:
-@end example
-
-(The @command{sed}@footnote{The @command{sed} utility is a ``stream editor.''
-Its behavior is also defined by the POSIX standard.}
-command prints just the first line of @file{/etc/passwd}.)
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Changing @code{FS} Does Not Affect the Fields}
-
-
+@cartouche Changing @code{FS} Does Not Affect the Fields
@cindex POSIX @command{awk} @subentry field separators and
@cindex field separator @subentry POSIX and
@@ -8491,7 +7973,6 @@ root:x:0:0:Root:/:
Its behavior is also defined by the POSIX standard.}
command prints just the first line of @file{/etc/passwd}.)
@end cartouche
-@end ifnotdocbook
@node Field Splitting Summary
@subsection Field-Splitting Summary
@@ -8534,41 +8015,7 @@ Each individual character in the record becomes a
separate field.
@end table
@cindex sidebar @subentry @code{FS} and @code{IGNORECASE}
-@ifdocbook
-@docbook
-<sidebar><title>@code{FS} and @code{IGNORECASE}</title>
-@end docbook
-
-
-The @code{IGNORECASE} variable
-(@pxref{User-modified})
-affects field splitting @emph{only} when the value of @code{FS} is a regexp.
-It has no effect when @code{FS} is a single character, even if
-that character is a letter. Thus, in the following code:
-
-@example
-FS = "c"
-IGNORECASE = 1
-$0 = "aCa"
-print $1
-@end example
-
-@noindent
-The output is @samp{aCa}. If you really want to split fields on an
-alphabetic character while ignoring case, use a regexp that will
-do it for you (e.g., @samp{FS = "[c]"}). In this case, @code{IGNORECASE}
-will take effect.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{@code{FS} and @code{IGNORECASE}}
-
-
+@cartouche @code{FS} and @code{IGNORECASE}
The @code{IGNORECASE} variable
(@pxref{User-modified})
@@ -8589,7 +8036,6 @@ alphabetic character while ignoring case, use a regexp
that will
do it for you (e.g., @samp{FS = "[c]"}). In this case, @code{IGNORECASE}
will take effect.
@end cartouche
-@end ifnotdocbook
@node Constant Size
@@ -11182,46 +10628,7 @@ program may have open to just one! In @command{gawk},
there is no such limit.
open as many pipelines as the underlying operating system permits.
@cindex sidebar @subentry Piping into @command{sh}
-@ifdocbook
-@docbook
-<sidebar><title>Piping into @command{sh}</title>
-@end docbook
-
-@cindex shells @subentry piping commands into
-
-A particularly powerful way to use redirection is to build command lines
-and pipe them into the shell, @command{sh}. For example, suppose you
-have a list of files brought over from a system where all the @value{FN}s
-are stored in uppercase, and you wish to rename them to have names in
-all lowercase. The following program is both simple and efficient:
-
-@c @cindex @command{mv} utility
-@example
-@{ printf("mv %s %s\n", $0, tolower($0)) | "sh" @}
-
-END @{ close("sh") @}
-@end example
-
-The @code{tolower()} function returns its argument string with all
-uppercase characters converted to lowercase
-(@pxref{String Functions}).
-The program builds up a list of command lines,
-using the @command{mv} utility to rename the files.
-It then sends the list to the shell for execution.
-
-@xref{Shell Quoting} for a function that can help in generating
-command lines to be fed to the shell.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Piping into @command{sh}}
-
-
+@cartouche Piping into @command{sh}
@cindex shells @subentry piping commands into
A particularly powerful way to use redirection is to build command lines
@@ -11247,7 +10654,6 @@ It then sends the list to the shell for execution.
@xref{Shell Quoting} for a function that can help in generating
command lines to be fed to the shell.
@end cartouche
-@end ifnotdocbook
@node Special FD
@section Special Files for Standard Preopened Data Streams
@@ -12122,34 +11528,7 @@ If @command{gawk} is in compatibility mode
they are not available.
@cindex sidebar @subentry A Constant's Base Does Not Affect Its Value
-@ifdocbook
-@docbook
-<sidebar><title>A Constant's Base Does Not Affect Its Value</title>
-@end docbook
-
-
-Once a numeric constant has
-been converted internally into a number,
-@command{gawk} no longer remembers
-what the original form of the constant was; the internal value is
-always used. This has particular consequences for conversion of
-numbers to strings:
-
-@example
-$ @kbd{gawk 'BEGIN @{ printf "0x11 is <%s>\n", 0x11 @}'}
-@print{} 0x11 is <17>
-@end example
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{A Constant's Base Does Not Affect Its Value}
-
-
+@cartouche A Constant's Base Does Not Affect Its Value
Once a numeric constant has
been converted internally into a number,
@@ -12163,7 +11542,6 @@ $ @kbd{gawk 'BEGIN @{ printf "0x11 is <%s>\n", 0x11 @}'}
@print{} 0x11 is <17>
@end example
@end cartouche
-@end ifnotdocbook
@node Regexp Constants
@subsubsection Regular Expression Constants
@@ -12648,34 +12026,7 @@ b = a ""
@value{DARKCORNER}
@cindex sidebar @subentry Pre-POSIX @command{awk} Used @code{OFMT} for String
Conversion
-@ifdocbook
-@docbook
-<sidebar><title>Pre-POSIX @command{awk} Used @code{OFMT} for String
Conversion</title>
-@end docbook
-
-@cindex POSIX @command{awk} @subentry @code{OFMT} variable and
-@cindex @code{OFMT} variable
-@cindex portability @subentry new @command{awk} vs.@: old @command{awk}
-@cindex @command{awk} @subentry new vs.@: old @subentry @code{OFMT} variable
-Prior to the POSIX standard, @command{awk} used the value
-of @code{OFMT} for converting numbers to strings. @code{OFMT}
-specifies the output format to use when printing numbers with @code{print}.
-@code{CONVFMT} was introduced in order to separate the semantics of
-conversion from the semantics of printing. Both @code{CONVFMT} and
-@code{OFMT} have the same default value: @code{"%.6g"}. In the vast majority
-of cases, old @command{awk} programs do not change their behavior.
-@xref{Print} for more information on the @code{print} statement.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Pre-POSIX @command{awk} Used @code{OFMT} for String Conversion}
-
-
+@cartouche Pre-POSIX @command{awk} Used @code{OFMT} for String Conversion
@cindex POSIX @command{awk} @subentry @code{OFMT} variable and
@cindex @code{OFMT} variable
@cindex portability @subentry new @command{awk} vs.@: old @command{awk}
@@ -12689,7 +12040,6 @@ conversion from the semantics of printing. Both
@code{CONVFMT} and
of cases, old @command{awk} programs do not change their behavior.
@xref{Print} for more information on the @code{print} statement.
@end cartouche
-@end ifnotdocbook
@node Locale influences conversions
@subsubsection Locales Can Influence Conversion
@@ -13268,57 +12618,7 @@ For maximum portability, do not use the @samp{**=}
operator.
@end quotation
@cindex sidebar @subentry Syntactic Ambiguities Between @samp{/=} and Regular
Expressions
-@ifdocbook
-@docbook
-<sidebar><title>Syntactic Ambiguities Between @samp{/=} and Regular
Expressions</title>
-@end docbook
-
-@cindex dark corner @subentry regexp constants @subentry @code{/=} operator and
-@cindex @code{/} (forward slash) @subentry @code{/=} operator @subentry vs.@:
@code{/=@dots{}/} regexp constant
-@cindex forward slash (@code{/}) @subentry @code{/=} operator @subentry vs.@:
@code{/=@dots{}/} regexp constant
-@cindex regexp constants @subentry @code{/=@dots{}/} @subentry @code{/=}
operator and
-
-@c derived from email from "Nelson H. F. Beebe" <beebe@math.utah.edu>
-@c Date: Mon, 1 Sep 1997 13:38:35 -0600 (MDT)
-
-@cindex dark corner @subentry @code{/=} operator vs.@: @code{/=@dots{}/}
regexp constant
-@cindex ambiguity, syntactic: @code{/=} operator vs.@: @code{/=@dots{}/}
regexp constant
-@cindex syntactic ambiguity: @code{/=} operator vs.@: @code{/=@dots{}/} regexp
constant
-@cindex @code{/=} operator vs.@: @code{/=@dots{}/} regexp constant
-There is a syntactic ambiguity between the @code{/=} assignment
-operator and regexp constants whose first character is an @samp{=}.
-@value{DARKCORNER}
-This is most notable in some commercial @command{awk} versions.
-For example:
-
-@example
-$ @kbd{awk /==/ /dev/null}
-@error{} awk: syntax error at source line 1
-@error{} context is
-@error{} >>> /= <<<
-@error{} awk: bailing out at source line 1
-@end example
-
-@noindent
-A workaround is:
-
-@example
-awk '/[=]=/' /dev/null
-@end example
-
-@command{gawk} does not have this problem; BWK @command{awk}
-and @command{mawk} also do not.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Syntactic Ambiguities Between @samp{/=} and Regular Expressions}
-
-
+@cartouche Syntactic Ambiguities Between @samp{/=} and Regular Expressions
@cindex dark corner @subentry regexp constants @subentry @code{/=} operator and
@cindex @code{/} (forward slash) @subentry @code{/=} operator @subentry vs.@:
@code{/=@dots{}/} regexp constant
@cindex forward slash (@code{/}) @subentry @code{/=} operator @subentry vs.@:
@code{/=@dots{}/} regexp constant
@@ -13355,7 +12655,6 @@ awk '/[=]=/' /dev/null
@command{gawk} does not have this problem; BWK @command{awk}
and @command{mawk} also do not.
@end cartouche
-@end ifnotdocbook
@node Increment Ops
@subsection Increment and Decrement Operators
@@ -13441,63 +12740,7 @@ like @samp{@var{lvalue}++}, but instead of adding, it
subtracts.)
@end table
@cindex sidebar @subentry Operator Evaluation Order
-@ifdocbook
-@docbook
-<sidebar><title>Operator Evaluation Order</title>
-@end docbook
-
-@cindex precedence
-@cindex operators @subentry precedence of
-@cindex portability @subentry operators
-@cindex evaluation order
-@cindex Marx, Groucho
-@quotation
-@i{Doctor, it hurts when I do this!@*
-Then don't do that!}
-@author Groucho Marx
-@end quotation
-
-@noindent
-What happens for something like the following?
-
-@example
-b = 6
-print b += b++
-@end example
-
-@noindent
-Or something even stranger?
-
-@example
-b = 6
-b += ++b + b++
-print b
-@end example
-
-@cindex side effects
-In other words, when do the various side effects prescribed by the
-postfix operators (@samp{b++}) take effect?
-When side effects happen is @dfn{implementation-defined}.
-In other words, it is up to the particular version of @command{awk}.
-The result for the first example may be 12 or 13, and for the second, it
-may be 22 or 23.
-
-In short, doing things like this is not recommended and definitely
-not anything that you can rely upon for portability.
-You should avoid such things in your own programs.
-@c You'll sleep better at night and be able to look at yourself
-@c in the mirror in the morning.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Operator Evaluation Order}
-
-
+@cartouche Operator Evaluation Order
@cindex precedence
@cindex operators @subentry precedence of
@cindex portability @subentry operators
@@ -13540,7 +12783,6 @@ You should avoid such things in your own programs.
@c You'll sleep better at night and be able to look at yourself
@c in the mirror in the morning.
@end cartouche
-@end ifnotdocbook
@node Truth Values and Conditions
@section Truth Values and Conditions
@@ -16995,51 +16237,7 @@ is available as an element within the @code{SYMTAB}
array.
@end table
@cindex sidebar @subentry Changing @code{NR} and @code{FNR}
-@ifdocbook
-@docbook
-<sidebar><title>Changing @code{NR} and @code{FNR}</title>
-@end docbook
-
-@cindex @code{NR} variable @subentry changing
-@cindex @code{FNR} variable @subentry changing
-@cindex dark corner @subentry @code{FNR}/@code{NR} variables
-@command{awk} increments @code{NR} and @code{FNR}
-each time it reads a record, instead of setting them to the absolute
-value of the number of records read. This means that a program can
-change these variables and their new values are incremented for
-each record.
-@value{DARKCORNER}
-The following example shows this:
-
-@example
-$ @kbd{echo '1}
-> @kbd{2}
-> @kbd{3}
-> @kbd{4' | awk 'NR == 2 @{ NR = 17 @}}
-> @kbd{@{ print NR @}'}
-@print{} 1
-@print{} 17
-@print{} 18
-@print{} 19
-@end example
-
-@noindent
-Before @code{FNR} was added to the @command{awk} language
-(@pxref{V7/SVR3.1}),
-many @command{awk} programs used this feature to track the number of
-records in a file by resetting @code{NR} to zero when @code{FILENAME}
-changed.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Changing @code{NR} and @code{FNR}}
-
-
+@cartouche Changing @code{NR} and @code{FNR}
@cindex @code{NR} variable @subentry changing
@cindex @code{FNR} variable @subentry changing
@cindex dark corner @subentry @code{FNR}/@code{NR} variables
@@ -17070,7 +16268,6 @@ many @command{awk} programs used this feature to track
the number of
records in a file by resetting @code{NR} to zero when @code{FILENAME}
changed.
@end cartouche
-@end ifnotdocbook
@node ARGC and ARGV
@subsection Using @code{ARGC} and @code{ARGV}
@@ -19813,38 +19010,7 @@ special rules involved for @code{FS}.
@end itemize
@cindex sidebar @subentry Matching the Null String
-@ifdocbook
-@docbook
-<sidebar><title>Matching the Null String</title>
-@end docbook
-
-@cindex matching @subentry null strings
-@cindex null strings @subentry matching
-@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry null
strings, matching
-@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry null
strings, matching
-
-In @command{awk}, the @samp{*} operator can match the null string.
-This is particularly important for the @code{sub()}, @code{gsub()},
-and @code{gensub()} functions. For example:
-
-@example
-$ @kbd{echo abc | awk '@{ gsub(/m*/, "X"); print @}'}
-@print{} XaXbXcX
-@end example
-
-@noindent
-Although this makes a certain amount of sense, it can be surprising.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Matching the Null String}
-
-
+@cartouche Matching the Null String
@cindex matching @subentry null strings
@cindex null strings @subentry matching
@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry null
strings, matching
@@ -19862,7 +19028,6 @@ $ @kbd{echo abc | awk '@{ gsub(/m*/, "X"); print @}'}
@noindent
Although this makes a certain amount of sense, it can be surprising.
@end cartouche
-@end ifnotdocbook
@node Gory Details
@@ -20269,62 +19434,7 @@ In such a case, @code{fflush()} returns @minus{}1, as
well.
@end table
@cindex sidebar @subentry Interactive Versus Noninteractive Buffering
-@ifdocbook
-@docbook
-<sidebar><title>Interactive Versus Noninteractive Buffering</title>
-@end docbook
-
-@cindex buffering @subentry interactive vs.@: noninteractive
-
-As a side point, buffering issues can be even more confusing if
-your program is @dfn{interactive} (i.e., communicating
-with a user sitting at a keyboard).@footnote{A program is interactive
-if the standard output is connected to a terminal device. On modern
-systems, this means your keyboard and screen.}
-
-@c Thanks to Walter.Mecky@dresdnerbank.de for this example, and for
-@c motivating me to write this section.
-Interactive programs generally @dfn{line buffer} their output (i.e., they
-write out every line). Noninteractive programs wait until they have
-a full buffer, which may be many lines of output.
-Here is an example of the difference:
-
-@example
-$ @kbd{awk '@{ print $1 + $2 @}'}
-@kbd{1 1}
-@print{} 2
-@kbd{2 3}
-@print{} 5
-@kbd{Ctrl-d}
-@end example
-
-@noindent
-Each line of output is printed immediately. Compare that behavior
-with this example:
-
-@example
-$ @kbd{awk '@{ print $1 + $2 @}' | cat}
-@kbd{1 1}
-@kbd{2 3}
-@kbd{Ctrl-d}
-@print{} 2
-@print{} 5
-@end example
-
-@noindent
-Here, no output is printed until after the @kbd{Ctrl-d} is typed, because
-it is all buffered and sent down the pipe to @command{cat} in one shot.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Interactive Versus Noninteractive Buffering}
-
-
+@cartouche Interactive Versus Noninteractive Buffering
@cindex buffering @subentry interactive vs.@: noninteractive
As a side point, buffering issues can be even more confusing if
@@ -20366,7 +19476,6 @@ $ @kbd{awk '@{ print $1 + $2 @}' | cat}
Here, no output is printed until after the @kbd{Ctrl-d} is typed, because
it is all buffered and sent down the pipe to @command{cat} in one shot.
@end cartouche
-@end ifnotdocbook
@table @asis
@item @code{system(@var{command})}
@@ -20448,76 +19557,7 @@ As of August, 2018, BWK @command{awk} now follows
@command{gawk}'s behavior
for the return value of @code{system()}.
@cindex sidebar @subentry Controlling Output Buffering with @code{system()}
-@ifdocbook
-@docbook
-<sidebar><title>Controlling Output Buffering with @code{system()}</title>
-@end docbook
-
-@cindex buffers @subentry flushing
-@cindex buffering @subentry input/output
-@cindex output @subentry buffering
-
-The @code{fflush()} function provides explicit control over output buffering
for
-individual files and pipes. However, its use is not portable to many older
-@command{awk} implementations. An alternative method to flush output
-buffers is to call @code{system()} with a null string as its argument:
-
-@example
-system("") # flush output
-@end example
-
-@noindent
-@command{gawk} treats this use of the @code{system()} function as a special
-case and is smart enough not to run a shell (or other command
-interpreter) with the empty command. Therefore, with @command{gawk}, this
-idiom is not only useful, it is also efficient. Although this method should
work
-with other @command{awk} implementations, it does not necessarily avoid
-starting an unnecessary shell. (Other implementations may only
-flush the buffer associated with the standard output and not necessarily
-all buffered output.)
-
-If you think about what a programmer expects, it makes sense that
-@code{system()} should flush any pending output. The following program:
-
-@example
-BEGIN @{
- print "first print"
- system("echo system echo")
- print "second print"
-@}
-@end example
-
-@noindent
-must print:
-
-@example
-first print
-system echo
-second print
-@end example
-
-@noindent
-and not:
-
-@example
-system echo
-first print
-second print
-@end example
-
-If @command{awk} did not flush its buffers before calling @code{system()},
-you would see the latter (undesirable) output.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Controlling Output Buffering with @code{system()}}
-
-
+@cartouche Controlling Output Buffering with @code{system()}
@cindex buffers @subentry flushing
@cindex buffering @subentry input/output
@cindex output @subentry buffering
@@ -20573,7 +19613,6 @@ second print
If @command{awk} did not flush its buffers before calling @code{system()},
you would see the latter (undesirable) output.
@end cartouche
-@end ifnotdocbook
@node Time Functions
@subsection Time Functions
@@ -21260,73 +20299,7 @@ and then demonstrates the
results of the @code{compl()}, @code{lshift()}, and @code{rshift()} functions.
@cindex sidebar @subentry Beware The Smoke and Mirrors!
-@ifdocbook
-@docbook
-<sidebar><title>Beware The Smoke and Mirrors!</title>
-@end docbook
-
-
-It other languages, bitwise operations are performed on integer values,
-not floating-point values. As a general statement, such operations work
-best when performed on unsigned integers.
-
-@command{gawk} attempts to treat the arguments to the bitwise functions
-as unsigned integers. For this reason, negative arguments produce a
-fatal error.
-
-In normal operation, for all of these functions, first the
-double-precision floating-point value is converted to the widest C
-unsigned integer type, then the bitwise operation is performed. If the
-result cannot be represented exactly as a C @code{double}, leading
-nonzero bits are removed one by one until it can be represented exactly.
-The result is then converted back into a C @code{double}.@footnote{If you don't
-understand this paragraph, the upshot is that @command{gawk} can only
-store a particular range of integer values; numbers outside that range
-are reduced to fit within the range.}
-
-However, when using arbitrary precision arithmetic with the @option{-M}
-option (@pxref{Arbitrary Precision Arithmetic}), the results may differ.
-This is particularly noticeable with the @code{compl()} function:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print compl(42) @}'}
-@print{} 9007199254740949
-$ @kbd{gawk -M 'BEGIN @{ print compl(42) @}'}
-@print{} -43
-@end example
-
-What's going on becomes clear when printing the results
-in hexadecimal:
-
-@example
-$ @kbd{gawk 'BEGIN @{ printf "%#x\n", compl(42) @}'}
-@print{} 0x1fffffffffffd5
-$ @kbd{gawk -M 'BEGIN @{ printf "%#x\n", compl(42) @}'}
-@print{} 0xffffffffffffffd5
-@end example
-
-When using the @option{-M} option, under the hood, @command{gawk} uses
-GNU MP arbitrary precision integers which have at least 64 bits of precision.
-When not using @option{-M}, @command{gawk} stores integral values in
-regular double-precision floating point, which only maintain 53 bits of
-precision. Furthermore, the GNU MP library treats (or at least seems to treat)
-the leading bit as a sign bit; thus the result with @option{-M} in this case is
-a negative number.
-
-In short, using @command{gawk} for any but the simplest kind of bitwise
-operations is probably a bad idea; caveat emptor!
-
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Beware The Smoke and Mirrors!}
-
-
+@cartouche Beware The Smoke and Mirrors!
It other languages, bitwise operations are performed on integer values,
not floating-point values. As a general statement, such operations work
@@ -21379,7 +20352,6 @@ In short, using @command{gawk} for any but the simplest
kind of bitwise
operations is probably a bad idea; caveat emptor!
@end cartouche
-@end ifnotdocbook
@node Type Functions
@subsection Getting Type Information
@@ -24110,35 +23082,7 @@ shows how this library function can be used and
how it simplifies writing the main program.
@cindex sidebar @subentry So Why Does @command{gawk} Have @code{BEGINFILE} and
@code{ENDFILE}?
-@ifdocbook
-@docbook
-<sidebar><title>So Why Does @command{gawk} Have @code{BEGINFILE} and
@code{ENDFILE}?</title>
-@end docbook
-
-
-You are probably wondering, if @code{beginfile()} and @code{endfile()}
-functions can do the job, why does @command{gawk} have
-@code{BEGINFILE} and @code{ENDFILE} patterns?
-
-Good question. Normally, if @command{awk} cannot open a file, this
-causes an immediate fatal error. In this case, there is no way for a
-user-defined function to deal with the problem, as the mechanism for
-calling it relies on the file being open and at the first record. Thus,
-the main reason for @code{BEGINFILE} is to give you a ``hook'' to catch
-files that cannot be processed. @code{ENDFILE} exists for symmetry,
-and because it provides an easy way to do per-file cleanup processing.
-For more information, refer to @ref{BEGINFILE/ENDFILE}.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{So Why Does @command{gawk} Have @code{BEGINFILE} and
@code{ENDFILE}?}
-
-
+@cartouche So Why Does @command{gawk} Have @code{BEGINFILE} and @code{ENDFILE}?
You are probably wondering, if @code{beginfile()} and @code{endfile()}
functions can do the job, why does @command{gawk} have
@@ -24153,7 +23097,6 @@ files that cannot be processed. @code{ENDFILE} exists
for symmetry,
and because it provides an easy way to do per-file cleanup processing.
For more information, refer to @ref{BEGINFILE/ENDFILE}.
@end cartouche
-@end ifnotdocbook
@node Rewind Function
@subsection Rereading the Current File
@@ -35680,44 +34623,7 @@ default rounding mode for IEEE 754 computing functions
and operators.
@c January 2018. Thanks to nethox@gmail.com for the example.
@cindex sidebar @subentry Rounding Modes and Conversion
-@ifdocbook
-@docbook
-<sidebar><title>Rounding Modes and Conversion</title>
-@end docbook
-
-It's important to understand that, along with @code{CONVFMT} and
-@code{OFMT}, the rounding mode affects how numbers are converted to strings.
-For example, consider the following program:
-
-@example
-BEGIN @{
- pi = 3.1416
- OFMT = "%.f" # Print value as integer
- print pi # ROUNDMODE = "N" by default.
- ROUNDMODE = "U" # Now change ROUNDMODE
- print pi
-@}
-@end example
-
-@noindent
-Running this program produces this output:
-
-@example
-$ @kbd{gawk -M -f roundmode.awk}
-@print{} 3
-@print{} 4
-@end example
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{Rounding Modes and Conversion}
-
-
+@cartouche Rounding Modes and Conversion
It's important to understand that, along with @code{CONVFMT} and
@code{OFMT}, the rounding mode affects how numbers are converted to strings.
For example, consider the following program:
@@ -35741,7 +34647,6 @@ $ @kbd{gawk -M -f roundmode.awk}
@print{} 4
@end example
@end cartouche
-@end ifnotdocbook
The other rounding modes are rarely used. Rounding toward positive infinity
(@code{roundTowardPositive}) and toward negative infinity
@@ -44452,33 +43357,7 @@ For more information, see
@uref{http://www.skeeve.com/fork-my-code.html,
by Arnold Robbins and Chet Ramey.
@cindex sidebar @subentry A Note About Fuzzers
-@ifdocbook
-@docbook
-<sidebar><title>A Note About Fuzzers</title>
-@end docbook
-
-In recent years, people have been running ``fuzzers'' to generate
-invalid @command{awk} programs in order to find and report (so-called)
-bugs in @command{gawk}.
-
-In general, such reports are not of much practical use. The programs
-they create are not realistic and the bugs found are generally from
-some kind of memory corruption that is fatal anyway.
-
-So, if you want to run a fuzzer against @command{gawk} and report the
-results, you may do so, but be aware that such reports don't carry the
-same weight as reports of real bugs do.
-
-@docbook
-</sidebar>
-@end docbook
-@end ifdocbook
-
-@ifnotdocbook
-@cartouche
-@center @b{A Note About Fuzzers}
-
-
+@cartouche A Note About Fuzzers
In recent years, people have been running ``fuzzers'' to generate
invalid @command{awk} programs in order to find and report (so-called)
bugs in @command{gawk}.
@@ -44491,7 +43370,6 @@ So, if you want to run a fuzzer against @command{gawk}
and report the
results, you may do so, but be aware that such reports don't carry the
same weight as reports of real bugs do.
@end cartouche
-@end ifnotdocbook
@node Bug address
@appendixsubsec Submitting Bug Reports
diff --git a/doc/gawktexi.in b/doc/gawktexi.in
deleted file mode 100644
index 1ea1d333..00000000
--- a/doc/gawktexi.in
+++ /dev/null
@@ -1,47551 +0,0 @@
-\input texinfo @c -*-texinfo-*-
-@c vim: filetype=texinfo
-@c %**start of header (This is for running Texinfo on a region.)
-@setfilename gawk.info
-@settitle The GNU Awk User's Guide
-@c %**end of header (This is for running Texinfo on a region.)
-
-@dircategory Text creation and manipulation
-@direntry
-* Gawk: (gawk). A text scanning and processing language.
-@end direntry
-@dircategory Individual utilities
-@direntry
-* awk: (gawk)Invoking Gawk. Text scanning and processing.
-@end direntry
-
-@ifset FOR_PRINT
-@tex
-\gdef\xrefprintnodename#1{``#1''}
-@end tex
-@end ifset
-
-@ifclear FOR_PRINT
-@c With early 2014 texinfo.tex, restore PDF links and colors
-@tex
-\gdef\linkcolor{0.5 0.09 0.12} % Dark Red
-\gdef\urlcolor{0.5 0.09 0.12} % Also
-\global\urefurlonlylinktrue
-@end tex
-@end ifclear
-
-@ifnotdocbook
-@set BULLET @bullet{}
-@set MINUS @minus{}
-@end ifnotdocbook
-
-@ifdocbook
-@set BULLET
-@set MINUS
-@end ifdocbook
-
-@iftex
-@set TIMES @times
-@end iftex
-@ifnottex
-@set TIMES *
-@end ifnottex
-
-@c Let texinfo.tex give us full section titles
-@xrefautomaticsectiontitle on
-
-@c The following information should be updated here only!
-@c This sets the edition of the document, the version of gawk it
-@c applies to and all the info about who's publishing this edition
-
-@c These apply across the board.
-@set UPDATE-MONTH October, 2023
-@set VERSION 5.3
-@set PATCHLEVEL 0
-
-@set GAWKINETTITLE TCP/IP Internetworking with @command{gawk}
-@set GAWKWORKFLOWTITLE Participating in @command{gawk} Development
-@set PMGAWKTITLE Persistent-Memory @command{gawk} User Manual
-@ifset FOR_PRINT
-@set TITLE Effective awk Programming
-@end ifset
-@ifclear FOR_PRINT
-@set TITLE GAWK: Effective AWK Programming
-@end ifclear
-@set SUBTITLE A User's Guide for GNU Awk
-@set EDITION 5.3
-
-@iftex
-@set DOCUMENT book
-@set CHAPTER chapter
-@set APPENDIX appendix
-@set SECTION section
-@set SUBSECTION subsection
-@set DARKCORNER @inmargin{@image{lflashlight,1cm}, @image{rflashlight,1cm}}
-@set COMMONEXT (c.e.)
-@set PAGE page
-@end iftex
-@iflatex
-@set DOCUMENT book
-@set CHAPTER chapter
-@set APPENDIX appendix
-@set SECTION section
-@set SUBSECTION subsection
-@set DARKCORNER (d.c.)
-@set COMMONEXT (c.e.)
-@set PAGE page
-@end iflatex
-@ifinfo
-@set DOCUMENT Info file
-@set CHAPTER major node
-@set APPENDIX major node
-@set SECTION minor node
-@set SUBSECTION node
-@set DARKCORNER (d.c.)
-@set COMMONEXT (c.e.)
-@set PAGE screen
-@end ifinfo
-@ifhtml
-@set DOCUMENT Web page
-@set CHAPTER chapter
-@set APPENDIX appendix
-@set SECTION section
-@set SUBSECTION subsection
-@set DARKCORNER (d.c.)
-@set COMMONEXT (c.e.)
-@set PAGE screen
-@end ifhtml
-@ifdocbook
-@set DOCUMENT book
-@set CHAPTER chapter
-@set APPENDIX appendix
-@set SECTION section
-@set SUBSECTION subsection
-@set DARKCORNER (d.c.)
-@set COMMONEXT (c.e.)
-@set PAGE page
-@end ifdocbook
-@ifxml
-@set DOCUMENT book
-@set CHAPTER chapter
-@set APPENDIX appendix
-@set SECTION section
-@set SUBSECTION subsection
-@set DARKCORNER (d.c.)
-@set COMMONEXT (c.e.)
-@set PAGE page
-@end ifxml
-@ifplaintext
-@set DOCUMENT book
-@set CHAPTER chapter
-@set APPENDIX appendix
-@set SECTION section
-@set SUBSECTION subsection
-@set DARKCORNER (d.c.)
-@set COMMONEXT (c.e.)
-@set PAGE page
-@end ifplaintext
-
-@ifdocbook
-@c empty on purpose
-@set PART1
-@set PART2
-@set PART3
-@set PART4
-@end ifdocbook
-
-@ifnotdocbook
-@set PART1 Part I:@*
-@set PART2 Part II:@*
-@set PART3 Part III:@*
-@set PART4 Part IV:@*
-@end ifnotdocbook
-
-@c some special symbols
-@iftex
-@set LEQ @math{@leq}
-@set PI @math{@pi}
-@end iftex
-@iflatex
-@set LEQ <=
-@set PI @i{pi}
-@end iflatex
-@ifdocbook
-@set LEQ @inlineraw{docbook, ≤}
-@set PI @inlineraw{docbook, &pgr;}
-@end ifdocbook
-@ifnottex
-@ifnotdocbook
-@set LEQ <=
-@set PI @i{pi}
-@end ifnotdocbook
-@end ifnottex
-
-@ifnottex
-@ifnotdocbook
-@macro ii{text}
-@i{\text\}
-@end macro
-@end ifnotdocbook
-@end ifnottex
-
-@ifdocbook
-@macro ii{text}
-@inlineraw{docbook,<lineannotation>\text\</lineannotation>}
-@end macro
-@end ifdocbook
-
-@ifclear FOR_PRINT
-@set FN file name
-@set FFN File name
-@set DF data file
-@set DDF Data file
-@set PVERSION version
-@end ifclear
-@ifset FOR_PRINT
-@set FN filename
-@set FFN Filename
-@set DF datafile
-@set DDF Datafile
-@set PVERSION version
-@end ifset
-
-@c For HTML, spell out email addresses, to avoid problems with
-@c address harvesters for spammers.
-@ifhtml
-@macro EMAIL{real,spelled}
-``\spelled\''
-@end macro
-@end ifhtml
-@ifnothtml
-@macro EMAIL{real,spelled}
-@email{\real\}
-@end macro
-@end ifnothtml
-
-@c Indexing macros
-@ifinfo
-
-@macro cindexawkfunc{name}
-@cindex @code{\name\}
-@end macro
-
-@macro cindexgawkfunc{name}
-@cindex @code{\name\}
-@end macro
-
-@end ifinfo
-
-@ifnotinfo
-
-@macro cindexawkfunc{name}
-@cindex @code{\name\()} function
-@end macro
-
-@macro cindexgawkfunc{name}
-@cindex @code{\name\()} function (@command{gawk})
-@end macro
-@end ifnotinfo
-
-@ignore
-Some comments on the layout for TeX.
-1. Use at least texinfo.tex 2016-02-05.07.
-@end ignore
-
-@c merge the function and variable indexes into the concept index
-@ifinfo
-@synindex fn cp
-@synindex vr cp
-@end ifinfo
-@iftex
-@syncodeindex fn cp
-@syncodeindex vr cp
-@end iftex
-@iflatex
-@syncodeindex fn cp
-@syncodeindex vr cp
-@end iflatex
-@ifxml
-@syncodeindex fn cp
-@syncodeindex vr cp
-@end ifxml
-@ifdocbook
-@synindex fn cp
-@synindex vr cp
-@end ifdocbook
-
-@c If "finalout" is commented out, the printed output will show
-@c black boxes that mark lines that are too long. Thus, it is
-@c unwise to comment it out when running a master in case there are
-@c overfulls which are deemed okay.
-
-@iftex
-@finalout
-@end iftex
-@iflatex
-@finalout
-@end iflatex
-
-@c Enabled '-quotes in PDF files so that cut/paste works in
-@c more places.
-
-@codequoteundirected on
-@codequotebacktick on
-
-@copying
-@docbook
-<para>
-“To boldly go where no man has gone before” is a
-Registered Trademark of Paramount Pictures Corporation.</para>
-
-<para>Published by:</para>
-
-<literallayout class="normal">Free Software Foundation
-51 Franklin Street, Fifth Floor
-Boston, MA 02110-1301 USA
-Phone: +1-617-542-5942
-Fax: +1-617-542-2652
-Email: <email>gnu@@gnu.org</email>
-URL: <ulink
url="https://www.gnu.org";>https://www.gnu.org/</ulink></literallayout>
-
-<literallayout class="normal">Copyright © 1989, 1991, 1992, 1993,
1996–2005, 2007, 2009–2023
-Free Software Foundation, Inc.
-All Rights Reserved.</literallayout>
-@end docbook
-
-@ifnotdocbook
-Copyright @copyright{} 1989, 1991, 1992, 1993, 1996--2005, 2007, 2009--2023 @*
-Free Software Foundation, Inc.
-@end ifnotdocbook
-@sp 2
-
-This is Edition @value{EDITION} of @cite{@value{TITLE}: @value{SUBTITLE}},
-for the @value{VERSION}.@value{PATCHLEVEL} (or later) version of the GNU
-implementation of AWK.
-
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.3 or
-any later version published by the Free Software Foundation; with the
-Invariant Sections being ``GNU General Public License'', with the
-Front-Cover Texts being ``A GNU Manual'', and with the Back-Cover Texts
-as in (a) below.
-@ifclear FOR_PRINT
-A copy of the license is included in the section entitled
-``GNU Free Documentation License''.
-@end ifclear
-@ifset FOR_PRINT
-A copy of the license
-may be found on the Internet at
-@uref{https://www.gnu.org/software/gawk/manual/html_node/GNU-Free-Documentation-License.html,
-the GNU Project's website}.
-@end ifset
-
-@enumerate a
-@item
-The FSF's Back-Cover Text is: ``You have the freedom to
-copy and modify this GNU manual.''
-@end enumerate
-@end copying
-
-@c Comment out the "smallbook" for technical review. Saves
-@c considerable paper. Remember to turn it back on *before*
-@c starting the page-breaking work.
-
-@c 4/2002: Karl Berry recommends commenting out this and the
-@c `@setchapternewpage odd', and letting users use `texi2dvi -t'
-@c if they want to waste paper.
-@c @smallbook
-
-
-@c Uncomment this for the release. Leaving it off saves paper
-@c during editing and review.
-@setchapternewpage odd
-
-@shorttitlepage GNU Awk
-@titlepage
-@title @value{TITLE}
-@subtitle @value{SUBTITLE}
-@subtitle Edition @value{EDITION}
-@subtitle @value{UPDATE-MONTH}
-@author Arnold D. Robbins
-
-@ifnotdocbook
-@c Include the Distribution inside the titlepage environment so
-@c that headings are turned off. Headings on and off do not work.
-
-@page
-@vskip 0pt plus 1filll
-``To boldly go where no man has gone before'' is a
-Registered Trademark of Paramount Pictures Corporation. @*
-@c sorry, i couldn't resist
-@sp 3
-Published by:
-@sp 1
-
-Free Software Foundation @*
-51 Franklin Street, Fifth Floor @*
-Boston, MA 02110-1301 USA @*
-Phone: +1-617-542-5942 @*
-Fax: +1-617-542-2652 @*
-Email: @email{gnu@@gnu.org} @*
-URL: @uref{https://www.gnu.org/} @*
-
-@c This one is correct for gawk 3.1.0 from the FSF
-ISBN 1-882114-28-0 @*
-@sp 2
-@insertcopying
-@end ifnotdocbook
-@end titlepage
-
-@c Thanks to Bob Chassell for directions on doing dedications.
-@iftex
-@headings off
-@page
-@w{ }
-@sp 9
-@center @i{To my parents, for their love, and for the wonderful example they
set for me.}
-@sp 1
-@center @i{To my wife, Miriam, for making me complete.
-Thank you for building your life together with me.}
-@sp 1
-@center @i{To our children, Chana, Rivka, Nachum, and Malka, for enrichening
our lives in innumerable ways.}
-@sp 1
-@w{ }
-@page
-@w{ }
-@page
-@headings on
-@end iftex
-
-@docbook
-<dedication>
-<para>To my parents, for their love, and for the wonderful
-example they set for me.</para>
-<para>To my wife Miriam, for making me complete.
-Thank you for building your life together with me.</para>
-<para>To our children Chana, Rivka, Nachum and Malka,
-for enrichening our lives in innumerable ways.</para>
-</dedication>
-@end docbook
-
-@iftex
-@headings off
-@evenheading @thispage@ @ @ @strong{@value{TITLE}} @| @|
-@oddheading @| @| @strong{@thischapter}@ @ @ @thispage
-@end iftex
-
-@ifnottex
-@ifnotxml
-@ifnotdocbook
-@node Top
-@top General Introduction
-@c Preface node should come right after the Top
-@c node, in `unnumbered' sections, then the chapter, `What is gawk'.
-@c Licensing nodes are appendices, they're not central to AWK.
-
-This file documents @command{awk}, a program that you can use to select
-particular records in a file and perform operations upon them.
-
-@insertcopying
-
-@end ifnotdocbook
-@end ifnotxml
-@end ifnottex
-
-@menu
-* Foreword3:: Some nice words about this
- @value{DOCUMENT}.
-* Foreword4:: More nice words.
-* Preface:: What this @value{DOCUMENT} is about; brief
- history and acknowledgments.
-* Getting Started:: A basic introduction to using
- @command{awk}. How to run an @command{awk}
- program. Command-line syntax.
-* Invoking Gawk:: How to run @command{gawk}.
-* Regexp:: All about matching things using regular
- expressions.
-* Reading Files:: How to read files and manipulate fields.
-* Printing:: How to print using @command{awk}. Describes
- the @code{print} and @code{printf}
- statements. Also describes redirection of
- output.
-* Expressions:: Expressions are the basic building blocks
- of statements.
-* Patterns and Actions:: Overviews of patterns and actions.
-* Arrays:: The description and use of arrays. Also
- includes array-oriented control statements.
-* Functions:: Built-in and user-defined functions.
-* Library Functions:: A Library of @command{awk} Functions.
-* Sample Programs:: Many @command{awk} programs with complete
- explanations.
-* Advanced Features:: Stuff for advanced users, specific to
- @command{gawk}.
-* Internationalization:: Getting @command{gawk} to speak your
- language.
-* Debugger:: The @command{gawk} debugger.
-* Namespaces:: How namespaces work in @command{gawk}.
-* Arbitrary Precision Arithmetic:: Arbitrary precision arithmetic with
- @command{gawk}.
-* Dynamic Extensions:: Adding new built-in functions to
- @command{gawk}.
-* Language History:: The evolution of the @command{awk}
- language.
-* Installation:: Installing @command{gawk} under various
- operating systems.
-* Notes:: Notes about adding things to @command{gawk}
- and possible future work.
-* Basic Concepts:: A very quick introduction to programming
- concepts.
-* Glossary:: An explanation of some unfamiliar terms.
-* Copying:: Your right to copy and distribute
- @command{gawk}.
-* GNU Free Documentation License:: The license for this @value{DOCUMENT}.
-* Index:: Concept and Variable Index.
-
-@detailmenu
-* History:: The history of @command{gawk} and
- @command{awk}.
-* Names:: What name to use to find
- @command{awk}.
-* This Manual:: Using this @value{DOCUMENT}. Includes
- sample input files that you can use.
-* Conventions:: Typographical Conventions.
-* Manual History:: Brief history of the GNU project and
- this @value{DOCUMENT}.
-* How To Contribute:: Helping to save the world.
-* Acknowledgments:: Acknowledgments.
-* Running gawk:: How to run @command{gawk} programs;
- includes command-line syntax.
-* One-shot:: Running a short throwaway
- @command{awk} program.
-* Read Terminal:: Using no input files (input from the
- keyboard instead).
-* Long:: Putting permanent @command{awk}
- programs in files.
-* Executable Scripts:: Making self-contained @command{awk}
- programs.
-* Comments:: Adding documentation to @command{gawk}
- programs.
-* Quoting:: More discussion of shell quoting
- issues.
-* DOS Quoting:: Quoting in Windows Batch Files.
-* Sample Data Files:: Sample data files for use in the
- @command{awk} programs illustrated in
- this @value{DOCUMENT}.
-* Very Simple:: A very simple example.
-* Two Rules:: A less simple one-line example using
- two rules.
-* More Complex:: A more complex example.
-* Statements/Lines:: Subdividing or combining statements
- into lines.
-* Other Features:: Other Features of @command{awk}.
-* When:: When to use @command{gawk} and when to
- use other things.
-* Intro Summary:: Summary of the introduction.
-* Command Line:: How to run @command{awk}.
-* Options:: Command-line options and their
- meanings.
-* Other Arguments:: Input file names and variable
- assignments.
-* Naming Standard Input:: How to specify standard input with
- other files.
-* Environment Variables:: The environment variables
- @command{gawk} uses.
-* AWKPATH Variable:: Searching directories for
- @command{awk} programs.
-* AWKLIBPATH Variable:: Searching directories for
- @command{awk} shared libraries.
-* Other Environment Variables:: The environment variables.
-* Exit Status:: @command{gawk}'s exit status.
-* Include Files:: Including other files into your
- program.
-* Loading Shared Libraries:: Loading shared libraries into your
- program.
-* Obsolete:: Obsolete Options and/or features.
-* Undocumented:: Undocumented Options and Features.
-* Invoking Summary:: Invocation summary.
-* Regexp Usage:: How to Use Regular Expressions.
-* Escape Sequences:: How to write nonprinting characters.
-* Regexp Operators:: Regular Expression Operators.
-* Regexp Operator Details:: The actual details.
-* Interval Expressions:: Notes on interval expressions.
-* Bracket Expressions:: What can go between @samp{[...]}.
-* Leftmost Longest:: How much text matches.
-* Computed Regexps:: Using Dynamic Regexps.
-* GNU Regexp Operators:: Operators specific to GNU software.
-* Case-sensitivity:: How to do case-insensitive matching.
-* Regexp Summary:: Regular expressions summary.
-* Records:: Controlling how data is split into
- records.
-* awk split records:: How standard @command{awk} splits
- records.
-* gawk split records:: How @command{gawk} splits records.
-* Fields:: An introduction to fields.
-* Nonconstant Fields:: Nonconstant Field Numbers.
-* Changing Fields:: Changing the Contents of a Field.
-* Field Separators:: The field separator and how to change
- it.
-* Default Field Splitting:: How fields are normally separated.
-* Regexp Field Splitting:: Using regexps as the field separator.
-* Single Character Fields:: Making each character a separate
- field.
-* Comma Separated Fields:: Working with CSV files.
-* Command Line Field Separator:: Setting @code{FS} from the command
- line.
-* Full Line Fields:: Making the full line be a single
- field.
-* Field Splitting Summary:: Some final points and a summary table.
-* Constant Size:: Reading constant width data.
-* Fixed width data:: Processing fixed-width data.
-* Skipping intervening:: Skipping intervening fields.
-* Allowing trailing data:: Capturing optional trailing data.
-* Fields with fixed data:: Field values with fixed-width data.
-* Splitting By Content:: Defining Fields By Content
-* More CSV:: More on CSV files.
-* FS versus FPAT:: A subtle difference.
-* Testing field creation:: Checking how @command{gawk} is
- splitting records.
-* Multiple Line:: Reading multiline records.
-* Getline:: Reading files under explicit program
- control using the @code{getline}
- function.
-* Plain Getline:: Using @code{getline} with no
- arguments.
-* Getline/Variable:: Using @code{getline} into a variable.
-* Getline/File:: Using @code{getline} from a file.
-* Getline/Variable/File:: Using @code{getline} into a variable
- from a file.
-* Getline/Pipe:: Using @code{getline} from a pipe.
-* Getline/Variable/Pipe:: Using @code{getline} into a variable
- from a pipe.
-* Getline/Coprocess:: Using @code{getline} from a coprocess.
-* Getline/Variable/Coprocess:: Using @code{getline} into a variable
- from a coprocess.
-* Getline Notes:: Important things to know about
- @code{getline}.
-* Getline Summary:: Summary of @code{getline} Variants.
-* Read Timeout:: Reading input with a timeout.
-* Retrying Input:: Retrying input after certain errors.
-* Command-line directories:: What happens if you put a directory on
- the command line.
-* Input Summary:: Input summary.
-* Input Exercises:: Exercises.
-* Print:: The @code{print} statement.
-* Print Examples:: Simple examples of @code{print}
- statements.
-* Output Separators:: The output separators and how to
- change them.
-* OFMT:: Controlling Numeric Output With
- @code{print}.
-* Printf:: The @code{printf} statement.
-* Basic Printf:: Syntax of the @code{printf} statement.
-* Control Letters:: Format-control letters.
-* Format Modifiers:: Format-specification modifiers.
-* Printf Examples:: Several examples.
-* Redirection:: How to redirect output to multiple
- files and pipes.
-* Special FD:: Special files for I/O.
-* Special Files:: File name interpretation in
- @command{gawk}. @command{gawk} allows
- access to inherited file descriptors.
-* Other Inherited Files:: Accessing other open files with
- @command{gawk}.
-* Special Network:: Special files for network
- communications.
-* Special Caveats:: Things to watch out for.
-* Close Files And Pipes:: Closing Input and Output Files and
- Pipes.
-* Close Return Value:: Using the return value from
- @code{close()}.
-* Noflush:: Speeding Up Pipe Output.
-* Nonfatal:: Enabling Nonfatal Output.
-* Output Summary:: Output summary.
-* Output Exercises:: Exercises.
-* Values:: Constants, Variables, and Regular
- Expressions.
-* Constants:: String, numeric and regexp constants.
-* Scalar Constants:: Numeric and string constants.
-* Nondecimal-numbers:: What are octal and hex numbers.
-* Regexp Constants:: Regular Expression constants.
-* Using Constant Regexps:: When and how to use a regexp constant.
-* Standard Regexp Constants:: Regexp constants in standard
- @command{awk}.
-* Strong Regexp Constants:: Strongly typed regexp constants.
-* Variables:: Variables give names to values for
- later use.
-* Using Variables:: Using variables in your programs.
-* Assignment Options:: Setting variables on the command line
- and a summary of command-line syntax.
- This is an advanced method of input.
-* Conversion:: The conversion of strings to numbers
- and vice versa.
-* Strings And Numbers:: How @command{awk} Converts Between
- Strings And Numbers.
-* Locale influences conversions:: How the locale may affect conversions.
-* All Operators:: @command{gawk}'s operators.
-* Arithmetic Ops:: Arithmetic operations (@samp{+},
- @samp{-}, etc.)
-* Concatenation:: Concatenating strings.
-* Assignment Ops:: Changing the value of a variable or a
- field.
-* Increment Ops:: Incrementing the numeric value of a
- variable.
-* Truth Values and Conditions:: Testing for true and false.
-* Truth Values:: What is ``true'' and what is
- ``false''.
-* Typing and Comparison:: How variables acquire types and how
- this affects comparison of numbers and
- strings with @samp{<}, etc.
-* Variable Typing:: String type versus numeric type.
-* Comparison Operators:: The comparison operators.
-* POSIX String Comparison:: String comparison with POSIX rules.
-* Boolean Ops:: Combining comparison expressions using
- boolean operators @samp{||} (``or''),
- @samp{&&} (``and'') and @samp{!}
- (``not'').
-* Conditional Exp:: Conditional expressions select between
- two subexpressions under control of a
- third subexpression.
-* Function Calls:: A function call is an expression.
-* Precedence:: How various operators nest.
-* Locales:: How the locale affects things.
-* Expressions Summary:: Expressions summary.
-* Pattern Overview:: What goes into a pattern.
-* Regexp Patterns:: Using regexps as patterns.
-* Expression Patterns:: Any expression can be used as a
- pattern.
-* Ranges:: Pairs of patterns specify record
- ranges.
-* BEGIN/END:: Specifying initialization and cleanup
- rules.
-* Using BEGIN/END:: How and why to use BEGIN/END rules.
-* I/O And BEGIN/END:: I/O issues in BEGIN/END rules.
-* BEGINFILE/ENDFILE:: Two special patterns for advanced
- control.
-* Empty:: The empty pattern, which matches every
- record.
-* Using Shell Variables:: How to use shell variables with
- @command{awk}.
-* Action Overview:: What goes into an action.
-* Statements:: Describes the various control
- statements in detail.
-* If Statement:: Conditionally execute some
- @command{awk} statements.
-* While Statement:: Loop until some condition is
- satisfied.
-* Do Statement:: Do specified action while looping
- until some condition is satisfied.
-* For Statement:: Another looping statement, that
- provides initialization and increment
- clauses.
-* Switch Statement:: Switch/case evaluation for conditional
- execution of statements based on a
- value.
-* Break Statement:: Immediately exit the innermost
- enclosing loop.
-* Continue Statement:: Skip to the end of the innermost
- enclosing loop.
-* Next Statement:: Stop processing the current input
- record.
-* Nextfile Statement:: Stop processing the current file.
-* Exit Statement:: Stop execution of @command{awk}.
-* Built-in Variables:: Summarizes the predefined variables.
-* User-modified:: Built-in variables that you change to
- control @command{awk}.
-* Auto-set:: Built-in variables where @command{awk}
- gives you information.
-* ARGC and ARGV:: Ways to use @code{ARGC} and
- @code{ARGV}.
-* Pattern Action Summary:: Patterns and Actions summary.
-* Array Basics:: The basics of arrays.
-* Array Intro:: Introduction to Arrays
-* Reference to Elements:: How to examine one element of an
- array.
-* Assigning Elements:: How to change an element of an array.
-* Array Example:: Basic Example of an Array
-* Scanning an Array:: A variation of the @code{for}
- statement. It loops through the
- indices of an array's existing
- elements.
-* Controlling Scanning:: Controlling the order in which arrays
- are scanned.
-* Numeric Array Subscripts:: How to use numbers as subscripts in
- @command{awk}.
-* Uninitialized Subscripts:: Using Uninitialized variables as
- subscripts.
-* Delete:: The @code{delete} statement removes an
- element from an array.
-* Multidimensional:: Emulating multidimensional arrays in
- @command{awk}.
-* Multiscanning:: Scanning multidimensional arrays.
-* Arrays of Arrays:: True multidimensional arrays.
-* Arrays Summary:: Summary of arrays.
-* Built-in:: Summarizes the built-in functions.
-* Calling Built-in:: How to call built-in functions.
-* Boolean Functions:: A function that returns Boolean
- values.
-* Numeric Functions:: Functions that work with numbers,
- including @code{int()}, @code{sin()}
- and @code{rand()}.
-* String Functions:: Functions for string manipulation,
- such as @code{split()}, @code{match()}
- and @code{sprintf()}.
-* Gory Details:: More than you want to know about
- @samp{\} and @samp{&} with
- @code{sub()}, @code{gsub()}, and
- @code{gensub()}.
-* I/O Functions:: Functions for files and shell
- commands.
-* Time Functions:: Functions for dealing with timestamps.
-* Bitwise Functions:: Functions for bitwise operations.
-* Type Functions:: Functions for type information.
-* I18N Functions:: Functions for string translation.
-* User-defined:: Describes User-defined functions in
- detail.
-* Definition Syntax:: How to write definitions and what they
- mean.
-* Function Example:: An example function definition and
- what it does.
-* Function Calling:: Calling user-defined functions.
-* Calling A Function:: Don't use spaces.
-* Variable Scope:: Controlling variable scope.
-* Pass By Value/Reference:: Passing parameters.
-* Function Caveats:: Other points to know about functions.
-* Return Statement:: Specifying the value a function
- returns.
-* Dynamic Typing:: How variable types can change at
- runtime.
-* Indirect Calls:: Choosing the function to call at
- runtime.
-* Functions Summary:: Summary of functions.
-* Library Names:: How to best name private global
- variables in library functions.
-* General Functions:: Functions that are of general use.
-* Strtonum Function:: A replacement for the built-in
- @code{strtonum()} function.
-* Assert Function:: A function for assertions in
- @command{awk} programs.
-* Round Function:: A function for rounding if
- @code{sprintf()} does not do it
- correctly.
-* Cliff Random Function:: The Cliff Random Number Generator.
-* Ordinal Functions:: Functions for using characters as
- numbers and vice versa.
-* Join Function:: A function to join an array into a
- string.
-* Getlocaltime Function:: A function to get formatted times.
-* Readfile Function:: A function to read an entire file at
- once.
-* Shell Quoting:: A function to quote strings for the
- shell.
-* Isnumeric Function:: A function to test whether a value is
- numeric.
-* To CSV Function:: A function to convert output to CSV
- format.
-* Data File Management:: Functions for managing command-line
- data files.
-* Filetrans Function:: A function for handling data file
- transitions.
-* Rewind Function:: A function for rereading the current
- file.
-* File Checking:: Checking that data files are readable.
-* Empty Files:: Checking for zero-length files.
-* Ignoring Assigns:: Treating assignments as file names.
-* Getopt Function:: A function for processing command-line
- arguments.
-* Passwd Functions:: Functions for getting user
- information.
-* Group Functions:: Functions for getting group
- information.
-* Walking Arrays:: A function to walk arrays of arrays.
-* Library Functions Summary:: Summary of library functions.
-* Library Exercises:: Exercises.
-* Running Examples:: How to run these examples.
-* Clones:: Clones of common utilities.
-* Cut Program:: The @command{cut} utility.
-* Egrep Program:: The @command{egrep} utility.
-* Id Program:: The @command{id} utility.
-* Split Program:: The @command{split} utility.
-* Tee Program:: The @command{tee} utility.
-* Uniq Program:: The @command{uniq} utility.
-* Wc Program:: The @command{wc} utility.
-* Bytes vs. Characters:: Modern character sets.
-* Using extensions:: A brief intro to extensions.
-* @command{wc} program:: Code for @file{wc.awk}.
-* Miscellaneous Programs:: Some interesting @command{awk}
- programs.
-* Dupword Program:: Finding duplicated words in a
- document.
-* Alarm Program:: An alarm clock.
-* Translate Program:: A program similar to the @command{tr}
- utility.
-* Labels Program:: Printing mailing labels.
-* Word Sorting:: A program to produce a word usage
- count.
-* History Sorting:: Eliminating duplicate entries from a
- history file.
-* Extract Program:: Pulling out programs from Texinfo
- source files.
-* Simple Sed:: A Simple Stream Editor.
-* Igawk Program:: A wrapper for @command{awk} that
- includes files.
-* Anagram Program:: Finding anagrams from a dictionary.
-* Signature Program:: People do amazing things with too much
- time on their hands.
-* Programs Summary:: Summary of programs.
-* Programs Exercises:: Exercises.
-* Nondecimal Data:: Allowing nondecimal input data.
-* Boolean Typed Values:: Values with @code{number|bool} type.
-* Array Sorting:: Facilities for controlling array
- traversal and sorting arrays.
-* Controlling Array Traversal:: How to use PROCINFO["sorted_in"].
-* Array Sorting Functions:: How to use @code{asort()} and
- @code{asorti()}.
-* Two-way I/O:: Two-way communications with another
- process.
-* TCP/IP Networking:: Using @command{gawk} for network
- programming.
-* Profiling:: Profiling your @command{awk} programs.
-* Persistent Memory:: Preserving data between runs.
-* Extension Philosophy:: What should be built-in and what
- should not.
-* Advanced Features Summary:: Summary of advanced features.
-* I18N and L10N:: Internationalization and Localization.
-* Explaining gettext:: How GNU @command{gettext} works.
-* Programmer i18n:: Features for the programmer.
-* Translator i18n:: Features for the translator.
-* String Extraction:: Extracting marked strings.
-* Printf Ordering:: Rearranging @code{printf} arguments.
-* I18N Portability:: @command{awk}-level portability
- issues.
-* I18N Example:: A simple i18n example.
-* Gawk I18N:: @command{gawk} is also
- internationalized.
-* I18N Summary:: Summary of I18N stuff.
-* Debugging:: Introduction to @command{gawk}
- debugger.
-* Debugging Concepts:: Debugging in General.
-* Debugging Terms:: Additional Debugging Concepts.
-* Awk Debugging:: Awk Debugging.
-* Sample Debugging Session:: Sample debugging session.
-* Debugger Invocation:: How to Start the Debugger.
-* Finding The Bug:: Finding the Bug.
-* List of Debugger Commands:: Main debugger commands.
-* Breakpoint Control:: Control of Breakpoints.
-* Debugger Execution Control:: Control of Execution.
-* Viewing And Changing Data:: Viewing and Changing Data.
-* Execution Stack:: Dealing with the Stack.
-* Debugger Info:: Obtaining Information about the
- Program and the Debugger State.
-* Miscellaneous Debugger Commands:: Miscellaneous Commands.
-* Readline Support:: Readline support.
-* Limitations:: Limitations and future plans.
-* Debugging Summary:: Debugging summary.
-* Global Namespace:: The global namespace in standard
- @command{awk}.
-* Qualified Names:: How to qualify names with a namespace.
-* Default Namespace:: The default namespace.
-* Changing The Namespace:: How to change the namespace.
-* Naming Rules:: Namespace and Component Naming Rules.
-* Internal Name Management:: How names are stored internally.
-* Namespace Example:: An example of code using a namespace.
-* Namespace And Features:: Namespaces and other @command{gawk}
- features.
-* Namespace Summary:: Summarizing namespaces.
-* Computer Arithmetic:: A quick intro to computer math.
-* Math Definitions:: Defining terms used.
-* MPFR features:: The MPFR features in @command{gawk}.
-* MPFR On Parole:: MPFR features are on parole!
-* MPFR Intro:: MPFR General introduction.
-* FP Math Caution:: Things to know.
-* Inexactness of computations:: Floating point math is not exact.
-* Inexact representation:: Numbers are not exactly represented.
-* Comparing FP Values:: How to compare floating point values.
-* Errors accumulate:: Errors get bigger as they go.
-* Strange values:: A few words about infinities and NaNs.
-* Getting Accuracy:: Getting more accuracy takes some work.
-* Try To Round:: Add digits and round.
-* Setting precision:: How to set the precision.
-* Setting the rounding mode:: How to set the rounding mode.
-* Arbitrary Precision Integers:: Arbitrary Precision Integer Arithmetic
- with @command{gawk}.
-* Checking for MPFR:: How to check if MPFR is available.
-* POSIX Floating Point Problems:: Standards Versus Existing Practice.
-* Floating point summary:: Summary of floating point discussion.
-* Extension Intro:: What is an extension.
-* Plugin License:: A note about licensing.
-* Extension Mechanism Outline:: An outline of how it works.
-* Extension API Description:: A full description of the API.
-* Extension API Functions Introduction:: Introduction to the API functions.
-* General Data Types:: The data types.
-* Memory Allocation Functions:: Functions for allocating memory.
-* Constructor Functions:: Functions for creating values.
-* API Ownership of MPFR and GMP Values:: Managing MPFR and GMP Values.
-* Registration Functions:: Functions to register things with
- @command{gawk}.
-* Extension Functions:: Registering extension functions.
-* Exit Callback Functions:: Registering an exit callback.
-* Extension Version String:: Registering a version string.
-* Input Parsers:: Registering an input parser.
-* Output Wrappers:: Registering an output wrapper.
-* Two-way processors:: Registering a two-way processor.
-* Printing Messages:: Functions for printing messages.
-* Updating @code{ERRNO}:: Functions for updating @code{ERRNO}.
-* Requesting Values:: How to get a value.
-* Accessing Parameters:: Functions for accessing parameters.
-* Symbol Table Access:: Functions for accessing global
- variables.
-* Symbol table by name:: Accessing variables by name.
-* Symbol table by cookie:: Accessing variables by ``cookie''.
-* Cached values:: Creating and using cached values.
-* Array Manipulation:: Functions for working with arrays.
-* Array Data Types:: Data types for working with arrays.
-* Array Functions:: Functions for working with arrays.
-* Flattening Arrays:: How to flatten arrays.
-* Creating Arrays:: How to create and populate arrays.
-* Redirection API:: How to access and manipulate
- redirections.
-* Extension API Variables:: Variables provided by the API.
-* Extension Versioning:: API Version information.
-* Extension GMP/MPFR Versioning:: Version information about GMP and
- MPFR.
-* Extension API Informational Variables:: Variables providing information about
- @command{gawk}'s invocation.
-* Extension API Boilerplate:: Boilerplate code for using the API.
-* Changes from API V1:: Changes from V1 of the API.
-* Finding Extensions:: How @command{gawk} finds compiled
- extensions.
-* Extension Example:: Example C code for an extension.
-* Internal File Description:: What the new functions will do.
-* Internal File Ops:: The code for internal file operations.
-* Using Internal File Ops:: How to use an external extension.
-* Extension Samples:: The sample extensions that ship with
- @command{gawk}.
-* Extension Sample File Functions:: The file functions sample.
-* Extension Sample Fnmatch:: An interface to @code{fnmatch()}.
-* Extension Sample Fork:: An interface to @code{fork()} and
- other process functions.
-* Extension Sample Inplace:: Enabling in-place file editing.
-* Extension Sample Ord:: Character to value to character
- conversions.
-* Extension Sample Readdir:: An interface to @code{readdir()}.
-* Extension Sample Revout:: Reversing output sample output
- wrapper.
-* Extension Sample Rev2way:: Reversing data sample two-way
- processor.
-* Extension Sample Read write array:: Serializing an array to a file.
-* Extension Sample Readfile:: Reading an entire file into a string.
-* Extension Sample Time:: An interface to @code{gettimeofday()}
- and @code{sleep()}.
-* Extension Sample API Tests:: Tests for the API.
-* gawkextlib:: The @code{gawkextlib} project.
-* Extension summary:: Extension summary.
-* Extension Exercises:: Exercises.
-* V7/SVR3.1:: The major changes between V7 and
- System V Release 3.1.
-* SVR4:: Minor changes between System V
- Releases 3.1 and 4.
-* POSIX:: New features from the POSIX standard.
-* BTL:: New features from Brian Kernighan's
- version of @command{awk}.
-* POSIX/GNU:: The extensions in @command{gawk} not
- in POSIX @command{awk}.
-* Feature History:: The history of the features in
- @command{gawk}.
-* Common Extensions:: Common Extensions Summary.
-* Ranges and Locales:: How locales used to affect regexp
- ranges.
-* Contributors:: The major contributors to
- @command{gawk}.
-* History summary:: History summary.
-* Gawk Distribution:: What is in the @command{gawk}
- distribution.
-* Getting:: How to get the distribution.
-* Extracting:: How to extract the distribution.
-* Distribution contents:: What is in the distribution.
-* Unix Installation:: Installing @command{gawk} under
- various versions of Unix.
-* Quick Installation:: Compiling @command{gawk} under Unix.
-* Compiling with MPFR:: Building with MPFR.
-* Shell Startup Files:: Shell convenience functions.
-* Additional Configuration Options:: Other compile-time options.
-* Configuration Philosophy:: How it's all supposed to work.
-* Compiling from Git:: Compiling from Git.
-* Building the Documentation:: Building the Documentation.
-* Non-Unix Installation:: Installation on Other Operating
- Systems.
-* PC Installation:: Installing and Compiling
- @command{gawk} on Microsoft Windows.
-* PC Binary Installation:: Installing a prepared distribution.
-* PC Compiling:: Compiling @command{gawk} for
- Windows32.
-* PC Using:: Running @command{gawk} on Windows32.
-* Cygwin:: Building and running @command{gawk}
- for Cygwin.
-* MSYS:: Using @command{gawk} In The MSYS
- Environment.
-* OpenVMS Installation:: Installing @command{gawk} on OpenVMS.
-* OpenVMS Compilation:: How to compile @command{gawk} under
- OpenVMS.
-* OpenVMS Dynamic Extensions:: Compiling @command{gawk} dynamic
- extensions on OpenVMS.
-* OpenVMS Installation Details:: How to install @command{gawk} under
- OpenVMS.
-* OpenVMS Running:: How to run @command{gawk} under
- OpenVMS.
-* OpenVMS GNV:: The OpenVMS GNV Project.
-* Bugs:: Reporting Problems and Bugs.
-* Bug definition:: Defining what is and is not a bug.
-* Bug address:: Where to send reports to.
-* Usenet:: Where not to send reports to.
-* Performance bugs:: What to do if you think there is a
- performance issue.
-* Asking for help:: Dealing with non-bug questions.
-* Maintainers:: Maintainers of non-*nix ports.
-* Other Versions:: Other freely available @command{awk}
- implementations.
-* Installation summary:: Summary of installation.
-* Compatibility Mode:: How to disable certain @command{gawk}
- extensions.
-* Additions:: Making Additions To @command{gawk}.
-* Accessing The Source:: Accessing the Git repository.
-* Adding Code:: Adding code to the main body of
- @command{gawk}.
-* New Ports:: Porting @command{gawk} to a new
- operating system.
-* Derived Files:: Why derived files are kept in the Git
- repository.
-* Future Extensions:: New features that may be implemented
- one day.
-* Implementation Limitations:: Some limitations of the
- implementation.
-* Extension Design:: Design notes about the extension API.
-* Old Extension Problems:: Problems with the old mechanism.
-* Extension New Mechanism Goals:: Goals for the new mechanism.
-* Extension Other Design Decisions:: Some other design decisions.
-* Extension Future Growth:: Some room for future growth.
-* Notes summary:: Summary of implementation notes.
-* Basic High Level:: The high level view.
-* Basic Data Typing:: A very quick intro to data types.
-@end detailmenu
-@end menu
-
-@c dedication for Info file
-@ifinfo
-To my parents, for their love, and for the wonderful
-example they set for me.
-@sp 1
-To my wife Miriam, for making me complete.
-Thank you for building your life together with me.
-@sp 1
-To our children Chana, Rivka, Nachum and Malka,
-for enrichening our lives in innumerable ways.
-@end ifinfo
-
-@summarycontents
-@contents
-
-@node Foreword3
-@unnumbered Foreword to the Third Edition
-
-@c This bit is post-processed by a script which turns the chapter
-@c tag into a preface tag, and moves this stuff to before the title.
-@c Bleah.
-@docbook
- <prefaceinfo>
- <author>
- <firstname>Michael</firstname>
- <surname>Brennan</surname>
- <!-- can't put mawk into command tags. sigh. -->
- <affiliation><jobtitle>Author of mawk</jobtitle></affiliation>
- </author>
- <date>March 2001</date>
- </prefaceinfo>
-@end docbook
-
-Arnold Robbins and I are good friends. We were introduced
-@c 11 years ago
-in 1990
-by circumstances---and our favorite programming language, AWK.
-The circumstances started a couple of years
-earlier. I was working at a new job and noticed an unplugged
-Unix computer sitting in the corner. No one knew how to use it,
-and neither did I. However,
-a couple of days later, it was running, and
-I was @code{root} and the one-and-only user.
-That day, I began the transition from statistician to Unix programmer.
-
-On one of many trips to the library or bookstore in search of
-books on Unix, I found the gray AWK book, a.k.a.@:
-Alfred V.@: Aho, Brian W.@: Kernighan, and
-Peter J.@: Weinberger's @cite{The AWK Programming Language} (Addison-Wesley,
-1988). @command{awk}'s simple programming paradigm---find a pattern in the
-input and then perform an action---often reduced complex or tedious
-data manipulations to a few lines of code. I was excited to try my
-hand at programming in AWK.
-
-Alas, the @command{awk} on my computer was a limited version of the
-language described in the gray book. I discovered that my computer
-had ``old @command{awk}'' and the book described
-``new @command{awk}.''
-I learned that this was typical; the old version refused to step
-aside or relinquish its name. If a system had a new @command{awk}, it was
-invariably called @command{nawk}, and few systems had it.
-The best way to get a new @command{awk} was to @command{ftp} the source code
for
-@command{gawk} from @code{prep.ai.mit.edu}. @command{gawk} was a version of
-new @command{awk} written by David Trueman and Arnold, and available under
-the GNU General Public License.
-
-(Incidentally,
-it's no longer difficult to find a new @command{awk}. @command{gawk} ships with
-GNU/Linux, and you can download binaries or source code for almost
-any system; my wife uses @command{gawk} on her VMS box.)
-
-My Unix system started out unplugged from the wall; it certainly was not
-plugged into a network. So, oblivious to the existence of @command{gawk}
-and the Unix community in general, and desiring a new @command{awk}, I wrote
-my own, called @command{mawk}.
-Before I was finished, I knew about @command{gawk},
-but it was too late to stop, so I eventually posted
-to a @code{comp.sources} newsgroup.
-
-A few days after my posting, I got a friendly email
-from Arnold introducing
-himself. He suggested we share design and algorithms and
-attached a draft of the POSIX standard so
-that I could update @command{mawk} to support language extensions added
-after publication of @cite{The AWK Programming Language}.
-
-Frankly, if our roles had
-been reversed, I would not have been so open and we probably would
-have never met. I'm glad we did meet.
-He is an AWK expert's AWK expert and a genuinely nice person.
-Arnold contributes significant amounts of his
-expertise and time to the Free Software Foundation.
-
-This book is the @command{gawk} reference manual, but at its core it
-is a book about AWK programming that
-will appeal to a wide audience.
-It is a definitive reference to the AWK language as defined by the
-1987 Bell Laboratories release and codified in the 1992 POSIX Utilities
-standard.
-
-On the other hand, the novice AWK programmer can study
-a wealth of practical programs that emphasize
-the power of AWK's basic idioms:
-data-driven control flow, pattern matching with regular expressions,
-and associative arrays.
-Those looking for something new can try out @command{gawk}'s
-interface to network protocols via special @file{/inet} files.
-
-The programs in this book make clear that an AWK program is
-typically much smaller and faster to develop than
-a counterpart written in C.
-Consequently, there is often a payoff to prototyping an
-algorithm or design in AWK to get it running quickly and expose
-problems early. Often, the interpreted performance is adequate
-and the AWK prototype becomes the product.
-
-The new @command{pgawk} (profiling @command{gawk}), produces
-program execution counts.
-I recently experimented with an algorithm that for
-@ifnotdocbook
-@math{n}
-@end ifnotdocbook
-@ifdocbook
-@i{n}
-@end ifdocbook
-lines of input, exhibited
-@tex
-$\sim\! Cn^2$
-@end tex
-@ifnottex
-@ifnotdocbook
-~ C n^2
-@end ifnotdocbook
-@end ifnottex
-@docbook
-<emphasis>∼ Cn<superscript>2</superscript></emphasis>
-@end docbook
-performance, while
-theory predicted
-@tex
-$\sim\! Cn\log n$
-@end tex
-@ifnottex
-@ifnotdocbook
-~ C n log n
-@end ifnotdocbook
-@end ifnottex
-@docbook
-<emphasis>∼ Cn log n</emphasis>
-@end docbook
-behavior. A few minutes poring
-over the @file{awkprof.out} profile pinpointed the problem to
-a single line of code. @command{pgawk} is a welcome addition to
-my programmer's toolbox.
-
-Arnold has distilled over a decade of experience writing and
-using AWK programs, and developing @command{gawk}, into this book. If you use
-AWK or want to learn how, then read this book.
-
-@ifnotdocbook
-@cindex Brennan, Michael
-@display
-Michael Brennan
-Author of @command{mawk}
-March 2001
-@end display
-@end ifnotdocbook
-
-@node Foreword4
-@unnumbered Foreword to the Fourth Edition
-
-@c This bit is post-processed by a script which turns the chapter
-@c tag into a preface tag, and moves this stuff to before the title.
-@c Bleah.
-@docbook
- <prefaceinfo>
- <author>
- <firstname>Michael</firstname>
- <surname>Brennan</surname>
- <!-- can't put mawk into command tags. sigh. -->
- <affiliation><jobtitle>Author of mawk</jobtitle></affiliation>
- </author>
- <date>October 2014</date>
- </prefaceinfo>
-@end docbook
-
-Some things don't change. Thirteen years ago I wrote:
-``If you use AWK or want to learn how, then read this book.''
-True then, and still true today.
-
-Learning to use a programming language is about more than mastering the
-syntax. One needs to acquire an understanding of how to use the
-features of the language to solve practical programming problems.
-A focus of this book is many examples that show how to use AWK.
-
-Some things do change. Our computers are much faster and have more memory.
-Consequently, speed and storage inefficiencies of a high-level language
-matter less. Prototyping in AWK and then rewriting in C for performance
-reasons happens less, because more often the prototype is fast enough.
-
-Of course, there are computing operations that are best done in C or C++.
-With @command{gawk} 4.1 and later, you do not have to choose between writing
-your program in AWK or in C/C++. You can write most of your
-program in AWK and the aspects that require C/C++ capabilities can be written
-in C/C++, and then the pieces glued together when the @command{gawk} module
loads
-the C/C++ module as a dynamic plug-in.
-@c Chapter 16
-@ref{Dynamic Extensions},
-has all the
-details, and, as expected, many examples to help you learn the ins and outs.
-
-I enjoy programming in AWK and had fun (re)reading this book.
-I think you will too.
-
-@ifnotdocbook
-@cindex Brennan, Michael
-@display
-Michael Brennan
-Author of @command{mawk}
-October 2014
-@end display
-@end ifnotdocbook
-
-@node Preface
-@unnumbered Preface
-@c I saw a comment somewhere that the preface should describe the book itself,
-@c and the introduction should describe what the book covers.
-@c
-@c 12/2000: Chuck wants the preface & intro combined.
-
-@c This bit is post-processed by a script which turns the chapter
-@c tag into a preface tag, and moves this stuff to before the title.
-@c Bleah.
-@docbook
- <prefaceinfo>
- <author>
- <firstname>Arnold</firstname>
- <surname>Robbins</surname>
- <affiliation><jobtitle>Nof Ayalon</jobtitle></affiliation>
- <affiliation><jobtitle>Israel</jobtitle></affiliation>
- </author>
- <date>February 2015</date>
- </prefaceinfo>
-@end docbook
-
-@cindex @command{awk}
-Several kinds of tasks occur repeatedly when working with text files.
-You might want to extract certain lines and discard the rest. Or you
-may need to make changes wherever certain patterns appear, but leave the
-rest of the file alone. Such jobs are often easy with @command{awk}.
-The @command{awk} utility interprets a special-purpose programming
-language that makes it easy to handle simple data-reformatting jobs.
-
-@cindex @command{gawk}
-The GNU implementation of @command{awk} is called @command{gawk}; if you
-invoke it with the proper options or environment variables,
-it is fully compatible with
-the POSIX@footnote{The 2018 POSIX standard is accessible online at
-@w{@url{https://pubs.opengroup.org/onlinepubs/9699919799/}.}}
-specification of the @command{awk} language
-and with the Unix version of @command{awk} maintained
-by Brian Kernighan.
-This means that all
-properly written @command{awk} programs should work with @command{gawk}.
-So most of the time, we don't distinguish between @command{gawk} and other
-@command{awk} implementations.
-
-@cindex @command{awk} @subentry POSIX and @seealso{POSIX @command{awk}}
-@cindex @command{awk} @subentry POSIX and
-@cindex POSIX @subentry @command{awk} and
-@cindex @command{gawk} @subentry @command{awk} and
-@cindex @command{awk} @subentry @command{gawk} and
-@cindex @command{awk} @subentry uses for
-Using @command{awk} you can:
-
-@itemize @value{BULLET}
-@item
-Manage small, personal databases
-
-@item
-Generate reports
-
-@item
-Validate data
-
-@item
-Produce indexes and perform other document-preparation tasks
-
-@item
-Experiment with algorithms that you can adapt later to other computer
-languages
-@end itemize
-
-@cindex @command{awk} @seealso{@command{gawk}}
-@cindex @command{gawk} @seealso{@command{awk}}
-@cindex @command{gawk} @subentry uses for
-In addition,
-@command{gawk}
-provides facilities that make it easy to:
-
-@itemize @value{BULLET}
-@item
-Extract bits and pieces of data for processing
-
-@item
-Sort data
-
-@item
-Perform simple network communications
-
-@item
-Profile and debug @command{awk} programs
-
-@item
-Extend the language with functions written in C or C++
-@end itemize
-
-This @value{DOCUMENT} teaches you about the @command{awk} language and
-how you can use it effectively. You should already be familiar with basic
-system commands, such as @command{cat} and @command{ls},@footnote{These
utilities
-are available on POSIX-compliant systems, as well as on traditional
-Unix-based systems. If you are using some other operating system, you still
need to
-be familiar with the ideas of I/O redirection and pipes.} as well as basic
shell
-facilities, such as input/output (I/O) redirection and pipes.
-
-@cindex GNU @command{awk} @seeentry{@command{gawk}}
-Implementations of the @command{awk} language are available for many
-different computing environments. This @value{DOCUMENT}, while describing
-the @command{awk} language in general, also describes the particular
-implementation of @command{awk} called @command{gawk} (which stands for
-``GNU @command{awk}''). @command{gawk} runs on a broad range of Unix systems,
-ranging from Intel-architecture PC-based computers
-up through large-scale systems.
-@command{gawk} has also been ported to macOS, z/OS,
-Microsoft Windows
-(all versions),
-and OpenVMS.@footnote{Some other, obsolete systems to which @command{gawk}
-was once ported are no longer supported and the code for those systems
-has been removed.}
-
-@menu
-* History:: The history of @command{gawk} and
- @command{awk}.
-* Names:: What name to use to find @command{awk}.
-* This Manual:: Using this @value{DOCUMENT}. Includes sample
- input files that you can use.
-* Conventions:: Typographical Conventions.
-* Manual History:: Brief history of the GNU project and this
- @value{DOCUMENT}.
-* How To Contribute:: Helping to save the world.
-* Acknowledgments:: Acknowledgments.
-@end menu
-
-@node History
-@unnumberedsec History of @command{awk} and @command{gawk}
-@cindex recipe for a programming language
-@cindex programming language, recipe for
-@sidebar Recipe for a Programming Language
-
-@multitable {2 parts} {1 part @code{egrep}} {1 part @code{snobol}}
-@item @tab 1 part @code{egrep} @tab 1 part @code{snobol}
-@item @tab 2 parts @code{ed} @tab 3 parts C
-@end multitable
-
-Blend all parts well using @code{lex} and @code{yacc}.
-Document minimally and release.
-
-After eight years, add another part @code{egrep} and two
-more parts C. Document very well and release.
-
-After 35 more years, add Unicode and CSV support, sprinkle lightly with
-a few choice features from @command{gawk}, document very well again,
-and release.
-@end sidebar
-
-@cindex Aho, Alfred
-@cindex Weinberger, Peter
-@cindex Kernighan, Brian
-@cindex @command{awk} @subentry history of
-The name @command{awk} comes from the initials of its designers: Alfred V.@:
-Aho, Peter J.@: Weinberger, and Brian W.@: Kernighan. The original version of
-@command{awk} was written in 1977 at AT&T Bell Laboratories.
-In 1985, a new version made the programming
-language more powerful, introducing user-defined functions, multiple input
-streams, and computed regular expressions.
-This new version became widely available with Unix System V
-Release 3.1 (1987).
-The version in System V Release 4 (1989) added some new features and cleaned
-up the behavior in some of the ``dark corners'' of the language.
-The specification for @command{awk} in the POSIX Command Language
-and Utilities standard further clarified the language.
-Both the @command{gawk} designers and the original @command{awk} designers at
Bell Laboratories
-provided feedback for the POSIX specification.
-
-@cindex Rubin, Paul
-@cindex Fenlason, Jay
-@cindex Trueman, David
-Paul Rubin wrote @command{gawk} in 1986.
-Jay Fenlason completed it, with advice from Richard Stallman. John Woods
-contributed parts of the code as well. In 1988 and 1989, David Trueman, with
-help from me, thoroughly reworked @command{gawk} for compatibility
-with the newer @command{awk}.
-Circa 1994, I became the primary maintainer.
-Current development focuses on bug fixes,
-performance improvements, standards compliance, and, occasionally, new
features.
-
-In May 1997, J@"urgen Kahrs felt the need for network access
-from @command{awk}, and with a little help from me, set about adding
-features to do this for @command{gawk}. At that time, he also
-wrote the bulk of
-@cite{@value{GAWKINETTITLE}}
-(a separate document, available as part of the @command{gawk} distribution).
-His code finally became part of the main @command{gawk} distribution
-with @command{gawk} @value{PVERSION} 3.1.
-
-John Haque rewrote the @command{gawk} internals, in the process providing
-an @command{awk}-level debugger. This version became available as
-@command{gawk} @value{PVERSION} 4.0 in 2011.
-
-@xref{Contributors}
-for a full list of those who have made important contributions to
@command{gawk}.
-
-@node Names
-@unnumberedsec A Rose by Any Other Name
-
-@cindex @command{awk} @subentry new vs.@: old
-The @command{awk} language has evolved over the years. Full details are
-provided in @ref{Language History}.
-The language described in this @value{DOCUMENT}
-is often referred to as ``new @command{awk}.''
-By analogy, the original version of @command{awk} is
-referred to as ``old @command{awk}.''
-
-On most current systems, when you run the @command{awk} utility
-you get some version of new @command{awk}.@footnote{Only
-Solaris systems still use an old @command{awk} for the
-default @command{awk} utility. A more modern @command{awk} lives in
-@file{/usr/xpg6/bin} on these systems.} If your system's standard
-@command{awk} is the old one, you will see something like this
-if you try the following test program:
-
-@example
-@group
-$ @kbd{awk 1 /dev/null}
-@error{} awk: syntax error near line 1
-@error{} awk: bailing out near line 1
-@end group
-@end example
-
-@noindent
-In this case, you should find a version of new @command{awk},
-or just install @command{gawk}!
-
-Throughout this @value{DOCUMENT}, whenever we refer to a language feature
-that should be available in any complete implementation of POSIX @command{awk},
-we simply use the term @command{awk}. When referring to a feature that is
-specific to the GNU implementation, we use the term @command{gawk}.
-
-@node This Manual
-@unnumberedsec Using This Book
-@cindex @command{awk} @subentry terms describing
-
-The term @command{awk} refers to a particular program as well as to the
language you
-use to tell this program what to do. When we need to be careful, we call
-the language ``the @command{awk} language,''
-and the program ``the @command{awk} utility.''
-This @value{DOCUMENT} explains
-both how to write programs in the @command{awk} language and how to
-run the @command{awk} utility.
-The term ``@command{awk} program'' refers to a program written by you in
-the @command{awk} programming language.
-
-@cindex @command{gawk} @subentry @command{awk} and
-@cindex @command{awk} @subentry @command{gawk} and
-@cindex POSIX @command{awk}
-Primarily, this @value{DOCUMENT} explains the features of @command{awk}
-as defined in the POSIX standard. It does so in the context of the
-@command{gawk} implementation. While doing so, it also
-attempts to describe important differences between @command{gawk}
-and other @command{awk}
-@ifclear FOR_PRINT
-implementations.@footnote{All such differences
-appear in the index under the
-entry ``differences in @command{awk} and @command{gawk}.''}
-@end ifclear
-@ifset FOR_PRINT
-implementations.
-@end ifset
-Finally, it notes any @command{gawk} features that are not in
-the POSIX standard for @command{awk}.
-
-@ifnotinfo
-This @value{DOCUMENT} has the difficult task of being both a tutorial and a
reference.
-If you are a novice, feel free to skip over details that seem too complex.
-You should also ignore the many cross-references; they are for the
-expert user and for the Info and
-@uref{https://www.gnu.org/software/gawk/manual/, HTML}
-versions of the @value{DOCUMENT}.
-@end ifnotinfo
-
-There are sidebars
-scattered throughout the @value{DOCUMENT}.
-They add a more complete explanation of points that are relevant, but not
likely
-to be of interest on first reading.
-@ifclear FOR_PRINT
-All appear in the index, under the heading ``sidebar.''
-@end ifclear
-
-Most of the time, the examples use complete @command{awk} programs.
-Some of the more advanced @value{SECTION}s show only the part of the
@command{awk}
-program that illustrates the concept being described.
-
-Although this @value{DOCUMENT} is aimed principally at people who have not been
-exposed
-to @command{awk}, there is a lot of information here that even the
@command{awk}
-expert should find useful. In particular, the description of POSIX
-@command{awk} and the example programs in
-@ref{Library Functions}, and
-@ifnotdocbook
-in
-@end ifnotdocbook
-@ref{Sample Programs},
-should be of interest.
-
-This @value{DOCUMENT} is split into several parts, as follows:
-
-@c FULLXREF ON
-
-@itemize @value{BULLET}
-@item
-Part I describes the @command{awk} language and the @command{gawk} program in
detail.
-It starts with the basics, and continues through all of the features of
@command{awk}.
-It contains the following chapters:
-
-@c nested
-@itemize @value{MINUS}
-@item
-@ref{Getting Started},
-provides the essentials you need to know to begin using @command{awk}.
-
-@item
-@ref{Invoking Gawk},
-describes how to run @command{gawk}, the meaning of its
-command-line options, and how it finds @command{awk}
-program source files.
-
-@item
-@ref{Regexp},
-introduces regular expressions in general, and in particular the flavors
-supported by POSIX @command{awk} and @command{gawk}.
-
-@item
-@ref{Reading Files},
-describes how @command{awk} reads your data.
-It introduces the concepts of records and fields, as well
-as the @code{getline} command.
-I/O redirection is first described here.
-Network I/O is also briefly introduced here.
-
-@item
-@ref{Printing},
-describes how @command{awk} programs can produce output with
-@code{print} and @code{printf}.
-
-@item
-@ref{Expressions},
-describes expressions, which are the basic building blocks
-for getting most things done in a program.
-
-@item
-@ref{Patterns and Actions},
-describes how to write patterns for matching records, actions for
-doing something when a record is matched, and the predefined variables
-@command{awk} and @command{gawk} use.
-
-@item
-@ref{Arrays},
-covers @command{awk}'s one-and-only data structure: the associative array.
-Deleting array elements and whole arrays is described, as well as
-sorting arrays in @command{gawk}. The @value{CHAPTER} also describes how
-@command{gawk} provides arrays of arrays.
-
-@item
-@ref{Functions},
-describes the built-in functions @command{awk} and @command{gawk} provide,
-as well as how to define your own functions. It also discusses how
-@command{gawk} lets you call functions indirectly.
-@end itemize
-
-@item
-Part II shows how to use @command{awk} and @command{gawk} for problem solving.
-There is lots of code here for you to read and learn from.
-This part contains the following chapters:
-
-@c nested
-@itemize @value{MINUS}
-@item
-@ref{Library Functions}, provides a number of functions meant to
-be used from main @command{awk} programs.
-
-@item
-@ref{Sample Programs},
-provides many sample @command{awk} programs.
-@end itemize
-
-Reading these two chapters allows you to see @command{awk}
-solving real problems.
-
-@item
-Part III focuses on features specific to @command{gawk}.
-It contains the following chapters:
-
-@c nested
-@itemize @value{MINUS}
-@item
-@ref{Advanced Features},
-describes a number of advanced features.
-Of particular note
-are the abilities to control the order of array traversal,
-have two-way communications with another process,
-perform TCP/IP networking, and
-profile your @command{awk} programs.
-
-@item
-@ref{Internationalization},
-describes special features for translating program
-messages into different languages at runtime.
-
-@item
-@ref{Debugger}, describes the @command{gawk} debugger.
-
-@item
-@ref{Namespaces}, describes how @command{gawk} allows variables and/or
-functions of the same name to be in different namespaces.
-
-@item
-@ref{Arbitrary Precision Arithmetic},
-describes advanced arithmetic facilities.
-
-@item
-@ref{Dynamic Extensions}, describes how to add new variables and
-functions to @command{gawk} by writing extensions in C or C++.
-@end itemize
-
-@item
-@ifclear FOR_PRINT
-Part IV provides the appendices, the Glossary, and two licenses that cover
-the @command{gawk} source code and this @value{DOCUMENT}, respectively.
-It contains the following appendices:
-@end ifclear
-@ifset FOR_PRINT
-Part IV provides the following appendices,
-including the GNU General Public License:
-@end ifset
-
-@itemize @value{MINUS}
-@item
-@ref{Language History},
-describes how the @command{awk} language has evolved since
-its first release to the present. It also describes how @command{gawk}
-has acquired features over time.
-
-@item
-@ref{Installation},
-describes how to get @command{gawk}, how to compile it
-on POSIX-compatible systems,
-and how to compile and use it on different
-non-POSIX systems. It also describes how to report bugs
-in @command{gawk} and where to get other freely
-available @command{awk} implementations.
-
-@ifset FOR_PRINT
-@item
-@ref{Copying},
-presents the license that covers the @command{gawk} source code.
-@end ifset
-
-@ifclear FOR_PRINT
-@item
-@ref{Notes},
-describes how to disable @command{gawk}'s extensions, as
-well as how to contribute new code to @command{gawk},
-and some possible future directions for @command{gawk} development.
-
-@item
-@ref{Basic Concepts},
-provides some very cursory background material for those who
-are completely unfamiliar with computer programming.
-
-@item
-The @ref{Glossary}, defines most, if not all, of the significant terms used
-throughout the @value{DOCUMENT}. If you find terms that you aren't familiar
with,
-try looking them up here.
-
-@item
-@ref{Copying}, and
-@ref{GNU Free Documentation License},
-present the licenses that cover the @command{gawk} source code
-and this @value{DOCUMENT}, respectively.
-@end ifclear
-@end itemize
-@end itemize
-
-@ifset FOR_PRINT
-The version of this @value{DOCUMENT} distributed with @command{gawk}
-contains additional appendices and other end material.
-To save space, we have omitted them from the
-printed edition. You may find them online, as follows:
-
-@itemize @value{BULLET}
-@item
-@uref{https://www.gnu.org/software/gawk/manual/html_node/Notes.html,
-The appendix on implementation notes}
-describes how to disable @command{gawk}'s extensions, how to contribute
-new code to @command{gawk}, where to find information on some possible
-future directions for @command{gawk} development, and the design decisions
-behind the extension API.
-
-@item
-@uref{https://www.gnu.org/software/gawk/manual/html_node/Basic-Concepts.html,
-The appendix on basic concepts}
-provides some very cursory background material for those who
-are completely unfamiliar with computer programming.
-
-@item
-@uref{https://www.gnu.org/software/gawk/manual/html_node/Glossary.html,
-The Glossary}
-defines most, if not all, of the significant terms used
-throughout the @value{DOCUMENT}. If you find terms that you aren't familiar
with,
-try looking them up here.
-
-@item
-@uref{https://www.gnu.org/software/gawk/manual/html_node/GNU-Free-Documentation-License.html,
-The GNU FDL}
-is the license that covers this @value{DOCUMENT}.
-@end itemize
-
-@c ok not to use CHAPTER / SECTION here
-Some of the chapters have exercise sections; these have also been
-omitted from the print edition but are available online.
-@end ifset
-
-@c FULLXREF OFF
-
-@node Conventions
-@unnumberedsec Typographical Conventions
-
-@cindex Texinfo
-This @value{DOCUMENT} is written in
@uref{https://www.gnu.org/software/texinfo/, Texinfo},
-the GNU documentation formatting language.
-A single Texinfo source file is used to produce both the printed and online
-versions of the documentation.
-@ifnotinfo
-Because of this, the typographical conventions
-are slightly different than in other books you may have read.
-@end ifnotinfo
-@ifinfo
-This @value{SECTION} briefly documents the typographical conventions used in
Texinfo.
-@end ifinfo
-
-Examples you would type at the command line are preceded by the common
-shell primary and secondary prompts, @samp{$} and @samp{>}, respectively.
-Input that you type is shown @kbd{like this}.
-@c 8/2014: @print{} is stripped from the texi to make docbook.
-@ifclear FOR_PRINT
-Output from the command is preceded by the glyph ``@print{}''.
-This typically represents the command's standard output.
-@end ifclear
-@ifset FOR_PRINT
-Output from the command, usually its standard output, appears
-@code{like this}.
-@end ifset
-Error messages and other output on the command's standard error are preceded
-by the glyph ``@error{}''. For example:
-
-@example
-$ @kbd{echo hi on stdout}
-@print{} hi on stdout
-$ @kbd{echo hello on stderr 1>&2}
-@error{} hello on stderr
-@end example
-
-@ifnotinfo
-In the text, almost anything related to programming, such as
-command names,
-variable and function names, and string, numeric and regexp constants
-appear in @code{this font}. Code fragments
-appear in the same font and quoted, @samp{like this}.
-Things that are replaced by the user or programmer
-appear in @var{this font}.
-Options look like this: @option{-f}.
-@value{FFN}s are indicated like this: @file{/path/to/ourfile}.
-@ifclear FOR_PRINT
-Some things are
-emphasized @emph{like this}, and if a point needs to be made
-strongly, it is done @strong{like this}.
-@end ifclear
-The first occurrence of
-a new term is usually its @dfn{definition} and appears in the same
-font as the previous occurrence of ``definition'' in this sentence.
-@end ifnotinfo
-
-Characters that you type at the keyboard look @kbd{like this}. In particular,
-there are special characters called ``control characters.'' These are
-characters that you type by holding down both the @kbd{CONTROL} key and
-another key, at the same time. For example, a @kbd{Ctrl-d} is typed
-by first pressing and holding the @kbd{CONTROL} key, next
-pressing the @kbd{d} key, and finally releasing both keys.
-
-For the sake of brevity, throughout this @value{DOCUMENT}, we refer to
-Brian Kernighan's version of @command{awk} as ``BWK @command{awk}.''
-(@xref{Other Versions} for information on his and other versions.)
-
-@ifset FOR_PRINT
-@quotation NOTE
-Notes of interest look like this.
-@end quotation
-
-@quotation CAUTION
-Cautionary or warning notes look like this.
-@end quotation
-@end ifset
-
-@c fakenode --- for prepinfo
-@unnumberedsubsec Dark Corners
-@cindex Kernighan, Brian @subentry quotes
-@quotation
-@i{Dark corners are basically fractal---no matter how much
-you illuminate, there's always a smaller but darker one.}
-@author Brian Kernighan
-@end quotation
-
-@cindex d.c. @seeentry{dark corner}
-@cindex dark corner
-Until the POSIX standard (and @cite{@value{TITLE}}),
-many features of @command{awk} were either poorly documented or not
-documented at all. Descriptions of such features
-(often called ``dark corners'') are noted in this @value{DOCUMENT} with
-@iftex
-the picture of a flashlight in the margin, as shown here.
-@value{DARKCORNER}
-@end iftex
-@ifnottex
-``(d.c.).''
-@end ifnottex
-@ifclear FOR_PRINT
-They also appear in the index under the heading ``dark corner.''
-@end ifclear
-
-But, as noted by the opening quote, any coverage of dark
-corners is by definition incomplete.
-
-@cindex c.e. @seeentry{common extensions}
-Extensions to the standard @command{awk} language that are supported by
-more than one @command{awk} implementation are marked
-@ifclear FOR_PRINT
-``@value{COMMONEXT},'' and listed in the index under ``common extensions''
-and ``extensions, common.''
-@end ifclear
-@ifset FOR_PRINT
-``@value{COMMONEXT}'' for ``common extension.''
-@end ifset
-
-@node Manual History
-@unnumberedsec The GNU Project and This Book
-
-@cindex FSF (Free Software Foundation)
-@cindex Free Software Foundation (FSF)
-@cindex Stallman, Richard
-The Free Software Foundation (FSF) is a nonprofit organization dedicated
-to the production and distribution of freely distributable software.
-It was founded by Richard M.@: Stallman, the author of the original
-Emacs editor. GNU Emacs is the most widely used version of Emacs today.
-
-@cindex GNU Project
-@cindex GPL (General Public License)
-@cindex GNU General Public License @seeentry{GPL}
-@cindex General Public License @seeentry{GPL}
-@cindex documentation @subentry online
-The GNU@footnote{GNU stands for ``GNU's Not Unix.''}
-Project is an ongoing effort on the part of the Free Software
-Foundation to create a complete, freely distributable, POSIX-compliant
-computing environment.
-The FSF uses the GNU General Public License (GPL) to ensure that
-its software's
-source code is always available to the end user.
-@ifclear FOR_PRINT
-A copy of the GPL is included
-@ifnotinfo
-in this @value{DOCUMENT}
-@end ifnotinfo
-for your reference
-(@pxref{Copying}).
-@end ifclear
-The GPL applies to the C language source code for @command{gawk}.
-To find out more about the FSF and the GNU Project online,
-see @uref{https://www.gnu.org, the GNU Project's home page}.
-This @value{DOCUMENT} may also be read from
-@uref{https://www.gnu.org/software/gawk/manual/, GNU's website}.
-
-@ifclear FOR_PRINT
-A shell, an editor (Emacs), highly portable optimizing C, C++, and
-Objective-C compilers, a symbolic debugger and dozens of large and
-small utilities (such as @command{gawk}), have all been completed and are
-freely available. The GNU operating
-system kernel (the HURD), has been released but remains in an early
-stage of development.
-
-@cindex Linux @seeentry{GNU/Linux}
-@cindex GNU/Linux
-@cindex operating systems @subentry BSD-based
-Until the GNU operating system is more fully developed, you should
-consider using GNU/Linux, a freely distributable, Unix-like operating
-system for Intel,
-Power Architecture,
-Sun SPARC, IBM S/390, and other
-systems.@footnote{The terminology ``GNU/Linux'' is explained
-in the @ref{Glossary}.}
-Many GNU/Linux distributions are
-available for download from the Internet.
-@end ifclear
-
-@ifnotinfo
-The @value{DOCUMENT} you are reading is actually free---at least, the
-information in it is free to anyone. The machine-readable
-source code for the @value{DOCUMENT} comes with @command{gawk}.
-@ifclear FOR_PRINT
-(Take a moment to check the Free Documentation
-License in @ref{GNU Free Documentation License}.)
-@end ifclear
-@end ifnotinfo
-
-@cindex Close, Diane
-The @value{DOCUMENT} itself has gone through multiple previous editions.
-Paul Rubin wrote the very first draft of @cite{The GAWK Manual};
-it was around 40 pages long.
-Diane Close and Richard Stallman improved it, yielding a
-version that was
-around 90 pages and barely described the original, ``old''
-version of @command{awk}.
-
-I started working with that version in the fall of 1988.
-As work on it progressed,
-the FSF published several preliminary versions (numbered 0.@var{x}).
-In 1996, edition 1.0 was released with @command{gawk} 3.0.0.
-The FSF published the first two editions under
-the title @cite{The GNU Awk User's Guide}.
-@ifset FOR_PRINT
-SSC published two editions of the @value{DOCUMENT} under the
-title @cite{Effective awk Programming}, and O'Reilly published
-the third edition in 2001.
-@end ifset
-
-This edition maintains the basic structure of the previous editions.
-For FSF edition 4.0, the content was thoroughly reviewed and updated. All
-references to @command{gawk} versions prior to 4.0 were removed.
-Of significant note for that edition was the addition of @ref{Debugger}.
-
-For FSF edition
-@ifclear FOR_PRINT
-5.0,
-@end ifclear
-@ifset FOR_PRINT
-@value{EDITION}
-(the fourth edition as published by O'Reilly),
-@end ifset
-the content has been reorganized into parts,
-and the major new additions are @ref{Arbitrary Precision Arithmetic},
-and @ref{Dynamic Extensions}.
-
-This @value{DOCUMENT} will undoubtedly continue to evolve. If you
-find an error in the @value{DOCUMENT}, please report it! @xref{Bugs}
-for information on submitting problem reports electronically.
-
-@ifset FOR_PRINT
-@c fakenode --- for prepinfo
-@unnumberedsec How to Stay Current
-
-You may have a newer version of @command{gawk} than the
-one described here. To find out what has changed,
-you should first look at the @file{NEWS} file in the @command{gawk}
-distribution, which provides a high-level summary of the changes in
-each release.
-
-You can then look at the @uref{https://www.gnu.org/software/gawk/manual/,
-online version} of this @value{DOCUMENT} to read about any new features.
-@end ifset
-
-@ifclear FOR_PRINT
-@node How To Contribute
-@unnumberedsec How to Contribute
-
-As the maintainer of GNU @command{awk}, I once thought that I would be
-able to manage a collection of publicly available @command{awk} programs
-and I even solicited contributions. Making things available on the Internet
-helps keep the @command{gawk} distribution down to manageable size.
-
-The initial collection of material, such as it is, is still available
-at @uref{ftp://ftp.freefriends.org/arnold/Awkstuff}.
-
-In the hopes of doing something broader, I acquired the
-@code{awklang.org} domain. Late in 2017, a volunteer took on the task
-of managing it.
-
-If you have written an interesting @command{awk} program that
-you would like to share with the rest of the world, please see
-@uref{http://www.awklang.org} and use the ``Contact'' link.
-
-If you have written a @command{gawk} extension, please see
-@ref{gawkextlib}.
-@end ifclear
-
-@node Acknowledgments
-@unnumberedsec Acknowledgments
-
-The initial draft of @cite{The GAWK Manual} had the following acknowledgments:
-
-@quotation
-Many people need to be thanked for their assistance in producing this
-manual. Jay Fenlason contributed many ideas and sample programs. Richard
-Mlynarik and Robert Chassell gave helpful comments on drafts of this
-manual. The paper @cite{A Supplemental Document for AWK} by John W.@:
-Pierce of the Chemistry Department at UC San Diego, pinpointed several
-issues relevant both to @command{awk} implementation and to this manual, that
-would otherwise have escaped us.
-@end quotation
-
-@cindex Stallman, Richard
-I would like to acknowledge Richard M.@: Stallman, for his vision of a
-better world and for his courage in founding the FSF and starting the
-GNU Project.
-
-@ifclear FOR_PRINT
-Earlier editions of this @value{DOCUMENT} had the following acknowledgements:
-@end ifclear
-@ifset FOR_PRINT
-The previous edition of this @value{DOCUMENT} had
-the following acknowledgements:
-@end ifset
-
-@quotation
-The following people (in alphabetical order)
-provided helpful comments on various
-versions of this book:
-Rick Adams,
-Dr.@: Nelson H.F. Beebe,
-Karl Berry,
-Dr.@: Michael Brennan,
-Rich Burridge,
-Claire Cloutier,
-Diane Close,
-Scott Deifik,
-Christopher (``Topher'') Eliot,
-Jeffrey Friedl,
-Dr.@: Darrel Hankerson,
-Michal Jaegermann,
-Dr.@: Richard J.@: LeBlanc,
-Michael Lijewski,
-Pat Rankin,
-Miriam Robbins,
-Mary Sheehan,
-and
-Chuck Toporek.
-
-@cindex Berry, Karl
-@cindex Chassell, Robert J.@:
-@c @cindex Texinfo
-Robert J.@: Chassell provided much valuable advice on
-the use of Texinfo.
-He also deserves special thanks for
-convincing me @emph{not} to title this @value{DOCUMENT}
-@cite{How to Gawk Politely}.
-Karl Berry helped significantly with the @TeX{} part of Texinfo.
-
-@cindex Hartholz @subentry Marshall
-@cindex Hartholz @subentry Elaine
-@cindex Schreiber @subentry Bert
-@cindex Schreiber @subentry Rita
-I would like to thank Marshall and Elaine Hartholz of Seattle and
-Dr.@: Bert and Rita Schreiber of Detroit for large amounts of quiet vacation
-time in their homes, which allowed me to make significant progress on
-this @value{DOCUMENT} and on @command{gawk} itself.
-
-@cindex Hughes, Phil
-Phil Hughes of SSC
-contributed in a very important way by loaning me his laptop GNU/Linux
-system, not once, but twice, which allowed me to do a lot of work while
-away from home.
-
-@cindex Trueman, David
-David Trueman deserves special credit; he has done a yeoman job
-of evolving @command{gawk} so that it performs well and without bugs.
-Although he is no longer involved with @command{gawk},
-working with him on this project was a significant pleasure.
-
-@cindex Drepper, Ulrich
-@cindex GNITS mailing list
-@cindex mailing list, GNITS
-The intrepid members of the GNITS mailing list, and most notably Ulrich
-Drepper, provided invaluable help and feedback for the design of the
-internationalization features.
-
-Chuck Toporek, Mary Sheehan, and Claire Cloutier of O'Reilly & Associates
contributed
-significant editorial help for this @value{DOCUMENT} for the
-3.1 release of @command{gawk}.
-@end quotation
-
-@cindex Beebe, Nelson H.F.@:
-@cindex Buening, Andreas
-@cindex Collado, Manuel
-@cindex Colombo, Antonio
-@cindex Davies, Stephen
-@cindex Deifik, Scott
-@cindex Demaille, Akim
-@cindex G., Daniel Richard
-@cindex Guerrero, Juan Manuel
-@cindex Hankerson, Darrel
-@cindex Jaegermann, Michal
-@cindex Kahrs, J@"urgen
-@cindex Kasal, Stepan
-@cindex Malmberg, John
-@cindex Ramey, Chet
-@cindex Rankin, Pat
-@cindex Schorr, Andrew
-@cindex Vinschen, Corinna
-@cindex Zaretskii, Eli
-
-Dr.@: Nelson Beebe,
-Andreas Buening,
-Dr.@: Manuel Collado,
-Antonio Colombo,
-Stephen Davies,
-Scott Deifik,
-Akim Demaille,
-Daniel Richard G.,
-Juan Manuel Guerrero,
-Darrel Hankerson,
-Michal Jaegermann,
-J@"urgen Kahrs,
-Stepan Kasal,
-John Malmberg,
-Chet Ramey,
-Pat Rankin,
-Andrew Schorr,
-Corinna Vinschen,
-and Eli Zaretskii
-(in alphabetical order)
-make up the current @command{gawk} ``crack portability team.'' Without
-their hard work and help, @command{gawk} would not be nearly the robust,
-portable program it is today. It has been and continues to be a pleasure
-working with this team of fine people.
-
-Notable code and documentation contributions were made by
-a number of people. @xref{Contributors} for the full list.
-
-@ifset FOR_PRINT
-@cindex Oram, Andy
-Thanks to Andy Oram of O'Reilly Media for initiating
-the fourth edition and for his support during the work.
-Thanks to Jasmine Kwityn for her copyediting work.
-@end ifset
-
-Thanks to Michael Brennan for the Forewords.
-
-@cindex Duman, Patrice
-@cindex Berry, Karl
-@cindex Smith, Gavin
-Thanks to Patrice Dumas for the new @command{makeinfo} program.
-Thanks to Karl Berry for his past work on Texinfo, and
-to Gavin Smith, who continues to work to improve
-the Texinfo markup language.
-
-@cindex Kernighan, Brian
-@cindex Brennan, Michael
-@cindex Day, Robert P.J.@:
-Robert P.J.@: Day, Michael Brennan, and Brian Kernighan kindly acted as
-reviewers for the 2015 edition of this @value{DOCUMENT}. Their feedback
-helped improve the final work.
-
-I would also like to thank Brian Kernighan for his invaluable assistance
during the
-testing and debugging of @command{gawk}, and for his ongoing
-help and advice in clarifying numerous points about the language.
-We could not have done nearly as good a job on either @command{gawk}
-or its documentation without his help.
-
-Brian is in a class by himself as a programmer and technical
-author. I have to thank him (yet again) for his ongoing friendship
-and for being a role model to me for over 30 years!
-Having him as a reviewer is an exciting privilege. It has also
-been extremely humbling@enddots{}
-
-@cindex Robbins @subentry Miriam
-@cindex Robbins @subentry Jean
-@cindex Robbins @subentry Harry
-@cindex G-d
-I must thank my wonderful wife, Miriam, for her patience through
-the many versions of this project, for her proofreading,
-and for sharing me with the computer.
-I would like to thank my parents for their love, and for the grace with
-which they raised and educated me.
-Finally, I also must acknowledge my gratitude to G-d, for the many
opportunities
-He has sent my way, as well as for the gifts He has given me with which to
-take advantage of those opportunities.
-@ifnotdocbook
-@sp 2
-@noindent
-Arnold Robbins @*
-Nof Ayalon @*
-Israel @*
-March, 2020
-@end ifnotdocbook
-
-@ifnotinfo
-@part @value{PART1}The @command{awk} Language
-@end ifnotinfo
-
-@ifdocbook
-
-Part I describes the @command{awk} language and @command{gawk} program
-in detail. It starts with the basics, and continues through all of
-the features of @command{awk}. Included also are many, but not all,
-of the features of @command{gawk}. This part contains the
-following chapters:
-
-@itemize @value{BULLET}
-@item
-@ref{Getting Started}
-
-@item
-@ref{Invoking Gawk}
-
-@item
-@ref{Regexp}
-
-@item
-@ref{Reading Files}
-
-@item
-@ref{Printing}
-
-@item
-@ref{Expressions}
-
-@item
-@ref{Patterns and Actions}
-
-@item
-@ref{Arrays}
-
-@item
-@ref{Functions}
-@end itemize
-@end ifdocbook
-
-@node Getting Started
-@chapter Getting Started with @command{awk}
-@c @cindex script, definition of
-@c @cindex rule, definition of
-@c @cindex program, definition of
-@c @cindex basic function of @command{awk}
-@cindex @command{awk} @subentry function of
-
-The basic function of @command{awk} is to search files for lines (or other
-units of text) that contain certain patterns. When a line matches one
-of the patterns, @command{awk} performs specified actions on that line.
-@command{awk} continues to process input lines in this way until it reaches
-the end of the input files.
-
-@cindex @command{awk} @subentry uses for
-@cindex programming languages @subentry data-driven vs.@: procedural
-@cindex @command{awk} programs
-Programs in @command{awk} are different from programs in most other languages,
-because @command{awk} programs are @dfn{data driven} (i.e., you describe
-the data you want to work with and then what to do when you find it).
-Most other languages are @dfn{procedural}; you have to describe, in great
-detail, every step the program should take. When working with procedural
-languages, it is usually much
-harder to clearly describe the data your program will process.
-For this reason, @command{awk} programs are often refreshingly easy to
-read and write.
-
-@cindex program, definition of
-@cindex rule, definition of
-When you run @command{awk}, you specify an @command{awk} @dfn{program} that
-tells @command{awk} what to do. The program consists of a series of
-@dfn{rules} (it may also contain @dfn{function definitions},
-an advanced feature that we will ignore for now;
-@pxref{User-defined}). Each rule specifies one
-pattern to search for and one action to perform
-upon finding the pattern.
-
-Syntactically, a rule consists of a @dfn{pattern} followed by an
-@dfn{action}. The action is enclosed in braces to separate it from the
-pattern. Newlines usually separate rules. Therefore, an @command{awk}
-program looks like this:
-
-@example
-@var{pattern} @{ @var{action} @}
-@var{pattern} @{ @var{action} @}
-@dots{}
-@end example
-
-@menu
-* Running gawk:: How to run @command{gawk} programs; includes
- command-line syntax.
-* Sample Data Files:: Sample data files for use in the @command{awk}
- programs illustrated in this @value{DOCUMENT}.
-* Very Simple:: A very simple example.
-* Two Rules:: A less simple one-line example using two
- rules.
-* More Complex:: A more complex example.
-* Statements/Lines:: Subdividing or combining statements into
- lines.
-* Other Features:: Other Features of @command{awk}.
-* When:: When to use @command{gawk} and when to use
- other things.
-* Intro Summary:: Summary of the introduction.
-@end menu
-
-@node Running gawk
-@section How to Run @command{awk} Programs
-
-@cindex @command{awk} programs @subentry running
-There are several ways to run an @command{awk} program. If the program is
-short, it is easiest to include it in the command that runs @command{awk},
-like this:
-
-@example
-awk '@var{program}' @var{input-file1} @var{input-file2} @dots{}
-@end example
-
-@cindex command line @subentry formats
-When the program is long, it is usually more convenient to put it in a file
-and run it with a command like this:
-
-@example
-awk -f @var{program-file} @var{input-file1} @var{input-file2} @dots{}
-@end example
-
-This @value{SECTION} discusses both mechanisms, along with several
-variations of each.
-
-@menu
-* One-shot:: Running a short throwaway @command{awk}
- program.
-* Read Terminal:: Using no input files (input from the keyboard
- instead).
-* Long:: Putting permanent @command{awk} programs in
- files.
-* Executable Scripts:: Making self-contained @command{awk} programs.
-* Comments:: Adding documentation to @command{gawk}
- programs.
-* Quoting:: More discussion of shell quoting issues.
-@end menu
-
-@node One-shot
-@subsection One-Shot Throwaway @command{awk} Programs
-
-Once you are familiar with @command{awk}, you will often type in simple
-programs the moment you want to use them. Then you can write the
-program as the first argument of the @command{awk} command, like this:
-
-@example
-awk '@var{program}' @var{input-file1} @var{input-file2} @dots{}
-@end example
-
-@noindent
-where @var{program} consists of a series of patterns and
-actions, as described earlier.
-
-@cindex single quote (@code{'})
-@cindex @code{'} (single quote)
-This command format instructs the @dfn{shell}, or command interpreter,
-to start @command{awk} and use the @var{program} to process records in the
-input file(s). There are single quotes around @var{program} so
-the shell won't interpret any @command{awk} characters as special shell
-characters. The quotes also cause the shell to treat all of @var{program} as
-a single argument for @command{awk}, and allow @var{program} to be more
-than one line long.
-
-@cindex shells @subentry scripts
-@cindex @command{awk} programs @subentry running @subentry from shell scripts
-This format is also useful for running short or medium-sized @command{awk}
-programs from shell scripts, because it avoids the need for a separate
-file for the @command{awk} program. A self-contained shell script is more
-reliable because there are no other files to misplace.
-
-Later in this chapter, in
-@ifdocbook
-the @value{SECTION}
-@end ifdocbook
-@ref{Very Simple},
-we'll see examples of several short,
-self-contained programs.
-
-@node Read Terminal
-@subsection Running @command{awk} Without Input Files
-
-@cindex standard input
-@cindex input @subentry standard
-@cindex input files @subentry running @command{awk} without
-You can also run @command{awk} without any input files. If you type the
-following command line:
-
-@example
-awk '@var{program}'
-@end example
-
-@noindent
-@command{awk} applies the @var{program} to the @dfn{standard input},
-which usually means whatever you type on the keyboard. This continues
-until you indicate end-of-file by typing @kbd{Ctrl-d}.
-(On non-POSIX operating systems, the end-of-file character may be different.)
-
-@cindex files @subentry input @seeentry{input files}
-@cindex input files @subentry running @command{awk} without
-@cindex @command{awk} programs @subentry running @subentry without input files
-As an example, the following program prints a friendly piece of advice
-(from Douglas Adams's @cite{The Hitchhiker's Guide to the Galaxy}),
-to keep you from worrying about the complexities of computer
-programming:
-
-@example
-$ @kbd{awk 'BEGIN @{ print "Don\47t Panic!" @}'}
-@print{} Don't Panic!
-@end example
-
-@command{awk} executes statements associated with @code{BEGIN} before
-reading any input. If there are no other statements in your program,
-as is the case here, @command{awk} just stops, instead of trying to read
-input it doesn't know how to process.
-The @samp{\47} is a magic way (explained later) of getting a single quote into
-the program, without having to engage in ugly shell quoting tricks.
-
-@quotation NOTE
-If you use Bash as your shell, you should execute the
-command @samp{set +H} before running this program interactively, to
-disable the C shell-style command history, which treats @samp{!} as a
-special character. We recommend putting this command into your personal
-startup file.
-@end quotation
-
-This next simple @command{awk} program
-emulates the @command{cat} utility; it copies whatever you type on the
-keyboard to its standard output (why this works is explained shortly):
-
-@example
-$ @kbd{awk '@{ print @}'}
-@kbd{Now is the time for all good men}
-@print{} Now is the time for all good men
-@kbd{to come to the aid of their country.}
-@print{} to come to the aid of their country.
-@kbd{Four score and seven years ago, ...}
-@print{} Four score and seven years ago, ...
-@kbd{What, me worry?}
-@print{} What, me worry?
-@kbd{Ctrl-d}
-@end example
-
-@node Long
-@subsection Running Long Programs
-
-@cindex @command{awk} programs @subentry running
-@cindex @command{awk} programs @subentry lengthy
-@cindex files @subentry @command{awk} programs in
-Sometimes @command{awk} programs are very long. In these cases, it is
-more convenient to put the program into a separate file. In order to tell
-@command{awk} to use that file for its program, you type:
-
-@example
-awk -f @var{source-file} @var{input-file1} @var{input-file2} @dots{}
-@end example
-
-@cindex @option{-f} option
-@cindex command line @subentry option @option{-f}
-The @option{-f} instructs the @command{awk} utility to get the
-@command{awk} program from the file @var{source-file} (@pxref{Options}).
-Any @value{FN} can be used for @var{source-file}. For example, you
-could put the program:
-
-@example
-BEGIN @{ print "Don't Panic!" @}
-@end example
-
-@noindent
-into the file @file{advice}. Then this command:
-
-@example
-awk -f advice
-@end example
-
-@noindent
-does the same thing as this one:
-
-@example
-awk 'BEGIN @{ print "Don\47t Panic!" @}'
-@end example
-
-@cindex quoting @subentry in @command{gawk} command lines
-@noindent
-This was explained earlier
-(@pxref{Read Terminal}).
-Note that you don't usually need single quotes around the @value{FN} that you
-specify with @option{-f}, because most @value{FN}s don't contain any of the
shell's
-special characters. Notice that in @file{advice}, the @command{awk}
-program did not have single quotes around it. The quotes are only needed
-for programs that are provided on the @command{awk} command line.
-(Also, placing the program in a file allows us to use a literal single quote
in the program
-text, instead of the magic @samp{\47}.)
-
-@cindex single quote (@code{'}) @subentry in @command{gawk} command lines
-@cindex @code{'} (single quote) @subentry in @command{gawk} command lines
-If you want to clearly identify an @command{awk} program file as such,
-you can add the extension @file{.awk} to the @value{FN}. This doesn't
-affect the execution of the @command{awk} program but it does make
-``housekeeping'' easier.
-
-@node Executable Scripts
-@subsection Executable @command{awk} Programs
-@cindex @command{awk} programs
-@cindex @code{#} (number sign) @subentry @code{#!} (executable scripts)
-@cindex Unix @subentry @command{awk} scripts and
-@cindex number sign (@code{#}) @subentry @code{#!} (executable scripts)
-
-Once you have learned @command{awk}, you may want to write self-contained
-@command{awk} scripts, using the @samp{#!} script mechanism. You can do
-this on many systems.@footnote{The @samp{#!} mechanism works on
-GNU/Linux systems, BSD-based systems, and commercial Unix systems.}
-For example, you could update the file @file{advice} to look like this:
-
-@example
-#! /bin/awk -f
-
-BEGIN @{ print "Don't Panic!" @}
-@end example
-
-@noindent
-After making this file executable (with the @command{chmod} utility),
-simply type @samp{advice}
-at the shell and the system arranges to run @command{awk} as if you had
-typed @samp{awk -f advice}:
-
-@example
-$ @kbd{chmod +x advice}
-$ @kbd{./advice}
-@print{} Don't Panic!
-@end example
-
-@noindent
-Self-contained @command{awk} scripts are useful when you want to write a
-program that users can invoke without their having to know that the program is
-written in @command{awk}.
-
-@sidebar Understanding @samp{#!}
-@cindex portability @subentry @code{#!} (executable scripts)
-
-@command{awk} is an @dfn{interpreted} language. This means that the
-@command{awk} utility reads your program and then processes your data
-according to the instructions in your program. (This is different
-from a @dfn{compiled} language such as C, where your program is first
-compiled into machine code that is executed directly by your system's
-processor.) The @command{awk} utility is thus termed an @dfn{interpreter}.
-Many modern languages are interpreted.
-
-The line beginning with @samp{#!} lists the full @value{FN} of an
-interpreter to run and a single optional initial command-line argument
-to pass to that interpreter. The operating system then runs the
-interpreter with the given argument and the full argument list of the
-executed program. The first argument in the list is the full @value{FN}
-of the @command{awk} program. The rest of the argument list contains
-either options to @command{awk}, or @value{DF}s, or both. (Note that on
-many systems @command{awk} is found in @file{/usr/bin} instead of
-in @file{/bin}.)
-
-Some systems limit the length of the interpreter name to 32 characters.
-Often, this can be dealt with by using a symbolic link.
-
-You should not put more than one argument on the @samp{#!}
-line after the path to @command{awk}. It does not work. The operating system
-treats the rest of the line as a single argument and passes it to
@command{awk}.
-Doing this leads to confusing behavior---most likely a usage diagnostic
-of some sort from @command{awk}.
-
-@cindex @code{ARGC}/@code{ARGV} variables @subentry portability and
-@cindex portability @subentry @code{ARGV} variable
-@cindex dark corner @subentry @code{ARGV} variable, value of
-Finally, the value of @code{ARGV[0]}
-(@pxref{Built-in Variables})
-varies depending upon your operating system.
-Some systems put @samp{awk} there, some put the full pathname
-of @command{awk} (such as @file{/bin/awk}), and some put the name
-of your script (@samp{advice}). @value{DARKCORNER}
-Don't rely on the value of @code{ARGV[0]}
-to provide your script name.
-@end sidebar
-
-@node Comments
-@subsection Comments in @command{awk} Programs
-@cindex @code{#} (number sign) @subentry commenting
-@cindex number sign (@code{#}) @subentry commenting
-@cindex commenting
-@cindex @command{awk} programs @subentry documenting
-
-A @dfn{comment} is some text that is included in a program for the sake
-of human readers; it is not really an executable part of the program. Comments
-can explain what the program does and how it works. Nearly all
-programming languages have provisions for comments, as programs are
-typically hard to understand without them.
-
-In the @command{awk} language, a comment starts with the number sign
-character (@samp{#}) and continues to the end of the line.
-The @samp{#} does not have to be the first character on the line. The
-@command{awk} language ignores the rest of a line following a number sign.
-For example, we could have put the following into @file{advice}:
-
-@example
-# This program prints a nice, friendly message. It helps
-# keep novice users from being afraid of the computer.
-BEGIN @{ print "Don't Panic!" @}
-@end example
-
-You can put comment lines into keyboard-composed throwaway @command{awk}
-programs, but this usually isn't very useful; the purpose of a
-comment is to help you or another person understand the program
-when reading it at a later time.
-
-@cindex quoting @subentry for small awk programs
-@cindex single quote (@code{'}) @subentry vs.@: apostrophe
-@cindex @code{'} (single quote) @subentry vs.@: apostrophe
-@quotation CAUTION
-As mentioned in
-@ref{One-shot},
-you can enclose short to medium-sized programs in single quotes,
-in order to keep
-your shell scripts self-contained. When doing so, @emph{don't} put
-an apostrophe (i.e., a single quote) into a comment (or anywhere else
-in your program). The shell interprets the quote as the closing
-quote for the entire program. As a result, usually the shell
-prints a message about mismatched quotes, and if @command{awk} actually
-runs, it will probably print strange messages about syntax errors.
-For example, look at the following:
-
-@example
-$ @kbd{awk 'BEGIN @{ print "hello" @} # let's be cute'}
->
-@end example
-
-The shell sees that the first two quotes match, and that
-a new quoted object begins at the end of the command line.
-It therefore prompts with the secondary prompt, waiting for more input.
-With Unix @command{awk}, closing the quoted string produces this result:
-
-@example
-$ @kbd{awk '@{ print "hello" @} # let's be cute'}
-> @kbd{'}
-@error{} awk: can't open file be
-@error{} source line number 1
-@end example
-
-@cindex @code{\} (backslash)
-@cindex backslash (@code{\})
-Putting a backslash before the single quote in @samp{let's} wouldn't help,
-because backslashes are not special inside single quotes.
-The next @value{SUBSECTION} describes the shell's quoting rules.
-@end quotation
-
-@node Quoting
-@subsection Shell Quoting Issues
-@cindex shell quoting, rules for
-
-@menu
-* DOS Quoting:: Quoting in Windows Batch Files.
-@end menu
-
-For short to medium-length @command{awk} programs, it is most convenient
-to enter the program on the @command{awk} command line.
-This is best done by enclosing the entire program in single quotes.
-This is true whether you are entering the program interactively at
-the shell prompt, or writing it as part of a larger shell script:
-
-@example
-awk '@var{program text}' @var{input-file1} @var{input-file2} @dots{}
-@end example
-
-@cindex shells @subentry quoting @subentry rules for
-@cindex Bourne shell, quoting rules for
-Once you are working with the shell, it is helpful to have a basic
-knowledge of shell quoting rules. The following rules apply only to
-POSIX-compliant, Bourne-style shells (such as Bash, the GNU Bourne-Again
-Shell). If you use the C shell, you're on your own.
-
-Before diving into the rules, we introduce a concept that appears
-throughout this @value{DOCUMENT}, which is that of the @dfn{null},
-or empty, string.
-
-The null string is character data that has no value.
-In other words, it is empty. It is written in @command{awk} programs
-like this: @code{""}. In the shell, it can be written using single
-or double quotes: @code{""} or @code{''}. Although the null string has
-no characters in it, it does exist. For example, consider this command:
-
-@example
-$ @kbd{echo ""}
-@end example
-
-@noindent
-Here, the @command{echo} utility receives a single argument, even
-though that argument has no characters in it. In the rest of this
-@value{DOCUMENT}, we use the terms @dfn{null string} and @dfn{empty string}
-interchangeably. Now, on to the quoting rules:
-
-@itemize @value{BULLET}
-@item
-Quoted items can be concatenated with nonquoted items as well as with other
-quoted items. The shell turns everything into one argument for
-the command.
-
-@item
-Preceding any single character with a backslash (@samp{\}) quotes
-that character. The shell removes the backslash and passes the quoted
-character on to the command.
-
-@item
-@cindex @code{\} (backslash) @subentry in shell commands
-@cindex backslash (@code{\}) @subentry in shell commands
-@cindex single quote (@code{'}) @subentry in shell commands
-@cindex @code{'} (single quote) @subentry in shell commands
-Single quotes protect everything between the opening and closing quotes.
-The shell does no interpretation of the quoted text, passing it on verbatim
-to the command.
-It is @emph{impossible} to embed a single quote inside single-quoted text.
-Refer back to
-@ref{Comments}
-for an example of what happens if you try.
-
-@item
-@cindex double quote (@code{"}) @subentry in shell commands
-@cindex @code{"} (double quote) @subentry in shell commands
-Double quotes protect most things between the opening and closing quotes.
-The shell does at least variable and command substitution on the quoted text.
-Different shells may do additional kinds of processing on double-quoted text.
-
-Because certain characters within double-quoted text are processed by the
shell,
-they must be @dfn{escaped} within the text. Of note are the characters
-@samp{$}, @samp{`}, @samp{\}, and @samp{"}, all of which must be preceded by
-a backslash within double-quoted text if they are to be passed on literally
-to the program. (The leading backslash is stripped first.)
-Thus, the example seen
-@ifnotinfo
-previously
-@end ifnotinfo
-in @ref{Read Terminal}:
-
-@example
-awk 'BEGIN @{ print "Don\47t Panic!" @}'
-@end example
-
-@noindent
-could instead be written this way:
-
-@example
-$ @kbd{awk "BEGIN @{ print \"Don't Panic!\" @}"}
-@print{} Don't Panic!
-@end example
-
-@cindex single quote (@code{'}) @subentry with double quotes
-@cindex @code{'} (single quote) @subentry with double quotes
-Note that the single quote is not special within double quotes.
-
-@item
-Null strings are removed when they occur as part of a non-null
-command-line argument, while explicit null objects are kept.
-For example, to specify that the field separator @code{FS} should
-be set to the null string, use:
-
-@example
-awk -F "" '@var{program}' @var{files} # correct
-@end example
-
-@noindent
-@cindex null strings @subentry in @command{gawk} arguments, quoting and
-Don't use this:
-
-@example
-awk -F"" '@var{program}' @var{files} # wrong!
-@end example
-
-@noindent
-In the second case, @command{awk} attempts to use the text of the program
-as the value of @code{FS}, and the first @value{FN} as the text of the program!
-This results in syntax errors at best, and confusing behavior at worst.
-@end itemize
-
-@cindex quoting @subentry in @command{gawk} command lines @subentry tricks for
-Mixing single and double quotes is difficult. You have to resort
-to shell quoting tricks, like this:
-
-@example
-$ @kbd{awk 'BEGIN @{ print "Here is a single quote <'"'"'>" @}'}
-@print{} Here is a single quote <'>
-@end example
-
-@noindent
-This program consists of three concatenated quoted strings. The first and the
-third are single-quoted, and the second is double-quoted.
-
-This can be ``simplified'' to:
-
-@example
-$ @kbd{awk 'BEGIN @{ print "Here is a single quote <'\''>" @}'}
-@print{} Here is a single quote <'>
-@end example
-
-@noindent
-Judge for yourself which of these two is the more readable.
-
-Another option is to use double quotes, escaping the embedded,
@command{awk}-level
-double quotes:
-
-@example
-$ @kbd{awk "BEGIN @{ print \"Here is a single quote <'>\" @}"}
-@print{} Here is a single quote <'>
-@end example
-
-@noindent
-This option is also painful, because double quotes, backslashes, and dollar
signs
-are very common in more advanced @command{awk} programs.
-
-A third option is to use the octal escape sequence equivalents
-(@pxref{Escape Sequences})
-for the
-single- and double-quote characters, like so:
-
-@example
-@group
-$ @kbd{awk 'BEGIN @{ print "Here is a single quote <\47>" @}'}
-@print{} Here is a single quote <'>
-$ @kbd{awk 'BEGIN @{ print "Here is a double quote <\42>" @}'}
-@print{} Here is a double quote <">
-@end group
-@end example
-
-@noindent
-This works nicely, but you should comment clearly what the
-escape sequences mean.
-
-A fourth option is to use command-line variable assignment, like this:
-
-@example
-$ @kbd{awk -v sq="'" 'BEGIN @{ print "Here is a single quote <" sq ">" @}'}
-@print{} Here is a single quote <'>
-@end example
-
-(Here, the two string constants and the value of @code{sq} are concatenated
-into a single string that is printed by @code{print}.)
-
-If you really need both single and double quotes in your @command{awk}
-program, it is probably best to move it into a separate file, where
-the shell won't be part of the picture and you can say what you mean.
-
-@node DOS Quoting
-@subsubsection Quoting in MS-Windows Batch Files
-
-@ignore
-Date: Wed, 21 May 2008 09:58:43 +0200 (CEST)
-From: jeroen.brink@inter.NL.net
-Subject: (g)awk "contribution"
-To: arnold@skeeve.com
-Message-id: <42220.193.172.132.34.1211356723.squirrel@webmail.internl.net>
-
-Hello Arnold,
-
-maybe you can help me out. Found your email on the GNU/awk online manual
-pages.
-
-I've searched hard to figure out how, on Windows, to print double quotes.
-Couldn't find it in the Quotes area, nor on google or elsewhere. Finally i
-figured out how to do this myself.
-
-How to print all lines in a file surrounded by double quotes (on Windows):
-
-gawk "{ print \"\042\" $0 \"\042\" }" <file>
-
-Maybe this is a helpfull tip for other (Windows) gawk users. However, i
-don't have a clue as to where to "publish" this tip! Do you?
-
-Kind regards,
-
-Jeroen Brink
-@end ignore
-
-Although this @value{DOCUMENT} generally only worries about POSIX systems and
the
-POSIX shell, the following issue arises often enough for many users that
-it is worth addressing.
-
-@cindex Brink, Jeroen
-The ``shells'' on Microsoft Windows systems use the double-quote
-character for quoting, and make it difficult or impossible to include an
-escaped double-quote character in a command-line script. The following
-example, courtesy of Jeroen Brink, shows how to escape the double quotes
-from this one liner script that prints all lines in a file surrounded by
-double quotes:
-
-@example
-@{ print "\"" $0 "\"" @}
-@end example
-
-@noindent
-In an MS-Windows command-line the one-liner script above may be passed as
-follows:
-
-@example
-gawk "@{ print \"\042\" $0 \"\042\" @}" @var{file}
-@end example
-
-In this example the @samp{\042} is the octal code for a double-quote;
-@command{gawk} converts it into a real double-quote for output by
-the @code{print} statement.
-
-In MS-Windows escaping double-quotes is a little tricky because you use
-backslashes to escape double-quotes, but backslashes themselves are not
-escaped in the usual way; indeed they are either duplicated or not,
-depending upon whether there is a subsequent double-quote. The MS-Windows
-rule for double-quoting a string is the following:
-
-@enumerate
-@item
-For each double quote in the original string, let @var{N} be the number
-of backslash(es) before it, @var{N} might be zero. Replace these @var{N}
-backslash(es) by @math{2@value{TIMES}@var{N}+1} backslash(es)
-
-@item
-Let @var{N} be the number of backslash(es) tailing the original string,
-@var{N} might be zero. Replace these @var{N} backslash(es) by
-@math{2@value{TIMES}@var{N}} backslash(es)
-
-@item
-Surround the resulting string by double-quotes.
-@end enumerate
-
-So to double-quote the one-liner script @samp{@{ print "\"" $0 "\"" @}}
-from the previous example you would do it this way:
-
-@example
-gawk "@{ print \"\\\"\" $0 \"\\\"\" @}" @var{file}
-@end example
-
-@noindent
-However, the use of @samp{\042} instead of @samp{\\\"} is also possible
-and easier to read, because backslashes that are not followed by a
-double-quote don't need duplication.
-
-@node Sample Data Files
-@section @value{DDF}s for the Examples
-
-@cindex input files @subentry examples
-@cindex @code{mail-list} file
-Many of the examples in this @value{DOCUMENT} take their input from two sample
-@value{DF}s. The first, @file{mail-list}, represents a list of peoples' names
-together with their email addresses and information about those people.
-The second @value{DF}, called @file{inventory-shipped}, contains
-information about monthly shipments. In both files,
-each line is considered to be one @dfn{record}.
-
-In @file{mail-list}, each record contains the name of a person,
-his/her phone number, his/her email address, and a code for his/her
relationship
-with the author of the list.
-The columns are aligned using spaces.
-An @samp{A} in the last column
-means that the person is an acquaintance. An @samp{F} in the last
-column means that the person is a friend.
-An @samp{R} means that the person is a relative:
-
-@example
-@c system if test ! -d eg ; then mkdir eg ; fi
-@c system if test ! -d eg/lib ; then mkdir eg/lib ; fi
-@c system if test ! -d eg/data ; then mkdir eg/data ; fi
-@c system if test ! -d eg/prog ; then mkdir eg/prog ; fi
-@c system if test ! -d eg/misc ; then mkdir eg/misc ; fi
-@c system if test ! -d eg/test-programs ; then mkdir eg/test-programs ; fi
-@c file eg/data/mail-list
-Amelia 555-5553 amelia.zodiacusque@@gmail.com F
-Anthony 555-3412 anthony.asserturo@@hotmail.com A
-Becky 555-7685 becky.algebrarum@@gmail.com A
-Bill 555-1675 bill.drowning@@hotmail.com A
-Broderick 555-0542 broderick.aliquotiens@@yahoo.com R
-Camilla 555-2912 camilla.infusarum@@skynet.be R
-Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
-Julie 555-6699 julie.perscrutabor@@skeeve.com F
-Martin 555-6480 martin.codicibus@@hotmail.com A
-Samuel 555-3430 samuel.lanceolis@@shu.edu A
-Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
-@c endfile
-@end example
-
-@cindex @code{inventory-shipped} file
-The @value{DF} @file{inventory-shipped} represents
-information about shipments during the year.
-Each record contains the month, the number
-of green crates shipped, the number of red boxes shipped, the number of
-orange bags shipped, and the number of blue packages shipped,
-respectively. There are 16 entries, covering the 12 months of last year
-and the first four months of the current year.
-An empty line separates the data for the two years:
-
-@example
-@c file eg/data/inventory-shipped
-Jan 13 25 15 115
-Feb 15 32 24 226
-Mar 15 24 34 228
-Apr 31 52 63 420
-May 16 34 29 208
-Jun 31 42 75 492
-Jul 24 34 67 436
-Aug 15 34 47 316
-Sep 13 55 37 277
-Oct 29 54 68 525
-Nov 20 87 82 577
-Dec 17 35 61 401
-
-Jan 21 36 64 620
-Feb 26 58 80 652
-Mar 24 75 70 495
-Apr 21 70 74 514
-@c endfile
-@end example
-
-The sample files are included in the @command{gawk} distribution,
-in the directory @file{awklib/eg/data}.
-
-@node Very Simple
-@section Some Simple Examples
-
-The following command runs a simple @command{awk} program that searches the
-input file @file{mail-list} for the character string @samp{li} (a
-grouping of characters is usually called a @dfn{string};
-the term @dfn{string} is based on similar usage in English, such
-as ``a string of pearls'' or ``a string of cars in a train''):
-
-@example
-awk '/li/ @{ print $0 @}' mail-list
-@end example
-
-@noindent
-When lines containing @samp{li} are found, they are printed because
-@w{@samp{print $0}} means print the current line. (Just @samp{print} by
-itself means the same thing, so we could have written that
-instead.)
-
-You will notice that slashes (@samp{/}) surround the string @samp{li}
-in the @command{awk} program. The slashes indicate that @samp{li}
-is the pattern to search for. This type of pattern is called a
-@dfn{regular expression}, which is covered in more detail later
-(@pxref{Regexp}).
-The pattern is allowed to match parts of words.
-There are
-single quotes around the @command{awk} program so that the shell won't
-interpret any of it as special shell characters.
-
-Here is what this program prints:
-
-@example
-$ @kbd{awk '/li/ @{ print $0 @}' mail-list}
-@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F
-@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R
-@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F
-@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A
-@end example
-
-@cindex actions @subentry default
-@cindex patterns @subentry default
-In an @command{awk} rule, either the pattern or the action can be omitted,
-but not both. If the pattern is omitted, then the action is performed
-for @emph{every} input line. If the action is omitted, the default
-action is to print all lines that match the pattern.
-
-@cindex actions @subentry empty
-Thus, we could leave out the action (the @code{print} statement and the
-braces) in the previous example and the result would be the same:
-@command{awk} prints all lines matching the pattern @samp{li}. By comparison,
-omitting the @code{print} statement but retaining the braces makes an
-empty action that does nothing (i.e., no lines are printed).
-
-@cindex @command{awk} programs @subentry one-line examples
-Many practical @command{awk} programs are just a line or two long. Following
is a
-collection of useful, short programs to get you started. Some of these
-programs contain constructs that haven't been covered yet. (The description
-of the program will give you a good idea of what is going on, but you'll
-need to read the rest of the @value{DOCUMENT} to become an @command{awk}
expert!)
-Most of the examples use a @value{DF} named @file{data}. This is just a
-placeholder; if you use these programs yourself, substitute
-your own @value{FN}s for @file{data}.
-
-@cindex @command{ls} utility
-Some of the following examples use the output of @w{@samp{ls -l}} as input.
-@command{ls} is a system command that gives you a listing of the files in a
-directory. With the @option{-l} option, this listing includes each file's
-size and the date the file was last modified. Its output looks like this:
-
-@example
--rw-r--r-- 1 arnold user 1933 Nov 7 13:05 Makefile
--rw-r--r-- 1 arnold user 10809 Nov 7 13:03 awk.h
--rw-r--r-- 1 arnold user 983 Apr 13 12:14 awk.tab.h
--rw-r--r-- 1 arnold user 31869 Jun 15 12:20 awkgram.y
--rw-r--r-- 1 arnold user 22414 Nov 7 13:03 awk1.c
--rw-r--r-- 1 arnold user 37455 Nov 7 13:03 awk2.c
--rw-r--r-- 1 arnold user 27511 Dec 9 13:07 awk3.c
--rw-r--r-- 1 arnold user 7989 Nov 7 13:03 awk4.c
-@end example
-
-@noindent
-The first field contains read-write permissions, the second field contains
-the number of links to the file, and the third field identifies the
-file's owner. The fourth field identifies the file's group. The fifth
-field contains the file's size in bytes. The sixth, seventh, and eighth
-fields contain the month, day, and time, respectively, that the file
-was last modified. Finally, the ninth field contains the @value{FN}.
-
-For future reference, note that there is often more than
-one way to do things in @command{awk}. At some point, you may want
-to look back at these examples and see if
-you can come up with different ways to do the same things shown here:
-
-@itemize @value{BULLET}
-@item
-Print every line that is longer than 80 characters:
-
-@example
-awk 'length($0) > 80' data
-@end example
-
-The sole rule has a relational expression as its pattern and has no
-action---so it uses the default action, printing the record.
-
-@item
-Print the length of the longest input line:
-
-@example
-@group
-awk '@{ if (length($0) > max) max = length($0) @}
- END @{ print max @}' data
-@end group
-@end example
-
-The code associated with @code{END} executes after all
-input has been read; it's the other side of the coin to @code{BEGIN}.
-
-@cindex @command{expand} utility
-@item
-Print the length of the longest line in @file{data}:
-
-@example
-expand data | awk '@{ if (x < length($0)) x = length($0) @}
- END @{ print "maximum line length is " x @}'
-@end example
-
-This example differs slightly from the previous one:
-the input is processed by the @command{expand} utility to change TABs
-into spaces, so the widths compared are actually the right-margin columns,
-as opposed to the number of input characters on each line.
-
-@item
-Print every line that has at least one field:
-
-@example
-awk 'NF > 0' data
-@end example
-
-This is an easy way to delete blank lines from a file (or rather, to
-create a new file similar to the old file but from which the blank lines
-have been removed).
-
-@item
-Print seven random numbers from 0 to 100, inclusive:
-
-@example
-awk 'BEGIN @{ for (i = 1; i <= 7; i++)
- print int(101 * rand()) @}'
-@end example
-
-@item
-Print the total number of bytes used by @var{files}:
-
-@example
-ls -l @var{files} | awk '@{ x += $5 @}
- END @{ print "total bytes: " x @}'
-@end example
-
-@item
-Print the total number of kilobytes used by @var{files}:
-
-@c Don't use \ continuation, not discussed yet
-@c Remember that awk does floating point division,
-@c no need for (x+1023) / 1024
-@example
-ls -l @var{files} | awk '@{ x += $5 @}
- END @{ print "total K-bytes:", x / 1024 @}'
-@end example
-
-@item
-Print a sorted list of the login names of all users:
-
-@example
-awk -F: '@{ print $1 @}' /etc/passwd | sort
-@end example
-
-@item
-Count the lines in a file:
-
-@example
-awk 'END @{ print NR @}' data
-@end example
-
-@item
-Print the even-numbered lines in the @value{DF}:
-
-@example
-awk 'NR % 2 == 0' data
-@end example
-
-If you used the expression @samp{NR % 2 == 1} instead,
-the program would print the odd-numbered lines.
-@end itemize
-
-@node Two Rules
-@section An Example with Two Rules
-@cindex @command{awk} programs
-
-The @command{awk} utility reads the input files one line at a
-time. For each line, @command{awk} tries the patterns of each rule.
-If several patterns match, then several actions execute in the order in
-which they appear in the @command{awk} program. If no patterns match, then
-no actions run.
-
-After processing all the rules that match the line (and perhaps there are
none),
-@command{awk} reads the next line. (However,
-@pxref{Next Statement}
-@ifdocbook
-and @ref{Nextfile Statement}.)
-@end ifdocbook
-@ifnotdocbook
-and also @pxref{Nextfile Statement}.)
-@end ifnotdocbook
-This continues until the program reaches the end of the file.
-For example, the following @command{awk} program contains two rules:
-
-@example
-/12/ @{ print $0 @}
-/21/ @{ print $0 @}
-@end example
-
-@noindent
-The first rule has the string @samp{12} as the
-pattern and @samp{print $0} as the action. The second rule has the
-string @samp{21} as the pattern and also has @samp{print $0} as the
-action. Each rule's action is enclosed in its own pair of braces.
-
-This program prints every line that contains the string
-@samp{12} @emph{or} the string @samp{21}. If a line contains both
-strings, it is printed twice, once by each rule.
-
-This is what happens if we run this program on our two sample @value{DF}s,
-@file{mail-list} and @file{inventory-shipped}:
-
-@example
-$ @kbd{awk '/12/ @{ print $0 @}}
-> @kbd{/21/ @{ print $0 @}' mail-list inventory-shipped}
-@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A
-@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R
-@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
-@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
-@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
-@print{} Jan 21 36 64 620
-@print{} Apr 21 70 74 514
-@end example
-
-@noindent
-Note how the line beginning with @samp{Jean-Paul}
-in @file{mail-list} was printed twice, once for each rule.
-
-@node More Complex
-@section A More Complex Example
-
-Now that we've mastered some simple tasks, let's look at
-what typical @command{awk}
-programs do. This example shows how @command{awk} can be used to
-summarize, select, and rearrange the output of another utility. It uses
-features that haven't been covered yet, so don't worry if you don't
-understand all the details:
-
-@example
-ls -l | awk '$6 == "Nov" @{ sum += $5 @}
- END @{ print sum @}'
-@end example
-
-@cindex @command{ls} utility
-This command prints the total number of bytes in all the files in the
-current directory that were last modified in November (of any year).
-
-As a reminder, the output of @w{@samp{ls -l}} gives you a listing of the
-files in a directory, including each file's size and the date the file
-was last modified. The first field contains read-write permissions,
-the second field contains the number of links to the file, and the
-third field identifies the file's owner. The fourth field identifies
-the file's group. The fifth field contains the file's size in bytes.
-The sixth, seventh, and eighth fields contain the month, day, and time,
-respectively, that the file was last modified. Finally, the ninth field
-contains the @value{FN}.
-
-@c @cindex automatic initialization
-@cindex initialization, automatic
-The @samp{$6 == "Nov"} in our @command{awk} program is an expression that
-tests whether the sixth field of the output from @w{@samp{ls -l}}
-matches the string @samp{Nov}. Each time a line has the string
-@samp{Nov} for its sixth field, @command{awk} performs the action
-@samp{sum += $5}. This adds the fifth field (the file's size) to the variable
-@code{sum}. As a result, when @command{awk} has finished reading all the
-input lines, @code{sum} is the total of the sizes of the files whose
-lines matched the pattern. (This works because @command{awk} variables
-are automatically initialized to zero.)
-
-After the last line of output from @command{ls} has been processed, the
-@code{END} rule executes and prints the value of @code{sum}.
-In this example, the value of @code{sum} is 80600.
-
-These more advanced @command{awk} techniques are covered in later
-@value{SECTION}s
-(@pxref{Action Overview}). Before you can move on to more
-advanced @command{awk} programming, you have to know how @command{awk}
interprets
-your input and displays your output. By manipulating fields and using
-@code{print} statements, you can produce some very useful and
-impressive-looking reports.
-
-@node Statements/Lines
-@section @command{awk} Statements Versus Lines
-@cindex line breaks
-@cindex newlines
-
-Most often, each line in an @command{awk} program is a separate statement or
-separate rule, like this:
-
-@example
-awk '/12/ @{ print $0 @}
- /21/ @{ print $0 @}' mail-list inventory-shipped
-@end example
-
-@cindex @command{gawk} @subentry newlines in
-However, @command{gawk} ignores newlines after any of the following
-symbols and keywords:
-
-@example
-, @{ ? : || && do else
-@end example
-
-@noindent
-A newline at any other point is considered the end of the
-statement.@footnote{The @samp{?} and @samp{:} referred to here is the
-three-operand conditional expression described in
-@ref{Conditional Exp}.
-Splitting lines after @samp{?} and @samp{:} is a minor @command{gawk}
-extension; if @option{--posix} is specified
-(@pxref{Options}), then this extension is disabled.}
-
-@cindex @code{\} (backslash) @subentry continuing lines and
-@cindex backslash (@code{\}) @subentry continuing lines and
-If you would like to split a single statement into two lines at a point
-where a newline would terminate it, you can @dfn{continue} it by ending the
-first line with a backslash character (@samp{\}). The backslash must be
-the final character on the line in order to be recognized as a continuation
-character. A backslash followed by a newline is allowed anywhere in the
statement, even
-in the middle of a string or regular expression. For example:
-
-@example
-awk '/This regular expression is too long, so continue it\
- on the next line/ @{ print $1 @}'
-@end example
-
-@noindent
-@cindex portability @subentry backslash continuation and
-We have generally not used backslash continuation in our sample programs.
-@command{gawk} places no limit on the
-length of a line, so backslash continuation is never strictly necessary;
-it just makes programs more readable. For this same reason, as well as
-for clarity, we have kept most statements short in the programs
-presented throughout the @value{DOCUMENT}.
-
-Backslash continuation is
-most useful when your @command{awk} program is in a separate source file
-instead of entered from the command line. You should also note that
-many @command{awk} implementations are more particular about where you
-may use backslash continuation. For example, they may not allow you to
-split a string constant using backslash continuation. Thus, for maximum
-portability of your @command{awk} programs, it is best not to split your
-lines in the middle of a regular expression or a string.
-@c 10/2000: gawk, mawk, and current bell labs awk allow it,
-@c solaris 2.7 nawk does not. Solaris /usr/xpg4/bin/awk does though! sigh.
-
-@cindex @command{csh} utility
-@cindex line continuations @subentry with C shell
-@cindex backslash (@code{\}) @subentry continuing lines and @subentry in
@command{csh}
-@cindex @code{\} (backslash) @subentry continuing lines and @subentry in
@command{csh}
-@quotation CAUTION
-@emph{Backslash continuation does not work as described
-with the C shell.} It works for @command{awk} programs in files and
-for one-shot programs, @emph{provided} you are using a POSIX-compliant
-shell, such as the Unix Bourne shell or Bash. But the C shell behaves
-differently! There you must use two backslashes in a row, followed by
-a newline. Note also that when using the C shell, @emph{every} newline
-in your @command{awk} program must be escaped with a backslash. To illustrate:
-
-@example
-% @kbd{awk 'BEGIN @{ \}
-? @kbd{ print \\}
-? @kbd{ "hello, world" \}
-? @kbd{@}'}
-@print{} hello, world
-@end example
-
-@noindent
-Here, the @samp{%} and @samp{?} are the C shell's primary and secondary
-prompts, analogous to the standard shell's @samp{$} and @samp{>}.
-
-Compare the previous example to how it is done with a POSIX-compliant shell:
-
-@example
-$ @kbd{awk 'BEGIN @{}
-> @kbd{print \}
-> @kbd{"hello, world"}
-> @kbd{@}'}
-@print{} hello, world
-@end example
-@end quotation
-
-@command{awk} is a line-oriented language. Each rule's action has to
-begin on the same line as the pattern. To have the pattern and action
-on separate lines, you @emph{must} use backslash continuation; there
-is no other option.
-
-@cindex backslash (@code{\}) @subentry continuing lines and @subentry comments
and
-@cindex @code{\} (backslash) @subentry continuing lines and @subentry comments
and
-@cindex commenting @subentry backslash continuation and
-Another thing to keep in mind is that backslash continuation and
-comments do not mix. As soon as @command{awk} sees the @samp{#} that
-starts a comment, it ignores @emph{everything} on the rest of the
-line. For example:
-
-@example
-@group
-$ @kbd{gawk 'BEGIN @{ print "dont panic" # a friendly \}
-> @kbd{ BEGIN rule}
-> @kbd{@}'}
-@error{} gawk: cmd. line:2: BEGIN rule
-@error{} gawk: cmd. line:2: ^ syntax error
-@end group
-@end example
-
-@noindent
-In this case, it looks like the backslash would continue the comment onto the
-next line. However, the backslash-newline combination is never even
-noticed because it is ``hidden'' inside the comment. Thus, the
-@code{BEGIN} is noted as a syntax error.
-
-@cindex dark corner @subentry backslash continuation on command line
-@cindex dark corner @subentry command line, backslash continuation on
-Backslash continuation comes into play in an additional, unexpected situation.
-Consider:
-
-@example
-gawk -F'\
-a' '@dots{}'
-@end example
-
-@noindent
-This command line assigns a value to @code{FS}. But what value?
-There are several possibilities, and in fact different versions of
-@command{awk} do different things. @command{gawk} treats this as
-if it were written:
-
-@example
-BEGIN @{ FS = "\
-a"
-@}
-@dots{}
-@end example
-
-@noindent
-In short, the backslash and newline are removed, assigning @code{"a"}
-to @code{FS}. This same treatment applies to variable assignments
-made with the @option{-v} option (@pxref{Options})
-and to regular command-line variable assignments (@pxref{Assignment Options}).
-
-If you're interested, see
-@uref{https://lists.gnu.org/archive/html/bug-gawk/2022-10/msg00025.html}
-for a source code patch that allows lines to be continued when inside
-parentheses. This patch was not added to @command{gawk} since it would
-quietly decrease the portability of @command{awk} programs.
-
-@cindex statements @subentry multiple
-@cindex @code{;} (semicolon) @subentry separating statements in actions
-@cindex semicolon (@code{;}) @subentry separating statements in actions
-@cindex @code{;} (semicolon) @subentry separating rules
-@cindex semicolon (@code{;}) @subentry separating rules
-When @command{awk} statements within one rule are short, you might want to put
-more than one of them on a line. This is accomplished by separating the
statements
-with a semicolon (@samp{;}).
-This also applies to the rules themselves.
-Thus, the program shown at the start of this @value{SECTION}
-could also be written this way:
-
-@example
-/12/ @{ print $0 @} ; /21/ @{ print $0 @}
-@end example
-
-@quotation NOTE
-The requirement that states that rules on the same line must be
-separated with a semicolon was not in the original @command{awk}
-language; it was added for consistency with the treatment of statements
-within an action.
-@end quotation
-
-@node Other Features
-@section Other Features of @command{awk}
-
-@cindex variables
-The @command{awk} language provides a number of predefined, or
-@dfn{built-in}, variables that your programs can use to get information
-from @command{awk}. There are other variables your program can set
-as well to control how @command{awk} processes your data.
-
-In addition, @command{awk} provides a number of built-in functions for doing
-common computational and string-related operations.
-@command{gawk} provides built-in functions for working with timestamps,
-performing bit manipulation, for runtime string translation
(internationalization),
-determining the type of a variable,
-and array sorting.
-
-As we develop our presentation of the @command{awk} language, we will introduce
-most of the variables and many of the functions. They are described
-systematically in @ref{Built-in Variables} and in
-@ref{Built-in}.
-
-@node When
-@section When to Use @command{awk}
-
-@cindex @command{awk} @subentry uses for
-Now that you've seen some of what @command{awk} can do,
-you might wonder how @command{awk} could be useful for you. By using
-utility programs, advanced patterns, field separators, arithmetic
-statements, and other selection criteria, you can produce much more
-complex output. The @command{awk} language is very useful for producing
-reports from large amounts of raw data, such as summarizing information
-from the output of other utility programs like @command{ls}.
-(@xref{More Complex}.)
-
-Programs written with @command{awk} are usually much smaller than they would
-be in other languages. This makes @command{awk} programs easy to compose and
-use. Often, @command{awk} programs can be quickly composed at your keyboard,
-used once, and thrown away. Because @command{awk} programs are interpreted,
you
-can avoid the (usually lengthy) compilation part of the typical
-edit-compile-test-debug cycle of software development.
-
-@cindex BWK @command{awk} @seeentry{Brian Kernighan's @command{awk}}
-@cindex Brian Kernighan's @command{awk}
-Complex programs have been written in @command{awk}, including a complete
-retargetable assembler for
-@ifclear FOR_PRINT
-eight-bit microprocessors (@pxref{Glossary}, for more information),
-@end ifclear
-@ifset FOR_PRINT
-eight-bit microprocessors,
-@end ifset
-and a microcode assembler for a special-purpose Prolog
-computer.
-The original @command{awk}'s capabilities were strained by tasks
-of such complexity, but modern versions are more capable.
-
-@cindex @command{awk} programs @subentry complex
-If you find yourself writing @command{awk} scripts of more than, say,
-a few hundred lines, you might consider using a different programming
-language. The shell is good at string and pattern matching; in addition,
-it allows powerful use of the system utilities. Python offers a nice
-balance between high-level ease of programming and access to system
-facilities.@footnote{Other popular scripting languages include Ruby
-and Perl.}
-
-@node Intro Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Programs in @command{awk} consist of @var{pattern}--@var{action} pairs.
-
-@item
-An @var{action} without a @var{pattern} always runs. The default
-@var{action} for a pattern without one is @samp{@{ print $0 @}}.
-
-@item
-Use either
-@samp{awk '@var{program}' @var{files}}
-or
-@samp{awk -f @var{program-file} @var{files}}
-to run @command{awk}.
-
-@item
-You may use the special @samp{#!} header line to create @command{awk}
-programs that are directly executable.
-
-@item
-Comments in @command{awk} programs start with @samp{#} and continue to
-the end of the same line.
-
-@item
-Be aware of quoting issues when writing @command{awk} programs as
-part of a larger shell script (or MS-Windows batch file).
-
-@item
-You may use backslash continuation to continue a source line.
-Lines are automatically continued after
-a comma, open brace, question mark, colon,
-@samp{||}, @samp{&&}, @code{do}, and @code{else}.
-@end itemize
-
-@node Invoking Gawk
-@chapter Running @command{awk} and @command{gawk}
-
-This @value{CHAPTER} covers how to run @command{awk}, both POSIX-standard
-and @command{gawk}-specific command-line options, and what
-@command{awk} and
-@command{gawk} do with nonoption arguments.
-It then proceeds to cover how @command{gawk} searches for source files,
-reading standard input along with other files, @command{gawk}'s
-environment variables, @command{gawk}'s exit status, using include files,
-and obsolete and undocumented options and/or features.
-
-Many of the options and features described here are discussed in
-more detail later in the @value{DOCUMENT}; feel free to skip over
-things in this @value{CHAPTER} that don't interest you right now.
-
-@menu
-* Command Line:: How to run @command{awk}.
-* Options:: Command-line options and their meanings.
-* Other Arguments:: Input file names and variable assignments.
-* Naming Standard Input:: How to specify standard input with other
- files.
-* Environment Variables:: The environment variables @command{gawk} uses.
-* Exit Status:: @command{gawk}'s exit status.
-* Include Files:: Including other files into your program.
-* Loading Shared Libraries:: Loading shared libraries into your program.
-* Obsolete:: Obsolete Options and/or features.
-* Undocumented:: Undocumented Options and Features.
-* Invoking Summary:: Invocation summary.
-@end menu
-
-@node Command Line
-@section Invoking @command{awk}
-@cindex command line @subentry invoking @command{awk} from
-@cindex @command{awk} @subentry invoking
-@cindex arguments @subentry command-line @subentry invoking @command{awk}
-@cindex options @subentry command-line @subentry invoking @command{awk}
-
-There are two ways to run @command{awk}---with an explicit program or with
-one or more program files. Here are templates for both of them; items
-enclosed in [@dots{}] in these templates are optional:
-
-@display
-@command{awk} [@var{options}] @option{-f} @var{progfile} [@option{--}]
@var{file} @dots{}
-@command{awk} [@var{options}] [@option{--}] @code{'@var{program}'} @var{file}
@dots{}
-@end display
-
-@cindex GNU long options
-@cindex long options
-@cindex options @subentry long
-In addition to traditional one-letter POSIX-style options, @command{gawk} also
-supports GNU long options.
-
-@cindex dark corner @subentry invoking @command{awk}
-@cindex lint checking @subentry empty programs
-It is possible to invoke @command{awk} with an empty program:
-
-@example
-awk '' datafile1 datafile2
-@end example
-
-@cindex @option{--lint} option
-@cindex dark corner @subentry empty programs
-@noindent
-Doing so makes little sense, though; @command{awk} exits
-silently when given an empty program.
-@value{DARKCORNER}
-If @option{--lint} has
-been specified on the command line, @command{gawk} issues a
-warning that the program is empty.
-
-@node Options
-@section Command-Line Options
-@cindex options @subentry command-line
-@cindex command line @subentry options
-@cindex GNU long options
-@cindex options @subentry long
-
-Options begin with a dash and consist of a single character.
-GNU-style long options consist of two dashes and a keyword.
-The keyword can be abbreviated, as long as the abbreviation allows the option
-to be uniquely identified. If the option takes an argument, either the
-keyword is immediately followed by an equals sign (@samp{=}) and the
-argument's value, or the keyword and the argument's value are separated
-by whitespace (spaces or TABs).
-If a particular option with a value is given more than once, it is (usually)
-the last value that counts.
-
-@cindex POSIX @command{awk} @subentry GNU long options and
-Each long option for @command{gawk} has a corresponding
-POSIX-style short option.
-The long and short options are
-interchangeable in all contexts.
-The following list describes options mandated by the POSIX standard:
-
-@table @code
-@item -F @var{fs}
-@itemx --field-separator @var{fs}
-@cindex @option{-F} option
-@cindex @option{--field-separator} option
-@cindex @code{FS} variable @subentry @option{--field-separator} option and
-Set the @code{FS} variable to @var{fs}
-(@pxref{Field Separators}).
-
-@item -f @var{source-file}
-@itemx --file @var{source-file}
-@cindex @option{-f} option
-@cindex @option{--file} option
-@cindex @command{awk} programs @subentry location of
-Read the @command{awk} program source from @var{source-file}
-instead of in the first nonoption argument.
-This option may be given multiple times; the @command{awk}
-program consists of the concatenation of the contents of
-each specified @var{source-file}.
-
-Files named with @option{-f} are treated as if they had @samp{@@namespace
"awk"}
-at their beginning. @xref{Changing The Namespace}, for more information
-on this advanced feature.
-
-@item -v @var{var}=@var{val}
-@itemx --assign @var{var}=@var{val}
-@cindex @option{-v} option
-@cindex @option{--assign} option
-@cindex variables @subentry setting
-Set the variable @var{var} to the value @var{val} @emph{before}
-execution of the program begins. Such variable values are available
-inside the @code{BEGIN} rule
-(@pxref{Other Arguments}).
-
-The @option{-v} option can only set one variable, but it can be used
-more than once, setting another variable each time, like this:
-@samp{awk @w{-v foo=1} @w{-v bar=2} @dots{}}.
-
-@cindex predefined variables @subentry @code{-v} option, setting with
-@cindex variables @subentry predefined @subentry @code{-v} option, setting with
-@quotation CAUTION
-Using @option{-v} to set the values of the built-in
-variables may lead to surprising results. @command{awk} will reset the
-values of those variables as it needs to, possibly ignoring any
-initial value you may have given.
-@end quotation
-
-@item -W @var{gawk-opt}
-@cindex @option{-W} option
-Provide an implementation-specific option.
-This is the POSIX convention for providing implementation-specific options.
-These options
-also have corresponding GNU-style long options.
-Note that the long options may be abbreviated, as long as
-the abbreviations remain unique.
-The full list of @command{gawk}-specific options is provided next.
-
-@item --
-@cindex command line @subentry options @subentry end of
-@cindex options @subentry command-line @subentry end of
-Signal the end of the command-line options. The following arguments
-are not treated as options even if they begin with @samp{-}. This
-interpretation of @option{--} follows the POSIX argument parsing
-conventions.
-
-@cindex @code{-} (hyphen) @subentry file names beginning with
-@cindex hyphen (@code{-}) @subentry file names beginning with
-This is useful if you have @value{FN}s that start with @samp{-},
-or in shell scripts, if you have @value{FN}s that will be specified
-by the user that could start with @samp{-}.
-It is also useful for passing options on to the @command{awk}
-program; see @ref{Getopt Function}.
-@end table
-
-The following list describes @command{gawk}-specific options:
-
-@c Have to use @asis here to get docbook to come out right.
-@table @asis
-@item @option{-b}
-@itemx @option{--characters-as-bytes}
-@cindex @option{-b} option
-@cindex @option{--characters-as-bytes} option
-Cause @command{gawk} to treat all input data as single-byte characters.
-In addition, all output written with @code{print} or @code{printf}
-is treated as single-byte characters.
-
-Normally, @command{gawk} follows the POSIX standard and attempts to process
-its input data according to the current locale (@pxref{Locales}). This can
often involve
-converting multibyte characters into wide characters (internally), and
-can lead to problems or confusion if the input data does not contain valid
-multibyte characters. This option is an easy way to tell @command{gawk},
-``Hands off my data!''
-
-@item @option{-c}
-@itemx @option{--traditional}
-@cindex @option{-c} option
-@cindex @option{--traditional} option
-@cindex compatibility mode (@command{gawk}) @subentry specifying
-Specify @dfn{compatibility mode}, in which the GNU extensions to
-the @command{awk} language are disabled, so that @command{gawk} behaves just
-like BWK @command{awk}.
-@xref{POSIX/GNU},
-which summarizes the extensions.
-@ifclear FOR_PRINT
-Also see
-@ref{Compatibility Mode}.
-@end ifclear
-
-@item @option{-C}
-@itemx @option{--copyright}
-@cindex @option{-C} option
-@cindex @option{--copyright} option
-@cindex GPL (General Public License) @subentry printing
-Print the short version of the General Public License and then exit.
-
-@item @option{-d}[@var{file}]
-@itemx @option{--dump-variables}[@code{=}@var{file}]
-@cindex @option{-d} option
-@cindex @option{--dump-variables} option
-@cindex dump all variables of a program
-@cindex @file{awkvars.out} file
-@cindex files @subentry @file{awkvars.out}
-@cindex variables @subentry global @subentry printing list of
-Print a sorted list of global variables, their types, and final values
-to @var{file}. If no @var{file} is provided, print this
-list to a file named @file{awkvars.out} in the current directory.
-No space is allowed between the @option{-d} and @var{file}, if
-@var{file} is supplied.
-
-@cindex troubleshooting @subentry typographical errors, global variables
-Having a list of all global variables is a good way to look for
-typographical errors in your programs.
-You would also use this option if you have a large program with a lot of
-functions, and you want to be sure that your functions don't
-inadvertently use global variables that you meant to be local.
-(This is a particularly easy mistake to make with simple variable
-names like @code{i}, @code{j}, etc.)
-
-@item @option{-D}[@var{file}]
-@itemx @option{--debug}[@code{=}@var{file}]
-@cindex @option{-D} option
-@cindex @option{--debug} option
-@cindex @command{awk} programs @subentry debugging, enabling
-Enable debugging of @command{awk} programs
-(@pxref{Debugging}).
-By default, the debugger reads commands interactively from the keyboard
-(standard input).
-The optional @var{file} argument allows you to specify a file with a list
-of commands for the debugger to execute noninteractively.
-No space is allowed between the @option{-D} and @var{file}, if
-@var{file} is supplied.
-
-@item @option{-e} @var{program-text}
-@itemx @option{--source} @var{program-text}
-@cindex @option{-e} option
-@cindex @option{--source} option
-@cindex source code @subentry mixing
-Provide program source code in the @var{program-text}.
-This option allows you to mix source code in files with source
-code that you enter on the command line.
-This is particularly useful
-when you have library functions that you want to use from your command-line
-programs (@pxref{AWKPATH Variable}).
-
-Note that @command{gawk} treats each string as if it ended with
-a newline character (even if it doesn't). This makes building
-the total program easier.
-
-@quotation CAUTION
-Prior to @value{PVERSION} 5.0, there was
-no requirement that each @var{program-text}
-be a full syntactic unit. I.e., the following worked:
-
-@example
-$ @kbd{gawk -e 'BEGIN @{ a = 5 ;' -e 'print a @}'}
-@print{} 5
-@end example
-
-@noindent
-However, this is no longer true. If you have any scripts that
-rely upon this feature, you should revise them.
-
-This is because each @var{program-text} is treated as if it had
-@samp{@@namespace "awk"} at its beginning. @xref{Changing The Namespace},
-for more information.
-@end quotation
-
-@item @option{-E} @var{file}
-@itemx @option{--exec} @var{file}
-@cindex @option{-E} option
-@cindex @option{--exec} option
-@cindex @command{awk} programs @subentry location of
-@cindex CGI, @command{awk} scripts for
-Similar to @option{-f}, read @command{awk} program text from @var{file}.
-There are two differences from @option{-f}:
-
-@itemize @value{BULLET}
-@item
-This option terminates option processing; anything
-else on the command line is passed on directly to the @command{awk} program.
-
-@item
-Command-line variable assignments of the form
-@samp{@var{var}=@var{value}} are disallowed.
-@end itemize
-
-This option is particularly necessary for World Wide Web CGI applications
-that pass arguments through the URL; using this option prevents a malicious
-(or other) user from passing in options, assignments, or @command{awk} source
-code (via @option{-e}) to the CGI application.@footnote{For more detail,
-please see Section 4.4 of @uref{http://www.ietf.org/rfc/rfc3875,
-RFC 3875}. Also see the
-@uref{https://lists.gnu.org/archive/html/bug-gawk/2014-11/msg00022.html,
-explanatory note sent to the @command{gawk} bug
-mailing list}.}
-This option should be used
-with @samp{#!} scripts (@pxref{Executable Scripts}), like so:
-
-@example
-#! /usr/local/bin/gawk -E
-
-@var{awk program here @dots{}}
-@end example
-
-@item @option{-g}
-@itemx @option{--gen-pot}
-@cindex @option{-g} option
-@cindex @option{--gen-pot} option
-@cindex portable object @subentry files @subentry generating
-@cindex files @subentry portable object @subentry generating
-Analyze the source program and
-generate a GNU @command{gettext} portable object template file on standard
-output for all string constants that have been marked for translation.
-@xref{Internationalization},
-for information about this option.
-
-@item @option{-h}
-@itemx @option{--help}
-@cindex @option{-h} option
-@cindex @option{--help} option
-@cindex GNU long options @subentry printing list of
-@cindex options @subentry printing list of
-@cindex printing @subentry list of options
-Print a ``usage'' message summarizing the short- and long-style options
-that @command{gawk} accepts and then exit.
-
-@item @option{-i} @var{source-file}
-@itemx @option{--include} @var{source-file}
-@cindex @option{-i} option
-@cindex @option{--include} option
-@cindex @command{awk} programs @subentry location of
-Read an @command{awk} source library from @var{source-file}. This option
-is completely equivalent to using the @code{@@include} directive inside
-your program. It is very similar to the @option{-f} option,
-but there are two important differences. First, when @option{-i} is
-used, the program source is not loaded if it has been previously
-loaded, whereas with @option{-f}, @command{gawk} always loads the file.
-Second, because this option is intended to be used with code libraries,
-@command{gawk} does not recognize such files as constituting main program
-input. Thus, after processing an @option{-i} argument, @command{gawk}
-still expects to find the main source code via the @option{-f} option
-or on the command line.
-
-Files named with @option{-i} are treated as if they had @samp{@@namespace
"awk"}
-at their beginning. @xref{Changing The Namespace}, for more information.
-
-@item @option{-I}
-@itemx @option{--trace}
-@cindex @option{-I} option
-@cindex @option{--trace} option
-@cindex trace, internal instructions
-@cindex instructions, trace of internal
-@cindex op-codes, trace of internal
-Print the internal byte code names as they are executed when running
-the program. The trace is printed to standard error. Each ``op code''
-is preceded by a @code{+}
-sign in the output.
-
-@item @option{-k}
-@itemx @option{--csv}
-@cindex @option{-k} option
-@cindex @option{--csv} option
-@cindex comma separated values (CSV) data @subentry @option{-k} option
-@cindex comma separated values (CSV) data @subentry @option{--csv} option
-@cindex CSV (comma separated values) data @subentry @option{-k} option
-@cindex CSV (comma separated values) data @subentry @option{--csv} option
-Enable special processing for files with comma separated values
-(CSV). @xref{Comma Separated Fields}.
-This option cannot be used with @option{--posix}. Attempting to do
-causes a fatal error.
-
-@item @option{-l} @var{ext}
-@itemx @option{--load} @var{ext}
-@cindex @option{-l} option
-@cindex @option{--load} option
-@cindex loading extensions
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-Load a dynamic extension named @var{ext}. Extensions
-are stored as system shared libraries.
-This option searches for the library using the @env{AWKLIBPATH}
-environment variable. The correct library suffix for your platform will be
-supplied by default, so it need not be specified in the extension name.
-The extension initialization routine should be named @code{dl_load()}.
-An alternative is to use the @code{@@load} keyword inside the program to load
-a shared library. This advanced feature is described in detail in
@ref{Dynamic Extensions}.
-
-@item @option{-L}[@var{value}]
-@itemx @option{--lint}[@code{=}@var{value}]
-@cindex @option{-l} option
-@cindex @option{--lint} option
-@cindex lint checking @subentry issuing warnings
-@cindex warnings, issuing
-Warn about constructs that are dubious or nonportable to
-other @command{awk} implementations.
-No space is allowed between the @option{-L} and @var{value}, if
-@var{value} is supplied.
-Some warnings are issued when @command{gawk} first reads your program. Others
-are issued at runtime, as your program executes. The optional
-argument may be one of the following:
-
-@table @code
-@item fatal
-Cause lint warnings become fatal errors.
-This may be drastic, but its use will certainly encourage the
-development of cleaner @command{awk} programs.
-
-@item invalid
-Only issue warnings about things
-that are actually invalid are issued. (This is not fully implemented yet.)
-
-@item no-ext
-Disable warnings about @command{gawk} extensions.
-@end table
-
-Some warnings are only printed once, even if the dubious constructs they
-warn about occur multiple times in your @command{awk} program. Thus,
-when eliminating problems pointed out by @option{--lint}, you should take
-care to search for all occurrences of each inappropriate construct. As
-@command{awk} programs are usually short, doing so is not burdensome.
-
-@item @option{-M}
-@itemx @option{--bignum}
-@cindex @option{-M} option
-@cindex @option{--bignum} option
-Select arbitrary-precision arithmetic on numbers. This option has no effect
-if @command{gawk} is not compiled to use the GNU MPFR and MP libraries
-(@pxref{Arbitrary Precision Arithmetic}).
-
-@ignore
-@cindex @env{GAWK_NO_MPFR_WARN} environment variable
-@cindex environment variables @subentry @env{GAWK_NO_MPFR_WARN}
-@end ignore
-As of @value{PVERSION} 5.2,
-the arbitrary precision arithmetic features in @command{gawk}
-are ``on parole.''
-The primary maintainer is no longer willing to support this feature,
-but another member of the development team has stepped up to take it over.
-As long as this situation remains stable, MPFR will be supported. If it
-changes, the MPFR support will be removed from @command{gawk}.
-@ignore
-If you use this option, @command{gawk} generates a warning message.
-Create the environment variable @env{GAWK_NO_MPFR_WARN} with an arbitrary
-value in order to silence the warning.
-@end ignore
-
-@item @option{-n}
-@itemx @option{--non-decimal-data}
-@cindex @option{-n} option
-@cindex @option{--non-decimal-data} option
-@cindex hexadecimal values, enabling interpretation of
-@cindex octal values, enabling interpretation of
-@cindex troubleshooting @subentry @option{--non-decimal-data} option
-Enable automatic interpretation of octal and hexadecimal
-values in input data
-(@pxref{Nondecimal Data}).
-
-@quotation CAUTION
-This option can severely break old programs. Use with care. Also note
-that this option may disappear in a future version of @command{gawk}.
-@end quotation
-
-@item @option{-N}
-@itemx @option{--use-lc-numeric}
-@cindex @option{-N} option
-@cindex @option{--use-lc-numeric} option
-Force the use of the locale's decimal point character
-when parsing numeric input data (@pxref{Locales}).
-
-@cindex pretty printing
-@item @option{-o}[@var{file}]
-@itemx @option{--pretty-print}[@code{=}@var{file}]
-@cindex @option{-o} option
-@cindex @option{--pretty-print} option
-Enable pretty-printing of @command{awk} programs.
-Implies @option{--no-optimize}.
-By default, the output program is created in a file named @file{awkprof.out}
-(@pxref{Profiling}).
-The optional @var{file} argument allows you to specify a different
-@value{FN} for the output.
-No space is allowed between the @option{-o} and @var{file}, if
-@var{file} is supplied.
-
-@quotation NOTE
-In the past, this option would also execute your program.
-This is no longer the case.
-@end quotation
-
-@item @option{-O}
-@itemx @option{--optimize}
-@cindex @option{--optimize} option
-@cindex @option{-O} option
-Enable @command{gawk}'s default optimizations on the internal
-representation of the program. At the moment, this includes just simple
-constant folding.
-
-Optimization is enabled by default.
-This option remains primarily for backwards compatibility. However, it may
-be used to cancel the effect of an earlier @option{-s} option
-(see later in this list).
-
-@item @option{-p}[@var{file}]
-@itemx @option{--profile}[@code{=}@var{file}]
-@cindex @option{-p} option
-@cindex @option{--profile} option
-@cindex @command{awk} @subentry profiling, enabling
-Enable profiling of @command{awk} programs
-(@pxref{Profiling}).
-Implies @option{--no-optimize}.
-By default, profiles are created in a file named @file{awkprof.out}.
-The optional @var{file} argument allows you to specify a different
-@value{FN} for the profile file.
-No space is allowed between the @option{-p} and @var{file}, if
-@var{file} is supplied.
-
-The profile contains execution counts for each statement in the program
-in the left margin, and function call counts for each function.
-
-@item @option{-P}
-@itemx @option{--posix}
-@cindex @option{-P} option
-@cindex @option{--posix} option
-@cindex POSIX mode
-@cindex @command{gawk} @subentry extensions, disabling
-Operate in strict POSIX mode. This disables all @command{gawk}
-extensions (just like @option{--traditional}) and
-disables all extensions not allowed by POSIX.
-@xref{Common Extensions} for a summary of the extensions
-in @command{gawk} that are disabled by this option.
-Also,
-the following additional
-restrictions apply:
-
-@itemize @value{BULLET}
-
-@cindex newlines
-@cindex whitespace @subentry newlines as
-@item
-Newlines are not allowed after @samp{?} or @samp{:}
-(@pxref{Conditional Exp}).
-
-
-@cindex @code{FS} variable @subentry TAB character as
-@item
-Specifying @samp{-Ft} on the command line does not set the value
-of @code{FS} to be a single TAB character
-(@pxref{Field Separators}).
-
-@cindex locale decimal point character
-@cindex decimal point character, locale specific
-@item
-The locale's decimal point character is used for parsing input
-data (@pxref{Locales}).
-@end itemize
-
-@c @cindex automatic warnings
-@c @cindex warnings, automatic
-@cindex @option{--traditional} option @subentry @option{--posix} option and
-@cindex @option{--posix} option @subentry @option{--traditional} option and
-If you supply both @option{--traditional} and @option{--posix} on the
-command line, @option{--posix} takes precedence. @command{gawk}
-issues a warning if both options are supplied.
-
-@item @option{-r}
-@itemx @option{--re-interval}
-@cindex @option{-r} option
-@cindex @option{--re-interval} option
-@cindex regular expressions @subentry interval expressions and
-Allow interval expressions
-(@pxref{Regexp Operators})
-in regexps.
-This is now @command{gawk}'s default behavior.
-Nevertheless, this option remains for backward compatibility.
-
-@item @option{-s}
-@itemx @option{--no-optimize}
-@cindex @option{--no-optimize} option
-@cindex @option{-s} option
-Disable @command{gawk}'s default optimizations on the internal
-representation of the program.
-
-@item @option{-S}
-@itemx @option{--sandbox}
-@cindex @option{-S} option
-@cindex @option{--sandbox} option
-@cindex sandbox mode
-@cindex @code{ARGV} array
-Disable the @code{system()} function,
-input redirections with @code{getline},
-output redirections with @code{print} and @code{printf},
-and dynamic extensions.
-Also, disallow adding @value{FN}s to @code{ARGV} that were
-not there when @command{gawk} started running.
-This is particularly useful when you want to run @command{awk} scripts
-from questionable sources and need to make sure the scripts
-can't access your system (other than the specified input @value{DF}s).
-
-@item @option{-t}
-@itemx @option{--lint-old}
-@cindex @option{-L} option
-@cindex @option{--lint-old} option
-Warn about constructs that are not available in the original version of
-@command{awk} from Version 7 Unix
-(@pxref{V7/SVR3.1}).
-
-@item @option{-V}
-@itemx @option{--version}
-@cindex @option{-V} option
-@cindex @option{--version} option
-@cindex @command{gawk} @subentry version of @subentry printing information
about
-Print version information for this particular copy of @command{gawk}.
-This allows you to determine if your copy of @command{gawk} is up to date
-with respect to whatever the Free Software Foundation is currently
-distributing.
-It is also useful for bug reports
-(@pxref{Bugs}).
-
-@cindex @code{-} (hyphen) @subentry @code{--} end of options marker
-@cindex hyphen (@code{-}) @subentry @code{--} end of options marker
-@item @code{--}
-Mark the end of all options.
-Any command-line arguments following @code{--} are placed in @code{ARGV},
-even if they start with a minus sign.
-@end table
-
-In compatibility mode,
-as long as program text has been supplied,
-any other options are flagged as invalid with a warning message but
-are otherwise ignored.
-
-@cindex @option{-F} option @subentry @option{-Ft} sets @code{FS} to TAB
-In compatibility mode, as a special case, if the value of @var{fs} supplied
-to the @option{-F} option is @samp{t}, then @code{FS} is set to the TAB
-character (@code{"\t"}). This is true only for @option{--traditional} and not
-for @option{--posix}
-(@pxref{Field Separators}).
-
-@cindex @option{-f} option @subentry multiple uses
-The @option{-f} option may be used more than once on the command line.
-If it is, @command{awk} reads its program source from all of the named files,
as
-if they had been concatenated together into one big file. This is
-useful for creating libraries of @command{awk} functions. These functions
-can be written once and then retrieved from a standard place, instead
-of having to be included in each individual program.
-The @option{-i} option is similar in this regard.
-(As mentioned in
-@ref{Definition Syntax},
-function names must be unique.)
-
-With standard @command{awk}, library functions can still be used, even
-if the program is entered at the keyboard,
-by specifying @samp{-f /dev/tty}. After typing your program,
-type @kbd{Ctrl-d} (the end-of-file character) to terminate it.
-(You may also use @samp{-f -} to read program source from the standard
-input, but then you will not be able to also use the standard input as a
-source of data.)
-
-Because it is clumsy using the standard @command{awk} mechanisms to mix
-source file and command-line @command{awk} programs, @command{gawk}
-provides the @option{-e} option. This does not require you to
-preempt the standard input for your source code, and it allows you to easily
-mix command-line and library source code (@pxref{AWKPATH Variable}).
-As with @option{-f}, the @option{-e} and @option{-i}
-options may also be used multiple times on the command line.
-
-@cindex @option{-e} option
-If no @option{-f} option (or @option{-e} option for @command{gawk})
-is specified, then @command{awk} uses the first nonoption command-line
-argument as the text of the program source code. Arguments on
-the command line that follow the program text are entered into the
-@code{ARGV} array; @command{awk} does @emph{not} continue to parse the
-command line looking for options.
-
-@cindex @env{POSIXLY_CORRECT} environment variable
-@cindex environment variables @subentry @env{POSIXLY_CORRECT}
-@cindex lint checking @subentry @env{POSIXLY_CORRECT} environment variable
-@cindex POSIX mode
-If the environment variable @env{POSIXLY_CORRECT} exists,
-then @command{gawk} behaves in strict POSIX mode, exactly as if
-you had supplied @option{--posix}.
-Many GNU programs look for this environment variable to suppress
-extensions that conflict with POSIX, but @command{gawk} behaves
-differently: it suppresses all extensions, even those that do not
-conflict with POSIX, and behaves in
-strict POSIX mode. If @option{--lint} is supplied on the command line
-and @command{gawk} turns on POSIX mode because of @env{POSIXLY_CORRECT},
-then it issues a warning message indicating that POSIX
-mode is in effect.
-You would typically set this variable in your shell's startup file.
-For a Bourne-compatible shell (such as Bash), you would add these
-lines to the @file{.profile} file in your home directory:
-
-@example
-POSIXLY_CORRECT=true
-export POSIXLY_CORRECT
-@end example
-
-@cindex @command{csh} utility @subentry @env{POSIXLY_CORRECT} environment
variable
-For a C shell-compatible
-shell,@footnote{Not recommended.}
-you would add this line to the @file{.login} file in your home directory:
-
-@example
-setenv POSIXLY_CORRECT true
-@end example
-
-@cindex portability @subentry @env{POSIXLY_CORRECT} environment variable
-Having @env{POSIXLY_CORRECT} set is not recommended for daily use,
-but it is good for testing the portability of your programs to other
-environments.
-
-@node Other Arguments
-@section Other Command-Line Arguments
-@cindex command line @subentry arguments
-@cindex arguments @subentry command-line
-
-Any additional arguments on the command line are normally treated as
-input files to be processed in the order specified. However, an
-argument that has the form @code{@var{var}=@var{value}}, assigns
-the value @var{value} to the variable @var{var}---it does not specify a
-file at all. (See @ref{Assignment Options}.) In the following example,
-@samp{count=1} is a variable assignment, not a @value{FN}:
-
-@example
-awk -f program.awk file1 count=1 file2
-@end example
-
-@noindent
-As a side point, should you really need to have @command{awk}
-process a file named @file{count=1} (or any file whose name looks like
-a variable assignment), precede the file name with @samp{./}, like so:
-
-@example
-awk -f program.awk file1 ./count=1 file2
-@end example
-
-@cindex @command{gawk} @subentry @code{ARGIND} variable in
-@cindex @code{ARGIND} variable @subentry command-line arguments
-@cindex @code{ARGV} array, indexing into
-@cindex @code{ARGC}/@code{ARGV} variables @subentry command-line arguments
-@cindex @command{gawk} @subentry @code{PROCINFO} array in
-All the command-line arguments are made available to your @command{awk}
program in the
-@code{ARGV} array (@pxref{Built-in Variables}). Command-line options
-and the program text (if present) are omitted from @code{ARGV}.
-All other arguments, including variable assignments, are
-included. As each element of @code{ARGV} is processed, @command{gawk}
-sets @code{ARGIND} to the index in @code{ARGV} of the
-current element. (@command{gawk} makes the full command line,
-including program text and options, available in @code{PROCINFO["argv"]};
-@pxref{Auto-set}.)
-
-Changing @code{ARGC} and @code{ARGV} in your @command{awk} program lets
-you control how @command{awk} processes the input files; this is described
-in more detail in @ref{ARGC and ARGV}.
-
-@cindex input files @subentry variable assignments and
-@cindex variable assignments and input files
-The distinction between @value{FN} arguments and variable-assignment
-arguments is made when @command{awk} is about to open the next input file.
-At that point in execution, it checks the @value{FN} to see whether
-it is really a variable assignment; if so, @command{awk} sets the variable
-instead of reading a file.
-
-Therefore, the variables actually receive the given values after all
-previously specified files have been read. In particular, the values of
-variables assigned in this fashion are @emph{not} available inside a
-@code{BEGIN} rule
-(@pxref{BEGIN/END}),
-because such rules are run before @command{awk} begins scanning the argument
list.
-
-@cindex dark corner @subentry escape sequences
-The variable values given on the command line are processed for escape
-sequences (@pxref{Escape Sequences}).
-@value{DARKCORNER}
-
-In some very early implementations of @command{awk}, when a variable assignment
-occurred before any @value{FN}s, the assignment would happen @emph{before}
-the @code{BEGIN} rule was executed. @command{awk}'s behavior was thus
-inconsistent; some command-line assignments were available inside the
-@code{BEGIN} rule, while others were not. Unfortunately,
-some applications came to depend
-upon this ``feature.'' When @command{awk} was changed to be more consistent,
-the @option{-v} option was added to accommodate applications that depended
-upon the old behavior.
-
-The variable assignment feature is most useful for assigning to variables
-such as @code{RS}, @code{OFS}, and @code{ORS}, which control input and
-output formats, before scanning the @value{DF}s. It is also useful for
-controlling state if multiple passes are needed over a @value{DF}. For
-example:
-
-@cindex files @subentry multiple passes over
-@example
-awk 'pass == 1 @{ @var{pass 1 stuff} @}
- pass == 2 @{ @var{pass 2 stuff} @}' pass=1 mydata pass=2 mydata
-@end example
-
-Given the variable assignment feature, the @option{-F} option for setting
-the value of @code{FS} is not
-strictly necessary. It remains for historical compatibility.
-
-@sidebar Quoting Shell Variables On The @command{awk} Command Line
-@cindex quoting @subentry in @command{gawk} command lines
-@cindex shell quoting, rules for
-@cindex null strings @subentry in @command{gawk} arguments, quoting and
-
-Small @command{awk} programs are often embedded in larger shell scripts,
-so it's worthwhile to understand some shell basics. Consider the following:
-
-@example
-f=""
-awk '@{ print("hi") @}' $f
-@end example
-
-In this case, @command{awk} reads from standard input instead of trying
-to open any command line files. To the unwary, this looks like @command{awk}
-is hanging.
-
-However @command{awk} doesn't see an explicit empty string. When a
-variable expansion is the null string, @emph{and} it's not quoted,
-the shell simply removes it from the command line. To demonstrate:
-
-@example
-$ @kbd{f=""}
-$ @kbd{awk 'BEGIN @{ print ARGC @}' $f}
-@print{} 1
-$ @kbd{awk 'BEGIN @{ print ARGC @}' "$f"}
-@print{} 2
-@end example
-@end sidebar
-
-@node Naming Standard Input
-@section Naming Standard Input
-
-Often, you may wish to read standard input together with other files.
-For example, you may wish to read one file, read standard input coming
-from a pipe, and then read another file.
-
-The way to name the standard input, with all versions of @command{awk},
-is to use a single, standalone minus sign or dash, @samp{-}. For example:
-
-@example
-@var{some_command} | awk -f myprog.awk file1 - file2
-@end example
-
-@noindent
-Here, @command{awk} first reads @file{file1}, then it reads
-the output of @var{some_command}, and finally it reads
-@file{file2}.
-
-You may also use @code{"-"} to name standard input when reading
-files with @code{getline} (@pxref{Getline/File}).
-And, you can even use @code{"-"} with the @option{-f} option
-to read program source code from standard input (@pxref{Options}).
-
-In addition, @command{gawk} allows you to specify the special
-@value{FN} @file{/dev/stdin}, both on the command line and
-with @code{getline}.
-Some other versions of @command{awk} also support this, but it
-is not standard.
-(Some operating systems provide a @file{/dev/stdin} file
-in the filesystem; however, @command{gawk} always processes
-this @value{FN} itself.)
-
-@node Environment Variables
-@section The Environment Variables @command{gawk} Uses
-@cindex environment variables @subentry used by @command{gawk}
-
-A number of environment variables influence how @command{gawk}
-behaves.
-
-@menu
-* AWKPATH Variable:: Searching directories for @command{awk}
- programs.
-* AWKLIBPATH Variable:: Searching directories for @command{awk} shared
- libraries.
-* Other Environment Variables:: The environment variables.
-@end menu
-
-@node AWKPATH Variable
-@subsection The @env{AWKPATH} Environment Variable
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-@cindex directories @subentry searching @subentry for source files
-@cindex search paths @subentry for source files
-@cindex differences in @command{awk} and @command{gawk} @subentry
@env{AWKPATH} environment variable
-@ifinfo
-The previous @value{SECTION} described how @command{awk} program files can be
named
-on the command line with the @option{-f} option.
-@end ifinfo
-In most @command{awk}
-implementations, you must supply a precise pathname for each program
-file, unless the file is in the current directory.
-But with @command{gawk}, if the @value{FN} supplied to the @option{-f}
-or @option{-i} options
-does not contain a directory separator @samp{/}, then @command{gawk} searches
a list of
-directories (called the @dfn{search path}) one by one, looking for a
-file with the specified name.
-
-The search path is a string consisting of directory names
-separated by colons.@footnote{Semicolons on MS-Windows.}
-@command{gawk} gets its search path from the
-@env{AWKPATH} environment variable. If that variable does not exist,
-or if it has an empty value,
-@command{gawk} uses a default path (described shortly).
-
-The search path feature is particularly helpful for building libraries
-of useful @command{awk} functions. The library files can be placed in a
-standard directory in the default path and then specified on
-the command line with a short @value{FN}. Otherwise, you would have to
-type the full @value{FN} for each file.
-
-By using the @option{-i} or @option{-f} options, your command-line
-@command{awk} programs can use facilities in @command{awk} library files
-(@pxref{Library Functions}).
-Path searching is not done if @command{gawk} is in compatibility mode.
-This is true for both @option{--traditional} and @option{--posix}.
-@xref{Options}.
-
-If the source code file is not found after the initial search, the path is
searched
-again after adding the suffix @samp{.awk} to the @value{FN}.
-
-@command{gawk}'s path search mechanism is similar
-to the shell's.
-(See @uref{https://www.gnu.org/software/bash/manual/,
-@cite{The Bourne-Again SHell manual}}.)
-It treats a null entry in the path as indicating the current
-directory.
-(A null entry is indicated by starting or ending the path with a
-colon or by placing two colons next to each other [@samp{::}].)
-
-@quotation NOTE
-To include the current directory in the path, either place @file{.}
-as an entry in the path or write a null entry in the path.
-
-Different past versions of @command{gawk} would also look explicitly in
-the current directory, either before or after the path search. As of
-@value{PVERSION} 4.1.2, this no longer happens; if you wish to look
-in the current directory, you must include @file{.} either as a separate
-entry or as a null entry in the search path.
-@end quotation
-
-The default value for @env{AWKPATH} is
-@samp{.:/usr/local/share/awk}.@footnote{Your version of @command{gawk}
-may use a different directory; it
-will depend upon how @command{gawk} was built and installed. The actual
-directory is the value of @code{$(pkgdatadir)} generated when
-@command{gawk} was configured.
-(For more detail, see the @file{INSTALL} file in the source distribution,
-and see @ref{Quick Installation}.
-You probably don't need to worry about this,
-though.)} Since @file{.} is included at the beginning, @command{gawk}
-searches first in the current directory and then in
@file{/usr/local/share/awk}.
-In practice, this means that you will rarely need to change the
-value of @env{AWKPATH}.
-
-@xref{Shell Startup Files}, for information on functions that help to
-manipulate the @env{AWKPATH} variable.
-
-@command{gawk} places the value of the search path that it used into
-@code{ENVIRON["AWKPATH"]}. This provides access to the actual search
-path value from within an @command{awk} program.
-
-Although you can change @code{ENVIRON["AWKPATH"]} within your @command{awk}
-program, this has no effect on the running program's behavior. This makes
-sense: the @env{AWKPATH} environment variable is used to find the program
-source files. Once your program is running, all the files have been
-found, and @command{gawk} no longer needs to use @env{AWKPATH}.
-
-@node AWKLIBPATH Variable
-@subsection The @env{AWKLIBPATH} Environment Variable
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-@cindex directories @subentry searching @subentry for loadable extensions
-@cindex search paths @subentry for loadable extensions
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{AWKLIBPATH} environment variable
-
-The @env{AWKLIBPATH} environment variable is similar to the @env{AWKPATH}
-variable, but it is used to search for loadable extensions (stored as
-system shared libraries) specified with the @option{-l} option rather
-than for source files. If the extension is not found, the path is
-searched again after adding the appropriate shared library suffix for
-the platform. For example, on GNU/Linux systems, the suffix @samp{.so}
-is used. The search path specified is also used for extensions loaded
-via the @code{@@load} keyword (@pxref{Loading Shared Libraries}).
-
-If @env{AWKLIBPATH} does not exist in the environment, or if it has
-an empty value, @command{gawk} uses a default path; this
-is typically @samp{/usr/local/lib/gawk}, although it can vary depending
-upon how @command{gawk} was built.@footnote{Your version of @command{gawk}
-may use a different directory; it
-will depend upon how @command{gawk} was built and installed. The actual
-directory is the value of @code{$(pkgextensiondir)} generated when
-@command{gawk} was configured.
-(For more detail, see the @file{INSTALL} file in the source distribution,
-and see @ref{Quick Installation}.
-You probably don't need to worry about this,
-though.)}
-
-@xref{Shell Startup Files}, for information on functions that help to
-manipulate the @env{AWKLIBPATH} variable.
-
-@command{gawk} places the value of the search path that it used into
-@code{ENVIRON["AWKLIBPATH"]}. This provides access to the actual search
-path value from within an @command{awk} program.
-
-Although you can change @code{ENVIRON["AWKLIBPATH"]} within your
-@command{awk} program, this has no effect on the running program's
-behavior. This makes sense: the @env{AWKLIBPATH} environment variable
-is used to find any requested extensions, and they are loaded before
-the program starts to run. Once your program is running, all the
-extensions have been found, and @command{gawk} no longer needs to use
-@env{AWKLIBPATH}.
-
-@node Other Environment Variables
-@subsection Other Environment Variables
-
-A number of other environment variables affect @command{gawk}'s
-behavior, but they are more specialized. Those in the following
-list are meant to be used by regular users:
-
-@table @env
-@cindex @env{GAWK_MSEC_SLEEP} environment variable
-@cindex environment variables @subentry @env{GAWK_MSEC_SLEEP}
-@item GAWK_MSEC_SLEEP
-Specifies the interval between connection retries,
-in milliseconds. On systems that do not support
-the @code{usleep()} system call,
-the value is rounded up to an integral number of seconds.
-
-@ignore
-@cindex @env{GAWK_NO_MPFR_WARN} environment variable
-@cindex environment variables @subentry @env{GAWK_NO_MPFR_WARN}
-@item GAWK_NO_MPFR_WARN
-Specifies that @command{gawk} should not print a deprecation
-warning when used with the @option{-M}/@option{--bignum} options.
-@end ignore
-
-@cindex @env{GAWK_PERSIST_FILE} environment variable
-@cindex environment variables @subentry @env{GAWK_PERSIST_FILE}
-@item GAWK_PERSIST_FILE
-Specifies the backing file to use for persistent storage
-of @command{gawk}'s variables and arrays.
-@xref{Persistent Memory}.
-
-@cindex @env{GAWK_READ_TIMEOUT} environment variable
-@cindex environment variables @subentry @env{GAWK_READ_TIMEOUT}
-@item GAWK_READ_TIMEOUT
-Specifies the time, in milliseconds, for @command{gawk} to
-wait for input before returning with an error.
-@xref{Read Timeout}.
-
-@cindex @env{GAWK_SOCK_RETRIES} environment variable
-@cindex environment variables @subentry @env{GAWK_SOCK_RETRIES}
-@item GAWK_SOCK_RETRIES
-Controls the number of times @command{gawk} attempts to
-retry a two-way TCP/IP (socket) connection before giving up.
-@xref{TCP/IP Networking}.
-Note that when nonfatal I/O is enabled (@pxref{Nonfatal}),
-@command{gawk} only tries to open a TCP/IP socket once.
-
-@cindex @env{PMA_VERBOSITY} environment variable
-@cindex environment variables @subentry @env{PMA_VERBOSITY}
-@item PMA_VERBOSITY
-Controls the verbosity of the persistent memory allocator.
-@xref{Persistent Memory}.
-
-@cindex @env{POSIXLY_CORRECT} environment variable
-@cindex environment variables @subentry @env{POSIXLY_CORRECT}
-@item POSIXLY_CORRECT
-Causes @command{gawk} to switch to POSIX-compatibility
-mode, disabling all traditional and GNU extensions.
-@xref{Options}.
-@end table
-
-The environment variables in the following list are meant
-for use by the @command{gawk} developers for testing and tuning.
-They are subject to change. The variables are:
-
-@table @env
-@cindex @env{AWKBUFSIZE} environment variable
-@cindex environment variables @subentry @env{AWKBUFSIZE}
-@item AWKBUFSIZE
-This variable only affects @command{gawk} on POSIX-compliant systems.
-With a value of @samp{exact}, @command{gawk} uses the size of each input
-file as the size of the memory buffer to allocate for I/O. Otherwise,
-the value should be a number, and @command{gawk} uses that number as
-the size of the buffer to allocate. (When this variable is not set,
-@command{gawk} uses the smaller of the file's size and the ``default''
-blocksize, which is usually the filesystem's I/O blocksize.)
-
-@cindex @env{AWK_HASH} environment variable
-@cindex environment variables @subentry @env{AWK_HASH}
-@item AWK_HASH
-If this variable exists with a value of @samp{gst}, @command{gawk}
-switches to using the hash function from GNU Smalltalk for
-managing arrays.
-With a value of @samp{fnv1a}, @command{gawk} uses the
-@uref{http://www.isthe.com/chongo/tech/comp/fnv/index.html,
-FNV1-A hash function}.
-These functions may be marginally faster than the standard function.
-
-@cindex @env{AWKREADFUNC} environment variable
-@cindex environment variables @subentry @env{AWKREADFUNC}
-@item AWKREADFUNC
-If this variable exists, @command{gawk} switches to reading source
-files one line at a time, instead of reading in blocks. This exists
-for debugging problems on filesystems on non-POSIX operating systems
-where I/O is performed in records, not in blocks.
-
-@cindex @env{GAWK_MSG_SRC} environment variable
-@cindex environment variables @subentry @env{GAWK_MSG_SRC}
-@item GAWK_MSG_SRC
-If this variable exists, @command{gawk} includes the @value{FN}
-and line number within the @command{gawk} source code
-from which warning and/or fatal messages
-are generated. Its purpose is to help isolate the source of a
-message, as there are multiple places that produce the
-same warning or error message.
-
-@cindex @env{GAWK_LOCALE_DIR} environment variable
-@cindex environment variables @subentry @env{GAWK_LOCALE_DIR}
-@item GAWK_LOCALE_DIR
-Specifies the location of compiled message object files
-for @command{gawk} itself. This is passed to the @code{bindtextdomain()}
-function when @command{gawk} starts up.
-
-@cindex @env{GAWK_NO_DFA} environment variable
-@cindex environment variables @subentry @env{GAWK_NO_DFA}
-@item GAWK_NO_DFA
-If this variable exists, @command{gawk} does not use the DFA regexp matcher
-for ``does it match'' kinds of tests. This can cause @command{gawk}
-to be slower. Its purpose is to help isolate differences between the
-two regexp matchers that @command{gawk} uses internally. (There aren't
-supposed to be differences, but occasionally theory and practice don't
-coordinate with each other.)
-
-@cindex @env{GAWK_STACKSIZE} environment variable
-@cindex environment variables @subentry @env{GAWK_STACKSIZE}
-@item GAWK_STACKSIZE
-This specifies the amount by which @command{gawk} should grow its
-internal evaluation stack, when needed.
-
-@cindex @env{INT_CHAIN_MAX} environment variable
-@cindex environment variables @subentry @env{INT_CHAIN_MAX}
-@item INT_CHAIN_MAX
-This specifies intended maximum number of items @command{gawk} will maintain
on a
-hash chain for managing arrays indexed by integers.
-
-@cindex @env{STR_CHAIN_MAX} environment variable
-@cindex environment variables @subentry @env{STR_CHAIN_MAX}
-@item STR_CHAIN_MAX
-This specifies intended maximum number of items @command{gawk} will maintain
on a
-hash chain for managing arrays indexed by strings.
-
-@cindex @env{TIDYMEM} environment variable
-@cindex environment variables @subentry @env{TIDYMEM}
-@item TIDYMEM
-If this variable exists, @command{gawk} uses the @code{mtrace()} library
-calls from the GNU C library to help track down possible memory leaks.
-This cannot be used together with the persistent memory allocator.
-@end table
-
-@node Exit Status
-@section @command{gawk}'s Exit Status
-
-@cindex exit status, of @command{gawk}
-If the @code{exit} statement is used with a value
-(@pxref{Exit Statement}), then @command{gawk} exits with
-the numeric value given to it.
-
-Otherwise, if there were no problems during execution,
-@command{gawk} exits with the value of the C constant
-@code{EXIT_SUCCESS}. This is usually zero.
-
-If an error occurs, @command{gawk} exits with the value of
-the C constant @code{EXIT_FAILURE}. This is usually one.
-
-If @command{gawk} exits because of a fatal error, the exit
-status is two. On non-POSIX systems, this value may be mapped
-to @code{EXIT_FAILURE}.
-
-@node Include Files
-@section Including Other Files into Your Program
-
-@c Panos Papadopoulos <panos1962@gmail.com> contributed the original
-@c text for this section.
-
-This @value{SECTION} describes a feature that is specific to @command{gawk}.
-
-@cindex @code{@@} (at-sign) @subentry @code{@@include} directive
-@cindex at-sign (@code{@@}) @subentry @code{@@include} directive
-@cindex file inclusion, @code{@@include} directive
-@cindex including files, @code{@@include} directive
-@cindex @code{@@include} directive @sortas{include directive}
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-The @code{@@include} keyword can be used to read external @command{awk} source
-files. This gives you the ability to split large @command{awk} source files
-into smaller, more manageable pieces, and also lets you reuse common
@command{awk}
-code from various @command{awk} scripts. In other words, you can group
-together @command{awk} functions used to carry out specific tasks
-into external files. These files can be used just like function libraries,
-using the @code{@@include} keyword in conjunction with the @env{AWKPATH}
-environment variable. Note that source files may also be included
-using the @option{-i} option.
-
-Let's see an example.
-We'll start with two (trivial) @command{awk} scripts, namely
-@file{test1} and @file{test2}. Here is the @file{test1} script:
-
-@example
-BEGIN @{
- print "This is script test1."
-@}
-@end example
-
-@noindent
-and here is @file{test2}:
-
-@example
-@@include "test1"
-BEGIN @{
- print "This is script test2."
-@}
-@end example
-
-Running @command{gawk} with @file{test2}
-produces the following result:
-
-@example
-$ @kbd{gawk -f test2}
-@print{} This is script test1.
-@print{} This is script test2.
-@end example
-
-@command{gawk} runs the @file{test2} script, which includes @file{test1}
-using the @code{@@include}
-keyword. So, to include external @command{awk} source files, you just
-use @code{@@include} followed by the name of the file to be included,
-enclosed in double quotes.
-
-@quotation NOTE
-Keep in mind that this is a language construct and the @value{FN} cannot
-be a string variable, but rather just a literal string constant in double
quotes.
-@end quotation
-
-The files to be included may be nested; e.g., given a third
-script, namely @file{test3}:
-
-@example
-@group
-@@include "test2"
-BEGIN @{
- print "This is script test3."
-@}
-@end group
-@end example
-
-@noindent
-Running @command{gawk} with the @file{test3} script produces the
-following results:
-
-@example
-$ @kbd{gawk -f test3}
-@print{} This is script test1.
-@print{} This is script test2.
-@print{} This is script test3.
-@end example
-
-The @value{FN} can, of course, be a pathname. For example:
-
-@example
-@@include "../io_funcs"
-@end example
-
-@noindent
-and:
-
-@example
-@@include "/usr/awklib/network"
-@end example
-
-@noindent
-are both valid. The @env{AWKPATH} environment variable can be of great
-value when using @code{@@include}. The same rules for the use
-of the @env{AWKPATH} variable in command-line file searches
-(@pxref{AWKPATH Variable}) apply to
-@code{@@include} also.
-
-This is very helpful in constructing @command{gawk} function libraries.
-If you have a large script with useful, general-purpose @command{awk}
-functions, you can break it down into library files and put those files
-in a special directory. You can then include those ``libraries,''
-either by using the full pathnames of the files, or by setting the
@env{AWKPATH}
-environment variable accordingly and then using @code{@@include} with
-just the file part of the full pathname. Of course,
-you can keep library files in more than one directory;
-the more complex the working
-environment is, the more directories you may need to organize the files
-to be included.
-
-Given the ability to specify multiple @option{-f} options, the
-@code{@@include} mechanism is not strictly necessary.
-However, the @code{@@include} keyword
-can help you in constructing self-contained @command{gawk} programs,
-thus reducing the need for writing complex and tedious command lines.
-In particular, @code{@@include} is very useful for writing CGI scripts
-to be run from web pages.
-
-The @code{@@include} directive and the @option{-i}/@option{--include}
-command line option are completely equivalent. An included program
-source is not loaded if it has been previously loaded.
-
-The rules for finding a source file described in @ref{AWKPATH Variable} also
-apply to files loaded with @code{@@include}.
-
-Finally, files included with @code{@@include}
-are treated as if they had @samp{@@namespace "awk"}
-at their beginning. @xref{Changing The Namespace}, for more information.
-
-@node Loading Shared Libraries
-@section Loading Dynamic Extensions into Your Program
-
-This @value{SECTION} describes a feature that is specific to @command{gawk}.
-
-@cindex @code{@@} (at-sign) @subentry @code{@@load} directive
-@cindex at-sign (@code{@@}) @subentry @code{@@load} directive
-@cindex loading extensions @subentry @code{@@load} directive
-@cindex extensions @subentry loadable @subentry loading, @code{@@load}
directive
-@cindex @code{@@load} directive @sortas{load directive}
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-The @code{@@load} keyword can be used to read external @command{awk} extensions
-(stored as system shared libraries).
-This allows you to link in compiled code that may offer superior
-performance and/or give you access to extended capabilities not supported
-by the @command{awk} language. The @env{AWKLIBPATH} variable is used to
-search for the extension. Using @code{@@load} is completely equivalent
-to using the @option{-l} command-line option.
-
-If the extension is not initially found in @env{AWKLIBPATH}, another
-search is conducted after appending the platform's default shared library
-suffix to the @value{FN}. For example, on GNU/Linux systems, the suffix
-@samp{.so} is used:
-
-@example
-$ @kbd{gawk '@@load "ordchr"; BEGIN @{print chr(65)@}'}
-@print{} A
-@end example
-
-@noindent
-This is equivalent to the following example:
-
-@example
-@group
-$ @kbd{gawk -lordchr 'BEGIN @{print chr(65)@}'}
-@print{} A
-@end group
-@end example
-
-@noindent
-For command-line usage, the @option{-l} option is more convenient,
-but @code{@@load} is useful for embedding inside an @command{awk} source file
-that requires access to an extension.
-
-@ref{Dynamic Extensions}, describes how to write extensions (in C or C++)
-that can be loaded with either @code{@@load} or the @option{-l} option.
-It also describes the @code{ordchr} extension.
-
-@node Obsolete
-@section Obsolete Options and/or Features
-
-@c update this section for each release!
-
-@cindex options @subentry deprecated
-@cindex features @subentry deprecated
-@cindex obsolete features
-This @value{SECTION} describes features and/or command-line options from
-previous releases of @command{gawk} that either are not available in the
-current version or are still supported but deprecated (meaning that
-they will @emph{not} be in a future release).
-
-@ignore
-@c This happened long enough ago that we can remove it.
-The process-related special files @file{/dev/pid}, @file{/dev/ppid},
-@file{/dev/pgrpid}, and @file{/dev/user} were deprecated in @command{gawk}
-3.1, but still worked. As of @value{PVERSION} 4.0, they are no longer
-interpreted specially by @command{gawk}. (Use @code{PROCINFO} instead;
-see @ref{Auto-set}.)
-@end ignore
-
-@ignore
-This @value{SECTION}
-is thus essentially a place holder,
-in case some option becomes obsolete in a future version of @command{gawk}.
-@end ignore
-
-@ignore
-The arbitrary precision arithmetic feature is deprecated as of
-@command{gawk} @value{PVERSION} 5.2.
-Use of @option{-M}/@option{--bignum} produces a warning message.
-The feature will be removed in the release of 2024.
-@end ignore
-
-As of
-@command{gawk} @value{PVERSION} 5.2.
-the arbitrary precision arithmetic feature is ``on parole.''
-This feature is now being
-supported by a volunteer in the development team and not by the primary
-maintainer. If this situation changes, then the feature will be removed.
-For more information see @ref{MPFR On Parole}.
-
-@node Undocumented
-@section Undocumented Options and Features
-@cindex undocumented features
-@cindex features @subentry undocumented
-@cindex Skywalker, Luke
-@cindex Kenobi, Obi-Wan
-@cindex jedi knights
-@cindex knights, jedi
-@quotation
-@i{Use the Source, Luke!}
-@author Obi-Wan
-@end quotation
-
-@cindex shells @subentry sea
-This @value{SECTION} intentionally left
-blank.
-
-@ignore
-@c If these came out in the Info file or TeX document, then they wouldn't
-@c be undocumented, would they?
-
-@command{gawk} has one undocumented option:
-
-@table @code
-@item -W nostalgia
-@itemx --nostalgia
-Print the message @samp{awk: bailing out near line 1} and dump core.
-This option was inspired by the common behavior of very early versions of
-Unix @command{awk} and by a t--shirt.
-The message is @emph{not} subject to translation in non-English locales.
-@c so there! nyah, nyah.
-@end table
-
-Early versions of @command{awk} used to not require any separator (either
-a newline or @samp{;}) between the rules in @command{awk} programs. Thus,
-it was common to see one-line programs like:
-
-@example
-awk '@{ sum += $1 @} END @{ print sum @}'
-@end example
-
-@command{gawk} actually supports this but it is purposely undocumented
-because it is bad style. The correct way to write such a program
-is either:
-
-@example
-awk '@{ sum += $1 @} ; END @{ print sum @}'
-@end example
-
-@noindent
-or:
-
-@example
-awk '@{ sum += $1 @}
- END @{ print sum @}' data
-@end example
-
-@noindent
-@xref{Statements/Lines}, for a fuller explanation.
-
-You can insert newlines after the @samp{;} in @code{for} loops.
-This seems to have been a long-undocumented feature in Unix @command{awk}.
-
-Similarly, you may use @code{print} or @code{printf} statements in the
-@var{init} and @var{increment} parts of a @code{for} loop. This is another
-long-undocumented ``feature'' of Unix @command{awk}.
-
-@command{gawk} lets you use the names of built-in functions that are
-@command{gawk} extensions as the names of parameters in user-defined functions.
-This is intended to ``future-proof'' old code that happens to use
-function names added by @command{gawk} after the code was written.
-Standard @command{awk} built-in functions, such as @code{sin()} or
-@code{substr()} are @emph{not} shadowed in this way.
-
-You can use a @samp{P} modifier for the @code{printf()} floating-point
-format control letters to use the underlying C library's result for
-NaN and Infinity values, instead of the special values @command{gawk}
-usually produces, as described in @ref{POSIX Floating Point Problems}.
-This is mainly useful for the included unit tests.
-
-The @code{typeof()} built-in function
-(@pxref{Type Functions})
-takes an optional second array argument that, if present, will be cleared
-and populated with some information about the internal implementation of
-the variable. This can be useful for debugging. At the moment, this
-returns a textual version of the flags for scalar variables, and the
-array back-end implementation type for arrays. This interface is subject
-to change and may not be stable.
-
-When not in POSIX or compatibility mode, if you set @code{LINENO} to a
-numeric value using the @option{-v} option, @command{gawk} adds that value
-to the real line number for use in error messages. This is intended for
-use within Bash shell scripts, such that the error message will reflect
-the line number in the shell script, instead of in the @command{awk}
-program. To demonstrate:
-
-@example
-$ @kbd{gawk -v LINENO=10 'BEGIN @{ print("hi" @}'}
-@error{} gawk: cmd. line:11: BEGIN @{ print("hi" @}
-@error{} gawk: cmd. line:11: ^ syntax error
-@end example
-
-@end ignore
-
-@node Invoking Summary
-@section Summary
-
-@itemize @value{BULLET}
-
-@c From Neil R. Ormos
-@item
-@command{gawk} parses arguments on the command line, left to right, to
-determine if they should be treated as options or as non-option arguments.
-
-@item
-@command{gawk} recognizes several options which control its operation,
-as described in @ref{Options}. All options begin with @samp{-}.
-
-@item
-Any argument that is not recognized as an option is treated as a
-non-option argument, even if it begins with @samp{-}.
-
-@itemize @value{MINUS}
-@item
-However, when an option itself requires an argument, and the option is
separated
-from that argument on the command line by at least one space, the space
-is ignored, and the argument is considered to be related to the option. Thus,
in
-the invocation, @samp{gawk -F x}, the @samp{x} is treated as belonging to the
-@option{-F} option, not as a separate non-option argument.
-@end itemize
-
-@item
-Once @command{gawk} finds a non-option argument, it stops looking for
-options. Therefore, all following arguments are also non-option arguments,
-even if they resemble recognized options.
-
-@item
-If no @option{-e} or @option{-f} options are present, @command{gawk}
-expects the program text to be in the first non-option argument.
-
-@item
-All non-option arguments, except program text provided in the first
-non-option argument, are placed in @code{ARGV} as explained in
-@ref{ARGC and ARGV}, and are processed as described in @ref{Other Arguments}.
-@c And I wrote:
-Adjusting @code{ARGC} and @code{ARGV}
-affects how @command{awk} processes input.
-
-@c ----------------------------------------
-
-@item
-The three standard options for all versions of @command{awk} are
-@option{-f}, @option{-F}, and @option{-v}. @command{gawk} supplies these
-and many others, as well as corresponding GNU-style long options.
-
-@item
-Nonoption command-line arguments are usually treated as @value{FN}s,
-unless they have the form @samp{@var{var}=@var{value}}, in which case
-they are taken as variable assignments to be performed at that point
-in processing the input.
-
-@item
-You can use a single minus sign (@samp{-}) to refer to standard input
-on the command line. @command{gawk} also lets you use the special
-@value{FN} @file{/dev/stdin}.
-
-@item
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-@cindex @env{POSIXLY_CORRECT} environment variable
-@cindex environment variables @subentry @env{POSIXLY_CORRECT}
-@command{gawk} pays attention to a number of environment variables.
-@env{AWKPATH}, @env{AWKLIBPATH}, and @env{POSIXLY_CORRECT} are the
-most important ones.
-
-@item
-@command{gawk}'s exit status conveys information to the program
-that invoked it. Use the @code{exit} statement from within
-an @command{awk} program to set the exit status.
-
-@item
-@command{gawk} allows you to include other @command{awk} source files into
-your program using the @code{@@include} statement and/or the @option{-i}
-and @option{-f} command-line options.
-
-@item
-@command{gawk} allows you to load additional functions written in C
-or C++ using the @code{@@load} statement and/or the @option{-l} option.
-(This advanced feature is described later, in @ref{Dynamic Extensions}.)
-@end itemize
-
-@node Regexp
-@chapter Regular Expressions
-@cindex regexp
-@cindex regular expressions
-
-A @dfn{regular expression}, or @dfn{regexp}, is a way of describing a
-set of strings.
-Because regular expressions are such a fundamental part of @command{awk}
-programming, their format and use deserve a separate @value{CHAPTER}.
-
-@cindex forward slash (@code{/}) @subentry to enclose regular expressions
-@cindex @code{/} (forward slash) @subentry to enclose regular expressions
-A regular expression enclosed in slashes (@samp{/})
-is an @command{awk} pattern that matches every input record whose text
-belongs to that set.
-The simplest regular expression is a sequence of letters, numbers, or
-both. Such a regexp matches any string that contains that sequence.
-Thus, the regexp @samp{foo} matches any string containing @samp{foo}.
-Thus, the pattern @code{/foo/} matches any input record containing
-the three adjacent characters @samp{foo} @emph{anywhere} in the record. Other
-kinds of regexps let you specify more complicated classes of strings.
-
-@ifnotinfo
-Initially, the examples in this @value{CHAPTER} are simple.
-As we explain more about how
-regular expressions work, we present more complicated instances.
-@end ifnotinfo
-
-@menu
-* Regexp Usage:: How to Use Regular Expressions.
-* Escape Sequences:: How to write nonprinting characters.
-* Regexp Operators:: Regular Expression Operators.
-* Bracket Expressions:: What can go between @samp{[...]}.
-* Leftmost Longest:: How much text matches.
-* Computed Regexps:: Using Dynamic Regexps.
-* GNU Regexp Operators:: Operators specific to GNU software.
-* Case-sensitivity:: How to do case-insensitive matching.
-* Regexp Summary:: Regular expressions summary.
-@end menu
-
-@node Regexp Usage
-@section How to Use Regular Expressions
-
-@cindex patterns @subentry regexp constants as
-@cindex regular expressions @subentry as patterns
-A regular expression can be used as a pattern by enclosing it in
-slashes. Then the regular expression is tested against the
-entire text of each record. (Normally, it only needs
-to match some part of the text in order to succeed.) For example, the
-following prints the second field of each record where the string
-@samp{li} appears anywhere in the record:
-
-@example
-$ @kbd{awk '/li/ @{ print $2 @}' mail-list}
-@print{} 555-5553
-@print{} 555-0542
-@print{} 555-6699
-@print{} 555-3430
-@end example
-
-@cindex regular expressions @subentry operators
-@cindex operators @subentry string-matching
-@c @cindex operators, @code{~}
-@cindex string-matching operators
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-@c @cindex operators, @code{!~}
-@cindex @code{if} statement @subentry use of regexps in
-@cindex @code{while} statement @subentry use of regexps in
-@cindex @code{do}-@code{while} statement @subentry use of regexps in
-@c @cindex statements, @code{if}
-@c @cindex statements, @code{while}
-@c @cindex statements, @code{do}
-Regular expressions can also be used in matching expressions. These
-expressions allow you to specify the string to match against; it need
-not be the entire current input record. The two operators @samp{~}
-and @samp{!~} perform regular expression comparisons. Expressions
-using these operators can be used as patterns, or in @code{if},
-@code{while}, @code{for}, and @code{do} statements.
-(@xref{Statements}.)
-For example, the following is true if the expression @var{exp} (taken
-as a string) matches @var{regexp}:
-
-@example
-@var{exp} ~ /@var{regexp}/
-@end example
-
-@noindent
-This example matches, or selects, all input records with the uppercase
-letter @samp{J} somewhere in the first field:
-
-@example
-$ @kbd{awk '$1 ~ /J/' inventory-shipped}
-@print{} Jan 13 25 15 115
-@print{} Jun 31 42 75 492
-@print{} Jul 24 34 67 436
-@print{} Jan 21 36 64 620
-@end example
-
-So does this:
-
-@example
-awk '@{ if ($1 ~ /J/) print @}' inventory-shipped
-@end example
-
-This next example is true if the expression @var{exp}
-(taken as a character string)
-does @emph{not} match @var{regexp}:
-
-@example
-@var{exp} !~ /@var{regexp}/
-@end example
-
-The following example matches,
-or selects, all input records whose first field @emph{does not} contain
-the uppercase letter @samp{J}:
-
-@example
-$ @kbd{awk '$1 !~ /J/' inventory-shipped}
-@print{} Feb 15 32 24 226
-@print{} Mar 15 24 34 228
-@print{} Apr 31 52 63 420
-@print{} May 16 34 29 208
-@dots{}
-@end example
-
-@cindex regexp constants
-@cindex constants @subentry regexp
-@cindex regular expressions, constants @seeentry{regexp constants}
-When a regexp is enclosed in slashes, such as @code{/foo/}, we call it
-a @dfn{regexp constant}, much like @code{5.27} is a numeric constant and
-@code{"foo"} is a string constant.
-
-@node Escape Sequences
-@section Escape Sequences
-
-@cindex escape sequences
-@cindex escape sequences @seealso{backslash}
-@cindex backslash (@code{\}) @subentry in escape sequences
-@cindex @code{\} (backslash) @subentry in escape sequences
-Some characters cannot be included literally in string constants
-(@code{"foo"}) or regexp constants (@code{/foo/}).
-Instead, they should be represented with @dfn{escape sequences},
-which are character sequences beginning with a backslash (@samp{\}).
-One use of an escape sequence is to include a double-quote character in
-a string constant. Because a plain double quote ends the string, you
-must use @samp{\"} to represent an actual double-quote character as a
-part of the string. For example:
-
-@example
-$ @kbd{awk 'BEGIN @{ print "He said \"hi!\" to her." @}'}
-@print{} He said "hi!" to her.
-@end example
-
-The backslash character itself is another character that cannot be
-included normally; you must write @samp{\\} to put one backslash in the
-string or regexp. Thus, the string whose contents are the two characters
-@samp{"} and @samp{\} must be written @code{"\"\\"}.
-
-Other escape sequences represent unprintable characters
-such as TAB or newline. There is nothing to stop you from entering most
-unprintable characters directly in a string constant or regexp constant,
-but they may look ugly.
-
-The following list presents
-all the escape sequences used in @command{awk} and
-what they represent. Unless noted otherwise, all these escape
-sequences apply to both string constants and regexp constants:
-
-@cindex ASCII
-@table @code
-@item \\
-A literal backslash, @samp{\}.
-
-@c @cindex @command{awk} language, V.4 version
-@cindex @code{\} (backslash) @subentry @code{\a} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\a} escape sequence
-@item \a
-The ``alert'' character, @kbd{Ctrl-g}, ASCII code 7 (BEL).
-(This often makes some sort of audible noise.)
-
-@cindex @code{\} (backslash) @subentry @code{\b} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\b} escape sequence
-@item \b
-Backspace, @kbd{Ctrl-h}, ASCII code 8 (BS).
-
-@cindex @code{\} (backslash) @subentry @code{\f} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\f} escape sequence
-@item \f
-Formfeed, @kbd{Ctrl-l}, ASCII code 12 (FF).
-
-@cindex @code{\} (backslash) @subentry @code{\n} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\n} escape sequence
-@item \n
-Newline, @kbd{Ctrl-j}, ASCII code 10 (LF).
-
-@cindex @code{\} (backslash) @subentry @code{\r} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\r} escape sequence
-@item \r
-Carriage return, @kbd{Ctrl-m}, ASCII code 13 (CR).
-
-@cindex @code{\} (backslash) @subentry @code{\t} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\t} escape sequence
-@item \t
-Horizontal TAB, @kbd{Ctrl-i}, ASCII code 9 (HT).
-
-@c @cindex @command{awk} language, V.4 version
-@cindex @code{\} (backslash) @subentry @code{\v} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\v} escape sequence
-@item \v
-Vertical TAB, @kbd{Ctrl-k}, ASCII code 11 (VT).
-
-@cindex @code{\} (backslash) @subentry @code{\}@var{nnn} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\}@var{nnn} escape sequence
-@item \@var{nnn}
-The octal value @var{nnn}, where @var{nnn} stands for 1 to 3 digits
-between @samp{0} and @samp{7}. For example, the code for the ASCII ESC
-(escape) character is @samp{\033}.
-
-@c @cindex @command{awk} language, V.4 version
-@c @cindex @command{awk} language, POSIX version
-@cindex @code{\} (backslash) @subentry @code{\x} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\x} escape sequence
-@cindex common extensions @subentry @code{\x} escape sequence
-@cindex extensions @subentry common @subentry @code{\x} escape sequence
-@item \x@var{hh}@dots{}
-The hexadecimal value @var{hh}, where @var{hh} stands for a sequence
-of hexadecimal digits (@samp{0}--@samp{9}, and either @samp{A}--@samp{F}
-or @samp{a}--@samp{f}). A maximum of two digits are allowed after
-the @samp{\x}. Any further hexadecimal digits are treated as simple
-letters or numbers. @value{COMMONEXT}
-(The @samp{\x} escape sequence is not allowed in POSIX awk.)
-
-@quotation CAUTION
-In ISO C, the escape sequence continues until the first nonhexadecimal
-digit is seen.
-For many years, @command{gawk} would continue incorporating
-hexadecimal digits into the value until a non-hexadecimal digit
-or the end of the string was encountered.
-However, using more than two hexadecimal digits produced
-undefined results.
-As of @value{PVERSION} 4.2, only two digits
-are processed.
-@end quotation
-
-@cindex @code{\} (backslash) @subentry @code{\u} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\u} escape sequence
-@cindex common extensions @subentry @code{\u} escape sequence
-@cindex extensions @subentry common @subentry @code{\u} escape sequence
-@item \u@var{hh}@dots{}
-The hexadecimal value @var{hh}, where @var{hh} stands for a sequence
-of one or more hexadecimal digits (@samp{0}--@samp{9}, and either
-@samp{A}--@samp{F} or @samp{a}--@samp{f}). A maximum of eight digits
-are allowed after the @samp{\u}. Any further hexadecimal digits are
-treated as simple letters or numbers. @value{COMMONEXT} (The @samp{\u}
-escape sequence is not allowed in POSIX awk.)
-
-This escape sequence is intended for designating a character in
-the current locale's character set.@footnote{Typically, this is a
-Unicode-based locale, but it doesn't have to be.} @command{gawk} first
-converts the given digits into an integer and then translates the given
-``wide character'' value into the current locale's multibyte encoding. If
-the wide character value does not represent a valid character, or if
-the character is valid but cannot be encoded into the current locale's
-multibyte encoding, the value becomes @code{"?"}. @command{gawk} issues
-a warning message when this happens.
-
-@cindex @code{\} (backslash) @subentry @code{\/} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\/} escape sequence
-@item \/
-A literal slash (should be used for regexp constants only).
-This sequence is used when you want to write a regexp
-constant that contains a slash
-(such as @code{/.*:\/home\/[[:alnum:]]+:.*/}; the @samp{[[:alnum:]]}
-notation is discussed in @ref{Bracket Expressions}).
-Because the regexp is delimited by
-slashes, you need to escape any slash that is part of the pattern,
-in order to tell @command{awk} to keep processing the rest of the regexp.
-
-@cindex @code{\} (backslash) @subentry @code{\"} escape sequence
-@cindex backslash (@code{\}) @subentry @code{\"} escape sequence
-@item \"
-A literal double quote (should be used for string constants only).
-This sequence is used when you want to write a string
-constant that contains a double quote
-(such as @code{"He said \"hi!\" to her."}).
-Because the string is delimited by
-double quotes, you need to escape any quote that is part of the string,
-in order to tell @command{awk} to keep processing the rest of the string.
-@end table
-
-In @command{gawk}, a number of additional two-character sequences that begin
-with a backslash have special meaning in regexps.
-@xref{GNU Regexp Operators}.
-
-In a regexp, a backslash before any character that is not in the previous list
-and not listed in
-@ref{GNU Regexp Operators}
-means that the next character should be taken literally, even if it would
-normally be a regexp operator. For example, @code{/a\+b/} matches the three
-characters @samp{a+b}.
-
-@cindex backslash (@code{\}) @subentry in escape sequences
-@cindex @code{\} (backslash) @subentry in escape sequences
-@cindex portability
-For complete portability, do not use a backslash before any character not
-shown in the previous list or that is not an operator.
-
-@c 11/2014: Moved so as to not stack sidebars
-@sidebar Backslash Before Regular Characters
-@cindex portability @subentry backslash in escape sequences
-@cindex POSIX @command{awk} @subentry backslashes in string constants
-@cindex backslash (@code{\}) @subentry in escape sequences @subentry POSIX and
-@cindex @code{\} (backslash) @subentry in escape sequences @subentry POSIX and
-
-@cindex troubleshooting @subentry backslash before nonspecial character
-If you place a backslash in a string constant before something that is
-not one of the characters previously listed, POSIX @command{awk} purposely
-leaves what happens as undefined. There are two choices:
-
-@c @cindex automatic warnings
-@c @cindex warnings, automatic
-@cindex Brian Kernighan's @command{awk}
-@table @asis
-@item Strip the backslash out
-This is what BWK @command{awk} and @command{gawk} both do.
-For example, @code{"a\qc"} is the same as @code{"aqc"}.
-(Because this is such an easy bug both to introduce and to miss,
-@command{gawk} warns you about it.)
-Consider @samp{FS = @w{"[ \t]+\|[ \t]+"}} to use vertical bars
-surrounded by whitespace as the field separator. There should be
-two backslashes in the string: @samp{FS = @w{"[ \t]+\\|[ \t]+"}}.)
-@c I did this! This is why I added the warning.
-
-@cindex @command{gawk} @subentry escape sequences
-@cindex @command{gawk} @subentry escape sequences @seealso{backslash}
-@cindex Unix @command{awk} @subentry backslashes in escape sequences
-@cindex @command{mawk} utility
-@item Leave the backslash alone
-Some other @command{awk} implementations do this.
-In such implementations, typing @code{"a\qc"} is the same as typing
-@code{"a\\qc"}.
-@end table
-@end sidebar
-
-To summarize:
-
-@itemize @value{BULLET}
-@item
-The escape sequences in the preceding list are always processed first,
-for both string constants and regexp constants. This happens very early,
-as soon as @command{awk} reads your program.
-
-@item
-@command{gawk} processes both regexp constants and dynamic regexps
-(@pxref{Computed Regexps}),
-for the special operators listed in
-@ref{GNU Regexp Operators}.
-
-@item
-A backslash before any other character means to treat that character
-literally.
-@end itemize
-
-@sidebar Escape Sequences for Metacharacters
-@cindex metacharacters @subentry escape sequences for
-
-Suppose you use an octal or hexadecimal
-escape to represent a regexp metacharacter.
-(See @ref{Regexp Operators}.)
-Does @command{awk} treat the character as a literal character or as a regexp
-operator?
-
-@cindex dark corner @subentry escape sequences @subentry for metacharacters
-Historically, such characters were taken literally.
-@value{DARKCORNER}
-However, the POSIX standard indicates that they should be treated
-as real metacharacters, which is what @command{gawk} does.
-In compatibility mode (@pxref{Options}),
-@command{gawk} treats the characters represented by octal and hexadecimal
-escape sequences literally when used in regexp constants. Thus,
-@code{/a\52b/} is equivalent to @code{/a\*b/}.
-@end sidebar
-
-@node Regexp Operators
-@section Regular Expression Operators
-@cindex regular expressions @subentry operators
-@cindex metacharacters @subentry in regular expressions
-
-You can combine regular expressions with special characters,
-called @dfn{regular expression operators} or @dfn{metacharacters}, to
-increase the power and versatility of regular expressions.
-
-@menu
-* Regexp Operator Details:: The actual details.
-* Interval Expressions:: Notes on interval expressions.
-@end menu
-
-@node Regexp Operator Details
-@subsection Regexp Operators in @command{awk}
-
-The escape sequences described
-@ifnotinfo
-earlier
-@end ifnotinfo
-in @ref{Escape Sequences}
-are valid inside a regexp. They are introduced by a @samp{\} and
-are recognized and converted into corresponding real characters as
-the very first step in processing regexps.
-
-Here is a list of metacharacters. All characters that are not escape
-sequences and that are not listed here stand for themselves:
-
-@c Use @asis so the docbook comes out ok. Sigh.
-@table @asis
-@cindex backslash (@code{\}) @subentry regexp operator
-@cindex @code{\} (backslash) @subentry regexp operator
-@item @code{\}
-This suppresses the special meaning of a character when
-matching. For example, @samp{\$}
-matches the character @samp{$}.
-
-@cindex regular expressions @subentry anchors in
-@cindex Texinfo @subentry chapter beginnings in files
-@cindex @code{^} (caret) @subentry regexp operator
-@cindex caret (@code{^}) @subentry regexp operator
-@item @code{^}
-This matches the beginning of a string. @samp{^@@chapter}
-matches @samp{@@chapter} at the beginning of a string,
-for example, and can be used
-to identify chapter beginnings in Texinfo source files.
-The @samp{^} is known as an @dfn{anchor}, because it anchors the pattern to
-match only at the beginning of the string.
-
-It is important to realize that @samp{^} does not match the beginning of
-a line (the point right after a @samp{\n} newline character) embedded in a
string.
-The condition is not true in the following example:
-
-@example
-if ("line1\nLINE 2" ~ /^L/) @dots{}
-@end example
-
-@cindex @code{$} (dollar sign) @subentry regexp operator
-@cindex dollar sign (@code{$}) @subentry regexp operator
-@item @code{$}
-This is similar to @samp{^}, but it matches only at the end of a string.
-For example, @samp{p$}
-matches a record that ends with a @samp{p}. The @samp{$} is an anchor
-and does not match the end of a line
-(the point right before a @samp{\n} newline character)
-embedded in a string.
-The condition in the following example is not true:
-
-@example
-if ("line1\nLINE 2" ~ /1$/) @dots{}
-@end example
-
-@cindex @code{.} (period), regexp operator
-@cindex period (@code{.}), regexp operator
-@item @code{.} (period)
-This matches any single character,
-@emph{including} the newline character. For example, @samp{.P}
-matches any single character followed by a @samp{P} in a string. Using
-concatenation, we can make a regular expression such as @samp{U.A}, which
-matches any three-character sequence that begins with @samp{U} and ends
-with @samp{A}.
-
-@cindex POSIX mode
-@cindex POSIX @command{awk} @subentry period (@code{.}), using
-In strict POSIX mode (@pxref{Options}),
-@samp{.} does not match the @sc{nul}
-character, which is a character with all bits equal to zero.
-Otherwise, @sc{nul} is just another character. Other versions of @command{awk}
-may not be able to match the @sc{nul} character.
-
-@cindex @code{[]} (square brackets), regexp operator
-@cindex square brackets (@code{[]}), regexp operator
-@cindex bracket expressions
-@cindex character sets (in regular expressions) @seeentry{bracket expressions}
-@cindex character lists @seeentry{bracket expressions}
-@cindex character classes @seeentry{bracket expressions}
-@item @code{[}@dots{}@code{]}
-This is called a @dfn{bracket expression}.@footnote{In other literature,
-you may see a bracket expression referred to as either a
-@dfn{character set}, a @dfn{character class}, or a @dfn{character list}.}
-It matches any @emph{one} of the characters that are enclosed in
-the square brackets. For example, @samp{[MVX]} matches any one of
-the characters @samp{M}, @samp{V}, or @samp{X} in a string. A full
-discussion of what can be inside the square brackets of a bracket expression
-is given in
-@ref{Bracket Expressions}.
-
-@cindex bracket expressions @subentry complemented
-@item @code{[^}@dots{}@code{]}
-This is a @dfn{complemented bracket expression}. The first character after
-the @samp{[} @emph{must} be a @samp{^}. It matches any characters
-@emph{except} those in the square brackets. For example, @samp{[^awk]}
-matches any character that is not an @samp{a}, @samp{w},
-or @samp{k}.
-
-@cindex @code{|} (vertical bar)
-@cindex vertical bar (@code{|})
-@item @code{|}
-This is the @dfn{alternation operator} and it is used to specify
-alternatives. The @samp{|} has the lowest precedence of all the regular
-expression operators. For example, @samp{^P|[aeiouy]} matches any string
-that matches either @samp{^P} or @samp{[aeiouy]}. This means it matches
-any string that starts with @samp{P} or contains (anywhere within it)
-a lowercase English vowel.
-
-The alternation applies to the largest possible regexps on either side.
-
-@cindex @code{()} (parentheses) @subentry regexp operator
-@cindex parentheses @code{()} @subentry regexp operator
-@item @code{(}@dots{}@code{)}
-Parentheses are used for grouping in regular expressions, as in
-arithmetic. They can be used to concatenate regular expressions
-containing the alternation operator, @samp{|}. For example,
-@samp{@@(samp|code)\@{[^@}]+\@}} matches both @samp{@@code@{foo@}} and
-@samp{@@samp@{bar@}}.
-(These are Texinfo formatting control sequences. The @samp{+} is
-explained further on in this list.)
-
-The left or opening parenthesis is always a metacharacter; to match
-one literally, precede it with a backslash. However, the right or
-closing parenthesis is only special when paired with a left parenthesis;
-an unpaired right parenthesis is (silently) treated as a regular character.
-
-@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry as regexp
operator
-@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry as regexp
operator
-@item @code{*}
-This symbol means that the preceding regular expression should be
-repeated as many times as necessary to find a match. For example, @samp{ph*}
-applies the @samp{*} symbol to the preceding @samp{h} and looks for matches
-of one @samp{p} followed by any number of @samp{h}s. This also matches
-just @samp{p} if no @samp{h}s are present.
-
-There are two subtle points to understand about how @samp{*} works.
-First, the @samp{*} applies only to the single preceding regular expression
-component (e.g., in @samp{ph*}, it applies just to the @samp{h}).
-To cause @samp{*} to apply to a larger subexpression, use parentheses:
-@samp{(ph)*} matches @samp{ph}, @samp{phph}, @samp{phphph}, and so on.
-
-Second, @samp{*} finds as many repetitions as possible. If the text
-to be matched is @samp{phhhhhhhhhhhhhhooey}, @samp{ph*} matches all of
-the @samp{h}s.
-
-@cindex @code{+} (plus sign) @subentry regexp operator
-@cindex plus sign (@code{+}) @subentry regexp operator
-@item @code{+}
-This symbol is similar to @samp{*}, except that the preceding expression must
be
-matched at least once. This means that @samp{wh+y}
-would match @samp{why} and @samp{whhy}, but not @samp{wy}, whereas
-@samp{wh*y} would match all three.
-
-@cindex @code{?} (question mark) @subentry regexp operator
-@cindex question mark (@code{?}) @subentry regexp operator
-@item @code{?}
-This symbol is similar to @samp{*}, except that the preceding expression can be
-matched either once or not at all. For example, @samp{fe?d}
-matches @samp{fed} and @samp{fd}, but nothing else.
-
-@cindex @code{@{@}} (braces) @subentry regexp operator
-@cindex braces (@code{@{@}}) @subentry regexp operator
-@cindex interval expressions, regexp operator
-@item @code{@{}@var{n}@code{@}}
-@itemx @code{@{}@var{n}@code{,@}}
-@itemx @code{@{}@var{n}@code{,}@var{m}@code{@}}
-One or two numbers inside braces denote an @dfn{interval expression}.
-If there is one number in the braces, the preceding regexp is repeated
-@var{n} times.
-If there are two numbers separated by a comma, the preceding regexp is
-repeated @var{n} to @var{m} times.
-If there is one number followed by a comma, then the preceding regexp
-is repeated at least @var{n} times:
-
-@table @code
-@item wh@{3@}y
-Matches @samp{whhhy}, but not @samp{why} or @samp{whhhhy}.
-
-@item wh@{3,5@}y
-Matches @samp{whhhy}, @samp{whhhhy}, or @samp{whhhhhy} only.
-
-@item wh@{2,@}y
-Matches @samp{whhy}, @samp{whhhy}, and so on.
-@end table
-@end table
-
-@cindex precedence @subentry regexp operators
-@cindex regular expressions @subentry operators @subentry precedence of
-In regular expressions, the @samp{*}, @samp{+}, and @samp{?} operators,
-as well as the braces @samp{@{} and @samp{@}},
-have
-the highest precedence, followed by concatenation, and finally by @samp{|}.
-As in arithmetic, parentheses can change how operators are grouped.
-
-@cindex POSIX @command{awk} @subentry regular expressions and
-@cindex @command{gawk} @subentry regular expressions @subentry precedence
-According to the POSIX specification, when @samp{*}, @samp{+}, @samp{?},
-or @samp{@{} are not preceded by a character, the behavior is
-``undefined.''
-In practice, for @command{gawk}, the @samp{*}, @samp{+}, @samp{?} and
-@samp{@{} operators stand for themselves when there is nothing in the
-regexp that precedes them. For example, @code{/+/} matches a literal
-plus sign. However, many other versions of @command{awk} treat such a
-usage as a syntax error.
-
-@sidebar What About The Empty Regexp?
-@cindex empty regexps
-@cindex regexps, empty
-We describe here an advanced regexp usage. Feel free to skip it
-upon first reading.
-
-You can supply an empty regexp constant (@samp{//}) in all places
-where a regexp is expected. Is this useful? What does it match?
-
-It is useful. It matches the (invisible) empty string at the start
-and end of a string of characters, as well as the empty string
-between characters. This is best illustrated with the @code{gsub()}
-function, which makes global substitutions in a string
-(@pxref{String Functions}). Normal usage of @code{gsub()} is like
-so:
-
-@example
-$ @kbd{awk '}
-> @kbd{BEGIN @{}
-> @kbd{ x = "ABC_CBA"}
-> @kbd{ gsub(/B/, "bb", x)}
-> @kbd{ print x}
-> @kbd{@}'}
-@print{} AbbC_CbbA
-@end example
-
-We can use @code{gsub()} to see where the empty strings
-are that match the empty regexp:
-
-@example
-$ @kbd{awk '}
-> @kbd{BEGIN @{}
-> @kbd{ x = "ABC"}
-> @kbd{ gsub(//, "x", x)}
-> @kbd{ print x}
-> @kbd{@}'}
-@print{} xAxBxCx
-@end example
-@end sidebar
-
-@node Interval Expressions
-@subsection Some Notes On Interval Expressions
-
-@cindex POSIX @command{awk} @subentry interval expressions in
-Interval expressions were not traditionally available in @command{awk}.
-They were added as part of the POSIX standard to make @command{awk}
-and @command{egrep} consistent with each other.
-
-@cindex @command{gawk} @subentry interval expressions and
-Initially, because old programs may use @samp{@{} and @samp{@}} in regexp
-constants,
-@command{gawk} did @emph{not} match interval expressions
-in regexps.
-
-However, beginning with @value{PVERSION} 4.0,
-@command{gawk} does match interval expressions by default.
-This is because compatibility with POSIX has become more
-important to most @command{gawk} users than compatibility with
-old programs.
-
-For programs that use @samp{@{} and @samp{@}} in regexp constants,
-it is good practice to always escape them with a backslash. Then the
-regexp constants are valid and work the way you want them to, using
-any version of @command{awk}.@footnote{Use two backslashes if you're
-using a string constant with a regexp operator or function.}
-
-When @samp{@{} and @samp{@}} appear in regexp constants
-in a way that cannot be interpreted as an interval expression
-(such as @code{/q@{a@}/}), then they stand for themselves.
-
-@cindex BWK @command{awk} @subentry interval expressions in
-As mentioned, interval expressions were not traditionally available
-in @command{awk}. In March of 2019, BWK @command{awk} (finally) acquired them.
-Starting with @value{PVERSION} 5.2, @command{gawk}'s
-@option{--traditional} option no longer disables interval
-expressions in regular expressions.
-
-POSIX says that interval expressions containing repetition counts greater
-than 255 produce unspecified results.
-
-@cindex Eggert, Paul
-In the manual for GNU @command{grep}, Paul Eggert notes the following:
-
-@quotation
-Interval expressions may be implemented internally via repetition.
-For example, @samp{^(a|bc)@{2,4@}$} might be implemented as
-@samp{^(a|bc)(a|bc)((a|bc)(a|bc)?)?$}. A large repetition count may
-exhaust memory or greatly slow matching. Even small counts can cause
-problems if cascaded; for example, @samp{grep -E
-".*@{10,@}@{10,@}@{10,@}@{10,@}@{10,@}"} is likely to overflow a
-stack. Fortunately, regular expressions like these are typically
-artificial, and cascaded repetitions do not conform to POSIX so cannot
-be used in portable programs anyway.
-@end quotation
-
-@noindent
-This same caveat applies to @command{gawk}.
-
-@node Bracket Expressions
-@section Using Bracket Expressions
-@cindex bracket expressions
-@cindex bracket expressions @subentry range expressions
-@cindex range expressions (regexps)
-@cindex bracket expressions @subentry character lists
-
-As mentioned earlier, a bracket expression matches any character among
-those listed between the opening and closing square brackets.
-
-Within a bracket expression, a @dfn{range expression} consists of two
-characters separated by a hyphen. It matches any single character that
-sorts between the two characters, based upon the system's native character
-set. For example, @samp{[0-9]} is equivalent to @samp{[0123456789]}.
-(See @ref{Ranges and Locales} for an explanation of how the POSIX
-standard and @command{gawk} have changed over time. This is mainly
-of historical interest.)
-
-With the increasing popularity of the
-@uref{http://www.unicode.org, Unicode character standard},
-there is an additional wrinkle to consider. Octal and hexadecimal
-escape sequences inside bracket expressions are taken to represent
-only single-byte characters (characters whose values fit within
-the range 0--256). To match a range of characters where the endpoints
-of the range are larger than 256, enter the multibyte encodings of
-the characters directly.
-
-@cindex @code{\} (backslash) @subentry in bracket expressions
-@cindex backslash (@code{\}) @subentry in bracket expressions
-@cindex @code{^} (caret) @subentry in bracket expressions
-@cindex caret (@code{^}) @subentry in bracket expressions
-@cindex @code{-} (hyphen) @subentry in bracket expressions
-@cindex hyphen (@code{-}) @subentry in bracket expressions
-To include one of the characters @samp{\}, @samp{]}, @samp{-}, or @samp{^} in a
-bracket expression, put a @samp{\} in front of it. For example:
-
-@example
-[d\]]
-@end example
-
-@noindent
-matches either @samp{d} or @samp{]}.
-Additionally, if you place @samp{]} right after the opening
-@samp{[}, the closing bracket is treated as one of the
-characters to be matched.
-
-@cindex POSIX @command{awk} @subentry bracket expressions and
-@cindex Extended Regular Expressions (EREs)
-@cindex EREs (Extended Regular Expressions)
-@cindex @command{egrep} utility
-The treatment of @samp{\} in bracket expressions
-is compatible with other @command{awk}
-implementations and is also mandated by POSIX.
-The regular expressions in @command{awk} are a superset
-of the POSIX specification for Extended Regular Expressions (EREs).
-POSIX EREs are based on the regular expressions accepted by the
-traditional @command{egrep} utility.
-
-@cindex bracket expressions @subentry character classes
-@cindex POSIX @command{awk} @subentry bracket expressions and @subentry
character classes
-@dfn{Character classes} are a feature introduced in the POSIX standard.
-A character class is a special notation for describing
-lists of characters that have a specific attribute, but the
-actual characters can vary from country to country and/or
-from character set to character set. For example, the notion of what
-is an alphabetic character differs between the United States and France.
-
-A character class is only valid in a regexp @emph{inside} the
-brackets of a bracket expression. Character classes consist of @samp{[:},
-a keyword denoting the class, and @samp{:]}.
-@ref{table-char-classes} lists the character classes defined by the
-POSIX standard.
-
-@float Table,table-char-classes
-@caption{POSIX character classes}
-@multitable @columnfractions .15 .85
-@headitem Class @tab Meaning
-@item @code{[:alnum:]} @tab Alphanumeric characters
-@item @code{[:alpha:]} @tab Alphabetic characters
-@item @code{[:blank:]} @tab Space and TAB characters
-@item @code{[:cntrl:]} @tab Control characters
-@item @code{[:digit:]} @tab Numeric characters
-@item @code{[:graph:]} @tab Characters that are both printable and visible
-(a space is printable but not visible, whereas an @samp{a} is both)
-@item @code{[:lower:]} @tab Lowercase alphabetic characters
-@item @code{[:print:]} @tab Printable characters (characters that are not
control characters)
-@item @code{[:punct:]} @tab Punctuation characters (characters that are not
letters, digits,
-control characters, or space characters)
-@item @code{[:space:]} @tab Space characters (these are: space, TAB, newline,
carriage return, formfeed and vertical tab)
-@item @code{[:upper:]} @tab Uppercase alphabetic characters
-@item @code{[:xdigit:]} @tab Characters that are hexadecimal digits
-@end multitable
-@end float
-
-For example, before the POSIX standard, you had to write @code{/[A-Za-z0-9]/}
-to match alphanumeric characters. If your
-character set had other alphabetic characters in it, this would not
-match them.
-With the POSIX character classes, you can write
-@code{/[[:alnum:]]/} to match the alphabetic
-and numeric characters in your character set.
-
-@ignore
-From eliz@gnu.org Fri Feb 15 03:38:41 2019
-Date: Fri, 15 Feb 2019 12:38:23 +0200
-From: Eli Zaretskii <eliz@gnu.org>
-To: arnold@skeeve.com
-CC: pengyu.ut@gmail.com, bug-gawk@gnu.org
-Subject: Re: [bug-gawk] Does gawk character classes follow this?
-
-> From: arnold@skeeve.com
-> Date: Fri, 15 Feb 2019 03:01:34 -0700
-> Cc: pengyu.ut@gmail.com, bug-gawk@gnu.org
->
-> I get the feeling that there's something really bothering you, but
-> I don't understand what.
->
-> Can you clarify, please?
-
-I thought I already did: we cannot be expected to provide a definitive
-description of what the named classes stand for, because the answer
-depends on various factors out of our control.
-@end ignore
-
-@c Thanks to
-@c Date: Tue, 01 Jul 2014 07:39:51 +0200
-@c From: Hermann Peifer <peifer@gmx.eu>
-@cindex ASCII
-Some utilities that match regular expressions provide a nonstandard
-@samp{[:ascii:]} character class; @command{awk} does not. However, you
-can simulate such a construct using @samp{[\x00-\x7F]}. This matches
-all values numerically between zero and 127, which is the defined
-range of the ASCII character set. Use a complemented character list
-(@samp{[^\x00-\x7F]}) to match any single-byte characters that are not
-in the ASCII range.
-
-@quotation NOTE
-Some older versions of Unix @command{awk}
-treat @code{[:blank:]} like @code{[:space:]}, incorrectly matching
-more characters than they should. Caveat Emptor.
-@end quotation
-
-@cindex bracket expressions @subentry collating elements
-@cindex bracket expressions @subentry non-ASCII
-@cindex collating elements
-Two additional special sequences can appear in bracket expressions.
-These apply to non-ASCII character sets, which can have single symbols
-(called @dfn{collating elements}) that are represented with more than one
-character. They can also have several characters that are equivalent for
-@dfn{collating}, or sorting, purposes. (For example, in French, a plain ``e''
-and a grave-accented ``@`e'' are equivalent.)
-These sequences are:
-
-@table @asis
-@cindex bracket expressions @subentry collating symbols
-@cindex collating symbols
-@item Collating symbols
-Multicharacter collating elements enclosed between
-@samp{[.} and @samp{.]}. For example, if @samp{ch} is a collating element,
-then @samp{[[.ch.]]} is a regexp that matches this collating element, whereas
-@samp{[ch]} is a regexp that matches either @samp{c} or @samp{h}.
-
-@cindex bracket expressions @subentry equivalence classes
-@item Equivalence classes
-Locale-specific names for a list of
-characters that are equal. The name is enclosed between
-@samp{[=} and @samp{=]}.
-For example, the name @samp{e} might be used to represent all of
-``e,'' ``@^e,'' ``@`e,'' and ``@'e.'' In this case, @samp{[[=e=]]} is a regexp
-that matches any of @samp{e}, @samp{@^e}, @samp{@'e}, or @samp{@`e}.
-@end table
-
-These features are very valuable in non-English-speaking locales.
-
-@cindex internationalization @subentry localization @subentry character classes
-@cindex @command{gawk} @subentry character classes and
-@cindex POSIX @command{awk} @subentry bracket expressions and @subentry
character classes
-@quotation CAUTION
-The library functions that @command{gawk} uses for regular
-expression matching currently recognize only POSIX character classes;
-they do not recognize collating symbols or equivalence classes.
-@end quotation
-@c maybe one day ...
-
-Inside a bracket expression, an opening bracket (@samp{[}) that does
-not start a character class, collating element or equivalence class is
-taken literally. This is also true of @samp{.} and @samp{*}.
-
-@node Leftmost Longest
-@section How Much Text Matches?
-
-@cindex regular expressions @subentry leftmost longest match
-@c @cindex matching, leftmost longest
-Consider the following:
-
-@example
-echo aaaabcd | awk '@{ sub(/a+/, "<A>"); print @}'
-@end example
-
-This example uses the @code{sub()} function to make a change to the input
-record. (@code{sub()} replaces the first instance of any text matched
-by the first argument with the string provided as the second argument;
-@pxref{String Functions}.) Here, the regexp @code{/a+/} indicates ``one
-or more @samp{a} characters,'' and the replacement text is @samp{<A>}.
-
-The input contains four @samp{a} characters.
-@command{awk} (and POSIX) regular expressions always match
-the leftmost, @emph{longest} sequence of input characters that can
-match. Thus, all four @samp{a} characters are
-replaced with @samp{<A>} in this example:
-
-@example
-$ @kbd{echo aaaabcd | awk '@{ sub(/a+/, "<A>"); print @}'}
-@print{} <A>bcd
-@end example
-
-For simple match/no-match tests, this is not so important. But when doing
-text matching and substitutions with the @code{match()}, @code{sub()},
@code{gsub()},
-and @code{gensub()} functions, it is very important.
-@ifinfo
-@xref{String Functions},
-for more information on these functions.
-@end ifinfo
-Understanding this principle is also important for regexp-based record
-and field splitting (@pxref{Records},
-and also @pxref{Field Separators}).
-
-@node Computed Regexps
-@section Using Dynamic Regexps
-
-@cindex regular expressions @subentry computed
-@cindex regular expressions @subentry dynamic
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-@c @cindex operators, @code{~}
-@c @cindex operators, @code{!~}
-The righthand side of a @samp{~} or @samp{!~} operator need not be a
-regexp constant (i.e., a string of characters between slashes). It may
-be any expression. The expression is evaluated and converted to a string
-if necessary; the contents of the string are then used as the
-regexp. A regexp computed in this way is called a @dfn{dynamic
-regexp} or a @dfn{computed regexp}:
-
-@example
-BEGIN @{ digits_regexp = "[[:digit:]]+" @}
-$0 ~ digits_regexp @{ print @}
-@end example
-
-@noindent
-This sets @code{digits_regexp} to a regexp that describes one or more digits,
-and tests whether the input record matches this regexp.
-
-@quotation NOTE
-When using the @samp{~} and @samp{!~}
-operators, be aware that there is a difference between a regexp constant
-enclosed in slashes and a string constant enclosed in double quotes.
-If you are going to use a string constant, you have to understand that
-the string is, in essence, scanned @emph{twice}: the first time when
-@command{awk} reads your program, and the second time when it goes to
-match the string on the lefthand side of the operator with the pattern
-on the right. This is true of any string-valued expression (such as
-@code{digits_regexp}, shown in the previous example), not just string
constants.
-@end quotation
-
-@cindex regexp constants @subentry slashes vs.@: quotes
-@cindex @code{\} (backslash) @subentry in regexp constants
-@cindex backslash (@code{\}) @subentry in regexp constants
-@cindex @code{"} (double quote) @subentry in regexp constants
-@cindex double quote (@code{"}) @subentry in regexp constants
-What difference does it make if the string is
-scanned twice? The answer has to do with escape sequences, and particularly
-with backslashes. To get a backslash into a regular expression inside a
-string, you have to type two backslashes.
-
-For example, @code{/\*/} is a regexp constant for a literal @samp{*}.
-Only one backslash is needed. To do the same thing with a string,
-you have to type @code{"\\*"}. The first backslash escapes the
-second one so that the string actually contains the
-two characters @samp{\} and @samp{*}.
-
-@cindex troubleshooting @subentry regexp constants vs.@: string constants
-@cindex regexp constants @subentry vs.@: string constants
-@cindex string @subentry constants @subentry vs.@: regexp constants
-Given that you can use both regexp and string constants to describe
-regular expressions, which should you use? The answer is ``regexp
-constants,'' for several reasons:
-
-@itemize @value{BULLET}
-@item
-String constants are more complicated to write and
-more difficult to read. Using regexp constants makes your programs
-less error-prone. Not understanding the difference between the two
-kinds of constants is a common source of errors.
-
-@item
-It is more efficient to use regexp constants. @command{awk} can note
-that you have supplied a regexp and store it internally in a form that
-makes pattern matching more efficient. When using a string constant,
-@command{awk} must first convert the string into this internal form and
-then perform the pattern matching.
-
-@item
-Using regexp constants is better form; it shows clearly that you
-intend a regexp match.
-@end itemize
-
-@sidebar Using @code{\n} in Bracket Expressions of Dynamic Regexps
-@cindex regular expressions @subentry dynamic @subentry with embedded newlines
-@cindex newlines @subentry in dynamic regexps
-
-Some older versions of @command{awk} do not allow the newline
-character to be used inside a bracket expression for a dynamic regexp:
-
-@example
-$ @kbd{awk '$0 ~ "[ \t\n]"'}
-@error{} awk: newline in character class [
-@error{} ]...
-@error{} source line number 1
-@error{} context is
-@error{} $0 ~ "[ >>> \t\n]" <<<
-@end example
-
-@cindex newlines @subentry in regexp constants
-But a newline in a regexp constant works with no problem:
-
-@example
-$ @kbd{awk '$0 ~ /[ \t\n]/'}
-@kbd{here is a sample line}
-@print{} here is a sample line
-@kbd{Ctrl-d}
-@end example
-
-@command{gawk} does not have this problem, and it isn't likely to
-occur often in practice, but it's worth noting for future reference.
-@end sidebar
-
-@node GNU Regexp Operators
-@section @command{gawk}-Specific Regexp Operators
-
-@c This section adapted (long ago) from the regex-0.12 manual
-
-@cindex regular expressions @subentry operators @subentry @command{gawk}
-@cindex @command{gawk} @subentry regular expressions @subentry operators
-@cindex operators @subentry GNU-specific
-@cindex regular expressions @subentry operators @subentry for words
-@cindex word, regexp definition of
-GNU software that deals with regular expressions provides a number of
-additional regexp operators. These operators are described in this
-@value{SECTION} and are specific to @command{gawk};
-they are not available in other @command{awk} implementations.
-Most of the additional operators deal with word matching.
-For our purposes, a @dfn{word} is a sequence of one or more letters, digits,
-or underscores (@samp{_}):
-
-@table @code
-@c @cindex operators, @code{\s} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\s} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\s} operator (@command{gawk})
-@item \s
-Matches any space character as defined by the current locale.
-Think of it as shorthand for
-@w{@samp{[[:space:]]}}.
-
-@c @cindex operators, @code{\S} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\S} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\S} operator (@command{gawk})
-@item \S
-Matches any character that is not a space, as defined by the current locale.
-Think of it as shorthand for
-@w{@samp{[^[:space:]]}}.
-
-@c @cindex operators, @code{\w} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\w} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\w} operator (@command{gawk})
-@item \w
-Matches any word-constituent character---that is, it matches any
-letter, digit, or underscore. Think of it as shorthand for
-@w{@samp{[[:alnum:]_]}}.
-
-@c @cindex operators, @code{\W} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\W} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\W} operator (@command{gawk})
-@item \W
-Matches any character that is not word-constituent.
-Think of it as shorthand for
-@w{@samp{[^[:alnum:]_]}}.
-
-@c @cindex operators, @code{\<} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\<} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\<} operator (@command{gawk})
-@item \<
-Matches the empty string at the beginning of a word.
-For example, @code{/\<away/} matches @samp{away} but not
-@samp{stowaway}.
-
-@c @cindex operators, @code{\>} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\>} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\>} operator (@command{gawk})
-@item \>
-Matches the empty string at the end of a word.
-For example, @code{/stow\>/} matches @samp{stow} but not @samp{stowaway}.
-
-@c @cindex operators, @code{\y} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\y} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\y} operator (@command{gawk})
-@cindex word boundaries, matching
-@item \y
-Matches the empty string at either the beginning or the
-end of a word (i.e., the word boundar@strong{y}). For example,
@samp{\yballs?\y}
-matches either @samp{ball} or @samp{balls}, as a separate word.
-
-@c @cindex operators, @code{\B} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\B} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\B} operator (@command{gawk})
-@item \B
-Matches the empty string that occurs between two
-word-constituent characters. For example,
-@code{/\Brat\B/} matches @samp{crate}, but it does not match @samp{dirty rat}.
-@samp{\B} is essentially the opposite of @samp{\y}.
-Another way to think of this is that @samp{\B} matches the empty string
-provided it's not at the edge of a word.
-@end table
-
-@cindex buffers @subentry operators for
-@cindex regular expressions @subentry operators @subentry for buffers
-@cindex operators @subentry string-matching @subentry for buffers
-There are two other operators that work on buffers. In Emacs, a
-@dfn{buffer} is, naturally, an Emacs buffer.
-Other GNU programs, including @command{gawk},
-consider the entire string to match as the buffer.
-The operators are:
-
-@table @code
-@item \`
-@c @cindex operators, @code{\`} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\`} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\`} operator (@command{gawk})
-Matches the empty string at the
-beginning of a buffer (string)
-
-@c @cindex operators, @code{\'} (@command{gawk})
-@cindex backslash (@code{\}) @subentry @code{\'} operator (@command{gawk})
-@cindex @code{\} (backslash) @subentry @code{\'} operator (@command{gawk})
-@item \'
-Matches the empty string at the
-end of a buffer (string)
-@end table
-
-@cindex @code{^} (caret) @subentry regexp operator
-@cindex caret (@code{^}) @subentry regexp operator
-@cindex @code{?} (question mark) @subentry regexp operator
-@cindex question mark (@code{?}) @subentry regexp operator
-Because @samp{^} and @samp{$} always work in terms of the beginning
-and end of strings, these operators don't add any new capabilities
-for @command{awk}. They are provided for compatibility with other
-GNU software.
-
-@cindex @command{gawk} @subentry word-boundary operator
-@cindex word-boundary operator (@command{gawk})
-@cindex operators @subentry word-boundary (@command{gawk})
-In other GNU software, the word-boundary operator is @samp{\b}. However,
-that conflicts with the @command{awk} language's definition of @samp{\b}
-as backspace, so @command{gawk} uses a different letter.
-An alternative method would have been to require two backslashes in the
-GNU operators, but this was deemed too confusing. The current
-method of using @samp{\y} for the GNU @samp{\b} appears to be the
-lesser of two evils.
-
-@cindex regular expressions @subentry @command{gawk}, command-line options
-@cindex @command{gawk} @subentry command-line options, regular expressions and
-The various command-line options
-(@pxref{Options})
-control how @command{gawk} interprets characters in regexps:
-
-@table @asis
-@item No options
-In the default case, @command{gawk} provides all the facilities of
-POSIX regexps and the
-@ifnotinfo
-previously described
-GNU regexp operators.
-@end ifnotinfo
-@ifnottex
-@ifnotdocbook
-GNU regexp operators described
-in @ref{Regexp Operators}.
-@end ifnotdocbook
-@end ifnottex
-
-@item @option{--posix}
-Match only POSIX regexps; the GNU operators are not special
-(e.g., @samp{\w} matches a literal @samp{w}). Interval expressions
-are allowed.
-
-@cindex Brian Kernighan's @command{awk}
-@item @option{--traditional}
-Match traditional Unix @command{awk} regexps. The GNU operators
-are not special. Because BWK @command{awk} supports them,
-the POSIX character classes (@samp{[[:alnum:]]}, etc.) are available.
-So too, interval expressions are allowed.
-Characters described by octal and hexadecimal escape sequences are
-treated literally, even if they represent regexp metacharacters.
-
-@item @option{--re-interval}
-This option remains for backwards compatibility but no longer has any
-real effect.
-@end table
-
-@node Case-sensitivity
-@section Case Sensitivity in Matching
-
-@cindex regular expressions @subentry case sensitivity
-@cindex case sensitivity @subentry regexps and
-Case is normally significant in regular expressions, both when matching
-ordinary characters (i.e., not metacharacters) and inside bracket
-expressions. Thus, a @samp{w} in a regular expression matches only a lowercase
-@samp{w} and not an uppercase @samp{W}.
-
-The simplest way to do a case-independent match is to use a bracket
-expression---for example, @samp{[Ww]}. However, this can be cumbersome if
-you need to use it often, and it can make the regular expressions harder
-to read. There are two alternatives that you might prefer.
-
-One way to perform a case-insensitive match at a particular point in the
-program is to convert the data to a single case, using the
-@code{tolower()} or @code{toupper()} built-in string functions (which we
-haven't discussed yet;
-@pxref{String Functions}).
-For example:
-
-@example
-tolower($1) ~ /foo/ @{ @dots{} @}
-@end example
-
-@noindent
-converts the first field to lowercase before matching against it.
-This works in any POSIX-compliant @command{awk}.
-
-@cindex @command{gawk} @subentry regular expressions @subentry case sensitivity
-@cindex case sensitivity @subentry @command{gawk}
-@cindex differences in @command{awk} and @command{gawk} @subentry regular
expressions
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-@cindex @code{IGNORECASE} variable @subentry with @code{~} and @code{!~}
operators
-@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
-@c @cindex variables, @code{IGNORECASE}
-Another method, specific to @command{gawk}, is to set the variable
-@code{IGNORECASE} to a nonzero value (@pxref{Built-in Variables}).
-When @code{IGNORECASE} is not zero, @emph{all} regexp and string
-operations ignore case.
-
-Changing the value of @code{IGNORECASE} dynamically controls the
-case sensitivity of the program as it runs. Case is significant by
-default because @code{IGNORECASE} (like most variables) is initialized
-to zero:
-
-@example
-x = "aB"
-if (x ~ /ab/) @dots{} # this test will fail
-
-IGNORECASE = 1
-if (x ~ /ab/) @dots{} # now it will succeed
-@end example
-
-In general, you cannot use @code{IGNORECASE} to make certain rules
-case insensitive and other rules case sensitive, as there is no
-straightforward way
-to set @code{IGNORECASE} just for the pattern of
-a particular rule.@footnote{Experienced C and C++ programmers will note
-that it is possible, using something like
-@samp{IGNORECASE = 1 && /foObAr/ @{ @dots{} @}}
-and
-@samp{IGNORECASE = 0 || /foobar/ @{ @dots{} @}}.
-However, this is somewhat obscure and we don't recommend it.}
-To do this, use either bracket expressions or @code{tolower()}. However, one
-thing you can do with @code{IGNORECASE} only is dynamically turn
-case sensitivity on or off for all the rules at once.
-
-@code{IGNORECASE} can be set on the command line or in a @code{BEGIN} rule
-(@pxref{Other Arguments}; also
-@pxref{Using BEGIN/END}).
-Setting @code{IGNORECASE} from the command line is a way to make
-a program case insensitive without having to edit it.
-
-@c @cindex ISO 8859-1
-@c @cindex ISO Latin-1
-In multibyte locales, the equivalences between upper- and lowercase
-characters are tested based on the wide-character values of the locale's
-character set. Prior to @value{PVERSION} 5.0, single-byte characters were
-tested based on the ISO-8859-1 (ISO Latin-1) character set. However, as
-of @value{PVERSION} 5.0, single-byte characters are also tested based on
-the values of the locale's character set.@footnote{If you don't understand
-this, don't worry about it; it just means that @command{gawk} does the
-right thing.}
-
-The value of @code{IGNORECASE} has no effect if @command{gawk} is in
-compatibility mode (@pxref{Options}).
-Case is always significant in compatibility mode.
-
-@node Regexp Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Regular expressions describe sets of strings to be matched.
-In @command{awk}, regular expression constants are written enclosed
-between slashes: @code{/}@dots{}@code{/}.
-
-@item
-Regexp constants may be used standalone in patterns and
-in conditional expressions, or as part of matching expressions
-using the @samp{~} and @samp{!~} operators.
-
-@item
-Escape sequences let you represent nonprintable characters and
-also let you represent regexp metacharacters as literal characters
-to be matched.
-
-@item
-Regexp operators provide grouping, alternation, and repetition.
-
-@item
-Bracket expressions give you a shorthand for specifying sets
-of characters that can match at a particular point in a regexp.
-Within bracket expressions, POSIX character classes let you specify
-certain groups of characters in a locale-independent fashion.
-
-@item
-Regular expressions match the leftmost longest text in the string being
-matched. This matters for cases where you need to know the extent of
-the match, such as for text substitution and when the record separator
-is a regexp.
-
-@item
-Matching expressions may use dynamic regexps (i.e., string values
-treated as regular expressions).
-
-@item
-@command{gawk}'s @code{IGNORECASE} variable lets you control the
-case sensitivity of regexp matching. In other @command{awk}
-versions, use @code{tolower()} or @code{toupper()}.
-
-@end itemize
-
-
-@node Reading Files
-@chapter Reading Input Files
-
-@cindex reading input files
-@cindex input files @subentry reading
-@cindex input files
-@cindex @code{FILENAME} variable
-In the typical @command{awk} program,
-@command{awk} reads all input either from the
-standard input (by default, this is the keyboard, but often it is a pipe from
another
-command) or from files whose names you specify on the @command{awk}
-command line. If you specify input files, @command{awk} reads them
-in order, processing all the data from one before going on to the next.
-The name of the current input file can be found in the predefined variable
-@code{FILENAME}
-(@pxref{Built-in Variables}).
-
-@cindex records
-@cindex fields
-The input is read in units called @dfn{records}, and is processed by the
-rules of your program one record at a time.
-By default, each record is one line. Each
-record is automatically split into chunks called @dfn{fields}.
-This makes it more convenient for programs to work on the parts of a record.
-
-@cindex @code{getline} command
-On rare occasions, you may need to use the @code{getline} command.
-The @code{getline} command is valuable both because it
-can do explicit input from any number of files, and because the files
-used with it do not have to be named on the @command{awk} command line
-(@pxref{Getline}).
-
-@menu
-* Records:: Controlling how data is split into records.
-* Fields:: An introduction to fields.
-* Nonconstant Fields:: Nonconstant Field Numbers.
-* Changing Fields:: Changing the Contents of a Field.
-* Field Separators:: The field separator and how to change it.
-* Constant Size:: Reading constant width data.
-* Splitting By Content:: Defining Fields By Content
-* Testing field creation:: Checking how @command{gawk} is splitting
- records.
-* Multiple Line:: Reading multiline records.
-* Getline:: Reading files under explicit program control
- using the @code{getline} function.
-* Read Timeout:: Reading input with a timeout.
-* Retrying Input:: Retrying input after certain errors.
-* Command-line directories:: What happens if you put a directory on the
- command line.
-* Input Summary:: Input summary.
-* Input Exercises:: Exercises.
-@end menu
-
-@node Records
-@section How Input Is Split into Records
-
-@cindex input @subentry splitting into records
-@cindex records @subentry splitting input into
-@cindex @code{NR} variable
-@cindex @code{FNR} variable
-@command{awk} divides the input for your program into records and fields.
-It keeps track of the number of records that have been read so far from
-the current input file. This value is stored in a predefined variable
-called @code{FNR}, which is reset to zero every time a new file is started.
-Another predefined variable, @code{NR}, records the total number of input
-records read so far from all @value{DF}s. It starts at zero, but is
-never automatically reset to zero.
-
-Normally, records are separated by newline characters. You can control how
-records are separated by assigning values to the built-in variable @code{RS}.
-If @code{RS} is any single character, that character separates records.
-Otherwise (in @command{gawk}), @code{RS} is treated as a regular expression.
-This mechanism is explained in greater detail shortly.
-
-@quotation NOTE
-When @command{gawk} is invoked with the @option{--csv} option, nothing
-in this @value{SECTION} applies. @xref{Comma Separated Fields}, for the
-details.
-@end quotation
-
-@menu
-* awk split records:: How standard @command{awk} splits records.
-* gawk split records:: How @command{gawk} splits records.
-@end menu
-
-@node awk split records
-@subsection Record Splitting with Standard @command{awk}
-
-@cindex separators @subentry for records
-@cindex record separators
-Records are separated by a character called the @dfn{record separator}.
-By default, the record separator is the newline character.
-This is why records are, by default, single lines.
-To use a different character for the record separator,
-simply assign that character to the predefined variable @code{RS}.
-
-@cindex record separators @subentry newlines as
-@cindex newlines @subentry as record separators
-@cindex @code{RS} variable
-Like any other variable,
-the value of @code{RS} can be changed in the @command{awk} program
-with the assignment operator, @samp{=}
-(@pxref{Assignment Ops}).
-The new record-separator character should be enclosed in quotation marks,
-which indicate a string constant. Often, the right time to do this is
-at the beginning of execution, before any input is processed,
-so that the very first record is read with the proper separator.
-To do this, use the special @code{BEGIN} pattern
-(@pxref{BEGIN/END}).
-For example:
-
-@example
-awk 'BEGIN @{ RS = "u" @}
- @{ print $0 @}' mail-list
-@end example
-
-@noindent
-changes the value of @code{RS} to @samp{u}, before reading any input.
-The new value is a string whose first character is the letter ``u''; as a
result, records
-are separated by the letter ``u''. Then the input file is read, and the second
-rule in the @command{awk} program (the action with no pattern) prints each
-record. Because each @code{print} statement adds a newline at the end of
-its output, this @command{awk} program copies the input
-with each @samp{u} changed to a newline. Here are the results of running
-the program on @file{mail-list}:
-
-@example
-@group
-$ @kbd{awk 'BEGIN @{ RS = "u" @}}
-> @kbd{@{ print $0 @}' mail-list}
-@end group
-@print{} Amelia 555-5553 amelia.zodiac
-@print{} sq
-@print{} e@@gmail.com F
-@print{} Anthony 555-3412 anthony.assert
-@print{} ro@@hotmail.com A
-@print{} Becky 555-7685 becky.algebrar
-@print{} m@@gmail.com A
-@print{} Bill 555-1675 bill.drowning@@hotmail.com A
-@print{} Broderick 555-0542 broderick.aliq
-@print{} otiens@@yahoo.com R
-@print{} Camilla 555-2912 camilla.inf
-@print{} sar
-@print{} m@@skynet.be R
-@print{} Fabi
-@print{} s 555-1234 fabi
-@print{} s.
-@print{} ndevicesim
-@print{} s@@
-@print{} cb.ed
-@print{} F
-@print{} J
-@print{} lie 555-6699 j
-@print{} lie.perscr
-@print{} tabor@@skeeve.com F
-@print{} Martin 555-6480 martin.codicib
-@print{} s@@hotmail.com A
-@print{} Sam
-@print{} el 555-3430 sam
-@print{} el.lanceolis@@sh
-@print{} .ed
-@print{} A
-@print{} Jean-Pa
-@print{} l 555-2127 jeanpa
-@print{} l.campanor
-@print{} m@@ny
-@print{} .ed
-@print{} R
-@print{}
-@end example
-
-@noindent
-Note that the entry for the name @samp{Bill} is not split.
-In the original @value{DF}
-(@pxref{Sample Data Files}),
-the line looks like this:
-
-@example
-Bill 555-1675 bill.drowning@@hotmail.com A
-@end example
-
-@noindent
-It contains no @samp{u}, so there is no reason to split the record,
-unlike the others, which each have one or more occurrences of the @samp{u}.
-In fact, this record is treated as part of the previous record;
-the newline separating them in the output
-is the original newline in the @value{DF}, not the one added by
-@command{awk} when it printed the record!
-
-@cindex record separators @subentry changing
-@cindex separators @subentry for records
-Another way to change the record separator is on the command line,
-using the variable-assignment feature
-(@pxref{Other Arguments}):
-
-@example
-awk '@{ print $0 @}' RS="u" mail-list
-@end example
-
-@noindent
-This sets @code{RS} to @samp{u} before processing @file{mail-list}.
-
-Using an alphabetic character such as @samp{u} for the record separator
-is highly likely to produce strange results.
-Using an unusual character such as @samp{/} is more likely to
-produce correct behavior in the majority of cases, but there
-are no guarantees. The moral is: Know Your Data.
-
-@command{gawk} allows @code{RS} to be a full regular expression
-(discussed shortly; @pxref{gawk split records}). Even so, using
-a regular expression metacharacter, such as @samp{.} as the single
-character in the value of @code{RS} has no special effect: it is
-treated literally. This is required for backwards compatibility with
-both Unix @command{awk} and with POSIX.
-
-@cindex dark corner @subentry input files
-Reaching the end of an input file terminates the current input record,
-even if the last character in the file is not the character in @code{RS}.
-@value{DARKCORNER}
-
-@cindex empty strings @seeentry{null strings}
-@cindex null strings
-@cindex strings @subentry empty @seeentry{null strings}
-The empty string @code{""} (a string without any characters)
-has a special meaning
-as the value of @code{RS}. It means that records are separated
-by one or more blank lines and nothing else.
-@xref{Multiple Line} for more details.
-
-If you change the value of @code{RS} in the middle of an @command{awk} run,
-the new value is used to delimit subsequent records, but the record
-currently being processed, as well as records already processed, are not
-affected.
-
-@cindex @command{gawk} @subentry @code{RT} variable in
-@cindex @code{RT} variable
-@cindex records @subentry terminating
-@cindex terminating records
-@cindex differences in @command{awk} and @command{gawk} @subentry record
separators
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{RS}/@code{RT} variables
-@cindex regular expressions @subentry as record separators
-@cindex record separators @subentry regular expressions as
-@cindex separators @subentry for records @subentry regular expressions as
-After the end of the record has been determined, @command{gawk}
-sets the variable @code{RT} to the text in the input that matched
-@code{RS}.
-
-@node gawk split records
-@subsection Record Splitting with @command{gawk}
-
-@cindex common extensions @subentry @code{RS} as a regexp
-@cindex extensions @subentry common @subentry @code{RS} as a regexp
-When using @command{gawk}, the value of @code{RS} is not limited to a
-one-character string. If it contains more than one character, it is
-treated as a regular expression
-(@pxref{Regexp}). @value{COMMONEXT}
-In general, each record
-ends at the next string that matches the regular expression; the next
-record starts at the end of the matching string. This general rule is
-actually at work in the usual case, where @code{RS} contains just a
-newline: a record ends at the beginning of the next matching string (the
-next newline in the input), and the following record starts just after
-the end of this string (at the first character of the following line).
-The newline, because it matches @code{RS}, is not part of either record.
-
-When @code{RS} is a single character, @code{RT}
-contains the same single character. However, when @code{RS} is a
-regular expression, @code{RT} contains
-the actual input text that matched the regular expression.
-
-If the input file ends without any text matching @code{RS},
-@command{gawk} sets @code{RT} to the null string.
-
-The following example illustrates both of these features.
-It sets @code{RS} equal to a regular expression that
-matches either a newline or a series of one or more uppercase letters
-with optional leading and/or trailing whitespace:
-
-@example
-@group
-$ @kbd{echo record 1 AAAA record 2 BBBB record 3 |}
-> @kbd{gawk 'BEGIN @{ RS = "\n|( *[[:upper:]]+ *)" @}}
-> @kbd{@{ print "Record =", $0,"and RT = [" RT "]" @}'}
-@end group
-@print{} Record = record 1 and RT = [ AAAA ]
-@print{} Record = record 2 and RT = [ BBBB ]
-@print{} Record = record 3 and RT = [
-@print{} ]
-@end example
-
-@noindent
-The square brackets delineate the contents of @code{RT}, letting you
-see the leading and trailing whitespace. The final value of
-@code{RT} is a newline.
-@xref{Simple Sed} for a more useful example
-of @code{RS} as a regexp and @code{RT}.
-
-If you set @code{RS} to a regular expression that allows optional
-trailing text, such as @samp{RS = "abc(XYZ)?"}, it is possible, due
-to implementation constraints, that @command{gawk} may match the leading
-part of the regular expression, but not the trailing part, particularly
-if the input text that could match the trailing part is fairly long.
-@command{gawk} attempts to avoid this problem, but currently, there's
-no guarantee that this will never happen.
-
-@sidebar Caveats When Using Regular Expressions for @code{RS}
-Remember that in @command{awk}, the @samp{^} and @samp{$} anchor
-metacharacters match the beginning and end of a @emph{string}, and not
-the beginning and end of a @emph{line}. As a result, something like
-@samp{RS = "^[[:upper:]]"} can only match at the beginning of a file.
-This is because @command{gawk} views the input file as one long string
-that happens to contain newline characters.
-It is thus best to avoid anchor metacharacters in the value of @code{RS}.
-
-Record splitting with regular expressions works differently than
-regexp matching with the @code{sub()}, @code{gsub()}, and @code{gensub()}
-(@pxref{String Functions}). Those functions allow a regexp to match the empty
string;
-record splitting does not. Thus, for example @samp{RS = "()"} does @emph{not}
-split records between characters.
-@end sidebar
-
-@cindex @command{gawk} @subentry @code{RT} variable in
-@cindex @code{RT} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{RS}/@code{RT} variables
-The use of @code{RS} as a regular expression and the @code{RT}
-variable are @command{gawk} extensions; they are not available in
-compatibility mode
-(@pxref{Options}).
-In compatibility mode, only the first character of the value of
-@code{RS} determines the end of the record.
-
-@cindex Brian Kernighan's @command{awk}
-@command{mawk} has allowed @code{RS} to be a regexp for decades.
-As of October, 2019, BWK @command{awk} also supports it. Neither
-version supplies @code{RT}, however.
-
-@sidebar @code{RS = "\0"} Is Not Portable
-@cindex portability @subentry data files as single record
-There are times when you might want to treat an entire @value{DF} as a
-single record. The only way to make this happen is to give @code{RS}
-a value that you know doesn't occur in the input file. This is hard
-to do in a general way, such that a program always works for arbitrary
-input files.
-
-You might think that for text files, the @sc{nul} character, which
-consists of a character with all bits equal to zero, is a good
-value to use for @code{RS} in this case:
-
-@example
-BEGIN @{ RS = "\0" @} # whole file becomes one record?
-@end example
-
-@cindex differences in @command{awk} and @command{gawk} @subentry strings
@subentry storing
-@command{gawk} in fact accepts this, and uses the @sc{nul}
-character for the record separator.
-This works for certain special files, such as @file{/proc/environ} on
-GNU/Linux systems, where the @sc{nul} character is in fact the record
separator.
-However, this usage is @emph{not} portable
-to most other @command{awk} implementations.
-
-@cindex dark corner @subentry strings, storing
-Almost all other @command{awk} implementations@footnote{At least that we know
-about.} store strings internally as C-style strings. C strings use the
-@sc{nul} character as the string terminator. In effect, this means that
-@samp{RS = "\0"} is the same as @samp{RS = ""}.
-@value{DARKCORNER}
-
-It happens that recent versions of @command{mawk} can use the @sc{nul}
-character as a record separator. However, this is a special case:
-@command{mawk} does not allow embedded @sc{nul} characters in strings.
-(This may change in a future version of @command{mawk}.)
-
-@cindex records @subentry treating files as
-@cindex treating files, as single records
-@cindex single records, treating files as
-@xref{Readfile Function} for an interesting way to read
-whole files. If you are using @command{gawk}, see @ref{Extension Sample
-Readfile} for another option.
-@end sidebar
-
-@node Fields
-@section Examining Fields
-
-@cindex examining fields
-@cindex fields
-@cindex accessing fields
-@cindex fields @subentry examining
-@cindex whitespace @subentry definition of
-When @command{awk} reads an input record, the record is
-automatically @dfn{parsed} or separated by the @command{awk} utility into
chunks
-called @dfn{fields}. By default, fields are separated by @dfn{whitespace},
-like words in a line.
-Whitespace in @command{awk} means any string of one or more spaces,
-TABs, or newlines; other characters
-that are considered whitespace by other languages
-(such as formfeed, vertical tab, etc.) are @emph{not} considered
-whitespace by @command{awk}.
-
-The purpose of fields is to make it more convenient for you to refer to
-these pieces of the record. You don't have to use them---you can
-operate on the whole record if you want---but fields are what make
-simple @command{awk} programs so powerful.
-
-@cindex field operator @code{$}
-@cindex @code{$} (dollar sign) @subentry @code{$} field operator
-@cindex dollar sign (@code{$}) @subentry @code{$} field operator
-@cindex field operators, dollar sign as
-You use a dollar sign (@samp{$})
-to refer to a field in an @command{awk} program,
-followed by the number of the field you want. Thus, @code{$1}
-refers to the first field, @code{$2} to the second, and so on.
-(Unlike in the Unix shells, the field numbers are not limited to single digits.
-@code{$127} is the 127th field in the record.)
-For example, suppose the following is a line of input:
-
-@example
-This seems like a pretty nice example.
-@end example
-
-@noindent
-Here the first field, or @code{$1}, is @samp{This}, the second field, or
-@code{$2}, is @samp{seems}, and so on. Note that the last field,
-@code{$7}, is @samp{example.}. Because there is no space between the
-@samp{e} and the @samp{.}, the period is considered part of the seventh
-field.
-
-@cindex @code{NF} variable
-@cindex fields @subentry number of
-@code{NF} is a predefined variable whose value is the number of fields
-in the current record. @command{awk} automatically updates the value
-of @code{NF} each time it reads a record. No matter how many fields
-there are, the last field in a record can be represented by @code{$NF}.
-So, @code{$NF} is the same as @code{$7}, which is @samp{example.}.
-If you try to reference a field beyond the last
-one (such as @code{$8} when the record has only seven fields), you get
-the empty string. If used in a numeric operation, you get zero.@footnote{In
-either case, with the @option{--lint} option, @command{gawk} warns that you
-are referencing an uninitialized field.}
-
-The use of @code{$0}, which looks like a reference to the ``zeroth'' field, is
-a special case: it represents the whole input record. Use it
-when you are not interested in specific fields.
-Here are some more examples:
-
-@example
-$ @kbd{awk '$1 ~ /li/ @{ print $0 @}' mail-list}
-@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F
-@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F
-@end example
-
-@noindent
-This example prints each record in the file @file{mail-list} whose first
-field contains the string @samp{li}.
-
-By contrast, the following example looks for @samp{li} in @emph{the
-entire record} and prints the first and last fields for each matching
-input record:
-
-@example
-$ @kbd{awk '/li/ @{ print $1, $NF @}' mail-list}
-@print{} Amelia F
-@print{} Broderick R
-@print{} Julie F
-@print{} Samuel A
-@end example
-
-@node Nonconstant Fields
-@section Nonconstant Field Numbers
-@cindex fields @subentry numbers
-@cindex field numbers
-
-A field number need not be a constant. Any expression in
-the @command{awk} language can be used after a @samp{$} to refer to a
-field. The value of the expression specifies the field number. If the
-value is a string, rather than a number, it is converted to a number.
-Consider this example:
-
-@example
-awk '@{ print $NR @}'
-@end example
-
-@noindent
-Recall that @code{NR} is the number of records read so far: one in the
-first record, two in the second, and so on. So this example prints the first
-field of the first record, the second field of the second record, and so
-on. For the twentieth record, field number 20 is printed; most likely,
-the record has fewer than 20 fields, so this prints a blank line.
-Here is another example of using expressions as field numbers:
-
-@example
-awk '@{ print $(2*2) @}' mail-list
-@end example
-
-@command{awk} evaluates the expression @samp{(2*2)} and uses
-its value as the number of the field to print. The @samp{*}
-represents multiplication, so the expression @samp{2*2} evaluates to four.
-The parentheses are used so that the multiplication is done before the
-@samp{$} operation; they are necessary whenever there is a binary
-operator@footnote{A @dfn{binary operator}, such as @samp{*} for
-multiplication, is one that takes two operands. The distinction
-is required because @command{awk} also has unary (one-operand)
-and ternary (three-operand) operators.}
-in the field-number expression. This example, then, prints the
-type of relationship (the fourth field) for every line of the file
-@file{mail-list}. (All of the @command{awk} operators are listed, in
-order of decreasing precedence, in
-@ref{Precedence}.)
-
-If the field number you compute is zero, you get the entire record.
-Thus, @samp{$(2-2)} has the same value as @code{$0}. Negative field
-numbers are not allowed; trying to reference one usually terminates
-the program. (The POSIX standard does not define
-what happens when you reference a negative field number. @command{gawk}
-notices this and terminates your program. Other @command{awk}
-implementations may behave differently.)
-
-As mentioned in @ref{Fields},
-@command{awk} stores the current record's number of fields in the built-in
-variable @code{NF} (also @pxref{Built-in Variables}). Thus, the expression
-@code{$NF} is not a special feature---it is the direct consequence of
-evaluating @code{NF} and using its value as a field number.
-
-@node Changing Fields
-@section Changing the Contents of a Field
-
-@cindex fields @subentry changing contents of
-The contents of a field, as seen by @command{awk}, can be changed within an
-@command{awk} program; this changes what @command{awk} perceives as the
-current input record. (The actual input is untouched; @command{awk}
@emph{never}
-modifies the input file.)
-Consider the following example and its output:
-
-@example
-$ @kbd{awk '@{ nboxes = $3 ; $3 = $3 - 10}
-> @kbd{print nboxes, $3 @}' inventory-shipped}
-@print{} 25 15
-@print{} 32 22
-@print{} 24 14
-@dots{}
-@end example
-
-@noindent
-The program first saves the original value of field three in the variable
-@code{nboxes}.
-The @samp{-} sign represents subtraction, so this program reassigns
-field three, @code{$3}, as the original value of field three minus ten:
-@samp{$3 - 10}. (@xref{Arithmetic Ops}.)
-Then it prints the original and new values for field three.
-(Someone in the warehouse made a consistent mistake while inventorying
-the red boxes.)
-
-For this to work, the text in @code{$3} must make sense
-as a number; the string of characters must be converted to a number
-for the computer to do arithmetic on it. The number resulting
-from the subtraction is converted back to a string of characters that
-then becomes field three.
-@xref{Conversion}.
-
-When the value of a field is changed (as perceived by @command{awk}), the
-text of the input record is recalculated to contain the new field where
-the old one was. In other words, @code{$0} changes to reflect the altered
-field. Thus, this program
-prints a copy of the input file, with 10 subtracted from the second
-field of each line:
-
-@example
-$ @kbd{awk '@{ $2 = $2 - 10; print $0 @}' inventory-shipped}
-@print{} Jan 3 25 15 115
-@print{} Feb 5 32 24 226
-@print{} Mar 5 24 34 228
-@dots{}
-@end example
-
-It is also possible to assign contents to fields that are out
-of range. For example:
-
-@example
-$ @kbd{awk '@{ $6 = ($5 + $4 + $3 + $2)}
-> @kbd{ print $6 @}' inventory-shipped}
-@print{} 168
-@print{} 297
-@print{} 301
-@dots{}
-@end example
-
-@cindex adding @subentry fields
-@cindex fields @subentry adding
-@noindent
-We've just created @code{$6}, whose value is the sum of fields
-@code{$2}, @code{$3}, @code{$4}, and @code{$5}. The @samp{+} sign
-represents addition. For the file @file{inventory-shipped}, @code{$6}
-represents the total number of parcels shipped for a particular month.
-
-Creating a new field changes @command{awk}'s internal copy of the current
-input record, which is the value of @code{$0}. Thus, if you do @samp{print $0}
-after adding a field, the record printed includes the new field, with
-the appropriate number of field separators between it and the previously
-existing fields.
-
-@cindex @code{OFS} variable
-@cindex output field separator @seeentry{@code{OFS} variable}
-@cindex field separator @seealso{@code{OFS}}
-This recomputation affects and is affected by
-@code{NF} (the number of fields; @pxref{Fields}).
-For example, the value of @code{NF} is set to the number of the highest
-field you create.
-The exact format of @code{$0} is also affected by a feature that has not been
discussed yet:
-the @dfn{output field separator}, @code{OFS},
-used to separate the fields (@pxref{Output Separators}).
-
-Note, however, that merely @emph{referencing} an out-of-range field
-does @emph{not} change the value of either @code{$0} or @code{NF}.
-Referencing an out-of-range field only produces an empty string. For
-example:
-
-@example
-if ($(NF+1) != "")
- print "can't happen"
-else
- print "everything is normal"
-@end example
-
-@noindent
-should print @samp{everything is normal}, because @code{NF+1} is certain
-to be out of range. (@xref{If Statement}
-for more information about @command{awk}'s @code{if-else} statements.
-@xref{Typing and Comparison}
-for more information about the @samp{!=} operator.)
-
-It is important to note that making an assignment to an existing field
-changes the
-value of @code{$0} but does not change the value of @code{NF},
-even when you assign the empty string to a field. For example:
-
-@example
-$ @kbd{echo a b c d | awk '@{ OFS = ":"; $2 = ""}
-> @kbd{print $0; print NF @}'}
-@print{} a::c:d
-@print{} 4
-@end example
-
-@noindent
-The field is still there; it just has an empty value, delimited by
-the two colons between @samp{a} and @samp{c}.
-This example shows what happens if you create a new field:
-
-@example
-$ @kbd{echo a b c d | awk '@{ OFS = ":"; $2 = ""; $6 = "new"}
-> @kbd{print $0; print NF @}'}
-@print{} a::c:d::new
-@print{} 6
-@end example
-
-@noindent
-The intervening field, @code{$5}, is created with an empty value
-(indicated by the second pair of adjacent colons),
-and @code{NF} is updated with the value six.
-
-@cindex dark corner @subentry @code{NF} variable, decrementing
-@cindex @code{NF} variable @subentry decrementing
-Decrementing @code{NF} throws away the values of the fields
-after the new value of @code{NF} and recomputes @code{$0}.
-@value{DARKCORNER}
-Here is an example:
-
-@example
-$ @kbd{echo a b c d e f | awk '@{ print "NF =", NF;}
-> @kbd{ NF = 3; print $0 @}'}
-@print{} NF = 6
-@print{} a b c
-@end example
-
-@cindex portability @subentry @code{NF} variable, decrementing
-@quotation CAUTION
-Some versions of @command{awk} don't
-rebuild @code{$0} when @code{NF} is decremented.
-Until August, 2018, this included BWK @command{awk}; fortunately
-his version now handles this correctly.
-@end quotation
-
-Finally, there are times when it is convenient to force
-@command{awk} to rebuild the entire record, using the current
-values of the fields and @code{OFS}. To do this, use the
-seemingly innocuous assignment:
-
-@example
-@group
-$1 = $1 # force record to be reconstituted
-print $0 # or whatever else with $0
-@end group
-@end example
-
-@noindent
-This forces @command{awk} to rebuild the record. It does help
-to add a comment, as we've shown here.
-
-There is a flip side to the relationship between @code{$0} and
-the fields. Any assignment to @code{$0} causes the record to be
-reparsed into fields using the @emph{current} value of @code{FS}.
-This also applies to any built-in function that updates @code{$0},
-such as @code{sub()} and @code{gsub()}
-(@pxref{String Functions}).
-
-@sidebar Understanding @code{$0}
-
-It is important to remember that @code{$0} is the @emph{full}
-record, exactly as it was read from the input. This includes
-any leading or trailing whitespace, and the exact whitespace (or other
-characters) that separates the fields.
-
-It is a common error to try to change the field separators
-in a record simply by setting @code{FS} and @code{OFS}, and then
-expecting a plain @samp{print} or @samp{print $0} to print the
-modified record.
-
-But this does not work, because nothing was done to change the record
-itself. Instead, you must force the record to be rebuilt, typically
-with a statement such as @samp{$1 = $1}, as described earlier.
-@end sidebar
-
-
-@node Field Separators
-@section Specifying How Fields Are Separated
-
-@menu
-* Default Field Splitting:: How fields are normally separated.
-* Regexp Field Splitting:: Using regexps as the field separator.
-* Single Character Fields:: Making each character a separate field.
-* Comma Separated Fields:: Working with CSV files.
-* Command Line Field Separator:: Setting @code{FS} from the command line.
-* Full Line Fields:: Making the full line be a single field.
-* Field Splitting Summary:: Some final points and a summary table.
-@end menu
-
-@cindex @code{FS} variable
-@cindex fields @subentry separating
-@cindex field separator
-@cindex fields @subentry separating
-The @dfn{field separator}, which is either a single character or a regular
-expression, controls the way @command{awk} splits an input record into fields.
-@command{awk} scans the input record for character sequences that
-match the separator; the fields themselves are the text between the matches.
-
-In the examples that follow, we use the bullet symbol (@bullet{}) to
-represent spaces in the output.
-If the field separator is @samp{oo}, then the following line:
-
-@example
-moo goo gai pan
-@end example
-
-@noindent
-is split into three fields: @samp{m}, @samp{@bullet{}g}, and
-@samp{@bullet{}gai@bullet{}pan}.
-Note the leading spaces in the values of the second and third fields.
-
-@cindex troubleshooting @subentry @command{awk} uses @code{FS} not @code{IFS}
-The field separator is represented by the predefined variable @code{FS}.
-Shell programmers take note: @command{awk} does @emph{not} use the
-name @code{IFS} that is used by the POSIX-compliant shells (such as
-the Unix Bourne shell, @command{sh}, or Bash).
-
-@cindex @code{FS} variable @subentry changing value of
-The value of @code{FS} can be changed in the @command{awk} program with the
-assignment operator, @samp{=} (@pxref{Assignment Ops}).
-Often, the right time to do this is at the beginning of execution
-before any input has been processed, so that the very first record
-is read with the proper separator. To do this, use the special
-@code{BEGIN} pattern
-(@pxref{BEGIN/END}).
-For example, here we set the value of @code{FS} to the string
-@code{":"}:
-
-@example
-awk 'BEGIN @{ FS = ":" @} ; @{ print $2 @}'
-@end example
-
-@cindex @code{BEGIN} pattern
-@noindent
-Given the input line:
-
-@example
-John Q. Smith: 29 Oak St.: Walamazoo: MI 42139
-@end example
-
-@noindent
-this @command{awk} program extracts and prints the string
-@samp{@bullet{}29@bullet{}Oak@bullet{}St.}.
-
-@cindex field separator @subentry choice of
-@cindex regular expressions @subentry as field separators
-@cindex field separator @subentry regular expression as
-Sometimes the input data contains separator characters that don't
-separate fields the way you thought they would. For instance, the
-person's name in the example we just used might have a title or
-suffix attached, such as:
-
-@example
-John Q. Smith: LXIX: 29 Oak St.: Walamazoo: MI 42139
-@end example
-
-@noindent
-The same program would extract @samp{@bullet{}LXIX} instead of
-@samp{@bullet{}29@bullet{}Oak@bullet{}St.}.
-If you were expecting the program to print the
-address, you would be surprised. The moral is to choose your data layout and
-separator characters carefully to prevent such problems.
-(If the data is not in a form that is easy to process, perhaps you
-can massage it first with a separate @command{awk} program.)
-
-
-@node Default Field Splitting
-@subsection Whitespace Normally Separates Fields
-
-@cindex field separator @subentry whitespace as
-@cindex whitespace @subentry as field separators
-@cindex field separator @subentry @code{FS} variable and
-@cindex separators @subentry field @subentry @code{FS} variable and
-Fields are normally separated by whitespace sequences
-(spaces, TABs, and newlines), not by single spaces. Two spaces in a row do not
-delimit an empty field. The default value of the field separator @code{FS}
-is a string containing a single space, @w{@code{" "}}. If @command{awk}
-interpreted this value in the usual way, each space character would separate
-fields, so two spaces in a row would make an empty field between them.
-The reason this does not happen is that a single space as the value of
-@code{FS} is a special case---it is taken to specify the default manner
-of delimiting fields.
-
-If @code{FS} is any other single character, such as @code{","}, then
-each occurrence of that character separates two fields. Two consecutive
-occurrences delimit an empty field. If the character occurs at the
-beginning or the end of the line, that too delimits an empty field. The
-space character is the only single character that does not follow these
-rules.
-
-@node Regexp Field Splitting
-@subsection Using Regular Expressions to Separate Fields
-
-@cindex regular expressions @subentry as field separators
-@cindex field separator @subentry regular expression as
-The previous @value{SUBSECTION}
-discussed the use of single characters or simple strings as the
-value of @code{FS}.
-More generally, the value of @code{FS} may be a string containing any
-regular expression. In this case, each match in the record for the regular
-expression separates fields. For example, the assignment:
-
-@example
-FS = ", \t"
-@end example
-
-@noindent
-makes every area of an input line that consists of a comma followed by a
-space and a TAB into a field separator.
-@ifinfo
-(@samp{\t}
-is an @dfn{escape sequence} that stands for a TAB;
-@pxref{Escape Sequences},
-for the complete list of similar escape sequences.)
-@end ifinfo
-
-For a less trivial example of a regular expression, try using
-single spaces to separate fields the way single commas are used.
-@code{FS} can be set to @w{@code{"[@ ]"}} (left bracket, space, right
-bracket). This regular expression matches a single space and nothing else
-(@pxref{Regexp}).
-
-There is an important difference between the two cases of @samp{FS = @w{" "}}
-(a single space) and @samp{FS = @w{"[ \t\n]+"}}
-(a regular expression matching one or more spaces, TABs, or newlines).
-For both values of @code{FS}, fields are separated by @dfn{runs}
-(multiple adjacent occurrences) of spaces, TABs,
-and/or newlines. However, when the value of @code{FS} is @w{@code{" "}},
-@command{awk} first strips leading and trailing whitespace from
-the record and then decides where the fields are.
-For example, the following pipeline prints @samp{b}:
-
-@example
-$ @kbd{echo ' a b c d ' | awk '@{ print $2 @}'}
-@print{} b
-@end example
-
-@noindent
-However, this pipeline prints @samp{a} (note the extra spaces around
-each letter):
-
-@example
-$ @kbd{echo ' a b c d ' | awk 'BEGIN @{ FS = "[ \t\n]+" @}}
-> @kbd{@{ print $2 @}'}
-@print{} a
-@end example
-
-@noindent
-@cindex null strings
-@cindex strings @subentry null
-In this case, the first field is null, or empty.
-
-The stripping of leading and trailing whitespace also comes into
-play whenever @code{$0} is recomputed. For instance, study this pipeline:
-
-@example
-$ @kbd{echo ' a b c d' | awk '@{ print; $2 = $2; print @}'}
-@print{} a b c d
-@print{} a b c d
-@end example
-
-@noindent
-The first @code{print} statement prints the record as it was read,
-with leading whitespace intact. The assignment to @code{$2} rebuilds
-@code{$0} by concatenating @code{$1} through @code{$NF} together,
-separated by the value of @code{OFS} (which is a space by default).
-Because the leading whitespace was ignored when finding @code{$1},
-it is not part of the new @code{$0}. Finally, the last @code{print}
-statement prints the new @code{$0}.
-
-@cindex @code{FS} variable @subentry containing @code{^}
-@cindex @code{^} (caret) @subentry in @code{FS}
-@cindex dark corner @subentry @code{^}, in @code{FS}
-There is an additional subtlety to be aware of when using regular expressions
-for field splitting.
-It is not well specified in the POSIX standard, or anywhere else, what @samp{^}
-means when splitting fields. Does the @samp{^} match only at the beginning of
-the entire record? Or is each field separator a new string? It turns out that
-different @command{awk} versions answer this question differently, and you
-should not rely on any specific behavior in your programs.
-@value{DARKCORNER}
-
-@cindex Brian Kernighan's @command{awk}
-As a point of information, BWK @command{awk} allows @samp{^}
-to match only at the beginning of the record. @command{gawk}
-also works this way. For example:
-
-@example
-$ @kbd{echo 'xxAA xxBxx C' |}
-> @kbd{gawk -F '(^x+)|( +)' '@{ for (i = 1; i <= NF; i++)}
-> @kbd{ printf "-->%s<--\n", $i @}'}
-@print{} --><--
-@print{} -->AA<--
-@print{} -->xxBxx<--
-@print{} -->C<--
-@end example
-
-Finally, field splitting with regular expressions works differently than
-regexp matching with the @code{sub()}, @code{gsub()}, and @code{gensub()}
-(@pxref{String Functions}). Those functions allow a regexp to match the
-empty string; field splitting does not. Thus, for example @samp{FS =
-"()"} does @emph{not} split fields between characters.
-
-@node Single Character Fields
-@subsection Making Each Character a Separate Field
-
-@cindex common extensions @subentry single character fields
-@cindex extensions @subentry common @subentry single character fields
-@cindex differences in @command{awk} and @command{gawk} @subentry
single-character fields
-@cindex single-character fields
-@cindex fields @subentry single-character
-There are times when you may want to examine each character
-of a record separately. This can be done in @command{gawk} by
-simply assigning the null string (@code{""}) to @code{FS}. @value{COMMONEXT}
-In this case,
-each individual character in the record becomes a separate field.
-For example:
-
-@example
-$ @kbd{echo a b | gawk 'BEGIN @{ FS = "" @}}
-> @kbd{@{}
-> @kbd{for (i = 1; i <= NF; i = i + 1)}
-> @kbd{print "Field", i, "is", $i}
-> @kbd{@}'}
-@print{} Field 1 is a
-@print{} Field 2 is
-@print{} Field 3 is b
-@end example
-
-@cindex dark corner @subentry @code{FS} as null string
-@cindex @code{FS} variable @subentry null string as
-Traditionally, the behavior of @code{FS} equal to @code{""} was not defined.
-In this case, most versions of Unix @command{awk} simply treat the entire
record
-as only having one field.
-@value{DARKCORNER}
-In compatibility mode
-(@pxref{Options}),
-if @code{FS} is the null string, then @command{gawk} also
-behaves this way.
-
-@node Comma Separated Fields
-@subsection Working With Comma Separated Value Files
-
-@cindex comma separated values (CSV) data @subentry records and fields
-@cindex CSV (comma separated values) data @subentry records and fields
-Many commonly-used tools use a comma to separate fields, instead of whitespace.
-This is particularly true of popular spreadsheet programs. There is no
-universally accepted standard for the format of these files, although
-@uref{http://www.ietf.org/rfc/rfc4180, RFC 4180} lists the common
-practices.
-
-For decades, anyone wishing to work with CSV files and @command{awk}
-had to ``roll their own'' solution.
-(For an example, @pxref{Splitting By Content}).
-In 2023, Brian Kernighan decided to add CSV support to his version of
-@command{awk}. In order to keep up, @command{gawk} too provides the same
-support as his version.
-To use CSV data, invoke @command{gawk} with either of the
-@option{-k} or @option{--csv} options.
-
-Fields in CSV files are separated by commas. In order to allow a comma
-to appear inside a field (i.e., as data), the field may be quoted
-by beginning and ending it with double quotes. In order to allow a double
-quote inside a field, the field @emph{must} be quoted, and two double quotes
-represent an actual double quote.
-The double quote that starts a quoted field must be the first
-character after the comma.
-@ref{table-csv-examples} shows some examples.
-
-@float Table,table-csv-examples
-@caption{Examples of CSV data}
-@multitable @columnfractions .3 .3
-@headitem Input @tab Field Contents
-@item @code{abc def} @tab @code{abc def}
-@item @code{"quoted data"} @tab @code{quoted data}
-@item @code{"quoted, data"} @tab @code{quoted, data}
-@item @code{"She said ""Stop!""."} @tab @code{She said "Stop!".}
-@end multitable
-@end float
-
-Additionally, and here's where it gets messy, newlines are also
-allowed inside double-quoted fields!
-In order to deal with such things, when processing CSV files,
-@command{gawk} scans the input data looking for newlines that
-are not enclosed in double quotes. Thus, use of the @option{--csv} option
-totally overrides normal record processing with @code{RS} (@pxref{Records}),
-as well as field splitting with any of @code{FS}, @code{FIELDWIDTHS},
-or @code{FPAT}.
-
-@cindex Kernighan, Brian @subentry quotes
-@sidebar Carriage-Return--Line-Feed Line Endings In CSV Files
-@quotation
-@code{\r\n} @i{is the invention of the devil.}
-@author Brian Kernighan
-@end quotation
-
-Many CSV files are imported from systems where the line terminator
-for text files is a carriage-return--line-feed pair
-(CR-LF, @samp{\r} followed by @samp{\n}).
-For ease of use, when processing CSV files, @command{gawk} converts
-CR-LF pairs into a single newline. That is, the @samp{\r} is removed.
-
-This occurs only when a CR is paired with an LF; a standalone CR
-is left alone. This behavior is consistent with Windows systems
-which automatically convert CR-LF in files into a plain LF in memory,
-and also with the commonly available @command{unix2dos} utility program.
-@end sidebar
-
-The behavior of the @code{split()} function (not formally discussed
-yet, see @ref{String Functions}) differs slightly when processing CSV
-files. When called with two arguments
-(@samp{split(@var{string}, @var{array})}), @code{split()}
-does CSV-based splitting. Otherwise, it behaves normally.
-
-If @option{--csv} has been used, @code{PROCINFO["CSV"]} will
-exist. Otherwise, it will not. @xref{Auto-set}.
-
-Finally, if @option{--csv} has been used, assigning a value
-to any of @code{FS}, @code{FIELDWIDTHS}, @code{FPAT}, or
-@code{RS} generates a warning message.
-
-To be clear, @command{gawk} takes
-@uref{http://www.ietf.org/rfc/rfc4180, RFC 4180} as its
-specification for CSV input data. There are no mechanisms
-for accepting nonstandard CSV data, such as files that use
-a semicolon instead of a comma as the separator.
-
-@node Command Line Field Separator
-@subsection Setting @code{FS} from the Command Line
-@cindex @option{-F} option @subentry command-line
-@cindex field separator @subentry on command line
-@cindex command line @subentry @code{FS} on, setting
-@cindex @code{FS} variable @subentry setting from command line
-
-@code{FS} can be set on the command line. Use the @option{-F} option to
-do so. For example:
-
-@example
-awk -F, '@var{program}' @var{input-files}
-@end example
-
-@noindent
-sets @code{FS} to the @samp{,} character. Notice that the option uses
-an uppercase @samp{F} instead of a lowercase @samp{f}. The latter
-option (@option{-f}) specifies a file containing an @command{awk} program.
-
-The value used for the argument to @option{-F} is processed in exactly the
-same way as assignments to the predefined variable @code{FS}.
-Any special characters in the field separator must be escaped
-appropriately. For example, to use a @samp{\} as the field separator
-on the command line, you would have to type:
-
-@example
-# same as FS = "\\"
-awk -F\\\\ '@dots{}' files @dots{}
-@end example
-
-@noindent
-@cindex field separator @subentry backslash (@code{\}) as
-@cindex @code{\} (backslash) @subentry as field separator
-@cindex backslash (@code{\}) @subentry as field separator
-Because @samp{\} is used for quoting in the shell, @command{awk} sees
-@samp{-F\\}. Then @command{awk} processes the @samp{\\} for escape
-characters (@pxref{Escape Sequences}), finally yielding
-a single @samp{\} to use for the field separator.
-
-@c @cindex historical features
-As a special case, in compatibility mode
-(@pxref{Options}),
-if the argument to @option{-F} is @samp{t}, then @code{FS} is set to
-the TAB character. If you type @samp{-F\t} at the
-shell, without any quotes, the @samp{\} gets deleted, so @command{awk}
-figures that you really want your fields to be separated with TABs and
-not @samp{t}s. Use @samp{-v FS="t"} or @samp{-F"[t]"} on the command line
-if you really do want to separate your fields with @samp{t}s.
-Use @samp{-F '\t'} when not in compatibility mode to specify that TABs
-separate fields.
-
-As an example, let's use an @command{awk} program file called @file{edu.awk}
-that contains the pattern @code{/edu/} and the action @samp{print $1}:
-
-@example
-/edu/ @{ print $1 @}
-@end example
-
-Let's also set @code{FS} to be the @samp{-} character and run the
-program on the file @file{mail-list}. The following command prints a
-list of the names of the people that work at or attend a university, and
-the first three digits of their phone numbers:
-
-@example
-$ @kbd{awk -F- -f edu.awk mail-list}
-@print{} Fabius 555
-@print{} Samuel 555
-@print{} Jean
-@end example
-
-@noindent
-Note the third line of output. The third line
-in the original file looked like this:
-
-@example
-Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
-@end example
-
-The @samp{-} as part of the person's name was used as the field
-separator, instead of the @samp{-} in the phone number that was
-originally intended. This demonstrates why you have to be careful in
-choosing your field and record separators.
-
-@cindex Unix @command{awk} @subentry password files, field separators and
-Perhaps the most common use of a single character as the field separator
-occurs when processing the Unix system password file. On many Unix
-systems, each user has a separate entry in the system password file, with one
-line per user. The information in these lines is separated by colons.
-The first field is the user's login name and the second is the user's
-encrypted or shadow password. (A shadow password is indicated by the
-presence of a single @samp{x} in the second field.) A password file
-entry might look like this:
-
-@cindex Robbins @subentry Arnold
-@example
-arnold:x:2076:10:Arnold Robbins:/home/arnold:/bin/bash
-@end example
-
-The following program searches the system password file and prints
-the entries for users whose full name is not indicated:
-
-@example
-awk -F: '$5 == ""' /etc/passwd
-@end example
-
-@node Full Line Fields
-@subsection Making the Full Line Be a Single Field
-
-Occasionally, it's useful to treat the whole input line as a
-single field. This can be done easily and portably simply by
-setting @code{FS} to @code{"\n"} (a newline):@footnote{Thanks to
-Andrew Schorr for this tip.}
-
-@example
-awk -F'\n' '@var{program}' @var{files @dots{}}
-@end example
-
-@noindent
-When you do this, @code{$1} is the same as @code{$0}.
-
-@sidebar Changing @code{FS} Does Not Affect the Fields
-
-@cindex POSIX @command{awk} @subentry field separators and
-@cindex field separator @subentry POSIX and
-According to the POSIX standard, @command{awk} is supposed to behave
-as if each record is split into fields at the time it is read.
-In particular, this means that if you change the value of @code{FS}
-after a record is read, the values of the fields (i.e., how they were split)
-should reflect the old value of @code{FS}, not the new one.
-
-@cindex dark corner @subentry field separators
-@cindex @command{sed} utility
-@cindex stream editors
-However, many older implementations of @command{awk} do not work this way.
Instead,
-they defer splitting the fields until a field is actually
-referenced. The fields are split
-using the @emph{current} value of @code{FS}!
-@value{DARKCORNER}
-This behavior can be difficult
-to diagnose. The following example illustrates the difference
-between the two methods:
-
-@example
-sed 1q /etc/passwd | awk '@{ FS = ":" ; print $1 @}'
-@end example
-
-@noindent
-which usually prints:
-
-@example
-root
-@end example
-
-@noindent
-on an incorrect implementation of @command{awk}, while @command{gawk}
-prints the full first line of the file, something like:
-
-@example
-root:x:0:0:Root:/:
-@end example
-
-(The @command{sed}@footnote{The @command{sed} utility is a ``stream editor.''
-Its behavior is also defined by the POSIX standard.}
-command prints just the first line of @file{/etc/passwd}.)
-@end sidebar
-
-@node Field Splitting Summary
-@subsection Field-Splitting Summary
-
-It is important to remember that when you assign a string constant
-as the value of @code{FS}, it undergoes normal @command{awk} string
-processing. For example, with Unix @command{awk} and @command{gawk},
-the assignment @samp{FS = "\.."} assigns the character string @code{".."}
-to @code{FS} (the backslash is stripped). This creates a regexp meaning
-``fields are separated by occurrences of any two characters.''
-If instead you want fields to be separated by a literal period followed
-by any single character, use @samp{FS = "\\.."}.
-
-The following list summarizes how fields are split, based on the value
-of @code{FS} (@samp{==} means ``is equal to''):
-
-@table @code
-@item @asis{@command{gawk} was invoked with @option{--csv}}
-Field splitting follows the rules given in @ref{Comma Separated Fields}.
-The value of @code{FS} is ignored.
-
-@item FS == " "
-Fields are separated by runs of whitespace. Leading and trailing
-whitespace are ignored. This is the default.
-
-@item FS == @var{any other single character}
-Fields are separated by each occurrence of the character. Multiple
-successive occurrences delimit empty fields, as do leading and
-trailing occurrences.
-The character can even be a regexp metacharacter; it does not need
-to be escaped.
-
-@item FS == @var{regexp}
-Fields are separated by occurrences of characters that match @var{regexp}.
-Leading and trailing matches of @var{regexp} delimit empty fields.
-
-@item FS == ""
-Each individual character in the record becomes a separate field.
-(This is a common extension; it is not specified by the POSIX standard.)
-@end table
-
-@sidebar @code{FS} and @code{IGNORECASE}
-
-The @code{IGNORECASE} variable
-(@pxref{User-modified})
-affects field splitting @emph{only} when the value of @code{FS} is a regexp.
-It has no effect when @code{FS} is a single character, even if
-that character is a letter. Thus, in the following code:
-
-@example
-FS = "c"
-IGNORECASE = 1
-$0 = "aCa"
-print $1
-@end example
-
-@noindent
-The output is @samp{aCa}. If you really want to split fields on an
-alphabetic character while ignoring case, use a regexp that will
-do it for you (e.g., @samp{FS = "[c]"}). In this case, @code{IGNORECASE}
-will take effect.
-@end sidebar
-
-
-@node Constant Size
-@section Reading Fixed-Width Data
-
-@cindex data, fixed-width
-@cindex fixed-width data
-@cindex advanced features @subentry fixed-width data
-
-@c O'Reilly doesn't like it as a note the first thing in the section.
-This @value{SECTION} discusses an advanced
-feature of @command{gawk}. If you are a novice @command{awk} user,
-you might want to skip it on the first reading.
-
-@command{gawk} provides a facility for dealing with fixed-width fields
-with no distinctive field separator. We discuss this feature in
-the following @value{SUBSECTION}s.
-
-@menu
-* Fixed width data:: Processing fixed-width data.
-* Skipping intervening:: Skipping intervening fields.
-* Allowing trailing data:: Capturing optional trailing data.
-* Fields with fixed data:: Field values with fixed-width data.
-@end menu
-
-@node Fixed width data
-@subsection Processing Fixed-Width Data
-
-An example of fixed-width data would be the input for old Fortran programs
-where numbers are run together, or the output of programs that did not
-anticipate the use of their output as input for other programs.
-
-An example of the latter is a table where all the columns are lined up
-by the use of a variable number of spaces and @emph{empty fields are
-just spaces}. Clearly, @command{awk}'s normal field splitting based
-on @code{FS} does not work well in this case. Although a portable
-@command{awk} program can use a series of @code{substr()} calls on
-@code{$0} (@pxref{String Functions}), this is awkward and inefficient
-for a large number of fields.
-
-@cindex troubleshooting @subentry fatal errors @subentry field widths,
specifying
-@cindex @command{w} utility
-@cindex @code{FIELDWIDTHS} variable
-@cindex @command{gawk} @subentry @code{FIELDWIDTHS} variable in
-The splitting of an input record into fixed-width fields is specified by
-assigning a string containing space-separated numbers to the built-in
-variable @code{FIELDWIDTHS}. Each number specifies the width of the
-field, @emph{including} columns between fields. If you want to ignore
-the columns between fields, you can specify the width as a separate
-field that is subsequently ignored. It is a fatal error to supply a
-field width that has a negative value.
-
-The following data is the output of the Unix @command{w} utility. It is useful
-to illustrate the use of @code{FIELDWIDTHS}:
-
-@example
-@group
- 10:06pm up 21 days, 14:04, 23 users
-User tty login@ idle JCPU PCPU what
-hzuo ttyV0 8:58pm 9 5 vi p24.tex
-hzang ttyV3 6:37pm 50 -csh
-eklye ttyV5 9:53pm 7 1 em thes.tex
-dportein ttyV6 8:17pm 1:47 -csh
-gierd ttyD3 10:00pm 1 elm
-dave ttyD4 9:47pm 4 4 w
-brent ttyp0 26Jun91 4:46 26:46 4:41 bash
-dave ttyq4 26Jun9115days 46 46 wnewmail
-@end group
-@end example
-
-The following program takes this input, converts the idle time to
-number of seconds, and prints out the first two fields and the calculated
-idle time:
-
-@example
-BEGIN @{ FIELDWIDTHS = "9 6 10 6 7 7 35" @}
-NR > 2 @{
- idle = $4
- sub(/^ +/, "", idle) # strip leading spaces
- if (idle == "")
- idle = 0
- if (idle ~ /:/) @{ # hh:mm
- split(idle, t, ":")
- idle = t[1] * 60 + t[2]
- @}
- if (idle ~ /days/)
- idle *= 24 * 60 * 60
-
- print $1, $2, idle
-@}
-@end example
-
-@quotation NOTE
-The preceding program uses a number of @command{awk} features that
-haven't been introduced yet.
-@end quotation
-
-Running the program on the data produces the following results:
-
-@example
-hzuo ttyV0 0
-hzang ttyV3 50
-eklye ttyV5 0
-dportein ttyV6 107
-gierd ttyD3 1
-dave ttyD4 0
-brent ttyp0 286
-dave ttyq4 1296000
-@end example
-
-Another (possibly more practical) example of fixed-width input data
-is the input from a deck of balloting cards. In some parts of
-the United States, voters mark their choices by punching holes in computer
-cards. These cards are then processed to count the votes for any particular
-candidate or on any particular issue. Because a voter may choose not to
-vote on some issue, any column on the card may be empty. An @command{awk}
-program for processing such data could use the @code{FIELDWIDTHS} feature
-to simplify reading the data. (Of course, getting @command{gawk} to run on
-a system with card readers is another story!)
-
-@node Skipping intervening
-@subsection Skipping Intervening Fields
-
-Starting in @value{PVERSION} 4.2, each field width may optionally be
-preceded by a colon-separated value specifying the number of characters
-to skip before the field starts. Thus, the preceding program could be
-rewritten to specify @code{FIELDWIDTHS} like so:
-
-@example
-BEGIN @{ FIELDWIDTHS = "8 1:5 4:7 6 1:6 1:6 2:33" @}
-@end example
-
-This strips away some of the white space separating the fields. With such
-a change, the program produces the following results:
-
-@example
-hzang ttyV3 50
-eklye ttyV5 0
-dportein ttyV6 107
-gierd ttyD3 1
-dave ttyD4 0
-brent ttyp0 286
-dave ttyq4 1296000
-@end example
-
-@node Allowing trailing data
-@subsection Capturing Optional Trailing Data
-
-There are times when fixed-width data may be followed by additional data
-that has no fixed length. Such data may or may not be present, but if
-it is, it should be possible to get at it from an @command{awk} program.
-
-Starting with @value{PVERSION} 4.2, in order to provide a way to say ``anything
-else in the record after the defined fields,'' @command{gawk}
-allows you to add a final @samp{*} character to the value of
-@code{FIELDWIDTHS}. There can only be one such character, and it must
-be the final non-whitespace character in @code{FIELDWIDTHS}.
-For example:
-
-@example
-$ @kbd{cat fw.awk} @ii{Show the program}
-@print{} BEGIN @{ FIELDWIDTHS = "2 2 *" @}
-@print{} @{ print NF, $1, $2, $3 @}
-$ @kbd{cat fw.in} @ii{Show sample input}
-@print{} 1234abcdefghi
-$ @kbd{gawk -f fw.awk fw.in} @ii{Run the program}
-@print{} 3 12 34 abcdefghi
-@end example
-
-@node Fields with fixed data
-@subsection Field Values With Fixed-Width Data
-
-So far, so good. But what happens if there isn't as much data as there
-should be based on the contents of @code{FIELDWIDTHS}? Or, what happens
-if there is more data than expected?
-
-For many years, what happens in these cases was not well defined. Starting
-with @value{PVERSION} 4.2, the rules are as follows:
-
-@table @asis
-@item Enough data for some fields
-For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4"} and the
-input record is @samp{aabbb}. In this case, @code{NF} is set to two.
-
-@item Not enough data for a field
-For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4"} and the
-input record is @samp{aab}. In this case, @code{NF} is set to two and
-@code{$2} has the value @code{"b"}. The idea is that even though there
-aren't as many characters as were expected, there are some, so the data
-should be made available to the program.
-
-@item Too much data
-For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4"} and the
-input record is @samp{aabbbccccddd}. In this case, @code{NF} is set to
-three and the extra characters (@samp{ddd}) are ignored. If you want
-@command{gawk} to capture the extra characters, supply a final @samp{*}
-in the value of @code{FIELDWIDTHS}.
-
-@item Too much data, but with @samp{*} supplied
-For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4 *"} and the
-input record is @samp{aabbbccccddd}. In this case, @code{NF} is set to
-four, and @code{$4} has the value @code{"ddd"}.
-
-@end table
-
-@node Splitting By Content
-@section Defining Fields by Content
-
-@quotation NOTE
-This whole section needs rewriting now
-that @command{gawk} has built-in CSV parsing. Sigh.
-@end quotation
-
-@menu
-* More CSV:: More on CSV files.
-* FS versus FPAT:: A subtle difference.
-@end menu
-
-@c O'Reilly doesn't like it as a note the first thing in the section.
-This @value{SECTION} discusses an advanced
-feature of @command{gawk}. If you are a novice @command{awk} user,
-you might want to skip it on the first reading.
-
-@cindex advanced features @subentry specifying field content
-Normally, when using @code{FS}, @command{gawk} defines the fields as the
-parts of the record that occur in between each field separator. In other
-words, @code{FS} defines what a field @emph{is not}, instead of what a field
-@emph{is}.
-However, there are times when you really want to define the fields by
-what they are, and not by what they are not.
-
-@cindex CSV (comma separated values) data @subentry parsing with @code{FPAT}
-@cindex Comma separated values (CSV) data @subentry parsing with @code{FPAT}
-The most notorious such case
-is comma-separated values (CSV) data. Many spreadsheet programs,
-for example, can export their data into text files, where each record is
-terminated with a newline, and fields are separated by commas. If
-commas only separated the data, there wouldn't be an issue. The problem comes
when
-one of the fields contains an @emph{embedded} comma.
-In such cases, most programs embed the field in double quotes.@footnote{The
-CSV format lacked a formal standard definition for many years.
-@uref{http://www.ietf.org/rfc/rfc4180.txt, RFC 4180}
-standardizes the most common practices.}
-So, we might have data like this:
-
-@example
-@c file eg/misc/addresses.csv
-Robbins,Arnold,"1234 A Pretty Street, NE",MyTown,MyState,12345-6789,USA
-@c endfile
-@end example
-
-@cindex @command{gawk} @subentry @code{FPAT} variable in
-@cindex @code{FPAT} variable
-The @code{FPAT} variable offers a solution for cases like this.
-The value of @code{FPAT} should be a string that provides a regular expression.
-This regular expression describes the contents of each field.
-
-In the case of CSV data as presented here, each field is either ``anything that
-is not a comma,'' or ``a double quote, anything that is not a double quote,
and a
-closing double quote.'' (There are more complicated definitions of CSV data,
-treated shortly.)
-If written as a regular expression constant
-(@pxref{Regexp}),
-we would have @code{/([^,]+)|("[^"]+")/}.
-Writing this as a string requires us to escape the double quotes, leading to:
-
-@example
-FPAT = "([^,]+)|(\"[^\"]+\")"
-@end example
-
-Putting this to use, here is a simple program to parse the data:
-
-@example
-@c file eg/misc/simple-csv.awk
-@group
-BEGIN @{
- FPAT = "([^,]+)|(\"[^\"]+\")"
-@}
-@end group
-
-@group
-@{
- print "NF = ", NF
- for (i = 1; i <= NF; i++) @{
- printf("$%d = <%s>\n", i, $i)
- @}
-@}
-@end group
-@c endfile
-@end example
-
-When run, we get the following:
-
-@example
-$ @kbd{gawk -f simple-csv.awk addresses.csv}
-NF = 7
-$1 = <Robbins>
-$2 = <Arnold>
-$3 = <"1234 A Pretty Street, NE">
-$4 = <MyTown>
-$5 = <MyState>
-$6 = <12345-6789>
-$7 = <USA>
-@end example
-
-Note the embedded comma in the value of @code{$3}.
-
-A straightforward improvement when processing CSV data of this sort
-would be to remove the quotes when they occur, with something like this:
-
-@example
-if (substr($i, 1, 1) == "\"") @{
- len = length($i)
- $i = substr($i, 2, len - 2) # Get text within the two quotes
-@}
-@end example
-
-@quotation NOTE
-Some programs export CSV data that contains embedded newlines between
-the double quotes. @command{gawk} provides no way to deal with this.
-Even though a formal specification for CSV data exists, there isn't much
-more to be done;
-the @code{FPAT} mechanism provides an elegant solution for the majority
-of cases, and the @command{gawk} developers are satisfied with that.
-@end quotation
-
-As written, the regexp used for @code{FPAT} requires that each field
-contain at least one character. A straightforward modification
-(changing the first @samp{+} to @samp{*}) allows fields to be empty:
-
-@example
-FPAT = "([^,]*)|(\"[^\"]+\")"
-@end example
-
-@c 4/2015:
-@c Consider use of FPAT = "([^,]*)|(\"[^\"]*\")"
-@c (star in latter part of value) to allow quoted strings to be empty.
-@c Per email from Ed Morton <mortoneccc@comcast.net>
-@c
-@c WONTFIX: 10/2020
-@c This is too much work. FPAT and CSV files are very flaky and
-@c fragile. Doing something like this is merely inviting trouble.
-
-As with @code{FS}, the @code{IGNORECASE} variable (@pxref{User-modified})
-affects field splitting with @code{FPAT}.
-
-Assigning a value to @code{FPAT} overrides field splitting
-with @code{FS} and with @code{FIELDWIDTHS}.
-
-Finally, the @code{patsplit()} function makes the same functionality
-available for splitting regular strings (@pxref{String Functions}).
-
-@quotation NOTE
-Given that @command{gawk} now has built-in CSV parsing
-(@pxref{Comma Separated Fields}), the examples presented here are obsolete.
-Nonetheless, it remains useful as an example of what @code{FPAT}-based
-field parsing can do.
-@end quotation
-
-@node More CSV
-@subsection More on CSV Files
-
-@cindex Collado, Manuel
-Manuel Collado notes that in addition to commas, a CSV field can also
-contains quotes, that have to be escaped by doubling them. The previously
-described regexps fail to accept quoted fields with both commas and
-quotes inside. He suggests that the simplest @code{FPAT} expression that
-recognizes this kind of fields is @code{/([^,]*)|("([^"]|"")+")/}. He
-provides the following input data to test these variants:
-
-@example
-@c file eg/misc/sample.csv
-p,"q,r",s
-p,"q""r",s
-p,"q,""r",s
-p,"",s
-p,,s
-@c endfile
-@end example
-
-@noindent
-And here is his test program:
-
-@example
-@c file eg/misc/test-csv.awk
-@group
-BEGIN @{
- fp[0] = "([^,]+)|(\"[^\"]+\")"
- fp[1] = "([^,]*)|(\"[^\"]+\")"
- fp[2] = "([^,]*)|(\"([^\"]|\"\")+\")"
- FPAT = fp[fpat+0]
-@}
-@end group
-
-@group
-@{
- print "<" $0 ">"
- printf("NF = %s ", NF)
- for (i = 1; i <= NF; i++) @{
- printf("<%s>", $i)
- @}
- print ""
-@}
-@end group
-@c endfile
-@end example
-
-When run on the third variant, it produces:
-
-@example
-$ @kbd{gawk -v fpat=2 -f test-csv.awk sample.csv}
-@print{} <p,"q,r",s>
-@print{} NF = 3 <p><"q,r"><s>
-@print{} <p,"q""r",s>
-@print{} NF = 3 <p><"q""r"><s>
-@print{} <p,"q,""r",s>
-@print{} NF = 3 <p><"q,""r"><s>
-@print{} <p,"",s>
-@print{} NF = 3 <p><""><s>
-@print{} <p,,s>
-@print{} NF = 3 <p><><s>
-@end example
-
-@cindex Collado, Manuel
-@cindex @code{CSVMODE} library for @command{gawk}
-@cindex CSV (comma separated values) data @subentry parsing with
@code{CSVMODE} library
-@cindex Comma separated values (CSV) data @subentry parsing with @code{FPAT}
library
-In general, using @code{FPAT} to do your own CSV parsing is like having
-a bed with a blanket that's not quite big enough. There's always a corner
-that isn't covered. We recommend, instead, that you use Manuel Collado's
-@uref{http://mcollado.z15.es/xgawk/, @code{CSVMODE} library for
@command{gawk}}.
-
-@node FS versus FPAT
-@subsection @code{FS} Versus @code{FPAT}: A Subtle Difference
-
-As we discussed earlier, @code{FS} describes the data between fields (``what
fields are not'')
-and @code{FPAT} describes the fields themselves (``what fields are'').
-This leads to a subtle difference in how fields are found when using regexps
as the value
-for @code{FS} or @code{FPAT}.
-
-In order to distinguish one field from another, there must be a non-empty
separator between
-each field. This makes intuitive sense---otherwise one could not distinguish
fields from
-separators.
-
-Thus, regular expression matching as done when splitting fields with @code{FS}
is not
-allowed to match the null string; it must always match at least one character,
in order
-to be able to proceed through the entire record.
-
-On the other hand, regular expression matching with @code{FPAT} can match the
null
-string, and the non-matching intervening characters function as the separators.
-
-This same difference is reflected in how matching is done with the
@code{split()}
-and @code{patsplit()} functions (@pxref{String Functions}).
-
-@node Testing field creation
-@section Checking How @command{gawk} Is Splitting Records
-
-@cindex @command{gawk} @subentry splitting fields and
-As we've seen, @command{gawk} provides three independent methods to split
-input records into fields. The mechanism used is based on which of the
-three variables---@code{FS}, @code{FIELDWIDTHS}, or @code{FPAT}---was
-last assigned to. In addition, an API input parser may choose to override
-the record parsing mechanism; please refer to @ref{Input Parsers} for
-further information about this feature.
-
-To restore normal field splitting after using @code{FIELDWIDTHS}
-and/or @code{FPAT}, simply assign a value to @code{FS}.
-You can use @samp{FS = FS} to do this,
-without having to know the current value of @code{FS}.
-
-In order to tell which kind of field splitting is in effect,
-use @code{PROCINFO["FS"]} (@pxref{Auto-set}).
-The value is @code{"FS"} if regular field splitting is being used,
-@code{"FIELDWIDTHS"} if fixed-width field splitting is being used,
-or @code{"FPAT"} if content-based field splitting is being used:
-
-@example
-if ("CSV" in PROCINFO)
- @var{CSV-based field splitting} @dots{}
-else if (PROCINFO["FS"] == "FS")
- @var{regular field splitting} @dots{}
-else if (PROCINFO["FS"] == "FIELDWIDTHS")
- @var{fixed-width field splitting} @dots{}
-else if (PROCINFO["FS"] == "FPAT")
- @var{content-based field splitting} @dots{}
-else
- @var{API input parser field splitting} @dots{} @ii{(advanced feature)}
-@end example
-
-This information is useful when writing a function that needs to
-temporarily change @code{FS}, @code{FIELDWIDTHS}, or @code{FPAT}, read some
records,
-and then restore the original settings (@pxref{Passwd Functions} for an
-example of such a function).
-
-@node Multiple Line
-@section Multiple-Line Records
-
-@cindex multiple-line records
-@cindex records @subentry multiline
-@cindex input @subentry multiline records
-@cindex files @subentry reading @subentry multiline records
-@cindex input, files @seeentry{input files}
-In some databases, a single line cannot conveniently hold all the
-information in one entry. In such cases, you can use multiline
-records. The first step in doing this is to choose your data format.
-
-@cindex record separators @subentry with multiline records
-One technique is to use an unusual character or string to separate
-records. For example, you could use the formfeed character (written
-@samp{\f} in @command{awk}, as in C) to separate them, making each record
-a page of the file. To do this, just set the variable @code{RS} to
-@code{"\f"} (a string containing the formfeed character). Any
-other character could equally well be used, as long as it won't be part
-of the data in a record.
-
-@cindex @code{RS} variable @subentry multiline records and
-Another technique is to have blank lines separate records. By a special
-dispensation, an empty string as the value of @code{RS} indicates that
-records are separated by one or more blank lines. When @code{RS} is set
-to the empty string, each record always ends at the first blank line
-encountered. The next record doesn't start until the first nonblank
-line that follows. No matter how many blank lines appear in a row, they
-all act as one record separator.
-(Blank lines must be completely empty; lines that contain only
-whitespace do not count.)
-
-@cindex leftmost longest match
-@cindex matching @subentry leftmost longest
-You can achieve the same effect as @samp{RS = ""} by assigning the
-string @code{"\n\n+"} to @code{RS}. This regexp matches the newline
-at the end of the record and one or more blank lines after the record.
-In addition, a regular expression always matches the longest possible
-sequence when there is a choice
-(@pxref{Leftmost Longest}).
-So, the next record doesn't start until
-the first nonblank line that follows---no matter how many blank lines
-appear in a row, they are considered one record separator.
-
-@cindex dark corner @subentry multiline records
-However, there is an important difference between @samp{RS = ""} and
-@samp{RS = "\n\n+"}. In the first case, leading newlines in the input
-@value{DF} are ignored, and if a file ends without extra blank lines
-after the last record, the final newline is removed from the record.
-In the second case, this special processing is not done.
-@value{DARKCORNER}
-
-@cindex field separator @subentry in multiline records
-@cindex @code{FS} variable @subentry in multiline records
-Now that the input is separated into records, the second step is to
-separate the fields in the records. One way to do this is to divide each
-of the lines into fields in the normal manner. This happens by default
-as the result of a special feature. When @code{RS} is set to the empty
-string @emph{and} @code{FS} is set to a single character,
-the newline character @emph{always} acts as a field separator.
-This is in addition to whatever field separations result from
-@code{FS}.
-
-@quotation NOTE
-When @code{FS} is the null string (@code{""})
-or a regexp, this special feature of @code{RS} does not apply.
-It does apply to the default field separator of a single space:
-@samp{FS = @w{" "}}.
-
-Note that language in the POSIX specification implies that
-this special feature should apply when @code{FS} is a regexp.
-However, Unix @command{awk} has never behaved that way, nor has
-@command{gawk}. This is essentially a bug in POSIX.
-@c Noted as of 4/2019; working to get the standard fixed.
-@end quotation
-
-The original motivation for this special exception was probably to provide
-useful behavior in the default case (i.e., @code{FS} is equal
-to @w{@code{" "}}). This feature can be a problem if you really don't
-want the newline character to separate fields, because there is no way to
-prevent it. However, you can work around this by using the @code{split()}
-function to break up the record manually
-(@pxref{String Functions}).
-If you have a single-character field separator, you can work around
-the special feature in a different way, by making @code{FS} into a
-regexp for that single character. For example, if the field
-separator is a percent character, instead of
-@samp{FS = "%"}, use @samp{FS = "[%]"}.
-
-Another way to separate fields is to
-put each field on a separate line: to do this, just set the
-variable @code{FS} to the string @code{"\n"}.
-(This single-character separator matches a single newline.)
-A practical example of a @value{DF} organized this way might be a mailing
-list, where blank lines separate the entries. Consider a mailing
-list in a file named @file{addresses}, which looks like this:
-
-@example
-Jane Doe
-123 Main Street
-Anywhere, SE 12345-6789
-
-John Smith
-456 Tree-lined Avenue
-Smallville, MW 98765-4321
-@dots{}
-@end example
-
-@noindent
-A simple program to process this file is as follows:
-
-@example
-# addrs.awk --- simple mailing list program
-
-# Records are separated by blank lines.
-# Each line is one field.
-BEGIN @{ RS = "" ; FS = "\n" @}
-
-@{
- print "Name is:", $1
- print "Address is:", $2
- print "City and State are:", $3
- print ""
-@}
-@end example
-
-Running the program produces the following output:
-
-@example
-$ @kbd{awk -f addrs.awk addresses}
-@print{} Name is: Jane Doe
-@print{} Address is: 123 Main Street
-@print{} City and State are: Anywhere, SE 12345-6789
-@print{}
-@print{} Name is: John Smith
-@print{} Address is: 456 Tree-lined Avenue
-@print{} City and State are: Smallville, MW 98765-4321
-@print{}
-@dots{}
-@end example
-
-@xref{Labels Program} for a more realistic program dealing with
-address lists. The following list summarizes how records are split,
-based on the value of
-@ifinfo
-@code{RS}.
-(@samp{==} means ``is equal to.'')
-@end ifinfo
-@ifnotinfo
-@code{RS}:
-@end ifnotinfo
-
-@table @code
-@item RS == "\n"
-Records are separated by the newline character (@samp{\n}). In effect,
-every line in the @value{DF} is a separate record, including blank lines.
-This is the default.
-
-@item RS == @var{any single character}
-Records are separated by each occurrence of the character. Multiple
-successive occurrences delimit empty records.
-
-@item RS == ""
-Records are separated by runs of blank lines.
-When @code{FS} is a single character, then
-the newline character
-always serves as a field separator, in addition to whatever value
-@code{FS} may have. Leading and trailing newlines in a file are ignored.
-
-@item RS == @var{regexp}
-Records are separated by occurrences of characters that match @var{regexp}.
-Leading and trailing matches of @var{regexp} delimit empty records.
-(This is a @command{gawk} extension; it is not specified by the
-POSIX standard.)
-@end table
-
-@cindex @command{gawk} @subentry @code{RT} variable in
-@cindex @code{RT} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{RS}/@code{RT} variables
-If not in compatibility mode (@pxref{Options}), @command{gawk} sets
-@code{RT} to the input text that matched the value specified by @code{RS}.
-But if the input file ended without any text that matches @code{RS},
-then @command{gawk} sets @code{RT} to the null string.
-
-@node Getline
-@section Explicit Input with @code{getline}
-
-@cindex @code{getline} command @subentry explicit input with
-@cindex input @subentry explicit
-So far we have been getting our input data from @command{awk}'s main
-input stream---either the standard input (usually your keyboard, sometimes
-the output from another program) or the
-files specified on the command line. The @command{awk} language has a
-special built-in command called @code{getline} that
-can be used to read input under your explicit control.
-
-The @code{getline} command is used in several different ways and should
-@emph{not} be used by beginners.
-The examples that follow the explanation of the @code{getline} command
-include material that has not been covered yet. Therefore, come back
-and study the @code{getline} command @emph{after} you have reviewed the
-rest of
-@ifinfo
-this @value{DOCUMENT}
-@end ifinfo
-@ifhtml
-this @value{DOCUMENT}
-@end ifhtml
-@ifnotinfo
-@ifnothtml
-Parts I and II
-@end ifnothtml
-@end ifnotinfo
-and have a good knowledge of how @command{awk} works.
-
-@cindex @command{gawk} @subentry @code{ERRNO} variable in
-@cindex @code{ERRNO} variable @subentry with @command{getline} command
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{getline} command
-@cindex @code{getline} command @subentry return values
-@cindex @option{--sandbox} option @subentry input redirection with
@code{getline}
-
-The @code{getline} command returns 1 if it finds a record and 0 if
-it encounters the end of the file. If there is some error in getting
-a record, such as a file that cannot be opened, then @code{getline}
-returns @minus{}1. In this case, @command{gawk} sets the variable
-@code{ERRNO} to a string describing the error that occurred.
-
-If @code{ERRNO} indicates that the I/O operation may be
-retried, and @code{PROCINFO["@var{input}", "RETRY"]} is set,
-then @code{getline} returns @minus{}2
-instead of @minus{}1, and further calls to @code{getline}
-may be attempted. @xref{Retrying Input} for further information about
-this feature.
-
-In the following examples, @var{command} stands for a string value that
-represents a shell command.
-
-@quotation NOTE
-When @option{--sandbox} is specified (@pxref{Options}),
-reading lines from files, pipes, and coprocesses is disabled.
-@end quotation
-
-@menu
-* Plain Getline:: Using @code{getline} with no arguments.
-* Getline/Variable:: Using @code{getline} into a variable.
-* Getline/File:: Using @code{getline} from a file.
-* Getline/Variable/File:: Using @code{getline} into a variable from a
- file.
-* Getline/Pipe:: Using @code{getline} from a pipe.
-* Getline/Variable/Pipe:: Using @code{getline} into a variable from a
- pipe.
-* Getline/Coprocess:: Using @code{getline} from a coprocess.
-* Getline/Variable/Coprocess:: Using @code{getline} into a variable from a
- coprocess.
-* Getline Notes:: Important things to know about @code{getline}.
-* Getline Summary:: Summary of @code{getline} Variants.
-@end menu
-
-@node Plain Getline
-@subsection Using @code{getline} with No Arguments
-
-The @code{getline} command can be used without arguments to read input
-from the current input file. All it does in this case is read the next
-input record and split it up into fields. This is useful if you've
-finished processing the current record, but want to do some special
-processing on the next record @emph{right now}. For example:
-
-@c 6/2019: Thanks to Mark Krauze <daburashka@ya.ru> for suggested
-@c improvements (the inner while loop).
-@example
-# Remove text between /* and */, inclusive
-@{
- while ((start = index($0, "/*")) != 0) @{
- out = substr($0, 1, start - 1) # leading part of the string
- rest = substr($0, start + 2) # ... */ ...
- while ((end = index(rest, "*/")) == 0) @{ # is */ in trailing part?
- # get more text
- if (getline <= 0) @{
- print("unexpected EOF or error:", ERRNO) > "/dev/stderr"
- exit
- @}
- # build up the line using string concatenation
- rest = rest $0
- @}
- rest = substr(rest, end + 2) # remove comment
- # build up the output line using string concatenation
- $0 = out rest
- @}
- print $0
-@}
-@end example
-
-This @command{awk} program deletes C-style comments (@samp{/* @dots{}
-*/}) from the input.
-It uses a number of features we haven't covered yet, including
-string concatenation
-(@pxref{Concatenation})
-and the @code{index()} and @code{substr()} built-in
-functions
-(@pxref{String Functions}).
-By replacing the @samp{print $0} with other
-statements, you could perform more complicated processing on the
-decommented input, such as searching for matches of a regular
-expression.
-
-Here is some sample input:
-
-@example
-mon/*comment*/key
-rab/*commen
-t*/bit
-horse /*comment*/more text
-part 1 /*comment*/part 2 /*comment*/part 3
-no comment
-@end example
-
-When run, the output is:
-
-@example
-$ @kbd{awk -f strip_comments.awk example_text}
-@print{} monkey
-@print{} rabbit
-@print{} horse more text
-@print{} part 1 part 2 part 3
-@print{} no comment
-@end example
-
-This form of the @code{getline} command sets @code{NF},
-@code{NR}, @code{FNR}, @code{RT}, and the value of @code{$0}.
-
-@quotation NOTE
-The new value of @code{$0} is used to test
-the patterns of any subsequent rules. The original value
-of @code{$0} that triggered the rule that executed @code{getline}
-is lost.
-By contrast, the @code{next} statement reads a new record
-but immediately begins processing it normally, starting with the first
-rule in the program. @xref{Next Statement}.
-@end quotation
-
-@node Getline/Variable
-@subsection Using @code{getline} into a Variable
-@cindex @code{getline} command @subentry into a variable
-@cindex variables @subentry @code{getline} command into, using
-
-You can use @samp{getline @var{var}} to read the next record from
-@command{awk}'s input into the variable @var{var}. No other processing is
-done.
-For example, suppose the next line is a comment or a special string,
-and you want to read it without triggering
-any rules. This form of @code{getline} allows you to read that line
-and store it in a variable so that the main
-read-a-line-and-check-each-rule loop of @command{awk} never sees it.
-The following example swaps every two lines of input:
-
-@example
-@group
-@{
- if ((getline tmp) > 0) @{
- print tmp
- print $0
- @} else
- print $0
-@}
-@end group
-@end example
-
-@noindent
-It takes the following list:
-
-@example
-wan
-tew
-free
-phore
-@end example
-
-@noindent
-and produces these results:
-
-@example
-tew
-wan
-phore
-free
-@end example
-
-The @code{getline} command used in this way sets only the variables
-@code{NR}, @code{FNR}, and @code{RT} (and, of course, @var{var}).
-The record is not
-split into fields, so the values of the fields (including @code{$0}) and
-the value of @code{NF} do not change.
-
-@node Getline/File
-@subsection Using @code{getline} from a File
-
-@cindex @code{getline} command @subentry from a file
-@cindex input redirection
-@cindex redirection @subentry of input
-@cindex @code{<} (left angle bracket) @subentry @code{<} operator (I/O)
-@cindex left angle bracket (@code{<}) @subentry @code{<} operator (I/O)
-@cindex operators @subentry input/output
-Use @samp{getline < @var{file}} to read the next record from @var{file}.
-Here, @var{file} is a string-valued expression that
-specifies the @value{FN}. @samp{< @var{file}} is called a @dfn{redirection}
-because it directs input to come from a different place.
-For example, the following
-program reads its input record from the file @file{secondary.input} when it
-encounters a first field with a value equal to 10 in the current input
-file:
-
-@example
-@{
- if ($1 == 10) @{
- getline < "secondary.input"
- print
- @} else
- print
-@}
-@end example
-
-Because the main input stream is not used, the values of @code{NR} and
-@code{FNR} are not changed. However, the record it reads is split into fields
in
-the normal manner, so the values of @code{$0} and the other fields are
-changed, resulting in a new value of @code{NF}.
-@code{RT} is also set.
-
-@cindex POSIX @command{awk} @subentry @code{<} operator and
-@c Thanks to Paul Eggert for initial wording here
-According to POSIX, @samp{getline < @var{expression}} is ambiguous if
-@var{expression} contains unparenthesized operators other than
-@samp{$}; for example, @samp{getline < dir "/" file} is ambiguous
-because the concatenation operator (not discussed yet; @pxref{Concatenation})
-is not parenthesized. You should write it as @samp{getline < (dir "/" file)}
if
-you want your program to be portable to all @command{awk} implementations.
-
-@node Getline/Variable/File
-@subsection Using @code{getline} into a Variable from a File
-@cindex variables @subentry @code{getline} command into, using
-
-Use @samp{getline @var{var} < @var{file}} to read input
-from the file
-@var{file}, and put it in the variable @var{var}. As earlier, @var{file}
-is a string-valued expression that specifies the file from which to read.
-
-In this version of @code{getline}, none of the predefined variables are
-changed and the record is not split into fields. The only variable
-changed is @var{var}.@footnote{This is not quite true. @code{RT} could
-be changed if @code{RS} is a regular expression.}
-For example, the following program copies all the input files to the
-output, except for records that say @w{@samp{@@include @var{filename}}}.
-Such a record is replaced by the contents of the file
-@var{filename}:
-
-@example
-@{
- if (NF == 2 && $1 == "@@include") @{
- while ((getline line < $2) > 0)
- print line
- close($2)
- @} else
- print
-@}
-@end example
-
-Note here how the name of the extra input file is not built into
-the program; it is taken directly from the data, specifically from the second
field on
-the @code{@@include} line.
-
-The @code{close()} function is called to ensure that if two identical
-@code{@@include} lines appear in the input, the entire specified file is
-included twice.
-@xref{Close Files And Pipes}.
-
-One deficiency of this program is that it does not process nested
-@code{@@include} statements
-(i.e., @code{@@include} statements in included files)
-the way a true macro preprocessor would.
-@xref{Igawk Program} for a program
-that does handle nested @code{@@include} statements.
-
-@node Getline/Pipe
-@subsection Using @code{getline} from a Pipe
-
-@c From private email, dated October 2, 1988. Used by permission, March 2013.
-@cindex Kernighan, Brian @subentry quotes
-@quotation
-@i{Omniscience has much to recommend it.
-Failing that, attention to details would be useful.}
-@author Brian Kernighan
-@end quotation
-
-@cindex @code{|} (vertical bar) @subentry @code{|} operator (I/O)
-@cindex vertical bar (@code{|}) @subentry @code{|} operator (I/O)
-@cindex input pipeline
-@cindex pipe @subentry input
-@cindex operators @subentry input/output
-The output of a command can also be piped into @code{getline}, using
-@samp{@var{command} | getline}. In
-this case, the string @var{command} is run as a shell command and its output
-is piped into @command{awk} to be used as input. This form of @code{getline}
-reads one record at a time from the pipe.
-For example, the following program copies its input to its output, except for
-lines that begin with @samp{@@execute}, which are replaced by the output
-produced by running the rest of the line as a shell command:
-
-@example
-@group
-@{
- if ($1 == "@@execute") @{
- tmp = substr($0, 10) # Remove "@@execute"
- while ((tmp | getline) > 0)
- print
- close(tmp)
- @} else
- print
-@}
-@end group
-@end example
-
-@noindent
-The @code{close()} function is called to ensure that if two identical
-@samp{@@execute} lines appear in the input, the command is run for
-each one.
-@ifnottex
-@ifnotdocbook
-@xref{Close Files And Pipes}.
-@end ifnotdocbook
-@end ifnottex
-@c This example is unrealistic, since you could just use system
-Given the input:
-
-@example
-foo
-bar
-baz
-@@execute who
-bletch
-@end example
-
-@noindent
-the program might produce:
-
-@cindex Robbins @subentry Bill
-@cindex Robbins @subentry Miriam
-@cindex Robbins @subentry Arnold
-@example
-foo
-bar
-baz
-arnold ttyv0 Jul 13 14:22
-miriam ttyp0 Jul 13 14:23 (murphy:0)
-bill ttyp1 Jul 13 14:23 (murphy:0)
-bletch
-@end example
-
-@noindent
-Notice that this program ran the command @command{who} and printed the result.
-(If you try this program yourself, you will of course get different results,
-depending upon who is logged in on your system.)
-
-This variation of @code{getline} splits the record into fields, sets the
-value of @code{NF}, and recomputes the value of @code{$0}. The values of
-@code{NR} and @code{FNR} are not changed.
-@code{RT} is set.
-
-@cindex POSIX @command{awk} @subentry @code{|} I/O operator and
-@c Thanks to Paul Eggert for initial wording here
-According to POSIX, @samp{@var{expression} | getline} is ambiguous if
-@var{expression} contains unparenthesized operators other than
-@samp{$}---for example, @samp{@w{"echo "} "date" | getline} is ambiguous
-because the concatenation operator is not parenthesized. You should
-write it as @samp{(@w{"echo "} "date") | getline} if you want your program
-to be portable to all @command{awk} implementations.
-
-@cindex Brian Kernighan's @command{awk}
-@cindex @command{mawk} utility
-@quotation NOTE
-Unfortunately, @command{gawk} has not been consistent in its treatment
-of a construct like @samp{@w{"echo "} "date" | getline}.
-Most versions, including the current version, treat it as
-@samp{@w{("echo "} "date") | getline}.
-(This is also how BWK @command{awk} behaves.)
-Some versions instead treat it as
-@samp{@w{"echo "} ("date" | getline)}.
-(This is how @command{mawk} behaves.)
-In short, @emph{always} use explicit parentheses, and then you won't
-have to worry.
-@end quotation
-
-@node Getline/Variable/Pipe
-@subsection Using @code{getline} into a Variable from a Pipe
-@cindex variables @subentry @code{getline} command into, using
-
-When you use @samp{@var{command} | getline @var{var}}, the
-output of @var{command} is sent through a pipe to
-@code{getline} and into the variable @var{var}. For example, the
-following program reads the current date and time into the variable
-@code{current_time}, using the @command{date} utility, and then
-prints it:
-
-@example
-BEGIN @{
- "date" | getline current_time
- close("date")
- print "Report printed on " current_time
-@}
-@end example
-
-In this version of @code{getline}, none of the predefined variables are
-changed and the record is not split into fields. However, @code{RT} is set.
-
-@ifinfo
-@c Thanks to Paul Eggert for initial wording here
-According to POSIX, @samp{@var{expression} | getline @var{var}} is ambiguous if
-@var{expression} contains unparenthesized operators other than
-@samp{$}; for example, @samp{@w{"echo "} "date" | getline @var{var}} is
ambiguous
-because the concatenation operator is not parenthesized. You should
-write it as @samp{(@w{"echo "} "date") | getline @var{var}} if you want your
-program to be portable to other @command{awk} implementations.
-@end ifinfo
-
-@node Getline/Coprocess
-@subsection Using @code{getline} from a Coprocess
-@cindex coprocesses @subentry @code{getline} from
-@cindex @code{getline} command @subentry coprocesses, using from
-@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
-@cindex vertical bar (@code{|}) @subentry @code{|&} operator (I/O)
-@cindex operators @subentry input/output
-@cindex differences in @command{awk} and @command{gawk} @subentry input/output
operators
-
-Reading input into @code{getline} from a pipe is a one-way operation.
-The command that is started with @samp{@var{command} | getline} only
-sends data @emph{to} your @command{awk} program.
-
-On occasion, you might want to send data to another program
-for processing and then read the results back.
-@command{gawk} allows you to start a @dfn{coprocess}, with which two-way
-communications are possible. This is done with the @samp{|&}
-operator.
-Typically, you write data to the coprocess first and then
-read the results back, as shown in the following:
-
-@example
-print "@var{some query}" |& "db_server"
-"db_server" |& getline
-@end example
-
-@noindent
-which sends a query to @command{db_server} and then reads the results.
-
-The values of @code{NR} and
-@code{FNR} are not changed,
-because the main input stream is not used.
-However, the record is split into fields in
-the normal manner, thus changing the values of @code{$0}, of the other fields,
-and of @code{NF} and @code{RT}.
-
-Coprocesses are an advanced feature. They are discussed here only because
-this is the @value{SECTION} on @code{getline}.
-@xref{Two-way I/O},
-where coprocesses are discussed in more detail.
-
-@node Getline/Variable/Coprocess
-@subsection Using @code{getline} into a Variable from a Coprocess
-@cindex variables @subentry @code{getline} command into, using
-
-When you use @samp{@var{command} |& getline @var{var}}, the output from
-the coprocess @var{command} is sent through a two-way pipe to @code{getline}
-and into the variable @var{var}.
-
-In this version of @code{getline}, none of the predefined variables are
-changed and the record is not split into fields. The only variable
-changed is @var{var}.
-However, @code{RT} is set.
-
-@ifinfo
-Coprocesses are an advanced feature. They are discussed here only because
-this is the @value{SECTION} on @code{getline}.
-@xref{Two-way I/O},
-where coprocesses are discussed in more detail.
-@end ifinfo
-
-@node Getline Notes
-@subsection Points to Remember About @code{getline}
-Here are some miscellaneous points about @code{getline} that
-you should bear in mind:
-
-@itemize @value{BULLET}
-@item
-When @code{getline} changes the value of @code{$0} and @code{NF},
-@command{awk} does @emph{not} automatically jump to the start of the
-program and start testing the new record against every pattern.
-However, the new record is tested against any subsequent rules.
-
-@cindex differences in @command{awk} and @command{gawk} @subentry
implementation limitations
-@cindex implementation issues, @command{gawk} @subentry limits
-@cindex @command{awk} @subentry implementations @subentry limits
-@cindex @command{gawk} @subentry implementation issues @subentry limits
-@item
-Some very old @command{awk} implementations limit the number of pipelines that
an @command{awk}
-program may have open to just one. In @command{gawk}, there is no such limit.
-You can open as many pipelines (and coprocesses) as the underlying operating
-system permits.
-
-@cindex side effects @subentry @code{FILENAME} variable
-@cindex @code{FILENAME} variable @subentry @code{getline}, setting with
-@cindex dark corner @subentry @code{FILENAME} variable
-@cindex @code{getline} command @subentry @code{FILENAME} variable and
-@cindex @code{BEGIN} pattern @subentry @code{getline} and
-@item
-An interesting side effect occurs if you use @code{getline} without a
-redirection inside a @code{BEGIN} rule. Because an unredirected @code{getline}
-reads from the command-line @value{DF}s, the first @code{getline} command
-causes @command{awk} to set the value of @code{FILENAME}. Normally,
-@code{FILENAME} does not have a value inside @code{BEGIN} rules, because you
-have not yet started to process the command-line @value{DF}s.
-@value{DARKCORNER}
-(See @ref{BEGIN/END};
-also @pxref{Auto-set}.)
-
-@item
-Using @code{FILENAME} with @code{getline}
-(@samp{getline < FILENAME})
-is likely to be a source of
-confusion. @command{awk} opens a separate input stream from the
-current input file. However, by not using a variable, @code{$0}
-and @code{NF} are still updated. If you're doing this, it's
-probably by accident, and you should reconsider what it is you're
-trying to accomplish.
-
-@item
-@ifdocbook
-The next @value{SECTION}
-@end ifdocbook
-@ifnotdocbook
-@ref{Getline Summary},
-@end ifnotdocbook
-presents a table summarizing the
-@code{getline} variants and which variables they can affect.
-It is worth noting that those variants that do not use redirection
-can cause @code{FILENAME} to be updated if they cause
-@command{awk} to start reading a new input file.
-
-@item
-@cindex Moore, Duncan
-If the variable being assigned is an expression with side effects,
-different versions of @command{awk} behave differently upon encountering
-end-of-file. Some versions don't evaluate the expression; many versions
-(including @command{gawk}) do. Here is an example, courtesy of Duncan Moore:
-
-@ignore
-Date: Sun, 01 Apr 2012 11:49:33 +0100
-From: Duncan Moore <duncan.moore@@gmx.com>
-@end ignore
-
-@example
-BEGIN @{
- system("echo 1 > f")
- while ((getline a[++c] < "f") > 0) @{ @}
- print c
-@}
-@end example
-
-@noindent
-Here, the side effect is the @samp{++c}. Is @code{c} incremented if
-end-of-file is encountered before the element in @code{a} is assigned?
-
-@command{gawk} treats @code{getline} like a function call, and evaluates
-the expression @samp{a[++c]} before attempting to read from @file{f}.
-However, some versions of @command{awk} only evaluate the expression once they
-know that there is a string value to be assigned.
-@end itemize
-
-@node Getline Summary
-@subsection Summary of @code{getline} Variants
-@cindex @code{getline} command @subentry variants
-
-@ref{table-getline-variants}
-summarizes the eight variants of @code{getline},
-listing which predefined variables are set by each one,
-and whether the variant is standard or a @command{gawk} extension.
-Note: for each variant, @command{gawk} sets the @code{RT} predefined variable.
-
-@float Table,table-getline-variants
-@caption{@code{getline} variants and what they set}
-@multitable @columnfractions .33 .38 .27
-@headitem Variant @tab Effect @tab @command{awk} / @command{gawk}
-@item @code{getline} @tab Sets @code{$0}, @code{NF}, @code{FNR}, @code{NR},
and @code{RT} @tab @command{awk}
-@item @code{getline} @var{var} @tab Sets @var{var}, @code{FNR}, @code{NR}, and
@code{RT} @tab @command{awk}
-@item @code{getline <} @var{file} @tab Sets @code{$0}, @code{NF}, and
@code{RT} @tab @command{awk}
-@item @code{getline @var{var} < @var{file}} @tab Sets @var{var} and @code{RT}
@tab @command{awk}
-@item @var{command} @code{| getline} @tab Sets @code{$0}, @code{NF}, and
@code{RT} @tab @command{awk}
-@item @var{command} @code{| getline} @var{var} @tab Sets @var{var} and
@code{RT} @tab @command{awk}
-@item @var{command} @code{|& getline} @tab Sets @code{$0}, @code{NF}, and
@code{RT} @tab @command{gawk}
-@item @var{command} @code{|& getline} @var{var} @tab Sets @var{var} and
@code{RT} @tab @command{gawk}
-@end multitable
-@end float
-
-@node Read Timeout
-@section Reading Input with a Timeout
-@cindex timeout, reading input
-
-@cindex differences in @command{awk} and @command{gawk} @subentry read timeouts
-This @value{SECTION} describes a feature that is specific to @command{gawk}.
-
-You may specify a timeout in milliseconds for reading input from the keyboard,
-a pipe, or two-way communication, including TCP/IP sockets. This can be done
-on a per-input, per-command, or per-connection basis, by setting a special
-element in the @code{PROCINFO} array (@pxref{Auto-set}):
-
-@example
-PROCINFO["input_name", "READ_TIMEOUT"] = @var{timeout in milliseconds}
-@end example
-
-When set, this causes @command{gawk} to time out and return failure
-if no data is available to read within the specified timeout period.
-For example, a TCP client can decide to give up on receiving
-any response from the server after a certain amount of time:
-
-@example
-@group
-Service = "/inet/tcp/0/localhost/daytime"
-PROCINFO[Service, "READ_TIMEOUT"] = 100
-if ((Service |& getline) > 0)
- print $0
-else if (ERRNO != "")
- print ERRNO
-@end group
-@end example
-
-Here is how to read interactively from the user@footnote{This assumes
-that standard input is the keyboard.} without waiting
-for more than five seconds:
-
-@example
-PROCINFO["/dev/stdin", "READ_TIMEOUT"] = 5000
-while ((getline < "/dev/stdin") > 0)
- print $0
-@end example
-
-@command{gawk} terminates the read operation if input does not
-arrive after waiting for the timeout period, returns failure,
-and sets @code{ERRNO} to an appropriate string value.
-A negative or zero value for the timeout is the same as specifying
-no timeout at all.
-
-A timeout can also be set for reading from the keyboard in the implicit
-loop that reads input records and matches them against patterns,
-like so:
-
-@example
-$ @kbd{gawk 'BEGIN @{ PROCINFO["-", "READ_TIMEOUT"] = 5000 @}}
-> @kbd{@{ print "You entered: " $0 @}'}
-@kbd{gawk}
-@print{} You entered: gawk
-@end example
-
-In this case, failure to respond within five seconds results in the following
-error message:
-
-@example
-@error{} gawk: cmd. line:2: (FILENAME=- FNR=1) fatal: error reading input file
`-': Connection timed out
-@end example
-
-The timeout can be set or changed at any time, and will take effect on the
-next attempt to read from the input device. In the following example,
-we start with a timeout value of one second, and progressively
-reduce it by one-tenth of a second until we wait indefinitely
-for the input to arrive:
-
-@example
-PROCINFO[Service, "READ_TIMEOUT"] = 1000
-while ((Service |& getline) > 0) @{
- print $0
- PROCINFO[Service, "READ_TIMEOUT"] -= 100
-@}
-@end example
-
-@quotation NOTE
-You should not assume that the read operation will block
-exactly after the tenth record has been printed. It is possible that
-@command{gawk} will read and buffer more than one record's
-worth of data the first time. Because of this, changing the value
-of timeout like in the preceding example is not very useful.
-@end quotation
-
-@cindex @env{GAWK_READ_TIMEOUT} environment variable
-@cindex environment variables @subentry @env{GAWK_READ_TIMEOUT}
-If the @code{PROCINFO} element is not present and the
-@env{GAWK_READ_TIMEOUT} environment variable exists,
-@command{gawk} uses its value to initialize the timeout value.
-The exclusive use of the environment variable to specify timeout
-has the disadvantage of not being able to control it
-on a per-command or per-connection basis.
-
-@command{gawk} considers a timeout event to be an error even though
-the attempt to read from the underlying device may
-succeed in a later attempt. This is a limitation, and it also
-means that you cannot use this to multiplex input from
-two or more sources. @xref{Retrying Input} for a way to enable
-later I/O attempts to succeed.
-
-Assigning a timeout value prevents read operations from being
-blocked indefinitely. But bear in mind that there are other ways
-@command{gawk} can stall waiting for an input device to be ready.
-A network client can sometimes take a long time to establish
-a connection before it can start reading any data,
-or the attempt to open a FIFO special file for reading can be blocked
-indefinitely until some other process opens it for writing.
-
-@node Retrying Input
-@section Retrying Reads After Certain Input Errors
-@cindex retrying input
-
-@cindex differences in @command{awk} and @command{gawk} @subentry retrying
input
-This @value{SECTION} describes a feature that is specific to @command{gawk}.
-
-When @command{gawk} encounters an error while reading input, by
-default @code{getline} returns @minus{}1, and subsequent attempts to
-read from that file result in an end-of-file indication. However, you
-may optionally instruct @command{gawk} to allow I/O to be retried when
-certain errors are encountered by setting a special element in
-the @code{PROCINFO} array (@pxref{Auto-set}):
-
-@example
-PROCINFO["@var{input_name}", "RETRY"] = 1
-@end example
-
-When this element exists, @command{gawk} checks the value of the system
-(C language)
-@code{errno} variable when an I/O error occurs. If @code{errno} indicates
-a subsequent I/O attempt may succeed, @code{getline} instead returns
-@minus{}2 and
-further calls to @code{getline} may succeed. This applies to the @code{errno}
-values @code{EAGAIN}, @code{EWOULDBLOCK}, @code{EINTR}, or @code{ETIMEDOUT}.
-
-This feature is useful in conjunction with
-@code{PROCINFO["@var{input_name}", "READ_TIMEOUT"]} or situations where a file
-descriptor has been configured to behave in a non-blocking fashion.
-
-@node Command-line directories
-@section Directories on the Command Line
-@cindex differences in @command{awk} and @command{gawk} @subentry command-line
directories
-@cindex directories @subentry command-line
-@cindex command line @subentry directories on
-
-According to the POSIX standard, files named on the @command{awk}
-command line must be text files; it is a fatal error if they are not.
-Most versions of @command{awk} treat a directory on the command line as
-a fatal error.
-
-By default, @command{gawk} produces a warning for a directory on the
-command line, but otherwise ignores it. This makes it easier to use
-shell wildcards with your @command{awk} program:
-
-@example
-$ @kbd{gawk -f whizprog.awk *} @ii{Directories could kill this program}
-@end example
-
-If either of the @option{--posix}
-or @option{--traditional} options is given, then @command{gawk} reverts
-to treating a directory on the command line as a fatal error.
-
-@xref{Extension Sample Readdir} for a way to treat directories
-as usable data from an @command{awk} program.
-
-@node Input Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Input is split into records based on the value of @code{RS}.
-The possibilities are as follows:
-
-@multitable @columnfractions .25 .35 .40
-@headitem Value of @code{RS} @tab Records are split on @dots{} @tab
@command{awk} / @command{gawk}
-@item Any single character @tab That character @tab @command{awk}
-@item The empty string (@code{""}) @tab Runs of two or more newlines @tab
@command{awk}
-@item A regexp @tab Text that matches the regexp @tab @command{gawk}
-@end multitable
-
-@item
-@code{FNR} indicates how many records have been read from the current input
file;
-@code{NR} indicates how many records have been read in total.
-
-@item
-@command{gawk} sets @code{RT} to the text matched by @code{RS}.
-
-@item
-After splitting the input into records, @command{awk} further splits
-the records into individual fields, named @code{$1}, @code{$2}, and so
-on. @code{$0} is the whole record, and @code{NF} indicates how many
-fields there are. The default way to split fields is between whitespace
-characters.
-
-@item
-Fields may be referenced using a variable, as in @code{$NF}. Fields
-may also be assigned values, which causes the value of @code{$0} to be
-recomputed when it is later referenced. Assigning to a field with a number
-greater than @code{NF} creates the field and rebuilds the record, using
-@code{OFS} to separate the fields. Incrementing @code{NF} does the same
-thing. Decrementing @code{NF} throws away fields and rebuilds the record.
-
-@item
-Field splitting is more complicated than record splitting:
-
-@multitable @columnfractions .40 .40 .20
-@headitem Field separator value @tab Fields are split @dots{} @tab
@command{awk} / @command{gawk}
-@item @code{FS == " "} @tab On runs of whitespace @tab @command{awk}
-@item @code{FS == @var{any single character}} @tab On that character @tab
@command{awk}
-@item @code{FS == @var{regexp}} @tab On text matching the regexp @tab
@command{awk}
-@item @code{FS == ""} @tab Such that each individual character is a separate
field @tab @command{gawk}
-@item @code{FIELDWIDTHS == @var{list of columns}} @tab Based on character
position @tab @command{gawk}
-@item @code{FPAT == @var{regexp}} @tab On the text surrounding text matching
the regexp @tab @command{gawk}
-@end multitable
-
-@item
-Using @samp{FS = "\n"} causes the entire record to be a single field
-(assuming that newlines separate records).
-
-@item
-@code{FS} may be set from the command line using the @option{-F} option.
-This can also be done using command-line variable assignment.
-
-@item
-Use @code{PROCINFO["FS"]} to see how fields are being split.
-
-@item
-Use @code{getline} in its various forms to read additional records
-from the default input stream, from a file, or from a pipe or coprocess.
-
-@item
-Use @code{PROCINFO[@var{file}, "READ_TIMEOUT"]} to cause reads to time out
-for @var{file}.
-
-@cindex POSIX mode
-@item
-Directories on the command line are fatal for standard @command{awk};
-@command{gawk} ignores them if not in POSIX mode.
-
-@end itemize
-
-@c EXCLUDE START
-@node Input Exercises
-@section Exercises
-
-@enumerate
-@item
-Using the @code{FIELDWIDTHS} variable (@pxref{Constant Size}),
-write a program to read election data, where each record represents
-one voter's votes. Come up with a way to define which columns are
-associated with each ballot item, and print the total votes,
-including abstentions, for each item.
-
-@end enumerate
-@c EXCLUDE END
-
-@node Printing
-@chapter Printing Output
-
-@cindex printing
-@cindex output, printing @seeentry{printing}
-One of the most common programming actions is to @dfn{print}, or output,
-some or all of the input. Use the @code{print} statement
-for simple output, and the @code{printf} statement
-for fancier formatting.
-The @code{print} statement is not limited when
-computing @emph{which} values to print. However, with two exceptions,
-you cannot specify @emph{how} to print them---how many
-columns, whether to use exponential notation or not, and so on.
-(For the exceptions, @pxref{Output Separators} and
-@ref{OFMT}.)
-For printing with specifications, you need the @code{printf} statement
-(@pxref{Printf}).
-
-@cindex @code{print} statement
-@cindex @code{printf} statement
-Besides basic and formatted printing, this @value{CHAPTER}
-also covers I/O redirections to files and pipes, introduces
-the special @value{FN}s that @command{gawk} processes internally,
-and discusses the @code{close()} built-in function.
-
-@menu
-* Print:: The @code{print} statement.
-* Print Examples:: Simple examples of @code{print} statements.
-* Output Separators:: The output separators and how to change them.
-* OFMT:: Controlling Numeric Output With @code{print}.
-* Printf:: The @code{printf} statement.
-* Redirection:: How to redirect output to multiple files and
- pipes.
-* Special FD:: Special files for I/O.
-* Special Files:: File name interpretation in @command{gawk}.
- @command{gawk} allows access to inherited file
- descriptors.
-* Close Files And Pipes:: Closing Input and Output Files and Pipes.
-* Noflush:: Speeding Up Pipe Output.
-* Nonfatal:: Enabling Nonfatal Output.
-* Output Summary:: Output summary.
-* Output Exercises:: Exercises.
-@end menu
-
-@node Print
-@section The @code{print} Statement
-
-Use the @code{print} statement to produce output with simple, standardized
-formatting. You specify only the strings or numbers to print, in a
-list separated by commas. They are output, separated by single spaces,
-followed by a newline. The statement looks like this:
-
-@example
-print @var{item1}, @var{item2}, @dots{}
-@end example
-
-@noindent
-The entire list of items may be optionally enclosed in parentheses. The
-parentheses are necessary if any of the item expressions uses the @samp{>}
-relational operator; otherwise it could be confused with an output redirection
-(@pxref{Redirection}).
-
-The items to print can be constant strings or numbers, fields of the
-current record (such as @code{$1}), variables, or any @command{awk}
-expression. Numeric values are converted to strings and then printed.
-
-@cindex records @subentry printing
-@cindex lines @subentry blank, printing
-@cindex text, printing
-The simple statement @samp{print} with no items is equivalent to
-@samp{print $0}: it prints the entire current record. To print a blank
-line, use @samp{print ""}.
-To print a fixed piece of text, use a string constant, such as
-@w{@code{"Don't Panic"}}, as one item. If you forget to use the
-double-quote characters, your text is taken as an @command{awk}
-expression, and you will probably get an error. Keep in mind that a
-space is printed between any two items.
-
-Note that the @code{print} statement is a statement and not an
-expression---you can't use it in the pattern part of a
-pattern--action statement, for example.
-
-@node Print Examples
-@section @code{print} Statement Examples
-
-Each @code{print} statement makes at least one line of output. However, it
-isn't limited to only one line. If an item value is a string containing a
-newline, the newline is output along with the rest of the string. A
-single @code{print} statement can make any number of lines this way.
-
-@cindex newlines @subentry printing
-The following is an example of printing a string that contains embedded
-@ifinfo
-newlines
-(the @samp{\n} is an escape sequence, used to represent the newline
-character; @pxref{Escape Sequences}):
-@end ifinfo
-@ifhtml
-newlines
-(the @samp{\n} is an escape sequence, used to represent the newline
-character; @pxref{Escape Sequences}):
-@end ifhtml
-@ifnotinfo
-@ifnothtml
-newlines:
-@end ifnothtml
-@end ifnotinfo
-
-@example
-@group
-$ @kbd{awk 'BEGIN @{ print "line one\nline two\nline three" @}'}
-@print{} line one
-@print{} line two
-@print{} line three
-@end group
-@end example
-
-@cindex fields @subentry printing
-The next example, which is run on the @file{inventory-shipped} file,
-prints the first two fields of each input record, with a space between
-them:
-
-@example
-$ @kbd{awk '@{ print $1, $2 @}' inventory-shipped}
-@print{} Jan 13
-@print{} Feb 15
-@print{} Mar 15
-@dots{}
-@end example
-
-@cindex @code{print} statement @subentry commas, omitting
-@cindex troubleshooting @subentry @code{print} statement, omitting commas
-A common mistake in using the @code{print} statement is to omit the comma
-between two items. This often has the effect of making the items run
-together in the output, with no space. The reason for this is that
-juxtaposing two string expressions in @command{awk} means to concatenate
-them. Here is the same program, without the comma:
-
-@example
-$ @kbd{awk '@{ print $1 $2 @}' inventory-shipped}
-@print{} Jan13
-@print{} Feb15
-@print{} Mar15
-@dots{}
-@end example
-
-@cindex @code{BEGIN} pattern @subentry headings, adding
-To someone unfamiliar with the @file{inventory-shipped} file, neither
-example's output makes much sense. A heading line at the beginning
-would make it clearer. Let's add some headings to our table of months
-(@code{$1}) and green crates shipped (@code{$2}). We do this using
-a @code{BEGIN} rule (@pxref{BEGIN/END}) so that the headings are only
-printed once:
-
-@example
-awk 'BEGIN @{ print "Month Crates"
- print "----- ------" @}
- @{ print $1, $2 @}' inventory-shipped
-@end example
-
-@noindent
-When run, the program prints the following:
-
-@example
-Month Crates
------ ------
-Jan 13
-Feb 15
-Mar 15
-@dots{}
-@end example
-
-@noindent
-The only problem, however, is that the headings and the table data
-don't line up! We can fix this by printing some spaces between the
-two fields:
-
-@example
-@group
-awk 'BEGIN @{ print "Month Crates"
- print "----- ------" @}
- @{ print $1, " ", $2 @}' inventory-shipped
-@end group
-@end example
-
-@cindex @code{printf} statement @subentry columns, aligning
-@cindex columns @subentry aligning
-Lining up columns this way can get pretty
-complicated when there are many columns to fix. Counting spaces for two
-or three columns is simple, but any more than this can take up
-a lot of time. This is why the @code{printf} statement was
-created (@pxref{Printf});
-one of its specialties is lining up columns of data.
-
-@cindex line continuations @subentry in @code{print} statement
-@cindex @code{print} statement @subentry line continuations and
-@quotation NOTE
-You can continue either a @code{print} or
-@code{printf} statement simply by putting a newline after any comma
-(@pxref{Statements/Lines}).
-@end quotation
-
-@node Output Separators
-@section Output Separators
-
-@cindex @code{OFS} variable
-As mentioned previously, a @code{print} statement contains a list
-of items separated by commas. In the output, the items are normally
-separated by single spaces. However, this doesn't need to be the case;
-a single space is simply the default. Any string of
-characters may be used as the @dfn{output field separator} by setting the
-predefined variable @code{OFS}. The initial value of this variable
-is the string @w{@code{" "}} (i.e., a single space).
-
-The output from an entire @code{print} statement is called an @dfn{output
-record}. Each @code{print} statement outputs one output record, and
-then outputs a string called the @dfn{output record separator} (or
-@code{ORS}). The initial value of @code{ORS} is the string @code{"\n"}
-(i.e., a newline character). Thus, each @code{print} statement normally
-makes a separate line.
-
-@cindex output @subentry records
-@cindex output record separator @seeentry{@code{ORS} variable}
-@cindex @code{ORS} variable
-@cindex @code{BEGIN} pattern @subentry @code{OFS}/@code{ORS} variables,
assigning values to
-In order to change how output fields and records are separated, assign
-new values to the variables @code{OFS} and @code{ORS}. The usual
-place to do this is in the @code{BEGIN} rule
-(@pxref{BEGIN/END}), so
-that it happens before any input is processed. It can also be done
-with assignments on the command line, before the names of the input
-files, or using the @option{-v} command-line option
-(@pxref{Options}).
-The following example prints the first and second fields of each input
-record, separated by a semicolon, with a blank line added after each
-newline:
-
-
-@example
-$ @kbd{awk 'BEGIN @{ OFS = ";"; ORS = "\n\n" @}}
-> @kbd{@{ print $1, $2 @}' mail-list}
-@print{} Amelia;555-5553
-@print{}
-@print{} Anthony;555-3412
-@print{}
-@print{} Becky;555-7685
-@print{}
-@print{} Bill;555-1675
-@print{}
-@print{} Broderick;555-0542
-@print{}
-@print{} Camilla;555-2912
-@print{}
-@print{} Fabius;555-1234
-@print{}
-@print{} Julie;555-6699
-@print{}
-@print{} Martin;555-6480
-@print{}
-@print{} Samuel;555-3430
-@print{}
-@print{} Jean-Paul;555-2127
-@print{}
-@end example
-
-If the value of @code{ORS} does not contain a newline, the program's output
-runs together on a single line.
-
-@node OFMT
-@section Controlling Numeric Output with @code{print}
-@cindex numeric @subentry output format
-@cindex formats, numeric output
-When printing numeric values with the @code{print} statement,
-@command{awk} internally converts each number to a string of characters
-and prints that string. @command{awk} uses the @code{sprintf()} function
-to do this conversion
-(@pxref{String Functions}).
-For now, it suffices to say that the @code{sprintf()}
-function accepts a @dfn{format specification} that tells it how to format
-numbers (or strings), and that there are a number of different ways in which
-numbers can be formatted. The different format specifications are discussed
-more fully in
-@ref{Control Letters}.
-
-@cindexawkfunc{sprintf}
-@cindex @code{OFMT} variable
-@cindex output @subentry format specifier, @code{OFMT}
-The predefined variable @code{OFMT} contains the format specification
-that @code{print} uses with @code{sprintf()} when it wants to convert a
-number to a string for printing.
-The default value of @code{OFMT} is @code{"%.6g"}.
-The way @code{print} prints numbers can be changed
-by supplying a different format specification
-for the value of @code{OFMT}, as shown in the following example:
-
-@example
-$ @kbd{awk 'BEGIN @{}
-> @kbd{OFMT = "%.0f" # print numbers as integers (rounds)}
-> @kbd{print 17.23, 17.54 @}'}
-@print{} 17 18
-@end example
-
-More detail on how @command{awk} converts numeric values into
-strings is provided in @ref{Strings And Numbers}. In particular, for
-@code{print}, @command{awk} uses the value of @code{OFMT} instead of
-that of @code{CONVFMT}, but otherwise behaves exactly the same
-as described in that @value{SECTION}.
-
-@noindent
-@cindex dark corner @subentry @code{OFMT} variable
-@cindex POSIX @command{awk} @subentry @code{OFMT} variable and
-@cindex @code{OFMT} variable @subentry POSIX @command{awk} and
-According to the POSIX standard, @command{awk}'s behavior is undefined
-if @code{OFMT} contains anything but a floating-point conversion specification.
-@value{DARKCORNER}
-
-@node Printf
-@section Using @code{printf} Statements for Fancier Printing
-
-@cindex @code{printf} statement
-@cindex output @subentry formatted
-@cindex formatting @subentry output
-For more precise control over the output format than what is
-provided by @code{print}, use @code{printf}.
-With @code{printf} you can
-specify the width to use for each item, as well as various
-formatting choices for numbers (such as what output base to use, whether to
-print an exponent, whether to print a sign, and how many digits to print
-after the decimal point).
-
-@menu
-* Basic Printf:: Syntax of the @code{printf} statement.
-* Control Letters:: Format-control letters.
-* Format Modifiers:: Format-specification modifiers.
-* Printf Examples:: Several examples.
-@end menu
-
-@node Basic Printf
-@subsection Introduction to the @code{printf} Statement
-
-@cindex @code{printf} statement @subentry syntax of
-A simple @code{printf} statement looks like this:
-
-@example
-printf @var{format}, @var{item1}, @var{item2}, @dots{}
-@end example
-
-@noindent
-As for @code{print}, the entire list of arguments may optionally be
-enclosed in parentheses. Here too, the parentheses are necessary if any
-of the item expressions uses the @samp{>} relational operator; otherwise,
-it can be confused with an output redirection (@pxref{Redirection}).
-
-@cindex format specifiers
-The difference between @code{printf} and @code{print} is the @var{format}
-argument. This is an expression whose value is taken as a string; it
-specifies how to output each of the other arguments. It is called the
-@dfn{format string}.
-
-The format string is very similar to that in the ISO C library function
-@code{printf()}. Most of @var{format} is text to output verbatim.
-Scattered among this text are @dfn{format specifiers}---one per item.
-Each format specifier says to output the next item in the argument list
-at that place in the format.
-
-The @code{printf} statement does not automatically append a newline
-to its output. It outputs only what the format string specifies.
-So if a newline is needed, you must include one in the format string.
-The output separator variables @code{OFS} and @code{ORS} have no effect
-on @code{printf} statements. For example:
-
-@example
-@group
-$ @kbd{awk 'BEGIN @{}
-> @kbd{ORS = "\nOUCH!\n"; OFS = "+"}
-> @kbd{msg = "Don\47t Panic!"}
-> @kbd{printf "%s\n", msg}
-> @kbd{@}'}
-@print{} Don't Panic!
-@end group
-@end example
-
-@noindent
-Here, neither the @samp{+} nor the @samp{OUCH!} appears in
-the output message.
-
-@node Control Letters
-@subsection Format-Control Letters
-@cindex @code{printf} statement @subentry format-control characters
-@cindex format specifiers @subentry @code{printf} statement
-
-A format specifier starts with the character @samp{%} and ends with
-a @dfn{format-control letter}---it tells the @code{printf} statement
-how to output one item. The format-control letter specifies what @emph{kind}
-of value to print. The rest of the format specifier is made up of
-optional @dfn{modifiers} that control @emph{how} to print the value, such as
-the field width. Here is a list of the format-control letters:
-
-@c @asis for docbook to come out right
-@table @asis
-@item @code{%a}, @code{%A}
-A floating point number of the form
-[@code{-}]@code{0x@var{h}.@var{hhhh}p+-@var{dd}}
-(C99 hexadecimal floating point format).
-For @code{%A},
-uppercase letters are used instead of lowercase ones.
-
-@quotation NOTE
-The current POSIX standard requires support for @code{%a} and @code{%A} in
-@command{awk}. As far as we know, besides @command{gawk}, the only other
-version of @command{awk} that actually implements it is BWK @command{awk}.
-It's use is thus highly nonportable!
-
-Furthermore, these formats are not available on any system where the
-underlying C library @code{printf()} function does not support them. As
-of this writing, among current systems, only OpenVMS is known to not
-support them.
-@end quotation
-
-@item @code{%c}
-Print a number as a character; thus, @samp{printf "%c",
-65} outputs the letter @samp{A}. The output for a string value is
-the first character of the string.
-
-@cindex dark corner @subentry format-control characters
-@cindex @command{gawk} @subentry format-control characters
-@quotation NOTE
-The POSIX standard says the first character of a string is printed.
-In locales with multibyte characters, @command{gawk} attempts to
-convert the leading bytes of the string into a valid wide character
-and then to print the multibyte encoding of that character.
-Similarly, when printing a numeric value, @command{gawk} allows the
-value to be within the numeric range of values that can be held
-in a wide character.
-If the conversion to multibyte encoding fails, @command{gawk}
-uses the low eight bits of the value as the character to print.
-
-Other @command{awk} versions generally restrict themselves to printing
-the first byte of a string or to numeric values within the range of
-a single byte (0--255).
-@value{DARKCORNER}
-@end quotation
-
-
-@item @code{%d}, @code{%i}
-Print a decimal integer.
-The two control letters are equivalent.
-(The @samp{%i} specification is for compatibility with ISO C.)
-
-@item @code{%e}, @code{%E}
-Print a number in scientific (exponential) notation.
-For example:
-
-@example
-printf "%4.3e\n", 1950
-@end example
-
-@noindent
-prints @samp{1.950e+03}, with a total of four significant figures, three of
-which follow the decimal point.
-(The @samp{4.3} represents two modifiers,
-discussed in the next @value{SUBSECTION}.)
-@samp{%E} uses @samp{E} instead of @samp{e} in the output.
-
-@item @code{%f}
-Print a number in floating-point notation.
-For example:
-
-@example
-printf "%4.3f", 1950
-@end example
-
-@noindent
-prints @samp{1950.000}, with a minimum of four significant figures, three of
-which follow the decimal point.
-(The @samp{4.3} represents two modifiers,
-discussed in the next @value{SUBSECTION}.)
-
-On systems supporting IEEE 754 floating-point format, values
-representing negative
-infinity are formatted as
-@samp{-inf} or @samp{-infinity},
-and positive infinity as
-@samp{inf} or @samp{infinity}.
-The special ``not a number'' value formats as @samp{-nan} or @samp{nan}
-(@pxref{Strange values}).
-
-@item @code{%F}
-Like @samp{%f}, but the infinity and ``not a number'' values are spelled
-using uppercase letters.
-
-The @samp{%F} format is a POSIX extension to ISO C; not all systems
-support it. On those that don't, @command{gawk} uses @samp{%f} instead.
-
-@item @code{%g}, @code{%G}
-Print a number in either scientific notation or in floating-point
-notation, whichever uses fewer characters; if the result is printed in
-scientific notation, @samp{%G} uses @samp{E} instead of @samp{e}.
-
-@item @code{%o}
-Print an unsigned octal integer
-(@pxref{Nondecimal-numbers}).
-
-@item @code{%s}
-Print a string.
-
-@item @code{%u}
-Print an unsigned decimal integer.
-(This format is of marginal use, because all numbers in @command{awk}
-are floating point; it is provided primarily for compatibility with C.)
-
-@item @code{%x}, @code{%X}
-Print an unsigned hexadecimal integer;
-@samp{%X} uses the letters @samp{A} through @samp{F}
-instead of @samp{a} through @samp{f}
-(@pxref{Nondecimal-numbers}).
-
-@item @code{%%}
-Print a single @samp{%}.
-This does not consume an
-argument and it ignores any modifiers.
-@end table
-
-@cindex dark corner @subentry format-control characters
-@cindex @command{gawk} @subentry format-control characters
-@quotation NOTE
-When using the integer format-control letters for values that are
-outside the range of the widest C integer type, @command{gawk} switches to
-the @samp{%g} format specifier. If @option{--lint} is provided on the
-command line (@pxref{Options}), @command{gawk}
-warns about this. Other versions of @command{awk} may print invalid
-values or do something else entirely.
-@value{DARKCORNER}
-@end quotation
-
-@quotation NOTE
-The IEEE 754 standard for floating-point arithmetic allows for special
-values that represent ``infinity'' (positive and negative) and values
-that are ``not a number'' (NaN).
-
-Input and output of these values occurs as text strings. This is
-somewhat problematic for the @command{awk} language, which predates
-the IEEE standard. Further details are provided in
-@ref{POSIX Floating Point Problems}; please see there.
-@end quotation
-
-@node Format Modifiers
-@subsection Modifiers for @code{printf} Formats
-
-@cindex @code{printf} statement @subentry modifiers
-@cindex modifiers, in format specifiers
-A format specification can also include @dfn{modifiers} that can control
-how much of the item's value is printed, as well as how much space it gets.
-The modifiers come between the @samp{%} and the format-control letter.
-We use the bullet symbol ``@bullet{}'' in the following examples to
-represent
-spaces in the output. Here are the possible modifiers, in the order in
-which they may appear:
-
-@table @asis
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{print}/@code{printf} statements
-@cindex @code{printf} statement @subentry positional specifiers
-@c the code{} does NOT start a secondary
-@cindex positional specifiers, @code{printf} statement
-@item @code{@var{N}$}
-An integer constant followed by a @samp{$} is a @dfn{positional specifier}.
-Normally, format specifications are applied to arguments in the order
-given in the format string. With a positional specifier, the format
-specification is applied to a specific argument, instead of what
-would be the next argument in the list. Positional specifiers begin
-counting with one. Thus:
-
-@example
-printf "%s %s\n", "don't", "panic"
-printf "%2$s %1$s\n", "panic", "don't"
-@end example
-
-@noindent
-prints the famous friendly message twice.
-
-At first glance, this feature doesn't seem to be of much use.
-It is in fact a @command{gawk} extension, intended for use in translating
-messages at runtime.
-@xref{Printf Ordering},
-which describes how and why to use positional specifiers.
-For now, we ignore them.
-
-@item @code{-} (Minus)
-The minus sign, used before the width modifier (see later on in
-this list),
-says to left-justify
-the argument within its specified width. Normally, the argument
-is printed right-justified in the specified width. Thus:
-
-@example
-printf "%-4s", "foo"
-@end example
-
-@noindent
-prints @samp{foo@bullet{}}.
-
-@item @var{space}
-For numeric conversions, prefix positive values with a space and
-negative values with a minus sign.
-
-@item @code{+}
-The plus sign, used before the width modifier (see later on in
-this list),
-says to always supply a sign for numeric conversions, even if the data
-to format is positive. The @samp{+} overrides the space modifier.
-
-@item @code{#}
-Use an ``alternative form'' for certain control letters.
-For @samp{%o}, supply a leading zero.
-For @samp{%x} and @samp{%X}, supply a leading @samp{0x} or @samp{0X} for
-a nonzero result.
-For @samp{%e}, @samp{%E}, @samp{%f}, and @samp{%F}, the result always
-contains a decimal point.
-For @samp{%g} and @samp{%G}, trailing zeros are not removed from the result.
-
-@item @code{0}
-A leading @samp{0} (zero) acts as a flag indicating that output should be
-padded with zeros instead of spaces.
-This applies only to the numeric output formats.
-This flag only has an effect when the field width is wider than the
-value to print.
-
-@item @code{'}
-A single quote or apostrophe character is a POSIX extension to ISO C.
-It indicates that the integer part of a floating-point value, or the
-entire part of an integer decimal value, should have a thousands-separator
-character in it. This only works in locales that support such characters.
-For example:
-
-@example
-$ @kbd{cat thousands.awk} @ii{Show source program}
-@print{} BEGIN @{ printf "%'d\n", 1234567 @}
-$ @kbd{LC_ALL=C gawk -f thousands.awk}
-@print{} 1234567 @ii{Results in} "C" @ii{locale}
-$ @kbd{LC_ALL=en_US.UTF-8 gawk -f thousands.awk}
-@print{} 1,234,567 @ii{Results in US English UTF locale}
-@end example
-
-@noindent
-For more information about locales and internationalization issues,
-see @ref{Locales}.
-
-@quotation NOTE
-The @samp{'} flag is a nice feature, but its use complicates things: it
-becomes difficult to use it in command-line programs. For information
-on appropriate quoting tricks, see @ref{Quoting}.
-@end quotation
-
-@item @var{width}
-This is a number specifying the desired minimum width of a field. Inserting
any
-number between the @samp{%} sign and the format-control character forces the
-field to expand to this width. The default way to do this is to
-pad with spaces on the left. For example:
-
-@example
-printf "%4s", "foo"
-@end example
-
-@noindent
-prints @samp{@bullet{}foo}.
-
-The value of @var{width} is a minimum width, not a maximum. If the item
-value requires more than @var{width} characters, it can be as wide as
-necessary. Thus, the following:
-
-@example
-printf "%4s", "foobar"
-@end example
-
-@noindent
-prints @samp{foobar}.
-
-Preceding the @var{width} with a minus sign causes the output to be
-padded with spaces on the right, instead of on the left.
-
-@item @code{.@var{prec}}
-A period followed by an integer constant
-specifies the precision to use when printing.
-The meaning of the precision varies by control letter:
-
-@table @asis
-@item @code{%d}, @code{%i}, @code{%o}, @code{%u}, @code{%x}, @code{%X}
-Minimum number of digits to print.
-
-@item @code{%e}, @code{%E}, @code{%f}, @code{%F}
-Number of digits to the right of the decimal point.
-
-@item @code{%g}, @code{%G}
-Maximum number of significant digits.
-
-@item @code{%s}
-Maximum number of characters from the string that should print.
-@end table
-
-Thus, the following:
-
-@example
-printf "%.4s", "foobar"
-@end example
-
-@noindent
-prints @samp{foob}.
-@end table
-
-The C library @code{printf}'s dynamic @var{width} and @var{prec}
-capability (e.g., @code{"%*.*s"}) is supported. Instead of
-supplying explicit @var{width} and/or @var{prec} values in the format
-string, they are passed in the argument list. For example:
-
-@example
-w = 5
-p = 3
-s = "abcdefg"
-printf "%*.*s\n", w, p, s
-@end example
-
-@noindent
-is exactly equivalent to:
-
-@example
-s = "abcdefg"
-printf "%5.3s\n", s
-@end example
-
-@noindent
-Both programs output @samp{@w{@bullet{}@bullet{}abc}}.
-Earlier versions of @command{awk} did not support this capability.
-If you must use such a version, you may simulate this feature by using
-concatenation to build up the format string, like so:
-
-@example
-w = 5
-p = 3
-s = "abcdefg"
-printf "%" w "." p "s\n", s
-@end example
-
-@noindent
-This is not particularly easy to read, but it does work.
-
-@c @cindex lint checks
-@cindex troubleshooting @subentry fatal errors @subentry @code{printf} format
strings
-@cindex POSIX @command{awk} @subentry @code{printf} format strings and
-C programmers may be used to supplying additional modifiers (@samp{h},
-@samp{j}, @samp{l}, @samp{L}, @samp{t}, and @samp{z}) in @code{printf}
-format strings. These are not valid in @command{awk}. Most @command{awk}
-implementations silently ignore them. If @option{--lint} is provided
-on the command line (@pxref{Options}), @command{gawk} warns about their
-use. If @option{--posix} is supplied, their use is a fatal error.
-
-@node Printf Examples
-@subsection Examples Using @code{printf}
-
-The following simple example shows
-how to use @code{printf} to make an aligned table:
-
-@example
-awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list
-@end example
-
-@noindent
-This command
-prints the names of the people (@code{$1}) in the file
-@file{mail-list} as a string of 10 characters that are left-justified. It also
-prints the phone numbers (@code{$2}) next on the line. This
-produces an aligned two-column table of names and phone numbers,
-as shown here:
-
-@example
-$ @kbd{awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list}
-@print{} Amelia 555-5553
-@print{} Anthony 555-3412
-@print{} Becky 555-7685
-@print{} Bill 555-1675
-@print{} Broderick 555-0542
-@print{} Camilla 555-2912
-@print{} Fabius 555-1234
-@print{} Julie 555-6699
-@print{} Martin 555-6480
-@print{} Samuel 555-3430
-@print{} Jean-Paul 555-2127
-@end example
-
-In this case, the phone numbers had to be printed as strings because
-the numbers are separated by dashes. Printing the phone numbers as
-numbers would have produced just the first three digits: @samp{555}.
-This would have been pretty confusing.
-
-It wasn't necessary to specify a width for the phone numbers because
-they are last on their lines. They don't need to have spaces
-after them.
-
-The table could be made to look even nicer by adding headings to the
-tops of the columns. This is done using a @code{BEGIN} rule
-(@pxref{BEGIN/END})
-so that the headers are only printed once, at the beginning of
-the @command{awk} program:
-
-@example
-awk 'BEGIN @{ print "Name Number"
- print "---- ------" @}
- @{ printf "%-10s %s\n", $1, $2 @}' mail-list
-@end example
-
-The preceding example mixes @code{print} and @code{printf} statements in
-the same program. Using just @code{printf} statements can produce the
-same results:
-
-@example
-awk 'BEGIN @{ printf "%-10s %s\n", "Name", "Number"
- printf "%-10s %s\n", "----", "------" @}
- @{ printf "%-10s %s\n", $1, $2 @}' mail-list
-@end example
-
-@noindent
-Printing each column heading with the same format specification
-used for the column elements ensures that the headings
-are aligned just like the columns.
-
-The fact that the same format specification is used three times can be
-emphasized by storing it in a variable, like this:
-
-@example
-awk 'BEGIN @{ format = "%-10s %s\n"
- printf format, "Name", "Number"
- printf format, "----", "------" @}
- @{ printf format, $1, $2 @}' mail-list
-@end example
-
-
-@node Redirection
-@section Redirecting Output of @code{print} and @code{printf}
-
-@cindex output redirection
-@cindex redirection @subentry of output
-@cindex @option{--sandbox} option @subentry output redirection with
@code{print} @subentry @code{printf}
-So far, the output from @code{print} and @code{printf} has gone
-to the standard
-output, usually the screen. Both @code{print} and @code{printf} can
-also send their output to other places.
-This is called @dfn{redirection}.
-
-@quotation NOTE
-When @option{--sandbox} is specified (@pxref{Options}),
-redirecting output to files, pipes, and coprocesses is disabled.
-@end quotation
-
-A redirection appears after the @code{print} or @code{printf} statement.
-Redirections in @command{awk} are written just like redirections in shell
-commands, except that they are written inside the @command{awk} program.
-
-@c the commas here are part of the see also
-@cindex @code{print} statement @seealso{redirection of output}
-@cindex @code{printf} statement @seealso{redirection of output}
-There are four forms of output redirection: output to a file, output
-appended to a file, output through a pipe to another command, and output
-to a coprocess. We show them all for the @code{print} statement,
-but they work identically for @code{printf}:
-
-@table @code
-@cindex @code{>} (right angle bracket) @subentry @code{>} operator (I/O)
-@cindex right angle bracket (@code{>}) @subentry @code{>} operator (I/O)
-@cindex operators @subentry input/output
-@item print @var{items} > @var{output-file}
-This redirection prints the items into the output file named
-@var{output-file}. The @value{FN} @var{output-file} can be any
-expression. Its value is changed to a string and then used as a
-@value{FN} (@pxref{Expressions}).
-
-When this type of redirection is used, the @var{output-file} is erased
-before the first output is written to it. Subsequent writes to the same
-@var{output-file} do not erase @var{output-file}, but append to it.
-(This is different from how you use redirections in shell scripts.)
-If @var{output-file} does not exist, it is created. For example, here
-is how an @command{awk} program can write a list of peoples' names to one
-file named @file{name-list}, and a list of phone numbers to another file
-named @file{phone-list}:
-
-@example
-$ @kbd{awk '@{ print $2 > "phone-list"}
-> @kbd{print $1 > "name-list" @}' mail-list}
-$ @kbd{cat phone-list}
-@print{} 555-5553
-@print{} 555-3412
-@dots{}
-$ @kbd{cat name-list}
-@print{} Amelia
-@print{} Anthony
-@dots{}
-@end example
-
-@noindent
-Each output file contains one name or number per line.
-
-@cindex @code{>} (right angle bracket) @subentry @code{>>} operator (I/O)
-@cindex right angle bracket (@code{>}) @subentry @code{>>} operator (I/O)
-@item print @var{items} >> @var{output-file}
-This redirection prints the items into the preexisting output file
-named @var{output-file}. The difference between this and the
-single-@samp{>} redirection is that the old contents (if any) of
-@var{output-file} are not erased. Instead, the @command{awk} output is
-appended to the file.
-If @var{output-file} does not exist, then it is created.
-
-@cindex @code{|} (vertical bar) @subentry @code{|} operator (I/O)
-@cindex pipe @subentry output
-@cindex output @subentry pipes
-@item print @var{items} | @var{command}
-It is possible to send output to another program through a pipe
-instead of into a file. This redirection opens a pipe to
-@var{command}, and writes the values of @var{items} through this pipe
-to another process created to execute @var{command}.
-
-The redirection argument @var{command} is actually an @command{awk}
-expression. Its value is converted to a string whose contents give
-the shell command to be run. For example, the following produces two
-files, one unsorted list of peoples' names, and one list sorted in reverse
-alphabetical order:
-
-@ignore
-10/2000:
-This isn't the best style, since COMMAND is assigned for each
-record. It's done to avoid overfull hboxes in TeX. Leave it
-alone for now and let's hope no-one notices.
-@end ignore
-
-@example
-@group
-awk '@{ print $1 > "names.unsorted"
- command = "sort -r > names.sorted"
- print $1 | command @}' mail-list
-@end group
-@end example
-
-The unsorted list is written with an ordinary redirection, while
-the sorted list is written by piping through the @command{sort} utility.
-
-The next example uses redirection to mail a message to the mailing
-list @code{bug-system}. This might be useful when trouble is encountered
-in an @command{awk} script run periodically for system maintenance:
-
-@example
-report = "mail bug-system"
-print("Awk script failed:", $0) | report
-print("at record number", FNR, "of", FILENAME) | report
-close(report)
-@end example
-
-The @code{close()} function is called here because it's a good idea to close
-the pipe as soon as all the intended output has been sent to it.
-@xref{Close Files And Pipes}
-for more information.
-
-This example also illustrates the use of a variable to represent
-a @var{file} or @var{command}---it is not necessary to always
-use a string constant. Using a variable is generally a good idea,
-because (if you mean to refer to that same file or command)
-@command{awk} requires that the string value be written identically
-every time.
-
-@cindex coprocesses
-@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
-@cindex operators @subentry input/output
-@cindex differences in @command{awk} and @command{gawk} @subentry input/output
operators
-@item print @var{items} |& @var{command}
-This redirection prints the items to the input of @var{command}.
-The difference between this and the
-single-@samp{|} redirection is that the output from @var{command}
-can be read with @code{getline}.
-Thus, @var{command} is a @dfn{coprocess}, which works together with
-but is subsidiary to the @command{awk} program.
-
-This feature is a @command{gawk} extension, and is not available in
-POSIX @command{awk}.
-@ifnotdocbook
-@xref{Getline/Coprocess},
-for a brief discussion.
-@xref{Two-way I/O},
-for a more complete discussion.
-@end ifnotdocbook
-@ifdocbook
-@xref{Getline/Coprocess}
-for a brief discussion and
-@ref{Two-way I/O}
-for a more complete discussion.
-@end ifdocbook
-@end table
-
-Redirecting output using @samp{>}, @samp{>>}, @samp{|}, or @samp{|&}
-asks the system to open a file, pipe, or coprocess only if the particular
-@var{file} or @var{command} you specify has not already been written
-to by your program or if it has been closed since it was last written to.
-
-@cindex troubleshooting @subentry printing
-It is a common error to use @samp{>} redirection for the first @code{print}
-to a file, and then to use @samp{>>} for subsequent output:
-
-@example
-# clear the file
-print "Don't panic" > "guide.txt"
-@dots{}
-# append
-print "Avoid improbability generators" >> "guide.txt"
-@end example
-
-@noindent
-This is indeed how redirections must be used from the shell. But in
-@command{awk}, it isn't necessary. In this kind of case, a program should
-use @samp{>} for all the @code{print} statements, because the output file
-is only opened once. (It happens that if you mix @samp{>} and @samp{>>}
-output is produced in the expected order. However, mixing the operators
-for the same file is definitely poor style, and is confusing to readers
-of your program.)
-
-@cindex differences in @command{awk} and @command{gawk} @subentry
implementation limitations
-@cindex implementation issues, @command{gawk} @subentry limits
-@cindex @command{awk} @subentry implementation issues @subentry pipes
-@cindex @command{gawk} @subentry implementation issues @subentry pipes
-@ifnotinfo
-As mentioned earlier
-(@pxref{Getline Notes}),
-many
-@end ifnotinfo
-@ifnottex
-@ifnotdocbook
-Many
-@end ifnotdocbook
-@end ifnottex
-older
-@command{awk} implementations limit the number of pipelines that an
@command{awk}
-program may have open to just one! In @command{gawk}, there is no such limit.
-@command{gawk} allows a program to
-open as many pipelines as the underlying operating system permits.
-
-@sidebar Piping into @command{sh}
-@cindex shells @subentry piping commands into
-
-A particularly powerful way to use redirection is to build command lines
-and pipe them into the shell, @command{sh}. For example, suppose you
-have a list of files brought over from a system where all the @value{FN}s
-are stored in uppercase, and you wish to rename them to have names in
-all lowercase. The following program is both simple and efficient:
-
-@c @cindex @command{mv} utility
-@example
-@{ printf("mv %s %s\n", $0, tolower($0)) | "sh" @}
-
-END @{ close("sh") @}
-@end example
-
-The @code{tolower()} function returns its argument string with all
-uppercase characters converted to lowercase
-(@pxref{String Functions}).
-The program builds up a list of command lines,
-using the @command{mv} utility to rename the files.
-It then sends the list to the shell for execution.
-
-@xref{Shell Quoting} for a function that can help in generating
-command lines to be fed to the shell.
-@end sidebar
-
-@node Special FD
-@section Special Files for Standard Preopened Data Streams
-@cindex standard input
-@cindex input @subentry standard
-@cindex standard output
-@cindex output @subentry standard
-@cindex error output
-@cindex standard error
-@cindex file descriptors
-@cindex files @subentry descriptors @seeentry{file descriptors}
-
-Running programs conventionally have three input and output streams
-already available to them for reading and writing. These are known
-as the @dfn{standard input}, @dfn{standard output}, and @dfn{standard
-error output}. These open streams (and any other open files or pipes)
-are often referred to by the technical term @dfn{file descriptors}.
-
-These streams are, by default, connected to your keyboard and screen, but
-they are often redirected with the shell, via the @samp{<}, @samp{<<},
-@samp{>}, @samp{>>}, @samp{>&}, and @samp{|} operators. Standard error
-is typically used for writing error messages; the reason there are two separate
-streams, standard output and standard error, is so that they can be
-redirected separately.
-
-@cindex differences in @command{awk} and @command{gawk} @subentry error
messages
-@cindex error handling
-In traditional implementations of @command{awk}, the only way to write an error
-message to standard error in an @command{awk} program is as follows:
-
-@example
-print "Serious error detected!" | "cat 1>&2"
-@end example
-
-@noindent
-This works by opening a pipeline to a shell command that can access the
-standard error stream that it inherits from the @command{awk} process.
-@c 8/2014: Mike Brennan says not to cite this as inefficient. So, fixed.
-This is far from elegant, and it also requires a
-separate process. So people writing @command{awk} programs often
-don't do this. Instead, they send the error messages to the
-screen, like this:
-
-@example
-print "Serious error detected!" > "/dev/tty"
-@end example
-
-@noindent
-(@file{/dev/tty} is a special file supplied by the operating system
-that is connected to your keyboard and screen. It represents the
-``terminal,''@footnote{The ``tty'' in @file{/dev/tty} stands for
-``Teletype,'' a serial terminal.} which on modern systems is a keyboard
-and screen, not a serial console.)
-This generally has the same effect, but not always: although the
-standard error stream is usually the screen, it can be redirected; when
-that happens, writing to the screen is not correct. In fact, if
-@command{awk} is run from a background job, it may not have a
-terminal at all.
-Then opening @file{/dev/tty} fails.
-
-@command{gawk}, BWK @command{awk}, and @command{mawk} provide
-special @value{FN}s for accessing the three standard streams.
-If the @value{FN} matches one of these special names when @command{gawk}
-(or one of the others) redirects input or output, then it directly uses
-the descriptor that the @value{FN} stands for. These special
-@value{FN}s work for all operating systems that @command{gawk}
-has been ported to, not just those that are POSIX-compliant:
-
-@cindex common extensions @subentry @code{/dev/stdin} special file
-@cindex common extensions @subentry @code{/dev/stdout} special file
-@cindex common extensions @subentry @code{/dev/stderr} special file
-@cindex extensions @subentry common @subentry @code{/dev/stdin} special file
-@cindex extensions @subentry common @subentry @code{/dev/stdout} special file
-@cindex extensions @subentry common @subentry @code{/dev/stderr} special file
-@cindex file names @subentry standard streams in @command{gawk}
-@cindex @code{/dev/@dots{}} special files
-@cindex files @subentry @code{/dev/@dots{}} special files
-@cindex @code{/dev/fd/@var{N}} special files (@command{gawk})
-@table @file
-@item /dev/stdin
-The standard input (file descriptor 0).
-
-@item /dev/stdout
-The standard output (file descriptor 1).
-
-@item /dev/stderr
-The standard error output (file descriptor 2).
-@end table
-
-With these facilities,
-the proper way to write an error message then becomes:
-
-@example
-print "Serious error detected!" > "/dev/stderr"
-@end example
-
-@cindex troubleshooting @subentry quotes with file names
-Note the use of quotes around the @value{FN}.
-Like with any other redirection, the value must be a string.
-It is a common error to omit the quotes, which leads
-to confusing results.
-
-@command{gawk} does not treat these @value{FN}s as special when
-in POSIX-compatibility mode. However, because BWK @command{awk}
-supports them, @command{gawk} does support them even when
-invoked with the @option{--traditional} option (@pxref{Options}).
-
-@node Special Files
-@section Special @value{FFN}s in @command{gawk}
-@cindex @command{gawk} @subentry file names in
-
-Besides access to standard input, standard output, and standard error,
-@command{gawk} provides access to any open file descriptor.
-Additionally, there are special @value{FN}s reserved for
-TCP/IP networking.
-
-@menu
-* Other Inherited Files:: Accessing other open files with
- @command{gawk}.
-* Special Network:: Special files for network communications.
-* Special Caveats:: Things to watch out for.
-@end menu
-
-@node Other Inherited Files
-@subsection Accessing Other Open Files with @command{gawk}
-
-Besides the @code{/dev/stdin}, @code{/dev/stdout}, and @code{/dev/stderr}
-special @value{FN}s mentioned earlier, @command{gawk} provides syntax
-for accessing any other inherited open file:
-
-@table @file
-@item /dev/fd/@var{N}
-The file associated with file descriptor @var{N}. Such a file must
-be opened by the program initiating the @command{awk} execution (typically
-the shell). Unless special pains are taken in the shell from which
-@command{gawk} is invoked, only descriptors 0, 1, and 2 are available.
-@end table
-
-The @value{FN}s @file{/dev/stdin}, @file{/dev/stdout}, and @file{/dev/stderr}
-are essentially aliases for @file{/dev/fd/0}, @file{/dev/fd/1}, and
-@file{/dev/fd/2}, respectively. However, those names are more self-explanatory.
-
-Note that using @code{close()} on a @value{FN} of the
-form @code{"/dev/fd/@var{N}"}, for file descriptor numbers
-above two, does actually close the given file descriptor.
-
-@node Special Network
-@subsection Special Files for Network Communications
-@cindex networks @subentry support for
-@cindex TCP/IP @subentry support for
-
-@command{gawk} programs
-can open a two-way
-TCP/IP connection, acting as either a client or a server.
-This is done using a special @value{FN} of the form:
-
-@example
-@file{/@var{net-type}/@var{protocol}/@var{local-port}/@var{remote-host}/@var{remote-port}}
-@end example
-
-The @var{net-type} is one of @samp{inet}, @samp{inet4}, or @samp{inet6}.
-The @var{protocol} is one of @samp{tcp} or @samp{udp},
-and the other fields represent the other essential pieces of information
-for making a networking connection.
-These @value{FN}s are used with the @samp{|&} operator for communicating
-with @w{a coprocess}
-(@pxref{Two-way I/O}).
-This is an advanced feature, mentioned here only for completeness.
-Full discussion is delayed until
-@ref{TCP/IP Networking}.
-
-@node Special Caveats
-@subsection Special @value{FFN} Caveats
-
-Here are some things to bear in mind when using the
-special @value{FN}s that @command{gawk} provides:
-
-@itemize @value{BULLET}
-@cindex compatibility mode (@command{gawk}) @subentry file names
-@cindex file names @subentry in compatibility mode
-@cindex POSIX mode
-@item
-Recognition of the @value{FN}s for the three standard preopened
-files is disabled only in POSIX mode.
-
-@item
-Recognition of the other special @value{FN}s is disabled if @command{gawk} is
in
-compatibility mode (either @option{--traditional} or @option{--posix};
-@pxref{Options}).
-
-@item
-@command{gawk} @emph{always}
-interprets these special @value{FN}s.
-For example, using @samp{/dev/fd/4}
-for output actually writes on file descriptor 4, and not on a new
-file descriptor that is @code{dup()}ed from file descriptor 4. Most of
-the time this does not matter; however, it is important to @emph{not}
-close any of the files related to file descriptors 0, 1, and 2.
-Doing so results in unpredictable behavior.
-@end itemize
-
-@node Close Files And Pipes
-@section Closing Input and Output Redirections
-@cindex files @subentry output @seeentry{output files}
-@cindex input files @subentry closing
-@cindex output @subentry files, closing
-@cindex pipe @subentry closing
-@cindex coprocesses @subentry closing
-@cindex @code{getline} command @subentry coprocesses, using from
-
-@menu
-* Close Return Value:: Using the return value from @code{close()}.
-@end menu
-
-If the same @value{FN} or the same shell command is used with @code{getline}
-more than once during the execution of an @command{awk} program
-(@pxref{Getline}),
-the file is opened (or the command is executed) the first time only.
-At that time, the first record of input is read from that file or command.
-The next time the same file or command is used with @code{getline},
-another record is read from it, and so on.
-
-Similarly, when a file or pipe is opened for output, @command{awk} remembers
-the @value{FN} or command associated with it, and subsequent
-writes to the same file or command are appended to the previous writes.
-The file or pipe stays open until @command{awk} exits.
-
-@cindexawkfunc{close}
-This implies that special steps are necessary in order to read the same
-file again from the beginning, or to rerun a shell command (rather than
-reading more output from the same command). The @code{close()} function
-makes these things possible:
-
-@example
-close(@var{filename})
-@end example
-
-@noindent
-or:
-
-@example
-close(@var{command})
-@end example
-
-The argument @var{filename} or @var{command} can be any expression. Its
-value must @emph{exactly} match the string that was used to open the file or
-start the command (spaces and other ``irrelevant'' characters
-included). For example, if you open a pipe with this:
-
-@example
-"sort -r names" | getline foo
-@end example
-
-@noindent
-then you must close it with this:
-
-@example
-close("sort -r names")
-@end example
-
-Once this function call is executed, the next @code{getline} from that
-file or command, or the next @code{print} or @code{printf} to that
-file or command, reopens the file or reruns the command.
-Because the expression that you use to close a file or pipeline must
-exactly match the expression used to open the file or run the command,
-it is good practice to use a variable to store the @value{FN} or command.
-The previous example becomes the following:
-
-@example
-@group
-sortcom = "sort -r names"
-sortcom | getline foo
-@end group
-@group
-@dots{}
-close(sortcom)
-@end group
-@end example
-
-@noindent
-This helps avoid hard-to-find typographical errors in your @command{awk}
-programs. Here are some of the reasons for closing an output file:
-
-@itemize @value{BULLET}
-@item
-To write a file and read it back later on in the same @command{awk}
-program. Close the file after writing it, then
-begin reading it with @code{getline}.
-
-@item
-To write numerous files, successively, in the same @command{awk}
-program. If the files aren't closed, eventually @command{awk} may exceed a
-system limit on the number of open files in one process. It is best to
-close each one when the program has finished writing it.
-
-@item
-To make a command finish. When output is redirected through a pipe,
-the command reading the pipe normally continues to try to read input
-as long as the pipe is open. Often this means the command cannot
-really do its work until the pipe is closed. For example, if
-output is redirected to the @command{mail} program, the message is not
-actually sent until the pipe is closed.
-
-@item
-To run the same program a second time, with the same arguments.
-This is not the same thing as giving more input to the first run!
-
-For example, suppose a program pipes output to the @command{mail} program.
-If it outputs several lines redirected to this pipe without closing
-it, they make a single message of several lines. By contrast, if the
-program closes the pipe after each line of output, then each line makes
-a separate message.
-@end itemize
-
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{close()} function
-@cindex portability @subentry @code{close()} function and
-@cindex @code{close()} function @subentry portability
-If you use more files than the system allows you to have open,
-@command{gawk} attempts to multiplex the available open files among
-your @value{DF}s. @command{gawk}'s ability to do this depends upon the
-facilities of your operating system, so it may not always work. It is
-therefore both good practice and good portability advice to always
-use @code{close()} on your files when you are done with them.
-In fact, if you are using a lot of pipes, it is essential that
-you close commands when done. For example, consider something like this:
-
-@example
-@{
- @dots{}
- command = ("grep " $1 " /some/file | my_prog -q " $3)
- while ((command | getline) > 0) @{
- @var{process output of} command
- @}
- # need close(command) here
-@}
-@end example
-
-This example creates a new pipeline based on data in @emph{each} record.
-Without the call to @code{close()} indicated in the comment, @command{awk}
-creates child processes to run the commands, until it eventually
-runs out of file descriptors for more pipelines.
-
-Even though each command has finished (as indicated by the end-of-file
-return status from @code{getline}), the child process is not
-terminated;@footnote{The technical terminology is rather morbid.
-The finished child is called a ``zombie,'' and cleaning up after
-it is referred to as ``reaping.''}
-@c Good old UNIX: give the marketing guys fits, that's the ticket
-more importantly, the file descriptor for the pipe
-is not closed and released until @code{close()} is called or
-@command{awk} exits.
-
-@code{close()} silently does nothing if given an argument that
-does not represent a file, pipe, or coprocess that was opened with
-a redirection. In such a case, it returns a negative value,
-indicating an error. In addition, @command{gawk} sets @code{ERRNO}
-to a string indicating the error.
-
-Note also that @samp{close(FILENAME)} has no ``magic'' effects on the
-implicit loop that reads through the files named on the command line.
-It is, more likely, a close of a file that was never opened with a
-redirection, so @command{awk} silently does nothing, except return
-a negative value.
-
-@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O) @subentry
pipes, closing
-When using the @samp{|&} operator to communicate with a coprocess,
-it is occasionally useful to be able to close one end of the two-way
-pipe without closing the other.
-This is done by supplying a second argument to @code{close()}.
-As in any other call to @code{close()},
-the first argument is the name of the command or special file used
-to start the coprocess.
-The second argument should be a string, with either of the values
-@code{"to"} or @code{"from"}. Case does not matter.
-As this is an advanced feature, discussion is
-delayed until
-@ref{Two-way I/O},
-which describes it in more detail and gives an example.
-
-@node Close Return Value
-@subsection Using @code{close()}'s Return Value
-@cindex dark corner @subentry @code{close()} function
-@cindex @code{close()} function @subentry return value
-@cindex return value, @code{close()} function
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{close()} function
-@cindex Unix @command{awk} @subentry @code{close()} function and
-
-In many older versions of Unix @command{awk}, the @code{close()} function
-is actually a statement.
-@value{DARKCORNER}
-It is a syntax error to try and use the return
-value from @code{close()}:
-
-@example
-command = "@dots{}"
-command | getline info
-retval = close(command) # syntax error in many Unix awks
-@end example
-
-@cindex @command{gawk} @subentry @code{ERRNO} variable in
-@cindex @code{ERRNO} variable @subentry with @command{close()} function
-@command{gawk} treats @code{close()} as a function.
-The return value is @minus{}1 if the argument names something
-that was never opened with a redirection, or if there is
-a system problem closing the file or process.
-In these cases, @command{gawk} sets the predefined variable
-@code{ERRNO} to a string describing the problem.
-
-In @command{gawk}, starting with @value{PVERSION} 4.2, when closing a pipe or
-coprocess (input or output), the return value is the exit status of the
-command, as described in @ref{table-close-pipe-return-values}.@footnote{Prior
-to @value{PVERSION} 4.2, the return value from closing a pipe or co-process
-was the full 16-bit exit value as defined by the @code{wait()} system
-call.} Otherwise, it is the return value from the system's @code{close()}
-or @code{fclose()} C functions when closing input or output files,
-respectively. This value is zero if the close succeeds, or @minus{}1
-if it fails.
-Recent versions of BWK @command{awk} also return the same values
-from @command{close()}.
-
-@float Table,table-close-pipe-return-values
-@caption{Return values from @code{close()} of a pipe}
-@multitable @columnfractions .50 .50
-@headitem Situation @tab Return value from @code{close()}
-@item Normal exit of command @tab Command's exit status
-@item Death by signal of command @tab 256 + number of murderous signal
-@item Death by signal of command with core dump @tab 512 + number of murderous
signal
-@item Some kind of error @tab @minus{}1
-@end multitable
-@end float
-
-@cindex POSIX mode
-The POSIX standard is very vague; it says that @code{close()}
-returns zero on success and a nonzero value otherwise. In general,
-different implementations vary in what they report when closing
-pipes; thus, the return value cannot be used portably.
-@value{DARKCORNER}
-In POSIX mode (@pxref{Options}), @command{gawk} just returns zero
-when closing a pipe.
-
-@node Noflush
-@section Speeding Up Pipe Output
-@cindex @code{PROCINFO} array @subentry not flushing pipe buffers
-@cindex pipe output, speeding up
-
-This @value{SECTION} describes a @command{gawk}-specific feature.
-
-Normally, when you send data down a pipeline to a command with
-@code{print} or @code{printf}, @command{gawk} @dfn{flushes} the
-output down the pipe. That is, output is not buffered, but
-written directly. This assures, that pipeline output
-intermixed with @command{gawk}'s output comes out in the
-expected order:
-
-@example
-print "something" # goes to standard output
-print "something else" | "some-command" # also to standard output
-print "more stuff" # and this too
-@end example
-
-There can be a price to pay for this; flushing data down
-the pipeline uses more CPU time, and in certain environments
-this can become expensive.
-
-You can tell @command{gawk} not to flush buffered data in
-one of two ways:
-
-@itemize @bullet
-@item
-Set @code{PROCINFO["BUFFERPIPE"]} to any value. When this is done,
-@command{gawk} will buffer data for all pipelines.
-
-@item
-Set @code{PROCINFO["@var{command}", "BUFFERPIPE"]} to any value.
-In this case, only @var{command}'s data will be fully buffered.
-@end itemize
-
-You @emph{must} create one or the other of these elements
-in @code{PROCINFO} before the first @code{print} or
-@code{printf} to the pipeline. Doing so after output has
-already been sent is too late.
-
-Be aware that using this feature may change the output behavior of
-your programs, so exercise caution.
-
-@node Nonfatal
-@section Enabling Nonfatal Output
-@cindex @code{PROCINFO} array @subentry nonfatal output
-@cindex output, nonfatal
-@cindex nonfatal output
-
-This @value{SECTION} describes a @command{gawk}-specific feature.
-
-In standard @command{awk}, output with @code{print} or @code{printf}
-to a nonexistent file, or some other I/O error (such as filling up the
-disk) is a fatal error.
-
-@example
-$ @kbd{gawk 'BEGIN @{ print "hi" > "/no/such/file" @}'}
-@error{} gawk: cmd. line:1: fatal: can't redirect to `/no/such/file' (No
-@error{} such file or directory)
-@end example
-
-@command{gawk} makes it possible to detect that an error has
-occurred, allowing you to possibly recover from the error, or
-at least print an error message of your choosing before exiting.
-You can do this in one of two ways:
-
-@itemize @bullet
-@item
-For all output files, by assigning any value to @code{PROCINFO["NONFATAL"]}.
-
-@item
-On a per-file basis, by assigning any value to
-@code{PROCINFO[@var{filename}, "NONFATAL"]}.
-Here, @var{filename} is the name of the file to which
-you wish output to be nonfatal.
-@end itemize
-
-Once you have enabled nonfatal output, you must check @code{ERRNO}
-after every relevant @code{print} or @code{printf} statement to
-see if something went wrong. It is also a good idea to initialize
-@code{ERRNO} to zero before attempting the output. For example:
-
-@example
-$ @kbd{gawk '}
-> @kbd{BEGIN @{}
-> @kbd{ PROCINFO["NONFATAL"] = 1}
-> @kbd{ ERRNO = 0}
-> @kbd{ print "hi" > "/no/such/file"}
-> @kbd{ if (ERRNO) @{}
-> @kbd{ print("Output failed:", ERRNO) > "/dev/stderr"}
-> @kbd{ exit 1}
-> @kbd{ @}}
-> @kbd{@}'}
-@error{} Output failed: No such file or directory
-@end example
-
-Here, @command{gawk} did not produce a fatal error; instead
-it let the @command{awk} program code detect the problem and handle it.
-
-This mechanism works also for standard output and standard error.
-For standard output, you may use @code{PROCINFO["-", "NONFATAL"]}
-or @code{PROCINFO["/dev/stdout", "NONFATAL"]}. For standard error, use
-@code{PROCINFO["/dev/stderr", "NONFATAL"]}.
-
-@cindex @env{GAWK_SOCK_RETRIES} environment variable
-@cindex environment variables @subentry @env{GAWK_SOCK_RETRIES}
-When attempting to open a TCP/IP socket (@pxref{TCP/IP Networking}),
-@command{gawk} tries multiple times. The @env{GAWK_SOCK_RETRIES}
-environment variable (@pxref{Other Environment Variables}) allows you to
-override @command{gawk}'s builtin default number of attempts. However,
-once nonfatal I/O is enabled for a given socket, @command{gawk} only
-retries once, relying on @command{awk}-level code to notice that there
-was a problem.
-
-@node Output Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-The @code{print} statement prints comma-separated expressions. Each
-expression is separated by the value of @code{OFS} and terminated by
-the value of @code{ORS}. @code{OFMT} provides the conversion format
-for numeric values for the @code{print} statement.
-
-@item
-The @code{printf} statement provides finer-grained control over output,
-with format-control letters for different data types and various flags
-that modify the behavior of the format-control letters.
-
-@item
-Output from both @code{print} and @code{printf} may be redirected to
-files, pipes, and coprocesses.
-
-@item
-@command{gawk} provides special @value{FN}s for access to standard input,
-output, and error, and for network communications.
-
-@item
-Use @code{close()} to close open file, pipe, and coprocess redirections.
-For coprocesses, it is possible to close only one direction of the
-communications.
-
-@item
-Normally errors with @code{print} or @code{printf} are fatal.
-@command{gawk} lets you make output errors be nonfatal either for
-all files or on a per-file basis. You must then check for errors
-after every relevant output statement.
-
-@end itemize
-
-@c EXCLUDE START
-@node Output Exercises
-@section Exercises
-
-@enumerate
-@item
-Rewrite the program:
-
-@example
-awk 'BEGIN @{ print "Month Crates"
- print "----- ------" @}
- @{ print $1, " ", $2 @}' inventory-shipped
-@end example
-
-@noindent
-from @ref{Output Separators}, by using a new value of @code{OFS}.
-
-@item
-Use the @code{printf} statement to line up the headings and table data
-for the @file{inventory-shipped} example that was covered in @ref{Print}.
-
-@item
-What happens if you forget the double quotes when redirecting
-output, as follows:
-
-@example
-BEGIN @{ print "Serious error detected!" > /dev/stderr @}
-@end example
-
-@end enumerate
-@c EXCLUDE END
-
-
-@node Expressions
-@chapter Expressions
-@cindex expressions
-
-Expressions are the basic building blocks of @command{awk} patterns
-and actions. An expression evaluates to a value that you can print, test,
-or pass to a function. Additionally, an expression
-can assign a new value to a variable or a field by using an assignment
operator.
-
-An expression can serve as a pattern or action statement on its own.
-Most other kinds of
-statements contain one or more expressions that specify the data on which to
-operate. As in other languages, expressions in @command{awk} can include
-variables, array references, constants, and function calls, as well as
-combinations of these with various operators.
-
-@menu
-* Values:: Constants, Variables, and Regular Expressions.
-* All Operators:: @command{gawk}'s operators.
-* Truth Values and Conditions:: Testing for true and false.
-* Function Calls:: A function call is an expression.
-* Precedence:: How various operators nest.
-* Locales:: How the locale affects things.
-* Expressions Summary:: Expressions summary.
-@end menu
-
-@node Values
-@section Constants, Variables, and Conversions
-
-Expressions are built up from values and the operations performed
-upon them. This @value{SECTION} describes the elementary objects
-that provide the values used in expressions.
-
-@menu
-* Constants:: String, numeric and regexp constants.
-* Using Constant Regexps:: When and how to use a regexp constant.
-* Variables:: Variables give names to values for later use.
-* Conversion:: The conversion of strings to numbers and vice
- versa.
-@end menu
-
-@node Constants
-@subsection Constant Expressions
-
-@cindex constants @subentry types of
-
-The simplest type of expression is the @dfn{constant}, which always has
-the same value. There are three types of constants: numeric,
-string, and regular expression.
-
-Each is used in the appropriate context when you need a data
-value that isn't going to change. Numeric constants can
-have different forms, but are internally stored in an identical manner.
-
-@menu
-* Scalar Constants:: Numeric and string constants.
-* Nondecimal-numbers:: What are octal and hex numbers.
-* Regexp Constants:: Regular Expression constants.
-@end menu
-
-@node Scalar Constants
-@subsubsection Numeric and String Constants
-
-@cindex constants @subentry numeric
-@cindex numeric @subentry constants
-A @dfn{numeric constant} stands for a number. This number can be an
-integer, a decimal fraction, or a number in scientific (exponential)
-notation.@footnote{The internal representation of all numbers,
-including integers, uses double-precision floating-point numbers.
-On most modern systems, these are in IEEE 754 standard format.
-@xref{Arbitrary Precision Arithmetic}, for much more information.}
-Here are some examples of numeric constants that all
-have the same value:
-
-@example
-105
-1.05e+2
-1050e-1
-@end example
-
-@cindex string @subentry constants
-@cindex constants @subentry string
-A @dfn{string constant} consists of a sequence of characters enclosed in
-double quotation marks. For example:
-
-@example
-"parrot"
-@end example
-
-@noindent
-@cindex differences in @command{awk} and @command{gawk} @subentry strings
-@cindex strings @subentry length limitations
-@cindex ASCII
-represents the string whose contents are @samp{parrot}. Strings in
-@command{gawk} can be of any length, and they can contain any of the possible
-eight-bit ASCII characters, including ASCII @sc{nul} (character code zero).
-Other @command{awk}
-implementations may have difficulty with some character codes.
-
-Some languages allow you to continue long strings across
-multiple lines by ending the line with a backslash. For example in C:
-
-@example
-#include <stdio.h>
-
-int main()
-@{
- printf("hello, \
-world\n");
- return 0;
-@}
-@end example
-
-@noindent
-In such a case, the C compiler removes both the backslash and the newline,
-producing a string as if it had been typed @samp{"hello, world\n"}.
-This is useful when a single string needs to contain a large amount of text.
-
-The POSIX standard says explicitly that newlines are not allowed inside string
-constants. And indeed, all @command{awk} implementations report an error
-if you try to do so. For example:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print "hello, }
-> @kbd{world" @}'}
-@print{} gawk: cmd. line:1: BEGIN @{ print "hello,
-@print{} gawk: cmd. line:1: ^ unterminated string
-@print{} gawk: cmd. line:1: BEGIN @{ print "hello,
-@print{} gawk: cmd. line:1: ^ syntax error
-@end example
-
-@cindex dark corner @subentry string continuation
-@cindex strings @subentry continuation across lines
-@cindex differences in @command{awk} and @command{gawk} @subentry strings
-Although POSIX doesn't define what happens if you use an escaped
-newline, as in the previous C example, all known versions of
-@command{awk} allow you to do so. Unfortunately, what each one
-does with such a string varies. @value{DARKCORNER} @command{gawk},
-@command{mawk}, and the OpenSolaris POSIX @command{awk}
-(@pxref{Other Versions}) elide the backslash and newline, as in C:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print "hello, \}
-> @kbd{world" @}'}
-@print{} hello, world
-@end example
-
-@cindex POSIX mode
-In POSIX mode (@pxref{Options}), @command{gawk} does not
-allow escaped newlines. Otherwise, it behaves as just described.
-
-BWK @command{awk}@footnote{In all examples throughout this @value{DOCUMENT},
-@command{nawk} is BWK @command{awk}.} and BusyBox @command{awk}
-remove the backslash but leave the newline
-intact, as part of the string:
-
-@example
-$ @kbd{nawk 'BEGIN @{ print "hello, \}
-> @kbd{world" @}'}
-@print{} hello,
-@print{} world
-@end example
-
-@node Nondecimal-numbers
-@subsubsection Octal and Hexadecimal Numbers
-@cindex octal numbers
-@cindex hexadecimal numbers
-@cindex numbers @subentry octal
-@cindex numbers @subentry hexadecimal
-
-In @command{awk}, all numbers are in decimal (i.e., base 10). Many other
-programming languages allow you to specify numbers in other bases, often
-octal (base 8) and hexadecimal (base 16).
-In octal, the numbers go 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on.
-Just as @samp{11} in decimal is 1 times 10 plus 1, so
-@samp{11} in octal is 1 times 8 plus 1. This equals 9 in decimal.
-In hexadecimal, there are 16 digits. Because the everyday decimal
-number system only has ten digits (@samp{0}--@samp{9}), the letters
-@samp{a} through @samp{f} represent the rest.
-(Case in the letters is usually irrelevant; hexadecimal @samp{a} and @samp{A}
-have the same value.)
-Thus, @samp{11} in
-hexadecimal is 1 times 16 plus 1, which equals 17 in decimal.
-
-Just by looking at plain @samp{11}, you can't tell what base it's in.
-So, in C, C++, and other languages derived from C,
-@c such as PERL, but we won't mention that....
-there is a special notation to signify the base.
-Octal numbers start with a leading @samp{0},
-and hexadecimal numbers start with a leading @samp{0x} or @samp{0X}:
-
-@table @code
-@item 11
-Decimal value 11
-
-@item 011
-Octal 11, decimal value 9
-
-@item 0x11
-Hexadecimal 11, decimal value 17
-@end table
-
-This example shows the difference:
-
-@example
-$ @kbd{gawk 'BEGIN @{ printf "%d, %d, %d\n", 011, 11, 0x11 @}'}
-@print{} 9, 11, 17
-@end example
-
-Being able to use octal and hexadecimal constants in your programs is most
-useful when working with data that cannot be represented conveniently as
-characters or as regular numbers, such as binary data of various sorts.
-
-@cindex @command{gawk} @subentry octal numbers and
-@cindex @command{gawk} @subentry hexadecimal numbers and
-@command{gawk} allows the use of octal and hexadecimal
-constants in your program text. However, such numbers in the input data
-are not treated differently; doing so by default would break old
-programs.
-(If you really need to do this, use the @option{--non-decimal-data}
-command-line option;
-@pxref{Nondecimal Data}.)
-If you have octal or hexadecimal data,
-you can use the @code{strtonum()} function
-(@pxref{String Functions})
-to convert the data into a number.
-Most of the time, you will want to use octal or hexadecimal constants
-when working with the built-in bit-manipulation functions;
-see @ref{Bitwise Functions}
-for more information.
-
-Unlike in some early C implementations, @samp{8} and @samp{9} are not
-valid in octal constants. For example, @command{gawk} treats @samp{018}
-as decimal 18:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print "021 is", 021 ; print 018 @}'}
-@print{} 021 is 17
-@print{} 18
-@end example
-
-@cindex compatibility mode (@command{gawk}) @subentry octal numbers
-@cindex compatibility mode (@command{gawk}) @subentry hexadecimal numbers
-Octal and hexadecimal source code constants are a @command{gawk} extension.
-If @command{gawk} is in compatibility mode
-(@pxref{Options}),
-they are not available.
-
-@sidebar A Constant's Base Does Not Affect Its Value
-
-Once a numeric constant has
-been converted internally into a number,
-@command{gawk} no longer remembers
-what the original form of the constant was; the internal value is
-always used. This has particular consequences for conversion of
-numbers to strings:
-
-@example
-$ @kbd{gawk 'BEGIN @{ printf "0x11 is <%s>\n", 0x11 @}'}
-@print{} 0x11 is <17>
-@end example
-@end sidebar
-
-@node Regexp Constants
-@subsubsection Regular Expression Constants
-
-@cindex regexp constants
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-A @dfn{regexp constant} is a regular expression description enclosed in
-slashes, such as @code{@w{/^beginning and end$/}}. Most regexps used in
-@command{awk} programs are constant, but the @samp{~} and @samp{!~}
-matching operators can also match computed or dynamic regexps
-(which are typically just ordinary strings or variables that contain a regexp,
-but could be more complex expressions).
-
-@node Using Constant Regexps
-@subsection Using Regular Expression Constants
-
-Regular expression constants consist of text describing
-a regular expression enclosed in slashes (such as @code{/the +answer/}).
-This @value{SECTION} describes how such constants work in
-POSIX @command{awk} and @command{gawk}, and then goes on to describe
-@dfn{strongly typed regexp constants}, which are a @command{gawk} extension.
-
-@menu
-* Standard Regexp Constants:: Regexp constants in standard @command{awk}.
-* Strong Regexp Constants:: Strongly typed regexp constants.
-@end menu
-
-@node Standard Regexp Constants
-@subsubsection Standard Regular Expression Constants
-
-@cindex dark corner @subentry regexp constants
-When used on the righthand side of the @samp{~} or @samp{!~}
-operators, a regexp constant merely stands for the regexp that is to be
-matched.
-However, regexp constants (such as @code{/foo/}) may be used like simple
expressions.
-When a
-regexp constant appears by itself, it has the same meaning as if it appeared
-in a pattern (i.e., @samp{($0 ~ /foo/)}).
-@value{DARKCORNER}
-@xref{Expression Patterns}.
-This means that the following two code segments:
-
-@example
-if ($0 ~ /barfly/ || $0 ~ /camelot/)
- print "found"
-@end example
-
-@noindent
-and:
-
-@example
-if (/barfly/ || /camelot/)
- print "found"
-@end example
-
-@noindent
-are exactly equivalent.
-One rather bizarre consequence of this rule is that the following
-Boolean expression is valid, but does not do what its author probably
-intended:
-
-@example
-# Note that /foo/ is on the left of the ~
-if (/foo/ ~ $1) print "found foo"
-@end example
-
-@c @cindex automatic warnings
-@c @cindex warnings, automatic
-@cindex @command{gawk} @subentry regexp constants and
-@cindex regexp constants @subentry in @command{gawk}
-@noindent
-This code is ``obviously'' testing @code{$1} for a match against the regexp
-@code{/foo/}. But in fact, the expression @samp{/foo/ ~ $1} really means
-@samp{($0 ~ /foo/) ~ $1}. In other words, first match the input record
-against the regexp @code{/foo/}. The result is either zero or one,
-depending upon the success or failure of the match. That result
-is then matched against the first field in the record.
-Because it is unlikely that you would ever really want to make this kind of
-test, @command{gawk} issues a warning when it sees this construct in
-a program.
-Another consequence of this rule is that the assignment statement:
-
-@example
-matches = /foo/
-@end example
-
-@noindent
-assigns either zero or one to the variable @code{matches}, depending
-upon the contents of the current input record.
-
-@cindex differences in @command{awk} and @command{gawk} @subentry regexp
constants
-@cindex dark corner @subentry regexp constants @subentry as arguments to
user-defined functions
-@cindexgawkfunc{gensub}
-@cindexawkfunc{sub}
-@cindexawkfunc{gsub}
-Constant regular expressions are also used as the first argument for
-the @code{gensub()}, @code{sub()}, and @code{gsub()} functions, as the
-second argument of the @code{match()} function,
-and as the third argument of the @code{split()} and @code{patsplit()} functions
-(@pxref{String Functions}).
-Modern implementations of @command{awk}, including @command{gawk}, allow
-the third argument of @code{split()} to be a regexp constant, but some
-older implementations do not.
-@value{DARKCORNER}
-Because some built-in functions accept regexp constants as arguments,
-confusion can arise when attempting to use regexp constants as arguments
-to user-defined functions (@pxref{User-defined}). For example:
-
-@example
-@group
-function mysub(pat, repl, str, global)
-@{
- if (global)
- gsub(pat, repl, str)
- else
- sub(pat, repl, str)
- return str
-@}
-@end group
-
-@group
-@{
- @dots{}
- text = "hi! hi yourself!"
- mysub(/hi/, "howdy", text, 1)
- @dots{}
-@}
-@end group
-@end example
-
-@c @cindex automatic warnings
-@c @cindex warnings, automatic
-In this example, the programmer wants to pass a regexp constant to the
-user-defined function @code{mysub()}, which in turn passes it on to
-either @code{sub()} or @code{gsub()}. However, what really happens is that
-the @code{pat} parameter is assigned a value of either one or zero, depending
upon whether
-or not @code{$0} matches @code{/hi/}.
-@command{gawk} issues a warning when it sees a regexp constant used as
-a parameter to a user-defined function, because passing a truth value in
-this way is probably not what was intended.
-
-@node Strong Regexp Constants
-@subsubsection Strongly Typed Regexp Constants
-
-This @value{SECTION} describes a @command{gawk}-specific feature.
-
-As we saw in the previous @value{SECTION},
-regexp constants (@code{/@dots{}/}) hold a strange position in the
-@command{awk} language. In most contexts, they act like an expression:
-@samp{$0 ~ /@dots{}/}. In other contexts, they denote only a regexp to
-be matched. In no case are they really a ``first class citizen'' of the
-language. That is, you cannot define a scalar variable whose type is
-``regexp'' in the same sense that you can define a variable to be a
-number or a string:
-
-@example
-num = 42 @ii{Numeric variable}
-str = "hi" @ii{String variable}
-re = /foo/ @ii{Wrong!} re @ii{is the result of} $0 ~ /foo/
-@end example
-
-For a number of more advanced use cases,
-it would be nice to have regexp constants that
-are @dfn{strongly typed}; in other words, that denote a regexp useful
-for matching, and not an expression.
-
-@cindex values @subentry regexp
-@command{gawk} provides this feature. A strongly typed regexp constant
-looks almost like a regular regexp constant, except that it is preceded
-by an @samp{@@} sign:
-
-@example
-re = @@/foo/ @ii{Regexp variable}
-@end example
-
-Strongly typed regexp constants @emph{cannot} be used everywhere that a
-regular regexp constant can, because this would make the language even more
-confusing. Instead, you may use them only in certain contexts:
-
-@itemize @bullet
-@item
-On the righthand side of the @samp{~} and @samp{!~} operators: @samp{some_var
~ @@/foo/}
-(@pxref{Regexp Usage}).
-
-@item
-In the @code{case} part of a @code{switch} statement
-(@pxref{Switch Statement}).
-
-@item
-As an argument to one of the built-in functions that accept regexp constants:
-@code{gensub()},
-@code{gsub()},
-@code{match()},
-@code{patsplit()},
-@code{split()},
-and
-@code{sub()}
-(@pxref{String Functions}).
-
-@item
-As a parameter in a call to a user-defined function
-(@pxref{User-defined}).
-
-@item
-As the return value of a user-defined function.
-
-@item
-On the righthand side of an assignment to a variable: @samp{some_var =
@@/foo/}.
-In this case, the type of @code{some_var} is regexp. Additionally,
@code{some_var}
-can be used with @samp{~} and @samp{!~}, passed to one of the built-in
functions
-listed above, or passed as a parameter to a user-defined function.
-@end itemize
-
-You may use the @option{-v} option (@pxref{Options}) to assign a
-strongly-typed regexp constant to a variable on the command line, like so:
-
-@example
-gawk -v pattern='@@/something(interesting)+/' @dots{}
-@end example
-
-@noindent
-You may also make such assignments as regular command-line arguments
-(@pxref{Other Arguments}).
-
-You may use the @code{typeof()} built-in function
-(@pxref{Type Functions})
-to determine if a variable or function parameter is
-a regexp variable.
-
-The true power of this feature comes from the ability to create variables that
-have regexp type. Such variables can be passed on to user-defined functions,
-without the confusing aspects of computed regular expressions created from
-strings or string constants. They may also be passed through indirect function
-calls (@pxref{Indirect Calls})
-and on to the built-in functions that accept regexp constants.
-
-When used in numeric conversions, strongly typed regexp variables convert
-to zero. When used in string conversions, they convert to the string
-value of the original regexp text.
-
-There is an additional, interesting corner case. When used as the third
-argument to @code{sub()} or @code{gsub()}, they retain their type. Thus,
-if you have something like this:
-
-@example
-re = @@/don't panic/
-sub(/don't/, "do", re)
-print typeof(re), re
-@end example
-
-@noindent
-then @code{re} retains its type, but now attempts to match the string
-@samp{do panic}. This provides a (very indirect) way to create regexp-typed
-variables at runtime.
-
-@node Variables
-@subsection Variables
-
-@cindex variables @subentry user-defined
-@cindex user-defined @subentry variables
-@dfn{Variables} are ways of storing values at one point in your program for
-use later in another part of your program. They can be manipulated
-entirely within the program text, and they can also be assigned values
-on the @command{awk} command line.
-
-@menu
-* Using Variables:: Using variables in your programs.
-* Assignment Options:: Setting variables on the command line and a
- summary of command-line syntax. This is an
- advanced method of input.
-@end menu
-
-@node Using Variables
-@subsubsection Using Variables in a Program
-
-Variables let you give names to values and refer to them later. Variables
-have already been used in many of the examples. The name of a variable
-must be a sequence of letters, digits, or underscores, and it may not begin
-with a digit.
-Here, a @dfn{letter} is any one of the 52 upper- and lowercase
-English letters. Other characters that may be defined as letters
-in non-English locales are not valid in variable names.
-Case is significant in variable names; @code{a} and @code{A}
-are distinct variables.
-
-A variable name is a valid expression by itself; it represents the
-variable's current value. Variables are given new values with
-@dfn{assignment operators}, @dfn{increment operators}, and
-@dfn{decrement operators}
-(@pxref{Assignment Ops}).
-In addition, the @code{sub()} and @code{gsub()} functions can
-change a variable's value, and the @code{match()}, @code{split()},
-and @code{patsplit()} functions can change the contents of their
-array parameters (@pxref{String Functions}).
-
-@cindex variables @subentry built-in
-@cindex variables @subentry initializing
-A few variables have special built-in meanings, such as @code{FS} (the
-field separator) and @code{NF} (the number of fields in the current input
-record). @xref{Built-in Variables} for a list of the predefined variables.
-These predefined variables can be used and assigned just like all other
-variables, but their values are also used or changed automatically by
-@command{awk}. All predefined variables' names are entirely uppercase.
-
-Variables in @command{awk} can be assigned either numeric or string values.
-The kind of value a variable holds can change over the life of a program.
-By default, variables are initialized to the empty string, which
-is zero if converted to a number. There is no need to explicitly
-initialize a variable in @command{awk},
-which is what you would do in C and in most other traditional languages.
-
-@node Assignment Options
-@subsubsection Assigning Variables on the Command Line
-@cindex variables @subentry assigning on command line
-@cindex command line @subentry variables, assigning on
-
-Any @command{awk} variable can be set by including a @dfn{variable assignment}
-among the arguments on the command line when @command{awk} is invoked
-(@pxref{Other Arguments}).
-Such an assignment has the following form:
-
-@example
-@var{variable}=@var{text}
-@end example
-
-@cindex @option{-v} option
-@noindent
-With it, a variable is set either at the beginning of the
-@command{awk} run or in between input files.
-When the assignment is preceded with the @option{-v} option,
-as in the following:
-
-@example
--v @var{variable}=@var{text}
-@end example
-
-@noindent
-the variable is set at the very beginning, even before the
-@code{BEGIN} rules execute. The @option{-v} option and its assignment
-must precede all the @value{FN} arguments, as well as the program text.
-(@xref{Options} for more information about
-the @option{-v} option.)
-Otherwise, the variable assignment is performed at a time determined by
-its position among the input file arguments---after the processing of the
-preceding input file argument. For example:
-
-@example
-awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list
-@end example
-
-@noindent
-prints the value of field number @code{n} for all input records. Before
-the first file is read, the command line sets the variable @code{n}
-equal to four. This causes the fourth field to be printed in lines from
-@file{inventory-shipped}. After the first file has finished,
-but before the second file is started, @code{n} is set to two, so that the
-second field is printed in lines from @file{mail-list}:
-
-@example
-$ @kbd{awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list}
-@print{} 15
-@print{} 24
-@dots{}
-@print{} 555-5553
-@print{} 555-3412
-@dots{}
-@end example
-
-@cindex dark corner @subentry command-line arguments
-Command-line arguments are made available for explicit examination by
-the @command{awk} program in the @code{ARGV} array
-(@pxref{ARGC and ARGV}).
-@command{awk} processes the values of command-line assignments for escape
-sequences
-(@pxref{Escape Sequences}).
-@value{DARKCORNER}
-
-Normally, variables assigned on the command line (with or without the
-@option{-v} option) are treated as strings. When such variables are
-used as numbers, @command{awk}'s normal automatic conversion of strings
-to numbers takes place, and everything ``just works.''
-
-However, @command{gawk} supports variables whose types are ``regexp''.
-You can assign variables of this type using the following syntax:
-
-@example
-gawk -v 're1=@@/foo|bar/' '@dots{}' /path/to/file1 're2=@@/baz|quux/'
/path/to/file2
-@end example
-
-@noindent
-Strongly typed regexps are an advanced feature (@pxref{Strong Regexp
Constants}).
-We mention them here only for completeness.
-
-@node Conversion
-@subsection Conversion of Strings and Numbers
-
-Number-to-string and string-to-number conversion are generally
-straightforward. There can be subtleties to be aware of;
-this @value{SECTION} discusses this important facet of @command{awk}.
-
-@menu
-* Strings And Numbers:: How @command{awk} Converts Between Strings And
- Numbers.
-* Locale influences conversions:: How the locale may affect conversions.
-@end menu
-
-@node Strings And Numbers
-@subsubsection How @command{awk} Converts Between Strings and Numbers
-
-@cindex converting @subentry string to numbers
-@cindex strings @subentry converting
-@cindex numbers @subentry converting
-@cindex converting @subentry numbers to strings
-Strings are converted to numbers and numbers are converted to strings, if the
context
-of the @command{awk} program demands it. For example, if the value of
-either @code{foo} or @code{bar} in the expression @samp{foo + bar}
-happens to be a string, it is converted to a number before the addition
-is performed. If numeric values appear in string concatenation, they
-are converted to strings. Consider the following:
-
-@example
-@group
-two = 2; three = 3
-print (two three) + 4
-@end group
-@end example
-
-@noindent
-This prints the (numeric) value 27. The numeric values of
-the variables @code{two} and @code{three} are converted to strings and
-concatenated together. The resulting string is converted back to the
-number 23, to which 4 is then added.
-
-@cindex null strings @subentry converting numbers to strings
-@cindex type @subentry conversion
-If, for some reason, you need to force a number to be converted to a
-string, concatenate that number with the empty string, @code{""}.
-To force a string to be converted to a number, add zero to that string.
-A string is converted to a number by interpreting any numeric prefix
-of the string as numerals:
-@code{"2.5"} converts to 2.5, @code{"1e3"} converts to 1,000, and
@code{"25fix"}
-has a numeric value of 25.
-Strings that can't be interpreted as valid numbers convert to zero.
-
-@cindex @code{CONVFMT} variable
-The exact manner in which numbers are converted into strings is controlled
-by the @command{awk} predefined variable @code{CONVFMT} (@pxref{Built-in
Variables}).
-Numbers are converted using the @code{sprintf()} function
-with @code{CONVFMT} as the format
-specifier
-(@pxref{String Functions}).
-
-@code{CONVFMT}'s default value is @code{"%.6g"}, which creates a value with
-at most six significant digits. For some applications, you might want to
-change it to specify more precision.
-On most modern machines,
-17 digits is usually enough to capture a floating-point number's
-value exactly.@footnote{Pathological cases can require up to
-752 digits (!), but we doubt that you need to worry about this.}
-
-@cindex dark corner @subentry @code{CONVFMT} variable
-Strange results can occur if you set @code{CONVFMT} to a string that doesn't
-tell @code{sprintf()} how to format floating-point numbers in a useful way.
-For example, if you forget the @samp{%} in the format, @command{awk} converts
-all numbers to the same constant string.
-
-As a special case, if a number is an integer, then the result of converting
-it to a string is @emph{always} an integer, no matter what the value of
-@code{CONVFMT} may be. Given the following code fragment:
-
-@example
-CONVFMT = "%2.2f"
-a = 12
-b = a ""
-@end example
-
-@noindent
-@code{b} has the value @code{"12"}, not @code{"12.00"}.
-@value{DARKCORNER}
-
-@sidebar Pre-POSIX @command{awk} Used @code{OFMT} for String Conversion
-@cindex POSIX @command{awk} @subentry @code{OFMT} variable and
-@cindex @code{OFMT} variable
-@cindex portability @subentry new @command{awk} vs.@: old @command{awk}
-@cindex @command{awk} @subentry new vs.@: old @subentry @code{OFMT} variable
-Prior to the POSIX standard, @command{awk} used the value
-of @code{OFMT} for converting numbers to strings. @code{OFMT}
-specifies the output format to use when printing numbers with @code{print}.
-@code{CONVFMT} was introduced in order to separate the semantics of
-conversion from the semantics of printing. Both @code{CONVFMT} and
-@code{OFMT} have the same default value: @code{"%.6g"}. In the vast majority
-of cases, old @command{awk} programs do not change their behavior.
-@xref{Print} for more information on the @code{print} statement.
-@end sidebar
-
-@node Locale influences conversions
-@subsubsection Locales Can Influence Conversion
-
-Where you are can matter when it comes to converting between numbers and
-strings. The local character set and language---the @dfn{locale}---can
-affect numeric formats. In particular, for @command{awk} programs,
-it affects the decimal point character and the thousands-separator
-character. The @code{"C"} locale, and most English-language locales,
-use the period character (@samp{.}) as the decimal point and don't
-have a thousands separator. However, many (if not most) European and
-non-English locales use the comma (@samp{,}) as the decimal point
-character. European locales often use either a space or a period as
-the thousands separator, if they have one.
-
-@cindex dark corner @subentry locale's decimal point character
-The POSIX standard says that @command{awk} always uses the period as the
decimal
-point when reading the @command{awk} program source code, and for
-command-line variable assignments (@pxref{Other Arguments}). However,
-when interpreting input data, for @code{print} and @code{printf} output,
-and for number-to-string conversion, the local decimal point character
-is used. @value{DARKCORNER} In all cases, numbers in source code and
-in input data cannot have a thousands separator. Here are some examples
-indicating the difference in behavior, on a GNU/Linux system:
-
-@example
-$ @kbd{export POSIXLY_CORRECT=1} @ii{Force POSIX
behavior}
-$ @kbd{gawk 'BEGIN @{ printf "%g\n", 3.1415927 @}'}
-@print{} 3.14159
-$ @kbd{LC_ALL=en_DK.utf-8 gawk 'BEGIN @{ printf "%g\n", 3.1415927 @}'}
-@print{} 3,14159
-$ @kbd{echo 4,321 | gawk '@{ print $1 + 1 @}'}
-@print{} 5
-$ @kbd{echo 4,321 | LC_ALL=en_DK.utf-8 gawk '@{ print $1 + 1 @}'}
-@print{} 5,321
-@end example
-
-@noindent
-The @code{en_DK.utf-8} locale is for English in Denmark, where the comma acts
as
-the decimal point separator. In the normal @code{"C"} locale, @command{gawk}
-treats @samp{4,321} as 4, while in the Danish locale, it's treated
-as the full number including the fractional part, 4.321.
-
-@cindex POSIX mode
-@cindex @env{POSIXLY_CORRECT} environment variable
-@cindex environment variables @subentry @env{POSIXLY_CORRECT}
-Some earlier versions of @command{gawk} fully complied with this aspect
-of the standard. However, many users in non-English locales complained
-about this behavior, because their data used a period as the decimal
-point, so the default behavior was restored to use a period as the
-decimal point character. You can use the @option{--use-lc-numeric}
-option (@pxref{Options}) to force @command{gawk} to use the locale's
-decimal point character. (@command{gawk} also uses the locale's decimal
-point character when in POSIX mode, either via @option{--posix} or the
-@env{POSIXLY_CORRECT} environment variable, as shown previously.)
-
-@ref{table-locale-affects} describes the cases in which the locale's decimal
-point character is used and when a period is used. Some of these
-features have not been described yet.
-
-@float Table,table-locale-affects
-@caption{Locale decimal point versus a period}
-@multitable @columnfractions .15 .20 .45
-@headitem Feature @tab Default @tab @option{--posix} or
@option{--use-lc-numeric}
-@item @code{%'g} @tab Use locale @tab Use locale
-@item @code{%g} @tab Use period @tab Use locale
-@item Input @tab Use period @tab Use locale
-@item @code{strtonum()} @tab Use period @tab Use locale
-@end multitable
-@end float
-
-Finally, modern-day formal standards and the IEEE standard floating-point
-representation can have an unusual but important effect on the way
-@command{gawk} converts some special string values to numbers. The details
-are presented in @ref{POSIX Floating Point Problems}.
-
-@node All Operators
-@section Operators: Doing Something with Values
-
-This @value{SECTION} introduces the @dfn{operators} that make use
-of the values provided by constants and variables.
-
-@menu
-* Arithmetic Ops:: Arithmetic operations (@samp{+}, @samp{-},
- etc.)
-* Concatenation:: Concatenating strings.
-* Assignment Ops:: Changing the value of a variable or a field.
-* Increment Ops:: Incrementing the numeric value of a variable.
-@end menu
-
-@node Arithmetic Ops
-@subsection Arithmetic Operators
-@cindex arithmetic operators
-@cindex operators @subentry arithmetic
-@c @cindex addition
-@c @cindex subtraction
-@c @cindex multiplication
-@c @cindex division
-@c @cindex remainder
-@c @cindex quotient
-@c @cindex exponentiation
-
-The @command{awk} language uses the common arithmetic operators when
-evaluating expressions. All of these arithmetic operators follow normal
-precedence rules and work as you would expect them to.
-
-The following example uses a file named @file{grades}, which contains
-a list of student names as well as three test scores per student (it's
-a small class):
-
-@example
-Pat 100 97 58
-Sandy 84 72 93
-Chris 72 92 89
-@end example
-
-@noindent
-This program takes the file @file{grades} and prints the average
-of the scores:
-
-@example
-$ @kbd{awk '@{ sum = $2 + $3 + $4 ; avg = sum / 3}
-> @kbd{print $1, avg @}' grades}
-@print{} Pat 85
-@print{} Sandy 83
-@print{} Chris 84.3333
-@end example
-
-The following list provides the arithmetic operators in @command{awk},
-in order from the highest precedence to the lowest:
-
-@table @code
-@cindex common extensions @subentry @code{**} operator
-@cindex extensions @subentry common @subentry @code{**} operator
-@cindex POSIX @command{awk} @subentry arithmetic operators and
-@item @var{x} ^ @var{y}
-@itemx @var{x} ** @var{y}
-Exponentiation; @var{x} raised to the @var{y} power. @samp{2 ^ 3} has
-the value eight; the character sequence @samp{**} is equivalent to
-@samp{^}. @value{COMMONEXT}
-
-@item - @var{x}
-Negation.
-
-@item + @var{x}
-Unary plus; the expression is converted to a number.
-
-@item @var{x} * @var{y}
-Multiplication.
-
-@cindex troubleshooting @subentry division
-@cindex division
-@item @var{x} / @var{y}
-Division; because all numbers in @command{awk} are floating-point
-numbers, the result is @emph{not} rounded to an integer---@samp{3 / 4} has
-the value 0.75. (It is a common mistake, especially for C programmers,
-to forget that @emph{all} numbers in @command{awk} are floating point,
-and that division of integer-looking constants produces a real number,
-not an integer.)
-
-@item @var{x} % @var{y}
-Remainder; further discussion is provided in the text, just
-after this list.
-
-@item @var{x} + @var{y}
-Addition.
-
-@item @var{x} - @var{y}
-Subtraction.
-@end table
-
-Unary plus and minus have the same precedence,
-the multiplication operators all have the same precedence, and
-addition and subtraction have the same precedence.
-
-@cindex differences in @command{awk} and @command{gawk} @subentry trunc-mod
operation
-@cindex trunc-mod operation
-When computing the remainder of @samp{@var{x} % @var{y}},
-the quotient is rounded toward zero to an integer and
-multiplied by @var{y}. This result is subtracted from @var{x};
-this operation is sometimes known as ``trunc-mod.'' The following
-relation always holds:
-
-@example
-b * int(a / b) + (a % b) == a
-@end example
-
-One possibly undesirable effect of this definition of remainder is that
-@samp{@var{x} % @var{y}} is negative if @var{x} is negative. Thus:
-
-@example
--17 % 8 = -1
-@end example
-
-@noindent
-This definition is compliant with the POSIX standard, which says that the
@code{%}
-operator produces results equivalent to using the standard C
-@code{fmod()} function, and that function in turn works as just
-described.
-
-In other @command{awk} implementations, the signedness of the remainder
-may be machine-dependent.
-
-@cindex portability @subentry @code{**} operator and
-@cindex @code{*} (asterisk) @subentry @code{**} operator
-@cindex asterisk (@code{*}) @subentry @code{**} operator
-@quotation NOTE
-The POSIX standard only specifies the use of @samp{^}
-for exponentiation.
-For maximum portability, do not use the @samp{**} operator.
-@end quotation
-
-@node Concatenation
-@subsection String Concatenation
-@cindex Kernighan, Brian @subentry quotes
-@quotation
-@i{It seemed like a good idea at the time.}
-@author Brian Kernighan
-@end quotation
-
-@cindex string @subentry operators
-@cindex operators @subentry string
-@cindex concatenating
-There is only one string operation: concatenation. It does not have a
-specific operator to represent it. Instead, concatenation is performed by
-writing expressions next to one another, with no operator. For example:
-
-@example
-$ @kbd{awk '@{ print "Field number one: " $1 @}' mail-list}
-@print{} Field number one: Amelia
-@print{} Field number one: Anthony
-@dots{}
-@end example
-
-Without the space in the string constant after the @samp{:}, the line
-runs together. For example:
-
-@example
-$ @kbd{awk '@{ print "Field number one:" $1 @}' mail-list}
-@print{} Field number one:Amelia
-@print{} Field number one:Anthony
-@dots{}
-@end example
-
-@cindex troubleshooting @subentry string concatenation
-Because string concatenation does not have an explicit operator, it is
-often necessary to ensure that it happens at the right time by using
-parentheses to enclose the items to concatenate. For example,
-you might expect that the
-following code fragment concatenates @code{file} and @code{name}:
-
-@example
-file = "file"
-name = "name"
-print "something meaningful" > file name
-@end example
-
-@cindex Brian Kernighan's @command{awk}
-@cindex @command{mawk} utility
-@noindent
-This produces a syntax error with some versions of Unix
-@command{awk}.@footnote{It happens that BWK
-@command{awk}, @command{gawk}, and @command{mawk} all ``get it right,''
-but you should not rely on this.}
-It is necessary to use the following:
-
-@example
-print "something meaningful" > (file name)
-@end example
-
-@cindex order of evaluation, concatenation
-@cindex evaluation order @subentry concatenation
-@cindex side effects
-Parentheses should be used around concatenation in all but the
-most common contexts, such as on the righthand side of @samp{=}.
-Be careful about the kinds of expressions used in string concatenation.
-In particular, the order of evaluation of expressions used for concatenation
-is undefined in the @command{awk} language. Consider this example:
-
-@example
-BEGIN @{
- a = "don't"
- print (a " " (a = "panic"))
-@}
-@end example
-
-@noindent
-It is not defined whether the second assignment to @code{a} happens
-before or after the value of @code{a} is retrieved for producing the
-concatenated value. The result could be either @samp{don't panic},
-or @samp{panic panic}.
-@c see test/nasty.awk for a worse example
-
-The precedence of concatenation, when mixed with other operators, is often
-counter-intuitive. Consider this example:
-
-@ignore
-> To: bug-gnu-utils@@gnu.org
-> CC: arnold@@gnu.org
-> Subject: gawk 3.0.4 bug with {print -12 " " -24}
-> From: Russell Schulz <Russell_Schulz@locutus.ofB.ORG>
-> Date: Tue, 8 Feb 2000 19:56:08 -0700
->
-> gawk 3.0.4 on NT gives me:
->
-> prompt> cat bad.awk
-> BEGIN { print -12 " " -24; }
->
-> prompt> gawk -f bad.awk
-> -12-24
->
-> when I would expect
->
-> -12 -24
->
-> I have not investigated the source, or other implementations. The
-> bug is there on my NT and DOS versions 2.15.6 .
-@end ignore
-
-@example
-$ @kbd{awk 'BEGIN @{ print -12 " " -24 @}'}
-@print{} -12-24
-@end example
-
-This ``obviously'' is concatenating @minus{}12, a space, and @minus{}24.
-But where did the space disappear to?
-The answer lies in the combination of operator precedences and
-@command{awk}'s automatic conversion rules. To get the desired result,
-write the program this way:
-
-@example
-$ @kbd{awk 'BEGIN @{ print -12 " " (-24) @}'}
-@print{} -12 -24
-@end example
-
-This forces @command{awk} to treat the @samp{-} on the @samp{-24} as unary.
-Otherwise, it's parsed as follows:
-
-@display
- @minus{}12 (@code{"@ "} @minus{} 24)
-@result{} @minus{}12 (0 @minus{} 24)
-@result{} @minus{}12 (@minus{}24)
-@result{} @minus{}12@minus{}24
-@end display
-
-As mentioned earlier,
-when mixing concatenation with other operators, @emph{parenthesize}.
Otherwise,
-you're never quite sure what you'll get.
-
-@node Assignment Ops
-@subsection Assignment Expressions
-@cindex assignment operators
-@cindex operators @subentry assignment
-@cindex expressions @subentry assignment
-@cindex @code{=} (equals sign) @subentry @code{=} operator
-@cindex equals sign (@code{=}) @subentry @code{=} operator
-An @dfn{assignment} is an expression that stores a (usually different)
-value into a variable. For example, let's assign the value one to the variable
-@code{z}:
-
-@example
-z = 1
-@end example
-
-After this expression is executed, the variable @code{z} has the value one.
-Whatever old value @code{z} had before the assignment is forgotten.
-
-Assignments can also store string values. For example, the
-following stores
-the value @code{"this food is good"} in the variable @code{message}:
-
-@example
-thing = "food"
-predicate = "good"
-message = "this " thing " is " predicate
-@end example
-
-@noindent
-@cindex side effects @subentry assignment expressions
-This also illustrates string concatenation.
-The @samp{=} sign is called an @dfn{assignment operator}. It is the
-simplest assignment operator because the value of the righthand
-operand is stored unchanged.
-Most operators (addition, concatenation, and so on) have no effect
-except to compute a value. If the value isn't used, there's no reason to
-use the operator. An assignment operator is different; it does
-produce a value, but even if you ignore it, the assignment still
-makes itself felt through the alteration of the variable. We call this
-a @dfn{side effect}.
-
-@cindex lvalues/rvalues
-@cindex rvalues/lvalues
-@cindex assignment operators @subentry lvalues/rvalues
-@cindex operators @subentry assignment
-The lefthand operand of an assignment need not be a variable
-(@pxref{Variables}); it can also be a field
-(@pxref{Changing Fields}) or
-an array element (@pxref{Arrays}).
-These are all called @dfn{lvalues},
-which means they can appear on the lefthand side of an assignment operator.
-The righthand operand may be any expression; it produces the new value
-that the assignment stores in the specified variable, field, or array
-element. (Such values are called @dfn{rvalues}.)
-
-@cindex variables @subentry types of
-It is important to note that variables do @emph{not} have permanent types.
-A variable's type is simply the type of whatever value was last assigned
-to it. In the following program fragment, the variable
-@code{foo} has a numeric value at first, and a string value later on:
-
-@example
-@group
-foo = 1
-print foo
-@end group
-@group
-foo = "bar"
-print foo
-@end group
-@end example
-
-@noindent
-When the second assignment gives @code{foo} a string value, the fact that
-it previously had a numeric value is forgotten.
-
-String values that do not begin with a digit have a numeric value of
-zero. After executing the following code, the value of @code{foo} is five:
-
-@example
-foo = "a string"
-foo = foo + 5
-@end example
-
-@quotation NOTE
-Using a variable as a number and then later as a string
-can be confusing and is poor programming style. The previous two examples
-illustrate how @command{awk} works, @emph{not} how you should write your
-programs!
-@end quotation
-
-An assignment is an expression, so it has a value---the same value that
-is assigned. Thus, @samp{z = 1} is an expression with the value one.
-One consequence of this is that you can write multiple assignments together,
-such as:
-
-@example
-x = y = z = 5
-@end example
-
-@noindent
-This example stores the value five in all three variables
-(@code{x}, @code{y}, and @code{z}).
-It does so because the
-value of @samp{z = 5}, which is five, is stored into @code{y} and then
-the value of @samp{y = z = 5}, which is five, is stored into @code{x}.
-
-Assignments may be used anywhere an expression is called for. For
-example, it is valid to write @samp{x != (y = 1)} to set @code{y} to one,
-and then test whether @code{x} equals one. But this style tends to make
-programs hard to read; such nesting of assignments should be avoided,
-except perhaps in a one-shot program.
-
-@cindex @code{+} (plus sign) @subentry @code{+=} operator
-@cindex plus sign (@code{+}) @subentry @code{+=} operator
-Aside from @samp{=}, there are several other assignment operators that
-do arithmetic with the old value of the variable. For example, the
-operator @samp{+=} computes a new value by adding the righthand value
-to the old value of the variable. Thus, the following assignment adds
-five to the value of @code{foo}:
-
-@example
-foo += 5
-@end example
-
-@noindent
-This is equivalent to the following:
-
-@example
-foo = foo + 5
-@end example
-
-@noindent
-Use whichever makes the meaning of your program clearer.
-
-There are situations where using @samp{+=} (or any assignment operator)
-is @emph{not} the same as simply repeating the lefthand operand in the
-righthand expression. For example:
-
-@cindex Rankin, Pat
-@example
-@group
-# Thanks to Pat Rankin for this example
-BEGIN @{
- foo[rand()] += 5
- for (x in foo)
- print x, foo[x]
-@end group
-
-@group
- bar[rand()] = bar[rand()] + 5
- for (x in bar)
- print x, bar[x]
-@}
-@end group
-@end example
-
-@cindex operators @subentry assignment @subentry evaluation order
-@cindex assignment operators @subentry evaluation order
-@noindent
-The indices of @code{bar} are practically guaranteed to be different, because
-@code{rand()} returns different values each time it is called.
-(Arrays and the @code{rand()} function haven't been covered yet.
-@xref{Arrays},
-and
-@ifnotdocbook
-@pxref{Numeric Functions}
-@end ifnotdocbook
-@ifdocbook
-@ref{Numeric Functions}
-@end ifdocbook
-for more information.)
-This example illustrates an important fact about assignment
-operators: the lefthand expression is only evaluated @emph{once}.
-
-It is up to the implementation as to which expression is evaluated
-first, the lefthand or the righthand.
-Consider this example:
-
-@example
-i = 1
-a[i += 2] = i + 1
-@end example
-
-@noindent
-The value of @code{a[3]} could be either two or four.
-
-@ref{table-assign-ops} lists the arithmetic assignment operators. In each
-case, the righthand operand is an expression whose value is converted
-to a number.
-
-@cindex @code{-} (hyphen) @subentry @code{-=} operator
-@cindex hyphen (@code{-}) @subentry @code{-=} operator
-@cindex @code{*} (asterisk) @subentry @code{*=} operator
-@cindex asterisk (@code{*}) @subentry @code{*=} operator
-@cindex @code{/} (forward slash) @subentry @code{/=} operator
-@cindex forward slash (@code{/}) @subentry @code{/=} operator
-@cindex @code{%} (percent sign) @subentry @code{%=} operator
-@cindex percent sign (@code{%}) @subentry @code{%=} operator
-@cindex @code{^} (caret) @subentry @code{^=} operator
-@cindex caret (@code{^}) @subentry @code{^=} operator
-@cindex @code{*} (asterisk) @subentry @code{**=} operator
-@cindex asterisk (@code{*}) @subentry @code{**=} operator
-@float Table,table-assign-ops
-@caption{Arithmetic assignment operators}
-@multitable @columnfractions .30 .70
-@headitem Operator @tab Effect
-@item @var{lvalue} @code{+=} @var{increment} @tab Add @var{increment} to the
value of @var{lvalue}.
-@item @var{lvalue} @code{-=} @var{decrement} @tab Subtract @var{decrement}
from the value of @var{lvalue}.
-@item @var{lvalue} @code{*=} @var{coefficient} @tab Multiply the value of
@var{lvalue} by @var{coefficient}.
-@item @var{lvalue} @code{/=} @var{divisor} @tab Divide the value of
@var{lvalue} by @var{divisor}.
-@item @var{lvalue} @code{%=} @var{modulus} @tab Set @var{lvalue} to its
remainder by @var{modulus}.
-@cindex common extensions @subentry @code{**=} operator
-@cindex extensions @subentry common @subentry @code{**=} operator
-@cindex @command{awk} @subentry language, POSIX version
-@cindex POSIX @command{awk}
-@item @var{lvalue} @code{^=} @var{power} @tab Raise @var{lvalue} to the power
@var{power}.
-@item @var{lvalue} @code{**=} @var{power} @tab Raise @var{lvalue} to the power
@var{power}. @value{COMMONEXT}
-@end multitable
-@end float
-
-@cindex POSIX @command{awk} @subentry @code{**=} operator and
-@cindex portability @subentry @code{**=} operator and
-@quotation NOTE
-Only the @samp{^=} operator is specified by POSIX.
-For maximum portability, do not use the @samp{**=} operator.
-@end quotation
-
-@sidebar Syntactic Ambiguities Between @samp{/=} and Regular Expressions
-@cindex dark corner @subentry regexp constants @subentry @code{/=} operator and
-@cindex @code{/} (forward slash) @subentry @code{/=} operator @subentry vs.@:
@code{/=@dots{}/} regexp constant
-@cindex forward slash (@code{/}) @subentry @code{/=} operator @subentry vs.@:
@code{/=@dots{}/} regexp constant
-@cindex regexp constants @subentry @code{/=@dots{}/} @subentry @code{/=}
operator and
-
-@c derived from email from "Nelson H. F. Beebe" <beebe@math.utah.edu>
-@c Date: Mon, 1 Sep 1997 13:38:35 -0600 (MDT)
-
-@cindex dark corner @subentry @code{/=} operator vs.@: @code{/=@dots{}/}
regexp constant
-@cindex ambiguity, syntactic: @code{/=} operator vs.@: @code{/=@dots{}/}
regexp constant
-@cindex syntactic ambiguity: @code{/=} operator vs.@: @code{/=@dots{}/} regexp
constant
-@cindex @code{/=} operator vs.@: @code{/=@dots{}/} regexp constant
-There is a syntactic ambiguity between the @code{/=} assignment
-operator and regexp constants whose first character is an @samp{=}.
-@value{DARKCORNER}
-This is most notable in some commercial @command{awk} versions.
-For example:
-
-@example
-$ @kbd{awk /==/ /dev/null}
-@error{} awk: syntax error at source line 1
-@error{} context is
-@error{} >>> /= <<<
-@error{} awk: bailing out at source line 1
-@end example
-
-@noindent
-A workaround is:
-
-@example
-awk '/[=]=/' /dev/null
-@end example
-
-@command{gawk} does not have this problem; BWK @command{awk}
-and @command{mawk} also do not.
-@end sidebar
-
-@node Increment Ops
-@subsection Increment and Decrement Operators
-
-@cindex increment operators
-@cindex operators @subentry decrement/increment
-@dfn{Increment} and @dfn{decrement operators} increase or decrease the value of
-a variable by one. An assignment operator can do the same thing, so
-the increment operators add no power to the @command{awk} language; however,
they
-are convenient abbreviations for very common operations.
-
-@cindex side effects
-@cindex @code{+} (plus sign) @subentry @code{++} operator
-@cindex plus sign (@code{+}) @subentry @code{++} operator
-@cindex side effects @subentry decrement/increment operators
-The operator used for adding one is written @samp{++}. It can be used to
increment
-a variable either before or after taking its value.
-To @dfn{pre-increment} a variable @code{v}, write @samp{++v}. This adds
-one to the value of @code{v}---that new value is also the value of the
-expression. (The assignment expression @samp{v += 1} is completely equivalent.)
-Writing the @samp{++} after the variable specifies @dfn{post-increment}. This
-increments the variable value just the same; the difference is that the
-value of the increment expression itself is the variable's @emph{old}
-value. Thus, if @code{foo} has the value four, then the expression
@samp{foo++}
-has the value four, but it changes the value of @code{foo} to five.
-In other words, the operator returns the old value of the variable,
-but with the side effect of incrementing it.
-
-The post-increment @samp{foo++} is nearly the same as writing @samp{(foo
-+= 1) - 1}. It is not perfectly equivalent because all numbers in
-@command{awk} are floating point---in floating point, @samp{foo + 1 - 1} does
-not necessarily equal @code{foo}. But the difference is minute as
-long as you stick to numbers that are fairly small (less than
-@iftex
-@math{10^{12}}).
-@end iftex
-@ifinfo
-10e12).
-@end ifinfo
-@ifnottex
-@ifnotinfo
-10@sup{12}).
-@end ifnotinfo
-@end ifnottex
-
-@cindex @code{$} (dollar sign) @subentry incrementing fields and arrays
-@cindex dollar sign (@code{$}) @subentry incrementing fields and arrays
-Fields and array elements are incremented
-just like variables. (Use @samp{$(i++)} when you want to do a field reference
-and a variable increment at the same time. The parentheses are necessary
-because of the precedence of the field reference operator @samp{$}.)
-
-@cindex decrement operators
-The decrement operator @samp{--} works just like @samp{++}, except that
-it subtracts one instead of adding it. As with @samp{++}, it can be used
before
-the lvalue to pre-decrement or after it to post-decrement.
-Following is a summary of increment and decrement expressions:
-
-@table @code
-@cindex @code{+} (plus sign) @subentry @code{++} operator
-@cindex plus sign (@code{+}) @subentry @code{++} operator
-@item ++@var{lvalue}
-Increment @var{lvalue}, returning the new value as the
-value of the expression.
-
-@item @var{lvalue}++
-Increment @var{lvalue}, returning the @emph{old} value of @var{lvalue}
-as the value of the expression.
-
-@cindex @code{-} (hyphen) @subentry @code{--} operator
-@cindex hyphen (@code{-}) @subentry @code{--} operator
-@item --@var{lvalue}
-Decrement @var{lvalue}, returning the new value as the
-value of the expression.
-(This expression is
-like @samp{++@var{lvalue}}, but instead of adding, it subtracts.)
-
-@item @var{lvalue}--
-Decrement @var{lvalue}, returning the @emph{old} value of @var{lvalue}
-as the value of the expression.
-(This expression is
-like @samp{@var{lvalue}++}, but instead of adding, it subtracts.)
-@end table
-
-@sidebar Operator Evaluation Order
-@cindex precedence
-@cindex operators @subentry precedence of
-@cindex portability @subentry operators
-@cindex evaluation order
-@cindex Marx, Groucho
-@quotation
-@i{Doctor, it hurts when I do this!@*
-Then don't do that!}
-@author Groucho Marx
-@end quotation
-
-@noindent
-What happens for something like the following?
-
-@example
-b = 6
-print b += b++
-@end example
-
-@noindent
-Or something even stranger?
-
-@example
-b = 6
-b += ++b + b++
-print b
-@end example
-
-@cindex side effects
-In other words, when do the various side effects prescribed by the
-postfix operators (@samp{b++}) take effect?
-When side effects happen is @dfn{implementation-defined}.
-In other words, it is up to the particular version of @command{awk}.
-The result for the first example may be 12 or 13, and for the second, it
-may be 22 or 23.
-
-In short, doing things like this is not recommended and definitely
-not anything that you can rely upon for portability.
-You should avoid such things in your own programs.
-@c You'll sleep better at night and be able to look at yourself
-@c in the mirror in the morning.
-@end sidebar
-
-@node Truth Values and Conditions
-@section Truth Values and Conditions
-
-In certain contexts, expression values also serve as ``truth values''; i.e.,
-they determine what should happen next as the program runs. This
-@value{SECTION} describes how @command{awk} defines ``true'' and ``false''
-and how values are compared.
-
-@menu
-* Truth Values:: What is ``true'' and what is ``false''.
-* Typing and Comparison:: How variables acquire types and how this
- affects comparison of numbers and strings with
- @samp{<}, etc.
-* Boolean Ops:: Combining comparison expressions using boolean
- operators @samp{||} (``or''), @samp{&&}
- (``and'') and @samp{!} (``not'').
-* Conditional Exp:: Conditional expressions select between two
- subexpressions under control of a third
- subexpression.
-@end menu
-
-@node Truth Values
-@subsection True and False in @command{awk}
-@cindex truth values
-@cindex logical false/true
-@cindex false, logical
-@cindex true, logical
-
-@cindex null strings
-Many programming languages have a special representation for the concepts
-of ``true'' and ``false.'' Such languages usually use the special
-constants @code{true} and @code{false}, or perhaps their uppercase
-equivalents.
-However, @command{awk} is different.
-It borrows a very simple concept of true and
-false from C. In @command{awk}, any nonzero numeric value @emph{or} any
-nonempty string value is true. Any other value (zero or the null
-string, @code{""}) is false. The following program prints @samp{A strange
-truth value} three times:
-
-@example
-BEGIN @{
- if (3.1415927)
- print "A strange truth value"
- if ("Four Score And Seven Years Ago")
- print "A strange truth value"
- if (j = 57)
- print "A strange truth value"
-@}
-@end example
-
-@cindex dark corner @subentry @code{"0"} is actually true
-There is a surprising consequence of the ``nonzero or non-null'' rule:
-the string constant @code{"0"} is actually true, because it is non-null.
-@value{DARKCORNER}
-
-@node Typing and Comparison
-@subsection Variable Typing and Comparison Expressions
-@quotation
-@i{The Guide is definitive. Reality is frequently inaccurate.}
-@author Douglas Adams, @cite{The Hitchhiker's Guide to the Galaxy}
-@end quotation
-@c 2/2015: Antonio Colombo points out that this is really from
-@c The Restaurant at the End of the Universe. But I'm going to
-@c leave it alone.
-
-@cindex comparison expressions
-@cindex expressions @subentry comparison
-@cindex expressions, matching @seeentry{comparison expressions}
-@cindex matching @subentry expressions @seeentry{comparison expressions}
-@cindex relational operators @seeentry{comparison operators}
-@cindex operators, relational @seeentry{operators, comparison}
-@cindex variables @subentry types of @subentry comparison expressions and
-Unlike in other programming languages, in @command{awk} variables do not have a
-fixed type. Instead, they can be either a number or a string, depending
-upon the value that is assigned to them.
-We look now at how variables are typed, and how @command{awk}
-compares variables.
-
-@menu
-* Variable Typing:: String type versus numeric type.
-* Comparison Operators:: The comparison operators.
-* POSIX String Comparison:: String comparison with POSIX rules.
-@end menu
-
-@node Variable Typing
-@subsubsection String Type versus Numeric Type
-
-Scalar objects in @command{awk} (variables, array elements, and fields)
-are @emph{dynamically} typed. This means their type can change as the
-program runs, from @dfn{untyped} before any use,@footnote{@command{gawk}
-calls this @dfn{unassigned}, as the following example shows.} to string
-or number, and then from string to number or number to string, as the
-program progresses. (@command{gawk} also provides regexp-typed scalars,
-but let's ignore that for now; @pxref{Strong Regexp Constants}.)
-
-You can't do much with untyped variables, other than tell that they
-are untyped. The following program tests @code{a} against @code{""}
-and @code{0}; the test succeeds when @code{a} has never been assigned
-a value. It also uses the built-in @code{typeof()} function
-(not presented yet; @pxref{Type Functions}) to show @code{a}'s type:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print (a == "" && a == 0 ?}
-> @kbd{"a is untyped" : "a has a type!") ; print typeof(a) @}'}
-@print{} a is untyped
-@print{} unassigned
-@end example
-
-A scalar has numeric type when assigned a numeric value,
-such as from a numeric constant, or from another scalar
-with numeric type:
-
-@example
-$ @kbd{gawk 'BEGIN @{ a = 42 ; print typeof(a)}
-> @kbd{b = a ; print typeof(b) @}'}
-number
-number
-@end example
-
-Similarly, a scalar has string type when assigned a string
-value, such as from a string constant, or from another scalar
-with string type:
-
-@example
-$ @kbd{gawk 'BEGIN @{ a = "forty two" ; print typeof(a)}
-> @kbd{b = a ; print typeof(b) @}'}
-string
-string
-@end example
-
-So far, this is all simple and straightforward. What happens, though,
-when @command{awk} has to process data from a user? Let's start with
-field data. What should the following command produce as output?
-
-@example
-echo hello | awk '@{ printf("%s %s < 42\n", $1,
- ($1 < 42 ? "is" : "is not")) @}'
-@end example
-
-@noindent
-Since @samp{hello} is alphabetic data, @command{awk} can only do a string
-comparison. Internally, it converts @code{42} into @code{"42"} and compares
-the two string values @code{"hello"} and @code{"42"}. Here's the result:
-
-@example
-$ @kbd{echo hello | awk '@{ printf("%s %s < 42\n", $1,}
-> @kbd{ ($1 < 42 ? "is" : "is not")) @}'}
-@print{} hello is not < 42
-@end example
-
-However, what happens when data from a user @emph{looks like} a number?
-On the one hand, in reality, the input data consists of characters, not
-binary numeric
-values. But, on the other hand, the data looks numeric, and @command{awk}
-really ought to treat it as such. And indeed, it does:
-
-@example
-$ @kbd{echo 37 | awk '@{ printf("%s %s < 42\n", $1,}
-> @kbd{ ($1 < 42 ? "is" : "is not")) @}'}
-@print{} 37 is < 42
-@end example
-
-Here are the rules for when @command{awk}
-treats data as a number, and for when it treats data as a string.
-
-@cindex numeric @subentry strings
-@cindex strings @subentry numeric
-@cindex POSIX @command{awk} @subentry numeric strings and
-The POSIX standard uses the term @dfn{numeric string} for input data that
-looks numeric. The @samp{37} in the previous example is a numeric string.
-So what is the type of a numeric string? Answer: numeric.
-
-The type of a variable is important because the types of two variables
-determine how they are compared.
-Variable typing follows these definitions and rules:
-
-@itemize @value{BULLET}
-@item
-A numeric constant or the result of a numeric operation has the @dfn{numeric}
-attribute.
-
-@item
-A string constant or the result of a string operation has the @dfn{string}
-attribute.
-
-@item
-Fields, @code{getline} input, @code{FILENAME}, @code{ARGV} elements,
-@code{ENVIRON} elements, and the elements of an array created by
-@code{match()}, @code{split()}, and @code{patsplit()} that are numeric
-strings have the @dfn{strnum} attribute.@footnote{Thus, a POSIX
-numeric string and @command{gawk}'s strnum are the same thing.}
-Otherwise, they have
-the @dfn{string} attribute. Uninitialized variables also have the
-@dfn{strnum} attribute.
-
-@item
-Attributes propagate across assignments but are not changed by
-any use.
-@c (Although a use may cause the entity to acquire an additional
-@c value such that it has both a numeric and string value, this leaves the
-@c attribute unchanged.)
-@c This is important but not relevant
-@end itemize
-
-The last rule is particularly important. In the following program,
-@code{a} has numeric type, even though it is later used in a string
-operation:
-
-@example
-BEGIN @{
- a = 12.345
- b = a " is a cute number"
- print b
-@}
-@end example
-
-When two operands are compared, either string comparison or numeric comparison
-may be used. This depends upon the attributes of the operands, according to the
-following symmetric matrix:
-
-@c thanks to Karl Berry, kb@cs.umb.edu, for major help with TeX tables
-@tex
-\centerline{
-\vbox{\bigskip % space above the table (about 1 linespace)
-% Because we have vertical rules, we can't let TeX insert interline space
-% in its usual way.
-\offinterlineskip
-%
-% Define the table template. & separates columns, and \cr ends the
-% template (and each row). # is replaced by the text of that entry on
-% each row. The template for the first column breaks down like this:
-% \strut -- a way to make each line have the height and depth
-% of a normal line of type, since we turned off interline spacing.
-% \hfil -- infinite glue; has the effect of right-justifying in this case.
-% # -- replaced by the text (for instance, `STRNUM', in the last row).
-% \quad -- about the width of an `M'. Just separates the columns.
-%
-% The second column (\vrule#) is what generates the vertical rule that
-% spans table rows.
-%
-% The doubled && before the next entry means `repeat the following
-% template as many times as necessary on each line' -- in our case, twice.
-%
-% The template itself, \quad#\hfil, left-justifies with a little space before.
-%
-\halign{\strut\hfil#\quad&\vrule#&&\quad#\hfil\cr
- &&STRING &NUMERIC &STRNUM\cr
-% The \omit tells TeX to skip inserting the template for this column on
-% this particular row. In this case, we only want a little extra space
-% to separate the heading row from the rule below it. the depth 2pt --
-% `\vrule depth 2pt' is that little space.
-\omit &depth 2pt\cr
-% This is the horizontal rule below the heading. Since it has nothing to
-% do with the columns of the table, we use \noalign to get it in there.
-\noalign{\hrule}
-% Like above, this time a little more space.
-\omit &depth 4pt\cr
-% The remaining rows have nothing special about them.
-STRING &&string &string &string\cr
-NUMERIC &&string &numeric &numeric\cr
-STRNUM &&string &numeric &numeric\cr
-}}}
-@end tex
-@ifnottex
-@ifnotdocbook
-@verbatim
- +----------------------------------------------
- | STRING NUMERIC STRNUM
---------+----------------------------------------------
- |
-STRING | string string string
- |
-NUMERIC | string numeric numeric
- |
-STRNUM | string numeric numeric
---------+----------------------------------------------
-@end verbatim
-@end ifnotdocbook
-@end ifnottex
-@docbook
-<informaltable>
-<tgroup cols="4">
-<colspec colname="1" align="left"/>
-<colspec colname="2" align="left"/>
-<colspec colname="3" align="left"/>
-<colspec colname="4" align="left"/>
-<thead>
-<row>
-<entry/>
-<entry>STRING</entry>
-<entry>NUMERIC</entry>
-<entry>STRNUM</entry>
-</row>
-</thead>
-
-<tbody>
-<row>
-<entry><emphasis role="bold">STRING</emphasis></entry>
-<entry>string</entry>
-<entry>string</entry>
-<entry>string</entry>
-</row>
-
-<row>
-<entry><emphasis role="bold">NUMERIC</emphasis></entry>
-<entry>string</entry>
-<entry>numeric</entry>
-<entry>numeric</entry>
-</row>
-
-<row>
-<entry><emphasis role="bold">STRNUM</emphasis></entry>
-<entry>string</entry>
-<entry>numeric</entry>
-<entry>numeric</entry>
-</row>
-
-</tbody>
-</tgroup>
-</informaltable>
-
-@end docbook
-
-The basic idea is that user input that looks numeric---and @emph{only}
-user input---should be treated as numeric, even though it is actually
-made of characters and is therefore also a string.
-Thus, for example, the string constant @w{@code{" +3.14"}},
-when it appears in program source code,
-is a string---even though it looks numeric---and
-is @emph{never} treated as a number for comparison
-purposes.
-
-In short, when one operand is a ``pure'' string, such as a string
-constant, then a string comparison is performed. Otherwise, a
-numeric comparison is performed.
-(The primary difference between a number and a strnum is that
-for strnums @command{gawk} preserves the original string value that
-the scalar had when it came in.)
-
-This point bears additional emphasis:
-Input that looks numeric @emph{is} numeric.
-All other input is treated as strings.
-
-Thus, the six-character input string @w{@samp{ +3.14}} receives the
-strnum attribute. In contrast, the eight characters
-@w{@code{" +3.14"}} appearing in program text comprise a string constant.
-The following examples print @samp{1} when the comparison between
-the two different constants is true, and @samp{0} otherwise:
-
-@c 22.9.2014: Tested with mawk and BWK awk, got same results.
-@example
-$ @kbd{echo ' +3.14' | awk '@{ print($0 == " +3.14") @}'} @ii{True}
-@print{} 1
-$ @kbd{echo ' +3.14' | awk '@{ print($0 == "+3.14") @}'} @ii{False}
-@print{} 0
-$ @kbd{echo ' +3.14' | awk '@{ print($0 == "3.14") @}'} @ii{False}
-@print{} 0
-$ @kbd{echo ' +3.14' | awk '@{ print($0 == 3.14) @}'} @ii{True}
-@print{} 1
-$ @kbd{echo ' +3.14' | awk '@{ print($1 == " +3.14") @}'} @ii{False}
-@print{} 0
-$ @kbd{echo ' +3.14' | awk '@{ print($1 == "+3.14") @}'} @ii{True}
-@print{} 1
-$ @kbd{echo ' +3.14' | awk '@{ print($1 == "3.14") @}'} @ii{False}
-@print{} 0
-$ @kbd{echo ' +3.14' | awk '@{ print($1 == 3.14) @}'} @ii{True}
-@print{} 1
-@end example
-
-You can see the type of an input field (or other user input)
-using @code{typeof()}:
-
-@example
-$ @kbd{echo hello 37 | gawk '@{ print typeof($1), typeof($2) @}'}
-@print{} string strnum
-@end example
-
-@node Comparison Operators
-@subsubsection Comparison Operators
-@cindex operators @subentry comparison
-
-@dfn{Comparison expressions} compare strings or numbers for
-relationships such as equality. They are written using @dfn{relational
-operators}, which are a superset of those in C.
-@ref{table-relational-ops} describes them.
-
-@cindex @code{<} (left angle bracket) @subentry @code{<} operator
-@cindex left angle bracket (@code{<}) @subentry @code{<} operator
-@cindex @code{<} (left angle bracket) @subentry @code{<=} operator
-@cindex left angle bracket (@code{<}) @subentry @code{<=} operator
-@cindex @code{>} (right angle bracket) @subentry @code{>=} operator
-@cindex right angle bracket (@code{>}) @subentry @code{>=} operator
-@cindex @code{>} (right angle bracket) @subentry @code{>} operator
-@cindex right angle bracket (@code{>}) @subentry @code{>} operator
-@cindex @code{=} (equals sign) @subentry @code{==} operator
-@cindex equals sign (@code{=}) @subentry @code{==} operator
-@cindex @code{!} (exclamation point) @subentry @code{!=} operator
-@cindex exclamation point (@code{!}) @subentry @code{!=} operator
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-@cindex @code{in} operator
-@float Table,table-relational-ops
-@caption{Relational operators}
-@multitable @columnfractions .25 .75
-@headitem Expression @tab Result
-@item @var{x} @code{<} @var{y} @tab True if @var{x} is less than @var{y}
-@item @var{x} @code{<=} @var{y} @tab True if @var{x} is less than or equal to
@var{y}
-@item @var{x} @code{>} @var{y} @tab True if @var{x} is greater than @var{y}
-@item @var{x} @code{>=} @var{y} @tab True if @var{x} is greater than or equal
to @var{y}
-@item @var{x} @code{==} @var{y} @tab True if @var{x} is equal to @var{y}
-@item @var{x} @code{!=} @var{y} @tab True if @var{x} is not equal to @var{y}
-@item @var{x} @code{~} @var{y} @tab True if the string @var{x} matches the
regexp denoted by @var{y}
-@item @var{x} @code{!~} @var{y} @tab True if the string @var{x} does not match
the regexp denoted by @var{y}
-@item @var{subscript} @code{in} @var{array} @tab True if the array @var{array}
has an element with the subscript @var{subscript}
-@end multitable
-@end float
-
-Comparison expressions have the value one if true and zero if false.
-When comparing operands of mixed types, numeric operands are converted
-to strings using the value of @code{CONVFMT}
-(@pxref{Conversion}).
-
-Strings are compared
-by comparing the first character of each, then the second character of each,
-and so on. Thus, @code{"10"} is less than @code{"9"}. If there are two
-strings where one is a prefix of the other, the shorter string is less than
-the longer one. Thus, @code{"abc"} is less than @code{"abcd"}.
-
-@cindex troubleshooting @subentry @code{==} operator
-It is very easy to accidentally mistype the @samp{==} operator and
-leave off one of the @samp{=} characters. The result is still valid
-@command{awk} code, but the program does not do what is intended:
-
-@example
-@group
-if (a = b) # oops! should be a == b
- @dots{}
-else
- @dots{}
-@end group
-@end example
-
-@noindent
-Unless @code{b} happens to be zero or the null string, the @code{if}
-part of the test always succeeds. Because the operators are
-so similar, this kind of error is very difficult to spot when
-scanning the source code.
-
-The following list of expressions illustrates the kinds of comparisons
-@command{awk} performs, as well as what the result of each comparison is:
-
-@table @code
-@item 1.5 <= 2.0
-Numeric comparison (true)
-
-@item "abc" >= "xyz"
-String comparison (false)
-
-@item 1.5 != " +2"
-String comparison (true)
-
-@item "1e2" < "3"
-String comparison (true)
-
-@item a = 2; b = "2"
-@itemx a == b
-String comparison (true)
-
-@item a = 2; b = " +2"
-@itemx a == b
-String comparison (false)
-@end table
-
-In this example:
-
-@example
-$ @kbd{echo 1e2 3 | awk '@{ print ($1 < $2) ? "true" : "false" @}'}
-@print{} false
-@end example
-
-@cindex comparison expressions @subentry string vs.@: regexp
-@c @cindex string comparison vs.@: regexp comparison
-@c @cindex regexp comparison vs.@: string comparison
-@noindent
-the result is @samp{false} because both @code{$1} and @code{$2}
-are user input. They are numeric strings---therefore both have
-the strnum attribute, dictating a numeric comparison.
-The purpose of the comparison rules and the use of numeric strings is
-to attempt to produce the behavior that is ``least surprising,'' while
-still ``doing the right thing.''
-
-String comparisons and regular expression comparisons are very different.
-For example:
-
-@example
-x == "foo"
-@end example
-
-@noindent
-has the value one, or is true if the variable @code{x}
-is precisely @samp{foo}. By contrast:
-
-@example
-x ~ /foo/
-@end example
-
-@noindent
-has the value one if @code{x} contains @samp{foo}, such as
-@code{"Oh, what a fool am I!"}.
-
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-The righthand operand of the @samp{~} and @samp{!~} operators may be
-either a regexp constant (@code{/}@dots{}@code{/}) or an ordinary
-expression. In the latter case, the value of the expression as a string is
used as a
-dynamic regexp (@pxref{Regexp Usage}; also
-@pxref{Computed Regexps}).
-
-@cindex @command{awk} @subentry regexp constants and
-@cindex regexp constants
-A constant regular
-expression in slashes by itself is also an expression.
-@code{/@var{regexp}/} is an abbreviation for the following comparison
expression:
-
-@example
-$0 ~ /@var{regexp}/
-@end example
-
-One special place where @code{/foo/} is @emph{not} an abbreviation for
-@samp{$0 ~ /foo/} is when it is the righthand operand of @samp{~} or
-@samp{!~}.
-@xref{Using Constant Regexps},
-where this is discussed in more detail.
-
-@node POSIX String Comparison
-@subsubsection String Comparison Based on Locale Collating Order
-
-The POSIX standard used to say that all string comparisons are
-performed based on the locale's @dfn{collating order}. This
-is the order in which characters sort, as defined by the locale
-(for more discussion, @pxref{Locales}). This order is usually very
-different from the results obtained when doing straight byte-by-byte
-comparison.@footnote{Technically, string comparison is supposed to behave
-the same way as if the strings were compared with the C @code{strcoll()}
-function.}
-
-@cindex POSIX mode
-Because this behavior differs considerably from existing practice,
-@command{gawk} only implemented it when in POSIX mode (@pxref{Options}).
-Here is an example to illustrate the difference, in an @code{en_US.UTF-8}
-locale:
-
-@example
-$ @kbd{gawk 'BEGIN @{ printf("ABC < abc = %s\n",}
-> @kbd{("ABC" < "abc" ? "TRUE" : "FALSE")) @}'}
-@print{} ABC < abc = TRUE
-$ @kbd{gawk --posix 'BEGIN @{ printf("ABC < abc = %s\n",}
-> @kbd{("ABC" < "abc" ? "TRUE" : "FALSE")) @}'}
-@print{} ABC < abc = FALSE
-@end example
-
-Fortunately, as of August 2016, comparison based on locale
-collating order is no longer required for the @code{==} and @code{!=}
-operators.@footnote{See @uref{http://austingroupbugs.net/view.php?id=1070,
-the Austin Group website}.} However, comparison based on locales is still
-required for @code{<}, @code{<=}, @code{>}, and @code{>=}. POSIX thus
-recommends as follows:
-
-@quotation
-Since the @code{==} operator checks whether strings are identical,
-not whether they collate equally, applications needing to check whether
-strings collate equally can use:
-
-@example
-a <= b && a >= b
-@end example
-@end quotation
-
-@cindex POSIX mode
-As of @value{PVERSION} 4.2, @command{gawk} continues to use locale
-collating order for @code{<}, @code{<=}, @code{>}, and @code{>=} only
-in POSIX mode.
-
-@ignore
-References: http://austingroupbugs.net/view.php?id=963
-and http://austingroupbugs.net/view.php?id=1070.
-@end ignore
-
-@node Boolean Ops
-@subsection Boolean Expressions
-@cindex and Boolean-logic operator
-@cindex or Boolean-logic operator
-@cindex not Boolean-logic operator
-@cindex expressions @subentry Boolean
-@cindex Boolean expressions
-@cindex operators, Boolean @seeentry{Boolean expressions}
-@cindex Boolean operators @seeentry{Boolean expressions}
-@cindex logical operators @seeentry{Boolean expressions}
-@cindex operators, logical @seeentry{Boolean expressions}
-
-A @dfn{Boolean expression} is a combination of comparison expressions or
-matching expressions, using the Boolean operators ``or''
-(@samp{||}), ``and'' (@samp{&&}), and ``not'' (@samp{!}), along with
-parentheses to control nesting. The truth value of the Boolean expression is
-computed by combining the truth values of the component expressions.
-Boolean expressions are also referred to as @dfn{logical expressions}.
-The terms are equivalent.
-
-Boolean expressions can be used wherever comparison and matching
-expressions can be used. They can be used in @code{if}, @code{while},
-@code{do}, and @code{for} statements
-(@pxref{Statements}).
-They have numeric values (one if true, zero if false) that come into play
-if the result of the Boolean expression is stored in a variable or
-used in arithmetic.
-
-In addition, every Boolean expression is also a valid pattern, so
-you can use one as a pattern to control the execution of rules.
-The Boolean operators are:
-
-@table @code
-@item @var{boolean1} && @var{boolean2}
-True if both @var{boolean1} and @var{boolean2} are true. For example,
-the following statement prints the current input record if it contains
-both @samp{edu} and @samp{li}:
-
-@example
-if ($0 ~ /edu/ && $0 ~ /li/) print
-@end example
-
-@cindex side effects @subentry Boolean operators
-The subexpression @var{boolean2} is evaluated only if @var{boolean1}
-is true. This can make a difference when @var{boolean2} contains
-expressions that have side effects. In the case of @samp{$0 ~ /foo/ &&
-($2 == bar++)}, the variable @code{bar} is not incremented if there is
-no substring @samp{foo} in the record.
-
-@item @var{boolean1} || @var{boolean2}
-True if at least one of @var{boolean1} or @var{boolean2} is true.
-For example, the following statement prints all records in the input
-that contain @emph{either} @samp{edu} or
-@samp{li}:
-
-@example
-if ($0 ~ /edu/ || $0 ~ /li/) print
-@end example
-
-The subexpression @var{boolean2} is evaluated only if @var{boolean1}
-is false. This can make a difference when @var{boolean2} contains
-expressions that have side effects.
-(Thus, this test never really distinguishes records that contain both
-@samp{edu} and @samp{li}---as soon as @samp{edu} is matched,
-the full test succeeds.)
-
-@item ! @var{boolean}
-True if @var{boolean} is false. For example,
-the following program prints @samp{no home!} in
-the unusual event that the @env{HOME} environment
-variable is not defined:
-
-@example
-BEGIN @{ if (! ("HOME" in ENVIRON))
- print "no home!" @}
-@end example
-
-(The @code{in} operator is described in
-@ref{Reference to Elements}.)
-@end table
-
-@cindex short-circuit operators
-@cindex operators @subentry short-circuit
-@cindex @code{&} (ampersand) @subentry @code{&&} operator
-@cindex ampersand (@code{&}) @subentry @code{&&} operator
-@cindex @code{|} (vertical bar) @subentry @code{||} operator
-@cindex vertical bar (@code{|}) @subentry @code{||} operator
-The @samp{&&} and @samp{||} operators are called @dfn{short-circuit}
-operators because of the way they work. Evaluation of the full expression
-is ``short-circuited'' if the result can be determined partway through
-its evaluation.
-
-@cindex line continuations
-Statements that end with @samp{&&} or @samp{||} can be continued simply
-by putting a newline after them. But you cannot put a newline in front
-of either of these operators without using backslash continuation
-(@pxref{Statements/Lines}).
-
-@cindex @code{!} (exclamation point) @subentry @code{!} operator
-@cindex exclamation point (@code{!}) @subentry @code{!} operator
-@cindex newlines
-@cindex variables @subentry flag
-@cindex flag variables
-The actual value of an expression using the @samp{!} operator is
-either one or zero, depending upon the truth value of the expression it
-is applied to.
-The @samp{!} operator is often useful for changing the sense of a flag
-variable from false to true and back again. For example, the following
-program is one way to print lines in between special bracketing lines:
-
-@example
-$1 == "START" @{ interested = ! interested; next @}
-interested @{ print @}
-$1 == "END" @{ interested = ! interested; next @}
-@end example
-
-@noindent
-The variable @code{interested}, as with all @command{awk} variables, starts
-out initialized to zero, which is also false. When a line is seen whose
-first field is @samp{START}, the value of @code{interested} is toggled
-to true, using @samp{!}. The next rule prints lines as long as
-@code{interested} is true. When a line is seen whose first field is
-@samp{END}, @code{interested} is toggled back to false.@footnote{This
-program has a bug; it prints lines starting with @samp{END}. How
-would you fix it?}
-
-@ignore
-Scott Deifik points out that this program isn't robust against
-bogus input data, but the point is to illustrate the use of `!',
-so we'll leave well enough alone.
-@end ignore
-
-Most commonly, the @samp{!} operator is used in the conditions of
-@code{if} and @code{while} statements, where it often makes more
-sense to phrase the logic in the negative:
-
-@example
-if (! @var{some condition} || @var{some other condition}) @{
- @var{@dots{} do whatever processing @dots{}}
-@}
-@end example
-
-@cindex @code{next} statement
-@quotation NOTE
-The @code{next} statement is discussed in
-@ref{Next Statement}.
-@code{next} tells @command{awk} to skip the rest of the rules, get the
-next record, and start processing the rules over again at the top.
-The reason it's there is to avoid printing the bracketing
-@samp{START} and @samp{END} lines.
-@end quotation
-
-@node Conditional Exp
-@subsection Conditional Expressions
-@cindex conditional expressions
-@cindex expressions @subentry conditional
-@cindex expressions @subentry selecting
-
-A @dfn{conditional expression} is a special kind of expression that has
-three operands. It allows you to use one expression's value to select
-one of two other expressions.
-The conditional expression in @command{awk} is the same as in the C
-language, as shown here:
-
-@example
-@var{selector} ? @var{if-true-exp} : @var{if-false-exp}
-@end example
-
-@noindent
-There are three subexpressions. The first, @var{selector}, is always
-computed first. If it is ``true'' (not zero or not null), then
-@var{if-true-exp} is computed next, and its value becomes the value of
-the whole expression. Otherwise, @var{if-false-exp} is computed next,
-and its value becomes the value of the whole expression.
-For example, the following expression produces the absolute value of @code{x}:
-
-@example
-x >= 0 ? x : -x
-@end example
-
-@cindex side effects @subentry conditional expressions
-Each time the conditional expression is computed, only one of
-@var{if-true-exp} and @var{if-false-exp} is used; the other is ignored.
-This is important when the expressions have side effects. For example,
-this conditional expression examines element @code{i} of either array
-@code{a} or array @code{b}, and increments @code{i}:
-
-@example
-x == y ? a[i++] : b[i++]
-@end example
-
-@noindent
-This is guaranteed to increment @code{i} exactly once, because each time
-only one of the two increment expressions is executed
-and the other is not.
-@xref{Arrays},
-for more information about arrays.
-
-@cindex differences in @command{awk} and @command{gawk} @subentry line
continuations
-@cindex line continuations @subentry @command{gawk}
-@cindex @command{gawk} @subentry line continuation in
-As a minor @command{gawk} extension,
-a statement that uses @samp{?:} can be continued simply
-by putting a newline after either character.
-However, putting a newline in front
-of either character does not work without using backslash continuation
-(@pxref{Statements/Lines}).
-If @option{--posix} is specified
-(@pxref{Options}), this extension is disabled.
-
-@node Function Calls
-@section Function Calls
-@cindex function calls
-
-A @dfn{function} is a name for a particular calculation.
-This enables you to
-ask for it by name at any point in the program. For
-example, the function @code{sqrt()} computes the square root of a number.
-
-@cindex functions @subentry built-in
-A fixed set of functions are @dfn{built in}, which means they are
-available in every @command{awk} program. The @code{sqrt()} function is one
-of these. @xref{Built-in} for a list of built-in
-functions and their descriptions. In addition, you can define
-functions for use in your program.
-@xref{User-defined}
-for instructions on how to do this.
-Finally, @command{gawk} lets you write functions in C or C++
-that may be called from your program (@pxref{Dynamic Extensions}).
-
-@cindex arguments @subentry in function calls
-The way to use a function is with a @dfn{function call} expression,
-which consists of the function name followed immediately by a list of
-@dfn{arguments} in parentheses. The arguments are expressions that
-provide the raw materials for the function's calculations.
-When there is more than one argument, they are separated by commas. If
-there are no arguments, just write @samp{()} after the function name.
-The following examples show function calls with and without arguments:
-
-@example
-sqrt(x^2 + y^2) @ii{one argument}
-atan2(y, x) @ii{two arguments}
-rand() @ii{no arguments}
-@end example
-
-@cindex troubleshooting @subentry function call syntax
-@quotation CAUTION
-Do not put any space between the function name and the opening parenthesis!
-A user-defined function name looks just like the name of a
-variable---a space would make the expression look like concatenation of
-a variable with an expression inside parentheses.
-With built-in functions, space before the parenthesis is harmless, but
-it is best not to get into the habit of using space to avoid mistakes
-with user-defined functions.
-@end quotation
-
-Each function expects a particular number
-of arguments. For example, the @code{sqrt()} function must be called with
-a single argument, the number of which to take the square root:
-
-@example
-sqrt(@var{argument})
-@end example
-
-Some of the built-in functions have one or
-more optional arguments.
-If those arguments are not supplied, the functions
-use a reasonable default value.
-@xref{Built-in} for full details. If arguments
-are omitted in calls to user-defined functions, then those arguments are
-treated as local variables. Such local variables act like the
-empty string if referenced where a string value is required,
-and like zero if referenced where a numeric value is required
-(@pxref{User-defined}).
-
-As an advanced feature, @command{gawk} provides indirect function calls,
-which is a way to choose the function to call at runtime, instead of
-when you write the source code to your program. We defer discussion of
-this feature until later; see @ref{Indirect Calls}.
-
-@cindex side effects @subentry function calls
-Like every other expression, the function call has a value, often
-called the @dfn{return value}, which is computed by the function
-based on the arguments you give it. In this example, the return value
-of @samp{sqrt(@var{argument})} is the square root of @var{argument}.
-The following program reads numbers, one number per line, and prints
-the square root of each one:
-
-@example
-$ @kbd{awk '@{ print "The square root of", $1, "is", sqrt($1) @}'}
-@kbd{1}
-@print{} The square root of 1 is 1
-@kbd{3}
-@print{} The square root of 3 is 1.73205
-@kbd{5}
-@print{} The square root of 5 is 2.23607
-@kbd{Ctrl-d}
-@end example
-
-A function can also have side effects, such as assigning
-values to certain variables or doing I/O.
-This program shows how the @code{match()} function
-(@pxref{String Functions})
-changes the variables @code{RSTART} and @code{RLENGTH}:
-
-@example
-@{
- if (match($1, $2))
- print RSTART, RLENGTH
- else
- print "no match"
-@}
-@end example
-
-@noindent
-Here is a sample run:
-
-@example
-$ @kbd{awk -f matchit.awk}
-@kbd{aaccdd c+}
-@print{} 3 2
-@kbd{foo bar}
-@print{} no match
-@kbd{abcdefg e}
-@print{} 5 1
-@end example
-
-@node Precedence
-@section Operator Precedence (How Operators Nest)
-@cindex precedence
-@cindex operators @subentry precedence of
-
-@dfn{Operator precedence} determines how operators are grouped when
-different operators appear close by in one expression. For example,
-@samp{*} has higher precedence than @samp{+}; thus, @samp{a + b * c}
-means to multiply @code{b} and @code{c}, and then add @code{a} to the
-product (i.e., @samp{a + (b * c)}).
-
-The normal precedence of the operators can be overruled by using parentheses.
-Think of the precedence rules as saying where the
-parentheses are assumed to be. In
-fact, it is wise to always use parentheses whenever there is an unusual
-combination of operators, because other people who read the program may
-not remember what the precedence is in this case.
-Even experienced programmers occasionally forget the exact rules,
-which leads to mistakes.
-Explicit parentheses help prevent
-any such mistakes.
-
-When operators of equal precedence are used together, the leftmost
-operator groups first, except for the assignment, conditional, and
-exponentiation operators, which group in the opposite order.
-Thus, @samp{a - b + c} groups as @samp{(a - b) + c} and
-@samp{a = b = c} groups as @samp{a = (b = c)}.
-
-Normally the precedence of prefix unary operators does not matter,
-because there is only one way to interpret
-them: innermost first. Thus, @samp{$++i} means @samp{$(++i)} and
-@samp{++$x} means @samp{++($x)}. However, when another operator follows
-the operand, then the precedence of the unary operators can matter.
-@samp{$x^2} means @samp{($x)^2}, but @samp{-x^2} means
-@samp{-(x^2)}, because @samp{-} has lower precedence than @samp{^},
-whereas @samp{$} has higher precedence.
-Also, operators cannot be combined in a way that violates the
-precedence rules; for example, @samp{$$0++--} is not a valid
-expression because the first @samp{$} has higher precedence than the
-@samp{++}; to avoid the problem the expression can be rewritten as
-@samp{$($0++)--}.
-
-This list presents @command{awk}'s operators, in order of highest
-to lowest precedence:
-
-@c @asis for docbook to come out right
-@table @asis
-@item @code{(}@dots{}@code{)}
-Grouping.
-
-@cindex @code{$} (dollar sign) @subentry @code{$} field operator
-@cindex dollar sign (@code{$}) @subentry @code{$} field operator
-@item @code{$}
-Field reference.
-
-@cindex @code{+} (plus sign) @subentry @code{++} operator
-@cindex plus sign (@code{+}) @subentry @code{++} operator
-@cindex @code{-} (hyphen) @subentry @code{--} operator
-@cindex hyphen (@code{-}) @subentry @code{--} operator
-@item @code{++ --}
-Increment, decrement.
-
-@cindex @code{^} (caret) @subentry @code{^} operator
-@cindex caret (@code{^}) @subentry @code{^} operator
-@cindex @code{*} (asterisk) @subentry @code{**} operator
-@cindex asterisk (@code{*}) @subentry @code{**} operator
-@item @code{^ **}
-Exponentiation. These operators group right to left.
-
-@cindex @code{+} (plus sign) @subentry @code{+} operator
-@cindex plus sign (@code{+}) @subentry @code{+} operator
-@cindex @code{-} (hyphen) @subentry @code{-} operator
-@cindex hyphen (@code{-}) @subentry @code{-} operator
-@cindex @code{!} (exclamation point) @subentry @code{!} operator
-@cindex exclamation point (@code{!}) @subentry @code{!} operator
-@item @code{+ - !}
-Unary plus, minus, logical ``not.''
-
-@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry as
multiplication operator
-@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry as
multiplication operator
-@cindex @code{/} (forward slash) @subentry @code{/} operator
-@cindex forward slash (@code{/}) @subentry @code{/} operator
-@cindex @code{%} (percent sign) @subentry @code{%} operator
-@cindex percent sign (@code{%}) @subentry @code{%} operator
-@item @code{* / %}
-Multiplication, division, remainder.
-
-@cindex @code{+} (plus sign) @subentry @code{+} operator
-@cindex plus sign (@code{+}) @subentry @code{+} operator
-@cindex @code{-} (hyphen) @subentry @code{-} operator
-@cindex hyphen (@code{-}) @subentry @code{-} operator
-@item @code{+ -}
-Addition, subtraction.
-
-@item String concatenation
-There is no special symbol for concatenation.
-The operands are simply written side by side
-(@pxref{Concatenation}).
-
-@cindex @code{<} (left angle bracket) @subentry @code{<} operator
-@cindex left angle bracket (@code{<}) @subentry @code{<} operator
-@cindex @code{<} (left angle bracket) @subentry @code{<=} operator
-@cindex left angle bracket (@code{<}) @subentry @code{<=} operator
-@cindex @code{>} (right angle bracket) @subentry @code{>=} operator
-@cindex right angle bracket (@code{>}) @subentry @code{>=} operator
-@cindex @code{>} (right angle bracket) @subentry @code{>} operator
-@cindex right angle bracket (@code{>}) @subentry @code{>} operator
-@cindex @code{=} (equals sign) @subentry @code{==} operator
-@cindex equals sign (@code{=}) @subentry @code{==} operator
-@cindex @code{!} (exclamation point) @subentry @code{!=} operator
-@cindex exclamation point (@code{!}) @subentry @code{!=} operator
-@cindex @code{>} (right angle bracket) @subentry @code{>>} operator (I/O)
-@cindex right angle bracket (@code{>}) @subentry @code{>>} operator (I/O)
-@cindex operators @subentry input/output
-@cindex @code{|} (vertical bar) @subentry @code{|} operator (I/O)
-@cindex vertical bar (@code{|}) @subentry @code{|} operator (I/O)
-@cindex operators @subentry input/output
-@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
-@cindex vertical bar (@code{|}) @subentry @code{|&} operator (I/O)
-@cindex operators @subentry input/output
-@item @code{< <= == != > >= >> | |&}
-Relational and redirection.
-The relational operators and the redirections have the same precedence
-level. Characters such as @samp{>} serve both as relationals and as
-redirections; the context distinguishes between the two meanings.
-
-@cindex @code{print} statement @subentry I/O operators in
-@cindex @code{printf} statement @subentry I/O operators in
-Note that the I/O redirection operators in @code{print} and @code{printf}
-statements belong to the statement level, not to expressions. The
-redirection does not produce an expression that could be the operand of
-another operator. As a result, it does not make sense to use a
-redirection operator near another operator of lower precedence without
-parentheses. Such combinations (e.g., @samp{print foo > a ? b : c})
-result in syntax errors.
-The correct way to write this statement is @samp{print foo > (a ? b : c)}.
-
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-@item @code{~ !~}
-Matching, nonmatching.
-
-@cindex @code{in} operator
-@item @code{in}
-Array membership.
-
-@cindex @code{&} (ampersand) @subentry @code{&&} operator
-@cindex ampersand (@code{&}) @subentry @code{&&} operator
-@item @code{&&}
-Logical ``and.''
-
-@cindex @code{|} (vertical bar) @subentry @code{||} operator
-@cindex vertical bar (@code{|}) @subentry @code{||} operator
-@item @code{||}
-Logical ``or.''
-
-@cindex @code{?} (question mark) @subentry @code{?:} operator
-@cindex question mark (@code{?}) @subentry @code{?:} operator
-@cindex @code{:} (colon) @subentry @code{?:} operator
-@cindex colon (@code{:}) @subentry @code{?:} operator
-@item @code{?:}
-Conditional. This operator groups right to left.
-
-@cindex @code{+} (plus sign) @subentry @code{+=} operator
-@cindex plus sign (@code{+}) @subentry @code{+=} operator
-@cindex @code{-} (hyphen) @subentry @code{-=} operator
-@cindex hyphen (@code{-}) @subentry @code{-=} operator
-@cindex @code{*} (asterisk) @subentry @code{*=} operator
-@cindex asterisk (@code{*}) @subentry @code{*=} operator
-@cindex @code{*} (asterisk) @subentry @code{**=} operator
-@cindex asterisk (@code{*}) @subentry @code{**=} operator
-@cindex @code{/} (forward slash) @subentry @code{/=} operator
-@cindex forward slash (@code{/}) @subentry @code{/=} operator
-@cindex @code{%} (percent sign) @subentry @code{%=} operator
-@cindex percent sign (@code{%}) @subentry @code{%=} operator
-@cindex @code{^} (caret) @subentry @code{^=} operator
-@cindex caret (@code{^}) @subentry @code{^=} operator
-@item @code{= += -= *= /= %= ^= **=}
-Assignment. These operators group right to left.
-@end table
-
-@cindex POSIX @command{awk} @subentry @code{**} operator and
-@cindex portability @subentry operators @subentry not in POSIX @command{awk}
-@quotation NOTE
-The @samp{|&}, @samp{**}, and @samp{**=} operators are not specified by POSIX.
-For maximum portability, do not use them.
-@end quotation
-
-@node Locales
-@section Where You Are Makes a Difference
-@cindex locale, definition of
-
-Modern systems support the notion of @dfn{locales}: a way to tell the
-system about the local character set and language. The ISO C standard
-defines a default @code{"C"} locale, which is an environment that is
-typical of what many C programmers are used to.
-
-Once upon a time, the locale setting used to affect regexp matching,
-but this is no longer true (@pxref{Ranges and Locales}).
-
-Locales can affect record splitting. For the normal case of @samp{RS =
-"\n"}, the locale is largely irrelevant. For other single-character
-record separators, setting @samp{LC_ALL=C} in the environment will
-give you much better performance when reading records. Otherwise,
-@command{gawk} has to make several function calls, @emph{per input
-character}, to find the record terminator.
-
-Locales can affect how dates and times are formatted (@pxref{Time
-Functions}). For example, a common way to abbreviate the date September
-4, 2015, in the United States is ``9/4/15.'' In many countries in
-Europe, however, it is abbreviated ``4.9.15.'' Thus, the @samp{%x}
-specification in a @code{"US"} locale might produce @samp{9/4/15},
-while in a @code{"EUROPE"} locale, it might produce @samp{4.9.15}.
-
-According to POSIX, string comparison is also affected by locales (similar
-to regular expressions). The details are presented in @ref{POSIX String
-Comparison}.
-
-Finally, the locale affects the value of the decimal point character
-used when @command{gawk} parses input data. This is discussed in detail
-in @ref{Conversion}.
-
-@node Expressions Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Expressions are the basic elements of computation in programs. They are
-built from constants, variables, function calls, and combinations of the
-various kinds of values with operators.
-
-@item
-@command{awk} supplies three kinds of constants: numeric, string, and
-regexp. @command{gawk} lets you specify numeric constants in octal
-and hexadecimal (bases 8 and 16) as well as decimal (base 10).
-In certain contexts, a standalone regexp constant such as @code{/foo/}
-has the same meaning as @samp{$0 ~ /foo/}.
-
-@item
-Variables hold values between uses in computations. A number of built-in
-variables provide information to your @command{awk} program, and a number
-of others let you control how @command{awk} behaves.
-
-@item
-Numbers are automatically converted to strings, and strings to numbers,
-as needed by @command{awk}. Numeric values are converted as if they were
-formatted with @code{sprintf()} using the format in @code{CONVFMT}.
-Locales can influence the conversions.
-
-@item
-@command{awk} provides the usual arithmetic operators (addition,
-subtraction, multiplication, division, modulus), and unary plus and minus.
-It also provides comparison operators, Boolean operators, an array membership
-testing operator, and regexp
-matching operators. String concatenation is accomplished by placing
-two expressions next to each other; there is no explicit operator.
-The three-operand @samp{?:} operator provides an ``if-else'' test within
-expressions.
-
-@item
-Assignment operators provide convenient shorthands for common arithmetic
-operations.
-
-@item
-In @command{awk}, a value is considered to be true if it is nonzero
-@emph{or} non-null. Otherwise, the value is false.
-
-@item
-A variable's type is set upon each assignment and may change over its
-lifetime. The type determines how it behaves in comparisons (string
-or numeric).
-
-@item
-Function calls return a value that may be used as part of a larger
-expression. Expressions used to pass parameter values are fully
-evaluated before the function is called. @command{awk} provides
-built-in and user-defined functions; this is described in
-@ref{Functions}.
-
-@item
-Operator precedence specifies the order in which operations are performed,
-unless explicitly overridden by parentheses. @command{awk}'s operator
-precedence is compatible with that of C.
-
-@item
-Locales can affect the format of data as output by an @command{awk}
-program, and occasionally the format for data read as input.
-
-@end itemize
-
-
-@node Patterns and Actions
-@chapter Patterns, Actions, and Variables
-@cindex patterns
-
-As you have already seen, each @command{awk} statement consists of
-a pattern with an associated action. This @value{CHAPTER} describes how
-you build patterns and actions, what kinds of things you can do within
-actions, and @command{awk}'s predefined variables.
-
-The pattern--action rules and the statements available for use
-within actions form the core of @command{awk} programming.
-In a sense, everything covered
-up to here has been the foundation
-that programs are built on top of. Now it's time to start
-building something useful.
-
-@menu
-* Pattern Overview:: What goes into a pattern.
-* Using Shell Variables:: How to use shell variables with @command{awk}.
-* Action Overview:: What goes into an action.
-* Statements:: Describes the various control statements in
- detail.
-* Built-in Variables:: Summarizes the predefined variables.
-* Pattern Action Summary:: Patterns and Actions summary.
-@end menu
-
-@node Pattern Overview
-@section Pattern Elements
-
-@menu
-* Regexp Patterns:: Using regexps as patterns.
-* Expression Patterns:: Any expression can be used as a pattern.
-* Ranges:: Pairs of patterns specify record ranges.
-* BEGIN/END:: Specifying initialization and cleanup rules.
-* BEGINFILE/ENDFILE:: Two special patterns for advanced control.
-* Empty:: The empty pattern, which matches every record.
-@end menu
-
-@cindex patterns @subentry types of
-Patterns in @command{awk} control the execution of rules---a rule is
-executed when its pattern matches the current input record.
-The following is a summary of the types of @command{awk} patterns:
-
-@table @code
-@item /@var{regular expression}/
-A regular expression. It matches when the text of the
-input record fits the regular expression.
-(@xref{Regexp}.)
-
-@item @var{expression}
-A single expression. It matches when its value
-is nonzero (if a number) or non-null (if a string).
-(@xref{Expression Patterns}.)
-
-@item @var{begpat}, @var{endpat}
-A pair of patterns separated by a comma, specifying a @dfn{range} of records.
-The range includes both the initial record that matches @var{begpat} and
-the final record that matches @var{endpat}.
-(@xref{Ranges}.)
-
-@item BEGIN
-@itemx END
-Special patterns for you to supply startup or cleanup actions for your
-@command{awk} program.
-(@xref{BEGIN/END}.)
-
-@item BEGINFILE
-@itemx ENDFILE
-Special patterns for you to supply startup or cleanup actions to be
-done on a per-file basis.
-(@xref{BEGINFILE/ENDFILE}.)
-
-@item @var{empty}
-The empty pattern matches every input record.
-(@xref{Empty}.)
-@end table
-
-@node Regexp Patterns
-@subsection Regular Expressions as Patterns
-@cindex patterns @subentry regexp constants as
-@cindex regular expressions @subentry as patterns
-
-Regular expressions are one of the first kinds of patterns presented
-in this book.
-This kind of pattern is simply a regexp constant in the pattern part of
-a rule. Its meaning is @samp{$0 ~ /@var{pattern}/}.
-The pattern matches when the input record matches the regexp.
-For example:
-
-@example
-/foo|bar|baz/ @{ buzzwords++ @}
-END @{ print buzzwords, "buzzwords seen" @}
-@end example
-
-@node Expression Patterns
-@subsection Expressions as Patterns
-@cindex expressions @subentry as patterns
-@cindex patterns @subentry expressions as
-
-Any @command{awk} expression is valid as an @command{awk} pattern.
-The pattern matches if the expression's value is nonzero (if a
-number) or non-null (if a string).
-The expression is reevaluated each time the rule is tested against a new
-input record. If the expression uses fields such as @code{$1}, the
-value depends directly on the new input record's text; otherwise, it
-depends on only what has happened so far in the execution of the
-@command{awk} program.
-
-@cindex comparison expressions @subentry as patterns
-@cindex patterns @subentry comparison expressions as
-Comparison expressions, using the comparison operators described in
-@ref{Typing and Comparison},
-are a very common kind of pattern.
-Regexp matching and nonmatching are also very common expressions.
-The left operand of the @samp{~} and @samp{!~} operators is a string.
-The right operand is either a constant regular expression enclosed in
-slashes (@code{/@var{regexp}/}), or any expression whose string value
-is used as a dynamic regular expression
-(@pxref{Computed Regexps}).
-The following example prints the second field of each input record
-whose first field is precisely @samp{li}:
-
-@cindex @code{/} (forward slash) @subentry patterns and
-@cindex forward slash (@code{/}) @subentry patterns and
-@cindex @code{~} (tilde), @code{~} operator
-@cindex tilde (@code{~}), @code{~} operator
-@cindex @code{!} (exclamation point) @subentry @code{!~} operator
-@cindex exclamation point (@code{!}) @subentry @code{!~} operator
-@example
-$ @kbd{awk '$1 == "li" @{ print $2 @}' mail-list}
-@end example
-
-@noindent
-(There is no output, because there is no person with the exact name @samp{li}.)
-Contrast this with the following regular expression match, which
-accepts any record with a first field that contains @samp{li}:
-
-@example
-$ @kbd{awk '$1 ~ /li/ @{ print $2 @}' mail-list}
-@print{} 555-5553
-@print{} 555-6699
-@end example
-
-@cindex regexp constants @subentry as patterns
-@cindex patterns @subentry regexp constants as
-A regexp constant as a pattern is also a special case of an expression
-pattern. The expression @code{/li/} has the value one if @samp{li}
-appears in the current input record. Thus, as a pattern, @code{/li/}
-matches any record containing @samp{li}.
-
-@cindex Boolean expressions @subentry as patterns
-@cindex patterns @subentry Boolean expressions as
-Boolean expressions are also commonly used as patterns.
-Whether the pattern
-matches an input record depends on whether its subexpressions match.
-For example, the following command prints all the records in
-@file{mail-list} that contain both @samp{edu} and @samp{li}:
-
-@example
-$ @kbd{awk '/edu/ && /li/' mail-list}
-@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A
-@end example
-
-The following command prints all records in
-@file{mail-list} that contain @emph{either} @samp{edu} or @samp{li}
-(or both, of course):
-
-@example
-$ @kbd{awk '/edu/ || /li/' mail-list}
-@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F
-@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R
-@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
-@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F
-@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A
-@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
-@end example
-
-The following command prints all records in
-@file{mail-list} that do @emph{not} contain the string @samp{li}:
-
-@example
-$ @kbd{awk '! /li/' mail-list}
-@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A
-@print{} Becky 555-7685 becky.algebrarum@@gmail.com A
-@print{} Bill 555-1675 bill.drowning@@hotmail.com A
-@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R
-@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
-@group
-@print{} Martin 555-6480 martin.codicibus@@hotmail.com A
-@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
-@end group
-@end example
-
-@cindex @code{BEGIN} pattern @subentry Boolean patterns and
-@cindex @code{END} pattern @subentry Boolean patterns and
-@cindex @code{BEGINFILE} pattern @subentry Boolean patterns and
-@cindex @code{ENDFILE} pattern @subentry Boolean patterns and
-The subexpressions of a Boolean operator in a pattern can be constant regular
-expressions, comparisons, or any other @command{awk} expressions. Range
-patterns are not expressions, so they cannot appear inside Boolean
-patterns. Likewise, the special patterns @code{BEGIN}, @code{END},
-@code{BEGINFILE}, and @code{ENDFILE},
-which never match any input record, are not expressions and cannot
-appear inside Boolean patterns.
-
-The precedence of the different operators that can appear in
-patterns is described in @ref{Precedence}.
-
-@node Ranges
-@subsection Specifying Record Ranges with Patterns
-
-@cindex range patterns
-@cindex patterns @subentry ranges in
-@cindex lines @subentry matching ranges of
-@cindex @code{,} (comma), in range patterns
-@cindex comma (@code{,}), in range patterns
-A @dfn{range pattern} is made of two patterns separated by a comma, in
-the form @samp{@var{begpat}, @var{endpat}}. It is used to match ranges of
-consecutive input records. The first pattern, @var{begpat}, controls
-where the range begins, while @var{endpat} controls where
-the pattern ends. For example, the following:
-
-@example
-awk '$1 == "on", $1 == "off"' myfile
-@end example
-
-@noindent
-prints every record in @file{myfile} between @samp{on}/@samp{off} pairs,
inclusive.
-
-A range pattern starts out by matching @var{begpat} against every
-input record. When a record matches @var{begpat}, the range pattern is
-@dfn{turned on}, and the range pattern matches this record as well. As long as
-the range pattern stays turned on, it automatically matches every input
-record read. The range pattern also matches @var{endpat} against every
-input record; when this succeeds, the range pattern is @dfn{turned off} again
-for the following record. Then the range pattern goes back to checking
-@var{begpat} against each record.
-
-@cindex @code{if} statement @subentry actions, changing
-The record that turns on the range pattern and the one that turns it
-off both match the range pattern. If you don't want to operate on
-these records, you can write @code{if} statements in the rule's action
-to distinguish them from the records you are interested in.
-
-It is possible for a pattern to be turned on and off by the same
-record. If the record satisfies both conditions, then the action is
-executed for just that record.
-For example, suppose there is text between two identical markers (e.g.,
-the @samp{%} symbol), each on its own line, that should be ignored.
-A first attempt would be to
-combine a range pattern that describes the delimited text with the
-@code{next} statement
-(not discussed yet, @pxref{Next Statement}).
-This causes @command{awk} to skip any further processing of the current
-record and start over again with the next input record. Such a program
-looks like this:
-
-@example
-/^%$/,/^%$/ @{ next @}
- @{ print @}
-@end example
-
-@noindent
-@cindex lines @subentry skipping between markers
-@c @cindex flag variables
-This program fails because the range pattern is both turned on and turned off
-by the first line, which just has a @samp{%} on it. To accomplish this task,
-write the program in the following manner, using a flag:
-
-@cindex @code{!} (exclamation point) @subentry @code{!} operator
-@example
-/^%$/ @{ skip = ! skip; next @}
-skip == 1 @{ next @} # skip lines with `skip' set
-@end example
-
-In a range pattern, the comma (@samp{,}) has the lowest precedence of
-all the operators (i.e., it is evaluated last). Thus, the following
-program attempts to combine a range pattern with another, simpler test:
-
-@example
-echo Yes | awk '/1/,/2/ || /Yes/'
-@end example
-
-The intent of this program is @samp{(/1/,/2/) || /Yes/}.
-However, @command{awk} interprets this as @samp{/1/, (/2/ || /Yes/)}.
-This cannot be changed or worked around; range patterns do not combine
-with other patterns:
-
-@example
-$ @kbd{echo Yes | gawk '(/1/,/2/) || /Yes/'}
-@error{} gawk: cmd. line:1: (/1/,/2/) || /Yes/
-@error{} gawk: cmd. line:1: ^ syntax error
-@end example
-
-@cindex range patterns @subentry line continuation and
-@cindex dark corner @subentry range patterns, line continuation and
-As a minor point of interest, although it is poor style,
-POSIX allows you to put a newline after the comma in
-a range pattern. @value{DARKCORNER}
-
-@node BEGIN/END
-@subsection The @code{BEGIN} and @code{END} Special Patterns
-
-@cindex @code{BEGIN} pattern
-@cindex @code{END} pattern
-All the patterns described so far are for matching input records.
-The @code{BEGIN} and @code{END} special patterns are different.
-They supply startup and cleanup actions for @command{awk} programs.
-@code{BEGIN} and @code{END} rules must have actions; there is no default
-action for these rules because there is no current record when they run.
-@code{BEGIN} and @code{END} rules are often referred to as
-``@code{BEGIN} and @code{END} blocks'' by longtime @command{awk}
-programmers.
-
-@menu
-* Using BEGIN/END:: How and why to use BEGIN/END rules.
-* I/O And BEGIN/END:: I/O issues in BEGIN/END rules.
-@end menu
-
-@node Using BEGIN/END
-@subsubsection Startup and Cleanup Actions
-
-@cindex @code{BEGIN} pattern
-@cindex @code{END} pattern
-A @code{BEGIN} rule is executed once only, before the first input record
-is read. Likewise, an @code{END} rule is executed once only, after all the
-input is read. For example:
-
-@example
-$ @kbd{awk '}
-> @kbd{BEGIN @{ print "Analysis of \"li\"" @}}
-> @kbd{/li/ @{ ++n @}}
-> @kbd{END @{ print "\"li\" appears in", n, "records." @}' mail-list}
-@print{} Analysis of "li"
-@print{} "li" appears in 4 records.
-@end example
-
-@cindex @code{BEGIN} pattern @subentry operators and
-@cindex @code{END} pattern @subentry operators and
-This program finds the number of records in the input file @file{mail-list}
-that contain the string @samp{li}. The @code{BEGIN} rule prints a title
-for the report. There is no need to use the @code{BEGIN} rule to
-initialize the counter @code{n} to zero, as @command{awk} does this
-automatically (@pxref{Variables}).
-The second rule increments the variable @code{n} every time a
-record containing the pattern @samp{li} is read. The @code{END} rule
-prints the value of @code{n} at the end of the run.
-
-The special patterns @code{BEGIN} and @code{END} cannot be used in ranges
-or with Boolean operators (indeed, they cannot be used with any operators).
-An @command{awk} program may have multiple @code{BEGIN} and/or @code{END}
-rules. They are executed in the order in which they appear: all the
@code{BEGIN}
-rules at startup and all the @code{END} rules at termination.
-
-@code{BEGIN} and @code{END} rules may be intermixed with other rules.
-This feature was added in the 1987 version of @command{awk} and is included
-in the POSIX standard.
-The original (1978) version of @command{awk}
-required the @code{BEGIN} rule to be placed at the beginning of the
-program, the @code{END} rule to be placed at the end, and only allowed one of
-each.
-This is no longer required, but it is a good idea to follow this template
-in terms of program organization and readability.
-
-Multiple @code{BEGIN} and @code{END} rules are useful for writing
-library functions, because each library file can have its own @code{BEGIN}
and/or
-@code{END} rule to do its own initialization and/or cleanup.
-The order in which library functions are named on the command line
-controls the order in which their @code{BEGIN} and @code{END} rules are
-executed. Therefore, you have to be careful when writing such rules in
-library files so that the order in which they are executed doesn't matter.
-@xref{Options} for more information on
-using library functions.
-@xref{Library Functions},
-for a number of useful library functions.
-
-If an @command{awk} program has only @code{BEGIN} rules and no
-other rules, then the program exits after the @code{BEGIN} rules are
-run.@footnote{The original version of @command{awk} kept
-reading and ignoring input until the end of the file was seen.} However, if an
-@code{END} rule exists, then the input is read, even if there are
-no other rules in the program. This is necessary in case the @code{END}
-rule checks the @code{FNR} and @code{NR} variables, or the fields.
-
-@node I/O And BEGIN/END
-@subsubsection Input/Output from @code{BEGIN} and @code{END} Rules
-
-@cindex input/output @subentry from @code{BEGIN} and @code{END}
-There are several (sometimes subtle) points to be aware of when doing I/O
-from a @code{BEGIN} or @code{END} rule.
-The first has to do with the value of @code{$0} in a @code{BEGIN}
-rule. Because @code{BEGIN} rules are executed before any input is read,
-there simply is no input record, and therefore no fields, when
-executing @code{BEGIN} rules. References to @code{$0} and the fields
-yield a null string or zero, depending upon the context. One way
-to give @code{$0} a real value is to execute a @code{getline} command
-without a variable (@pxref{Getline}).
-Another way is simply to assign a value to @code{$0}.
-
-@cindex Brian Kernighan's @command{awk}
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{BEGIN}/@code{END} patterns
-@cindex POSIX @command{awk} @subentry @code{BEGIN}/@code{END} patterns
-@cindex @code{print} statement @subentry @code{BEGIN}/@code{END} patterns and
-@cindex @code{BEGIN} pattern @subentry @code{print} statement and
-@cindex @code{END} pattern @subentry @code{print} statement and
-The second point is similar to the first, but from the other direction.
-Traditionally, due largely to implementation issues, @code{$0} and
-@code{NF} were @emph{undefined} inside an @code{END} rule.
-The POSIX standard specifies that @code{NF} is available in an @code{END}
-rule. It contains the number of fields from the last input record.
-@c FIXME: Update this if POSIX is ever fixed.
-Most probably due to an oversight, the standard does not say that @code{$0}
-is also preserved, although logically one would think that it should be.
-In fact, all of BWK @command{awk}, @command{mawk}, and @command{gawk}
-preserve the value of @code{$0} for use in @code{END} rules. Be aware,
-however, that some other implementations and many older versions
-of Unix @command{awk} do not.
-
-The third point follows from the first two. The meaning of @samp{print}
-inside a @code{BEGIN} or @code{END} rule is the same as always:
-@samp{print $0}. If @code{$0} is the null string, then this prints an
-empty record. Many longtime @command{awk} programmers use an unadorned
-@samp{print} in @code{BEGIN} and @code{END} rules to mean @samp{@w{print ""}},
-relying on @code{$0} being null. Although one might generally get away with
-this in @code{BEGIN} rules, it is a very bad idea in @code{END} rules,
-at least in @command{gawk}. It is also poor style, because if an empty
-line is needed in the output, the program should print one explicitly.
-
-@cindex @code{next} statement @subentry @code{BEGIN}/@code{END} patterns and
-@cindex @code{nextfile} statement @subentry @code{BEGIN}/@code{END} patterns
and
-@cindex @code{BEGIN} pattern @subentry @code{next}/@code{nextfile} statements
and
-@cindex @code{END} pattern @subentry @code{next}/@code{nextfile} statements and
-Finally, the @code{next} and @code{nextfile} statements are not allowed
-in a @code{BEGIN} rule, because the implicit
-read-a-record-and-match-against-the-rules loop has not started yet.
Similarly, those statements
-are not valid in an @code{END} rule, because all the input has been read.
-(@xref{Next Statement} and
-@ifnotdocbook
-@pxref{Nextfile Statement}.)
-@end ifnotdocbook
-@ifdocbook
-@ref{Nextfile Statement}.)
-@end ifdocbook
-
-@node BEGINFILE/ENDFILE
-@subsection The @code{BEGINFILE} and @code{ENDFILE} Special Patterns
-@cindex @code{BEGINFILE} pattern
-@cindex @code{ENDFILE} pattern
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{BEGINFILE}/@code{ENDFILE} patterns
-
-This @value{SECTION} describes a @command{gawk}-specific feature.
-
-Two special kinds of rule, @code{BEGINFILE} and @code{ENDFILE}, give
-you ``hooks'' into @command{gawk}'s command-line file processing loop.
-As with the @code{BEGIN} and @code{END} rules
-@ifnottex
-@ifnotdocbook
-@ifnotlatex
-(@pxref{BEGIN/END}),
-@end ifnotlatex
-@end ifnotdocbook
-@end ifnottex
-@iftex
-(see the previous @value{SECTION}),
-@end iftex
-@iflatex
-(see the previous @value{SECTION}),
-@end iflatex
-@ifdocbook
-(see the previous @value{SECTION}),
-@end ifdocbook
-@code{BEGINFILE} rules in a program execute in the order they are
-read by @command{gawk}. Similarly, all @code{ENDFILE} rules also execute in
-the order they are read.
-
-The bodies of the @code{BEGINFILE} rules execute just before
-@command{gawk} reads the first record from a file. @code{FILENAME}
-is set to the name of the current file, and @code{FNR} is set to zero.
-
-Prior to @value{PVERSION} 5.1.1 of @command{gawk}, as an accident of the
-implementation, @code{$0} and the fields retained any previous values
-they had in @code{BEGINFILE} rules. Starting with @value{PVERSION}
-5.1.1, @code{$0} and the fields are cleared, since no record has been
-read yet from the file that is about to be processed.
-
-The @code{BEGINFILE} rule provides you the opportunity to accomplish two tasks
-that would otherwise be difficult or impossible to perform:
-
-@itemize @value{BULLET}
-@item
-You can test if the file is readable. Normally, it is a fatal error if a
-file named on the command line cannot be opened for reading. However,
-you can bypass the fatal error and move on to the next file on the
-command line.
-
-@cindex @command{gawk} @subentry @code{ERRNO} variable in
-@cindex @code{ERRNO} variable @subentry with @code{BEGINFILE} pattern
-@cindex @code{nextfile} statement @subentry @code{BEGINFILE}/@code{ENDFILE}
patterns and
-You do this by checking if the @code{ERRNO} variable is not the empty
-string; if so, then @command{gawk} was not able to open the file. In
-this case, your program can execute the @code{nextfile} statement
-(@pxref{Nextfile Statement}). This causes @command{gawk} to skip
-the file entirely. Otherwise, @command{gawk} exits with the usual
-fatal error.
-
-@item
-If you have written extensions that modify the record handling (by
-inserting an ``input parser''; @pxref{Input Parsers}), you can invoke
-them at this point, before @command{gawk} has started processing the file.
-(This is a @emph{very} advanced feature, currently used only by the
-@uref{https://sourceforge.net/projects/gawkextlib, @code{gawkextlib} project}.)
-@end itemize
-
-The @code{ENDFILE} rule is called when @command{gawk} has finished processing
-the last record in an input file. For the last input file,
-it will be called before any @code{END} rules.
-The @code{ENDFILE} rule is executed even for empty input files.
-
-Normally, when an error occurs when reading input in the normal
-input-processing loop, the error is fatal. However, if a @code{BEGINFILE}
-rule is present, the error becomes non-fatal, and instead @code{ERRNO}
-is set. This makes it possible to catch and process I/O errors at the
-level of the @command{awk} program.
-
-@cindex @code{next} statement @subentry @code{BEGINFILE}/@code{ENDFILE}
patterns and
-The @code{next} statement (@pxref{Next Statement}) is not allowed inside
-either a @code{BEGINFILE} or an @code{ENDFILE} rule. The @code{nextfile}
-statement is allowed only inside a
-@code{BEGINFILE} rule, not inside an @code{ENDFILE} rule.
-
-@cindex @code{getline} command @subentry @code{BEGINFILE}/@code{ENDFILE}
patterns and
-The @code{getline} statement (@pxref{Getline}) is restricted inside
-both @code{BEGINFILE} and @code{ENDFILE}: only redirected
-forms of @code{getline} are allowed.
-
-@code{BEGINFILE} and @code{ENDFILE} are @command{gawk} extensions.
-In most other @command{awk} implementations, or if @command{gawk} is in
-compatibility mode (@pxref{Options}), they are not special.
-
-@node Empty
-@subsection The Empty Pattern
-
-@cindex empty pattern
-@cindex patterns @subentry empty
-An empty (i.e., nonexistent) pattern is considered to match @emph{every}
-input record. For example, the program:
-
-@example
-awk '@{ print $1 @}' mail-list
-@end example
-
-@noindent
-prints the first field of every record.
-
-@node Using Shell Variables
-@section Using Shell Variables in Programs
-@cindex shells @subentry variables
-@cindex @command{awk} programs @subentry shell variables in
-@c @cindex shell and @command{awk} interaction
-
-@command{awk} programs are often used as components in larger
-programs written in shell.
-For example, it is very common to use a shell variable to
-hold a pattern that the @command{awk} program searches for.
-There are two ways to get the value of the shell variable
-into the body of the @command{awk} program.
-
-@cindex shells @subentry quoting
-A common method is to use shell quoting to substitute
-the variable's value into the program inside the script.
-For example, consider the following program:
-
-@example
-@group
-printf "Enter search pattern: "
-read pattern
-awk "/$pattern/ "'@{ nmatches++ @}
- END @{ print nmatches, "found" @}' /path/to/data
-@end group
-@end example
-
-@noindent
-The @command{awk} program consists of two pieces of quoted text
-that are concatenated together to form the program.
-The first part is double-quoted, which allows substitution of
-the @code{pattern} shell variable inside the quotes.
-The second part is single-quoted.
-
-Variable substitution via quoting works, but can potentially be
-messy. It requires a good understanding of the shell's quoting rules
-(@pxref{Quoting}),
-and it's often difficult to correctly
-match up the quotes when reading the program.
-
-A better method is to use @command{awk}'s variable assignment feature
-(@pxref{Assignment Options})
-to assign the shell variable's value to an @command{awk} variable.
-Then use dynamic regexps to match the pattern
-(@pxref{Computed Regexps}).
-The following shows how to redo the
-previous example using this technique:
-
-@example
-printf "Enter search pattern: "
-read pattern
-awk -v pat="$pattern" '$0 ~ pat @{ nmatches++ @}
- END @{ print nmatches, "found" @}' /path/to/data
-@end example
-
-@noindent
-Now, the @command{awk} program is just one single-quoted string.
-The assignment @samp{-v pat="$pattern"} still requires double quotes,
-in case there is whitespace in the value of @code{$pattern}.
-The @command{awk} variable @code{pat} could be named @code{pattern}
-too, but that would be more confusing. Using a variable also
-provides more flexibility, as the variable can be used anywhere inside
-the program---for printing, as an array subscript, or for any other
-use---without requiring the quoting tricks at every point in the program.
-
-@node Action Overview
-@section Actions
-@c @cindex action, definition of
-@c @cindex curly braces
-@c @cindex action, curly braces
-@c @cindex action, separating statements
-@cindex actions
-
-An @command{awk} program or script consists of a series of
-rules and function definitions interspersed. (Functions are
-described later. @xref{User-defined}.)
-A rule contains a pattern and an action, either of which (but not
-both) may be omitted. The purpose of the @dfn{action} is to tell
-@command{awk} what to do once a match for the pattern is found. Thus,
-in outline, an @command{awk} program generally looks like this:
-
-@display
-[@var{pattern}] @code{@{ @var{action} @}}
- @var{pattern} [@code{@{ @var{action} @}}]
-@dots{}
-@code{function @var{name}(@var{args}) @{ @dots{} @}}
-@dots{}
-@end display
-
-@cindex @code{@{@}} (braces) @subentry actions and
-@cindex braces (@code{@{@}}) @subentry actions and
-@cindex separators @subentry for statements in actions
-@cindex newlines @subentry separating statements in actions
-@cindex @code{;} (semicolon) @subentry separating statements in actions
-@cindex semicolon (@code{;}) @subentry separating statements in actions
-An action consists of one or more @command{awk} @dfn{statements}, enclosed
-in braces (@samp{@{@r{@dots{}}@}}). Each statement specifies one
-thing to do. The statements are separated by newlines or semicolons.
-The braces around an action must be used even if the action
-contains only one statement, or if it contains no statements at
-all. However, if you omit the action entirely, omit the braces as
-well. An omitted action is equivalent to @samp{@{ print $0 @}}:
-
-@example
-/foo/ @{ @} @ii{match @code{foo}, do nothing --- empty action}
-/foo/ @ii{match @code{foo}, print the record --- omitted action}
-@end example
-
-The following types of statements are supported in @command{awk}:
-
-@table @asis
-@cindex side effects @subentry statements
-@item Expressions
-Call functions or assign values to variables
-(@pxref{Expressions}). Executing
-this kind of statement simply computes the value of the expression.
-This is useful when the expression has side effects
-(@pxref{Assignment Ops}).
-
-@item Control statements
-Specify the control flow of @command{awk}
-programs. The @command{awk} language gives you C-like constructs
-(@code{if}, @code{for}, @code{while}, and @code{do}) as well as a few
-special ones (@pxref{Statements}).
-
-@item Compound statements
-Enclose one or more statements in braces. A compound statement
-is used in order to put several statements together in the body of an
-@code{if}, @code{while}, @code{do}, or @code{for} statement.
-
-@item Input statements
-Use the @code{getline} command
-(@pxref{Getline}).
-Also supplied in @command{awk} are the @code{next}
-statement (@pxref{Next Statement})
-and the @code{nextfile} statement
-(@pxref{Nextfile Statement}).
-
-@item Output statements
-Such as @code{print} and @code{printf}.
-@xref{Printing}.
-
-@item Deletion statements
-For deleting array elements.
-@xref{Delete}.
-@end table
-
-@node Statements
-@section Control Statements in Actions
-@cindex control statements
-@cindex statements @subentry control, in actions
-@cindex actions @subentry control statements in
-
-@dfn{Control statements}, such as @code{if}, @code{while}, and so on,
-control the flow of execution in @command{awk} programs. Most of
@command{awk}'s
-control statements are patterned after similar statements in C.
-
-@cindex compound statements, control statements and
-@cindex statements @subentry compound, control statements and
-@cindex body @subentry in actions
-@cindex @code{@{@}} (braces) @subentry statements, grouping
-@cindex braces (@code{@{@}}) @subentry statements, grouping
-@cindex newlines @subentry separating statements in actions
-@cindex @code{;} (semicolon) @subentry separating statements in actions
-@cindex semicolon (@code{;}) @subentry separating statements in actions
-All the control statements start with special keywords, such as @code{if}
-and @code{while}, to distinguish them from simple expressions.
-Many control statements contain other statements. For example, the
-@code{if} statement contains another statement that may or may not be
-executed. The contained statement is called the @dfn{body}.
-To include more than one statement in the body, group them into a
-single @dfn{compound statement} with braces, separating them with
-newlines or semicolons.
-
-@menu
-* If Statement:: Conditionally execute some @command{awk}
- statements.
-* While Statement:: Loop until some condition is satisfied.
-* Do Statement:: Do specified action while looping until some
- condition is satisfied.
-* For Statement:: Another looping statement, that provides
- initialization and increment clauses.
-* Switch Statement:: Switch/case evaluation for conditional
- execution of statements based on a value.
-* Break Statement:: Immediately exit the innermost enclosing loop.
-* Continue Statement:: Skip to the end of the innermost enclosing
- loop.
-* Next Statement:: Stop processing the current input record.
-* Nextfile Statement:: Stop processing the current file.
-* Exit Statement:: Stop execution of @command{awk}.
-@end menu
-
-@node If Statement
-@subsection The @code{if}-@code{else} Statement
-
-@cindex @code{if} statement
-The @code{if}-@code{else} statement is @command{awk}'s decision-making
-statement. It looks like this:
-
-@display
-@code{if (@var{condition}) @var{then-body}} [@code{else @var{else-body}}]
-@end display
-
-@noindent
-The @var{condition} is an expression that controls what the rest of the
-statement does. If the @var{condition} is true, @var{then-body} is
-executed; otherwise, @var{else-body} is executed.
-The @code{else} part of the statement is
-optional. The condition is considered false if its value is zero or
-the null string; otherwise, the condition is true.
-Refer to the following:
-
-@example
-@group
-if (x % 2 == 0)
- print "x is even"
-else
- print "x is odd"
-@end group
-@end example
-
-In this example, if the expression @samp{x % 2 == 0} is true (i.e.,
-if the value of @code{x} is evenly divisible by two), then the first
-@code{print} statement is executed; otherwise, the second @code{print}
-statement is executed.
-If the @code{else} keyword appears on the same line as @var{then-body} and
-@var{then-body} is not a compound statement (i.e., not surrounded by
-braces), then a semicolon must separate @var{then-body} from
-the @code{else}.
-To illustrate this, the previous example can be rewritten as:
-
-@example
-if (x % 2 == 0) print "x is even"; else
- print "x is odd"
-@end example
-
-@noindent
-If the @samp{;} is left out, @command{awk} can't interpret the statement and
-it produces a syntax error. Don't actually write programs this way,
-because a human reader might fail to see the @code{else} if it is not
-the first thing on its line.
-
-@node While Statement
-@subsection The @code{while} Statement
-@cindex @code{while} statement
-@cindex loops
-@cindex loops @subentry @code{while}
-@cindex loops @seealso{@code{while} statement}
-
-In programming, a @dfn{loop} is a part of a program that can
-be executed two or more times in succession.
-The @code{while} statement is the simplest looping statement in
-@command{awk}. It repeatedly executes a statement as long as a condition is
-true. For example:
-
-@example
-while (@var{condition})
- @var{body}
-@end example
-
-@cindex body @subentry in loops
-@noindent
-@var{body} is a statement called the @dfn{body} of the loop,
-and @var{condition} is an expression that controls how long the loop
-keeps running.
-The first thing the @code{while} statement does is test the @var{condition}.
-If the @var{condition} is true, it executes the statement @var{body}.
-@ifinfo
-(The @var{condition} is true when the value
-is not zero and not a null string.)
-@end ifinfo
-After @var{body} has been executed,
-@var{condition} is tested again, and if it is still true, @var{body}
-executes again. This process repeats until the @var{condition} is no longer
-true. If the @var{condition} is initially false, the body of the loop
-never executes and @command{awk} continues with the statement following
-the loop.
-This example prints the first three fields of each record, one per line:
-
-@example
-awk '
-@{
- i = 1
- while (i <= 3) @{
- print $i
- i++
- @}
-@}' inventory-shipped
-@end example
-
-@noindent
-The body of this loop is a compound statement enclosed in braces,
-containing two statements.
-The loop works in the following manner: first, the value of @code{i} is set to
one.
-Then, the @code{while} statement tests whether @code{i} is less than or equal
to
-three. This is true when @code{i} equals one, so the @code{i}th
-field is printed. Then the @samp{i++} increments the value of @code{i}
-and the loop repeats. The loop terminates when @code{i} reaches four.
-
-A newline is not required between the condition and the
-body; however, using one makes the program clearer unless the body is a
-compound statement or else is very simple. The newline after the open brace
-that begins the compound statement is not required either, but the
-program is harder to read without it.
-
-@node Do Statement
-@subsection The @code{do}-@code{while} Statement
-@cindex @code{do}-@code{while} statement
-@cindex loops @subentry @code{do}-@code{while}
-
-The @code{do} loop is a variation of the @code{while} looping statement.
-The @code{do} loop executes the @var{body} once and then repeats the
-@var{body} as long as the @var{condition} is true. It looks like this:
-
-@example
-do
- @var{body}
-while (@var{condition})
-@end example
-
-Even if the @var{condition} is false at the start, the @var{body}
-executes at least once (and only once, unless executing @var{body}
-makes @var{condition} true). Contrast this with the corresponding
-@code{while} statement:
-
-@example
-while (@var{condition})
- @var{body}
-@end example
-
-@noindent
-This statement does not execute the @var{body} even once if the
-@var{condition} is false to begin with. The following is an example of
-a @code{do} statement:
-
-@example
-@{
- i = 1
- do @{
- print $0
- i++
- @} while (i <= 10)
-@}
-@end example
-
-@noindent
-This program prints each input record 10 times. However, it isn't a very
-realistic example, because in this case an ordinary @code{while} would do
-just as well. This situation reflects actual experience; only
-occasionally is there a real use for a @code{do} statement.
-
-@node For Statement
-@subsection The @code{for} Statement
-@cindex @code{for} statement
-@cindex loops @subentry @code{for} @subentry iterative
-
-The @code{for} statement makes it more convenient to count iterations of a
-loop. The general form of the @code{for} statement looks like this:
-
-@example
-for (@var{initialization}; @var{condition}; @var{increment})
- @var{body}
-@end example
-
-@noindent
-The @var{initialization}, @var{condition}, and @var{increment} parts are
-arbitrary @command{awk} expressions, and @var{body} stands for any
-@command{awk} statement.
-
-The @code{for} statement starts by executing @var{initialization}.
-Then, as long
-as the @var{condition} is true, it repeatedly executes @var{body} and then
-@var{increment}. Typically, @var{initialization} sets a variable to
-either zero or one, @var{increment} adds one to it, and @var{condition}
-compares it against the desired number of iterations.
-For example:
-
-@example
-awk '
-@{
- for (i = 1; i <= 3; i++)
- print $i
-@}' inventory-shipped
-@end example
-
-@noindent
-This prints the first three fields of each input record, with one
-input field per output line.
-
-@c @cindex comma operator, not supported
-C and C++ programmers might expect to be able to use the comma
-operator to set more than one variable in the @var{initialization}
-part of the @code{for} loop, or to increment multiple variables in the
-@var{increment} part of the loop, like so:
-
-@example
-for (i = 0, j = length(a); i < j; i++, j--) @dots{} @ii{C/C++, not awk!}
-@end example
-
-@noindent
-You cannot do this; the comma operator is not supported in @command{awk}.
-There are workarounds, but they are nonobvious and can lead to
-code that is difficult to read and understand. It is best, therefore,
-to simply write additional initializations as separate statements
-preceding the @code{for} loop and to place additional increment statements
-at the end of the loop's body.
-
-Most often, @var{increment} is an increment expression, as in the earlier
-example. But this is not required; it can be any expression
-whatsoever. For example, the following statement prints all the powers of two
-between 1 and 100:
-
-@example
-for (i = 1; i <= 100; i *= 2)
- print i
-@end example
-
-If there is nothing to be done, any of the three expressions in the
-parentheses following the @code{for} keyword may be omitted. Thus,
-@w{@samp{for (; x > 0;)}} is equivalent to @w{@samp{while (x > 0)}}. If the
-@var{condition} is omitted, it is treated as true, effectively
-yielding an @dfn{infinite loop} (i.e., a loop that never terminates).
-
-In most cases, a @code{for} loop is an abbreviation for a @code{while}
-loop, as shown here:
-
-@example
-@var{initialization}
-while (@var{condition}) @{
- @var{body}
- @var{increment}
-@}
-@end example
-
-@cindex loops @subentry @code{continue} statement and
-@noindent
-The only exception is when the @code{continue} statement
-(@pxref{Continue Statement}) is used
-inside the loop. Changing a @code{for} statement to a @code{while}
-statement in this way can change the effect of the @code{continue}
-statement inside the loop.
-
-The @command{awk} language has a @code{for} statement in addition to a
-@code{while} statement because a @code{for} loop is often both less work to
-type and more natural to think of. Counting the number of iterations is
-very common in loops. It can be easier to think of this counting as part
-of looping rather than as something to do inside the loop.
-
-@cindex @code{in} operator
-There is an alternative version of the @code{for} loop, for iterating over
-all the indices of an array:
-
-@example
-for (i in array)
- @var{do something with} array[i]
-@end example
-
-@noindent
-@xref{Scanning an Array}
-for more information on this version of the @code{for} loop.
-
-@node Switch Statement
-@subsection The @code{switch} Statement
-@cindex @code{switch} statement
-@cindex @code{case} keyword
-@cindex @code{default} keyword
-
-This @value{SECTION} describes a @command{gawk}-specific feature.
-If @command{gawk} is in compatibility mode (@pxref{Options}),
-it is not available.
-
-The @code{switch} statement allows the evaluation of an expression and
-the execution of statements based on a @code{case} match. Case statements
-are checked for a match in the order they are defined. If no suitable
-@code{case} is found, the @code{default} section is executed, if supplied.
-
-Each @code{case} contains a single constant, be it numeric, string,
-or regexp. The @code{switch} expression is evaluated, and then each
-@code{case}'s constant is compared against the result in turn. The
-type of constant determines the comparison: numeric or string do the
-usual comparisons. A regexp constant (either regular, @code{/foo/}, or
-strongly typed, @code{@@/foo/}) does a regular expression match against
-the string value of the original expression. The general form of the
-@code{switch} statement looks like this:
-
-@example
-switch (@var{expression}) @{
-case @var{value or regular expression}:
- @var{case-body}
-default:
- @var{default-body}
-@}
-@end example
-
-Control flow in
-the @code{switch} statement works as it does in C. Once a match to a given
-case is made, the case statement bodies execute until a @code{break},
-@code{continue}, @code{next}, @code{nextfile}, or @code{exit} is encountered,
-or the end of the @code{switch} statement itself. For example:
-
-@example
-while ((c = getopt(ARGC, ARGV, "aksx")) != -1) @{
- switch (c) @{
- case "a":
- # report size of all files
- all_files = TRUE;
- break
- case "k":
- BLOCK_SIZE = 1024 # 1K block size
- break
- case "s":
- # do sums only
- sum_only = TRUE
- break
- case "x":
- # don't cross filesystems
- fts_flags = or(fts_flags, FTS_XDEV)
- break
- case "?":
- default:
- usage()
- break
- @}
-@}
-@end example
-
-Note that if none of the statements specified here halt execution
-of a matched @code{case} statement, execution falls through to the
-next @code{case} until execution halts. In this example, the
-@code{case} for @code{"?"} falls through to the @code{default}
-case, which is to call a function named @code{usage()}.
-(The @code{getopt()} function being called here is
-described in @ref{Getopt Function}.)
-
-@node Break Statement
-@subsection The @code{break} Statement
-@cindex @code{break} statement
-@cindex loops @subentry exiting
-@cindex loops @subentry @code{break} statement and
-
-The @code{break} statement jumps out of the innermost @code{for},
-@code{while}, or @code{do} loop that encloses it. The following example
-finds the smallest divisor of any integer, and also identifies prime
-numbers:
-
-@example
-@group
-# find smallest divisor of num
-@{
- num = $1
- for (divisor = 2; divisor * divisor <= num; divisor++) @{
- if (num % divisor == 0)
- break
- @}
-@end group
-@group
- if (num % divisor == 0)
- printf "Smallest divisor of %d is %d\n", num, divisor
- else
- printf "%d is prime\n", num
-@}
-@end group
-@end example
-
-When the remainder is zero in the first @code{if} statement, @command{awk}
-immediately @dfn{breaks out} of the containing @code{for} loop. This means
-that @command{awk} proceeds immediately to the statement following the loop
-and continues processing. (This is very different from the @code{exit}
-statement, which stops the entire @command{awk} program.
-@xref{Exit Statement}.)
-
-The following program illustrates how the @var{condition} of a @code{for}
-or @code{while} statement could be replaced with a @code{break} inside
-an @code{if}:
-
-@example
-# find smallest divisor of num
-@{
- num = $1
- for (divisor = 2; ; divisor++) @{
- if (num % divisor == 0) @{
- printf "Smallest divisor of %d is %d\n", num, divisor
- break
- @}
- if (divisor * divisor > num) @{
- printf "%d is prime\n", num
- break
- @}
- @}
-@}
-@end example
-
-The @code{break} statement is also used to break out of the
-@code{switch} statement.
-This is discussed in @ref{Switch Statement}.
-
-@c @cindex @code{break}, outside of loops
-@c @cindex historical features
-@c @cindex @command{awk} language, POSIX version
-@cindex POSIX @command{awk} @subentry @code{break} statement and
-@cindex dark corner @subentry @code{break} statement
-@cindex @command{gawk} @subentry @code{break} statement in
-@cindex Brian Kernighan's @command{awk}
-The @code{break} statement has no meaning when
-used outside the body of a loop or @code{switch}.
-However, although it was never documented,
-historical implementations of @command{awk} treated the @code{break}
-statement outside of a loop as if it were a @code{next} statement
-(@pxref{Next Statement}).
-@value{DARKCORNER}
-Recent versions of BWK @command{awk} no longer allow this usage,
-nor does @command{gawk}.
-
-@node Continue Statement
-@subsection The @code{continue} Statement
-
-@cindex @code{continue} statement
-Similar to @code{break}, the @code{continue} statement is used only inside
-@code{for}, @code{while}, and @code{do} loops. It skips
-over the rest of the loop body, causing the next cycle around the loop
-to begin immediately. Contrast this with @code{break}, which jumps out
-of the loop altogether.
-
-The @code{continue} statement in a @code{for} loop directs @command{awk} to
-skip the rest of the body of the loop and resume execution with the
-increment-expression of the @code{for} statement. The following program
-illustrates this fact:
-
-@example
-BEGIN @{
- for (x = 0; x <= 20; x++) @{
- if (x == 5)
- continue
- printf "%d ", x
- @}
- print ""
-@}
-@end example
-
-@noindent
-This program prints all the numbers from 0 to 20---except for 5, for
-which the @code{printf} is skipped. Because the increment @samp{x++}
-is not skipped, @code{x} does not remain stuck at 5. Contrast the
-@code{for} loop from the previous example with the following @code{while} loop:
-
-@example
-BEGIN @{
- x = 0
- while (x <= 20) @{
- if (x == 5)
- continue
- printf "%d ", x
- x++
- @}
- print ""
-@}
-@end example
-
-@noindent
-This program loops forever once @code{x} reaches 5, because
-the increment (@samp{x++}) is never reached.
-
-@c @cindex @code{continue}, outside of loops
-@c @cindex historical features
-@c @cindex @command{awk} language, POSIX version
-@cindex POSIX @command{awk} @subentry @code{continue} statement and
-@cindex dark corner @subentry @code{continue} statement
-@cindex @command{gawk} @subentry @code{continue} statement in
-@cindex Brian Kernighan's @command{awk}
-The @code{continue} statement has no special meaning with respect to the
-@code{switch} statement, nor does it have any meaning when used outside the
-body of a loop. Historical versions of @command{awk} treated a @code{continue}
-statement outside a loop the same way they treated a @code{break}
-statement outside a loop: as if it were a @code{next}
-statement
-@ifset FOR_PRINT
-(discussed in the following @value{SECTION}).
-@end ifset
-@ifclear FOR_PRINT
-(@pxref{Next Statement}).
-@end ifclear
-@value{DARKCORNER}
-Recent versions of BWK @command{awk} no longer work this way, nor
-does @command{gawk}.
-
-@node Next Statement
-@subsection The @code{next} Statement
-@cindex @code{next} statement
-
-The @code{next} statement forces @command{awk} to immediately stop processing
-the current record and go on to the next record. This means that no
-further rules are executed for the current record, and the rest of the
-current rule's action isn't executed.
-
-Contrast this with the effect of the @code{getline} function
-(@pxref{Getline}). That also causes
-@command{awk} to read the next record immediately, but it does not alter the
-flow of control in any way (i.e., the rest of the current action executes
-with a new input record).
-
-@cindex @command{awk} programs @subentry execution of
-At the highest level, @command{awk} program execution is a loop that reads
-an input record and then tests each rule's pattern against it. If you
-think of this loop as a @code{for} statement whose body contains the
-rules, then the @code{next} statement is analogous to a @code{continue}
-statement. It skips to the end of the body of this implicit loop and
-executes the increment (which reads another record).
-
-For example, suppose an @command{awk} program works only on records
-with four fields, and it shouldn't fail when given bad input. To avoid
-complicating the rest of the program, write a ``weed out'' rule near
-the beginning, in the following manner:
-
-@example
-NF != 4 @{
- printf("%s:%d: skipped: NF != 4\n", FILENAME, FNR) > "/dev/stderr"
- next
-@}
-@end example
-
-@noindent
-Because of the @code{next} statement,
-the program's subsequent rules won't see the bad record. The error
-message is redirected to the standard error output stream, as error
-messages should be.
-For more detail, see
-@ref{Special Files}.
-
-If the @code{next} statement causes the end of the input to be reached,
-then the code in any @code{END} rules is executed.
-@xref{BEGIN/END}.
-
-The @code{next} statement is not allowed inside @code{BEGINFILE} and
-@code{ENDFILE} rules. @xref{BEGINFILE/ENDFILE}.
-
-@c @cindex @code{next}, inside a user-defined function
-@cindex @command{awk} @subentry language, POSIX version
-@cindex @code{BEGIN} pattern @subentry @code{next}/@code{nextfile} statements
and
-@cindex @code{END} pattern @subentry @code{next}/@code{nextfile} statements and
-@cindex POSIX @command{awk} @subentry @code{next}/@code{nextfile} statements
and
-@cindex @code{next} statement @subentry user-defined functions and
-@cindex functions @subentry user-defined @subentry @code{next}/@code{nextfile}
statements and
-According to the POSIX standard, the behavior is undefined if the
-@code{next} statement is used in a @code{BEGIN} or @code{END} rule.
-@command{gawk} treats it as a syntax error. Although POSIX does not disallow
it,
-most other @command{awk} implementations don't allow the @code{next}
-statement inside function bodies (@pxref{User-defined}). Just as with any
-other @code{next} statement, a @code{next} statement inside a function
-body reads the next record and starts processing it with the first rule
-in the program.
-
-@node Nextfile Statement
-@subsection The @code{nextfile} Statement
-@cindex @code{nextfile} statement
-
-The @code{nextfile} statement
-is similar to the @code{next} statement.
-However, instead of abandoning processing of the current record, the
-@code{nextfile} statement instructs @command{awk} to stop processing the
-current @value{DF}.
-
-Upon execution of the @code{nextfile} statement,
-@code{FILENAME} is
-updated to the name of the next @value{DF} listed on the command line,
-@code{FNR} is reset to one,
-and processing
-starts over with the first rule in the program.
-If the @code{nextfile} statement causes the end of the input to be reached,
-then the code in any @code{END} rules is executed. An exception to this is
-when @code{nextfile} is invoked during execution of any statement in an
-@code{END} rule; in this case, it causes the program to stop immediately.
-@xref{BEGIN/END}.
-
-The @code{nextfile} statement is useful when there are many @value{DF}s
-to process but it isn't necessary to process every record in every file.
-Without @code{nextfile},
-in order to move on to the next @value{DF}, a program
-would have to continue scanning the unwanted records. The @code{nextfile}
-statement accomplishes this much more efficiently.
-
-In @command{gawk}, execution of @code{nextfile} causes additional things
-to happen: any @code{ENDFILE} rules are executed if @command{gawk} is
-not currently in an @code{END} rule, @code{ARGIND} is
-incremented, and any @code{BEGINFILE} rules are executed. (@code{ARGIND}
-hasn't been introduced yet. @xref{Built-in Variables}.)
-
-There is an additional, special, use case
-with @command{gawk}. @code{nextfile} is useful inside a @code{BEGINFILE}
-rule to skip over a file that would otherwise cause @command{gawk}
-to exit with a fatal error. In this special case, @code{ENDFILE} rules are not
-executed. @xref{BEGINFILE/ENDFILE}.
-
-Although it might seem that @samp{close(FILENAME)} would accomplish
-the same as @code{nextfile}, this isn't true. @code{close()} is
-reserved for closing files, pipes, and coprocesses that are
-opened with redirections. It is not related to the main processing that
-@command{awk} does with the files listed in @code{ARGV}.
-
-@quotation NOTE
-For many years, @code{nextfile} was a
-common extension. In September 2012, it was accepted for
-inclusion into the POSIX standard.
-See @uref{http://austingroupbugs.net/view.php?id=607, the Austin Group
website}.
-@end quotation
-
-@cindex functions @subentry user-defined @subentry @code{next}/@code{nextfile}
statements and
-@cindex @code{nextfile} statement @subentry user-defined functions and
-@cindex Brian Kernighan's @command{awk}
-@cindex @command{mawk} utility
-The current version of BWK @command{awk} and @command{mawk}
-also support @code{nextfile}. However, they don't allow the
-@code{nextfile} statement inside function bodies (@pxref{User-defined}).
-@command{gawk} does; a @code{nextfile} inside a function body reads the
-first record from the next file and starts processing it with the first
-rule in the program, just as any other @code{nextfile} statement.
-
-@node Exit Statement
-@subsection The @code{exit} Statement
-
-@cindex @code{exit} statement
-The @code{exit} statement causes @command{awk} to immediately stop
-executing the current rule and to stop processing input; any remaining input
-is ignored. The @code{exit} statement is written as follows:
-
-@display
-@code{exit} [@var{return code}]
-@end display
-
-@cindex @code{BEGIN} pattern @subentry @code{exit} statement and
-@cindex @code{END} pattern @subentry @code{exit} statement and
-When an @code{exit} statement is executed from a @code{BEGIN} rule, the
-program stops processing everything immediately. No input records are
-read. However, if an @code{END} rule is present,
-as part of executing the @code{exit} statement,
-the @code{END} rule is executed
-(@pxref{BEGIN/END}).
-If @code{exit} is used in the body of an @code{END} rule, it causes
-the program to stop immediately.
-
-An @code{exit} statement that is not part of a @code{BEGIN} or @code{END}
-rule stops the execution of any further automatic rules for the current
-record, skips reading any remaining input records, and executes the
-@code{END} rule if there is one. @command{gawk} also skips
-any @code{ENDFILE} rules; they do not execute.
-
-In such a case,
-if you don't want the @code{END} rule to do its job, set a variable
-to a nonzero value before the @code{exit} statement and check that variable in
-the @code{END} rule.
-@xref{Assert Function}
-for an example that does this.
-
-@cindex dark corner @subentry @code{exit} statement
-If an argument is supplied to @code{exit}, its value is used as the exit
-status code for the @command{awk} process. If no argument is supplied,
-@code{exit} causes @command{awk} to return a ``success'' status.
-In the case where an argument
-is supplied to a first @code{exit} statement, and then @code{exit} is
-called a second time from an @code{END} rule with no argument,
-@command{awk} uses the previously supplied exit value. @value{DARKCORNER}
-@xref{Exit Status} for more information.
-
-@cindex programming conventions @subentry @code{exit} statement
-For example, suppose an error condition occurs that is difficult or
-impossible to handle. Conventionally, programs report this by
-exiting with a nonzero status. An @command{awk} program can do this
-using an @code{exit} statement with a nonzero argument, as shown
-in the following example:
-
-@example
-@group
-BEGIN @{
- if (("date" | getline date_now) <= 0) @{
- print "Can't get system date" > "/dev/stderr"
- exit 1
- @}
-@end group
-@group
- print "current date is", date_now
- close("date")
-@}
-@end group
-@end example
-
-@quotation NOTE
-For full portability, exit values should be between zero and 126, inclusive.
-Negative values, and values of 127 or greater, may not produce consistent
-results across different operating systems.
-@end quotation
-
-
-@node Built-in Variables
-@section Predefined Variables
-@cindex predefined variables
-@cindex variables @subentry predefined
-
-Most @command{awk} variables are available to use for your own
-purposes; they never change unless your program assigns values to
-them, and they never affect anything unless your program examines them.
-However, a few variables in @command{awk} have special built-in meanings.
-@command{awk} examines some of these automatically, so that they enable you
-to tell @command{awk} how to do certain things. Others are set
-automatically by @command{awk}, so that they carry information from the
-internal workings of @command{awk} to your program.
-
-@cindex @command{gawk} @subentry predefined variables and
-This @value{SECTION} documents all of @command{gawk}'s predefined variables,
-most of which are also documented in the @value{CHAPTER}s describing
-their areas of activity.
-
-@menu
-* User-modified:: Built-in variables that you change to control
- @command{awk}.
-* Auto-set:: Built-in variables where @command{awk} gives
- you information.
-* ARGC and ARGV:: Ways to use @code{ARGC} and @code{ARGV}.
-@end menu
-
-@node User-modified
-@subsection Built-in Variables That Control @command{awk}
-@cindex predefined variables @subentry user-modifiable
-@cindex user-modifiable variables
-
-The following is an alphabetical list of variables that you can change to
-control how @command{awk} does certain things.
-
-The variables that are specific to @command{gawk} are marked with a pound
-sign (@samp{#}). These variables are @command{gawk} extensions. In other
-@command{awk} implementations or if @command{gawk} is in compatibility
-mode (@pxref{Options}), they are not special. (Any exceptions are noted
-in the description of each variable.)
-
-@table @code
-@cindex @code{BINMODE} variable
-@cindex binary input/output
-@cindex input/output @subentry binary
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{BINMODE} variable
-@item BINMODE #
-On non-POSIX systems, this variable specifies use of binary mode
-for all I/O. Numeric values of one, two, or three specify that input
-files, output files, or all files, respectively, should use binary I/O.
-A numeric value less than zero is treated as zero, and a numeric value
-greater than three is treated as three. Alternatively, string values
-of @code{"r"} or @code{"w"} specify that input files and output files,
-respectively, should use binary I/O. A string value of @code{"rw"} or
-@code{"wr"} indicates that all files should use binary I/O. Any other
-string value is treated the same as @code{"rw"}, but causes @command{gawk}
-to generate a warning message. @code{BINMODE} is described in more
-detail in @ref{PC Using}. @command{mawk} (@pxref{Other Versions})
-also supports this variable, but only using numeric values.
-
-@cindex @code{CONVFMT} variable
-@cindex POSIX @command{awk} @subentry @code{CONVFMT} variable and
-@cindex numbers @subentry converting @subentry to strings
-@cindex strings @subentry converting @subentry numbers to
-@item @code{CONVFMT}
-A string that controls the conversion of numbers to
-strings (@pxref{Conversion}).
-It works by being passed, in effect, as the first argument to the
-@code{sprintf()} function
-(@pxref{String Functions}).
-Its default value is @code{"%.6g"}.
-@code{CONVFMT} was introduced by the POSIX standard.
-
-@cindex @command{gawk} @subentry @code{FIELDWIDTHS} variable in
-@cindex @code{FIELDWIDTHS} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{FIELDWIDTHS} variable
-@cindex field separator @subentry @code{FIELDWIDTHS} variable and
-@cindex separators @subentry field @subentry @code{FIELDWIDTHS} variable and
-@item FIELDWIDTHS #
-A space-separated list of columns that tells @command{gawk}
-how to split input with fixed columnar boundaries.
-Starting in @value{PVERSION} 4.2, each field width may optionally be
-preceded by a colon-separated value specifying the number of characters to skip
-before the field starts.
-Assigning a value to @code{FIELDWIDTHS}
-overrides the use of @code{FS} and @code{FPAT} for field splitting.
-@xref{Constant Size} for more information.
-
-@cindex @command{gawk} @subentry @code{FPAT} variable in
-@cindex @code{FPAT} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry @code{FPAT}
variable
-@cindex field separator @subentry @code{FPAT} variable and
-@cindex separators @subentry field @subentry @code{FPAT} variable and
-@item FPAT #
-A regular expression (as a string) that tells @command{gawk}
-to create the fields based on text that matches the regular expression.
-Assigning a value to @code{FPAT}
-overrides the use of @code{FS} and @code{FIELDWIDTHS} for field splitting.
-@xref{Splitting By Content} for more information.
-
-@cindex @code{FS} variable
-@cindex separators @subentry field
-@cindex field separator
-@item FS
-The input field separator (@pxref{Field Separators}).
-The value is a single-character string or a multicharacter regular
-expression that matches the separations between fields in an input
-record. If the value is the null string (@code{""}), then each
-character in the record becomes a separate field.
-(This behavior is a @command{gawk} extension. POSIX @command{awk} does not
-specify the behavior when @code{FS} is the null string.
-Nonetheless, some other versions of @command{awk} also treat
-@code{""} specially.)
-
-The default value is @w{@code{" "}}, a string consisting of a single
-space. As a special exception, this value means that any sequence of
-spaces, TABs, and/or newlines is a single separator. It also causes
-spaces, TABs, and newlines at the beginning and end of a record to
-be ignored.
-
-You can set the value of @code{FS} on the command line using the
-@option{-F} option:
-
-@example
-awk -F, '@var{program}' @var{input-files}
-@end example
-
-@cindex @command{gawk} @subentry field separators and
-If @command{gawk} is using @code{FIELDWIDTHS} or @code{FPAT}
-for field splitting,
-assigning a value to @code{FS} causes @command{gawk} to return to
-the normal, @code{FS}-based field splitting. An easy way to do this
-is to simply say @samp{FS = FS}, perhaps with an explanatory comment.
-
-@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
-@cindex @code{IGNORECASE} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{IGNORECASE} variable
-@cindex case sensitivity @subentry string comparisons and
-@cindex case sensitivity @subentry regexps and
-@cindex regular expressions @subentry case sensitivity
-@item IGNORECASE #
-If @code{IGNORECASE} is nonzero or non-null, then all string comparisons
-and all regular expression matching are case-independent.
-This applies to
-regexp matching with @samp{~} and @samp{!~},
-the @code{gensub()}, @code{gsub()}, @code{index()}, @code{match()},
-@code{patsplit()}, @code{split()}, and @code{sub()} functions,
-record termination with @code{RS}, and field splitting with
-@code{FS} and @code{FPAT}.
-However, the value of @code{IGNORECASE} does @emph{not} affect array
subscripting
-and it does not affect field splitting when using a single-character
-field separator.
-@xref{Case-sensitivity}.
-
-@cindex @command{gawk} @subentry @code{LINT} variable in
-@cindex @code{LINT} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry @code{LINT}
variable
-@cindex lint checking
-@item LINT #
-When this variable is true (nonzero or non-null), @command{gawk}
-behaves as if the @option{--lint} command-line option is in effect
-(@pxref{Options}).
-With a value of @code{"fatal"}, lint warnings become fatal errors.
-With a value of @code{"invalid"}, only warnings about things that are
-actually invalid are issued. (This is not fully implemented yet.)
-Any other true value prints nonfatal warnings.
-Assigning a false value to @code{LINT} turns off the lint warnings.
-
-This variable is a @command{gawk} extension. It is not special
-in other @command{awk} implementations. Unlike with the other special
variables,
-changing @code{LINT} does affect the production of lint warnings,
-even if @command{gawk} is in compatibility mode. Much as
-the @option{--lint} and @option{--traditional} options independently
-control different aspects of @command{gawk}'s behavior, the control
-of lint warnings during program execution is independent of the flavor
-of @command{awk} being executed.
-
-@cindex @code{OFMT} variable
-@cindex numbers @subentry converting @subentry to strings
-@cindex strings @subentry converting @subentry numbers to
-@item OFMT
-A string that controls conversion of numbers to
-strings (@pxref{Conversion}) for
-printing with the @code{print} statement. It works by being passed
-as the first argument to the @code{sprintf()} function
-(@pxref{String Functions}).
-Its default value is @code{"%.6g"}. Earlier versions of @command{awk}
-used @code{OFMT} to specify the format for converting numbers to
-strings in general expressions; this is now done by @code{CONVFMT}.
-
-@cindex @code{print} statement @subentry @code{OFMT} variable and
-@cindex @code{OFS} variable
-@cindex separators @subentry field
-@cindex field separator
-@item OFS
-The output field separator (@pxref{Output Separators}). It is
-output between the fields printed by a @code{print} statement. Its
-default value is @w{@code{" "}}, a string consisting of a single space.
-
-@cindex @code{ORS} variable
-@item ORS
-The output record separator. It is output at the end of every
-@code{print} statement. Its default value is @code{"\n"}, the newline
-character. (@xref{Output Separators}.)
-
-@cindex @code{PREC} variable
-@item PREC #
-The working precision of arbitrary-precision floating-point numbers,
-53 bits by default (@pxref{Setting precision}).
-
-@cindex @code{ROUNDMODE} variable
-@item ROUNDMODE #
-The rounding mode to use for arbitrary-precision arithmetic on
-numbers, by default @code{"N"} (@code{roundTiesToEven} in
-the IEEE 754 standard; @pxref{Setting the rounding mode}).
-
-@cindex @code{RS} variable
-@cindex separators @subentry for records
-@cindex record separators
-@item @code{RS}
-The input record separator. Its default value is a string
-containing a single newline character, which means that an input record
-consists of a single line of text.
-It can also be the null string, in which case records are separated by
-runs of blank lines.
-If it is a regexp, records are separated by
-matches of the regexp in the input text.
-(@xref{Records}.)
-
-The ability for @code{RS} to be a regular expression
-is a @command{gawk} extension.
-In most other @command{awk} implementations,
-or if @command{gawk} is in compatibility mode
-(@pxref{Options}),
-just the first character of @code{RS}'s value is used.
-
-@cindex @code{SUBSEP} variable
-@cindex separators @subentry subscript
-@cindex subscript separators
-@item @code{SUBSEP}
-The subscript separator. It has the default value of
-@code{"\034"} and is used to separate the parts of the indices of a
-multidimensional array. Thus, the expression @samp{@w{foo["A", "B"]}}
-really accesses @code{foo["A\034B"]}
-(@pxref{Multidimensional}).
-
-@cindex @command{gawk} @subentry @code{TEXTDOMAIN} variable in
-@cindex @code{TEXTDOMAIN} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{TEXTDOMAIN} variable
-@cindex internationalization @subentry localization
-@item TEXTDOMAIN #
-Used for internationalization of programs at the
-@command{awk} level. It sets the default text domain for specially
-marked string constants in the source text, as well as for the
-@code{dcgettext()}, @code{dcngettext()}, and @code{bindtextdomain()} functions
-(@pxref{Internationalization}).
-The default value of @code{TEXTDOMAIN} is @code{"messages"}.
-@end table
-
-@node Auto-set
-@subsection Built-in Variables That Convey Information
-
-@cindex predefined variables @subentry conveying information
-@cindex variables @subentry predefined @subentry conveying information
-The following is an alphabetical list of variables that @command{awk}
-sets automatically on certain occasions in order to provide
-information to your program.
-
-The variables that are specific to @command{gawk} are marked with a pound
-sign (@samp{#}). These variables are @command{gawk} extensions. In other
-@command{awk} implementations or if @command{gawk} is in compatibility
-mode (@pxref{Options}), they are not special:
-
-@c @asis for docbook
-@table @asis
-@cindex @code{ARGC}/@code{ARGV} variables
-@cindex arguments @subentry command-line
-@cindex command line @subentry arguments
-@item @code{ARGC}, @code{ARGV}
-The command-line arguments available to @command{awk} programs are stored in
-an array called @code{ARGV}. @code{ARGC} is the number of command-line
-arguments present. @xref{Other Arguments}.
-Unlike most @command{awk} arrays,
-@code{ARGV} is indexed from 0 to @code{ARGC} @minus{} 1.
-In the following example:
-
-@example
-@group
-$ @kbd{awk 'BEGIN @{}
-> @kbd{for (i = 0; i < ARGC; i++)}
-> @kbd{print ARGV[i]}
-> @kbd{@}' inventory-shipped mail-list}
-@print{} awk
-@print{} inventory-shipped
-@print{} mail-list
-@end group
-@end example
-
-@noindent
-@code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]}
-contains @samp{inventory-shipped}, and @code{ARGV[2]} contains
-@samp{mail-list}. The value of @code{ARGC} is three, one more than the
-index of the last element in @code{ARGV}, because the elements are numbered
-from zero.
-
-@cindex programming conventions @subentry @code{ARGC}/@code{ARGV} variables
-The names @code{ARGC} and @code{ARGV}, as well as the convention of indexing
-the array from 0 to @code{ARGC} @minus{} 1, are derived from the C language's
-method of accessing command-line arguments.
-
-@cindex dark corner @subentry value of @code{ARGV[0]}
-The value of @code{ARGV[0]} can vary from system to system.
-Also, you should note that the program text is @emph{not} included in
-@code{ARGV}, nor are any of @command{awk}'s command-line options.
-@xref{ARGC and ARGV} for information
-about how @command{awk} uses these variables.
-@value{DARKCORNER}
-
-@cindex @code{ARGIND} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{ARGIND} variable
-@item @code{ARGIND #}
-The index in @code{ARGV} of the current file being processed.
-Every time @command{gawk} opens a new @value{DF} for processing, it sets
-@code{ARGIND} to the index in @code{ARGV} of the @value{FN}.
-When @command{gawk} is processing the input files,
-@samp{FILENAME == ARGV[ARGIND]} is always true.
-
-@cindex files @subentry processing, @code{ARGIND} variable and
-This variable is useful in file processing; it allows you to tell how far
-along you are in the list of @value{DF}s as well as to distinguish between
-successive instances of the same @value{FN} on the command line.
-
-@cindex file names @subentry distinguishing
-While you can change the value of @code{ARGIND} within your @command{awk}
-program, @command{gawk} automatically sets it to a new value when it
-opens the next file.
-
-@cindex @code{ENVIRON} array
-@cindex environment variables @subentry in @code{ENVIRON} array
-@item @code{ENVIRON}
-An associative array containing the values of the environment. The array
-indices are the environment variable names; the elements are the values of
-the particular environment variables. For example,
-@code{ENVIRON["HOME"]} might be @code{/home/arnold}.
-
-For POSIX @command{awk}, changing this array does not affect the
-environment passed on to any programs that @command{awk} may spawn via
-redirection or the @code{system()} function.
-
-However, beginning with @value{PVERSION} 4.2, if not in POSIX
-compatibility mode, @command{gawk} does update its own environment when
-@code{ENVIRON} is changed, thus changing the environment seen by programs
-that it creates. You should therefore be especially careful if you
-modify @code{ENVIRON["PATH"]}, which is the search path for finding
-executable programs.
-
-@cindex @env{TZ} environment variable
-@cindex environment variables @subentry @env{TZ}
-This can also affect the running @command{gawk} program, since some of the
-built-in functions may pay attention to certain environment variables.
-The most notable instance of this is @code{mktime()} (@pxref{Time
-Functions}), which pays attention the value of the @env{TZ} environment
-variable on many systems.
-
-Some operating systems may not have environment variables.
-On such systems, the @code{ENVIRON} array is empty (except for
-@w{@code{ENVIRON["AWKPATH"]}} and
-@w{@code{ENVIRON["AWKLIBPATH"]}};
-@pxref{AWKPATH Variable} and
-@ifdocbook
-@ref{AWKLIBPATH Variable}).
-@end ifdocbook
-@ifnotdocbook
-@pxref{AWKLIBPATH Variable}).
-@end ifnotdocbook
-
-@cindex @command{gawk} @subentry @code{ERRNO} variable in
-@cindex @code{ERRNO} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry @code{ERRNO}
variable
-@cindex error handling @subentry @code{ERRNO} variable and
-@item @code{ERRNO #}
-If a system error occurs during a redirection for @code{getline}, during
-a read for @code{getline}, or during a @code{close()} operation, then
-@code{ERRNO} contains a string describing the error.
-
-In addition, @command{gawk} clears @code{ERRNO} before opening each
-command-line input file. This enables checking if the file is readable
-inside a @code{BEGINFILE} pattern (@pxref{BEGINFILE/ENDFILE}).
-
-Otherwise, @code{ERRNO} works similarly to the C variable @code{errno}.
-Except for the case just mentioned, @command{gawk} @emph{never} clears
-it (sets it to zero or @code{""}). Thus, you should only expect its
-value to be meaningful when an I/O operation returns a failure value,
-such as @code{getline} returning @minus{}1. You are, of course, free
-to clear it yourself before doing an I/O operation.
-
-If the value of @code{ERRNO} corresponds to a system error in the C
-@code{errno} variable, then @code{PROCINFO["errno"]} will be set to the value
-of @code{errno}. For non-system errors, @code{PROCINFO["errno"]} will
-be zero.
-
-@cindex @code{FILENAME} variable
-@cindex dark corner @subentry @code{FILENAME} variable
-@item @code{FILENAME}
-The name of the current input file. When no @value{DF}s are listed
-on the command line, @command{awk} reads from the standard input and
-@code{FILENAME} is set to @code{"-"}. @code{FILENAME} changes each
-time a new file is read (@pxref{Reading Files}). Inside a @code{BEGIN}
-rule, the value of @code{FILENAME} is @code{""}, because there are no input
-files being processed yet.@footnote{Some early implementations of Unix
-@command{awk} initialized @code{FILENAME} to @code{"-"}, even if there
-were @value{DF}s to be processed. This behavior was incorrect and should
-not be relied upon in your programs.} @value{DARKCORNER} Note, though,
-that using @code{getline} (@pxref{Getline}) inside a @code{BEGIN} rule
-can give @code{FILENAME} a value.
-
-@cindex @code{FNR} variable
-@item @code{FNR}
-The current record number in the current file. @command{awk} increments
-@code{FNR} each time it reads a new record (@pxref{Records}).
-@command{awk} resets @code{FNR} to zero each time it starts a new
-input file.
-
-@cindex @code{NF} variable
-@item @code{NF}
-The number of fields in the current input record.
-@code{NF} is set each time a new record is read, when a new field is
-created, or when @code{$0} changes (@pxref{Fields}).
-
-Unlike most of the variables described in this @value{SUBSECTION},
-assigning a value to @code{NF} has the potential to affect
-@command{awk}'s internal workings. In particular, assignments
-to @code{NF} can be used to create fields in or remove fields from the
-current record. @xref{Changing Fields}.
-
-@cindex @code{FUNCTAB} array
-@cindex @command{gawk} @subentry @code{FUNCTAB} array in
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{FUNCTAB} variable
-@item @code{FUNCTAB #}
-An array whose indices and corresponding values are the names of all
-the built-in, user-defined, and extension functions in the program.
-
-@quotation NOTE
-Attempting to use the @code{delete} statement with the @code{FUNCTAB}
-array causes a fatal error. Any attempt to assign to an element of
-@code{FUNCTAB} also causes a fatal error.
-@end quotation
-
-@cindex @code{NR} variable
-@item @code{NR}
-The number of input records @command{awk} has processed since
-the beginning of the program's execution
-(@pxref{Records}).
-@command{awk} increments @code{NR} each time it reads a new record.
-
-@cindex @command{gawk} @subentry @code{PROCINFO} array in
-@cindex @code{PROCINFO} array
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{PROCINFO} array
-@item @code{PROCINFO #}
-The elements of this array provide access to information about the
-running @command{awk} program.
-The following elements (listed alphabetically)
-are guaranteed to be available:
-
-@table @code
-@item PROCINFO["argv"]
-@cindex command line @subentry arguments
-The @code{PROCINFO["argv"]} array contains all of the command-line arguments
-(after glob expansion and redirection processing on platforms where that must
-be done manually by the program) with subscripts ranging from 0 through
-@code{argc} @minus{} 1. For example, @code{PROCINFO["argv"][0]} will contain
-the name by which @command{gawk} was invoked. Here is an example of how this
-feature may be used:
-
-@example
-gawk '
-BEGIN @{
- for (i = 0; i < length(PROCINFO["argv"]); i++)
- print i, PROCINFO["argv"][i]
-@}'
-@end example
-
-Please note that this differs from the standard @code{ARGV} array which does
-not include command-line arguments that have already been processed by
-@command{gawk} (@pxref{ARGC and ARGV}).
-
-@cindex effective group ID of @command{gawk} user
-@item PROCINFO["egid"]
-The value of the @code{getegid()} system call.
-
-@item PROCINFO["errno"]
-The value of the C @code{errno} variable when @code{ERRNO} is set to
-the associated error message.
-
-@item PROCINFO["euid"]
-@cindex effective user ID of @command{gawk} user
-The value of the @code{geteuid()} system call.
-
-@item PROCINFO["FS"]
-This is
-@code{"FS"} if field splitting with @code{FS} is in effect,
-@code{"FIELDWIDTHS"} if field splitting with @code{FIELDWIDTHS} is in effect,
-@code{"FPAT"} if field matching with @code{FPAT} is in effect,
-or @code{"API"} if field splitting is controlled by an API input parser.
-
-@item PROCINFO["gid"]
-@cindex group ID of @command{gawk} user
-The value of the @code{getgid()} system call.
-
-@item PROCINFO["identifiers"]
-@cindex program identifiers
-A subarray, indexed by the names of all identifiers used in the text of
-the @command{awk} program. An @dfn{identifier} is simply the name of a
variable
-(be it scalar or array), built-in function, user-defined function, or
-extension function. For each identifier, the value of the element is
-one of the following:
-
-@table @code
-@item "array"
-The identifier is an array.
-
-@item "builtin"
-The identifier is a built-in function.
-
-@item "extension"
-The identifier is an extension function loaded via
-@code{@@load} or @option{-l}.
-
-@item "scalar"
-The identifier is a scalar.
-
-@item "untyped"
-The identifier is untyped (could be used as a scalar or an array;
-@command{gawk} doesn't know yet).
-
-@item "user"
-The identifier is a user-defined function.
-@end table
-
-@noindent
-The values indicate what @command{gawk} knows about the identifiers
-after it has finished parsing the program; they are @emph{not} updated
-while the program runs.
-
-@item PROCINFO["platform"]
-@cindex platform running on
-@cindex @code{PROCINFO} array @subentry platform running on
-This element gives a string indicating the platform for which
-@command{gawk} was compiled. The value will be one of the following:
-
-@c nested table
-@table @code
-@item "mingw"
-Microsoft Windows, using MinGW.
-
-@item "os390"
-OS/390 (also known as z/OS).
-
-@item "posix"
-GNU/Linux, Cygwin, macOS, and legacy Unix systems.
-
-@item "vms"
-OpenVMS.
-@end table
-
-@item PROCINFO["pgrpid"]
-@cindex process group ID of @command{gawk} process
-The process group ID of the current process.
-
-@item PROCINFO["pid"]
-@cindex process ID of @command{gawk} process
-The process ID of the current process.
-
-@item PROCINFO["pma"]
-@cindex persistent memory @subentry compiled into @command{gawk}
-@cindex PMA memory allocator
-The version of the PMA memory allocator compiled into @command{gawk}.
-This element will not be present if the PMA allocator is not available
-for use. @xref{Persistent Memory}.
-
-@item PROCINFO["ppid"]
-@cindex parent process ID of @command{gawk} process
-The parent process ID of the current process.
-
-@item PROCINFO["strftime"]
-The default time format string for @code{strftime()}.
-Assigning a new value to this element changes the default.
-@xref{Time Functions}.
-
-@item PROCINFO["uid"]
-The value of the @code{getuid()} system call.
-
-@item PROCINFO["version"]
-@cindex version of @subentry @command{gawk}
-@cindex @command{gawk} @subentry version of
-The version of @command{gawk}.
-@end table
-
-The following additional elements in the array
-are available to provide information about the MPFR and GMP libraries
-if your version of @command{gawk} supports arbitrary-precision arithmetic
-(@pxref{Arbitrary Precision Arithmetic}):
-
-@table @code
-@item PROCINFO["gmp_version"]
-@cindex version of @subentry GNU MP library
-The version of the GNU MP library.
-
-@cindex version of @subentry GNU MPFR library
-@item PROCINFO["mpfr_version"]
-The version of the GNU MPFR library.
-
-@item PROCINFO["prec_max"]
-@cindex maximum precision supported by MPFR library
-The maximum precision supported by MPFR.
-
-@item PROCINFO["prec_min"]
-@cindex minimum precision required by MPFR library
-The minimum precision required by MPFR.
-@end table
-
-The following additional elements in the array are available to provide
-information about the version of the extension API, if your version
-of @command{gawk} supports dynamic loading of extension functions
-(@pxref{Dynamic Extensions}):
-
-@table @code
-@item PROCINFO["api_major"]
-@cindex version of @subentry @command{gawk} extension API
-@cindex extension API @subentry version number
-The major version of the extension API.
-
-@item PROCINFO["api_minor"]
-The minor version of the extension API.
-@end table
-
-@cindex supplementary groups of @command{gawk} process
-On some systems, there may be elements in the array, @code{"group1"}
-through @code{"group@var{N}"} for some @var{N}. @var{N} is the number of
-supplementary groups that the process has. Use the @code{in} operator
-to test for these elements
-(@pxref{Reference to Elements}).
-
-The following elements allow you to change @command{gawk}'s behavior:
-
-@table @code
-@item PROCINFO["BUFFERPIPE"]
-If this element exists, all output to pipelines becomes buffered.
-@xref{Noflush}.
-
-@item PROCINFO["@var{command}", "BUFFERPIPE"]
-Make output to @var{command} buffered.
-@xref{Noflush}.
-
-@item PROCINFO["NONFATAL"]
-If this element exists, then I/O errors for all redirections become nonfatal.
-@xref{Nonfatal}.
-
-@item PROCINFO["@var{name}", "NONFATAL"]
-Make I/O errors for @var{name} be nonfatal.
-@xref{Nonfatal}.
-
-@item PROCINFO["@var{command}", "pty"]
-For two-way communication to @var{command}, use a pseudo-tty instead
-of setting up a two-way pipe.
-@xref{Two-way I/O} for more information.
-
-@item PROCINFO["@var{input_name}", "READ_TIMEOUT"]
-Set a timeout for reading from input redirection @var{input_name}.
-@xref{Read Timeout} for more information.
-
-@item PROCINFO["@var{input_name}", "RETRY"]
-If an I/O error that may be retried occurs when reading data from
-@var{input_name}, and this array entry exists, then @code{getline} returns
-@minus{}2 instead of following the default behavior of returning @minus{}1
-and configuring @var{input_name} to return no further data. An I/O error
-that may be retried is one where @code{errno} has the value @code{EAGAIN},
-@code{EWOULDBLOCK}, @code{EINTR}, or @code{ETIMEDOUT}. This may be useful
-in conjunction with @code{PROCINFO["@var{input_name}", "READ_TIMEOUT"]}
-or situations where a file descriptor has been configured to behave in
-a non-blocking fashion.
-@xref{Retrying Input} for more information.
-
-@item PROCINFO["sorted_in"]
-If this element exists in @code{PROCINFO}, its value controls the
-order in which array indices will be processed by
-@samp{for (@var{indx} in @var{array})} loops.
-This is an advanced feature, so we defer the
-full description until later; see
-@ref{Controlling Scanning}.
-@end table
-
-@cindex @code{RLENGTH} variable
-@item @code{RLENGTH}
-The length of the substring matched by the
-@code{match()} function
-(@pxref{String Functions}).
-@code{RLENGTH} is set by invoking the @code{match()} function. Its value
-is the length of the matched string, or @minus{}1 if no match is found.
-
-@cindex @code{RSTART} variable
-@item @code{RSTART}
-The start index in characters of the substring that is matched by the
-@code{match()} function
-(@pxref{String Functions}).
-@code{RSTART} is set by invoking the @code{match()} function. Its value
-is the position of the string where the matched substring starts, or zero
-if no match was found.
-
-@cindex @command{gawk} @subentry @code{RT} variable in
-@cindex @code{RT} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{RS}/@code{RT} variables
-@item @code{RT #}
-The input text that matched the text denoted by @code{RS},
-the record separator. It is set every time a record is read.
-
-@cindex @command{gawk} @subentry @code{SYMTAB} array in
-@cindex @code{SYMTAB} array
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{SYMTAB} variable
-@item @code{SYMTAB #}
-An array whose indices are the names of all defined global variables and
-arrays in the program. @code{SYMTAB} makes @command{gawk}'s symbol table
-visible to the @command{awk} programmer. It is built as @command{gawk}
-parses the program and is complete before the program starts to run.
-
-The array may be used for indirect access to read or write the value of
-a variable:
-
-@example
-foo = 5
-SYMTAB["foo"] = 4
-print foo # prints 4
-@end example
-
-@noindent
-The @code{isarray()} function (@pxref{Type Functions}) may be used to test
-if an element in @code{SYMTAB} is an array.
-Also, you may not use the @code{delete} statement with the
-@code{SYMTAB} array.
-
-Prior to @value{PVERSION} 5.0 of @command{gawk}, you could
-use an index for @code{SYMTAB} that was not a predefined identifier:
-
-@example
-SYMTAB["xxx"] = 5
-print SYMTAB["xxx"]
-@end example
-
-@noindent
-This no longer works, instead producing a fatal error, as it led
-to rampant confusion.
-
-@cindex Schorr, Andrew
-The @code{SYMTAB} array is more interesting than it looks. Andrew Schorr
-points out that it effectively gives @command{awk} data pointers. Consider his
-example:
-
-@example
-@group
-# Indirect multiply of any variable by amount, return result
-
-function multiply(variable, amount)
-@{
- return SYMTAB[variable] *= amount
-@}
-@end group
-@end example
-
-@noindent
-You would use it like this:
-
-@example
-BEGIN @{
- answer = 10.5
- multiply("answer", 4)
- print "The answer is", answer
-@}
-@end example
-
-@noindent
-When run, this produces:
-
-@example
-$ @kbd{gawk -f answer.awk}
-@print{} The answer is 42
-@end example
-
-@quotation NOTE
-In order to avoid severe time-travel paradoxes,@footnote{Not to mention
-difficult implementation issues.} neither @code{FUNCTAB} nor @code{SYMTAB}
-is available as an element within the @code{SYMTAB} array.
-@end quotation
-@end table
-
-@sidebar Changing @code{NR} and @code{FNR}
-@cindex @code{NR} variable @subentry changing
-@cindex @code{FNR} variable @subentry changing
-@cindex dark corner @subentry @code{FNR}/@code{NR} variables
-@command{awk} increments @code{NR} and @code{FNR}
-each time it reads a record, instead of setting them to the absolute
-value of the number of records read. This means that a program can
-change these variables and their new values are incremented for
-each record.
-@value{DARKCORNER}
-The following example shows this:
-
-@example
-$ @kbd{echo '1}
-> @kbd{2}
-> @kbd{3}
-> @kbd{4' | awk 'NR == 2 @{ NR = 17 @}}
-> @kbd{@{ print NR @}'}
-@print{} 1
-@print{} 17
-@print{} 18
-@print{} 19
-@end example
-
-@noindent
-Before @code{FNR} was added to the @command{awk} language
-(@pxref{V7/SVR3.1}),
-many @command{awk} programs used this feature to track the number of
-records in a file by resetting @code{NR} to zero when @code{FILENAME}
-changed.
-@end sidebar
-
-@node ARGC and ARGV
-@subsection Using @code{ARGC} and @code{ARGV}
-@cindex @code{ARGC}/@code{ARGV} variables @subentry how to use
-@cindex arguments @subentry command-line
-@cindex command line @subentry arguments
-
-@ref{Auto-set}
-presented the following program describing the information contained in
@code{ARGC}
-and @code{ARGV}:
-
-@example
-@group
-$ @kbd{awk 'BEGIN @{}
-> @kbd{for (i = 0; i < ARGC; i++)}
-> @kbd{print ARGV[i]}
-> @kbd{@}' inventory-shipped mail-list}
-@print{} awk
-@print{} inventory-shipped
-@print{} mail-list
-@end group
-@end example
-
-@noindent
-In this example, @code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]}
-contains @samp{inventory-shipped}, and @code{ARGV[2]} contains
-@samp{mail-list}.
-Notice that the @command{awk} program is not entered in @code{ARGV}. The
-other command-line options, with their arguments, are also not
-entered. This includes variable assignments done with the @option{-v}
-option (@pxref{Options}).
-Normal variable assignments on the command line @emph{are}
-treated as arguments and do show up in the @code{ARGV} array.
-Given the following program in a file named @file{showargs.awk}:
-
-@example
-BEGIN @{
- printf "A=%d, B=%d\n", A, B
- for (i = 0; i < ARGC; i++)
- printf "\tARGV[%d] = %s\n", i, ARGV[i]
-@}
-END @{ printf "A=%d, B=%d\n", A, B @}
-@end example
-
-@noindent
-Running it produces the following:
-
-@example
-$ @kbd{awk -v A=1 -f showargs.awk B=2 /dev/null}
-@print{} A=1, B=0
-@print{} ARGV[0] = awk
-@print{} ARGV[1] = B=2
-@print{} ARGV[2] = /dev/null
-@print{} A=1, B=2
-@end example
-
-A program can alter @code{ARGC} and the elements of @code{ARGV}.
-Each time @command{awk} reaches the end of an input file, it uses the next
-element of @code{ARGV} as the name of the next input file. By storing a
-different string there, a program can change which files are read.
-Use @code{"-"} to represent the standard input. Storing
-additional elements and incrementing @code{ARGC} causes
-additional files to be read.
-
-If the value of @code{ARGC} is decreased, that eliminates input files
-from the end of the list. By recording the old value of @code{ARGC}
-elsewhere, a program can treat the eliminated arguments as
-something other than @value{FN}s.
-
-To eliminate a file from the middle of the list, store the null string
-(@code{""}) into @code{ARGV} in place of the file's name. As a
-special feature, @command{awk} ignores @value{FN}s that have been
-replaced with the null string.
-Another option is to
-use the @code{delete} statement to remove elements from
-@code{ARGV} (@pxref{Delete}).
-
-All of these actions are typically done in the @code{BEGIN} rule,
-before actual processing of the input begins.
-@xref{Split Program} and
-@ifnotdocbook
-@pxref{Tee Program}
-@end ifnotdocbook
-@ifdocbook
-@ref{Tee Program}
-@end ifdocbook
-for examples
-of each way of removing elements from @code{ARGV}.
-
-To actually get options into an @command{awk} program,
-end the @command{awk} options with @option{--} and then supply
-the @command{awk} program's options, in the following manner:
-
-@example
-awk -f myprog.awk -- -v -q file1 file2 @dots{}
-@end example
-
-The following fragment processes @code{ARGV} in order to examine, and
-then remove, the previously mentioned command-line options:
-
-@example
-BEGIN @{
- for (i = 1; i < ARGC; i++) @{
- if (ARGV[i] == "-v")
- verbose = 1
- else if (ARGV[i] == "-q")
- debug = 1
- else if (ARGV[i] ~ /^-./) @{
- e = sprintf("%s: unrecognized option -- %c",
- ARGV[0], substr(ARGV[i], 2, 1))
- print e > "/dev/stderr"
- @} else
- break
- delete ARGV[i]
- @}
-@}
-@end example
-
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{ARGC}/@code{ARGV} variables
-Ending the @command{awk} options with @option{--} isn't
-necessary in @command{gawk}. Unless @option{--posix} has
-been specified, @command{gawk} silently puts any unrecognized options
-into @code{ARGV} for the @command{awk} program to deal with. As soon
-as it sees an unknown option, @command{gawk} stops looking for other
-options that it might otherwise recognize. The previous command line with
-@command{gawk} would be:
-
-@example
-gawk -f myprog.awk -q -v file1 file2 @dots{}
-@end example
-
-@noindent
-Because @option{-q} is not a valid @command{gawk} option, it and the
-following @option{-v} are passed on to the @command{awk} program.
-(@xref{Getopt Function} for an @command{awk} library function that
-parses command-line options.)
-
-When designing your program, you should choose options that don't
-conflict with @command{gawk}'s, because it will process any options
-that it accepts before passing the rest of the command line on to
-your program. Using @samp{#!} with the @option{-E} option may help
-(@pxref{Executable Scripts}
-and
-@ifnotdocbook
-@pxref{Options}).
-@end ifnotdocbook
-@ifdocbook
-@ref{Options}).
-@end ifdocbook
-
-@node Pattern Action Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Pattern--action pairs make up the basic elements of an @command{awk}
-program. Patterns are either normal expressions, range expressions,
-or regexp constants; one of the special keywords @code{BEGIN}, @code{END},
-@code{BEGINFILE}, or @code{ENDFILE}; or empty. The action executes if
-the current record matches the pattern. Empty (missing) patterns match
-all records.
-
-@item
-I/O from @code{BEGIN} and @code{END} rules has certain constraints.
-This is also true, only more so, for @code{BEGINFILE} and @code{ENDFILE}
-rules. The latter two give you ``hooks'' into @command{gawk}'s file
-processing, allowing you to recover from a file that otherwise would
-cause a fatal error (such as a file that cannot be opened).
-
-@item
-Shell variables can be used in @command{awk} programs by careful
-use of shell quoting. It is easier to pass a shell variable into
-@command{awk} by using the @option{-v} option and an @command{awk}
-variable.
-
-@item
-Actions consist of statements enclosed in curly braces. Statements
-are built up from expressions, control statements, compound statements,
-input and output statements, and deletion statements.
-
-@item
-The control statements in @command{awk} are @code{if}-@code{else},
-@code{while}, @code{for}, and @code{do}-@code{while}. @command{gawk}
-adds the @code{switch} statement. There are two flavors of @code{for}
-statement: one for performing general looping, and the other for iterating
-through an array.
-
-@item
-@code{break} and @code{continue} let you exit early or start the next
-iteration of a loop (or get out of a @code{switch}).
-
-@item
-@code{next} and @code{nextfile} let you read the next record and start
-over at the top of your program or skip to the next input file and
-start over, respectively.
-
-@item
-The @code{exit} statement terminates your program. When executed
-from an action (or function body), it transfers control to the
-@code{END} statements. From an @code{END} statement body, it exits
-immediately. You may pass an optional numeric value to be used
-as @command{awk}'s exit status.
-
-@item
-Some predefined variables provide control over @command{awk}, mainly for I/O.
-Other variables convey information from @command{awk} to your program.
-
-@item
-@code{ARGC} and @code{ARGV} make the command-line arguments available
-to your program. Manipulating them from a @code{BEGIN} rule lets you
-control how @command{awk} will process the provided @value{DF}s.
-
-@end itemize
-
-@node Arrays
-@chapter Arrays in @command{awk}
-@cindex arrays
-
-An @dfn{array} is a table of values called @dfn{elements}. The
-elements of an array are distinguished by their @dfn{indices}. Indices
-may be either numbers or strings.
-
-This @value{CHAPTER} describes how arrays work in @command{awk},
-how to use array elements, how to scan through every element in an array,
-and how to remove array elements.
-It also describes how @command{awk} simulates multidimensional
-arrays, as well as some of the less obvious points about array usage.
-The @value{CHAPTER} moves on to discuss @command{gawk}'s facility
-for sorting arrays, and ends with a brief description of @command{gawk}'s
-ability to support true arrays of arrays.
-
-@menu
-* Array Basics:: The basics of arrays.
-* Numeric Array Subscripts:: How to use numbers as subscripts in
- @command{awk}.
-* Uninitialized Subscripts:: Using Uninitialized variables as subscripts.
-* Delete:: The @code{delete} statement removes an element
- from an array.
-* Multidimensional:: Emulating multidimensional arrays in
- @command{awk}.
-* Arrays of Arrays:: True multidimensional arrays.
-* Arrays Summary:: Summary of arrays.
-@end menu
-
-@node Array Basics
-@section The Basics of Arrays
-
-This @value{SECTION} presents the basics: working with elements
-in arrays one at a time, and traversing all of the elements in
-an array.
-
-@menu
-* Array Intro:: Introduction to Arrays
-* Reference to Elements:: How to examine one element of an array.
-* Assigning Elements:: How to change an element of an array.
-* Array Example:: Basic Example of an Array
-* Scanning an Array:: A variation of the @code{for} statement. It
- loops through the indices of an array's
- existing elements.
-* Controlling Scanning:: Controlling the order in which arrays are
- scanned.
-@end menu
-
-@node Array Intro
-@subsection Introduction to Arrays
-
-@cindex Wall, Larry
-@quotation
-@i{Doing linear scans over an associative array is like trying to club someone
-to death with a loaded Uzi.}
-@author Larry Wall
-@end quotation
-
-The @command{awk} language provides one-dimensional arrays
-for storing groups of related strings or numbers.
-Every @command{awk} array must have a name. Array names have the same
-syntax as variable names; any valid variable name would also be a valid
-array name. But one name cannot be used in both ways (as an array and
-as a variable) in the same @command{awk} program.
-
-Arrays in @command{awk} superficially resemble arrays in other programming
-languages, but there are fundamental differences. In @command{awk}, it
-isn't necessary to specify the size of an array before starting to use it.
-Additionally, any number or string, not just consecutive integers,
-may be used as an array index.
-
-In most other languages, arrays must be @dfn{declared} before use,
-including a specification of
-how many elements or components they contain. In such languages, the
-declaration causes a contiguous block of memory to be allocated for that
-many elements. Usually, an index in the array must be a nonnegative integer.
-For example, the index zero specifies the first element in the array, which is
-actually stored at the beginning of the block of memory. Index one
-specifies the second element, which is stored in memory right after the
-first element, and so on. It is impossible to add more elements to the
-array, because it has room only for as many elements as given in
-the declaration.
-(Some languages allow arbitrary starting and ending
-indices---e.g., @samp{15 .. 27}---but the size of the array is still fixed when
-the array is declared.)
-
-@c 1/2015: Do not put the numeric values into @code. Array element
-@c values are no different than scalar variable values.
-A contiguous array of four elements might look like
-@ifnotdocbook
-@ref{figure-array-elements},
-@end ifnotdocbook
-@ifdocbook
-@inlineraw{docbook, <xref linkend="figure-array-elements"/>},
-@end ifdocbook
-conceptually, if the element values are eight, @code{"foo"},
-@code{""}, and 30.
-
-@ifnotdocbook
-@float Figure,figure-array-elements
-@caption{A contiguous array}
-@center @image{gawk_array-elements, , , A Contiguous Array}
-@end float
-@end ifnotdocbook
-
-@docbook
-<figure id="figure-array-elements" float="0">
-<title>A contiguous array</title>
-<mediaobject>
-<imageobject role="web"><imagedata fileref="array-elements.png"
format="PNG"/></imageobject>
-</mediaobject>
-</figure>
-@end docbook
-
-@noindent
-Only the values are stored; the indices are implicit from the order of
-the values. Here, eight is the value at index zero, because eight appears in
the
-position with zero elements before it.
-
-@cindex arrays @subentry indexing
-@cindex indexing arrays
-@cindex associative arrays
-@cindex arrays @subentry associative
-Arrays in @command{awk} are different---they are @dfn{associative}. This means
-that each array is a collection of pairs---an index and its corresponding
-array element value:
-
-@ifnotdocbook
-@c extra empty column to indent it right
-@multitable @columnfractions .1 .1 .1
-@headitem @tab Index @tab Value
-@item @tab @code{3} @tab @code{30}
-@item @tab @code{1} @tab @code{"foo"}
-@item @tab @code{0} @tab @code{8}
-@item @tab @code{2} @tab @code{""}
-@end multitable
-@end ifnotdocbook
-
-@docbook
-<informaltable>
-<tgroup cols="2">
-<colspec colname="1" align="left"/>
-<colspec colname="2" align="left"/>
-<thead>
-<row>
-<entry>Index</entry>
-<entry>Value</entry>
-</row>
-</thead>
-
-<tbody>
-<row>
-<entry><literal>3</literal></entry>
-<entry><literal>30</literal></entry>
-</row>
-
-<row>
-<entry><literal>1</literal></entry>
-<entry><literal>"foo"</literal></entry>
-</row>
-
-<row>
-<entry><literal>0</literal></entry>
-<entry><literal>8</literal></entry>
-</row>
-
-<row>
-<entry><literal>2</literal></entry>
-<entry><literal>""</literal></entry>
-</row>
-
-</tbody>
-</tgroup>
-</informaltable>
-
-@end docbook
-
-@noindent
-The pairs are shown in jumbled order because their order is
-irrelevant.@footnote{The ordering will vary among @command{awk}
-implementations, which typically use hash tables to store array elements
-and values.}
-
-One advantage of associative arrays is that new pairs can be added
-at any time. For example, suppose a tenth element is added to the array
-whose value is @w{@code{"number ten"}}. The result is:
-
-@ifnotdocbook
-@c extra empty column to indent it right
-@multitable @columnfractions .1 .1 .2
-@headitem @tab Index @tab Value
-@item @tab @code{10} @tab @code{"number ten"}
-@item @tab @code{3} @tab @code{30}
-@item @tab @code{1} @tab @code{"foo"}
-@item @tab @code{0} @tab @code{8}
-@item @tab @code{2} @tab @code{""}
-@end multitable
-@end ifnotdocbook
-
-@docbook
-<informaltable>
-<tgroup cols="2">
-<colspec colname="1" align="left"/>
-<colspec colname="2" align="left"/>
-<thead>
-<row>
-<entry>Index</entry>
-<entry>Value</entry>
-</row>
-</thead>
-<tbody>
-
-<row>
-<entry><literal>10</literal></entry>
-<entry><literal>"number ten"</literal></entry>
-</row>
-
-<row>
-<entry><literal>3</literal></entry>
-<entry><literal>30</literal></entry>
-</row>
-
-<row>
-<entry><literal>1</literal></entry>
-<entry><literal>"foo"</literal></entry>
-</row>
-
-<row>
-<entry><literal>0</literal></entry>
-<entry><literal>8</literal></entry>
-</row>
-
-<row>
-<entry><literal>2</literal></entry>
-<entry><literal>""</literal></entry>
-</row>
-
-</tbody>
-</tgroup>
-</informaltable>
-
-@end docbook
-
-@noindent
-@cindex sparse arrays
-@cindex arrays @subentry sparse
-Now the array is @dfn{sparse}, which just means some indices are missing.
-It has elements 0--3 and 10, but doesn't have elements 4, 5, 6, 7, 8, or 9.
-
-Another consequence of associative arrays is that the indices don't
-have to be nonnegative integers. Any number, or even a string, can be
-an index. For example, the following is an array that translates words from
-English to French:
-
-@ifnotdocbook
-@multitable @columnfractions .1 .1 .1
-@headitem @tab Index @tab Value
-@item @tab @code{"dog"} @tab @code{"chien"}
-@item @tab @code{"cat"} @tab @code{"chat"}
-@item @tab @code{"one"} @tab @code{"un"}
-@item @tab @code{1} @tab @code{"un"}
-@end multitable
-@end ifnotdocbook
-
-@docbook
-<informaltable>
-<tgroup cols="2">
-<colspec colname="1" align="left"/>
-<colspec colname="2" align="left"/>
-<thead>
-<row>
-<entry>Index</entry>
-<entry>Value</entry>
-</row>
-</thead>
-<tbody>
-<row>
-<entry><literal>"dog"</literal></entry>
-<entry><literal>"chien"</literal></entry>
-</row>
-
-<row>
-<entry><literal>"cat"</literal></entry>
-<entry><literal>"chat"</literal></entry>
-</row>
-
-<row>
-<entry><literal>"one"</literal></entry>
-<entry><literal>"un"</literal></entry>
-</row>
-
-<row>
-<entry><literal>1</literal></entry>
-<entry><literal>"un"</literal></entry>
-</row>
-
-</tbody>
-</tgroup>
-</informaltable>
-
-@end docbook
-
-@noindent
-Here we decided to translate the number one in both spelled-out and
-numeric form---thus illustrating that a single array can have both
-numbers and strings as indices.
-(In fact, array subscripts are always strings.
-There are some subtleties to how numbers work when used as
-array subscripts; this is discussed in more detail in
-@ref{Numeric Array Subscripts}.)
-Here, the number @code{1} isn't double-quoted, because @command{awk}
-automatically converts it to a string.
-
-@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
-@cindex case sensitivity @subentry array indices and
-@cindex arrays @subentry @code{IGNORECASE} variable and
-@cindex @code{IGNORECASE} variable @subentry array indices and
-The value of @code{IGNORECASE} has no effect upon array subscripting.
-The identical string value used to store an array element must be used
-to retrieve it.
-When @command{awk} creates an array (e.g., with the @code{split()}
-built-in function),
-that array's indices are consecutive integers starting at one.
-(@xref{String Functions}.)
-
-@command{awk}'s arrays are efficient---the time to access an element
-is independent of the number of elements in the array.
-
-@node Reference to Elements
-@subsection Referring to an Array Element
-@cindex arrays @subentry referencing elements
-@cindex array members
-@cindex elements in arrays
-
-The principal way to use an array is to refer to one of its elements.
-An @dfn{array reference} is an expression as follows:
-
-@example
-@var{array}[@var{index-expression}]
-@end example
-
-@noindent
-Here, @var{array} is the name of an array. The expression
@var{index-expression} is
-the index of the desired element of the array.
-
-@c 1/2015: Having the 4.3 in @samp is a little iffy. It's essentially
-@c an expression though, so leave be. It's to early in the discussion
-@c to mention that it's really a string.
-The value of the array reference is the current value of that array
-element. For example, @code{foo[4.3]} is an expression referencing the element
-of array @code{foo} at index @samp{4.3}.
-
-@cindex arrays @subentry unassigned elements
-@cindex unassigned array elements
-@cindex empty array elements
-A reference to an array element that has no recorded value yields a value of
-@code{""}, the null string. This includes elements
-that have not been assigned any value as well as elements that have been
-deleted (@pxref{Delete}).
-
-@cindex non-existent array elements
-@cindex arrays @subentry elements @subentry that don't exist
-@quotation NOTE
-A reference to an element that does not exist @emph{automatically} creates
-that array element, with the null string as its value. (In some cases,
-this is unfortunate, because it might waste memory inside @command{awk}.)
-
-Novice @command{awk} programmers often make the mistake of checking if
-an element exists by checking if the value is empty:
-
-@example
-# Check if "foo" exists in a: @ii{Incorrect!}
-if (a["foo"] != "") @dots{}
-@end example
-
-@noindent
-This is incorrect for two reasons. First, it @emph{creates} @code{a["foo"]}
-if it didn't exist before! Second, it is valid (if a bit unusual) to set
-an array element equal to the empty string.
-@end quotation
-
-@c @cindex arrays, @code{in} operator and
-@cindex @code{in} operator @subentry testing if array element exists
-To determine whether an element exists in an array at a certain index, use
-the following expression:
-
-@example
-@var{indx} in @var{array}
-@end example
-
-@cindex side effects @subentry array indexing
-@noindent
-This expression tests whether the particular index @var{indx} exists,
-without the side effect of creating that element if it is not present.
-The expression has the value one (true) if @code{@var{array}[@var{indx}]}
-exists and zero (false) if it does not exist.
-(We use @var{indx} here, because @samp{index} is the name of a built-in
-function.)
-For example, this statement tests whether the array @code{frequencies}
-contains the index @samp{2}:
-
-@example
-@group
-if (2 in frequencies)
- print "Subscript 2 is present."
-@end group
-@end example
-
-Note that this is @emph{not} a test of whether the array
-@code{frequencies} contains an element whose @emph{value} is two.
-There is no way to do that except to scan all the elements. Also, this
-@emph{does not} create @code{frequencies[2]}, while the following
-(incorrect) alternative does:
-
-@example
-@group
-if (frequencies[2] != "")
- print "Subscript 2 is present."
-@end group
-@end example
-
-@node Assigning Elements
-@subsection Assigning Array Elements
-@cindex arrays @subentry elements @subentry assigning values
-@cindex elements in arrays @subentry assigning values
-
-Array elements can be assigned values just like
-@command{awk} variables:
-
-@example
-@var{array}[@var{index-expression}] = @var{value}
-@end example
-
-@noindent
-@var{array} is the name of an array. The expression
-@var{index-expression} is the index of the element of the array that is
-assigned a value. The expression @var{value} is the value to
-assign to that element of the array.
-
-@node Array Example
-@subsection Basic Array Example
-@cindex arrays @subentry example of using
-
-The following program takes a list of lines, each beginning with a line
-number, and prints them out in order of line number. The line numbers
-are not in order when they are first read---instead, they
-are scrambled. This program sorts the lines by making an array using
-the line numbers as subscripts. The program then prints out the lines
-in sorted order of their numbers. It is a very simple program and gets
-confused upon encountering repeated numbers, gaps, or lines that don't
-begin with a number:
-
-@example
-@c file eg/misc/arrayorder.awk
-@{
- if ($1 > max)
- max = $1
- arr[$1] = $0
-@}
-
-END @{
- for (x = 1; x <= max; x++)
- print arr[x]
-@}
-@c endfile
-@end example
-
-The first rule keeps track of the largest line number seen so far;
-it also stores each line into the array @code{arr}, at an index that
-is the line's number.
-The second rule runs after all the input has been read, to print out
-all the lines.
-When this program is run with the following input:
-
-@example
-@group
-@c file eg/misc/arrayorder.data
-5 I am the Five man
-2 Who are you? The new number two!
-4 . . . And four on the floor
-1 Who is number one?
-3 I three you.
-@c endfile
-@end group
-@end example
-
-@noindent
-Its output is:
-
-@example
-@group
-1 Who is number one?
-2 Who are you? The new number two!
-3 I three you.
-4 . . . And four on the floor
-5 I am the Five man
-@end group
-@end example
-
-If a line number is repeated, the last line with a given number overrides
-the others.
-Gaps in the line numbers can be handled with an easy improvement to the
-program's @code{END} rule, as follows:
-
-@example
-@group
-END @{
- for (x = 1; x <= max; x++)
- if (x in arr)
- print arr[x]
-@}
-@end group
-@end example
-
-As mentioned, the program is simplistic. It can be easily
-confused; for example, by using negative or nonalphabetic line numbers.
-The point here is merely to demonstrate basic array usage.
-
-@node Scanning an Array
-@subsection Scanning All Elements of an Array
-@cindex elements in arrays @subentry scanning
-@cindex scanning arrays
-@cindex arrays @subentry scanning
-@cindex loops @subentry @code{for} @subentry array scanning
-
-In programs that use arrays, it is often necessary to use a loop that
-executes once for each element of an array. In other languages, where
-arrays are contiguous and indices are limited to nonnegative integers,
-this is easy: all the valid indices can be found by counting from
-the lowest index up to the highest. This technique won't do the job
-in @command{awk}, because any number or string can be an array index.
-So @command{awk} has a special kind of @code{for} statement for scanning
-an array:
-
-@example
-@group
-for (@var{var} in @var{array})
- @var{body}
-@end group
-@end example
-
-@noindent
-@cindex @code{in} operator @subentry use in loops
-This loop executes @var{body} once for each index in @var{array} that the
-program has previously used, with the variable @var{var} set to that index.
-
-@cindex arrays @subentry @code{for} statement and
-@cindex @code{for} statement @subentry looping over arrays
-The following program uses this form of the @code{for} statement. The
-first rule scans the input records and notes which words appear (at
-least once) in the input, by storing a one into the array @code{used} with
-the word as the index. The second rule scans the elements of @code{used} to
-find all the distinct words that appear in the input. It prints each
-word that is more than 10 characters long and also prints the number of
-such words.
-@xref{String Functions}
-for more information on the built-in function @code{length()}.
-
-@example
-@group
-# Record a 1 for each word that is used at least once
-@{
- for (i = 1; i <= NF; i++)
- used[$i] = 1
-@}
-@end group
-
-@group
-# Find number of distinct words more than 10 characters long
-END @{
- for (x in used) @{
- if (length(x) > 10) @{
- ++num_long_words
- print x
- @}
- @}
- print num_long_words, "words longer than 10 characters"
-@}
-@end group
-@end example
-
-@noindent
-@xref{Word Sorting}
-for a more detailed example of this type.
-
-@cindex arrays @subentry elements @subentry order of access by @code{in}
operator
-@cindex elements in arrays @subentry order of access by @code{in} operator
-@cindex @code{in} operator @subentry order of array access
-The order in which elements of the array are accessed by this statement
-is determined by the internal arrangement of the array elements within
-@command{awk} and in standard @command{awk} cannot be controlled
-or changed. This can lead to problems if new elements are added to
-@var{array} by statements in the loop body; it is not predictable whether
-the @code{for} loop will reach them. Similarly, changing @var{var} inside
-the loop may produce strange results. It is best to avoid such things.
-
-As a point of information, @command{gawk} sets up the list of elements
-to be iterated over before the loop starts, and does not change it.
-But not all @command{awk} versions do so. Consider this program, named
-@file{loopcheck.awk}:
-
-@example
-BEGIN @{
- a["here"] = "here"
- a["is"] = "is"
- a["a"] = "a"
- a["loop"] = "loop"
- for (i in a) @{
- j++
- a[j] = j
- print i
- @}
-@}
-@end example
-
-Here is what happens when run with @command{gawk} (and @command{mawk}):
-
-@example
-$ @kbd{gawk -f loopcheck.awk}
-@print{} here
-@print{} loop
-@print{} a
-@print{} is
-@end example
-
-Contrast this to BWK @command{awk}:
-
-@example
-$ @kbd{nawk -f loopcheck.awk}
-@print{} loop
-@print{} here
-@print{} is
-@print{} a
-@print{} 1
-@end example
-
-@node Controlling Scanning
-@subsection Using Predefined Array Scanning Orders with @command{gawk}
-
-This @value{SUBSECTION} describes a feature that is specific to @command{gawk}.
-
-By default, when a @code{for} loop traverses an array, the order
-is undefined, meaning that the @command{awk} implementation
-determines the order in which the array is traversed.
-This order is usually based on the internal implementation of arrays
-and will vary from one version of @command{awk} to the next.
-
-@cindex array scanning order, controlling
-@cindex controlling array scanning order
-Often, though, you may wish to do something simple, such as
-``traverse the array by comparing the indices in ascending order,''
-or ``traverse the array by comparing the values in descending order.''
-@command{gawk} provides two mechanisms that give you this control:
-
-@itemize @value{BULLET}
-@item
-Set @code{PROCINFO["sorted_in"]} to one of a set of predefined values.
-We describe this now.
-
-@item
-Set @code{PROCINFO["sorted_in"]} to the name of a user-defined function
-to use for comparison of array elements. This advanced feature
-is described later in @ref{Array Sorting}.
-@end itemize
-
-@cindex @code{PROCINFO} array @subentry values of @code{sorted_in}
-The following special values for @code{PROCINFO["sorted_in"]} are available:
-
-@table @code
-@item "@@unsorted"
-Array elements are processed in arbitrary order, which is the default
-@command{awk} behavior.
-
-@item "@@ind_str_asc"
-Order by indices in ascending order compared as strings; this is the most
basic sort.
-(Internally, array indices are always strings, so with @samp{a[2*5] = 1}
-the index is @code{"10"} rather than numeric 10.)
-
-@item "@@ind_num_asc"
-Order by indices in ascending order but force them to be treated as numbers in
the process.
-Any index with a non-numeric value will end up positioned as if it were zero.
-
-@item "@@val_type_asc"
-Order by element values in ascending order (rather than by indices).
-Ordering is by the type assigned to the element
-(@pxref{Typing and Comparison}).
-All numeric values come before all string values,
-which in turn come before all subarrays.
-(Subarrays have not been described yet;
-@pxref{Arrays of Arrays}.)
-
-If you choose to use this feature in traversing @code{FUNCTAB}
-(@pxref{Auto-set}), then the order is built-in functions first
-(@pxref{Built-in}), then user-defined functions (@pxref{User-defined})
-next, and finally functions loaded from an extension
-(@pxref{Dynamic Extensions}).
-
-@item "@@val_str_asc"
-Order by element values in ascending order (rather than by indices). Scalar
values are
-compared as strings.
-If the string values are identical,
-the index string values are compared instead.
-When comparing non-scalar values,
-@code{"@@val_type_asc"} sort ordering is used, so subarrays, if present,
-come out last.
-
-@item "@@val_num_asc"
-Order by element values in ascending order (rather than by indices). Scalar
values are
-compared as numbers.
-Non-scalar values are compared using @code{"@@val_type_asc"} sort ordering,
-so subarrays, if present, come out last.
-When numeric values are equal, the string values are used to provide
-an ordering: this guarantees consistent results across different
-versions of the C @code{qsort()} function,@footnote{When two elements
-compare as equal, the C @code{qsort()} function does not guarantee
-that they will maintain their original relative order after sorting.
-Using the string value to provide a unique ordering when the numeric
-values are equal ensures that @command{gawk} behaves consistently
-across different environments.} which @command{gawk} uses internally
-to perform the sorting.
-If the string values are also identical,
-the index string values are compared instead.
-
-
-@item "@@ind_str_desc"
-Like @code{"@@ind_str_asc"}, but the
-string indices are ordered from high to low.
-
-@item "@@ind_num_desc"
-Like @code{"@@ind_num_asc"}, but the
-numeric indices are ordered from high to low.
-
-@item "@@val_type_desc"
-Like @code{"@@val_type_asc"}, but the
-element values, based on type, are ordered from high to low.
-Subarrays, if present, come out first.
-
-@item "@@val_str_desc"
-Like @code{"@@val_str_asc"}, but the
-element values, treated as strings, are ordered from high to low.
-If the string values are identical,
-the index string values are compared instead.
-When comparing non-scalar values,
-@code{"@@val_type_desc"} sort ordering is used, so subarrays, if present,
-come out first.
-
-@item "@@val_num_desc"
-Like @code{"@@val_num_asc"}, but the
-element values, treated as numbers, are ordered from high to low.
-If the numeric values are equal, the string values are compared instead.
-If they are also identical, the index string values are compared instead.
-Non-scalar values are compared using @code{"@@val_type_desc"} sort ordering,
-so subarrays, if present, come out first.
-@end table
-
-The array traversal order is determined before the @code{for} loop
-starts to run. Changing @code{PROCINFO["sorted_in"]} in the loop body
-does not affect the loop.
-For example:
-
-@example
-$ @kbd{gawk '}
-> @kbd{BEGIN @{}
-> @kbd{ a[4] = 4}
-> @kbd{ a[3] = 3}
-> @kbd{ for (i in a)}
-> @kbd{ print i, a[i]}
-> @kbd{@}'}
-@print{} 4 4
-@print{} 3 3
-$ @kbd{gawk '}
-> @kbd{BEGIN @{}
-> @kbd{ PROCINFO["sorted_in"] = "@@ind_str_asc"}
-> @kbd{ a[4] = 4}
-> @kbd{ a[3] = 3}
-> @kbd{ for (i in a)}
-> @kbd{ print i, a[i]}
-> @kbd{@}'}
-@print{} 3 3
-@print{} 4 4
-@end example
-
-When sorting an array by element values, if a value happens to be
-a subarray then it is considered to be greater than any string or
-numeric value, regardless of what the subarray itself contains,
-and all subarrays are treated as being equal to each other. Their
-order relative to each other is determined by their index strings.
-
-Here are some additional things to bear in mind about sorted
-array traversal:
-
-@itemize @value{BULLET}
-@item
-The value of @code{PROCINFO["sorted_in"]} is global. That is, it affects
-all array traversal @code{for} loops. If you need to change it within your
-own code, you should see if it's defined and save and restore the value:
-
-@example
-@dots{}
-if ("sorted_in" in PROCINFO)
- save_sorted = PROCINFO["sorted_in"]
-
-PROCINFO["sorted_in"] = "@@val_str_desc" # or whatever
-@dots{}
-if (save_sorted)
- PROCINFO["sorted_in"] = save_sorted
-@end example
-
-@item
-As already mentioned, the default array traversal order is represented by
-@code{"@@unsorted"}. You can also get the default behavior by assigning
-the null string to @code{PROCINFO["sorted_in"]} or by just deleting the
-@code{"sorted_in"} element from the @code{PROCINFO} array with
-the @code{delete} statement.
-(The @code{delete} statement hasn't been described yet; @pxref{Delete}.)
-@end itemize
-
-In addition, @command{gawk} provides built-in functions for
-sorting arrays; see @ref{Array Sorting Functions}.
-
-@node Numeric Array Subscripts
-@section Using Numbers to Subscript Arrays
-
-@cindex numbers @subentry as array subscripts
-@cindex array subscripts @subentry numbers as
-@cindex arrays @subentry numeric subscripts
-@cindex subscripts in arrays @subentry numbers as
-@cindex @code{CONVFMT} variable @subentry array subscripts and
-An important aspect to remember about arrays is that @emph{array subscripts
-are always strings}. When a numeric value is used as a subscript,
-it is converted to a string value before being used for subscripting
-(@pxref{Conversion}).
-This means that the value of the predefined variable @code{CONVFMT} can
-affect how your program accesses elements of an array. For example:
-
-@example
-xyz = 12.153
-data[xyz] = 1
-CONVFMT = "%2.2f"
-if (xyz in data)
- printf "%s is in data\n", xyz
-else
- printf "%s is not in data\n", xyz
-@end example
-
-@noindent
-This prints @samp{12.15 is not in data}. The first statement gives
-@code{xyz} a numeric value. Assigning to
-@code{data[xyz]} subscripts @code{data} with the string value @code{"12.153"}
-(using the default conversion value of @code{CONVFMT}, @code{"%.6g"}).
-Thus, the array element @code{data["12.153"]} is assigned the value one.
-The program then changes
-the value of @code{CONVFMT}. The test @samp{(xyz in data)} generates a new
-string value from @code{xyz}---this time @code{"12.15"}---because the value of
-@code{CONVFMT} only allows two significant digits. This test fails,
-because @code{"12.15"} is different from @code{"12.153"}.
-
-@cindex converting @subentry integer array subscripts to strings
-@cindex integer array indices
-According to the rules for conversions
-(@pxref{Conversion}), integer
-values always convert to strings as integers, no matter what the
-value of @code{CONVFMT} may happen to be. So the usual case of
-the following works:
-
-@example
-for (i = 1; i <= maxsub; i++)
- @ii{do something with} array[i]
-@end example
-
-The ``integer values always convert to strings as integers'' rule
-has an additional consequence for array indexing.
-Octal and hexadecimal constants
-@ifnotdocbook
-(@pxref{Nondecimal-numbers})
-@end ifnotdocbook
-@ifdocbook
-(covered in @ref{Nondecimal-numbers})
-@end ifdocbook
-are converted internally into numbers, and their original form
-is forgotten. This means, for example, that @code{array[17]},
-@code{array[021]}, and @code{array[0x11]} all refer to the same element!
-
-As with many things in @command{awk}, the majority of the time
-things work as you would expect them to. But it is useful to have a precise
-knowledge of the actual rules, as they can sometimes have a subtle
-effect on your programs.
-
-@node Uninitialized Subscripts
-@section Using Uninitialized Variables as Subscripts
-
-@cindex variables @subentry uninitialized, as array subscripts
-@cindex uninitialized variables, as array subscripts
-@cindex subscripts in arrays @subentry uninitialized variables as
-@cindex arrays @subentry subscripts, uninitialized variables as
-Suppose it's necessary to write a program
-to print the input data in reverse order.
-A reasonable attempt to do so (with some test
-data) might look like this:
-
-@example
-$ @kbd{echo 'line 1}
-> @kbd{line 2}
-> @kbd{line 3' | awk '@{ l[lines] = $0; ++lines @}}
-> @kbd{END @{}
-> @kbd{for (i = lines - 1; i >= 0; i--)}
-> @kbd{print l[i]}
-> @kbd{@}'}
-@print{} line 3
-@print{} line 2
-@end example
-
-Unfortunately, the very first line of input data did not appear in the
-output!
-
-Upon first glance, we would think that this program should have worked.
-The variable @code{lines}
-is uninitialized, and uninitialized variables have the numeric value zero.
-So, @command{awk} should have printed the value of @code{l[0]}.
-
-The issue here is that subscripts for @command{awk} arrays are @emph{always}
-strings. Uninitialized variables, when used as strings, have the
-value @code{""}, not zero. Thus, @samp{line 1} ends up stored in
-@code{l[""]}.
-The following version of the program works correctly:
-
-@example
-@{ l[lines++] = $0 @}
-END @{
- for (i = lines - 1; i >= 0; i--)
- print l[i]
-@}
-@end example
-
-Here, the @samp{++} forces @code{lines} to be numeric, thus making
-the ``old value'' numeric zero. This is then converted to @code{"0"}
-as the array subscript.
-
-@cindex array subscripts @subentry null string as
-@cindex null strings @subentry as array subscripts
-@cindex dark corner @subentry array subscripts
-@cindex lint checking @subentry array subscripts
-Even though it is somewhat unusual, the null string
-(@code{""}) is a valid array subscript.
-@value{DARKCORNER}
-@command{gawk} warns about the use of the null string as a subscript
-if @option{--lint} is provided
-on the command line (@pxref{Options}).
-
-@node Delete
-@section The @code{delete} Statement
-@cindex @code{delete} statement
-@cindex deleting @subentry elements in arrays
-@cindex arrays @subentry elements @subentry deleting
-@cindex elements in arrays @subentry deleting
-
-To remove an individual element of an array, use the @code{delete}
-statement:
-
-@example
-delete @var{array}[@var{index-expression}]
-@end example
-
-Once an array element has been deleted, any value the element once
-had is no longer available. It is as if the element had never
-been referred to or been given a value.
-The following is an example of deleting elements in an array:
-
-@example
-for (i in frequencies)
- delete frequencies[i]
-@end example
-
-@noindent
-This example removes all the elements from the array @code{frequencies}.
-Once an element is deleted, a subsequent @code{for} statement to scan the array
-does not report that element and using the @code{in} operator to check for
-the presence of that element returns zero (i.e., false):
-
-@example
-delete foo[4]
-if (4 in foo)
- print "This will never be printed"
-@end example
-
-@cindex null strings @subentry deleting array elements and
-It is important to note that deleting an element is @emph{not} the
-same as assigning it a null value (the empty string, @code{""}).
-For example:
-
-@example
-@group
-foo[4] = ""
-if (4 in foo)
- print "This is printed, even though foo[4] is empty"
-@end group
-@end example
-
-@cindex lint checking @subentry array subscripts
-It is not an error to delete an element that does not exist.
-However, if @option{--lint} is provided on the command line
-(@pxref{Options}),
-@command{gawk} issues a warning message when an element that
-is not in the array is deleted.
-
-@cindex common extensions @subentry @code{delete} to delete entire arrays
-@cindex extensions @subentry common @subentry @code{delete} to delete entire
arrays
-@cindex arrays @subentry deleting entire contents
-@cindex deleting @subentry entire arrays
-@cindex @code{delete} @var{array}
-@cindex differences in @command{awk} and @command{gawk} @subentry array
elements, deleting
-All the elements of an array may be deleted with a single statement
-by leaving off the subscript in the @code{delete} statement,
-as follows:
-
-
-@example
-delete @var{array}
-@end example
-
-Using this version of the @code{delete} statement is about three times
-more efficient than the equivalent loop that deletes each element one
-at a time.
-
-This form of the @code{delete} statement is also supported
-by BWK @command{awk} and @command{mawk}, as well as
-by a number of other implementations.
-
-@cindex Brian Kernighan's @command{awk}
-@quotation NOTE
-For many years, using @code{delete} without a subscript was a common
-extension. In September 2012, it was accepted for inclusion into the
-POSIX standard. See @uref{http://austingroupbugs.net/view.php?id=544,
-the Austin Group website}.
-@end quotation
-
-@cindex portability @subentry deleting array elements
-@cindex Brennan, Michael
-The following statement provides a portable but nonobvious way to clear
-out an array:@footnote{Thanks to Michael Brennan for pointing this out.}
-
-@example
-split("", array)
-@end example
-
-@cindex @code{split()} function @subentry array elements, deleting
-The @code{split()} function
-(@pxref{String Functions})
-clears out the target array first. This call asks it to split
-apart the null string. Because there is no data to split out, the
-function simply clears the array and then returns.
-
-@quotation CAUTION
-Deleting all the elements from an array does not change its type; you cannot
-clear an array and then use the array's name as a scalar
-(i.e., a regular variable). For example, the following does not work:
-
-@example
-a[1] = 3
-delete a
-a = 3
-@end example
-@end quotation
-
-@node Multidimensional
-@section Multidimensional Arrays
-
-@menu
-* Multiscanning:: Scanning multidimensional arrays.
-@end menu
-
-@cindex subscripts in arrays @subentry multidimensional
-@cindex arrays @subentry multidimensional
-A @dfn{multidimensional array} is an array in which an element is identified
-by a sequence of indices instead of a single index. For example, a
-two-dimensional array requires two indices. The usual way (in many
-languages, including @command{awk}) to refer to an element of a
-two-dimensional array named @code{grid} is with
-@code{grid[@var{x},@var{y}]}.
-
-@cindex @code{SUBSEP} variable @subentry multidimensional arrays and
-Multidimensional arrays are supported in @command{awk} through
-concatenation of indices into one string.
-@command{awk} converts the indices into strings
-(@pxref{Conversion}) and
-concatenates them together, with a separator between them. This creates
-a single string that describes the values of the separate indices. The
-combined string is used as a single index into an ordinary,
-one-dimensional array. The separator used is the value of the built-in
-variable @code{SUBSEP}.
-
-For example, suppose we evaluate the expression @samp{foo[5,12] = "value"}
-when the value of @code{SUBSEP} is @code{"@@"}. The numbers 5 and 12 are
-converted to strings and
-concatenated with an @samp{@@} between them, yielding @code{"5@@12"}; thus,
-the array element @code{foo["5@@12"]} is set to @code{"value"}.
-
-Once the element's value is stored, @command{awk} has no record of whether
-it was stored with a single index or a sequence of indices. The two
-expressions @samp{foo[5,12]} and @w{@samp{foo[5 SUBSEP 12]}} are always
-equivalent.
-
-The default value of @code{SUBSEP} is the string @code{"\034"},
-which contains a nonprinting character that is unlikely to appear in an
-@command{awk} program or in most input data.
-The usefulness of choosing an unlikely character comes from the fact
-that index values that contain a string matching @code{SUBSEP} can lead to
-combined strings that are ambiguous. Suppose that @code{SUBSEP} is
-@code{"@@"}; then @w{@samp{foo["a@@b", "c"]}} and @w{@samp{foo["a",
-"b@@c"]}} are indistinguishable because both are actually
-stored as @samp{foo["a@@b@@c"]}.
-
-@cindex @code{in} operator @subentry index existence in multidimensional arrays
-To test whether a particular index sequence exists in a
-multidimensional array, use the same operator (@code{in}) that is
-used for single-dimensional arrays. Write the whole sequence of indices
-in parentheses, separated by commas, as the left operand:
-
-@example
-if ((@var{subscript1}, @var{subscript2}, @dots{}) in @var{array})
- @dots{}
-@end example
-
-Here is an example that treats its input as a two-dimensional array of
-fields; it rotates this array 90 degrees clockwise and prints the
-result. It assumes that all lines have the same number of
-elements:
-
-@example
-@{
- if (max_nf < NF)
- max_nf = NF
- max_nr = NR
- for (x = 1; x <= NF; x++)
- vector[x, NR] = $x
-@}
-
-END @{
- for (x = 1; x <= max_nf; x++) @{
- for (y = max_nr; y >= 1; --y)
- printf("%s ", vector[x, y])
- printf("\n")
- @}
-@}
-@end example
-
-@noindent
-When given the input:
-
-@example
-@group
-1 2 3 4 5 6
-2 3 4 5 6 1
-3 4 5 6 1 2
-4 5 6 1 2 3
-@end group
-@end example
-
-@noindent
-the program produces the following output:
-
-@example
-@group
-4 3 2 1
-5 4 3 2
-6 5 4 3
-1 6 5 4
-2 1 6 5
-3 2 1 6
-@end group
-@end example
-
-@node Multiscanning
-@subsection Scanning Multidimensional Arrays
-
-There is no special @code{for} statement for scanning a
-``multidimensional'' array. There cannot be one, because, in truth,
-@command{awk} does not have
-multidimensional arrays or elements---there is only a
-multidimensional @emph{way of accessing} an array.
-
-@cindex subscripts in arrays @subentry multidimensional @subentry scanning
-@cindex arrays @subentry multidimensional @subentry scanning
-@cindex scanning multidimensional arrays
-However, if your program has an array that is always accessed as
-multidimensional, you can get the effect of scanning it by combining
-the scanning @code{for} statement
-(@pxref{Scanning an Array}) with the
-built-in @code{split()} function
-(@pxref{String Functions}).
-It works in the following manner:
-
-@example
-for (combined in array) @{
- split(combined, separate, SUBSEP)
- @dots{}
-@}
-@end example
-
-@noindent
-This sets the variable @code{combined} to
-each concatenated combined index in the array, and splits it
-into the individual indices by breaking it apart where the value of
-@code{SUBSEP} appears. The individual indices then become the elements of
-the array @code{separate}.
-
-Thus, if a value is previously stored in @code{array[1, "foo"]}, then
-an element with index @code{"1\034foo"} exists in @code{array}. (Recall
-that the default value of @code{SUBSEP} is the character with code 034.)
-Sooner or later, the @code{for} statement finds that index and does an
-iteration with the variable @code{combined} set to @code{"1\034foo"}.
-Then the @code{split()} function is called as follows:
-
-@example
-split("1\034foo", separate, "\034")
-@end example
-
-@noindent
-The result is to set @code{separate[1]} to @code{"1"} and
-@code{separate[2]} to @code{"foo"}. Presto! The original sequence of
-separate indices is recovered.
-
-
-@node Arrays of Arrays
-@section Arrays of Arrays
-@cindex arrays @subentry arrays of arrays
-
-@command{gawk} goes beyond standard @command{awk}'s multidimensional
-array access and provides true arrays of
-arrays. Elements of a subarray are referred to by their own indices
-enclosed in square brackets, just like the elements of the main array.
-For example, the following creates a two-element subarray at index @code{1}
-of the main array @code{a}:
-
-@example
-a[1][1] = 1
-a[1][2] = 2
-@end example
-
-This simulates a true two-dimensional array. Each subarray element can
-contain another subarray as a value, which in turn can hold other arrays
-as well. In this way, you can create arrays of three or more dimensions.
-The indices can be any @command{awk} expressions, including scalars
-separated by commas (i.e., a regular @command{awk} simulated
-multidimensional subscript). So the following is valid in
-@command{gawk}:
-
-@example
-a[1][3][1, "name"] = "barney"
-@end example
-
-Each subarray and the main array can be of different length. In fact, the
-elements of an array or its subarray do not all have to have the same
-type. This means that the main array and any of its subarrays can be
-nonrectangular, or jagged in structure. You can assign a scalar value to
-the index @code{4} of the main array @code{a}, even though @code{a[1]}
-is itself an array and not a scalar:
-
-@example
-a[4] = "An element in a jagged array"
-@end example
-
-The terms @dfn{dimension}, @dfn{row}, and @dfn{column} are
-meaningless when applied
-to such an array, but we will use ``dimension'' henceforth to imply the
-maximum number of indices needed to refer to an existing element. The
-type of any element that has already been assigned cannot be changed
-by assigning a value of a different type. You have to first delete the
-current element, which effectively makes @command{gawk} forget about
-the element at that index:
-
-@example
-delete a[4]
-a[4][5][6][7] = "An element in a four-dimensional array"
-@end example
-
-@noindent
-This removes the scalar value from index @code{4} and then inserts a
-three-level nested subarray
-containing a scalar. You can also
-delete an entire subarray or subarray of subarrays:
-
-@example
-delete a[4][5]
-a[4][5] = "An element in subarray a[4]"
-@end example
-
-But recall that you can not delete the main array @code{a} and then use it
-as a scalar.
-
-The built-in functions that take array arguments can also be used
-with subarrays. For example, the following code fragment uses @code{length()}
-(@pxref{String Functions})
-to determine the number of elements in the main array @code{a} and
-its subarrays:
-
-@example
-print length(a), length(a[1]), length(a[1][3])
-@end example
-
-@noindent
-This results in the following output for our main array @code{a}:
-
-@example
-2, 3, 1
-@end example
-
-@noindent
-The @samp{@var{subscript} in @var{array}} expression
-(@pxref{Reference to Elements}) works similarly for both
-regular @command{awk}-style
-arrays and arrays of arrays. For example, the tests @samp{1 in a},
-@samp{3 in a[1]}, and @samp{(1, "name") in a[1][3]} all evaluate to
-one (true) for our array @code{a}.
-
-The @samp{for (item in array)} statement (@pxref{Scanning an Array})
-can be nested to scan all the
-elements of an array of arrays if it is rectangular in structure. In order
-to print the contents (scalar values) of a two-dimensional array of arrays
-(i.e., in which each first-level element is itself an
-array, not necessarily of the same length),
-you could use the following code:
-
-@example
-for (i in array)
- for (j in array[i])
- print array[i][j]
-@end example
-
-The @code{isarray()} function (@pxref{Type Functions})
-lets you test if an array element is itself an array:
-
-@example
-for (i in array) @{
- if (isarray(array[i])) @{
- for (j in array[i]) @{
- print array[i][j]
- @}
- @}
- else
- print array[i]
-@}
-@end example
-
-If the structure of a jagged array of arrays is known in advance,
-you can often devise workarounds using control statements. For example,
-the following code prints the elements of our main array @code{a}:
-
-@example
-@group
-for (i in a) @{
- for (j in a[i]) @{
- if (j == 3) @{
- for (k in a[i][j])
- print a[i][j][k]
-@end group
-@group
- @} else
- print a[i][j]
- @}
-@}
-@end group
-@end example
-
-@noindent
-@xref{Walking Arrays} for a user-defined function that ``walks'' an
-arbitrarily dimensioned array of arrays.
-
-Recall that a reference to an uninitialized array element yields a value
-of @code{""}, the null string. This has one important implication when you
-intend to use a subarray as an argument to a function, as illustrated by
-the following example:
-
-@example
-$ @kbd{gawk 'BEGIN @{ split("a b c d", b[1]); print b[1][1] @}'}
-@error{} gawk: cmd. line:1: fatal: split: second argument is not an array
-@end example
-
-The way to work around this is to first force @code{b[1]} to be an array by
-creating an arbitrary index:
-
-@example
-$ @kbd{gawk 'BEGIN @{ b[1][1] = ""; split("a b c d", b[1]); print b[1][1] @}'}
-@print{} a
-@end example
-
-@node Arrays Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Standard @command{awk} provides one-dimensional associative arrays
-(arrays indexed by string values). All arrays are associative; numeric
-indices are converted automatically to strings.
-
-@item
-Array elements are referenced as @code{@var{array}[@var{indx}]}.
-Referencing an element creates it if it did not exist previously.
-
-@item
-The proper way to see if an array has an element with a given index
-is to use the @code{in} operator: @samp{@var{indx} in @var{array}}.
-
-@item
-Use @samp{for (@var{indx} in @var{array}) @dots{}} to scan through all the
-individual elements of an array. In the body of the loop, @var{indx} takes
-on the value of each element's index in turn.
-
-@item
-The order in which a @samp{for (@var{indx} in @var{array})} loop
-traverses an array is undefined in POSIX @command{awk} and varies among
-implementations. @command{gawk} lets you control the order by assigning
-special predefined values to @code{PROCINFO["sorted_in"]}.
-
-@item
-Use @samp{delete @var{array}[@var{indx}]} to delete an individual element.
-To delete all of the elements in an array,
-use @samp{delete @var{array}}.
-This latter feature has been a common extension for many
-years and is now standard, but may not be supported by all commercial
-versions of @command{awk}.
-
-@item
-Standard @command{awk} simulates multidimensional arrays by separating
-subscript values with commas. The values are concatenated into a
-single string, separated by the value of @code{SUBSEP}. The fact
-that such a subscript was created in this way is not retained; thus,
-changing @code{SUBSEP} may have unexpected consequences. You can use
-@samp{(@var{sub1}, @var{sub2}, @dots{}) in @var{array}} to see if such
-a multidimensional subscript exists in @var{array}.
-
-@item
-@command{gawk} provides true arrays of arrays. You use a separate
-set of square brackets for each dimension in such an array:
-@code{data[row][col]}, for example. Array elements may thus be either
-scalar values (number or string) or other arrays.
-
-@item
-Use the @code{isarray()} built-in function to determine if an array
-element is itself a subarray.
-
-@end itemize
-
-
-@node Functions
-@chapter Functions
-
-@cindex functions @subentry built-in
-@cindex built-in functions
-This @value{CHAPTER} describes @command{awk}'s built-in functions,
-which fall into three categories: numeric, string, and I/O.
-@command{gawk} provides additional groups of functions
-to work with values that represent time, do
-bit manipulation, sort arrays,
-provide type information, and internationalize and localize programs.
-
-Besides the built-in functions, @command{awk} has provisions for
-writing new functions that the rest of a program can use.
-The second half of this @value{CHAPTER} describes these
-@dfn{user-defined} functions.
-Finally, we explore indirect function calls, a @command{gawk}-specific
-extension that lets you determine at runtime what function is to
-be called.
-
-@menu
-* Built-in:: Summarizes the built-in functions.
-* User-defined:: Describes User-defined functions in detail.
-* Indirect Calls:: Choosing the function to call at runtime.
-* Functions Summary:: Summary of functions.
-@end menu
-
-@node Built-in
-@section Built-in Functions
-
-@dfn{Built-in} functions are always available for your @command{awk}
-program to call. This @value{SECTION} defines all the built-in functions
-in @command{awk}; some of these are mentioned in other @value{SECTION}s
-but are summarized here for your convenience.
-
-@menu
-* Calling Built-in:: How to call built-in functions.
-* Boolean Functions:: A function that returns Boolean values.
-* Numeric Functions:: Functions that work with numbers, including
- @code{int()}, @code{sin()} and @code{rand()}.
-* String Functions:: Functions for string manipulation, such as
- @code{split()}, @code{match()} and
- @code{sprintf()}.
-* I/O Functions:: Functions for files and shell commands.
-* Time Functions:: Functions for dealing with timestamps.
-* Bitwise Functions:: Functions for bitwise operations.
-* Type Functions:: Functions for type information.
-* I18N Functions:: Functions for string translation.
-@end menu
-
-@node Calling Built-in
-@subsection Calling Built-in Functions
-
-To call one of @command{awk}'s built-in functions, write the name of
-the function followed
-by arguments in parentheses. For example, @samp{atan2(y + z, 1)}
-is a call to the function @code{atan2()} and has two arguments.
-
-@cindex programming conventions @subentry functions @subentry calling
-@cindex whitespace @subentry functions, calling
-Whitespace is ignored between the built-in function name and the
-opening parenthesis, but nonetheless it is good practice to avoid using
whitespace
-there. User-defined functions do not permit whitespace in this way, and
-it is easier to avoid mistakes by following a simple
-convention that always works---no whitespace after a function name.
-
-@cindex troubleshooting @subentry @command{gawk} @subentry fatal errors,
function arguments
-@cindex @command{gawk} @subentry function arguments and
-@cindex differences in @command{awk} and @command{gawk} @subentry function
arguments
-Each built-in function accepts a certain number of arguments.
-In some cases, arguments can be omitted. The defaults for omitted
-arguments vary from function to function and are described under the
-individual functions. In some @command{awk} implementations, extra
-arguments given to built-in functions are ignored. However, in @command{gawk},
-it is a fatal error to give extra arguments to a built-in function.
-
-When a function is called, expressions that create the function's actual
-parameters are evaluated completely before the call is performed.
-For example, in the following code fragment:
-
-@example
-i = 4
-j = sqrt(i++)
-@end example
-
-@cindex evaluation order @subentry functions
-@cindex functions @subentry built-in @subentry evaluation order
-@cindex built-in functions @subentry evaluation order
-@noindent
-the variable @code{i} is incremented to the value five before @code{sqrt()}
-is called with a value of four for its actual parameter.
-The order of evaluation of the expressions used for the function's
-parameters is undefined. Thus, avoid writing programs that
-assume that parameters are evaluated from left to right or from
-right to left. For example:
-
-@example
-i = 5
-j = atan2(++i, i *= 2)
-@end example
-
-If the order of evaluation is left to right, then @code{i} first becomes
-six, and then 12, and @code{atan2()} is called with the two arguments six
-and 12. But if the order of evaluation is right to left, @code{i}
-first becomes 10, then 11, and @code{atan2()} is called with the
-two arguments 11 and 10.
-
-
-@node Boolean Functions
-@subsection Generating Boolean Values
-@cindex boolean function
-
-This function is specific to @command{gawk}. It is not
-available in compatibility mode (@pxref{Options}):
-
-@c @asis for docbook
-@table @asis
-@item @code{mkbool(@var{expression})}
-@cindexgawkfunc{mkbool}
-Return a Boolean-typed value based on the regular Boolean value
-of @var{expression}. Boolean ``true'' values have numeric value one.
-Boolean ``false'' values have numeric
-zero. This is discussed in more
-detail in @ref{Boolean Typed Values}.
-@end table
-
-@node Numeric Functions
-@subsection Numeric Functions
-@cindex numeric @subentry functions
-
-The following list describes all of
-the built-in functions that work with numbers.
-Optional parameters are enclosed in square brackets@w{ ([ ]):}
-
-@c @asis for docbook
-@table @asis
-@item @code{atan2(@var{y}, @var{x})}
-@cindexawkfunc{atan2}
-@cindex arctangent
-Return the arctangent of @code{@var{y} / @var{x}} in radians.
-You can use @samp{pi = atan2(0, -1)} to retrieve the value of
-@value{PI}.
-
-@item @code{cos(@var{x})}
-@cindexawkfunc{cos}
-@cindex cosine
-Return the cosine of @var{x}, with @var{x} in radians.
-
-@item @code{exp(@var{x})}
-@cindexawkfunc{exp}
-@cindex exponent
-Return the exponential of @var{x} (@code{e ^ @var{x}}) or report
-an error if @var{x} is out of range. The range of values @var{x} can have
-depends on your machine's floating-point representation.
-
-@item @code{int(@var{x})}
-@cindexawkfunc{int}
-@cindex round to nearest integer
-Return the nearest integer to @var{x}, located between @var{x} and zero and
-truncated toward zero.
-For example, @code{int(3)} is 3, @code{int(3.9)} is 3, @code{int(-3.9)}
-is @minus{}3, and @code{int(-3)} is @minus{}3 as well.
-
-@ifset INTDIV
-@item @code{intdiv0(@var{numerator}, @var{denominator}, @var{result})}
-@cindexawkfunc{intdiv0}
-@cindex intdiv0
-Perform integer division, similar to the standard C @code{div()} function.
-First, truncate @code{numerator} and @code{denominator}
-towards zero, creating integer values. Clear the @code{result}
-array, and then set @code{result["quotient"]} to the result of
-@samp{numerator / denominator}, truncated towards zero to an integer,
-and set @code{result["remainder"]} to the result of @samp{numerator %
-denominator}, truncated towards zero to an integer.
-Attempting division by zero causes a fatal error.
-The function returns zero upon success, and @minus{}1 upon error.
-
-This function is
-primarily intended for use with arbitrary length integers; it avoids
-creating MPFR arbitrary precision floating-point values (@pxref{Arbitrary
-Precision Integers}).
-
-This function is a @code{gawk} extension. It is not available in
-compatibility mode (@pxref{Options}).
-@end ifset
-
-@item @code{log(@var{x})}
-@cindexawkfunc{log}
-@cindex logarithm
-Return the natural logarithm of @var{x}, if @var{x} is positive;
-otherwise, return NaN (``not a number'') on IEEE 754 systems.
-Additionally, @command{gawk} prints a warning message when @code{x}
-is negative.
-
-@cindex Beebe, Nelson H.F.@:
-@item @code{rand()}
-@cindexawkfunc{rand}
-@cindex random numbers @subentry @code{rand()}/@code{srand()} functions
-Return a random number. The values of @code{rand()} are
-uniformly distributed between zero and one.
-The value could be zero but is never one.@footnote{The C version of
-@code{rand()} on many Unix systems is known to produce fairly poor
-sequences of random numbers. However, nothing requires that an
-@command{awk} implementation use the C @code{rand()} to implement the
-@command{awk} version of @code{rand()}. In fact, for many years,
-@command{gawk} used the BSD @code{random()} function, which is
-considerably better than @code{rand()}, to produce random numbers.
-From @value{PVERSION} 4.1.4, courtesy of Nelson H.F.@: Beebe, @command{gawk}
-uses the Bayes-Durham shuffle buffer algorithm which considerably extends
-the period of the random number generator, and eliminates short-range and
-long-range correlations that might exist in the original generator.}
-
-Often random integers are needed instead. Following is a user-defined function
-that can be used to obtain a random nonnegative integer less than @var{n}:
-
-@example
-function randint(n)
-@{
- return int(n * rand())
-@}
-@end example
-
-@noindent
-The multiplication produces a random number greater than or equal to
-zero and less than @code{n}. Using @code{int()}, this result is made into
-an integer between zero and @code{n} @minus{} 1, inclusive.
-
-The following example uses a similar function to produce random integers
-between one and @var{n}. This program prints a new random number for
-each input record:
-
-@example
-# Function to roll a simulated die.
-function roll(n) @{ return 1 + int(rand() * n) @}
-
-# Roll 3 six-sided dice and
-# print total number of points.
-@{
- printf("%d points\n", roll(6) + roll(6) + roll(6))
-@}
-@end example
-
-@cindex seeding random number generator
-@cindex random numbers @subentry seed of
-@quotation CAUTION
-In most @command{awk} implementations, including @command{gawk},
-@code{rand()} starts generating numbers from the same
-starting number, or @dfn{seed}, each time you run
@command{awk}.@footnote{@command{mawk}
-uses a different seed each time.} Thus,
-a program generates the same results each time you run it.
-The numbers are random within one @command{awk} run but predictable
-from run to run. This is convenient for debugging, but if you want
-a program to do different things each time it is used, you must change
-the seed to a value that is different in each run. To do this,
-use @code{srand()}.
-@end quotation
-
-@item @code{sin(@var{x})}
-@cindexawkfunc{sin}
-@cindex sine
-Return the sine of @var{x}, with @var{x} in radians.
-
-@item @code{sqrt(@var{x})}
-@cindexawkfunc{sqrt}
-@cindex square root
-Return the positive square root of @var{x}.
-@command{gawk} prints a warning message
-if @var{x} is negative. Thus, @code{sqrt(4)} is 2.
-
-@item @code{srand(}[@var{x}]@code{)}
-@cindexawkfunc{srand}
-Set the starting point, or seed,
-for generating random numbers to the value @var{x}.
-
-Each seed value leads to a particular sequence of random
-numbers.@footnote{Computer-generated random numbers really are not truly
-random. They are technically known as @dfn{pseudorandom}. This means
-that although the numbers in a sequence appear to be random, you can in
-fact generate the same sequence of random numbers over and over again.}
-Thus, if the seed is set to the same value a second time,
-the same sequence of random numbers is produced again.
-
-@quotation CAUTION
-Different @command{awk} implementations use different random-number
-generators internally. Don't expect the same @command{awk} program
-to produce the same series of random numbers when executed by
-different versions of @command{awk}.
-@end quotation
-
-If the argument @var{x} is omitted, as in @samp{srand()}, then the current
-date and time of day are used for a seed. This is the way to get random
-numbers that are truly unpredictable.
-
-The return value of @code{srand()} is the previous seed. This makes it
-easy to keep track of the seeds in case you need to consistently reproduce
-sequences of random numbers.
-
-POSIX does not specify the initial seed; it differs among @command{awk}
-implementations.
-@end table
-
-@node String Functions
-@subsection String-Manipulation Functions
-@cindex string-manipulation functions
-
-The functions in this @value{SECTION} look at or change the text of one
-or more strings.
-
-@command{gawk} understands locales (@pxref{Locales}) and does all
-string processing in terms of @emph{characters}, not @emph{bytes}.
-This distinction is particularly important to understand for locales
-where one character may be represented by multiple bytes. Thus, for
-example, @code{length()} returns the number of characters in a string,
-and not the number of bytes used to represent those characters. Similarly,
-@code{index()} works with character indices, and not byte indices.
-
-@quotation CAUTION
-A number of functions deal with indices into strings. For these
-functions, the first character of a string is at position (index) one.
-This is different from C and the languages descended from it, where the
-first character is at position zero. You need to remember this when
-doing index calculations, particularly if you are used to C.
-@end quotation
-
-In the following list, optional parameters are enclosed in square brackets@w{
([ ]).}
-Several functions perform string substitution; the full discussion is
-provided in the description of the @code{sub()} function, which comes
-toward the end, because the list is presented alphabetically.
-
-Those functions that are specific to @command{gawk} are marked with a
-pound sign (@samp{#}). They are not available in compatibility mode
-(@pxref{Options}):
-
-
-@menu
-* Gory Details:: More than you want to know about @samp{\} and
- @samp{&} with @code{sub()}, @code{gsub()}, and
- @code{gensub()}.
-@end menu
-
-@c @asis for docbook
-@table @asis
-@item @code{asort(}@var{source} [@code{,} @var{dest} [@code{,} @var{how} ]
]@code{) #}
-@itemx @code{asorti(}@var{source} [@code{,} @var{dest} [@code{,} @var{how} ]
]@code{) #}
-@cindexgawkfunc{asorti}
-@cindex sort array
-@cindex arrays @subentry elements @subentry retrieving number of
-@cindexgawkfunc{asort}
-@cindex sort array indices
-These two functions are similar in behavior, so they are described
-together.
-
-@quotation NOTE
-The following description ignores the third argument, @var{how}, as it
-requires understanding features that we have not discussed yet. Thus,
-the discussion here is a deliberate simplification. (We do provide all
-the details later on; see @ref{Array Sorting Functions} for the full story.)
-@end quotation
-
-Both functions return the number of elements in the array @var{source}.
-For @command{asort()}, @command{gawk} sorts the values of @var{source}
-and replaces the indices of the sorted values of @var{source} with
-sequential integers starting with one. If the optional array @var{dest}
-is specified, then @var{source} is duplicated into @var{dest}. @var{dest}
-is then sorted, leaving the indices of @var{source} unchanged.
-
-@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
-When comparing strings, @code{IGNORECASE} affects the sorting
-(@pxref{Array Sorting Functions}). If the
-@var{source} array contains subarrays as values (@pxref{Arrays of
-Arrays}), they will come last, after all scalar values.
-Subarrays are @emph{not} recursively sorted.
-
-For example, if the contents of @code{a} are as follows:
-
-@example
-a["last"] = "de"
-a["first"] = "sac"
-a["middle"] = "cul"
-@end example
-
-@noindent
-A call to @code{asort()}:
-
-@example
-asort(a)
-@end example
-
-@noindent
-results in the following contents of @code{a}:
-
-@example
-@group
-a[1] = "cul"
-a[2] = "de"
-a[3] = "sac"
-@end group
-@end example
-
-The @code{asorti()} function works similarly to @code{asort()}; however,
-the @emph{indices} are sorted, instead of the values. Thus, in the
-previous example, starting with the same initial set of indices and
-values in @code{a}, calling @samp{asorti(a)} would yield:
-
-@example
-a[1] = "first"
-a[2] = "last"
-a[3] = "middle"
-@end example
-
-@quotation NOTE
-You may not use either @code{SYMTAB} or @code{FUNCTAB} as the second
-argument to these functions. Attempting to do so produces a fatal error.
-You may use them as the first argument, but only if providing a second
-array to use for the actual sorting.
-@end quotation
-
-You are allowed to use the same array for both the @var{source} and @var{dest}
-arguments, but doing so only makes sense if you're also supplying the third
argument.
-
-@item @code{gensub(@var{regexp}, @var{replacement}, @var{how}} [@code{,
@var{target}}]@code{) #}
-@cindexgawkfunc{gensub}
-@cindex search and replace in strings
-@cindex substitute in string
-Search the target string @var{target} for matches of the regular
-expression @var{regexp}. If @var{how} is a string beginning with
-@samp{g} or @samp{G} (short for ``global''), then replace all matches
-of @var{regexp} with @var{replacement}. Otherwise, treat @var{how}
-as a number indicating which match of @var{regexp} to replace. Treat
-numeric values less than one as if they were one. If no @var{target}
-is supplied, use @code{$0}. Return the modified string as the result
-of the function. The original target string is @emph{not} changed.
-
-The returned value is @emph{always} a string, even if the original
-@var{target} was a number or a regexp value.
-
-@code{gensub()} is a general substitution function. Its purpose is
-to provide more features than the standard @code{sub()} and @code{gsub()}
-functions.
-
-@code{gensub()} provides an additional feature that is not available
-in @code{sub()} or @code{gsub()}: the ability to specify components of a
-regexp in the replacement text. This is done by using parentheses in
-the regexp to mark the components and then specifying @samp{\@var{N}}
-in the replacement text, where @var{N} is a digit from 1 to 9.
-For example:
-
-@example
-$ @kbd{gawk '}
-> @kbd{BEGIN @{}
-> @kbd{a = "abc def"}
-> @kbd{b = gensub(/(.+) (.+)/, "\\2 \\1", "g", a)}
-> @kbd{print b}
-> @kbd{@}'}
-@print{} def abc
-@end example
-
-@noindent
-As with @code{sub()}, you must type two backslashes in order
-to get one into the string.
-In the replacement text, the sequence @samp{\0} represents the entire
-matched text, as does the character @samp{&}.
-
-The following example shows how you can use the third argument to control
-which match of the regexp should be changed:
-
-@example
-$ @kbd{echo a b c a b c |}
-> @kbd{gawk '@{ print gensub(/a/, "AA", 2) @}'}
-@print{} a b c AA b c
-@end example
-
-In this case, @code{$0} is the default target string.
-@code{gensub()} returns the new string as its result, which is
-passed directly to @code{print} for printing.
-
-@c @cindex automatic warnings
-@c @cindex warnings, automatic
-If the @var{how} argument is a string that does not begin with @samp{g} or
-@samp{G}, or if it is a number that is less than or equal to zero, only one
-substitution is performed. If @var{how} is zero, @command{gawk} issues
-a warning message.
-
-If @var{regexp} does not match @var{target}, @code{gensub()}'s return value
-is the original unchanged value of @var{target}. Note that, as mentioned
-above, the returned value is a string, even if @var{target} was not.
-
-In the replacement string, a backslash before a non-digit character
-is simply elided. For example, @samp{\q} becomes @samp{q} in the result.
-If the final character in the replacement string is a backslash,
-it is left alone.
-
-@item @code{gsub(@var{regexp}, @var{replacement}} [@code{,
@var{target}}]@code{)}
-@cindexawkfunc{gsub}
-Search @var{target} for
-@emph{all} of the longest, leftmost, @emph{nonoverlapping} matching
-substrings it can find and replace them with @var{replacement}.
-The @samp{g} in @code{gsub()} stands for
-``global,'' which means replace everywhere. For example:
-
-@example
-@{ gsub(/Britain/, "United Kingdom"); print @}
-@end example
-
-@noindent
-replaces all occurrences of the string @samp{Britain} with @samp{United
-Kingdom} for all input records.
-
-The @code{gsub()} function returns the number of substitutions made. If
-the variable to search and alter (@var{target}) is
-omitted, then the entire input record (@code{$0}) is used.
-As in @code{sub()}, the characters @samp{&} and @samp{\} are special,
-and the third argument must be assignable.
-
-@item @code{index(@var{in}, @var{find})}
-@cindexawkfunc{index}
-@cindex search for substring
-@cindex find substring in string
-Search the string @var{in} for the first occurrence of the string
-@var{find}, and return the position in characters where that occurrence
-begins in the string @var{in}. Consider the following example:
-
-@example
-$ @kbd{awk 'BEGIN @{ print index("peanut", "an") @}'}
-@print{} 3
-@end example
-
-@noindent
-If @var{find} is not found, @code{index()} returns zero.
-
-@cindex dark corner @subentry regexp as second argument to @code{index()}
-With BWK @command{awk} and @command{gawk},
-it is a fatal error to use a regexp constant for @var{find}.
-Other implementations allow it, simply treating the regexp
-constant as an expression meaning @samp{$0 ~ /regexp/}. @value{DARKCORNER}
-
-@item @code{length(}[@var{string}]@code{)}
-@cindexawkfunc{length}
-@cindex string @subentry length
-@cindex length of string
-Return the number of characters in @var{string}. If
-@var{string} is a number, the length of the digit string representing
-that number is returned. For example, @code{length("abcde")} is five. By
-contrast, @code{length(15 * 35)} works out to three. In this example,
-@iftex
-@math{15 @cdot 35 = 525},
-@end iftex
-@ifnottex
-@ifnotdocbook
-15 * 35 = 525,
-@end ifnotdocbook
-@end ifnottex
-@docbook
-15 ⋅ 35 = 525,
-@end docbook
-and 525 is then converted to the string @code{"525"}, which has
-three characters.
-
-@cindex length of input record
-@cindex input record, length of
-If no argument is supplied, @code{length()} returns the length of @code{$0}.
-
-@c @cindex historical features
-@cindex portability @subentry @code{length()} function
-@cindex POSIX @command{awk} @subentry functions and @subentry @code{length()}
-@quotation NOTE
-In older versions of @command{awk}, the @code{length()} function could
-be called
-without any parentheses. Doing so is considered poor practice,
-although the 2008 POSIX standard explicitly allows it, to
-support historical practice. For programs to be maximally portable,
-always supply the parentheses.
-@end quotation
-
-@cindex dark corner @subentry @code{length()} function
-If @code{length()} is called with a variable that has not been used,
-@command{gawk} forces the variable to be a scalar. Other
-implementations of @command{awk} leave the variable without a type.
-@value{DARKCORNER}
-Consider:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print length(x) ; x[1] = 1 @}'}
-@print{} 0
-@error{} gawk: fatal: attempt to use scalar `x' as array
-
-$ @kbd{nawk 'BEGIN @{ print length(x) ; x[1] = 1 @}'}
-@print{} 0
-@end example
-
-@noindent
-If @option{--lint} has
-been specified on the command line, @command{gawk} issues a
-warning about this.
-
-@cindex common extensions @subentry @code{length()} applied to an array
-@cindex extensions @subentry common @subentry @code{length()} applied to an
array
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{length()} function
-@cindex number of array elements
-@cindex arrays @subentry number of elements
-With @command{gawk} and several other @command{awk} implementations, when
given an
-array argument, the @code{length()} function returns the number of elements
-in the array. @value{COMMONEXT}
-This is less useful than it might seem at first, as the
-array is not guaranteed to be indexed from one to the number of elements
-in it.
-If @option{--lint} is provided on the command line
-(@pxref{Options}),
-@command{gawk} warns that passing an array argument is not portable.
-If @option{--posix} is supplied, using an array argument is a fatal error
-(@pxref{Arrays}).
-
-@item @code{match(@var{string}, @var{regexp}} [@code{, @var{array}}]@code{)}
-@cindexawkfunc{match}
-@cindex string @subentry regular expression match of
-@cindex match regexp in string
-Search @var{string} for the
-longest, leftmost substring matched by the regular expression
-@var{regexp} and return the character position (index)
-at which that substring begins (one, if it starts at the beginning of
-@var{string}). If no match is found, return zero.
-
-The @var{regexp} argument may be either a regexp constant
-(@code{/}@dots{}@code{/}) or a string constant (@code{"}@dots{}@code{"}).
-In the latter case, the string is treated as a regexp to be matched.
-@xref{Computed Regexps} for a
-discussion of the difference between the two forms, and the
-implications for writing your program correctly.
-
-The order of the first two arguments is the opposite of most other string
-functions that work with regular expressions, such as
-@code{sub()} and @code{gsub()}. It might help to remember that
-for @code{match()}, the order is the same as for the @samp{~} operator:
-@samp{@var{string} ~ @var{regexp}}.
-
-@cindex @code{RSTART} variable @subentry @code{match()} function and
-@cindex @code{RLENGTH} variable @subentry @code{match()} function and
-@cindex @code{match()} function @subentry @code{RSTART}/@code{RLENGTH}
variables
-@cindex @code{match()} function @subentry side effects
-@cindex side effects @subentry @code{match()} function
-The @code{match()} function sets the predefined variable @code{RSTART} to
-the index. It also sets the predefined variable @code{RLENGTH} to the
-length in characters of the matched substring. If no match is found,
-@code{RSTART} is set to zero, and @code{RLENGTH} to @minus{}1.
-
-For example:
-
-@example
-@c file eg/misc/findpat.awk
-@{
- if ($1 == "FIND")
- regex = $2
- else @{
- where = match($0, regex)
- if (where != 0)
- print "Match of", regex, "found at", where, "in", $0
- @}
-@}
-@c endfile
-@end example
-
-@noindent
-This program looks for lines that match the regular expression stored in
-the variable @code{regex}. This regular expression can be changed. If the
-first word on a line is @samp{FIND}, @code{regex} is changed to be the
-second word on that line. Therefore, if given:
-
-@example
-@c file eg/misc/findpat.data
-FIND ru+n
-My program runs
-but not very quickly
-FIND Melvin
-JF+KM
-This line is property of Reality Engineering Co.
-Melvin was here.
-@c endfile
-@end example
-
-@noindent
-@command{awk} prints:
-
-@example
-Match of ru+n found at 12 in My program runs
-Match of Melvin found at 1 in Melvin was here.
-@end example
-
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{match()} function
-If @var{array} is present, it is cleared, and then the zeroth element
-of @var{array} is set to the entire portion of @var{string}
-matched by @var{regexp}. If @var{regexp} contains parentheses,
-the integer-indexed elements of @var{array} are set to contain the
-portion of @var{string} matching the corresponding parenthesized
-subexpression.
-For example:
-
-@example
-$ @kbd{echo foooobazbarrrrr |}
-> @kbd{gawk '@{ match($0, /(fo+).+(bar*)/, arr)}
-> @kbd{print arr[1], arr[2] @}'}
-@print{} foooo barrrrr
-@end example
-
-In addition,
-multidimensional subscripts are available providing
-the start index and length of each matched subexpression:
-
-@example
-$ @kbd{echo foooobazbarrrrr |}
-> @kbd{gawk '@{ match($0, /(fo+).+(bar*)/, arr)}
-> @kbd{print arr[1], arr[2]}
-> @kbd{print arr[1, "start"], arr[1, "length"]}
-> @kbd{print arr[2, "start"], arr[2, "length"]}
-> @kbd{@}'}
-@print{} foooo barrrrr
-@print{} 1 5
-@print{} 9 7
-@end example
-
-There may not be subscripts for the start and index for every parenthesized
-subexpression, because they may not all have matched text; thus, they
-should be tested for with the @code{in} operator
-(@pxref{Reference to Elements}).
-
-@cindex troubleshooting @subentry @code{match()} function
-The @var{array} argument to @code{match()} is a
-@command{gawk} extension. In compatibility mode
-(@pxref{Options}),
-using a third argument is a fatal error.
-
-@item @code{patsplit(@var{string}, @var{array}} [@code{, @var{fieldpat}}
[@code{, @var{seps}} ] ]@code{) #}
-@cindexgawkfunc{patsplit}
-@cindex split string into array
-Divide
-@var{string} into pieces (or ``fields'') defined by @var{fieldpat}
-and store the pieces in @var{array} and the separator strings in the
-@var{seps} array. The first piece is stored in
-@code{@var{array}[1]}, the second piece in @code{@var{array}[2]}, and so
-forth. The third argument, @var{fieldpat}, is
-a regexp describing the fields in @var{string} (just as @code{FPAT} is
-a regexp describing the fields in input records).
-It may be either a regexp constant or a string.
-If @var{fieldpat} is omitted, the value of @code{FPAT} is used.
-@code{patsplit()} returns the number of elements created.
-@code{@var{seps}[@var{i}]} is
-the possibly null separator string
-after @code{@var{array}[@var{i}]}.
-The possibly null leading separator will be in @code{@var{seps}[0]}.
-So a non-null @var{string} with @var{n} fields will have @var{n+1} separators.
-A null @var{string} has no fields or separators.
-
-The @code{patsplit()} function splits strings into pieces in a
-manner similar to the way input lines are split into fields using @code{FPAT}
-(@pxref{Splitting By Content}).
-
-Before splitting the string, @code{patsplit()} deletes any previously existing
-elements in the arrays @var{array} and @var{seps}.
-
-@item @code{split(@var{string}, @var{array}} [@code{, @var{fieldsep}} [@code{,
@var{seps}} ] ]@code{)}
-@cindexawkfunc{split}
-Divide @var{string} into pieces separated by @var{fieldsep}
-and store the pieces in @var{array} and the separator strings in the
-@var{seps} array. The first piece is stored in
-@code{@var{array}[1]}, the second piece in @code{@var{array}[2]}, and so
-forth. The string value of the third argument, @var{fieldsep}, is
-a regexp describing where to split @var{string} (much as @code{FS} can
-be a regexp describing where to split input records).
-If @var{fieldsep} is omitted, the value of @code{FS} is used.
-@code{split()} returns the number of elements created.
-@var{seps} is a @command{gawk} extension, with @code{@var{seps}[@var{i}]}
-being the separator string
-between @code{@var{array}[@var{i}]} and @code{@var{array}[@var{i}+1]}.
-If @var{fieldsep} is a single
-space, then any leading whitespace goes into @code{@var{seps}[0]} and
-any trailing
-whitespace goes into @code{@var{seps}[@var{n}]}, where @var{n} is the
-return value of
-@code{split()} (i.e., the number of elements in @var{array}).
-
-The @code{split()} function splits strings into pieces in the same way
-that input lines are split into fields. For example:
-
-@example
-split("cul-de-sac", a, "-", seps)
-@end example
-
-@noindent
-@cindex strings @subentry splitting, example
-splits the string @code{"cul-de-sac"} into three fields using @samp{-} as the
-separator. It sets the contents of the array @code{a} as follows:
-
-@example
-a[1] = "cul"
-a[2] = "de"
-a[3] = "sac"
-@end example
-
-and sets the contents of the array @code{seps} as follows:
-
-@example
-seps[1] = "-"
-seps[2] = "-"
-@end example
-
-@noindent
-The value returned by this call to @code{split()} is three.
-
-If @command{gawk} is invoked with @option{--csv}, then a two-argument
-call to @code{split()} splits the string using the CSV parsing rules as
-described in @ref{Comma Separated Fields}. With three and four arguments,
-@code{split()} works as just described. The four-argument call makes
-no sense, since each element of @var{seps} would simply consist of a
-string containing a comma.
-
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{split()} function
-As with input field-splitting, when the value of @var{fieldsep} is
-@w{@code{" "}}, leading and trailing whitespace is ignored in values assigned
to
-the elements of
-@var{array} but not in @var{seps}, and the elements
-are separated by runs of whitespace.
-Also, as with input field splitting, if @var{fieldsep} is the null string, each
-individual character in the string is split into its own array element.
-@value{COMMONEXT}
-Additionally, if @var{fieldsep} is a single-character string, that string acts
-as the separator, even if its value is a regular expression metacharacter.
-
-Note, however, that @code{RS} has no effect on the way @code{split()}
-works. Even though @samp{RS = ""} causes the newline character to also be an
input
-field separator, this does not affect how @code{split()} splits strings.
-
-@cindex dark corner @subentry @code{split()} function
-Modern implementations of @command{awk}, including @command{gawk}, allow
-the third argument to be a regexp constant (@w{@code{/}@dots{}@code{/}})
-as well as a string. @value{DARKCORNER}
-The POSIX standard allows this as well.
-@xref{Computed Regexps} for a
-discussion of the difference between using a string constant or a regexp
constant,
-and the implications for writing your program correctly.
-
-Before splitting the string, @code{split()} deletes any previously existing
-elements in the arrays @var{array} and @var{seps}.
-
-If @var{string} is null, the array has no elements. (So this is a portable
-way to delete an entire array with one statement.
-@xref{Delete}.)
-
-If @var{string} does not match @var{fieldsep} at all (but is not null),
-@var{array} has one element only. The value of that element is the original
-@var{string}.
-
-@cindex POSIX mode
-In POSIX mode (@pxref{Options}), the fourth argument is not allowed.
-
-@item @code{sprintf(@var{format}, @var{expression1}, @dots{})}
-@cindexawkfunc{sprintf}
-@cindex formatting @subentry strings
-Return (without printing) the string that @code{printf} would
-have printed out with the same arguments
-(@pxref{Printf}).
-For example:
-
-@example
-pival = sprintf("pi = %.2f (approx.)", 22/7)
-@end example
-
-@noindent
-assigns the string @w{@samp{pi = 3.14 (approx.)}} to the variable @code{pival}.
-
-@cindexgawkfunc{strtonum}
-@cindex converting @subentry string to numbers
-@item @code{strtonum(@var{str}) #}
-Examine @var{str} and return its numeric value. If @var{str}
-begins with a leading @samp{0}, @code{strtonum()} assumes that @var{str}
-is an octal number. If @var{str} begins with a leading @samp{0x} or
-@samp{0X}, @code{strtonum()} assumes that @var{str} is a hexadecimal number.
-For example:
-
-@example
-$ @kbd{echo 0x11 |}
-> @kbd{gawk '@{ printf "%d\n", strtonum($1) @}'}
-@print{} 17
-@end example
-
-Using the @code{strtonum()} function is @emph{not} the same as adding zero
-to a string value; the automatic coercion of strings to numbers
-works only for decimal data, not for octal or hexadecimal.@footnote{Unless
-you use the @option{--non-decimal-data} option, which isn't recommended.
-@xref{Nondecimal Data} for more information.}
-
-Note also that @code{strtonum()} uses the current locale's decimal point
-for recognizing numbers (@pxref{Locales}).
-
-@item @code{sub(@var{regexp}, @var{replacement}} [@code{,
@var{target}}]@code{)}
-@cindexawkfunc{sub}
-@cindex replace in string
-Search @var{target}, which is treated as a string, for the
-leftmost, longest substring matched by the regular expression @var{regexp}.
-Modify the entire string
-by replacing the matched text with @var{replacement}.
-The modified string becomes the new value of @var{target}.
-Return the number of substitutions made (zero or one).
-
-The @var{regexp} argument may be either a regexp constant
-(@code{/}@dots{}@code{/}) or a string constant (@code{"}@dots{}@code{"}).
-In the latter case, the string is treated as a regexp to be matched.
-@xref{Computed Regexps} for a
-discussion of the difference between the two forms, and the
-implications for writing your program correctly.
-
-This function is peculiar because @var{target} is not simply
-used to compute a value, and not just any expression will do---it
-must be a variable, field, or array element so that @code{sub()} can
-store a modified value there. If this argument is omitted, then the
-default is to use and alter @code{$0}.@footnote{Note that this means
-that the record will first be regenerated using the value of @code{OFS} if
-any fields have been changed, and that the fields will be updated
-after the substitution, even if the operation is a ``no-op'' such
-as @samp{sub(/^/, "")}.}
-For example:
-
-@example
-str = "water, water, everywhere"
-sub(/at/, "ith", str)
-@end example
-
-@noindent
-sets @code{str} to @w{@samp{wither, water, everywhere}}, by replacing the
-leftmost longest occurrence of @samp{at} with @samp{ith}.
-
-If the special character @samp{&} appears in @var{replacement}, it
-stands for the precise substring that was matched by @var{regexp}. (If
-the regexp can match more than one string, then this precise substring
-may vary.) For example:
-
-@example
-@{ sub(/candidate/, "& and his wife"); print @}
-@end example
-
-@noindent
-changes the first occurrence of @samp{candidate} to @samp{candidate
-and his wife} on each input line.
-Here is another example:
-
-@example
-$ @kbd{awk 'BEGIN @{}
-> @kbd{str = "daabaaa"}
-> @kbd{sub(/a+/, "C&C", str)}
-> @kbd{print str}
-> @kbd{@}'}
-@print{} dCaaCbaaa
-@end example
-
-@noindent
-This shows how @samp{&} can represent a nonconstant string and also
-illustrates the ``leftmost, longest'' rule in regexp matching
-(@pxref{Leftmost Longest}).
-
-The effect of this special character (@samp{&}) can be turned off by putting a
-backslash before it in the string. As usual, to insert one backslash in
-the string, you must write two backslashes. Therefore, write @samp{\\&}
-in a string constant to include a literal @samp{&} in the replacement.
-For example, the following shows how to replace the first @samp{|} on each
line with
-an @samp{&}:
-
-@example
-@{ sub(/\|/, "\\&"); print @}
-@end example
-
-@cindex @code{sub()} function @subentry arguments of
-@cindex @code{gsub()} function @subentry arguments of
-@cindex side effects @subentry @code{sub()} function
-@cindex side effects @subentry @code{gsub()} function
-As mentioned, the third argument to @code{sub()} must
-be a variable, field, or array element.
-Some versions of @command{awk} allow the third argument to
-be an expression that is not an lvalue. In such a case, @code{sub()}
-still searches for the pattern and returns zero or one, but the result of
-the substitution (if any) is thrown away because there is no place
-to put it. Such versions of @command{awk} accept expressions
-like the following:
-
-@example
-sub(/USA/, "United States", "the USA and Canada")
-@end example
-
-@noindent
-@cindex troubleshooting @subentry @code{gsub()}/@code{sub()} functions
-For historical compatibility, @command{gawk} accepts such erroneous code.
-However, using any other nonchangeable
-object as the third parameter causes a fatal error and your program
-will not run.
-
-Finally, if the @var{regexp} is not a regexp constant, it is converted into a
-string, and then the value of that string is treated as the regexp to match.
-
-@item @code{substr(@var{string}, @var{start}} [@code{, @var{length}} ]@code{)}
-@cindexawkfunc{substr}
-@cindex substring
-Return a @var{length}-character-long substring of @var{string},
-starting at character number @var{start}. The first character of a
-string is character number one.@footnote{This is different from
-C and C++, in which the first character is number zero.}
-For example, @code{substr("washington", 5, 3)} returns @code{"ing"}.
-
-If @var{length} is not present, @code{substr()} returns the whole suffix of
-@var{string} that begins at character number @var{start}. For example,
-@code{substr("washington", 5)} returns @code{"ington"}. The whole
-suffix is also returned
-if @var{length} is greater than the number of characters remaining
-in the string, counting from character @var{start}.
-
-@cindex Brian Kernighan's @command{awk}
-If @var{start} is less than one, @code{substr()} treats it as
-if it was one. (POSIX doesn't specify what to do in this case:
-BWK @command{awk} acts this way, and therefore @command{gawk}
-does too.)
-If @var{start} is greater than the number of characters
-in the string, @code{substr()} returns the null string.
-Similarly, if @var{length} is present but less than or equal to zero,
-the null string is returned.
-
-@cindex troubleshooting @subentry @code{substr()} function
-The string returned by @code{substr()} @emph{cannot} be
-assigned. Thus, it is a mistake to attempt to change a portion of
-a string, as shown in the following example:
-
-@example
-string = "abcdef"
-# try to get "abCDEf", won't work
-substr(string, 3, 3) = "CDE"
-@end example
-
-@noindent
-It is also a mistake to use @code{substr()} as the third argument
-of @code{sub()} or @code{gsub()}:
-
-@example
-gsub(/xyz/, "pdq", substr($0, 5, 20)) # WRONG
-@end example
-
-@cindex portability @subentry @code{substr()} function
-(Some commercial versions of @command{awk} treat
-@code{substr()} as assignable, but doing so is not portable.)
-
-If you need to replace bits and pieces of a string, combine @code{substr()}
-with string concatenation, in the following manner:
-
-@example
-string = "abcdef"
-@dots{}
-string = substr(string, 1, 2) "CDE" substr(string, 6)
-@end example
-
-@cindex case sensitivity @subentry converting case
-@cindex strings @subentry converting letter case
-@item @code{tolower(@var{string})}
-@cindexawkfunc{tolower}
-@cindex converting @subentry string to lower case
-Return a copy of @var{string}, with each uppercase character
-in the string replaced with its corresponding lowercase character.
-Nonalphabetic characters are left unchanged. For example,
-@code{tolower("MiXeD cAsE 123")} returns @code{"mixed case 123"}.
-
-@item @code{toupper(@var{string})}
-@cindexawkfunc{toupper}
-@cindex converting @subentry string to upper case
-Return a copy of @var{string}, with each lowercase character
-in the string replaced with its corresponding uppercase character.
-Nonalphabetic characters are left unchanged. For example,
-@code{toupper("MiXeD cAsE 123")} returns @code{"MIXED CASE 123"}.
-@end table
-
-At first glance, the @code{split()} and @code{patsplit()} functions appear to
be
-mirror images of each other. But there are differences:
-
-@itemize @bullet
-@item @code{split()} treats its third argument like @code{FS}, with all the
-special rules involved for @code{FS}.
-
-@item Matching of null strings differs. This is discussed in @ref{FS versus
FPAT}.
-@end itemize
-
-@sidebar Matching the Null String
-@cindex matching @subentry null strings
-@cindex null strings @subentry matching
-@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry null
strings, matching
-@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry null
strings, matching
-
-In @command{awk}, the @samp{*} operator can match the null string.
-This is particularly important for the @code{sub()}, @code{gsub()},
-and @code{gensub()} functions. For example:
-
-@example
-$ @kbd{echo abc | awk '@{ gsub(/m*/, "X"); print @}'}
-@print{} XaXbXcX
-@end example
-
-@noindent
-Although this makes a certain amount of sense, it can be surprising.
-@end sidebar
-
-
-@node Gory Details
-@subsubsection More about @samp{\} and @samp{&} with @code{sub()},
@code{gsub()}, and @code{gensub()}
-
-@cindex escape processing @subentry @code{gsub()}/@code{gensub()}/@code{sub()}
functions
-@cindex @code{sub()} function @subentry escape processing
-@cindex @code{gsub()} function @subentry escape processing
-@cindex @code{gensub()} function (@command{gawk}) @subentry escape processing
-@cindex @code{\} (backslash) @subentry
@code{gsub()}/@code{gensub()}/@code{sub()} functions and
-@cindex backslash (@code{\}) @subentry
@code{gsub()}/@code{gensub()}/@code{sub()} functions and
-@cindex @code{&} (ampersand) @subentry
@code{gsub()}/@code{gensub()}/@code{sub()} functions and
-@cindex ampersand (@code{&}) @subentry
@code{gsub()}/@code{gensub()}/@code{sub()} functions and
-@cindex Spengler, Egon
-@cindex Ghostbusters
-@quotation
-@i{I collect spores, molds, and fungus.}
-@author Dr.@: Egon Spengler (``Ghostbusters,'' 1984)
-@end quotation
-
-@quotation CAUTION
-This subsubsection has been reported to cause headaches.
-You might want to skip it upon first reading.
-@end quotation
-
-When using @code{sub()}, @code{gsub()}, or @code{gensub()}, and trying to get
literal
-backslashes and ampersands into the replacement text, you need to remember
-that there are several levels of @dfn{escape processing} going on.
-
-First, there is the @dfn{lexical} level, which is when @command{awk} reads
-your program
-and builds an internal copy of it to execute.
-Then there is the runtime level, which is when @command{awk} actually scans the
-replacement string to determine what to generate.
-
-@cindex Brian Kernighan's @command{awk}
-At both levels, @command{awk} looks for a defined set of characters that
-can come after a backslash. At the lexical level, it looks for the
-escape sequences listed in @ref{Escape Sequences}.
-Thus, for every @samp{\} that @command{awk} processes at the runtime
-level, you must type two backslashes at the lexical level.
-When a character that is not valid for an escape sequence follows the
-@samp{\}, BWK @command{awk} and @command{gawk} both simply remove the initial
-@samp{\} and put the next character into the string. Thus, for
-example, @code{"a\qb"} is treated as @code{"aqb"}.
-
-At the runtime level, the various functions handle sequences of
-@samp{\} and @samp{&} differently. The situation is (sadly) somewhat complex.
-Historically, the @code{sub()} and @code{gsub()} functions treated the
-two-character sequence @samp{\&} specially; this sequence was replaced in
-the generated text with a single @samp{&}. Any other @samp{\} within
-the @var{replacement} string that did not precede an @samp{&} was passed
-through unchanged. This is illustrated in @ref{table-sub-escapes}.
-
-@c Thank to Karl Berry for help with the TeX stuff.
-@float Table,table-sub-escapes
-@caption{Historical escape sequence processing for @code{sub()} and
@code{gsub()}}
-@tex
-\vbox{\bigskip
-% We need more characters for escape and tab ...
-\catcode`_ = 0
-\catcode`! = 4
-% ... since this table has lots of &'s and \'s, so we unspecialize them.
-\catcode`\& = \other \catcode`\\ = \other
-_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
- You type!@code{sub()} sees!@code{sub()} generates_cr
-_hrulefill!_hrulefill!_hrulefill_cr
- @code{\&}! @code{&}!The matched text_cr
- @code{\\&}! @code{\&}!A literal @samp{&}_cr
- @code{\\\&}! @code{\&}!A literal @samp{&}_cr
- @code{\\\\&}! @code{\\&}!A literal @samp{\&}_cr
- @code{\\\\\&}! @code{\\&}!A literal @samp{\&}_cr
-@code{\\\\\\&}! @code{\\\&}!A literal @samp{\\&}_cr
- @code{\\q}! @code{\q}!A literal @samp{\q}_cr
-}
-_bigskip}
-@end tex
-@ifdocbook
-@multitable @columnfractions .20 .20 .60
-@headitem You type @tab @code{sub()} sees @tab @code{sub()} generates
-@item @code{\&} @tab @code{&} @tab The matched text
-@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
-@item @code{\\\&} @tab @code{\&} @tab A literal @samp{&}
-@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\&}
-@item @code{\\\\\&} @tab @code{\\&} @tab A literal @samp{\&}
-@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\\&}
-@item @code{\\q} @tab @code{\q} @tab A literal @samp{\q}
-@end multitable
-@end ifdocbook
-@ifnottex
-@ifnotdocbook
-@display
- You type @code{sub()} sees @code{sub()} generates
- -------- ---------- ---------------
- @code{\&} @code{&} The matched text
- @code{\\&} @code{\&} A literal @samp{&}
- @code{\\\&} @code{\&} A literal @samp{&}
- @code{\\\\&} @code{\\&} A literal @samp{\&}
- @code{\\\\\&} @code{\\&} A literal @samp{\&}
-@code{\\\\\\&} @code{\\\&} A literal @samp{\\&}
- @code{\\q} @code{\q} A literal @samp{\q}
-@end display
-@end ifnotdocbook
-@end ifnottex
-@end float
-
-@noindent
-This table shows the lexical-level processing, where
-an odd number of backslashes becomes an even number at the runtime level,
-as well as the runtime processing done by @code{sub()}.
-(For the sake of simplicity, the rest of the following tables only show the
-case of even numbers of backslashes entered at the lexical level.)
-
-The problem with the historical approach is that there is no way to get
-a literal @samp{\} followed by the matched text.
-
-Several editions of the POSIX standard attempted to fix this problem
-but weren't successful. The details are irrelevant at this point in time.
-
-At one point, the @command{gawk} maintainer submitted
-proposed text for a revised standard that
-reverts to rules that correspond more closely to the original existing
-practice. The proposed rules have special cases that make it possible
-to produce a @samp{\} preceding the matched text.
-This is shown in
-@ref{table-sub-proposed}.
-
-@float Table,table-sub-proposed
-@caption{@command{gawk} rules for @code{sub()} and backslash}
-@tex
-\vbox{\bigskip
-% We need more characters for escape and tab ...
-\catcode`_ = 0
-\catcode`! = 4
-% ... since this table has lots of &'s and \'s, so we unspecialize them.
-\catcode`\& = \other \catcode`\\ = \other
-_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
- You type!@code{sub()} sees!@code{sub()} generates_cr
-_hrulefill!_hrulefill!_hrulefill_cr
-@code{\\\\\\&}! @code{\\\&}!A literal @samp{\&}_cr
-@code{\\\\&}! @code{\\&}!A literal @samp{\}, followed by the matched
text_cr
- @code{\\&}! @code{\&}!A literal @samp{&}_cr
- @code{\\q}! @code{\q}!A literal @samp{\q}_cr
- @code{\\\\}! @code{\\}!@code{\\}_cr
-}
-_bigskip}
-@end tex
-@ifdocbook
-@multitable @columnfractions .20 .20 .60
-@headitem You type @tab @code{sub()} sees @tab @code{sub()} generates
-@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\&}
-@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\}, followed by the
matched text
-@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
-@item @code{\\q} @tab @code{\q} @tab A literal @samp{\q}
-@item @code{\\\\} @tab @code{\\} @tab @code{\\}
-@end multitable
-@end ifdocbook
-@ifnottex
-@ifnotdocbook
-@display
- You type @code{sub()} sees @code{sub()} generates
- -------- ---------- ---------------
-@code{\\\\\\&} @code{\\\&} A literal @samp{\&}
- @code{\\\\&} @code{\\&} A literal @samp{\}, followed
by the matched text
- @code{\\&} @code{\&} A literal @samp{&}
- @code{\\q} @code{\q} A literal @samp{\q}
- @code{\\\\} @code{\\} @code{\\}
-@end display
-@end ifnotdocbook
-@end ifnottex
-@end float
-
-In a nutshell, at the runtime level, there are now three special sequences
-of characters (@samp{\\\&}, @samp{\\&}, and @samp{\&}) whereas historically
-there was only one. However, as in the historical case, any @samp{\} that
-is not part of one of these three sequences is not special and appears
-in the output literally.
-
-@command{gawk} 3.0 and 3.1 follow these rules for @code{sub()} and
-@code{gsub()}. The POSIX standard took much longer to be revised than
-was expected. In addition, the @command{gawk} maintainer's proposal was
-lost during the standardization process. The final rules are
-somewhat simpler. The results are similar except for one case.
-
-@cindex POSIX @command{awk} @subentry functions and @subentry
@code{gsub()}/@code{sub()}
-The POSIX rules state that @samp{\&} in the replacement string produces
-a literal @samp{&}, @samp{\\} produces a literal @samp{\}, and @samp{\}
followed
-by anything else is not special; the @samp{\} is placed straight into the
output.
-These rules are presented in @ref{table-posix-sub}.
-
-@float Table,table-posix-sub
-@caption{POSIX rules for @code{sub()} and @code{gsub()}}
-@tex
-\vbox{\bigskip
-% We need more characters for escape and tab ...
-\catcode`_ = 0
-\catcode`! = 4
-% ... since this table has lots of &'s and \'s, so we unspecialize them.
-\catcode`\& = \other \catcode`\\ = \other
-_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
- You type!@code{sub()} sees!@code{sub()} generates_cr
-_hrulefill!_hrulefill!_hrulefill_cr
-@code{\\\\\\&}! @code{\\\&}!A literal @samp{\&}_cr
-@code{\\\\&}! @code{\\&}!A literal @samp{\}, followed by the matched
text_cr
- @code{\\&}! @code{\&}!A literal @samp{&}_cr
- @code{\\q}! @code{\q}!A literal @samp{\q}_cr
- @code{\\\\}! @code{\\}!@code{\}_cr
-}
-_bigskip}
-@end tex
-@ifdocbook
-@multitable @columnfractions .20 .20 .60
-@headitem You type @tab @code{sub()} sees @tab @code{sub()} generates
-@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\&}
-@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\}, followed by the
matched text
-@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
-@item @code{\\q} @tab @code{\q} @tab A literal @samp{\q}
-@item @code{\\\\} @tab @code{\\} @tab @code{\}
-@end multitable
-@end ifdocbook
-@ifnottex
-@ifnotdocbook
-@display
- You type @code{sub()} sees @code{sub()} generates
- -------- ---------- ---------------
-@code{\\\\\\&} @code{\\\&} A literal @samp{\&}
- @code{\\\\&} @code{\\&} A literal @samp{\}, followed
by the matched text
- @code{\\&} @code{\&} A literal @samp{&}
- @code{\\q} @code{\q} A literal @samp{\q}
- @code{\\\\} @code{\\} @code{\}
-@end display
-@end ifnotdocbook
-@end ifnottex
-@end float
-
-The only case where the difference is noticeable is the last one: @samp{\\\\}
-is seen as @samp{\\} and produces @samp{\} instead of @samp{\\}.
-
-Starting with @value{PVERSION} 3.1.4, @command{gawk} followed the POSIX rules
-when @option{--posix} was specified (@pxref{Options}). Otherwise,
-it continued to follow the proposed rules, as
-that had been its behavior for many years.
-
-When @value{PVERSION} 4.0.0 was released, the @command{gawk} maintainer
-made the POSIX rules the default, breaking well over a decade's worth
-of backward compatibility.@footnote{This was rather naive of him, despite
-there being a note in this @value{SECTION} indicating that the next major
version
-would move to the POSIX rules.} Needless to say, this was a bad idea,
-and as of @value{PVERSION} 4.0.1, @command{gawk} resumed its historical
-behavior, and only follows the POSIX rules when @option{--posix} is given.
-
-The rules for @code{gensub()} are considerably simpler. At the runtime
-level, whenever @command{gawk} sees a @samp{\}, if the following character
-is a digit, then the text that matched the corresponding parenthesized
-subexpression is placed in the generated output. Otherwise,
-no matter what character follows the @samp{\}, it
-appears in the generated text and the @samp{\} does not,
-as shown in @ref{table-gensub-escapes}.
-
-@float Table,table-gensub-escapes
-@caption{Escape sequence processing for @code{gensub()}}
-@tex
-\vbox{\bigskip
-% We need more characters for escape and tab ...
-\catcode`_ = 0
-\catcode`! = 4
-% ... since this table has lots of &'s and \'s, so we unspecialize them.
-\catcode`\& = \other \catcode`\\ = \other
-_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
- You type!@code{gensub()} sees!@code{gensub()} generates_cr
-_hrulefill!_hrulefill!_hrulefill_cr
- @code{&}! @code{&}!The matched text_cr
- @code{\\&}! @code{\&}!A literal @samp{&}_cr
- @code{\\\\}! @code{\\}!A literal @samp{\}_cr
- @code{\\\\&}! @code{\\&}!A literal @samp{\}, then the matched text_cr
-@code{\\\\\\&}! @code{\\\&}!A literal @samp{\&}_cr
- @code{\\q}! @code{\q}!A literal @samp{q}_cr
-}
-_bigskip}
-@end tex
-@ifdocbook
-@multitable @columnfractions .20 .20 .60
-@headitem You type @tab @code{gensub()} sees @tab @code{gensub()} generates
-@item @code{&} @tab @code{&} @tab The matched text
-@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
-@item @code{\\\\} @tab @code{\\} @tab A literal @samp{\}
-@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\}, then the
matched text
-@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\&}
-@item @code{\\q} @tab @code{\q} @tab A literal @samp{q}
-@end multitable
-@end ifdocbook
-@ifnottex
-@ifnotdocbook
-@display
- You type @code{gensub()} sees @code{gensub()} generates
- -------- ------------- ------------------
- @code{&} @code{&} The matched text
- @code{\\&} @code{\&} A literal @samp{&}
- @code{\\\\} @code{\\} A literal @samp{\}
- @code{\\\\&} @code{\\&} A literal @samp{\}, then
the matched text
-@code{\\\\\\&} @code{\\\&} A literal @samp{\&}
- @code{\\q} @code{\q} A literal @samp{q}
-@end display
-@end ifnotdocbook
-@end ifnottex
-@end float
-
-Because of the complexity of the lexical- and runtime-level processing
-and the special cases for @code{sub()} and @code{gsub()},
-we recommend the use of @command{gawk} and @code{gensub()} when you have
-to do substitutions.
-
-@node I/O Functions
-@subsection Input/Output Functions
-@cindex input/output @subentry functions
-
-The following functions relate to input/output (I/O).
-Optional parameters are enclosed in square brackets ([ ]):
-
-@table @asis
-@item @code{close(}@var{filename} [@code{,} @var{how}]@code{)}
-@cindexawkfunc{close}
-@cindex files @subentry closing
-@cindex close file or coprocess
-Close the file @var{filename} for input or output. Alternatively, the
-argument may be a shell command that was used for creating a coprocess, or
-for redirecting to or from a pipe; then the coprocess or pipe is closed.
-@xref{Close Files And Pipes}
-for more information.
-
-When closing a coprocess, it is occasionally useful to first close
-one end of the two-way pipe and then to close the other. This is done
-by providing a second argument to @code{close()}. This second argument
-(@var{how})
-should be one of the two string values @code{"to"} or @code{"from"},
-indicating which end of the pipe to close. Case in the string does
-not matter.
-@xref{Two-way I/O},
-which discusses this feature in more detail and gives an example.
-
-Note that the second argument to @code{close()} is a @command{gawk}
-extension; it is not available in compatibility mode (@pxref{Options}).
-
-@item @code{fflush(}[@var{filename}]@code{)}
-@cindexawkfunc{fflush}
-@cindex flush buffered output
-Flush any buffered output associated with @var{filename}, which is either a
-file opened for writing or a shell command for redirecting output to
-a pipe or coprocess.
-
-@cindex buffers @subentry flushing
-@cindex output @subentry buffering
-Many utility programs @dfn{buffer} their output (i.e., they save information
-to write to a disk file or the screen in memory until there is enough
-for it to be worthwhile to send the data to the output device).
-This is often more efficient than writing
-every little bit of information as soon as it is ready. However, sometimes
-it is necessary to force a program to @dfn{flush} its buffers (i.e.,
-write the information to its destination, even if a buffer is not full).
-This is the purpose of the @code{fflush()} function---@command{gawk} also
-buffers its output, and the @code{fflush()} function forces
-@command{gawk} to flush its buffers.
-
-@cindex extensions @subentry common @subentry @code{fflush()} function
-@cindex Brian Kernighan's @command{awk}
-Brian Kernighan added @code{fflush()} to his @command{awk} in April
-1992. For two decades, it was a common extension. In December
-2012, it was accepted for inclusion into the POSIX standard.
-See @uref{http://austingroupbugs.net/view.php?id=634, the Austin Group
website}.
-
-POSIX standardizes @code{fflush()} as follows: if there
-is no argument, or if the argument is the null string (@w{@code{""}}),
-then @command{awk} flushes the buffers for @emph{all} open output files
-and pipes.
-
-@quotation NOTE
-Prior to @value{PVERSION} 4.0.2, @command{gawk}
-would flush only the standard output if there was no argument,
-and flush all output files and pipes if the argument was the null
-string. This was changed in order to be compatible with BWK
-@command{awk}, in the hope that standardizing this
-feature in POSIX would then be easier (which indeed proved to be the case).
-
-With @command{gawk},
-you can use @samp{fflush("/dev/stdout")} if you wish to flush
-only the standard output.
-@end quotation
-
-@c @cindex automatic warnings
-@c @cindex warnings, automatic
-@cindex troubleshooting @subentry @code{fflush()} function
-@code{fflush()} returns zero if the buffer is successfully flushed;
-otherwise, it returns a nonzero value. (@command{gawk} returns @minus{}1.)
-In the case where all buffers are flushed, the return value is zero
-only if all buffers were flushed successfully. Otherwise, it is
-@minus{}1, and @command{gawk} warns about the problem @var{filename}.
-
-@command{gawk} also issues a warning message if you attempt to flush
-a file or pipe that was opened for reading (such as with @code{getline}),
-or if @var{filename} is not an open file, pipe, or coprocess.
-In such a case, @code{fflush()} returns @minus{}1, as well.
-
-@c end the table to let the sidebar take up the full width of the page.
-@end table
-
-@sidebar Interactive Versus Noninteractive Buffering
-@cindex buffering @subentry interactive vs.@: noninteractive
-
-As a side point, buffering issues can be even more confusing if
-your program is @dfn{interactive} (i.e., communicating
-with a user sitting at a keyboard).@footnote{A program is interactive
-if the standard output is connected to a terminal device. On modern
-systems, this means your keyboard and screen.}
-
-@c Thanks to Walter.Mecky@dresdnerbank.de for this example, and for
-@c motivating me to write this section.
-Interactive programs generally @dfn{line buffer} their output (i.e., they
-write out every line). Noninteractive programs wait until they have
-a full buffer, which may be many lines of output.
-Here is an example of the difference:
-
-@example
-$ @kbd{awk '@{ print $1 + $2 @}'}
-@kbd{1 1}
-@print{} 2
-@kbd{2 3}
-@print{} 5
-@kbd{Ctrl-d}
-@end example
-
-@noindent
-Each line of output is printed immediately. Compare that behavior
-with this example:
-
-@example
-$ @kbd{awk '@{ print $1 + $2 @}' | cat}
-@kbd{1 1}
-@kbd{2 3}
-@kbd{Ctrl-d}
-@print{} 2
-@print{} 5
-@end example
-
-@noindent
-Here, no output is printed until after the @kbd{Ctrl-d} is typed, because
-it is all buffered and sent down the pipe to @command{cat} in one shot.
-@end sidebar
-
-@table @asis
-@item @code{system(@var{command})}
-@cindexawkfunc{system}
-@cindex invoke shell command
-@cindex interacting with other programs
-Execute the operating system
-command @var{command} and then return to the @command{awk} program.
-Return @var{command}'s exit status (see further on).
-
-For example, if the following fragment of code is put in your @command{awk}
-program:
-
-@example
-END @{
- system("date | mail -s 'awk run done' root")
-@}
-@end example
-
-@noindent
-the system administrator is sent mail when the @command{awk} program
-finishes processing input and begins its end-of-input processing.
-
-Note that redirecting @code{print} or @code{printf} into a pipe is often
-enough to accomplish your task. If you need to run many commands, it
-is more efficient to simply print them down a pipeline to the shell:
-
-@example
-while (@var{more stuff to do})
- print @var{command} | "/bin/sh"
-close("/bin/sh")
-@end example
-
-@noindent
-@cindex troubleshooting @subentry @code{system()} function
-@cindex @option{--sandbox} option @subentry disabling @code{system()} function
-However, if your @command{awk}
-program is interactive, @code{system()} is useful for running large
-self-contained programs, such as a shell or an editor.
-Some operating systems cannot implement the @code{system()} function.
-@code{system()} causes a fatal error if it is not supported.
-
-@quotation NOTE
-When @option{--sandbox} is specified, the @code{system()} function is disabled
-(@pxref{Options}).
-@end quotation
-
-On POSIX systems, a command's exit status is a 16-bit number. The exit
-value passed to the C @code{exit()} function is held in the high-order
-eight bits. The low-order bits indicate if the process was killed by a
-signal (bit 7) and if so, the guilty signal number (bits 0--6).
-
-Traditionally, @command{awk}'s @code{system()} function has simply
-returned the exit status value divided by 256. In the normal case this
-gives the exit status but in the case of death-by-signal it yields
-a fractional floating-point value.@footnote{In private correspondence,
-Dr.@: Kernighan has indicated to me that the way this was done
-was probably a mistake.} POSIX states that @command{awk}'s
-@code{system()} should return the full 16-bit value.
-
-@command{gawk} steers a middle ground.
-The return values are summarized in @ref{table-system-return-values}.
-
-@float Table,table-system-return-values
-@caption{Return values from @code{system()}}
-@multitable @columnfractions .40 .60
-@headitem Situation @tab Return value from @code{system()}
-@item @option{--traditional} @tab C @code{system()}'s value divided by 256
-@item @option{--posix} @tab C @code{system()}'s value
-@item Normal exit of command @tab Command's exit status
-@item Death by signal of command @tab 256 + number of murderous signal
-@item Death by signal of command with core dump @tab 512 + number of murderous
signal
-@item Some kind of error @tab @minus{}1
-@end multitable
-@end float
-@end table
-
-As of August, 2018, BWK @command{awk} now follows @command{gawk}'s behavior
-for the return value of @code{system()}.
-
-@sidebar Controlling Output Buffering with @code{system()}
-@cindex buffers @subentry flushing
-@cindex buffering @subentry input/output
-@cindex output @subentry buffering
-
-The @code{fflush()} function provides explicit control over output buffering
for
-individual files and pipes. However, its use is not portable to many older
-@command{awk} implementations. An alternative method to flush output
-buffers is to call @code{system()} with a null string as its argument:
-
-@example
-system("") # flush output
-@end example
-
-@noindent
-@command{gawk} treats this use of the @code{system()} function as a special
-case and is smart enough not to run a shell (or other command
-interpreter) with the empty command. Therefore, with @command{gawk}, this
-idiom is not only useful, it is also efficient. Although this method should
work
-with other @command{awk} implementations, it does not necessarily avoid
-starting an unnecessary shell. (Other implementations may only
-flush the buffer associated with the standard output and not necessarily
-all buffered output.)
-
-If you think about what a programmer expects, it makes sense that
-@code{system()} should flush any pending output. The following program:
-
-@example
-BEGIN @{
- print "first print"
- system("echo system echo")
- print "second print"
-@}
-@end example
-
-@noindent
-must print:
-
-@example
-first print
-system echo
-second print
-@end example
-
-@noindent
-and not:
-
-@example
-system echo
-first print
-second print
-@end example
-
-If @command{awk} did not flush its buffers before calling @code{system()},
-you would see the latter (undesirable) output.
-@end sidebar
-
-@node Time Functions
-@subsection Time Functions
-@cindex time functions
-
-@cindex timestamps
-@cindex log files, timestamps in
-@cindex files @subentry log, timestamps in
-@cindex @command{gawk} @subentry timestamps
-@cindex POSIX @command{awk} @subentry timestamps and
-@command{awk} programs are commonly used to process log files
-containing timestamp information, indicating when a
-particular log record was written. Many programs log their timestamps
-in the form returned by the @code{time()} system call, which is the
-number of seconds since a particular epoch. On POSIX-compliant systems,
-it is the number of seconds since
-1970-01-01 00:00:00 UTC, not counting leap
-@ifclear FOR_PRINT
-seconds.@footnote{@xref{Glossary}, especially the entries ``Epoch'' and
``UTC.''}
-@end ifclear
-@ifset FOR_PRINT
-seconds.
-@end ifset
-All known POSIX-compliant systems support timestamps from 0 through
-@iftex
-@math{2^{31} - 1},
-@end iftex
-@ifinfo
-2^31 - 1,
-@end ifinfo
-@ifnottex
-@ifnotinfo
-2@sup{31} @minus{} 1,
-@end ifnotinfo
-@end ifnottex
-which is sufficient to represent times through
-2038-01-19 03:14:07 UTC. Many systems support a wider range of timestamps,
-including negative timestamps that represent times before the
-epoch.
-
-@cindex @command{date} utility @subentry GNU
-@cindex time @subentry retrieving
-In order to make it easier to process such log files and to produce
-useful reports, @command{gawk} provides the following functions for
-working with timestamps. They are @command{gawk} extensions; they are
-not specified in the POSIX standard.@footnote{The GNU @command{date} utility
can
-also do many of the things described here. Its use may be preferable
-for simple time-related operations in shell scripts.}
-However, recent versions
-of @command{mawk} (@pxref{Other Versions}) also support these functions.
-Optional parameters are enclosed in square brackets ([ ]):
-
-@c @asis for docbook
-@table @asis
-@item @code{mktime(@var{datespec}} [@code{, @var{utc-flag}} ]@code{)}
-@cindexgawkfunc{mktime}
-@cindex generate time values
-Turn @var{datespec} into a timestamp in the same form
-as is returned by @code{systime()}. It is similar to the function of the
-same name in ISO C. The argument, @var{datespec}, is a string of the form
-@w{@code{"@var{YYYY} @var{MM} @var{DD} @var{HH} @var{MM} @var{SS}
[@var{DST}]"}}.
-The string consists of six or seven numbers representing, respectively,
-the full year including century, the month from 1 to 12, the day of the month
-from 1 to 31, the hour of the day from 0 to 23, the minute from 0 to
-59, the second from 0 to 60,@footnote{Occasionally there are
-minutes in a year with a leap second, which is why the
-seconds can go up to 60.}
-and an optional daylight-savings flag.
-
-The values of these numbers need not be within the ranges specified;
-for example, an hour of @minus{}1 means 1 hour before midnight.
-The origin-zero Gregorian calendar is assumed, with year 0 preceding
-year 1 and year @minus{}1 preceding year 0.
-If @var{utc-flag} is present and is either nonzero or non-null, the time
-is assumed to be in the UTC time zone; otherwise, the
-time is assumed to be in the local time zone.
-If the @var{DST} daylight-savings flag is positive, the time is assumed to be
-daylight savings time; if zero, the time is assumed to be standard
-time; and if negative (the default), @code{mktime()} attempts to determine
-whether daylight savings time is in effect for the specified time.
-
-If @var{datespec} does not contain enough elements or if the resulting time
-is out of range, @code{mktime()} returns @minus{}1.
-
-@cindex @command{gawk} @subentry @code{PROCINFO} array in
-@cindex @code{PROCINFO} array
-@item @code{strftime(}[@var{format} [@code{,} @var{timestamp} [@code{,}
@var{utc-flag}] ] ]@code{)}
-@cindexgawkfunc{strftime}
-@cindex format time string
-Format the time specified by @var{timestamp}
-based on the contents of the @var{format} string and return the result.
-It is similar to the function of the same name in ISO C.
-If @var{utc-flag} is present and is either nonzero or non-null, the value
-is formatted as UTC (Coordinated Universal Time, formerly GMT or Greenwich
-Mean Time). Otherwise, the value is formatted for the local time zone.
-The @var{timestamp} is in the same format as the value returned by the
-@code{systime()} function. If no @var{timestamp} argument is supplied,
-@command{gawk} uses the current time of day as the timestamp.
-Without a @var{format} argument, @code{strftime()} uses
-the value of @code{PROCINFO["strftime"]} as the format string
-(@pxref{Built-in Variables}).
-The default string value is
-@code{@w{"%a %b %e %H:%M:%S %Z %Y"}}. This format string produces
-output that is equivalent to that of the @command{date} utility.
-You can assign a new value to @code{PROCINFO["strftime"]} to
-change the default format; see the following list for the various format
directives.
-
-@item @code{systime()}
-@cindexgawkfunc{systime}
-@cindex timestamps
-@cindex current system time
-Return the current time as the number of seconds since
-the system epoch. On POSIX systems, this is the number of seconds
-since 1970-01-01 00:00:00 UTC, not counting leap seconds.
-It may be a different number on other systems.
-@end table
-
-The @code{systime()} function allows you to compare a timestamp from a
-log file with the current time of day. In particular, it is easy to
-determine how long ago a particular record was logged. It also allows
-you to produce log records using the ``seconds since the epoch'' format.
-
-@cindex converting @subentry dates to timestamps
-@cindex dates @subentry converting to timestamps
-@cindex timestamps @subentry converting dates to
-The @code{mktime()} function allows you to convert a textual representation
-of a date and time into a timestamp. This makes it easy to do before/after
-comparisons of dates and times, particularly when dealing with date and
-time data coming from an external source, such as a log file.
-
-The @code{strftime()} function allows you to easily turn a timestamp
-into human-readable information. It is similar in nature to the
@code{sprintf()}
-function
-(@pxref{String Functions}),
-in that it copies nonformat specification characters verbatim to the
-returned string, while substituting date and time values for format
-specifications in the @var{format} string.
-
-@cindex format specifiers @subentry @code{strftime()} function (@command{gawk})
-@code{strftime()} is guaranteed by the 1999 ISO C
-standard@footnote{Unfortunately,
-not every system's @code{strftime()} necessarily
-supports all of the conversions listed here.}
-to support the following date format specifications:
-
-@table @code
-@item %a
-The locale's abbreviated weekday name.
-
-@item %A
-The locale's full weekday name.
-
-@item %b
-The locale's abbreviated month name.
-
-@item %B
-The locale's full month name.
-
-@item %c
-The locale's ``appropriate'' date and time representation.
-(This is @samp{%A %B %d %T %Y} in the @code{"C"} locale.)
-
-@item %C
-The century part of the current year.
-This is the year divided by 100 and truncated to the next
-lower integer.
-
-@item %d
-The day of the month as a decimal number (01--31).
-
-@item %D
-Equivalent to specifying @samp{%m/%d/%y}.
-
-@item %e
-The day of the month, padded with a space if it is only one digit.
-
-@item %F
-Equivalent to specifying @samp{%Y-%m-%d}.
-This is the ISO 8601 date format.
-
-@item %g
-The year modulo 100 of the ISO 8601 week number, as a decimal number (00--99).
-For example, January 1, 2012, is in week 53 of 2011. Thus, the year
-of its ISO 8601 week number is 2011, even though its year is 2012.
-Similarly, December 31, 2012, is in week 1 of 2013. Thus, the year
-of its ISO week number is 2013, even though its year is 2012.
-
-@item %G
-The full year of the ISO week number, as a decimal number.
-
-@item %h
-Equivalent to @samp{%b}.
-
-@item %H
-The hour (24-hour clock) as a decimal number (00--23).
-
-@item %I
-The hour (12-hour clock) as a decimal number (01--12).
-
-@item %j
-The day of the year as a decimal number (001--366).
-
-@item %m
-The month as a decimal number (01--12).
-
-@item %M
-The minute as a decimal number (00--59).
-
-@item %n
-A newline character (ASCII LF).
-
-@item %p
-The locale's equivalent of the AM/PM designations associated
-with a 12-hour clock.
-
-@item %r
-The locale's 12-hour clock time.
-(This is @samp{%I:%M:%S %p} in the @code{"C"} locale.)
-
-@item %R
-Equivalent to specifying @samp{%H:%M}.
-
-@item %S
-The second as a decimal number (00--60).
-
-@item %t
-A TAB character.
-
-@item %T
-Equivalent to specifying @samp{%H:%M:%S}.
-
-@item %u
-The weekday as a decimal number (1--7). Monday is day one.
-
-@item %U
-The week number of the year (with the first Sunday as the first day of week
one)
-as a decimal number (00--53).
-
-@cindex ISO @subentry ISO 8601 date and time standard
-@item %V
-The week number of the year (with the first Monday as the first
-day of week one) as a decimal number (01--53).
-The method for determining the week number is as specified by ISO 8601.
-(To wit: if the week containing January 1 has four or more days in the
-new year, then it is week one; otherwise it is the last week
-[52 or 53] of the previous year and the next week is week one.)
-
-@item %w
-The weekday as a decimal number (0--6). Sunday is day zero.
-
-@item %W
-The week number of the year (with the first Monday as the first day of week
one)
-as a decimal number (00--53).
-
-@item %x
-The locale's ``appropriate'' date representation.
-(This is @samp{%A %B %d %Y} in the @code{"C"} locale.)
-
-@item %X
-The locale's ``appropriate'' time representation.
-(This is @samp{%T} in the @code{"C"} locale.)
-
-@item %y
-The year modulo 100 as a decimal number (00--99).
-
-@item %Y
-The full year as a decimal number (e.g., 2015).
-
-@c @cindex RFC 822
-@c @cindex RFC 1036
-@item %z
-The time zone offset in a @samp{+@var{HHMM}} format (e.g., the format
-necessary to produce RFC 822/RFC 1036 date headers).
-
-@item %Z
-The time zone name or abbreviation; no characters if
-no time zone is determinable.
-
-@item %Ec %EC %Ex %EX %Ey %EY %Od %Oe %OH
-@itemx %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy
-``Alternative representations'' for the specifications
-that use only the second letter (@samp{%c}, @samp{%C},
-and so on).@footnote{If you don't understand any of this, don't worry about
-it; these facilities are meant to make it easier to ``internationalize''
-programs.
-Other internationalization features are described in
-@ref{Internationalization}.}
-(These facilitate compliance with the POSIX @command{date} utility.)
-
-@item %%
-A literal @samp{%}.
-@end table
-
-If a conversion specifier is not one of those just listed, the behavior is
-undefined.@footnote{This is because ISO C leaves the
-behavior of the C version of @code{strftime()} undefined and @command{gawk}
-uses the system's version of @code{strftime()} if it's there.
-Typically, the conversion specifier either does not appear in the
-returned string or appears literally.}
-
-For systems that are not yet fully standards-compliant,
-@command{gawk} supplies a copy of
-@code{strftime()} from the GNU C Library.
-It supports all of the just-listed format specifications.
-If that version is
-used to compile @command{gawk} (@pxref{Installation}),
-then the following additional format specifications are available:
-
-@table @code
-@item %k
-The hour (24-hour clock) as a decimal number (0--23).
-Single-digit numbers are padded with a space.
-
-@item %l
-The hour (12-hour clock) as a decimal number (1--12).
-Single-digit numbers are padded with a space.
-
-@ignore
-@item %N
-The ``Emperor/Era'' name.
-Equivalent to @samp{%C}.
-
-@item %o
-The ``Emperor/Era'' year.
-Equivalent to @samp{%y}.
-@end ignore
-
-@item %s
-The time as a decimal timestamp in seconds since the epoch.
-
-@ignore
-@item %v
-The date in OpenVMS format (e.g., @samp{20-JUN-1991}).
-@end ignore
-@end table
-
-Additionally, the alternative representations are recognized but their
-normal representations are used.
-
-@cindex @code{date} utility @subentry POSIX
-@cindex POSIX @command{awk} @subentry @code{date} utility and
-The following example is an @command{awk} implementation of the POSIX
-@command{date} utility. Normally, the @command{date} utility prints the
-current date and time of day in a well-known format. However, if you
-provide an argument to it that begins with a @samp{+}, @command{date}
-copies nonformat specifier characters to the standard output and
-interprets the current time according to the format specifiers in
-the string. For example:
-
-@example
-$ @kbd{date '+Today is %A, %B %d, %Y.'}
-@print{} Today is Monday, September 22, 2014.
-@end example
-
-Here is the @command{gawk} version of the @command{date} utility.
-It has a shell ``wrapper'' to handle the @option{-u} option,
-which requires that @command{date} run as if the time zone
-is set to UTC:
-
-@example
-#! /bin/sh
-#
-# date --- approximate the POSIX 'date' command
-
-case $1 in
--u) TZ=UTC0 # use UTC
- export TZ
- shift ;;
-esac
-
-gawk 'BEGIN @{
- format = PROCINFO["strftime"]
- exitval = 0
-
- if (ARGC > 2)
- exitval = 1
- else if (ARGC == 2) @{
- format = ARGV[1]
- if (format ~ /^\+/)
- format = substr(format, 2) # remove leading +
- @}
- print strftime(format)
- exit exitval
-@}' "$@@"
-@end example
-
-@node Bitwise Functions
-@subsection Bit-Manipulation Functions
-@cindex bit-manipulation functions
-@cindex bitwise @subentry operations
-@cindex AND bitwise operation
-@cindex OR bitwise operation
-@cindex XOR bitwise operation
-@cindex operations, bitwise
-@quotation
-@i{I can explain it for you, but I can't understand it for you.}
-@author Anonymous
-@end quotation
-
-Many languages provide the ability to perform @dfn{bitwise} operations
-on two integer numbers. In other words, the operation is performed on
-each successive pair of bits in the operands.
-Three common operations are bitwise AND, OR, and XOR.
-The operations are described in @ref{table-bitwise-ops}.
-
-@c 11/2014: Postprocessing turns the docbook informaltable
-@c into a table. Hurray for scripting!
-@float Table,table-bitwise-ops
-@caption{Bitwise operations}
-@ifnottex
-@ifnotdocbook
-@verbatim
- Bit operator
- | AND | OR | XOR
- |---+---+---+---+---+---
-Operands | 0 | 1 | 0 | 1 | 0 | 1
-----------+---+---+---+---+---+---
- 0 | 0 0 | 0 1 | 0 1
- 1 | 0 1 | 1 1 | 1 0
-@end verbatim
-@end ifnotdocbook
-@end ifnottex
-@tex
-\centerline{
-\vbox{\bigskip % space above the table (about 1 linespace)
-% Because we have vertical rules, we can't let TeX insert interline space
-% in its usual way.
-\offinterlineskip
-\halign{\strut\hfil#\quad\hfil % operands
- &\vrule#&\quad#\quad % rule, 0 (of and)
- &\vrule#&\quad#\quad % rule, 1 (of and)
- &\vrule# % rule between and and or
- &\quad#\quad % 0 (of or)
- &\vrule#&\quad#\quad % rule, 1 (of of)
- &\vrule# % rule between or and xor
- &\quad#\quad % 0 of xor
- &\vrule#&\quad#\quad % rule, 1 of xor
- \cr
-&\omit&\multispan{11}\hfil\bf Bit operator\hfil\cr
-\noalign{\smallskip}
-& &\multispan3\hfil AND\hfil&&\multispan3\hfil OR\hfil
- &&\multispan3\hfil XOR\hfil\cr
-\bf Operands&&0&&1&&0&&1&&0&&1\cr
-\noalign{\hrule}
-\omit&height 2pt&&\omit&&&&\omit&&&&\omit\cr
-\noalign{\hrule height0pt}% without this the rule does not extend; why?
-0&&0&\omit&0&&0&\omit&1&&0&\omit&1\cr
-1&&0&\omit&1&&1&\omit&1&&1&\omit&0\cr
-}}}
-@end tex
-
-@docbook
-<informaltable>
-
-<tgroup cols="7" colsep="1">
-<colspec colname="c1"/>
-<colspec colname="c2"/>
-<colspec colname="c3"/>
-<colspec colname="c4"/>
-<colspec colname="c5"/>
-<colspec colname="c6"/>
-<colspec colname="c7"/>
-<spanspec spanname="optitle" namest="c2" nameend="c7" align="center"/>
-<spanspec spanname="andspan" namest="c2" nameend="c3" align="center"/>
-<spanspec spanname="orspan" namest="c4" nameend="c5" align="center"/>
-<spanspec spanname="xorspan" namest="c6" nameend="c7" align="center"/>
-
-<tbody>
-<row>
-<entry colsep="0"></entry>
-<entry spanname="optitle"><emphasis role="bold">Bit operator</emphasis></entry>
-</row>
-
-<row rowsep="1">
-<entry rowsep="0"></entry>
-<entry spanname="andspan">AND</entry>
-<entry spanname="orspan">OR</entry>
-<entry spanname="xorspan">XOR</entry>
-</row>
-
-<row rowsep="1">
-<entry ><emphasis role="bold">Operands</emphasis></entry>
-<entry colsep="0">0</entry>
-<entry colsep="1">1</entry>
-<entry colsep="0">0</entry>
-<entry colsep="1">1</entry>
-<entry colsep="0">0</entry>
-<entry colsep="1">1</entry>
-</row>
-
-<row>
-<entry align="center">0</entry>
-<entry colsep="0">0</entry>
-<entry>0</entry>
-<entry colsep="0">0</entry>
-<entry>1</entry>
-<entry colsep="0">0</entry>
-<entry>1</entry>
-</row>
-
-<row>
-<entry align="center">1</entry>
-<entry colsep="0">0</entry>
-<entry>1</entry>
-<entry colsep="0">1</entry>
-<entry>1</entry>
-<entry colsep="0">1</entry>
-<entry>0</entry>
-</row>
-
-</tbody>
-</tgroup>
-</informaltable>
-@end docbook
-@end float
-
-@cindex bitwise @subentry complement
-@cindex complement, bitwise
-As you can see, the result of an AND operation is 1 only when @emph{both}
-bits are 1.
-The result of an OR operation is 1 if @emph{either} bit is 1.
-The result of an XOR operation is 1 if either bit is 1,
-but not both.
-The next operation is the @dfn{complement}; the complement of 1 is 0 and
-the complement of 0 is 1. Thus, this operation ``flips'' all the bits
-of a given value.
-
-@cindex bitwise @subentry shift
-@cindex left shift, bitwise
-@cindex right shift, bitwise
-@cindex shift, bitwise
-Finally, two other common operations are to shift the bits left or right.
-For example, if you have a bit string @samp{10111001} and you shift it
-right by three bits, you end up with @samp{00010111}.@footnote{This example
-shows that zeros come in on the left side. For @command{gawk}, this is
-always true, but in some languages, it's possible to have the left side
-fill with ones.}
-If you start over again with @samp{10111001} and shift it left by three
-bits, you end up with @samp{11001000}. The following list describes
-@command{gawk}'s built-in functions that implement the bitwise operations.
-Optional parameters are enclosed in square brackets ([ ]):
-
-@cindex @command{gawk} @subentry bitwise operations in
-@table @asis
-@cindexgawkfunc{and}
-@cindex bitwise @subentry AND
-@item @code{and(}@var{v1}@code{,} @var{v2} [@code{,} @dots{}]@code{)}
-Return the bitwise AND of the arguments. There must be at least two.
-
-@cindexgawkfunc{compl}
-@cindex bitwise @subentry complement
-@item @code{compl(@var{val})}
-Return the bitwise complement of @var{val}.
-
-@cindexgawkfunc{lshift}
-@item @code{lshift(@var{val}, @var{count})}
-Return the value of @var{val}, shifted left by @var{count} bits.
-
-@cindexgawkfunc{or}
-@cindex bitwise @subentry OR
-@item @code{or(}@var{v1}@code{,} @var{v2} [@code{,} @dots{}]@code{)}
-Return the bitwise OR of the arguments. There must be at least two.
-
-@cindexgawkfunc{rshift}
-@item @code{rshift(@var{val}, @var{count})}
-Return the value of @var{val}, shifted right by @var{count} bits.
-
-@cindexgawkfunc{xor}
-@cindex bitwise @subentry XOR
-@item @code{xor(}@var{v1}@code{,} @var{v2} [@code{,} @dots{}]@code{)}
-Return the bitwise XOR of the arguments. There must be at least two.
-@end table
-
-@quotation CAUTION
-Beginning with @command{gawk} @value{PVERSION} 4.2, negative
-operands are not allowed for any of these functions. A negative
-operand produces a fatal error. See the sidebar
-``Beware The Smoke and Mirrors!'' for more information as to why.
-@end quotation
-
-Here is a user-defined function (@pxref{User-defined})
-that illustrates the use of these functions:
-
-@cindex @code{bits2str()} user-defined function
-@cindex user-defined @subentry function @subentry @code{bits2str()}
-@cindex @file{testbits.awk} program
-@example
-@group
-@c file eg/lib/bits2str.awk
-# bits2str --- turn an integer into readable ones and zeros
-
-function bits2str(bits, data, mask)
-@{
- if (bits == 0)
- return "0"
-
- mask = 1
- for (; bits != 0; bits = rshift(bits, 1))
- data = (and(bits, mask) ? "1" : "0") data
-
- while ((length(data) % 8) != 0)
- data = "0" data
-
- return data
-@}
-@c endfile
-@end group
-
-@c this is a hack to make testbits.awk self-contained
-@ignore
-@c file eg/prog/testbits.awk
-# bits2str --- turn an integer into readable ones and zeros
-
-function bits2str(bits, data, mask)
-@{
- if (bits == 0)
- return "0"
-
- mask = 1
- for (; bits != 0; bits = rshift(bits, 1))
- data = (and(bits, mask) ? "1" : "0") data
-
- while ((length(data) % 8) != 0)
- data = "0" data
-
- return data
-@}
-@c endfile
-@end ignore
-@c file eg/prog/testbits.awk
-BEGIN @{
- printf "123 = %s\n", bits2str(123)
- printf "0123 = %s\n", bits2str(0123)
- printf "0x99 = %s\n", bits2str(0x99)
- comp = compl(0x99)
- printf "compl(0x99) = %#x = %s\n", comp, bits2str(comp)
- shift = lshift(0x99, 2)
- printf "lshift(0x99, 2) = %#x = %s\n", shift, bits2str(shift)
- shift = rshift(0x99, 2)
- printf "rshift(0x99, 2) = %#x = %s\n", shift, bits2str(shift)
-@}
-@c endfile
-@end example
-
-@noindent
-This program produces the following output when run:
-
-@example
-$ @kbd{gawk -f testbits.awk}
-@print{} 123 = 01111011
-@print{} 0123 = 01010011
-@print{} 0x99 = 10011001
-@print{} compl(0x99) = 0x3fffffffffff66 =
-@print{} 00111111111111111111111111111111111111111111111101100110
-@print{} lshift(0x99, 2) = 0x264 = 0000001001100100
-@print{} rshift(0x99, 2) = 0x26 = 00100110
-@end example
-
-@cindex converting @subentry string to numbers
-@cindex strings @subentry converting
-@cindex numbers @subentry converting
-@cindex converting @subentry numbers to strings
-@cindex numbers @subentry as string of bits
-The @code{bits2str()} function turns a binary number into a string.
-Initializing @code{mask} to one creates
-a binary value where the rightmost bit
-is set to one. Using this mask,
-the function repeatedly checks the rightmost bit.
-ANDing the mask with the value indicates whether the
-rightmost bit is one or not. If so, a @code{"1"} is concatenated onto the front
-of the string.
-Otherwise, a @code{"0"} is added.
-The value is then shifted right by one bit and the loop continues
-until there are no more one bits.
-
-If the initial value is zero, it returns a simple @code{"0"}.
-Otherwise, at the end, it pads the value with zeros to represent multiples
-of 8-bit quantities. This is typical in modern computers.
-
-The main code in the @code{BEGIN} rule shows the difference between the
-decimal and octal values for the same numbers
-(@pxref{Nondecimal-numbers}),
-and then demonstrates the
-results of the @code{compl()}, @code{lshift()}, and @code{rshift()} functions.
-
-@sidebar Beware The Smoke and Mirrors!
-
-It other languages, bitwise operations are performed on integer values,
-not floating-point values. As a general statement, such operations work
-best when performed on unsigned integers.
-
-@command{gawk} attempts to treat the arguments to the bitwise functions
-as unsigned integers. For this reason, negative arguments produce a
-fatal error.
-
-In normal operation, for all of these functions, first the
-double-precision floating-point value is converted to the widest C
-unsigned integer type, then the bitwise operation is performed. If the
-result cannot be represented exactly as a C @code{double}, leading
-nonzero bits are removed one by one until it can be represented exactly.
-The result is then converted back into a C @code{double}.@footnote{If you don't
-understand this paragraph, the upshot is that @command{gawk} can only
-store a particular range of integer values; numbers outside that range
-are reduced to fit within the range.}
-
-However, when using arbitrary precision arithmetic with the @option{-M}
-option (@pxref{Arbitrary Precision Arithmetic}), the results may differ.
-This is particularly noticeable with the @code{compl()} function:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print compl(42) @}'}
-@print{} 9007199254740949
-$ @kbd{gawk -M 'BEGIN @{ print compl(42) @}'}
-@print{} -43
-@end example
-
-What's going on becomes clear when printing the results
-in hexadecimal:
-
-@example
-$ @kbd{gawk 'BEGIN @{ printf "%#x\n", compl(42) @}'}
-@print{} 0x1fffffffffffd5
-$ @kbd{gawk -M 'BEGIN @{ printf "%#x\n", compl(42) @}'}
-@print{} 0xffffffffffffffd5
-@end example
-
-When using the @option{-M} option, under the hood, @command{gawk} uses
-GNU MP arbitrary precision integers which have at least 64 bits of precision.
-When not using @option{-M}, @command{gawk} stores integral values in
-regular double-precision floating point, which only maintain 53 bits of
-precision. Furthermore, the GNU MP library treats (or at least seems to treat)
-the leading bit as a sign bit; thus the result with @option{-M} in this case is
-a negative number.
-
-In short, using @command{gawk} for any but the simplest kind of bitwise
-operations is probably a bad idea; caveat emptor!
-
-@end sidebar
-
-@node Type Functions
-@subsection Getting Type Information
-
-@command{gawk} provides two functions that let you distinguish
-the type of a variable.
-This is necessary for writing code
-that traverses every element of an array of arrays
-(@pxref{Arrays of Arrays}), and in other contexts.
-
-@table @code
-@cindexgawkfunc{isarray}
-@cindex scalar or array
-@item isarray(@var{x})
-Return a true value if @var{x} is an array. Otherwise, return false.
-
-@cindexgawkfunc{typeof}
-@cindex variable type, @code{typeof()} function (@command{gawk})
-@cindex type @subentry of variable, @code{typeof()} function (@command{gawk})
-@item typeof(@var{x})
-Return one of the following strings, depending upon the type of @var{x}:
-
-@c nested table
-@table @code
-@item "array"
-@var{x} is an array.
-
-@item "regexp"
-@var{x} is a strongly typed regexp (@pxref{Strong Regexp Constants}).
-
-@item "number"
-@var{x} is a number.
-
-@item "number|bool"
-@var{x} is a Boolean typed value (@pxref{Boolean Typed Values}).
-
-@item "string"
-@var{x} is a string.
-
-@item "strnum"
-@var{x} is a number that started life as user input, such as a field or
-the result of calling @code{split()}. (I.e., @var{x} has the strnum
-attribute; @pxref{Variable Typing}.)
-
-@item "unassigned"
-@var{x} is a scalar variable that has not been assigned a value yet.
-For example:
-
-@example
-BEGIN @{
- # creates a[1] but it has no assigned value
- a[1]
- print typeof(a[1]) # unassigned
-@}
-@end example
-
-@item "untyped"
-@var{x} has not yet been used yet at all; it can become a scalar or an
-array. The typing could even conceivably differ from run to run of
-the same program! For example:
-
-@example
-BEGIN @{
- print "initially, typeof(v) = ", typeof(v)
-
- if ("FOO" in ENVIRON)
- make_scalar(v)
- else
- make_array(v)
-
- print "typeof(v) =", typeof(v)
-@}
-
-function make_scalar(p, l) @{ l = p @}
-
-function make_array(p) @{ p[1] = 1 @}
-@end example
-
-@end table
-@end table
-
-@code{isarray()} is meant for use in two circumstances. The first is when
-traversing a multidimensional array: you can test if an element is itself
-an array or not. The second is inside the body of a user-defined function
-(not discussed yet; @pxref{User-defined}), to test if a parameter is an
-array or not.
-
-@quotation NOTE
-While you can use @code{isarray()} at the global level to test variables,
-doing so makes no sense. Because @emph{you} are the one writing the
-program, @emph{you} are supposed to know if your variables are arrays
-or not.
-@end quotation
-
-The @code{typeof()} function is general; it allows you to determine
-if a variable or function parameter is a scalar (number, string,
-or strongly typed regexp) or an array.
-
-Normally, passing a variable that has never been used to a built-in
-function causes it to become a scalar variable (unassigned).
-However, @code{isarray()} and @code{typeof()} are different; they do
-not change their arguments from untyped to unassigned.
-
-This applies to both variables denoted by simple identifiers
-and array elements that come into existence simply by referencing them.
-Consider:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print typeof(x) @}'}
-@print{} untyped
-$ @kbd{gawk 'BEGIN @{ print typeof(x["foo"]) @}'}
-@print{} untyped
-@end example
-
-Note that prior to @value{PVERSION} 5.2, array elements
-that come into existence simply by referencing them
-were different, they were automatically forced to be scalars:
-
-@example
-$ @kbd{gawk-5.1.1 'BEGIN @{ print typeof(x) @}'}
-@print{} untyped
-$ @kbd{gawk-5.1.1 'BEGIN @{ print typeof(x["foo"]) @}'}
-@print{} unassigned
-@end example
-
-@node I18N Functions
-@subsection String-Translation Functions
-@cindex @command{gawk} @subentry string-translation functions
-@cindex functions @subentry string-translation
-@cindex string-translation functions
-@cindex internationalization
-@cindex @command{awk} programs @subentry internationalizing
-
-@command{gawk} provides facilities for internationalizing @command{awk}
programs.
-These include the functions described in the following list.
-The descriptions here are purposely brief.
-@xref{Internationalization},
-for the full story.
-Optional parameters are enclosed in square brackets ([ ]):
-
-@table @asis
-@cindexgawkfunc{bindtextdomain}
-@cindex set directory of message catalogs
-@item @code{bindtextdomain(@var{directory}} [@code{,} @var{domain}]@code{)}
-Set the directory in which
-@command{gawk} will look for message translation files, in case they
-will not or cannot be placed in the ``standard'' locations
-(e.g., during testing).
-It returns the directory in which @var{domain} is ``bound.''
-
-The default @var{domain} is the value of @code{TEXTDOMAIN}.
-If @var{directory} is the null string (@code{""}), then
-@code{bindtextdomain()} returns the current binding for the
-given @var{domain}.
-
-@cindexgawkfunc{dcgettext}
-@cindex translate string
-@item @code{dcgettext(@var{string}} [@code{,} @var{domain} [@code{,}
@var{category}] ]@code{)}
-Return the translation of @var{string} in
-text domain @var{domain} for locale category @var{category}.
-The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
-The default value for @var{category} is @code{"LC_MESSAGES"}.
-
-@cindexgawkfunc{dcngettext}
-@item @code{dcngettext(@var{string1}, @var{string2}, @var{number}} [@code{,}
@var{domain} [@code{,} @var{category}] ]@code{)}
-Return the plural form used for @var{number} of the
-translation of @var{string1} and @var{string2} in text domain
-@var{domain} for locale category @var{category}. @var{string1} is the
-English singular variant of a message, and @var{string2} is the English plural
-variant of the same message.
-The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
-The default value for @var{category} is @code{"LC_MESSAGES"}.
-@end table
-
-@node User-defined
-@section User-Defined Functions
-
-@cindex user-defined @subentry functions
-@cindex functions @subentry user-defined
-Complicated @command{awk} programs can often be simplified by defining
-your own functions. User-defined functions can be called just like
-built-in ones (@pxref{Function Calls}), but it is up to you to define
-them (i.e., to tell @command{awk} what they should do).
-
-@menu
-* Definition Syntax:: How to write definitions and what they mean.
-* Function Example:: An example function definition and what it
- does.
-* Function Calling:: Calling user-defined functions.
-* Return Statement:: Specifying the value a function returns.
-* Dynamic Typing:: How variable types can change at runtime.
-@end menu
-
-@node Definition Syntax
-@subsection Function Definition Syntax
-
-@quotation
-@i{It's entirely fair to say that the awk syntax for local
-variable definitions is appallingly awful.}
-@author Brian Kernighan
-@end quotation
-
-@cindex functions @subentry defining
-Definitions of functions can appear anywhere between the rules of an
-@command{awk} program. Thus, the general form of an @command{awk} program is
-extended to include sequences of rules @emph{and} user-defined function
-definitions.
-There is no need to put the definition of a function
-before all uses of the function. This is because @command{awk} reads the
-entire program before starting to execute any of it.
-
-The definition of a function named @var{name} looks like this:
-
-@display
-@group
-@code{function} @var{name}@code{(}[@var{parameter-list}]@code{)}
-@code{@{}
- @var{body-of-function}
-@code{@}}
-@end group
-@end display
-
-@cindex names @subentry functions
-@cindex functions @subentry names of
-@cindex naming issues @subentry functions
-@noindent
-Here, @var{name} is the name of the function to define. A valid function
-name is like a valid variable name: a sequence of letters, digits, and
-underscores that doesn't start with a digit.
-Here too, only the 52 upper- and lowercase English letters may
-be used in a function name.
-Within a single @command{awk} program, any particular name can only be
-used as a variable, array, or function.
-
-@var{parameter-list} is an optional list of the function's arguments and local
-variable names, separated by commas. When the function is called,
-the argument names are used to hold the argument values given in
-the call.
-
-A function cannot have two parameters with the same name, nor may it
-have a parameter with the same name as the function itself.
-
-@quotation CAUTION
-According to the POSIX standard, function parameters
-cannot have the same name as one of the special predefined variables
-(@pxref{Built-in Variables}), nor may a function parameter have the
-same name as another function.
-
-@cindex dark corner @subentry parameter name restrictions
-Not all versions of @command{awk} enforce
-these restrictions. @value{DARKCORNER}
-@command{gawk} always enforces the first restriction.
-With @option{--posix} (@pxref{Options}),
-it also enforces the second restriction.
-@end quotation
-
-Local variables act like the empty string if referenced where a string
-value is required, and like zero if referenced where a numeric value
-is required. This is the same as the behavior of regular variables that have
never been
-assigned a value. (There is more to understand about local variables;
-@pxref{Dynamic Typing}.)
-
-The @var{body-of-function} consists of @command{awk} statements. It is the
-most important part of the definition, because it says what the function
-should actually @emph{do}. The argument names exist to give the body a
-way to talk about the arguments; local variables exist to give the body
-places to keep temporary values.
-
-Argument names are not distinguished syntactically from local variable
-names. Instead, the number of arguments supplied when the function is
-called determines how many argument variables there are. Thus, if three
-argument values are given, the first three names in @var{parameter-list}
-are arguments and the rest are local variables.
-
-It follows that if the number of arguments is not the same in all calls
-to the function, some of the names in @var{parameter-list} may be
-arguments on some occasions and local variables on others. Another
-way to think of this is that omitted arguments default to the
-null string.
-
-@cindex programming conventions @subentry functions @subentry writing
-Usually when you write a function, you know how many names you intend to
-use for arguments and how many you intend to use as local variables. It is
-conventional to place some extra space between the arguments and
-the local variables, in order to document how your function is supposed to be
used.
-
-@cindex variables @subentry shadowing
-@cindex shadowing of variable values
-During execution of the function body, the arguments and local variable
-values hide, or @dfn{shadow}, any variables of the same names used in the
-rest of the program. The shadowed variables are not accessible in the
-function definition, because there is no way to name them while their
-names have been taken away for the arguments and local variables. All other
variables
-used in the @command{awk} program can be referenced or set normally in the
-function's body.
-
-The arguments and local variables last only as long as the function body
-is executing. Once the body finishes, you can once again access the
-variables that were shadowed while the function was running.
-
-@cindex recursive functions
-@cindex functions @subentry recursive
-The function body can contain expressions that call functions. They
-can even call this function, either directly or by way of another
-function. When this happens, we say the function is @dfn{recursive}.
-The act of a function calling itself is called @dfn{recursion}.
-
-All the built-in functions return a value to their caller.
-User-defined functions can do so also, using the @code{return} statement,
-which is described in detail in @ref{Return Statement}.
-Many of the subsequent examples in this @value{SECTION} use
-the @code{return} statement.
-
-@cindex common extensions @subentry @code{func} keyword
-@cindex extensions @subentry common @subentry @code{func} keyword
-@c @cindex POSIX @command{awk}
-@cindex @command{awk} @subentry language, POSIX version
-@cindex POSIX @command{awk} @subentry @code{function} keyword in
-In many @command{awk} implementations, including @command{gawk},
-the keyword @code{function} may be
-abbreviated @code{func}. @value{COMMONEXT}
-However, POSIX only specifies the use of
-the keyword @code{function}. This actually has some practical implications.
-If @command{gawk} is in POSIX-compatibility mode
-(@pxref{Options}), then the following
-statement does @emph{not} define a function:
-
-@example
-func foo() @{ a = sqrt($1) ; print a @}
-@end example
-
-@noindent
-Instead, it defines a rule that, for each record, concatenates the value
-of the variable @samp{func} with the return value of the function @samp{foo}.
-If the resulting string is non-null, the action is executed.
-This is probably not what is desired. (@command{awk} accepts this input as
-syntactically valid, because functions may be used before they are defined
-in @command{awk} programs.@footnote{This program won't actually run,
-because @code{foo()} is undefined.})
-
-@cindex portability @subentry functions, defining
-To ensure that your @command{awk} programs are portable, always use the
-keyword @code{function} when defining a function.
-
-@node Function Example
-@subsection Function Definition Examples
-@cindex function definition example
-
-Here is an example of a user-defined function, called @code{myprint()}, that
-takes a number and prints it in a specific format:
-
-@example
-function myprint(num)
-@{
- printf "%6.3g\n", num
-@}
-@end example
-
-@noindent
-To illustrate, here is an @command{awk} rule that uses our @code{myprint()}
-function:
-
-@example
-$3 > 0 @{ myprint($3) @}
-@end example
-
-@noindent
-This program prints, in our special format, all the third fields that
-contain a positive number in our input. Therefore, when given the following
input:
-
-@example
- 1.2 3.4 5.6 7.8
- 9.10 11.12 -13.14 15.16
-17.18 19.20 21.22 23.24
-@end example
-
-@noindent
-this program, using our function to format the results, prints:
-
-@example
- 5.6
- 21.2
-@end example
-
-This function deletes all the elements in an array (recall that the
-extra whitespace signifies the start of the local variable list):
-
-@example
-@group
-function delarray(a, i)
-@{
- for (i in a)
- delete a[i]
-@}
-@end group
-@end example
-
-When working with arrays, it is often necessary to delete all the elements
-in an array and start over with a new list of elements
-(@pxref{Delete}).
-Instead of having
-to repeat this loop everywhere that you need to clear out
-an array, your program can just call @code{delarray()}.
-(This guarantees portability. The use of @samp{delete @var{array}} to delete
-the contents of an entire array is a relatively recent@footnote{Late in 2012.}
-addition to the POSIX standard.)
-
-The following is an example of a recursive function. It takes a string
-as an input parameter and returns the string in reverse order.
-Recursive functions must always have a test that stops the recursion.
-In this case, the recursion terminates when the input string is
-already empty:
-
-@c 8/2014: Thanks to Mike Brennan for the improved formulation
-@cindex @code{rev()} user-defined function
-@cindex user-defined @subentry function @subentry @code{rev()}
-@example
-function rev(str)
-@{
- if (str == "")
- return ""
-
- return (rev(substr(str, 2)) substr(str, 1, 1))
-@}
-@end example
-
-If this function is in a file named @file{rev.awk}, it can be tested
-this way:
-
-@example
-$ @kbd{echo "Don't Panic!" |}
-> @kbd{gawk -e '@{ print rev($0) @}' -f rev.awk}
-@print{} !cinaP t'noD
-@end example
-
-The C @code{ctime()} function takes a timestamp and returns it as a string,
-formatted in a well-known fashion.
-The following example uses the built-in @code{strftime()} function
-(@pxref{Time Functions})
-to create an @command{awk} version of @code{ctime()}:
-
-@cindex @code{ctime()} user-defined function
-@cindex user-defined @subentry function @subentry @code{ctime()}
-@example
-@c file eg/lib/ctime.awk
-# ctime.awk
-#
-# awk version of C ctime(3) function
-
-function ctime(ts, format)
-@{
- format = "%a %b %e %H:%M:%S %Z %Y"
-
- if (ts == 0)
- ts = systime() # use current time as default
- return strftime(format, ts)
-@}
-@c endfile
-@end example
-
-You might think that @code{ctime()} could use @code{PROCINFO["strftime"]}
-for its format string. That would be a mistake, because @code{ctime()} is
-supposed to return the time formatted in a standard fashion, and user-level
-code could have changed @code{PROCINFO["strftime"]}.
-
-@node Function Calling
-@subsection Calling User-Defined Functions
-
-@cindex functions @subentry user-defined @subentry calling
-@dfn{Calling a function} means causing the function to run and do its job.
-A function call is an expression and its value is the value returned by
-the function.
-
-@menu
-* Calling A Function:: Don't use spaces.
-* Variable Scope:: Controlling variable scope.
-* Pass By Value/Reference:: Passing parameters.
-* Function Caveats:: Other points to know about functions.
-@end menu
-
-@node Calling A Function
-@subsubsection Writing a Function Call
-
-A function call consists of the function name followed by the arguments
-in parentheses. @command{awk} expressions are what you write in the
-call for the arguments. Each time the call is executed, these
-expressions are evaluated, and the values become the actual arguments. For
-example, here is a call to @code{foo()} with three arguments (the first
-being a string concatenation):
-
-@example
-foo(x y, "lose", 4 * z)
-@end example
-
-@quotation CAUTION
-Whitespace characters (spaces and TABs) are not allowed
-between the function name and the opening parenthesis of the argument list.
-If you write whitespace by mistake, @command{awk} might think that you mean
-to concatenate a variable with an expression in parentheses. However, it
-notices that you used a function name and not a variable name, and reports
-an error.
-@end quotation
-
-@node Variable Scope
-@subsubsection Controlling Variable Scope
-
-@cindex local variables @subentry in a function
-@cindex variables @subentry local to a function
-Unlike in many languages,
-there is no way to make a variable local to a @code{@{} @dots{} @code{@}}
block in
-@command{awk}, but you can make a variable local to a function. It is
-good practice to do so whenever a variable is needed only in that
-function.
-
-To make a variable local to a function, simply declare the variable as
-an argument after the actual function arguments
-(@pxref{Definition Syntax}).
-Look at the following example, where variable
-@code{i} is a global variable used by both functions @code{foo()} and
-@code{bar()}:
-
-@example
-function bar()
-@{
- for (i = 0; i < 3; i++)
- print "bar's i=" i
-@}
-
-function foo(j)
-@{
- i = j + 1
- print "foo's i=" i
- bar()
- print "foo's i=" i
-@}
-
-BEGIN @{
- i = 10
- print "top's i=" i
- foo(0)
- print "top's i=" i
-@}
-@end example
-
-Running this script produces the following, because the @code{i} in
-functions @code{foo()} and @code{bar()} and at the top level refer to the same
-variable instance:
-
-@example
-top's i=10
-foo's i=1
-bar's i=0
-bar's i=1
-bar's i=2
-foo's i=3
-top's i=3
-@end example
-
-If you want @code{i} to be local to both @code{foo()} and @code{bar()}, do as
-follows (the extra space before @code{i} is a coding convention to
-indicate that @code{i} is a local variable, not an argument):
-
-@example
-function bar( i)
-@{
- for (i = 0; i < 3; i++)
- print "bar's i=" i
-@}
-
-function foo(j, i)
-@{
- i = j + 1
- print "foo's i=" i
- bar()
- print "foo's i=" i
-@}
-
-BEGIN @{
- i = 10
- print "top's i=" i
- foo(0)
- print "top's i=" i
-@}
-@end example
-
-Running the corrected script produces the following:
-
-@example
-top's i=10
-foo's i=1
-bar's i=0
-bar's i=1
-bar's i=2
-foo's i=1
-top's i=10
-@end example
-
-Besides scalar values (strings and numbers), you may also have
-local arrays. By using a parameter name as an array, @command{awk}
-treats it as an array, and it is local to the function.
-In addition, recursive calls create new arrays.
-Consider this example:
-
-@example
-@group
-function some_func(p1, a)
-@{
- if (p1++ > 3)
- return
-@end group
-
- a[p1] = p1
-
- some_func(p1)
-
- printf("At level %d, index %d %s found in a\n",
- p1, (p1 - 1), (p1 - 1) in a ? "is" : "is not")
- printf("At level %d, index %d %s found in a\n",
- p1, p1, p1 in a ? "is" : "is not")
- print ""
-@}
-
-BEGIN @{
- some_func(1)
-@}
-@end example
-
-When run, this program produces the following output:
-
-@example
-At level 4, index 3 is not found in a
-At level 4, index 4 is found in a
-
-At level 3, index 2 is not found in a
-At level 3, index 3 is found in a
-
-At level 2, index 1 is not found in a
-At level 2, index 2 is found in a
-@end example
-
-@node Pass By Value/Reference
-@subsubsection Passing Function Arguments by Value Or by Reference
-
-In @command{awk}, when you declare a function, there is no way to
-declare explicitly whether the arguments are passed @dfn{by value} or
-@dfn{by reference}.
-
-Instead, the passing convention is determined at runtime when
-the function is called, according to the following rule:
-if the argument is an array variable, then it is passed by reference.
-Otherwise, the argument is passed by value.
-
-@cindex call by value
-Passing an argument by value means that when a function is called, it
-is given a @emph{copy} of the value of this argument.
-The caller may use a variable as the expression for the argument, but
-the called function does not know this---it only knows what value the
-argument had. For example, if you write the following code:
-
-@example
-foo = "bar"
-z = myfunc(foo)
-@end example
-
-@noindent
-then you should not think of the argument to @code{myfunc()} as being
-``the variable @code{foo}.'' Instead, think of the argument as the
-string value @code{"bar"}.
-If the function @code{myfunc()} alters the values of its local variables,
-this has no effect on any other variables. Thus, if @code{myfunc()}
-does this:
-
-@example
-@group
-function myfunc(str)
-@{
- print str
- str = "zzz"
- print str
-@}
-@end group
-@end example
-
-@noindent
-to change its first argument variable @code{str}, it does @emph{not}
-change the value of @code{foo} in the caller. The role of @code{foo} in
-calling @code{myfunc()} ended when its value (@code{"bar"}) was computed.
-If @code{str} also exists outside of @code{myfunc()}, the function body
-cannot alter this outer value, because it is shadowed during the
-execution of @code{myfunc()} and cannot be seen or changed from there.
-
-@cindex call by reference
-@cindex arrays @subentry as parameters to functions
-@cindex functions @subentry arrays as parameters to
-However, when arrays are the parameters to functions, they are @emph{not}
-copied. Instead, the array itself is made available for direct manipulation
-by the function. This is usually termed @dfn{call by reference}.
-Changes made to an array parameter inside the body of a function @emph{are}
-visible outside that function.
-
-@quotation NOTE
-Changing an array parameter inside a function
-can be very dangerous if you do not watch what you are doing.
-For example:
-
-@example
-function changeit(array, ind, nvalue)
-@{
- array[ind] = nvalue
-@}
-
-BEGIN @{
- a[1] = 1; a[2] = 2; a[3] = 3
- changeit(a, 2, "two")
- printf "a[1] = %s, a[2] = %s, a[3] = %s\n",
- a[1], a[2], a[3]
-@}
-@end example
-
-@noindent
-prints @samp{a[1] = 1, a[2] = two, a[3] = 3}, because
-@code{changeit()} stores @code{"two"} in the second element of @code{a}.
-@end quotation
-
-@node Function Caveats
-@subsubsection Other Points About Calling Functions
-
-@cindex undefined functions
-@cindex functions @subentry undefined
-Some @command{awk} implementations allow you to call a function that
-has not been defined. They only report a problem at runtime, when the
-program actually tries to call the function. For example:
-
-@example
-BEGIN @{
- if (0)
- foo()
- else
- bar()
-@}
-function bar() @{ @dots{} @}
-# note that `foo' is not defined
-@end example
-
-@noindent
-Because the @samp{if} statement will never be true, it is not really a
-problem that @code{foo()} has not been defined. Usually, though, it is a
-problem if a program calls an undefined function.
-
-@cindex lint checking @subentry undefined functions
-If @option{--lint} is specified
-(@pxref{Options}),
-@command{gawk} reports calls to undefined functions.
-
-@cindex portability @subentry @code{next} statement in user-defined functions
-Some @command{awk} implementations generate a runtime
-error if you use either the @code{next} statement
-or the @code{nextfile} statement
-(@pxref{Next Statement}, and
-@ifdocbook
-@ref{Nextfile Statement})
-@end ifdocbook
-@ifnotdocbook
-@pxref{Nextfile Statement})
-@end ifnotdocbook
-inside a user-defined function.
-@command{gawk} does not have this limitation.
-
-You can call a function and pass it more parameters than it was declared
-with, like so:
-
-@example
-function foo(p1, p2)
-@{
- @dots{}
-@}
-
-BEGIN @{
- foo(1, 2, 3, 4)
-@}
-@end example
-
-Doing so is bad practice, however. The called function cannot do
-anything with the additional values being passed to it, so @command{awk}
-evaluates the expressions but then just throws them away.
-
-More importantly, such a call is confusing for whoever will next read your
-program.@footnote{Said person might even be you, sometime in the future,
-at which point you will wonder, ``what was I thinking?!?''} Function
-parameters generally are input items that influence the computation
-performed by the function. Calling a function with more parameters than
-it accepts gives the false impression that those values are important
-to the function, when in fact they are not.
-
-Because this is such a bad practice, @command{gawk} @emph{unconditionally}
-issues a warning whenever it executes such a function call. (If you
-don't like the warning, fix your code! It's incorrect, after all.)
-
-@node Return Statement
-@subsection The @code{return} Statement
-@cindex @code{return} statement, user-defined functions
-
-As seen in several earlier examples,
-the body of a user-defined function can contain a @code{return} statement.
-This statement returns control to the calling part of the @command{awk}
program. It
-can also be used to return a value for use in the rest of the @command{awk}
-program. It looks like this:
-
-@display
-@code{return} [@var{expression}]
-@end display
-
-The @var{expression} part is optional.
-Due most likely to an oversight, POSIX does not define what the return
-value is if you omit the @var{expression}. Technically speaking, this
-makes the returned value undefined, and therefore, unpredictable.
-In practice, though, all versions of @command{awk} simply return the
-null string, which acts like zero if used in a numeric context.
-
-A @code{return} statement without an @var{expression} is assumed at the end of
-every function definition. So, if control reaches the end of the function
-body, then technically the function returns an unpredictable value.
-In practice, it returns the empty string. @command{awk}
-does @emph{not} warn you if you use the return value of such a function.
-
-Sometimes, you want to write a function for what it does, not for
-what it returns. Such a function corresponds to a @code{void} function
-in C, C++, or Java, or to a @code{procedure} in Ada. Thus, it may be
appropriate to not
-return any value; simply bear in mind that you should not be using the
-return value of such a function.
-
-The following is an example of a user-defined function that returns a value
-for the largest number among the elements of an array:
-
-@example
-function maxelt(vec, i, ret)
-@{
- for (i in vec) @{
- if (ret == "" || vec[i] > ret)
- ret = vec[i]
- @}
- return ret
-@}
-@end example
-
-@cindex programming conventions @subentry function parameters
-@noindent
-You call @code{maxelt()} with one argument, which is an array name. The local
-variables @code{i} and @code{ret} are not intended to be arguments;
-there is nothing to stop you from passing more than one argument
-to @code{maxelt()} but the results would be strange. The extra space before
-@code{i} in the function parameter list indicates that @code{i} and
-@code{ret} are local variables.
-You should follow this convention when defining functions.
-
-The following program uses the @code{maxelt()} function. It loads an
-array, calls @code{maxelt()}, and then reports the maximum number in that
-array:
-
-@example
-function maxelt(vec, i, ret)
-@{
- for (i in vec) @{
- if (ret == "" || vec[i] > ret)
- ret = vec[i]
- @}
- return ret
-@}
-
-@group
-# Load all fields of each record into nums.
-@{
- for(i = 1; i <= NF; i++)
- nums[NR, i] = $i
-@}
-@end group
-
-END @{
- print maxelt(nums)
-@}
-@end example
-
-Given the following input:
-
-@example
- 1 5 23 8 16
-44 3 5 2 8 26
-256 291 1396 2962 100
--6 467 998 1101
-99385 11 0 225
-@end example
-
-@noindent
-the program reports (predictably) that 99,385 is the largest value
-in the array.
-
-@node Dynamic Typing
-@subsection Functions and Their Effects on Variable Typing
-
-@cindex Saturday Night Live
-@quotation
-@i{It's a desert topping! @*
-It's a floor wax!}
-@author Saturday Night Live (back when it used to be funny)
-@end quotation
-
-@command{awk} is a very fluid language.
-It is possible that @command{awk} can't tell if an identifier
-represents a scalar variable or an array until runtime.
-Here is an annotated sample program:
-
-@example
-function foo(a)
-@{
- a[1] = 1 # parameter is an array
-@}
-
-BEGIN @{
- b = 1
- foo(b) # invalid: fatal type mismatch
-
- foo(x) # x uninitialized, becomes an array dynamically
- x = 1 # now not allowed, runtime error
-@}
-@end example
-
-In this example, the first call to @code{foo()} generates
-a fatal error, so @command{awk} will not report the second
-error. If you comment out that call, though, then @command{awk}
-does report the second error.
-
-Here is a more extreme example:
-
-@example
-BEGIN @{
- funky(a)
- if (A == 0)
- print "<" a ">"
- else
- print a[1]
-@}
-
-function funky(arr)
-@{
- if (A == 0)
- arr = 1
- else
- arr[1] = 1
-@}
-@end example
-
-Here, the function uses its parameter differently depending upon the
-value of the global variable @code{A}. If @code{A} is zero, the
-parameter @code{arr} is treated as a scalar. Otherwise it's treated
-as an array.
-
-There are two ways this program might behave. @command{awk} could notice
-that in the main program, @code{a} is subscripted, and so mark it as
-an array before the program even begins to run. BWK @code{awk}, @code{mawk},
-and possibly others do this:
-
-@example
-$ @kbd{nawk -v A=0 -f funky.awk}
-@error{} nawk: can't assign to a; it's an array name.
-@error{} source line number 11
-$ @kbd{nawk -v A=1 -f funky.awk}
-@print{} 1
-@end example
-
-Or @command{awk} could wait until runtime to set the type of @code{a}.
-In this case, since @code{a} was never used before being
-passed to the function, how the function uses it forces the type to
-be resolved to either scalar or array. @command{gawk}
-and the MKS @command{awk} do this:
-
-@example
-$ @kbd{gawk -v A=0 -f funky.awk}
-@print{} <>
-$ @kbd{gawk -v A=1 -f funky.awk }
-@print{} 1
-@end example
-
-POSIX does not specify the correct behavior, so be aware that different
-implementations work differently.
-
-@node Indirect Calls
-@section Indirect Function Calls
-
-@cindex indirect function calls
-@cindex function calls @subentry indirect
-@cindex function pointers
-@cindex pointers to functions
-@cindex differences in @command{awk} and @command{gawk} @subentry indirect
function calls
-
-This @value{SECTION} describes an advanced, @command{gawk}-specific extension.
-
-Often, you may wish to defer the choice of function to call until runtime.
-For example, you may have different kinds of records, each of which
-should be processed differently.
-
-Normally, you would have to use a series of @code{if}-@code{else}
-statements to decide which function to call. By using @dfn{indirect}
-function calls, you can specify the name of the function to call as a
-string variable, and then call the function. Let's look at an example.
-
-Suppose you have a file with your test scores for the classes you
-are taking, and
-you wish to get the sum and the average of
-your test scores.
-The first field is the class name. The following fields
-are the functions to call to process the data, up to a ``marker''
-field @samp{data:}. Following the marker, to the end of the record,
-are the various numeric test scores.
-
-Here is the initial file:
-
-@example
-@c file eg/data/class_data1
-Biology_101 sum average data: 87.0 92.4 78.5 94.9
-Chemistry_305 sum average data: 75.2 98.3 94.7 88.2
-English_401 sum average data: 100.0 95.6 87.1 93.4
-@c endfile
-@end example
-
-To process the data, you might write initially:
-
-@example
-@{
- class = $1
- for (i = 2; $i != "data:"; i++) @{
- if ($i == "sum")
- sum() # processes the whole record
- else if ($i == "average")
- average()
- @dots{} # and so on
- @}
-@}
-@end example
-
-@noindent
-This style of programming works, but can be awkward. With @dfn{indirect}
-function calls, you tell @command{gawk} to use the @emph{value} of a
-variable as the @emph{name} of the function to call.
-
-@cindex @code{@@} (at-sign) @subentry @code{@@}-notation for indirect function
calls
-@cindex at-sign (@code{@@}) @subentry @code{@@}-notation for indirect function
calls
-@cindex indirect function calls @subentry @code{@@}-notation
-@cindex function calls @subentry indirect @subentry @code{@@}-notation for
-The syntax is similar to that of a regular function call: an identifier
-immediately followed by an opening parenthesis, any arguments, and then
-a closing parenthesis, with the addition of a leading @samp{@@}
-character:
-
-@example
-the_function = "sum"
-result = @@the_function() # calls the sum() function
-@end example
-
-Here is a full program that processes the previously shown data,
-using indirect function calls:
-
-@example
-@c file eg/prog/indirectcall.awk
-# indirectcall.awk --- Demonstrate indirect function calls
-@c endfile
-@ignore
-@c file eg/prog/indirectcall.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# January 2009
-@c endfile
-@end ignore
-
-@c file eg/prog/indirectcall.awk
-# average --- return the average of the values in fields $first - $last
-
-function average(first, last, sum, i)
-@{
- sum = 0;
- for (i = first; i <= last; i++)
- sum += $i
-
- return sum / (last - first + 1)
-@}
-
-# sum --- return the sum of the values in fields $first - $last
-
-function sum(first, last, ret, i)
-@{
- ret = 0;
- for (i = first; i <= last; i++)
- ret += $i
-
- return ret
-@}
-@c endfile
-@end example
-
-These two functions expect to work on fields; thus, the parameters
-@code{first} and @code{last} indicate where in the fields to start and end.
-Otherwise, they perform the expected computations and are not unusual:
-
-@example
-@c file eg/prog/indirectcall.awk
-# For each record, print the class name and the requested statistics
-@{
- class_name = $1
- gsub(/_/, " ", class_name) # Replace _ with spaces
-
- # find start
- for (i = 1; i <= NF; i++) @{
- if ($i == "data:") @{
- start = i + 1
- break
- @}
- @}
-
- printf("%s:\n", class_name)
- for (i = 2; $i != "data:"; i++) @{
- the_function = $i
- printf("\t%s: <%s>\n", $i, @@the_function(start, NF) "")
- @}
- print ""
-@}
-@c endfile
-@end example
-
-This is the main processing for each record. It prints the class name (with
-underscores replaced with spaces). It then finds the start of the actual data,
-saving it in @code{start}.
-The last part of the code loops through each function name (from @code{$2} up
to
-the marker, @samp{data:}), calling the function named by the field. The
indirect
-function call itself occurs as a parameter in the call to @code{printf}.
-(The @code{printf} format string uses @samp{%s} as the format specifier so
that we
-can use functions that return strings, as well as numbers. Note that the result
-from the indirect call is concatenated with the empty string, in order to force
-it to be a string value.)
-
-Here is the result of running the program:
-
-@example
-$ @kbd{gawk -f indirectcall.awk class_data1}
-@print{} Biology 101:
-@print{} sum: <352.8>
-@print{} average: <88.2>
-@print{}
-@print{} Chemistry 305:
-@print{} sum: <356.4>
-@print{} average: <89.1>
-@print{}
-@print{} English 401:
-@print{} sum: <376.1>
-@print{} average: <94.025>
-@end example
-
-The ability to use indirect function calls is more powerful than you may
-think at first. The C and C++ languages provide ``function pointers,'' which
-are a mechanism for calling a function chosen at runtime. One of the most
-well-known uses of this ability is the C @code{qsort()} function, which sorts
-an array using the famous ``quicksort'' algorithm
-(see @uref{https://en.wikipedia.org/wiki/Quicksort, the Wikipedia article}
-for more information). To use this function, you supply a pointer to a
comparison
-function. This mechanism allows you to sort arbitrary data in an arbitrary
-fashion.
-
-We can do something similar using @command{gawk}, like this:
-
-@example
-@c file eg/lib/quicksort.awk
-# quicksort.awk --- Quicksort algorithm, with user-supplied
-# comparison function
-@c endfile
-@ignore
-@c file eg/lib/quicksort.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# January 2009
-
-@c endfile
-@end ignore
-@c file eg/lib/quicksort.awk
-
-# quicksort --- C.A.R. Hoare's quicksort algorithm. See Wikipedia
-# or almost any algorithms or computer science text.
-@c endfile
-@ignore
-@c file eg/lib/quicksort.awk
-#
-# Adapted from K&R-II, page 110
-@c endfile
-@end ignore
-@c file eg/lib/quicksort.awk
-
-function quicksort(data, left, right, less_than, i, last)
-@{
- if (left >= right) # do nothing if array contains fewer
- return # than two elements
-
- quicksort_swap(data, left, int((left + right) / 2))
- last = left
- for (i = left + 1; i <= right; i++)
- if (@@less_than(data[i], data[left]))
- quicksort_swap(data, ++last, i)
- quicksort_swap(data, left, last)
- quicksort(data, left, last - 1, less_than)
- quicksort(data, last + 1, right, less_than)
-@}
-
-# quicksort_swap --- helper function for quicksort, should really be inline
-
-function quicksort_swap(data, i, j, temp)
-@{
- temp = data[i]
- data[i] = data[j]
- data[j] = temp
-@}
-@c endfile
-@end example
-
-The @code{quicksort()} function receives the @code{data} array, the starting
and ending
-indices to sort (@code{left} and @code{right}), and the name of a function that
-performs a ``less than'' comparison. It then implements the quicksort
algorithm.
-
-To make use of the sorting function, we return to our previous example. The
-first thing to do is write some comparison functions:
-
-@example
-@c file eg/prog/indirectcall.awk
-@group
-# num_lt --- do a numeric less than comparison
-
-function num_lt(left, right)
-@{
- return ((left + 0) < (right + 0))
-@}
-@end group
-
-# num_ge --- do a numeric greater than or equal to comparison
-
-function num_ge(left, right)
-@{
- return ((left + 0) >= (right + 0))
-@}
-@c endfile
-@end example
-
-The @code{num_ge()} function is needed to perform a descending sort; when used
-to perform a ``less than'' test, it actually does the opposite (greater than
-or equal to), which yields data sorted in descending order.
-
-Next comes a sorting function. It is parameterized with the starting and
-ending field numbers and the comparison function. It builds an array with
-the data and calls @code{quicksort()} appropriately, and then formats the
-results as a single string:
-
-@example
-@c file eg/prog/indirectcall.awk
-# do_sort --- sort the data according to `compare'
-# and return it as a string
-
-function do_sort(first, last, compare, data, i, retval)
-@{
- delete data
- for (i = 1; first <= last; first++) @{
- data[i] = $first
- i++
- @}
-
- quicksort(data, 1, i-1, compare)
-
- retval = data[1]
- for (i = 2; i in data; i++)
- retval = retval " " data[i]
-
- return retval
-@}
-@c endfile
-@end example
-
-Finally, the two sorting functions call @code{do_sort()}, passing in the
-names of the two comparison functions:
-
-@example
-@c file eg/prog/indirectcall.awk
-@group
-# sort --- sort the data in ascending order and return it as a string
-
-function sort(first, last)
-@{
- return do_sort(first, last, "num_lt")
-@}
-@end group
-
-@group
-# rsort --- sort the data in descending order and return it as a string
-
-function rsort(first, last)
-@{
- return do_sort(first, last, "num_ge")
-@}
-@end group
-@c endfile
-@end example
-
-Here is an extended version of the @value{DF}:
-
-@example
-@c file eg/data/class_data2
-Biology_101 sum average sort rsort data: 87.0 92.4 78.5 94.9
-Chemistry_305 sum average sort rsort data: 75.2 98.3 94.7 88.2
-English_401 sum average sort rsort data: 100.0 95.6 87.1 93.4
-@c endfile
-@end example
-
-Finally, here are the results when the enhanced program is run:
-
-@example
-$ @kbd{gawk -f quicksort.awk -f indirectcall.awk class_data2}
-@print{} Biology 101:
-@print{} sum: <352.8>
-@print{} average: <88.2>
-@print{} sort: <78.5 87.0 92.4 94.9>
-@print{} rsort: <94.9 92.4 87.0 78.5>
-@print{}
-@print{} Chemistry 305:
-@print{} sum: <356.4>
-@print{} average: <89.1>
-@print{} sort: <75.2 88.2 94.7 98.3>
-@print{} rsort: <98.3 94.7 88.2 75.2>
-@print{}
-@print{} English 401:
-@print{} sum: <376.1>
-@print{} average: <94.025>
-@print{} sort: <87.1 93.4 95.6 100.0>
-@print{} rsort: <100.0 95.6 93.4 87.1>
-@end example
-
-Another example where indirect functions calls are useful can be found in
-processing arrays. This is described in @ref{Walking Arrays}.
-
-Remember that you must supply a leading @samp{@@} in front of an indirect
function call.
-
-Starting with @value{PVERSION} 4.1.2 of @command{gawk}, indirect function
-calls may also be used with built-in functions and with extension functions
-(@pxref{Dynamic Extensions}). There are some limitations when calling
-built-in functions indirectly, as follows.
-
-@itemize @value{BULLET}
-@item
-You cannot pass a regular expression constant to a built-in function
-through an indirect function call. This applies to the @code{sub()},
-@code{gsub()}, @code{gensub()}, @code{match()}, @code{split()} and
-@code{patsplit()} functions. However, you can pass a strongly typed
-regexp constant (@pxref{Strong Regexp Constants}).
-
-@item
-If calling @code{sub()} or @code{gsub()}, you may only pass two arguments,
-since those functions are unusual in that they update their third argument.
-This means that @code{$0} will be updated.
-
-@item
-You cannot indirectly call built-in functions that can take @code{$0} as
-a default parameter; you must supply an argument instead. For example,
-you must pass an argument to @code{length()} if calling it indirectly.
-
-@item
-Calling a built-in function indirectly with the wrong number of arguments
-for that function causes a fatal error. For example, calling
-@code{length()} with two arguments. These errors are found at runtime
-instead of when @command{gawk} parses your program, since @command{gawk}
-doesn't know until runtime if you have passed the correct number of
-arguments or not.
-@end itemize
-
-@command{gawk} does its best to make indirect function calls efficient.
-For example, in the following case:
-
-@example
-for (i = 1; i <= n; i++)
- @@the_function()
-@end example
-
-@noindent
-@command{gawk} looks up the actual function to call only once.
-
-@node Functions Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-@command{awk} provides built-in functions and lets you define your own
-functions.
-
-@item
-POSIX @command{awk} provides three kinds of built-in functions: numeric,
-string, and I/O. @command{gawk} provides functions that sort arrays, work
-with values representing time, do bit manipulation, determine variable
-type (array versus scalar), and internationalize and localize programs.
-@command{gawk} also provides several extensions to some of standard
-functions, typically in the form of additional arguments.
-
-@item
-Functions accept zero or more arguments and return a value. The
-expressions that provide the argument values are completely evaluated
-before the function is called. Order of evaluation is not defined.
-The return value can be ignored.
-
-@item
-The handling of backslash in @code{sub()} and @code{gsub()} is not simple.
-It is more straightforward in @command{gawk}'s @code{gensub()} function,
-but that function still requires care in its use.
-
-@item
-User-defined functions provide important capabilities but come with
-some syntactic inelegancies. In a function call, there cannot be any
-space between the function name and the opening left parenthesis of the
-argument list. Also, there is no provision for local variables, so the
-convention is to add extra parameters, and to separate them visually
-from the real parameters by extra whitespace.
-
-@item
-User-defined functions may call other user-defined (and built-in)
-functions and may call themselves recursively. Function parameters
-``hide'' any global variables of the same names.
-You cannot use the name of a reserved variable (such as @code{ARGC})
-as the name of a parameter in user-defined functions.
-
-@item
-Scalar values are passed to user-defined functions by value. Array
-parameters are passed by reference; any changes made by the function to
-array parameters are thus visible after the function has returned.
-
-@item
-Use the @code{return} statement to return from a user-defined function.
-An optional expression becomes the function's return value. Only scalar
-values may be returned by a function.
-
-@item
-If a variable that has never been used is passed to a user-defined
-function, how that function treats the variable can set its nature:
-either scalar or array.
-
-@item
-@command{gawk} provides indirect function calls using a special syntax.
-By setting a variable to the name of a function, you can
-determine at runtime what function will be called at that point in the
-program. This is equivalent to function pointers in C and C++.
-
-@end itemize
-
-
-@ifnotinfo
-@part @value{PART2}Problem Solving with @command{awk}
-@end ifnotinfo
-
-@ifdocbook
-Part II shows how to use @command{awk} and @command{gawk} for problem solving.
-There is lots of code here for you to read and learn from.
-It contains the following chapters:
-
-@itemize @value{BULLET}
-@item
-@ref{Library Functions}
-
-@item
-@ref{Sample Programs}
-@end itemize
-@end ifdocbook
-
-@node Library Functions
-@chapter A Library of @command{awk} Functions
-@cindex libraries of @command{awk} functions
-@cindex functions @subentry library
-@cindex functions @subentry user-defined @subentry library of
-
-@ref{User-defined} describes how to write
-your own @command{awk} functions. Writing functions is important, because
-it allows you to encapsulate algorithms and program tasks in a single
-place. It simplifies programming, making program development more
-manageable and making programs more readable.
-
-@cindex Kernighan, Brian @subentry quotes
-@cindex Plauger, P.J.@:
-In their seminal 1976 book, @cite{Software Tools},@footnote{Sadly, over 35
-years later, many of the lessons taught by this book have yet to be
-learned by a vast number of practicing programmers.} Brian Kernighan
-and P.J.@: Plauger wrote:
-
-@quotation
-Good Programming is not learned from generalities, but by seeing how
-significant programs can be made clean, easy to read, easy to maintain and
-modify, human-engineered, efficient and reliable, by the application of
-common sense and good programming practices. Careful study and imitation
-of good programs leads to better writing.
-@end quotation
-
-In fact, they felt this idea was so important that they placed this
-statement on the cover of their book. Because we believe strongly
-that their statement is correct, this @value{CHAPTER} and @ref{Sample
-Programs}, provide a good-sized body of code for you to read and, we hope,
-to learn from.
-
-This @value{CHAPTER} presents a library of useful @command{awk} functions.
-Many of the sample programs presented later in this @value{DOCUMENT}
-use these functions.
-The functions are presented here in a progression from simple to complex.
-
-@cindex Texinfo
-@ref{Extract Program}
-presents a program that you can use to extract the source code for
-these example library functions and programs from the Texinfo source
-for this @value{DOCUMENT}.
-(This has already been done as part of the @command{gawk} distribution.)
-
-@ifclear FOR_PRINT
-If you have written one or more useful, general-purpose @command{awk} functions
-and would like to contribute them to the @command{awk} user community, see
-@ref{How To Contribute}, for more information.
-@end ifclear
-
-@cindex portability @subentry example programs
-The programs in this @value{CHAPTER} and in
-@ref{Sample Programs},
-freely use @command{gawk}-specific features.
-Rewriting these programs for different implementations of @command{awk}
-is pretty straightforward:
-
-@itemize @value{BULLET}
-@item
-Diagnostic error messages are sent to @file{/dev/stderr}.
-Use @samp{| "cat 1>&2"} instead of @samp{> "/dev/stderr"} if your system
-does not have a @file{/dev/stderr}, or if you cannot use @command{gawk}.
-
-@item
-@c 12/2000: Thanks to Nelson Beebe for pointing out the output issue.
-@cindex case sensitivity @subentry example programs
-@cindex @code{IGNORECASE} variable @subentry in example programs
-Finally, some of the programs choose to ignore upper- and lowercase
-distinctions in their input. They do so by assigning one to @code{IGNORECASE}.
-You can achieve almost the same effect@footnote{The effects are
-not identical. Output of the transformed
-record will be in all lowercase, while @code{IGNORECASE} preserves the original
-contents of the input record.} by adding the following rule to the
-beginning of the program:
-
-@example
-# ignore case
-@{ $0 = tolower($0) @}
-@end example
-
-@noindent
-Also, verify that all regexp and string constants used in
-comparisons use only lowercase letters.
-@end itemize
-
-@menu
-* Library Names:: How to best name private global variables in
- library functions.
-* General Functions:: Functions that are of general use.
-* Data File Management:: Functions for managing command-line data
- files.
-* Getopt Function:: A function for processing command-line
- arguments.
-* Passwd Functions:: Functions for getting user information.
-* Group Functions:: Functions for getting group information.
-* Walking Arrays:: A function to walk arrays of arrays.
-* Library Functions Summary:: Summary of library functions.
-* Library Exercises:: Exercises.
-@end menu
-
-@node Library Names
-@section Naming Library Function Global Variables
-
-@cindex names @subentry arrays/variables
-@cindex names @subentry functions
-@cindex naming issues
-@cindex @command{awk} programs @subentry documenting
-@cindex documentation @subentry of @command{awk} programs
-Due to the way the @command{awk} language evolved, variables are either
-@dfn{global} (usable by the entire program) or @dfn{local} (usable just by
-a specific function). There is no intermediate state analogous to
-@code{static} variables in C.
-
-@cindex variables @subentry global @subentry for library functions
-@cindex private variables
-@cindex variables @subentry private
-Library functions often need to have global variables that they can use to
-preserve state information between calls to the function---for example,
-@code{getopt()}'s variable @code{_opti}
-(@pxref{Getopt Function}).
-Such variables are called @dfn{private}, as the only functions that need to
-use them are the ones in the library.
-
-When writing a library function, you should try to choose names for your
-private variables that will not conflict with any variables used by
-either another library function or a user's main program. For example, a
-name like @code{i} or @code{j} is not a good choice, because user programs
-often use variable names like these for their own purposes.
-
-@cindex programming conventions @subentry private variable names
-The example programs shown in this @value{CHAPTER} all start the names of their
-private variables with an underscore (@samp{_}). Users generally don't use
-leading underscores in their variable names, so this convention immediately
-decreases the chances that the variable names will be accidentally shared
-with the user's program.
-
-@cindex @code{_} (underscore) @subentry in names of private variables
-@cindex underscore (@code{_}) @subentry in names of private variables
-In addition, several of the library functions use a prefix that helps
-indicate what function or set of functions use the variables---for example,
-@code{_pw_byname()} in the user database routines
-(@pxref{Passwd Functions}).
-This convention is recommended, as it even further decreases the
-chance of inadvertent conflict among variable names. Note that this
-convention is used equally well for variable names and for private
-function names.@footnote{Although all the library routines could have
-been rewritten to use this convention, this was not done, in order to
-show how our own @command{awk} programming style has evolved and to
-provide some basis for this discussion.}
-
-As a final note on variable naming, if a function makes global variables
-available for use by a main program, it is a good convention to start those
-variables' names with a capital letter---for
-example, @code{getopt()}'s @code{Opterr} and @code{Optind} variables
-(@pxref{Getopt Function}).
-The leading capital letter indicates that it is global, while the fact that
-the variable name is not all capital letters indicates that the variable is
-not one of @command{awk}'s predefined variables, such as @code{FS}.
-
-@cindex @option{--dump-variables} option @subentry using for library functions
-It is also important that @emph{all} variables in library
-functions that do not need to save state are, in fact, declared
-local.@footnote{@command{gawk}'s @option{--dump-variables} command-line
-option is useful for verifying this.} If this is not done, the variables
-could accidentally be used in the user's program, leading to bugs that
-are very difficult to track down:
-
-@example
-function lib_func(x, y, l1, l2)
-@{
- @dots{}
- # some_var should be local but by oversight is not
- @var{use variable} some_var
- @dots{}
-@}
-@end example
-
-@cindex arrays @subentry associative @subentry library functions and
-@cindex libraries of @command{awk} functions @subentry associative arrays and
-@cindex functions @subentry library @subentry associative arrays and
-@cindex Tcl
-A different convention, common in the Tcl community, is to use a single
-associative array to hold the values needed by the library function(s), or
-``package.'' This significantly decreases the number of actual global names
-in use. For example, the functions described in
-@ref{Passwd Functions}
-might have used array elements @code{@w{PW_data["inited"]}},
@code{@w{PW_data["total"]}},
-@code{@w{PW_data["count"]}}, and @code{@w{PW_data["awklib"]}}, instead of
-@code{@w{_pw_inited}}, @code{@w{_pw_awklib}}, @code{@w{_pw_total}},
-and @code{@w{_pw_count}}.
-
-The conventions presented in this @value{SECTION} are exactly
-that: conventions. You are not required to write your programs this
-way---we merely recommend that you do so.
-
-Beginning with @value{PVERSION} 5.0, @command{gawk} provides
-a powerful mechanism for solving the problems described in this
-section: @dfn{namespaces}. Namespaces and their use are described
-in detail in @ref{Namespaces}.
-
-@node General Functions
-@section General Programming
-
-This @value{SECTION} presents a number of functions that are of general
-programming use.
-
-@menu
-* Strtonum Function:: A replacement for the built-in
- @code{strtonum()} function.
-* Assert Function:: A function for assertions in @command{awk}
- programs.
-* Round Function:: A function for rounding if @code{sprintf()}
- does not do it correctly.
-* Cliff Random Function:: The Cliff Random Number Generator.
-* Ordinal Functions:: Functions for using characters as numbers and
- vice versa.
-* Join Function:: A function to join an array into a string.
-* Getlocaltime Function:: A function to get formatted times.
-* Readfile Function:: A function to read an entire file at once.
-* Shell Quoting:: A function to quote strings for the shell.
-* Isnumeric Function:: A function to test whether a value is numeric.
-* To CSV Function:: A function to convert output to CSV format.
-@end menu
-
-@node Strtonum Function
-@subsection Converting Strings to Numbers
-
-The @code{strtonum()} function (@pxref{String Functions})
-is a @command{gawk} extension. The following function
-provides an implementation for other versions of @command{awk}:
-
-@example
-@c file eg/lib/strtonum.awk
-# mystrtonum --- convert string to number
-
-@c endfile
-@ignore
-@c file eg/lib/strtonum.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# February, 2004
-# Revised June, 2014
-
-@c endfile
-@end ignore
-@c file eg/lib/strtonum.awk
-function mystrtonum(str, ret, n, i, k, c)
-@{
- if (str ~ /^0[0-7]*$/) @{
- # octal
- n = length(str)
- ret = 0
- for (i = 1; i <= n; i++) @{
- c = substr(str, i, 1)
- # index() returns 0 if c not in string,
- # includes c == "0"
- k = index("1234567", c)
-
- ret = ret * 8 + k
- @}
- @} else if (str ~ /^0[xX][[:xdigit:]]+$/) @{
- # hexadecimal
- str = substr(str, 3) # lop off leading 0x
- n = length(str)
- ret = 0
- for (i = 1; i <= n; i++) @{
- c = substr(str, i, 1)
- c = tolower(c)
- # index() returns 0 if c not in string,
- # includes c == "0"
- k = index("123456789abcdef", c)
-
- ret = ret * 16 + k
- @}
- @} else if (str ~ \
- /^[-+]?([0-9]+([.][0-9]*([Ee][0-9]+)?)?|([.][0-9]+([Ee][-+]?[0-9]+)?))$/) @{
- # decimal number, possibly floating point
- ret = str + 0
- @} else
- ret = "NOT-A-NUMBER"
-
- return ret
-@}
-
-# BEGIN @{ # gawk test harness
-# a[1] = "25"
-# a[2] = ".31"
-# a[3] = "0123"
-# a[4] = "0xdeadBEEF"
-# a[5] = "123.45"
-# a[6] = "1.e3"
-# a[7] = "1.32"
-# a[8] = "1.32E2"
-#
-# for (i = 1; i in a; i++)
-# print a[i], strtonum(a[i]), mystrtonum(a[i])
-# @}
-@c endfile
-@end example
-
-The function first looks for C-style octal numbers (base 8).
-If the input string matches a regular expression describing octal
-numbers, then @code{mystrtonum()} loops through each character in the
-string. It sets @code{k} to the index in @code{"1234567"} of the current
-octal digit.
-The return value will either be the same number as the digit, or zero
-if the character is not there, which will be true for a @samp{0}.
-This is safe, because the regexp test in the @code{if} ensures that
-only octal values are converted.
-
-Similar logic applies to the code that checks for and converts a
-hexadecimal value, which starts with @samp{0x} or @samp{0X}.
-The use of @code{tolower()} simplifies the computation for finding
-the correct numeric value for each hexadecimal digit.
-
-Finally, if the string matches the (rather complicated) regexp for a
-regular decimal integer or floating-point number, the computation
-@samp{ret = str + 0} lets @command{awk} convert the value to a
-number.
-
-A commented-out test program is included, so that the function can
-be tested with @command{gawk} and the results compared to the built-in
-@code{strtonum()} function.
-
-@node Assert Function
-@subsection Assertions
-
-@cindex assertions
-@cindex @code{assert()} function (C library)
-@cindex C library functions @subentry @code{assert()}
-@cindex libraries of @command{awk} functions @subentry assertions
-@cindex functions @subentry library @subentry assertions
-@cindex @command{awk} programs @subentry lengthy @subentry assertions
-When writing large programs, it is often useful to know
-that a condition or set of conditions is true. Before proceeding with a
-particular computation, you make a statement about what you believe to be
-the case. Such a statement is known as an
-@dfn{assertion}. The C language provides an @code{<assert.h>} header file
-and corresponding @code{assert()} macro that a programmer can use to make
-assertions. If an assertion fails, the @code{assert()} macro arranges to
-print a diagnostic message describing the condition that should have
-been true but was not, and then it kills the program. In C, using
-@code{assert()} looks this:
-
-@example
-@group
-#include <assert.h>
-
-int myfunc(int a, double b)
-@{
- assert(a <= 5 && b >= 17.1);
- @dots{}
-@}
-@end group
-@end example
-
-If the assertion fails, the program prints a message similar to this:
-
-@example
-prog.c:5: assertion failed: a <= 5 && b >= 17.1
-@end example
-
-@cindex @code{assert()} user-defined function
-@cindex user-defined @subentry function @subentry @code{assert()}
-The C language makes it possible to turn the condition into a string for use
-in printing the diagnostic message. This is not possible in @command{awk}, so
-this @code{assert()} function also requires a string version of the condition
-that is being tested.
-Following is the function:
-
-@example
-@c file eg/lib/assert.awk
-# assert --- assert that a condition is true. Otherwise, exit.
-
-@c endfile
-@ignore
-@c file eg/lib/assert.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May, 1993
-
-@c endfile
-@end ignore
-@c file eg/lib/assert.awk
-function assert(condition, string)
-@{
- if (! condition) @{
- printf("%s:%d: assertion failed: %s\n",
- FILENAME, FNR, string) > "/dev/stderr"
- _assert_exit = 1
- exit 1
- @}
-@}
-
-@group
-END @{
- if (_assert_exit)
- exit 1
-@}
-@end group
-@c endfile
-@end example
-
-The @code{assert()} function tests the @code{condition} parameter. If it
-is false, it prints a message to standard error, using the @code{string}
-parameter to describe the failed condition. It then sets the variable
-@code{_assert_exit} to one and executes the @code{exit} statement.
-The @code{exit} statement jumps to the @code{END} rule. If the @code{END}
-rule finds @code{_assert_exit} to be true, it exits immediately.
-
-The purpose of the test in the @code{END} rule is to
-keep any other @code{END} rules from running. When an assertion fails, the
-program should exit immediately.
-If no assertions fail, then @code{_assert_exit} is still
-false when the @code{END} rule is run normally, and the rest of the
-program's @code{END} rules execute.
-For all of this to work correctly, @file{assert.awk} must be the
-first source file read by @command{awk}.
-The function can be used in a program in the following way:
-
-@example
-function myfunc(a, b)
-@{
- assert(a <= 5 && b >= 17.1, "a <= 5 && b >= 17.1")
- @dots{}
-@}
-@end example
-
-@noindent
-If the assertion fails, you see a message similar to the following:
-
-@example
-mydata:1357: assertion failed: a <= 5 && b >= 17.1
-@end example
-
-@cindex @code{END} pattern @subentry @code{assert()} user-defined function and
-There is a small problem with this version of @code{assert()}.
-An @code{END} rule is automatically added
-to the program calling @code{assert()}. Normally, if a program consists
-of just a @code{BEGIN} rule, the input files and/or standard input are
-not read. However, now that the program has an @code{END} rule, @command{awk}
-attempts to read the input @value{DF}s or standard input
-(@pxref{Using BEGIN/END}),
-most likely causing the program to hang as it waits for input.
-
-@cindex @code{BEGIN} pattern @subentry @code{assert()} user-defined function
and
-There is a simple workaround to this:
-make sure that such a @code{BEGIN} rule always ends
-with an @code{exit} statement.
-
-@node Round Function
-@subsection Rounding Numbers
-
-@cindex rounding numbers
-@cindex numbers @subentry rounding
-@cindex libraries of @command{awk} functions @subentry rounding numbers
-@cindex functions @subentry library @subentry rounding numbers
-@cindex @code{print} statement @subentry @code{sprintf()} function and
-@cindex @code{printf} statement @subentry @code{sprintf()} function and
-@cindex @code{sprintf()} function @subentry @code{print}/@code{printf}
statements and
-The way @code{printf} and @code{sprintf()}
-(@pxref{Printf})
-perform rounding often depends upon the system's C @code{sprintf()}
-subroutine. On many machines, @code{sprintf()} rounding is @dfn{unbiased},
-which means it doesn't always round a trailing .5 up, contrary
-to naive expectations. In unbiased rounding, .5 rounds to even,
-rather than always up, so 1.5 rounds to 2 but 4.5 rounds to 4. This means
-that if you are using a format that does rounding (e.g., @code{"%.0f"}),
-you should check what your system does. The following function does
-traditional rounding; it might be useful if your @command{awk}'s @code{printf}
-does unbiased rounding:
-
-@cindex @code{round()} user-defined function
-@cindex user-defined @subentry function @subentry @code{round()}
-@example
-@c file eg/lib/round.awk
-# round.awk --- do normal rounding
-@c endfile
-@ignore
-@c file eg/lib/round.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# August, 1996
-@c endfile
-@end ignore
-@c file eg/lib/round.awk
-
-function round(x, ival, aval, fraction)
-@{
- ival = int(x) # integer part, int() truncates
-
- # see if fractional part
- if (ival == x) # no fraction
- return ival # ensure no decimals
-
- if (x < 0) @{
- aval = -x # absolute value
- ival = int(aval)
- fraction = aval - ival
- if (fraction >= .5)
- return int(x) - 1 # -2.5 --> -3
- else
- return int(x) # -2.3 --> -2
- @} else @{
- fraction = x - ival
- if (fraction >= .5)
- return ival + 1
- else
- return ival
- @}
-@}
-@c endfile
-@c don't include test harness in the file that gets installed
-@group
-# test harness
-# @{ print $0, round($0) @}
-@end group
-@end example
-
-@node Cliff Random Function
-@subsection The Cliff Random Number Generator
-@cindex random numbers @subentry Cliff
-@cindex Cliff random numbers
-@cindex numbers @subentry Cliff random
-@cindex functions @subentry library @subentry Cliff random numbers
-
-The
-@uref{http://mathworld.wolfram.com/CliffRandomNumberGenerator.html, Cliff
random number generator}
-is a very simple random number generator that ``passes the noise sphere test
-for randomness by showing no structure.''
-It is easily programmed, in less than 10 lines of @command{awk} code:
-
-@cindex @code{cliff_rand()} user-defined function
-@cindex user-defined @subentry function @subentry @code{cliff_rand()}
-@example
-@c file eg/lib/cliff_rand.awk
-# cliff_rand.awk --- generate Cliff random numbers
-@c endfile
-@ignore
-@c file eg/lib/cliff_rand.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# December 2000
-@c endfile
-@end ignore
-@c file eg/lib/cliff_rand.awk
-
-BEGIN @{ _cliff_seed = 0.1 @}
-
-function cliff_rand()
-@{
- _cliff_seed = (100 * log(_cliff_seed)) % 1
- if (_cliff_seed < 0)
- _cliff_seed = - _cliff_seed
- return _cliff_seed
-@}
-@c endfile
-@end example
-
-This algorithm requires an initial ``seed'' of 0.1. Each new value
-uses the current seed as input for the calculation.
-If the built-in @code{rand()} function
-(@pxref{Numeric Functions})
-isn't random enough, you might try using this function instead.
-
-@node Ordinal Functions
-@subsection Translating Between Characters and Numbers
-
-@cindex libraries of @command{awk} functions @subentry character values as
numbers
-@cindex functions @subentry library @subentry character values as numbers
-@cindex characters @subentry values of as numbers
-@cindex numbers @subentry as values of characters
-One commercial implementation of @command{awk} supplies a built-in function,
-@code{ord()}, which takes a character and returns the numeric value for that
-character in the machine's character set. If the string passed to
-@code{ord()} has more than one character, only the first one is used.
-
-The inverse of this function is @code{chr()} (from the function of the same
-name in Pascal), which takes a number and returns the corresponding character.
-Both functions are written very nicely in @command{awk}; there is no real
-reason to build them into the @command{awk} interpreter:
-
-@cindex @code{ord()} user-defined function
-@cindex user-defined @subentry function @subentry @code{ord()}
-@cindex @code{chr()} user-defined function
-@cindex user-defined @subentry function @subentry @code{chr()}
-@cindex @code{_ord_init()} user-defined function
-@cindex user-defined @subentry function @subentry @code{_ord_init()}
-@example
-@c file eg/lib/ord.awk
-# ord.awk --- do ord and chr
-
-# Global identifiers:
-# _ord_: numerical values indexed by characters
-# _ord_init: function to initialize _ord_
-@c endfile
-@ignore
-@c file eg/lib/ord.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# 16 January, 1992
-# 20 July, 1992, revised
-@c endfile
-@end ignore
-@c file eg/lib/ord.awk
-
-BEGIN @{ _ord_init() @}
-
-function _ord_init( low, high, i, t)
-@{
- low = sprintf("%c", 7) # BEL is ascii 7
- if (low == "\a") @{ # regular ascii
- low = 0
- high = 127
- @} else if (sprintf("%c", 128 + 7) == "\a") @{
- # ascii, mark parity
- low = 128
- high = 255
- @} else @{ # ebcdic(!)
- low = 0
- high = 255
- @}
-
- for (i = low; i <= high; i++) @{
- t = sprintf("%c", i)
- _ord_[t] = i
- @}
-@}
-@c endfile
-@end example
-
-@cindex character sets (machine character encodings)
-@cindex ASCII
-@cindex EBCDIC
-@cindex Unicode
-@cindex mark parity
-Some explanation of the numbers used by @code{_ord_init()} is worthwhile.
-The most prominent character set in use today is ASCII.@footnote{This
-is changing; many systems use Unicode, a very large character set
-that includes ASCII as a subset. On systems with full Unicode support,
-a character can occupy up to 32 bits, making simple tests such as
-used here prohibitively expensive.}
-Although an
-8-bit byte can hold 256 distinct values (from 0 to 255), ASCII only
-defines characters that use the values from 0 to 127.@footnote{ASCII
-has been extended in many countries to use the values from 128 to 255
-for country-specific characters. If your system uses these extensions,
-you can simplify @code{_ord_init()} to loop from 0 to 255.}
-In the now distant past,
-at least one minicomputer manufacturer
-@c Pr1me, blech
-used ASCII, but with mark parity, meaning that the leftmost bit in the byte
-is always 1. This means that on those systems, characters
-have numeric values from 128 to 255.
-Finally, large mainframe systems use the EBCDIC character set, which
-uses all 256 values.
-There are other character sets in use on some older systems, but
-they are not really worth worrying about:
-
-@example
-@c file eg/lib/ord.awk
-function ord(str, c)
-@{
- # only first character is of interest
- c = substr(str, 1, 1)
- return _ord_[c]
-@}
-
-function chr(c)
-@{
- # force c to be numeric by adding 0
- return sprintf("%c", c + 0)
-@}
-@c endfile
-
-#### test code ####
-# BEGIN @{
-# for (;;) @{
-# printf("enter a character: ")
-# if (getline var <= 0)
-# break
-# printf("ord(%s) = %d\n", var, ord(var))
-# @}
-# @}
-@c endfile
-@end example
-
-An obvious improvement to these functions is to move the code for the
-@code{@w{_ord_init}} function into the body of the @code{BEGIN} rule. It was
-written this way initially for ease of development.
-There is a ``test program'' in a @code{BEGIN} rule, to test the
-function. It is commented out for production use.
-
-@node Join Function
-@subsection Merging an Array into a String
-
-@cindex libraries of @command{awk} functions @subentry merging arrays into
strings
-@cindex functions @subentry library @subentry merging arrays into strings
-@cindex strings @subentry merging arrays into
-@cindex arrays @subentry merging into strings
-When doing string processing, it is often useful to be able to join
-all the strings in an array into one long string. The following function,
-@code{join()}, accomplishes this task. It is used later in several of
-the application programs
-(@pxref{Sample Programs}).
-
-Good function design is important; this function needs to be general, but it
-should also have a reasonable default behavior. It is called with an array
-as well as the beginning and ending indices of the elements in the array to be
-merged. This assumes that the array indices are numeric---a reasonable
-assumption, as the array was likely created with @code{split()}
-(@pxref{String Functions}):
-
-@cindex @code{join()} user-defined function
-@cindex user-defined @subentry function @subentry @code{join()}
-@example
-@c file eg/lib/join.awk
-# join.awk --- join an array into a string
-@c endfile
-@ignore
-@c file eg/lib/join.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-@c endfile
-@end ignore
-@c file eg/lib/join.awk
-
-function join(array, start, end, sep, result, i)
-@{
- if (sep == "")
- sep = " "
- else if (sep == SUBSEP) # magic value
- sep = ""
- result = array[start]
- for (i = start + 1; i <= end; i++)
- result = result sep array[i]
- return result
-@}
-@c endfile
-@end example
-
-An optional additional argument is the separator to use when joining the
-strings back together. If the caller supplies a nonempty value,
-@code{join()} uses it; if it is not supplied, it has a null
-value. In this case, @code{join()} uses a single space as a default
-separator for the strings. If the value is equal to @code{SUBSEP},
-then @code{join()} joins the strings with no separator between them.
-@code{SUBSEP} serves as a ``magic'' value to indicate that there should
-be no separation between the component strings.@footnote{It would
-be nice if @command{awk} had an assignment operator for concatenation.
-The lack of an explicit operator for concatenation makes string operations
-more difficult than they really need to be.}
-
-@node Getlocaltime Function
-@subsection Managing the Time of Day
-
-@cindex libraries of @command{awk} functions @subentry managing @subentry time
-@cindex functions @subentry library @subentry managing time
-@cindex timestamps @subentry formatted
-@cindex time @subentry managing
-The @code{systime()} and @code{strftime()} functions described in
-@ref{Time Functions}
-provide the minimum functionality necessary for dealing with the time of day
-in human-readable form. Although @code{strftime()} is extensive, the control
-formats are not necessarily easy to remember or intuitively obvious when
-reading a program.
-
-The following function, @code{getlocaltime()}, populates a user-supplied array
-with preformatted time information. It returns a string with the current
-time formatted in the same way as the @command{date} utility:
-
-@cindex @code{getlocaltime()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getlocaltime()}
-@example
-@c file eg/lib/gettime.awk
-# getlocaltime.awk --- get the time of day in a usable format
-@c endfile
-@ignore
-@c file eg/lib/gettime.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain, May 1993
-#
-@c endfile
-@end ignore
-@c file eg/lib/gettime.awk
-
-# Returns a string in the format of output of date(1)
-# Populates the array argument time with individual values:
-# time["second"] -- seconds (0 - 59)
-# time["minute"] -- minutes (0 - 59)
-# time["hour"] -- hours (0 - 23)
-# time["althour"] -- hours (0 - 12)
-# time["monthday"] -- day of month (1 - 31)
-# time["month"] -- month of year (1 - 12)
-# time["monthname"] -- name of the month
-# time["shortmonth"] -- short name of the month
-# time["year"] -- year modulo 100 (0 - 99)
-# time["fullyear"] -- full year
-# time["weekday"] -- day of week (Sunday = 0)
-# time["altweekday"] -- day of week (Monday = 0)
-# time["dayname"] -- name of weekday
-# time["shortdayname"] -- short name of weekday
-# time["yearday"] -- day of year (0 - 365)
-# time["timezone"] -- abbreviation of timezone name
-# time["ampm"] -- AM or PM designation
-# time["weeknum"] -- week number, Sunday first day
-# time["altweeknum"] -- week number, Monday first day
-
-function getlocaltime(time, ret, now, i)
-@{
- # get time once, avoids unnecessary system calls
- now = systime()
-
- # return date(1)-style output
- ret = strftime("%a %b %e %H:%M:%S %Z %Y", now)
-
- # clear out target array
- delete time
-
- # fill in values, force numeric values to be
- # numeric by adding 0
- time["second"] = strftime("%S", now) + 0
- time["minute"] = strftime("%M", now) + 0
- time["hour"] = strftime("%H", now) + 0
- time["althour"] = strftime("%I", now) + 0
- time["monthday"] = strftime("%d", now) + 0
- time["month"] = strftime("%m", now) + 0
- time["monthname"] = strftime("%B", now)
- time["shortmonth"] = strftime("%b", now)
- time["year"] = strftime("%y", now) + 0
- time["fullyear"] = strftime("%Y", now) + 0
- time["weekday"] = strftime("%w", now) + 0
- time["altweekday"] = strftime("%u", now) + 0
- time["dayname"] = strftime("%A", now)
- time["shortdayname"] = strftime("%a", now)
- time["yearday"] = strftime("%j", now) + 0
- time["timezone"] = strftime("%Z", now)
- time["ampm"] = strftime("%p", now)
- time["weeknum"] = strftime("%U", now) + 0
- time["altweeknum"] = strftime("%W", now) + 0
-
- return ret
-@}
-@c endfile
-@end example
-
-The string indices are easier to use and read than the various formats
-required by @code{strftime()}. The @code{alarm} program presented in
-@ref{Alarm Program}
-uses this function.
-A more general design for the @code{getlocaltime()} function would have
-allowed the user to supply an optional timestamp value to use instead
-of the current time.
-
-@node Readfile Function
-@subsection Reading a Whole File at Once
-
-Often, it is convenient to have the entire contents of a file available
-in memory as a single string. A straightforward but naive way to
-do that might be as follows:
-
-@example
-function readfile1(file, tmp, contents)
-@{
- if ((getline tmp < file) < 0)
- return
-
- contents = tmp RT
- while ((getline tmp < file) > 0)
- contents = contents tmp RT
-
- close(file)
- return contents
-@}
-@end example
-
-This function reads from @code{file} one record at a time, building
-up the full contents of the file in the local variable @code{contents}.
-It works, but is not necessarily efficient.
-
-The following function, based on a suggestion by Denis Shirokov,
-reads the entire contents of the named file in one shot:
-
-@cindex @code{readfile()} user-defined function
-@cindex user-defined @subentry function @subentry @code{readfile()}
-@example
-@c file eg/lib/readfile.awk
-# readfile.awk --- read an entire file at once
-@c endfile
-@ignore
-@c file eg/lib/readfile.awk
-#
-# Original idea by Denis Shirokov, cosmogen@@gmail.com, April 2013
-#
-@c endfile
-@end ignore
-@c file eg/lib/readfile.awk
-
-function readfile(file, tmp, save_rs)
-@{
- save_rs = RS
- RS = "^$"
- getline tmp < file
- close(file)
- RS = save_rs
-
- return tmp
-@}
-@c endfile
-@end example
-
-It works by setting @code{RS} to @samp{^$}, a regular expression that
-will never match if the file has contents. @command{gawk} reads data from
-the file into @code{tmp}, attempting to match @code{RS}. The match fails
-after each read, but fails quickly, such that @command{gawk} fills
-@code{tmp} with the entire contents of the file.
-(@xref{Records} for information on @code{RT} and @code{RS}.)
-
-In the case that @code{file} is empty, the return value is the null
-string. Thus, calling code may use something like:
-
-@example
-contents = readfile("/some/path")
-if (length(contents) == 0)
- # file was empty @dots{}
-@end example
-
-This tests the result to see if it is empty or not. An equivalent
-test would be @samp{@w{contents == ""}}.
-
-@xref{Extension Sample Readfile} for an extension function that
-also reads an entire file into memory.
-
-@node Shell Quoting
-@subsection Quoting Strings to Pass to the Shell
-
-@c included by permission
-@ignore
-Date: Sun, 27 Jul 2014 17:16:16 -0700
-Message-ID:
<CAKuGj+iCF_obaCLDUX60aSAgbfocFVtguG39GyeoNxTFby5sqQ@mail.gmail.com>
-Subject: Useful awk function
-From: Mike Brennan <mike@madronabluff.com>
-To: Arnold Robbins <arnold@skeeve.com>
-@end ignore
-
-Michael Brennan offers the following programming pattern,
-which he uses frequently:
-
-@example
-#! /bin/sh
-
-awkp='
- @dots{}
- '
-
-@var{input_program} | awk "$awkp" | /bin/sh
-@end example
-
-For example, a program of his named @command{flac-edit} has this form:
-
-@example
-$ @kbd{flac-edit -song="Whoope! That's Great" file.flac}
-@end example
-
-It generates the following output, which is to be piped to
-the shell (@file{/bin/sh}):
-
-@example
-chmod +w file.flac
-metaflac --remove-tag=TITLE file.flac
-LANG=en_US.88591 metaflac --set-tag=TITLE='Whoope! That'"'"'s Great' file.flac
-chmod -w file.flac
-@end example
-
-Note the need for shell quoting. The function @code{shell_quote()}
-does it. @code{SINGLE} is the one-character string @code{"'"} and
-@code{QSINGLE} is the three-character string @code{"\"'\""}:
-
-@example
-@c file eg/lib/shellquote.awk
-# shell_quote --- quote an argument for passing to the shell
-@c endfile
-@ignore
-@c file eg/lib/shellquote.awk
-#
-# Michael Brennan
-# brennan@@madronabluff.com
-# September 2014
-@c endfile
-@end ignore
-@c file eg/lib/shellquote.awk
-
-function shell_quote(s, # parameter
- SINGLE, QSINGLE, i, X, n, ret) # locals
-@{
- if (s == "")
- return "\"\""
-
- SINGLE = "\x27" # single quote
- QSINGLE = "\"\x27\""
- n = split(s, X, SINGLE)
-
- ret = SINGLE X[1] SINGLE
- for (i = 2; i <= n; i++)
- ret = ret QSINGLE SINGLE X[i] SINGLE
-
- return ret
-@}
-@c endfile
-@end example
-
-@node Isnumeric Function
-@subsection Checking Whether A Value Is Numeric
-
-A frequent programming question is how to ascertain whether a value is numeric.
-This can be solved by using this example function @code{isnumeric()}, which
-employs the trick of converting a string value to user input by using the
-@code{split()} function:
-
-@cindex @code{isnumeric()} user-defined function
-@cindex user-defined @subentry function @subentry @code{isnumeric()}
-@example
-@c file eg/lib/isnumeric.awk
-# isnumeric --- check whether a value is numeric
-
-function isnumeric(x, f)
-@{
- switch (typeof(x)) @{
- case "strnum":
- case "number":
- return 1
- case "string":
- return (split(x, f, " ") == 1) && (typeof(f[1]) == "strnum")
- default:
- return 0
- @}
-@}
-@c endfile
-@end example
-
-Please note that leading or trailing white space is disregarded in deciding
-whether a value is numeric or not, so if it matters to you, you may want
-to add an additional check for that.
-
-Traditionally, it has been recommended to check for numeric values using the
-test @samp{x+0 == x}. This function is superior in two ways: it will not
-report that unassigned variables contain numeric values; and it recognizes
-string values with numeric contents where @code{CONVFMT} does not yield
-the original string.
-On the other hand, it uses the @code{typeof()} function
-(@pxref{Type Functions}), which is specific to @command{gawk}.
-
-@node To CSV Function
-@subsection Producing CSV Data
-
-@cindex comma separated values (CSV) data @subentry generating CSV data
-@cindex CSV (comma separated values) data @subentry generating CSV data
-@command{gawk}'s @option{--csv} option causes @command{gawk}
-to process CSV data (@pxref{Comma Separated Fields}).
-
-But what if you have regular data that you want to output
-in CSV format? This @value{SECTION} provides functions for
-doing that.
-
-The first function, @code{tocsv()}, takes an array of data
-fields as input. The array should be indexed starting from one.
-The optional second parameter is the separator to use. If none
-is supplied, the default is a comma.
-
-The function takes care to quote fields that contain double
-quotes, newlines, or the separator character. It then builds
-up the final CSV record and returns it.
-
-@cindex @code{tocsv()} user-defined function
-@example
-@c file eg/lib/tocsv.awk
-# tocsv.awk --- convert data to CSV format
-@c endfile
-@ignore
-@c file eg/lib/tocsv.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# April 2023
-@c endfile
-@end ignore
-@c file eg/lib/tocsv.awk
-
-function tocsv(fields, sep, i, j, nfields, result)
-@{
- if (length(fields) == 0)
- return ""
-
- if (sep == "")
- sep = ","
- delete nfields
- for (i = 1; i in fields; i++) @{
- nfields[i] = fields[i]
- if (nfields[i] ~ /["\n]/ || index(nfields[i], sep) != 0) @{
- gsub(/"/, "\"\"", nfields[i]) # double up quotes
- nfields[i] = "\"" nfields[i] "\"" # wrap in quotes
- @}
- @}
-
- result = nfields[1]
- j = length(nfields)
- for (i = 2; i <= j; i++)
- result = result sep nfields[i]
-
- return result
-@}
-@c endfile
-@end example
-
-The next function, @code{tocsv_rec()} is a wrapper around
-@code{tocsv()}. Its intended use is for when you want to convert the
-current input record to CSV format. The function itself simply copies
-the fields into an array to pass to @code{tocsv()} which does the work.
-It accepts an optional separator character as its first parameter,
-which it simply passes on to @code{tocsv()}.
-
-@cindex @code{tocsv_rec()} user-defined function
-@example
-@c file eg/lib/tocsv.awk
-function tocsv_rec(sep, i, fields)
-@{
- delete fields
- for (i = 1; i <= NF; i++)
- fields[i] = $i
-
- return tocsv(fields, sep)
-@}
-@c endfile
-@end example
-
-@node Data File Management
-@section @value{DDF} Management
-
-@cindex files @subentry managing
-@cindex libraries of @command{awk} functions @subentry managing @subentry data
files
-@cindex functions @subentry library @subentry managing data files
-This @value{SECTION} presents functions that are useful for managing
-command-line @value{DF}s.
-
-@menu
-* Filetrans Function:: A function for handling data file transitions.
-* Rewind Function:: A function for rereading the current file.
-* File Checking:: Checking that data files are readable.
-* Empty Files:: Checking for zero-length files.
-* Ignoring Assigns:: Treating assignments as file names.
-@end menu
-
-@node Filetrans Function
-@subsection Noting @value{DDF} Boundaries
-
-@cindex files @subentry managing @subentry data file boundaries
-@cindex files @subentry initialization and cleanup
-The @code{BEGIN} and @code{END} rules are each executed exactly once, at
-the beginning and end of your @command{awk} program, respectively
-(@pxref{BEGIN/END}).
-We (the @command{gawk} authors) once had a user who mistakenly thought that the
-@code{BEGIN} rules were executed at the beginning of each @value{DF} and the
-@code{END} rules were executed at the end of each @value{DF}.
-
-When informed
-that this was not the case, the user requested that we add new special
-patterns to @command{gawk}, named @code{BEGIN_FILE} and @code{END_FILE}, that
-would have the desired behavior. He even supplied us the code to do so.
-
-Adding these special patterns to @command{gawk} wasn't necessary;
-the job can be done cleanly in @command{awk} itself, as illustrated
-by the following library program.
-It arranges to call two user-supplied functions, @code{beginfile()} and
-@code{endfile()}, at the beginning and end of each @value{DF}.
-Besides solving the problem in only nine(!) lines of code, it does so
-@emph{portably}; this works with any implementation of @command{awk}:
-
-@example
-# transfile.awk
-#
-# Give the user a hook for filename transitions
-#
-# The user must supply functions beginfile() and endfile()
-# that each take the name of the file being started or
-# finished, respectively.
-@c #
-@c # Arnold Robbins, arnold@@skeeve.com, Public Domain
-@c # January 1992
-
-FILENAME != _oldfilename @{
- if (_oldfilename != "")
- endfile(_oldfilename)
- _oldfilename = FILENAME
- beginfile(FILENAME)
-@}
-
-END @{ endfile(FILENAME) @}
-@end example
-
-This file must be loaded before the user's ``main'' program, so that the
-rule it supplies is executed first.
-
-This rule relies on @command{awk}'s @code{FILENAME} variable, which
-automatically changes for each new @value{DF}. The current @value{FN} is
-saved in a private variable, @code{_oldfilename}. If @code{FILENAME} does
-not equal @code{_oldfilename}, then a new @value{DF} is being processed and
-it is necessary to call @code{endfile()} for the old file. Because
-@code{endfile()} should only be called if a file has been processed, the
-program first checks to make sure that @code{_oldfilename} is not the null
-string. The program then assigns the current @value{FN} to
-@code{_oldfilename} and calls @code{beginfile()} for the file.
-Because, like all @command{awk} variables, @code{_oldfilename} is
-initialized to the null string, this rule executes correctly even for the
-first @value{DF}.
-
-The program also supplies an @code{END} rule to do the final processing for
-the last file. Because this @code{END} rule comes before any @code{END} rules
-supplied in the ``main'' program, @code{endfile()} is called first. Once
-again, the value of multiple @code{BEGIN} and @code{END} rules should be clear.
-
-@cindex @code{beginfile()} user-defined function
-@cindex user-defined @subentry function @subentry @code{beginfile()}
-@cindex @code{endfile()} user-defined function
-@cindex user-defined @subentry function @subentry @code{endfile()}
-If the same @value{DF} occurs twice in a row on the command line, then
-@code{endfile()} and @code{beginfile()} are not executed at the end of the
-first pass and at the beginning of the second pass.
-The following version solves the problem:
-
-@example
-@c file eg/lib/ftrans.awk
-# ftrans.awk --- handle datafile transitions
-#
-# user supplies beginfile() and endfile() functions
-@c endfile
-@ignore
-@c file eg/lib/ftrans.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# November 1992
-@c endfile
-@end ignore
-@c file eg/lib/ftrans.awk
-
-FNR == 1 @{
- if (_filename_ != "")
- endfile(_filename_)
- _filename_ = FILENAME
- beginfile(FILENAME)
-@}
-
-END @{ endfile(_filename_) @}
-@c endfile
-@end example
-
-@ref{Wc Program}
-shows how this library function can be used and
-how it simplifies writing the main program.
-
-@sidebar So Why Does @command{gawk} Have @code{BEGINFILE} and @code{ENDFILE}?
-
-You are probably wondering, if @code{beginfile()} and @code{endfile()}
-functions can do the job, why does @command{gawk} have
-@code{BEGINFILE} and @code{ENDFILE} patterns?
-
-Good question. Normally, if @command{awk} cannot open a file, this
-causes an immediate fatal error. In this case, there is no way for a
-user-defined function to deal with the problem, as the mechanism for
-calling it relies on the file being open and at the first record. Thus,
-the main reason for @code{BEGINFILE} is to give you a ``hook'' to catch
-files that cannot be processed. @code{ENDFILE} exists for symmetry,
-and because it provides an easy way to do per-file cleanup processing.
-For more information, refer to @ref{BEGINFILE/ENDFILE}.
-@end sidebar
-
-@node Rewind Function
-@subsection Rereading the Current File
-
-@cindex files @subentry reading
-Another request for a new built-in function was for a
-function that would make it possible to reread the current file.
-The requesting user didn't want to have to use @code{getline}
-(@pxref{Getline})
-inside a loop.
-
-However, as long as you are not in the @code{END} rule, it is
-quite easy to arrange to immediately close the current input file
-and then start over with it from the top.
-For lack of a better name, we'll call the function @code{rewind()}:
-
-@cindex @code{rewind()} user-defined function
-@cindex user-defined @subentry function @subentry @code{rewind()}
-@example
-@c file eg/lib/rewind.awk
-# rewind.awk --- rewind the current file and start over
-@c endfile
-@ignore
-@c file eg/lib/rewind.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# September 2000
-@c endfile
-@end ignore
-@c file eg/lib/rewind.awk
-
-function rewind( i)
-@{
- # shift remaining arguments up
- for (i = ARGC; i > ARGIND; i--)
- ARGV[i] = ARGV[i-1]
-
- # make sure gawk knows to keep going
- ARGC++
-
- # make current file next to get done
- ARGV[ARGIND+1] = FILENAME
-
- # do it
- nextfile
-@}
-@c endfile
-@end example
-
-The @code{rewind()} function relies on the @code{ARGIND} variable
-(@pxref{Auto-set}), which is specific to @command{gawk}. It also
-relies on the @code{nextfile} keyword (@pxref{Nextfile Statement}).
-Because of this, you should not call it from an @code{ENDFILE} rule.
-(This isn't necessary anyway, because @command{gawk} goes to the next
-file as soon as an @code{ENDFILE} rule finishes!)
-
-You need to be careful calling @code{rewind()}. You can end up
-causing infinite recursion if you don't pay attention. Here is an
-example use:
-
-@example
-$ @kbd{cat data}
-@print{} a
-@print{} b
-@print{} c
-@print{} d
-@print{} e
-
-$ cat @kbd{test.awk}
-@print{} FNR == 3 && ! rewound @{
-@print{} rewound = 1
-@print{} rewind()
-@print{} @}
-@print{}
-@print{} @{ print FILENAME, FNR, $0 @}
-
-$ @kbd{gawk -f rewind.awk -f test.awk data }
-@print{} data 1 a
-@print{} data 2 b
-@print{} data 1 a
-@print{} data 2 b
-@print{} data 3 c
-@group
-@print{} data 4 d
-@print{} data 5 e
-@end group
-@end example
-
-@node File Checking
-@subsection Checking for Readable @value{DDF}s
-
-@cindex troubleshooting @subentry readable data files
-@cindex readable data files, checking
-@cindex files @subentry skipping
-Normally, if you give @command{awk} a @value{DF} that isn't readable,
-it stops with a fatal error. There are times when you might want to
-just ignore such files and keep going.@footnote{The @code{BEGINFILE}
-special pattern (@pxref{BEGINFILE/ENDFILE}) provides an alternative
-mechanism for dealing with files that can't be opened. However, the
-code here provides a portable solution.} You can do this by prepending
-the following program to your @command{awk} program:
-
-@cindex @file{readable.awk} program
-@example
-@c file eg/lib/readable.awk
-# readable.awk --- library file to skip over unreadable files
-@c endfile
-@ignore
-@c file eg/lib/readable.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# October 2000
-# December 2010
-@c endfile
-@end ignore
-@c file eg/lib/readable.awk
-
-BEGIN @{
- for (i = 1; i < ARGC; i++) @{
- if (ARGV[i] ~ /^[a-zA-Z_][a-zA-Z0-9_]*=.*/ \
- || ARGV[i] == "-" || ARGV[i] == "/dev/stdin")
- continue # assignment or standard input
- else if ((getline junk < ARGV[i]) < 0) # unreadable
- delete ARGV[i]
- else
- close(ARGV[i])
- @}
-@}
-@c endfile
-@end example
-
-@cindex troubleshooting @subentry @code{getline} command
-This works, because the @code{getline} won't be fatal.
-Removing the element from @code{ARGV} with @code{delete}
-skips the file (because it's no longer in the list).
-See also @ref{ARGC and ARGV}.
-
-Because @command{awk} variable names only allow the English letters,
-the regular expression check purposely does not use character classes
-such as @samp{[:alpha:]} and @samp{[:alnum:]}
-(@pxref{Bracket Expressions}).
-
-@node Empty Files
-@subsection Checking for Zero-Length Files
-
-All known @command{awk} implementations silently skip over zero-length files.
-This is a by-product of @command{awk}'s implicit
-read-a-record-and-match-against-the-rules loop: when @command{awk}
-tries to read a record from an empty file, it immediately receives an
-end-of-file indication, closes the file, and proceeds on to the next
-command-line @value{DF}, @emph{without} executing any user-level
-@command{awk} program code.
-
-Using @command{gawk}'s @code{ARGIND} variable
-(@pxref{Built-in Variables}), it is possible to detect when an empty
-@value{DF} has been skipped. Similar to the library file presented
-in @ref{Filetrans Function}, the following library file calls a function named
-@code{zerofile()} that the user must provide. The arguments passed are
-the @value{FN} and the position in @code{ARGV} where it was found:
-
-@cindex @file{zerofile.awk} program
-@example
-@c file eg/lib/zerofile.awk
-# zerofile.awk --- library file to process empty input files
-@c endfile
-@ignore
-@c file eg/lib/zerofile.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# June 2003
-@c endfile
-@end ignore
-@c file eg/lib/zerofile.awk
-
-BEGIN @{ Argind = 0 @}
-
-ARGIND > Argind + 1 @{
- for (Argind++; Argind < ARGIND; Argind++)
- zerofile(ARGV[Argind], Argind)
-@}
-
-ARGIND != Argind @{ Argind = ARGIND @}
-
-END @{
- if (ARGIND > Argind)
- for (Argind++; Argind <= ARGIND; Argind++)
- zerofile(ARGV[Argind], Argind)
-@}
-@c endfile
-@end example
-
-The user-level variable @code{Argind} allows the @command{awk} program
-to track its progress through @code{ARGV}. Whenever the program detects
-that @code{ARGIND} is greater than @samp{Argind + 1}, it means that one or
-more empty files were skipped. The action then calls @code{zerofile()} for
-each such file, incrementing @code{Argind} along the way.
-
-The @samp{Argind != ARGIND} rule simply keeps @code{Argind} up to date
-in the normal case.
-
-Finally, the @code{END} rule catches the case of any empty files at
-the end of the command-line arguments. Note that the test in the
-condition of the @code{for} loop uses the @samp{<=} operator,
-not @samp{<}.
-
-@node Ignoring Assigns
-@subsection Treating Assignments as @value{FFN}s
-
-@cindex assignments as file names
-@cindex file names @subentry assignments as
-Occasionally, you might not want @command{awk} to process command-line
-variable assignments
-(@pxref{Assignment Options}).
-In particular, if you have a @value{FN} that contains an @samp{=} character,
-@command{awk} treats the @value{FN} as an assignment and does not process it.
-
-Some users have suggested an additional command-line option for @command{gawk}
-to disable command-line assignments. However, some simple programming with
-a library file does the trick:
-
-@cindex @file{noassign.awk} program
-@example
-@c file eg/lib/noassign.awk
-# noassign.awk --- library file to avoid the need for a
-# special option that disables command-line assignments
-@c endfile
-@ignore
-@c file eg/lib/noassign.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# October 1999
-@c endfile
-@end ignore
-@c file eg/lib/noassign.awk
-
-function disable_assigns(argc, argv, i)
-@{
- for (i = 1; i < argc; i++)
- if (argv[i] ~ /^[a-zA-Z_][a-zA-Z0-9_]*=.*/)
- argv[i] = ("./" argv[i])
-@}
-
-BEGIN @{
- if (No_command_assign)
- disable_assigns(ARGC, ARGV)
-@}
-@c endfile
-@end example
-
-You then run your program this way:
-
-@example
-awk -v No_command_assign=1 -f noassign.awk -f yourprog.awk *
-@end example
-
-The function works by looping through the arguments.
-It prepends @samp{./} to
-any argument that matches the form
-of a variable assignment, turning that argument into a @value{FN}.
-
-The use of @code{No_command_assign} allows you to disable command-line
-assignments at invocation time, by giving the variable a true value.
-When not set, it is initially zero (i.e., false), so the command-line arguments
-are left alone.
-
-@node Getopt Function
-@section Processing Command-Line Options
-
-@cindex libraries of @command{awk} functions @subentry command-line options
-@cindex functions @subentry library @subentry command-line options
-@cindex command line @subentry options @subentry processing
-@cindex options @subentry command-line @subentry processing
-@cindex functions @subentry library @subentry C library
-@cindex arguments @subentry processing
-Most utilities on POSIX-compatible systems take options on
-the command line that can be used to change the way a program behaves.
-@command{awk} is an example of such a program
-(@pxref{Options}).
-Often, options take @dfn{arguments} (i.e., data that the program needs to
-correctly obey the command-line option). For example, @command{awk}'s
-@option{-F} option requires a string to use as the field separator.
-The first occurrence on the command line of either @option{--} or a
-string that does not begin with @samp{-} ends the options.
-
-@cindex @code{getopt()} function (C library)
-@cindex C library functions @subentry @code{getopt()}
-Modern Unix systems provide a C function named @code{getopt()} for processing
-command-line arguments. The programmer provides a string describing the
-one-letter options. If an option requires an argument, it is followed in the
-string with a colon. @code{getopt()} is also passed the
-count and values of the command-line arguments and is called in a loop.
-@code{getopt()} processes the command-line arguments for option letters.
-Each time around the loop, it returns a single character representing the
-next option letter that it finds, or @samp{?} if it finds an invalid option.
-When it returns @minus{}1, there are no options left on the command line.
-
-When using @code{getopt()}, options that do not take arguments can be
-grouped together. Furthermore, options that take arguments require that the
-argument be present. The argument can immediately follow the option letter,
-or it can be a separate command-line argument.
-
-Given a hypothetical program that takes
-three command-line options, @option{-a}, @option{-b}, and @option{-c}, where
-@option{-b} requires an argument, all of the following are valid ways of
-invoking the program:
-
-@example
-prog -a -b foo -c data1 data2 data3
-prog -ac -bfoo -- data1 data2 data3
-prog -acbfoo data1 data2 data3
-@end example
-
-Notice that when the argument is grouped with its option, the rest of
-the argument is considered to be the option's argument.
-In this example, @option{-acbfoo} indicates that all of the
-@option{-a}, @option{-b}, and @option{-c} options were supplied,
-and that @samp{foo} is the argument to the @option{-b} option.
-
-@code{getopt()} provides four external variables that the programmer can use:
-
-@table @code
-@item optind
-The index in the argument value array (@code{argv}) where the first
-nonoption command-line argument can be found.
-
-@item optarg
-The string value of the argument to an option.
-
-@item opterr
-Usually @code{getopt()} prints an error message when it finds an invalid
-option. Setting @code{opterr} to zero disables this feature. (An
-application might want to print its own error message.)
-
-@item optopt
-The letter representing the command-line option.
-@end table
-
-The following C fragment shows how @code{getopt()} might process command-line
-arguments for @command{awk}:
-
-@example
-int
-main(int argc, char *argv[])
-@{
- @dots{}
- /* print our own message */
- opterr = 0;
- while ((c = getopt(argc, argv, "v:f:F:W:")) != -1) @{
- switch (c) @{
- case 'f': /* file */
- @dots{}
- break;
- case 'F': /* field separator */
- @dots{}
- break;
- case 'v': /* variable assignment */
- @dots{}
- break;
- case 'W': /* extension */
- @dots{}
- break;
- case '?':
- default:
- usage();
- break;
- @}
- @}
- @dots{}
-@}
-@end example
-
-The GNU project's version of the original Unix utilities popularized
-the use of long command line options. For example, @option{--help}
-in addition to @option{-h}. Arguments to long options are either provided
-as separate command line arguments (@samp{--source '@var{program-text}'})
-or separated from the option with an @samp{=} sign
-(@samp{--source='@var{program-text}'}).
-
-As a side point, @command{gawk} actually uses the GNU @code{getopt_long()}
-function to process both normal and GNU-style long options
-(@pxref{Options}).
-
-@cindex Minshall, Greg
-The abstraction provided by @code{getopt()} is very useful and is quite
-handy in @command{awk} programs as well. Following is an @command{awk}
-version of @code{getopt()} that accepts both short and long options.
-(Support for long options was supplied by Greg Minshall. We thank him.)
-
-This function highlights one of the
-greatest weaknesses in @command{awk}, which is that it is very poor at
-manipulating single characters. The function needs repeated calls to
-@code{substr()} in order to access individual characters
-(@pxref{String Functions}).@footnote{This
-function was written before @command{gawk} acquired the ability to
-split strings into single characters using @code{""} as the separator.
-We have left it alone, as using @code{substr()} is more portable.}
-
-The discussion that follows walks through the code a bit at a time:
-
-@cindex @code{getopt()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getopt()}
-@example
-@c file eg/lib/getopt.awk
-# getopt.awk --- Do C library getopt(3) function in awk
-# Also supports long options.
-@c endfile
-@ignore
-@c file eg/lib/getopt.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-#
-# Initial version: March, 1991
-# Revised: May, 1993
-# Long options added by Greg Minshall, January 2020
-@c endfile
-@end ignore
-@c file eg/lib/getopt.awk
-
-# External variables:
-# Optind -- index in ARGV of first nonoption argument
-# Optarg -- string value of argument to current option
-# Opterr -- if nonzero, print our own diagnostic
-# Optopt -- current option letter
-
-# Returns:
-# -1 at end of options
-# "?" for unrecognized option
-# <s> a string representing the current option
-
-# Private Data:
-# _opti -- index in multiflag option, e.g., -abc
-@c endfile
-@end example
-
-The function starts out with comments presenting
-a list of the global variables it uses,
-what the return values are, what they mean, and any global variables that
-are ``private'' to this library function. Such documentation is essential
-for any program, and particularly for library functions.
-
-The @code{getopt()} function first checks that it was indeed called with
-a string of options (the @code{options} parameter). If both
-@code{options} and @code{longoptions} have a zero length,
-@code{getopt()} immediately returns @minus{}1:
-
-@cindex @code{getopt()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getopt()}
-@example
-@c file eg/lib/getopt.awk
-function getopt(argc, argv, options, longopts, thisopt, i, j)
-@{
- if (length(options) == 0 && length(longopts) == 0)
- return -1 # no options given
-
-@group
- if (argv[Optind] == "--") @{ # all done
- Optind++
- _opti = 0
- return -1
-@end group
- @} else if (argv[Optind] !~ /^-[^:[:space:]]/) @{
- _opti = 0
- return -1
- @}
-@c endfile
-@end example
-
-The next thing to check for is the end of the options. A @option{--}
-ends the command-line options, as does any command-line argument that
-does not begin with a @samp{-} (unless it is an argument to a preceding
-option). @code{Optind} steps through
-the array of command-line arguments; it retains its value across calls
-to @code{getopt()}, because it is a global variable.
-
-The regular expression @code{@w{/^-[^:[:space:]/}}
-checks for a @samp{-} followed by anything
-that is not whitespace and not a colon.
-If the current command-line argument does not match this pattern,
-it is not an option, and it ends option processing.
-Now, we
-check to see if we are processing a short (single letter) option, or a
-long option (indicated by two dashes, e.g., @samp{--filename}). If it
-is a short option, we continue on:
-
-@example
-@c file eg/lib/getopt.awk
- if (argv[Optind] !~ /^--/) @{ # if this is a short option
- if (_opti == 0)
- _opti = 2
- thisopt = substr(argv[Optind], _opti, 1)
- Optopt = thisopt
- i = index(options, thisopt)
- if (i == 0) @{
- if (Opterr)
- printf("%c -- invalid option\n", thisopt) > "/dev/stderr"
- if (_opti >= length(argv[Optind])) @{
- Optind++
- _opti = 0
- @} else
- _opti++
- return "?"
- @}
-@c endfile
-@end example
-
-The @code{_opti} variable tracks the position in the current command-line
-argument (@code{argv[Optind]}). If multiple options are
-grouped together with one @samp{-} (e.g., @option{-abx}), it is necessary
-to return them to the user one at a time.
-
-If @code{_opti} is equal to zero, it is set to two, which is the index in
-the string of the next character to look at (we skip the @samp{-}, which
-is at position one). The variable @code{thisopt} holds the character,
-obtained with @code{substr()}. It is saved in @code{Optopt} for the main
-program to use.
-
-If @code{thisopt} is not in the @code{options} string, then it is an
-invalid option. If @code{Opterr} is nonzero, @code{getopt()} prints an error
-message on the standard error that is similar to the message from the C
-version of @code{getopt()}.
-
-Because the option is invalid, it is necessary to skip it and move on to the
-next option character. If @code{_opti} is greater than or equal to the
-length of the current command-line argument, it is necessary to move on
-to the next argument, so @code{Optind} is incremented and @code{_opti} is reset
-to zero. Otherwise, @code{Optind} is left alone and @code{_opti} is merely
-incremented.
-
-In any case, because the option is invalid, @code{getopt()} returns @code{"?"}.
-The main program can examine @code{Optopt} if it needs to know what the
-invalid option letter actually is. Continuing on:
-
-@example
-@c file eg/lib/getopt.awk
- if (substr(options, i + 1, 1) == ":") @{
- # get option argument
- if (length(substr(argv[Optind], _opti + 1)) > 0)
- Optarg = substr(argv[Optind], _opti + 1)
- else
- Optarg = argv[++Optind]
- _opti = 0
- @} else
- Optarg = ""
-@c endfile
-@end example
-
-If the option requires an argument, the option letter is followed by a colon
-in the @code{options} string. If there are remaining characters in the
-current command-line argument (@code{argv[Optind]}), then the rest of that
-string is assigned to @code{Optarg}. Otherwise, the next command-line
-argument is used (@samp{-xFOO} versus @samp{@w{-x FOO}}). In either case,
-@code{_opti} is reset to zero, because there are no more characters left to
-examine in the current command-line argument. Continuing:
-
-@example
-@c file eg/lib/getopt.awk
- if (_opti == 0 || _opti >= length(argv[Optind])) @{
- Optind++
- _opti = 0
- @} else
- _opti++
- return thisopt
-@c endfile
-@end example
-
-Finally, for a short option, if @code{_opti} is either zero or greater
-than the length of the current command-line argument, it means this
-element in @code{argv} is through being processed, so @code{Optind} is
-incremented to point to the next element in @code{argv}. If neither
-condition is true, then only @code{_opti} is incremented, so that the
-next option letter can be processed on the next call to @code{getopt()}.
-
-On the other hand, if the earlier test found that this was a long
-option, we take a different branch:
-
-@example
-@c file eg/lib/getopt.awk
- @} else @{
- j = index(argv[Optind], "=")
- if (j > 0)
- thisopt = substr(argv[Optind], 3, j - 3)
- else
- thisopt = substr(argv[Optind], 3)
- Optopt = thisopt
-@c endfile
-@end example
-
-First, we search this option for a possible embedded equal sign, as the
-specification of long options allows an argument to an option
-@samp{--someopt} to be specified as @samp{--someopt=answer} as well as
-@samp{@w{--someopt answer}}.
-
-@example
-@c file eg/lib/getopt.awk
- i = match(longopts, "(^|,)" thisopt "($|[,:])")
- if (i == 0) @{
- if (Opterr)
- printf("%s -- invalid option\n", thisopt) > "/dev/stderr"
- Optind++
- return "?"
- @}
-@c endfile
-@end example
-
-Next, we try to find the current option in @code{longopts}. The regular
-expression given to @code{match()}, @code{@w{"(^|,)" thisopt "($|[,:])"}},
-matches this option at the beginning of @code{longopts}, or at the
-beginning of a subsequent long option (the previous long option would
-have been terminated by a comma), and, in any case, either at the end of
-the @code{longopts} string (@samp{$}), or followed by a comma
-(separating this option from a subsequent option) or a colon (indicating
-this long option takes an argument (@samp{@w{[,:]}}).
-
-Using this regular expression, we check to see if the current option
-might possibly be in @code{longopts} (if @code{longopts} is not
-specified, this test will also fail). In case of an error, we possibly
-print an error message and then return @code{"?"}. Continuing on:
-
-@example
-@c file eg/lib/getopt.awk
- if (substr(longopts, i-1+RLENGTH, 1) == ":") @{
- if (j > 0)
- Optarg = substr(argv[Optind], j + 1)
- else
- Optarg = argv[++Optind]
- @} else
- Optarg = ""
-@c endfile
-@end example
-
-We now check to see if this option takes an argument and, if so, we set
-@code{Optarg} to the value of that argument (either a value after an
-equal sign specified on the command line, immediately adjoining the long
-option string, or as the next argument on the command line).
-
-@example
-@c file eg/lib/getopt.awk
- Optind++
- return thisopt
- @}
-@}
-@c endfile
-@end example
-
-We increase @code{Optind} (which we already increased once if a required
-argument was separated from its option by an equal sign), and return the
-long option (minus its leading dashes).
-
-The @code{BEGIN} rule initializes both @code{Opterr} and @code{Optind} to one.
-@code{Opterr} is set to one, because the default behavior is for
@code{getopt()}
-to print a diagnostic message upon seeing an invalid option. @code{Optind}
-is set to one, because there's no reason to look at the program name, which is
-in @code{ARGV[0]}:
-
-@example
-@c file eg/lib/getopt.awk
-BEGIN @{
- Opterr = 1 # default is to diagnose
- Optind = 1 # skip ARGV[0]
-
- # test program
- if (_getopt_test) @{
- _myshortopts = "ab:cd"
- _mylongopts = "longa,longb:,otherc,otherd"
-
- while ((_go_c = getopt(ARGC, ARGV, _myshortopts, _mylongopts)) != -1)
- printf("c = <%s>, Optarg = <%s>\n", _go_c, Optarg)
- printf("non-option arguments:\n")
- for (; Optind < ARGC; Optind++)
- printf("\tARGV[%d] = <%s>\n", Optind, ARGV[Optind])
- @}
-@}
-@c endfile
-@end example
-
-The rest of the @code{BEGIN} rule is a simple test program. Here are the
-results of some sample runs of the test program:
-
-@example
-$ @kbd{awk -f getopt.awk -v _getopt_test=1 -- -a -cbARG bax -x}
-@print{} c = <a>, Optarg = <>
-@print{} c = <c>, Optarg = <>
-@print{} c = <b>, Optarg = <ARG>
-@print{} non-option arguments:
-@print{} ARGV[3] = <bax>
-@print{} ARGV[4] = <-x>
-
-$ @kbd{awk -f getopt.awk -v _getopt_test=1 -- -a -x -- xyz abc}
-@print{} c = <a>, Optarg = <>
-@error{} x -- invalid option
-@print{} c = <?>, Optarg = <>
-@print{} non-option arguments:
-@print{} ARGV[4] = <xyz>
-@print{} ARGV[5] = <abc>
-
-$ @kbd{awk -f getopt.awk -v _getopt_test=1 -- -a \}
-> @kbd{--longa -b xx --longb=foo=bar --otherd --otherc arg1 arg2}
-@print{} c = <a>, Optarg = <>
-@print{} c = <longa>, Optarg = <>
-@print{} c = <b>, Optarg = <xx>
-@print{} c = <longb>, Optarg = <foo=bar>
-@print{} c = <otherd>, Optarg = <>
-@print{} c = <otherc>, Optarg = <>
-@print{} non-option arguments:
-@print{} ARGV[8] = <arg1>
-@print{} ARGV[9] = <arg2>
-@end example
-
-In all the runs, the first @option{--} terminates the arguments to
-@command{awk}, so that it does not try to interpret the @option{-a},
-etc., as its own options.
-
-@quotation NOTE
-After @code{getopt()} is through,
-user-level code must clear out all the elements of @code{ARGV} from 1
-to @code{Optind}, so that @command{awk} does not try to process the
-command-line options as @value{FN}s.
-@end quotation
-
-Using @samp{#!} with the @option{-E} option may help avoid
-conflicts between your program's options and @command{gawk}'s options,
-as @option{-E} causes @command{gawk} to abandon processing of
-further options
-(@pxref{Executable Scripts} and
-@ifnotdocbook
-@pxref{Options}).
-@end ifnotdocbook
-@ifdocbook
-@ref{Options}).
-@end ifdocbook
-
-Several of the sample programs presented in
-@ref{Sample Programs},
-use @code{getopt()} to process their arguments.
-
-@node Passwd Functions
-@section Reading the User Database
-
-@cindex libraries of @command{awk} functions @subentry user database, reading
-@cindex functions @subentry library @subentry user database, reading
-@cindex user database, reading
-@cindex database @subentry users, reading
-@cindex @code{PROCINFO} array
-The @code{PROCINFO} array
-(@pxref{Built-in Variables})
-provides access to the current user's real and effective user and group ID
-numbers, and, if available, the user's supplementary group set.
-However, because these are numbers, they do not provide very useful
-information to the average user. There needs to be some way to find the
-user information associated with the user and group ID numbers. This
-@value{SECTION} presents a suite of functions for retrieving information from
the
-user database. @xref{Group Functions}
-for a similar suite that retrieves information from the group database.
-
-@cindex @code{getpwent()} function (C library)
-@cindex C library functions @subentry @code{getpwent()}
-@cindex @code{getpwent()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getpwent()}
-@cindex users, information about @subentry retrieving
-@cindex login information
-@cindex account information
-@cindex password file
-@cindex files @subentry password
-The POSIX standard does not define the file where user information is
-kept. Instead, it provides the @code{<pwd.h>} header file
-and several C language subroutines for obtaining user information.
-The primary function is @code{getpwent()}, for ``get password entry.''
-The ``password'' comes from the original user database file,
-@file{/etc/passwd}, which stores user information along with the
-encrypted passwords (hence the name).
-
-@cindex @command{pwcat} program
-Although an @command{awk} program could simply read @file{/etc/passwd}
-directly, this file may not contain complete information about the
-system's set of users.@footnote{It is often the case that password
-information is stored in a network database.} To be sure you are able to
-produce a readable and complete version of the user database, it is necessary
-to write a small C program that calls @code{getpwent()}. @code{getpwent()}
-is defined as returning a pointer to a @code{struct passwd}. Each time it
-is called, it returns the next entry in the database. When there are
-no more entries, it returns @code{NULL}, the null pointer. When this
-happens, the C program should call @code{endpwent()} to close the database.
-Following is @command{pwcat}, a C program that ``cats'' the password database:
-
-@example
-@c file eg/lib/pwcat.c
-/*
- * pwcat.c
- *
- * Generate a printable version of the password database.
- */
-@c endfile
-@ignore
-@c file eg/lib/pwcat.c
-/*
- * Arnold Robbins, arnold@@skeeve.com, May 1993
- * Public Domain
- * December 2010, move to ANSI C definition for main().
- */
-
-#if HAVE_CONFIG_H
-#include <config.h>
-#endif
-
-@c endfile
-@end ignore
-@c file eg/lib/pwcat.c
-#include <stdio.h>
-#include <pwd.h>
-
-@c endfile
-@ignore
-@c file eg/lib/pwcat.c
-#if defined (STDC_HEADERS)
-#include <stdlib.h>
-#endif
-
-@c endfile
-@end ignore
-@c file eg/lib/pwcat.c
-int
-main(int argc, char **argv)
-@{
- struct passwd *p;
-
- while ((p = getpwent()) != NULL)
-@c endfile
-@ignore
-@c file eg/lib/pwcat.c
-#ifdef HAVE_STRUCT_PASSWD_PW_PASSWD
-@c endfile
-@end ignore
-@c file eg/lib/pwcat.c
- printf("%s:%s:%ld:%ld:%s:%s:%s\n",
- p->pw_name, p->pw_passwd, (long) p->pw_uid,
- (long) p->pw_gid, p->pw_gecos, p->pw_dir, p->pw_shell);
-@c endfile
-@ignore
-@c file eg/lib/pwcat.c
-#else
- printf("%s:*:%ld:%ld:%s:%s\n",
- p->pw_name, (long) p->pw_uid,
- (long) p->pw_gid, p->pw_dir, p->pw_shell);
-#endif
-@c endfile
-@end ignore
-@c file eg/lib/pwcat.c
-
- endpwent();
- return 0;
-@}
-@c endfile
-@end example
-
-If you don't understand C, don't worry about it.
-The output from @command{pwcat} is the user database, in the traditional
-@file{/etc/passwd} format of colon-separated fields. The fields are:
-
-@table @asis
-@item Login name
-The user's login name.
-
-@item Encrypted password
-The user's encrypted password. This may not be available on some systems.
-
-@item User-ID
-The user's numeric user ID number.
-(On some systems, it's a C @code{long}, and not an @code{int}. Thus,
-we cast it to @code{long} for all cases.)
-
-@item Group-ID
-The user's numeric group ID number.
-(Similar comments about @code{long} versus @code{int} apply here.)
-
-@item Full name
-The user's full name, and perhaps other information associated with the
-user.
-
-@item Home directory
-The user's login (or ``home'') directory (familiar to shell programmers as
-@code{$HOME}).
-
-@item Login shell
-The program that is run when the user logs in. This is usually a
-shell, such as Bash.
-@end table
-
-A few lines representative of @command{pwcat}'s output are as follows:
-
-@cindex Jacobs, Andrew
-@cindex Robbins @subentry Arnold
-@cindex Robbins @subentry Miriam
-@example
-$ @kbd{pwcat}
-@print{} root:x:0:1:Operator:/:/bin/sh
-@print{} nobody:*:65534:65534::/:
-@print{} daemon:*:1:1::/:
-@print{} sys:*:2:2::/:/bin/csh
-@print{} bin:*:3:3::/bin:
-@print{} arnold:xyzzy:2076:10:Arnold Robbins:/home/arnold:/bin/sh
-@print{} miriam:yxaay:112:10:Miriam Robbins:/home/miriam:/bin/sh
-@print{} andy:abcca2:113:10:Andy Jacobs:/home/andy:/bin/sh
-@dots{}
-@end example
-
-With that introduction, following is a group of functions for getting user
-information. There are several functions here, corresponding to the C
-functions of the same names:
-
-@cindex @code{_pw_init()} user-defined function
-@cindex user-defined @subentry function @subentry @code{_pw_init()}
-@example
-@c file eg/lib/passwdawk.in
-# passwd.awk --- access password file information
-@c endfile
-@ignore
-@c file eg/lib/passwdawk.in
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised October 2000
-# Revised December 2010
-@c endfile
-@end ignore
-@c file eg/lib/passwdawk.in
-
-BEGIN @{
- # tailor this to suit your system
- _pw_awklib = "/usr/local/libexec/awk/"
-@}
-
-function _pw_init( oldfs, oldrs, olddol0, pwcat, using_fw, using_fpat)
-@{
- if (_pw_inited)
- return
-
- oldfs = FS
- oldrs = RS
- olddol0 = $0
- using_fw = (PROCINFO["FS"] == "FIELDWIDTHS")
- using_fpat = (PROCINFO["FS"] == "FPAT")
- FS = ":"
- RS = "\n"
-
- pwcat = _pw_awklib "pwcat"
- while ((pwcat | getline) > 0) @{
- _pw_byname[$1] = $0
- _pw_byuid[$3] = $0
- _pw_bycount[++_pw_total] = $0
- @}
- close(pwcat)
- _pw_count = 0
- _pw_inited = 1
- FS = oldfs
- if (using_fw)
- FIELDWIDTHS = FIELDWIDTHS
- else if (using_fpat)
- FPAT = FPAT
- RS = oldrs
- $0 = olddol0
-@}
-@c endfile
-@end example
-
-@cindex @code{BEGIN} pattern @subentry @code{pwcat} program
-The @code{BEGIN} rule sets a private variable to the directory where
-@command{pwcat} is stored. Because it is used to help out an @command{awk}
library
-routine, we have chosen to put it in @file{/usr/local/libexec/awk};
-however, you might want it to be in a different directory on your system.
-
-The function @code{_pw_init()} fills three copies of the user information
-into three associative arrays. The arrays are indexed by username
-(@code{_pw_byname}), by user ID number (@code{_pw_byuid}), and by order of
-occurrence (@code{_pw_bycount}).
-The variable @code{_pw_inited} is used for efficiency, as @code{_pw_init()}
-needs to be called only once.
-
-@cindex @code{PROCINFO} array @subentry testing the field splitting
-@cindex @code{getline} command @subentry @code{_pw_init()} function
-Because this function uses @code{getline} to read information from
-@command{pwcat}, it first saves the values of @code{FS}, @code{RS}, and
@code{$0}.
-It notes in the variable @code{using_fw} whether field splitting
-with @code{FIELDWIDTHS} is in effect or not.
-Doing so is necessary, as these functions could be called
-from anywhere within a user's program, and the user may have his
-or her own way of splitting records and fields.
-This makes it possible to restore the correct
-field-splitting mechanism later. The test can only be true for
-@command{gawk}. It is false if using @code{FS} or @code{FPAT},
-or on some other @command{awk} implementation.
-
-The code that checks for using @code{FPAT}, using @code{using_fpat}
-and @code{PROCINFO["FS"]}, is similar.
-
-The main part of the function uses a loop to read database lines, split
-the lines into fields, and then store the lines into each array as necessary.
-When the loop is done, @code{@w{_pw_init()}} cleans up by closing the pipeline,
-setting @code{@w{_pw_inited}} to one, and restoring @code{FS}
-(and @code{FIELDWIDTHS} or @code{FPAT}
-if necessary), @code{RS}, and @code{$0}.
-The use of @code{@w{_pw_count}} is explained shortly.
-
-@cindex @code{getpwnam()} function (C library)
-@cindex C library functions @subentry @code{getpwnam()}
-The @code{getpwnam()} function takes a username as a string argument. If that
-user is in the database, it returns the appropriate line. Otherwise, it
-relies on the array reference to a nonexistent
-element to create the element with the null string as its value:
-
-@cindex @code{getpwnam()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getpwnam()}
-@example
-@group
-@c file eg/lib/passwdawk.in
-function getpwnam(name)
-@{
- _pw_init()
- return _pw_byname[name]
-@}
-@c endfile
-@end group
-@end example
-
-@cindex @code{getpwuid()} function (C library)
-@cindex C library functions @subentry @code{getpwuid()}
-Similarly, the @code{getpwuid()} function takes a user ID number
-argument. If that user number is in the database, it returns the
-appropriate line. Otherwise, it returns the null string:
-
-@cindex @code{getpwuid()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getpwuid()}
-@example
-@c file eg/lib/passwdawk.in
-function getpwuid(uid)
-@{
- _pw_init()
- return _pw_byuid[uid]
-@}
-@c endfile
-@end example
-
-@cindex @code{getpwent()} function (C library)
-@cindex C library functions @subentry @code{getpwent()}
-The @code{getpwent()} function simply steps through the database, one entry at
-a time. It uses @code{_pw_count} to track its current position in the
-@code{_pw_bycount} array:
-
-@cindex @code{getpwent()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getpwent()}
-@example
-@c file eg/lib/passwdawk.in
-function getpwent()
-@{
- _pw_init()
- if (_pw_count < _pw_total)
- return _pw_bycount[++_pw_count]
- return ""
-@}
-@c endfile
-@end example
-
-@cindex @code{endpwent()} function (C library)
-@cindex C library functions @subentry @code{endpwent()}
-The @code{@w{endpwent()}} function resets @code{@w{_pw_count}} to zero, so that
-subsequent calls to @code{getpwent()} start over again:
-
-@cindex @code{endpwent()} user-defined function
-@cindex user-defined @subentry function @subentry @code{endpwent()}
-@example
-@c file eg/lib/passwdawk.in
-function endpwent()
-@{
- _pw_count = 0
-@}
-@c endfile
-@end example
-
-A conscious design decision in this suite is that each subroutine calls
-@code{@w{_pw_init()}} to initialize the database arrays.
-The overhead of running
-a separate process to generate the user database, and the I/O to scan it,
-are only incurred if the user's main program actually calls one of these
-functions. If this library file is loaded along with a user's program, but
-none of the routines are ever called, then there is no extra runtime overhead.
-(The alternative is move the body of @code{@w{_pw_init()}} into a
-@code{BEGIN} rule, which always runs @command{pwcat}. This simplifies the
-code but runs an extra process that may never be needed.)
-
-In turn, calling @code{_pw_init()} is not too expensive, because the
-@code{_pw_inited} variable keeps the program from reading the data more than
-once. If you are worried about squeezing every last cycle out of your
-@command{awk} program, the check of @code{_pw_inited} could be moved out of
-@code{_pw_init()} and duplicated in all the other functions. In practice,
-this is not necessary, as most @command{awk} programs are I/O-bound,
-and such a change would clutter up the code.
-
-The @command{id} program in @ref{Id Program}
-uses these functions.
-
-@node Group Functions
-@section Reading the Group Database
-
-@cindex libraries of @command{awk} functions @subentry group database, reading
-@cindex functions @subentry library @subentry group database, reading
-@cindex group database, reading
-@cindex database @subentry group, reading
-@cindex @code{PROCINFO} array @subentry group membership and
-@cindex @code{getgrent()} function (C library)
-@cindex C library functions @subentry @code{getgrent()}
-@cindex @code{getgrent()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getgrent()}
-@cindex groups, information about
-@cindex account information
-@cindex group file
-@cindex files @subentry group
-Much of the discussion presented in
-@ref{Passwd Functions}
-applies to the group database as well. Although there has traditionally
-been a well-known file (@file{/etc/group}) in a well-known format, the POSIX
-standard only provides a set of C library routines
-(@code{<grp.h>} and @code{getgrent()})
-for accessing the information.
-Even though this file may exist, it may not have
-complete information. Therefore, as with the user database, it is necessary
-to have a small C program that generates the group database as its output.
-@command{grcat}, a C program that ``cats'' the group database,
-is as follows:
-
-@cindex @command{grcat} program
-@example
-@c file eg/lib/grcat.c
-/*
- * grcat.c
- *
- * Generate a printable version of the group database.
- */
-@c endfile
-@ignore
-@c file eg/lib/grcat.c
-/*
- * Arnold Robbins, arnold@@skeeve.com, May 1993
- * Public Domain
- * December 2010, move to ANSI C definition for main().
- */
-
-#if HAVE_CONFIG_H
-#include <config.h>
-#endif
-
-#if defined (STDC_HEADERS)
-#include <stdlib.h>
-#endif
-
-#ifndef HAVE_GETGRENT
-int main() { return 0; }
-#else
-@c endfile
-@end ignore
-@c file eg/lib/grcat.c
-#include <stdio.h>
-#include <grp.h>
-
-int
-main(int argc, char **argv)
-@{
- struct group *g;
- int i;
-
- while ((g = getgrent()) != NULL) @{
-@c endfile
-@ignore
-@c file eg/lib/grcat.c
-#ifdef HAVE_STRUCT_GROUP_GR_PASSWD
-@c endfile
-@end ignore
-@c file eg/lib/grcat.c
- printf("%s:%s:%ld:", g->gr_name, g->gr_passwd,
- (long) g->gr_gid);
-@c endfile
-@ignore
-@c file eg/lib/grcat.c
-#else
- printf("%s:*:%ld:", g->gr_name, (long) g->gr_gid);
-#endif
-@c endfile
-@end ignore
-@c file eg/lib/grcat.c
- for (i = 0; g->gr_mem[i] != NULL; i++) @{
- printf("%s", g->gr_mem[i]);
-@group
- if (g->gr_mem[i+1] != NULL)
- putchar(',');
- @}
-@end group
- putchar('\n');
- @}
- endgrent();
- return 0;
-@}
-@c endfile
-@ignore
-@c file eg/lib/grcat.c
-#endif /* HAVE_GETGRENT */
-@c endfile
-@end ignore
-@end example
-
-Each line in the group database represents one group. The fields are
-separated with colons and represent the following information:
-
-@table @asis
-@item Group Name
-The group's name.
-
-@item Group Password
-The group's encrypted password. In practice, this field is never used;
-it is usually empty or set to @samp{*}.
-
-@item Group ID Number
-The group's numeric group ID number;
-the association of name to number must be unique within the file.
-(On some systems it's a C @code{long}, and not an @code{int}. Thus,
-we cast it to @code{long} for all cases.)
-
-@item Group Member List
-A comma-separated list of usernames. These users are members of the group.
-Modern Unix systems allow users to be members of several groups
-simultaneously. If your system does, then there are elements
-@code{"group1"} through @code{"group@var{N}"} in @code{PROCINFO}
-for those group ID numbers.
-(Note that @code{PROCINFO} is a @command{gawk} extension;
-@pxref{Built-in Variables}.)
-@end table
-
-Here is what running @command{grcat} might produce:
-
-@example
-$ @kbd{grcat}
-@print{} wheel:*:0:arnold
-@print{} nogroup:*:65534:
-@print{} daemon:*:1:
-@print{} kmem:*:2:
-@print{} staff:*:10:arnold,miriam,andy
-@print{} other:*:20:
-@dots{}
-@end example
-
-Here are the functions for obtaining information from the group database.
-There are several, modeled after the C library functions of the same names:
-
-@cindex @code{getline} command @subentry @code{_gr_init()} user-defined
function
-@cindex @code{_gr_init()} user-defined function
-@cindex user-defined @subentry function @subentry @code{_gr_init()}
-@example
-@c file eg/lib/groupawk.in
-# group.awk --- functions for dealing with the group file
-@c endfile
-@ignore
-@c file eg/lib/groupawk.in
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised October 2000
-# Revised December 2010
-@c endfile
-@end ignore
-@c line break on _gr_init for smallbook
-@c file eg/lib/groupawk.in
-
-BEGIN @{
- # Change to suit your system
- _gr_awklib = "/usr/local/libexec/awk/"
-@}
-
-function _gr_init( oldfs, oldrs, olddol0, grcat,
- using_fw, using_fpat, n, a, i)
-@{
- if (_gr_inited)
- return
-
- oldfs = FS
- oldrs = RS
- olddol0 = $0
- using_fw = (PROCINFO["FS"] == "FIELDWIDTHS")
- using_fpat = (PROCINFO["FS"] == "FPAT")
- FS = ":"
- RS = "\n"
-
- grcat = _gr_awklib "grcat"
- while ((grcat | getline) > 0) @{
- if ($1 in _gr_byname)
- _gr_byname[$1] = _gr_byname[$1] "," $4
- else
- _gr_byname[$1] = $0
- if ($3 in _gr_bygid)
- _gr_bygid[$3] = _gr_bygid[$3] "," $4
- else
- _gr_bygid[$3] = $0
-
- n = split($4, a, "[ \t]*,[ \t]*")
- for (i = 1; i <= n; i++)
- if (a[i] in _gr_groupsbyuser)
- _gr_groupsbyuser[a[i]] = _gr_groupsbyuser[a[i]] " " $1
- else
- _gr_groupsbyuser[a[i]] = $1
-
- _gr_bycount[++_gr_count] = $0
- @}
- close(grcat)
- _gr_count = 0
- _gr_inited++
- FS = oldfs
- if (using_fw)
- FIELDWIDTHS = FIELDWIDTHS
- else if (using_fpat)
- FPAT = FPAT
- RS = oldrs
- $0 = olddol0
-@}
-@c endfile
-@end example
-
-The @code{BEGIN} rule sets a private variable to the directory where
-@command{grcat} is stored. Because it is used to help out an @command{awk}
library
-routine, we have chosen to put it in @file{/usr/local/libexec/awk}. You might
-want it to be in a different directory on your system.
-
-These routines follow the same general outline as the user database routines
-(@pxref{Passwd Functions}).
-The @code{@w{_gr_inited}} variable is used to
-ensure that the database is scanned no more than once.
-The @code{@w{_gr_init()}} function first saves @code{FS},
-@code{RS}, and
-@code{$0}, and then sets @code{FS} and @code{RS} to the correct values for
-scanning the group information.
-It also takes care to note whether @code{FIELDWIDTHS} or @code{FPAT}
-is being used, and to restore the appropriate field-splitting mechanism.
-
-The group information is stored in several associative arrays.
-The arrays are indexed by group name (@code{@w{_gr_byname}}), by group ID
number
-(@code{@w{_gr_bygid}}), and by position in the database
(@code{@w{_gr_bycount}}).
-There is an additional array indexed by username (@code{@w{_gr_groupsbyuser}}),
-which is a space-separated list of groups to which each user belongs.
-
-Unlike in the user database, it is possible to have multiple records in the
-database for the same group. This is common when a group has a large number
-of members. A pair of such entries might look like the following:
-
-@example
-tvpeople:*:101:johnny,jay,arsenio
-tvpeople:*:101:david,conan,tom,joan
-@end example
-
-For this reason, @code{_gr_init()} looks to see if a group name or
-group ID number is already seen. If so, the usernames are
-simply concatenated onto the previous list of users.@footnote{There is a
-subtle problem with the code just presented. Suppose that
-the first time there were no names. This code adds the names with
-a leading comma. It also doesn't check that there is a @code{$4}.}
-
-Finally, @code{_gr_init()} closes the pipeline to @command{grcat}, restores
-@code{FS} (and @code{FIELDWIDTHS} or @code{FPAT}, if necessary), @code{RS},
and @code{$0},
-initializes @code{_gr_count} to zero
-(it is used later), and makes @code{_gr_inited} nonzero.
-
-@cindex @code{getgrnam()} function (C library)
-@cindex C library functions @subentry @code{getgrnam()}
-The @code{getgrnam()} function takes a group name as its argument, and if that
-group exists, it is returned.
-Otherwise, it
-relies on the array reference to a nonexistent
-element to create the element with the null string as its value:
-
-@cindex @code{getgrnam()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getgrnam()}
-@example
-@c file eg/lib/groupawk.in
-function getgrnam(group)
-@{
- _gr_init()
- return _gr_byname[group]
-@}
-@c endfile
-@end example
-
-@cindex @code{getgrgid()} function (C library)
-@cindex C library functions @subentry @code{getgrgid()}
-The @code{getgrgid()} function is similar; it takes a numeric group ID and
-looks up the information associated with that group ID:
-
-@cindex @code{getgrgid()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getgrgid()}
-@example
-@c file eg/lib/groupawk.in
-function getgrgid(gid)
-@{
- _gr_init()
- return _gr_bygid[gid]
-@}
-@c endfile
-@end example
-
-@cindex @code{getgruser()} function (C library)
-@cindex C library functions @subentry @code{getgruser()}
-The @code{getgruser()} function does not have a C counterpart. It takes a
-username and returns the list of groups that have the user as a member:
-
-@cindex @code{getgruser()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getgruser()}
-@example
-@c file eg/lib/groupawk.in
-function getgruser(user)
-@{
- _gr_init()
- return _gr_groupsbyuser[user]
-@}
-@c endfile
-@end example
-
-@cindex @code{getgrent()} function (C library)
-@cindex C library functions @subentry @code{getgrent()}
-The @code{getgrent()} function steps through the database one entry at a time.
-It uses @code{_gr_count} to track its position in the list:
-
-@cindex @code{getgrent()} user-defined function
-@cindex user-defined @subentry function @subentry @code{getgrent()}
-@example
-@c file eg/lib/groupawk.in
-function getgrent()
-@{
- _gr_init()
- if (++_gr_count in _gr_bycount)
- return _gr_bycount[_gr_count]
-@group
- return ""
-@}
-@end group
-@c endfile
-@end example
-
-@cindex @code{endgrent()} function (C library)
-@cindex C library functions @subentry @code{endgrent()}
-The @code{endgrent()} function resets @code{_gr_count} to zero so that
@code{getgrent()} can
-start over again:
-
-@cindex @code{endgrent()} user-defined function
-@cindex user-defined @subentry function @subentry @code{endgrent()}
-@example
-@c file eg/lib/groupawk.in
-function endgrent()
-@{
- _gr_count = 0
-@}
-@c endfile
-@end example
-
-As with the user database routines, each function calls @code{_gr_init()} to
-initialize the arrays. Doing so only incurs the extra overhead of running
-@command{grcat} if these functions are used (as opposed to moving the body of
-@code{_gr_init()} into a @code{BEGIN} rule).
-
-Most of the work is in scanning the database and building the various
-associative arrays. The functions that the user calls are themselves very
-simple, relying on @command{awk}'s associative arrays to do work.
-
-The @command{id} program in @ref{Id Program}
-uses these functions.
-
-@node Walking Arrays
-@section Traversing Arrays of Arrays
-
-@ref{Arrays of Arrays} described how @command{gawk}
-provides arrays of arrays. In particular, any element of
-an array may be either a scalar or another array. The
-@code{isarray()} function (@pxref{Type Functions})
-lets you distinguish an array
-from a scalar.
-The following function, @code{walk_array()}, recursively traverses
-an array, printing the element indices and values.
-You call it with the array and a string representing the name
-of the array:
-
-@cindex @code{walk_array()} user-defined function
-@cindex user-defined @subentry function @subentry @code{walk_array()}
-@example
-@c file eg/lib/walkarray.awk
-function walk_array(arr, name, i)
-@{
- for (i in arr) @{
- if (isarray(arr[i]))
- walk_array(arr[i], (name "[" i "]"))
- else
- printf("%s[%s] = %s\n", name, i, arr[i])
- @}
-@}
-@c endfile
-@end example
-
-@noindent
-It works by looping over each element of the array. If any given
-element is itself an array, the function calls itself recursively,
-passing the subarray and a new string representing the current index.
-Otherwise, the function simply prints the element's name, index, and value.
-Here is a main program to demonstrate:
-
-@example
-BEGIN @{
- a[1] = 1
- a[2][1] = 21
- a[2][2] = 22
- a[3] = 3
- a[4][1][1] = 411
- a[4][2] = 42
-
- walk_array(a, "a")
-@}
-@end example
-
-When run, the program produces the following output:
-
-@example
-$ @kbd{gawk -f walk_array.awk}
-@print{} a[1] = 1
-@print{} a[2][1] = 21
-@print{} a[2][2] = 22
-@print{} a[3] = 3
-@print{} a[4][1][1] = 411
-@print{} a[4][2] = 42
-@end example
-
-The function just presented simply prints the
-name and value of each scalar array element. However, it is easy to
-generalize it, by passing in the name of a function to call
-when walking an array. The modified function looks like this:
-
-@example
-@c file eg/lib/processarray.awk
-function process_array(arr, name, process, do_arrays, i, new_name)
-@{
- for (i in arr) @{
- new_name = (name "[" i "]")
- if (isarray(arr[i])) @{
- if (do_arrays)
- @@process(new_name, arr[i])
- process_array(arr[i], new_name, process, do_arrays)
- @} else
- @@process(new_name, arr[i])
- @}
-@}
-@c endfile
-@end example
-
-The arguments are as follows:
-
-@table @code
-@item arr
-The array.
-
-@item name
-The name of the array (a string).
-
-@item process
-The name of the function to call.
-
-@item do_arrays
-If this is true, the function can handle elements that are subarrays.
-@end table
-
-If subarrays are to be processed, that is done before walking them further.
-
-When run with the following scaffolding, the function produces the same
-results as does the earlier version of @code{walk_array()}:
-
-@example
-BEGIN @{
- a[1] = 1
- a[2][1] = 21
- a[2][2] = 22
- a[3] = 3
- a[4][1][1] = 411
- a[4][2] = 42
-
- process_array(a, "a", "do_print", 0)
-@}
-
-function do_print(name, element)
-@{
- printf "%s = %s\n", name, element
-@}
-@end example
-
-@node Library Functions Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Reading programs is an excellent way to learn Good Programming.
-The functions and programs provided in this @value{CHAPTER} and the next
-are intended to serve that purpose.
-
-@item
-When writing general-purpose library functions, put some thought into how
-to name any global variables so that they won't conflict with variables
-from a user's program.
-
-@item
-The functions presented here fit into the following categories:
-
-@c nested list
-@table @asis
-@item General problems
-Number-to-string conversion, testing assertions, rounding, random number
-generation, converting characters to numbers, joining strings, getting
-easily usable time-of-day information, and reading a whole file in
-one shot
-
-@item Managing @value{DF}s
-Noting @value{DF} boundaries, rereading the current file, checking for
-readable files, checking for zero-length files, and treating assignments
-as @value{FN}s
-
-@item Processing command-line options
-An @command{awk} version of the standard C @code{getopt()} function
-
-@item Reading the user and group databases
-Two sets of routines that parallel the C library versions
-
-@item Traversing arrays of arrays
-Two functions that traverse an array of arrays to any depth
-@end table
-@c end nested list
-
-@end itemize
-
-@c EXCLUDE START
-@node Library Exercises
-@section Exercises
-
-@enumerate
-@item
-In @ref{Empty Files}, we presented the @file{zerofile.awk} program,
-which made use of @command{gawk}'s @code{ARGIND} variable. Can this
-problem be solved without relying on @code{ARGIND}? If so, how?
-
-@ignore
-# zerofile2.awk --- same thing, portably
-
-BEGIN @{
- ARGIND = Argind = 0
- for (i = 1; i < ARGC; i++)
- Fnames[ARGV[i]]++
-
-@}
-FNR == 1 @{
- while (ARGV[ARGIND] != FILENAME)
- ARGIND++
- Seen[FILENAME]++
- if (Seen[FILENAME] == Fnames[FILENAME])
- do
- ARGIND++
- while (ARGV[ARGIND] != FILENAME)
-@}
-ARGIND > Argind + 1 @{
- for (Argind++; Argind < ARGIND; Argind++)
- zerofile(ARGV[Argind], Argind)
-@}
-ARGIND != Argind @{
- Argind = ARGIND
-@}
-END @{
- if (ARGIND < ARGC - 1)
- ARGIND = ARGC - 1
- if (ARGIND > Argind)
- for (Argind++; Argind <= ARGIND; Argind++)
- zerofile(ARGV[Argind], Argind)
-@}
-@end ignore
-
-@item
-As a related challenge, revise that code to handle the case where
-an intervening value in @code{ARGV} is a variable assignment.
-
-@ignore
-@c June 13 2015: Antonio points out that this is answered in the text. Ooops.
-@item
-@ref{Walking Arrays} presented a function that walked a multidimensional
-array to print it out. However, walking an array and processing
-each element is a general-purpose operation. Generalize the
-@code{walk_array()} function by adding an additional parameter named
-@code{process}.
-
-Then, inside the loop, instead of printing the array element's index and
-value, use the indirect function call syntax (@pxref{Indirect Calls})
-on @code{process}, passing it the index and the value.
-
-When calling @code{walk_array()}, you would pass the name of a
-user-defined function that expects to receive an index and a value,
-and then processes the element.
-
-Test your new version by printing the array; you should end up with
-output identical to that of the original version.
-@end ignore
-
-@end enumerate
-@c EXCLUDE END
-
-
-@node Sample Programs
-@chapter Practical @command{awk} Programs
-@cindex @command{awk} programs @subentry examples of
-
-@c FULLXREF ON
-@ref{Library Functions},
-presents the idea that reading programs in a language contributes to
-learning that language. This @value{CHAPTER} continues that theme,
-presenting a potpourri of @command{awk} programs for your reading
-enjoyment.
-@c FULLXREF OFF
-@ifnotinfo
-There are three @value{SECTION}s.
-The first describes how to run the programs presented
-in this @value{CHAPTER}.
-
-The second presents @command{awk}
-versions of several common POSIX utilities.
-These are programs that you are hopefully already familiar with,
-and therefore whose problems are understood.
-By reimplementing these programs in @command{awk},
-you can focus on the @command{awk}-related aspects of solving
-the programming problems.
-
-The third is a grab bag of interesting programs.
-These solve a number of different data-manipulation and management
-problems. Many of the programs are short, which emphasizes @command{awk}'s
-ability to do a lot in just a few lines of code.
-@end ifnotinfo
-
-Many of these programs use library functions presented in
-@ref{Library Functions}.
-
-@menu
-* Running Examples:: How to run these examples.
-* Clones:: Clones of common utilities.
-* Miscellaneous Programs:: Some interesting @command{awk} programs.
-* Programs Summary:: Summary of programs.
-* Programs Exercises:: Exercises.
-@end menu
-
-@node Running Examples
-@section Running the Example Programs
-
-To run a given program, you would typically do something like this:
-
-@example
-awk -f @var{program} -- @var{options} @var{files}
-@end example
-
-@noindent
-Here, @var{program} is the name of the @command{awk} program (such as
-@file{cut.awk}), @var{options} are any command-line options for the
-program that start with a @samp{-}, and @var{files} are the actual @value{DF}s.
-
-If your system supports the @samp{#!} executable interpreter mechanism
-(@pxref{Executable Scripts}),
-you can instead run your program directly:
-
-@example
-cut.awk -c1-8 myfiles > results
-@end example
-
-If your @command{awk} is not @command{gawk}, you may instead need to use this:
-
-@example
-cut.awk -- -c1-8 myfiles > results
-@end example
-
-@node Clones
-@section Reinventing Wheels for Fun and Profit
-@cindex POSIX @subentry programs, implementing in @command{awk}
-
-This @value{SECTION} presents a number of POSIX utilities implemented in
-@command{awk}. Reinventing these programs in @command{awk} is often enjoyable,
-because the algorithms can be very clearly expressed, and the code is usually
-very concise and simple. This is true because @command{awk} does so much for
you.
-
-It should be noted that these programs are not necessarily intended to
-replace the installed versions on your system.
-Nor may all of these programs be fully compliant with the most recent
-POSIX standard. This is not a problem; their
-purpose is to illustrate @command{awk} language programming for ``real-world''
-tasks.
-
-The programs are presented in alphabetical order.
-
-@menu
-* Cut Program:: The @command{cut} utility.
-* Egrep Program:: The @command{egrep} utility.
-* Id Program:: The @command{id} utility.
-* Split Program:: The @command{split} utility.
-* Tee Program:: The @command{tee} utility.
-* Uniq Program:: The @command{uniq} utility.
-* Wc Program:: The @command{wc} utility.
-@end menu
-
-@node Cut Program
-@subsection Cutting Out Fields and Columns
-
-@cindex @command{cut} utility
-@cindex @command{cut} utility
-@cindex fields @subentry cutting
-@cindex columns @subentry cutting
-The @command{cut} utility selects, or ``cuts,'' characters or fields
-from its standard input and sends them to its standard output.
-Fields are separated by TABs by default,
-but you may supply a command-line option to change the field
-@dfn{delimiter} (i.e., the field-separator character). @command{cut}'s
-definition of fields is less general than @command{awk}'s.
-
-A common use of @command{cut} might be to pull out just the login names of
-logged-on users from the output of @command{who}. For example, the following
-pipeline generates a sorted, unique list of the logged-on users:
-
-@example
-who | cut -c1-8 | sort | uniq
-@end example
-
-The options for @command{cut} are:
-
-@table @code
-@item -c @var{list}
-Use @var{list} as the list of characters to cut out. Items within the list
-may be separated by commas, and ranges of characters can be separated with
-dashes. The list @samp{1-8,15,22-35} specifies characters 1 through
-8, 15, and 22 through 35.
-
-@item -d @var{delim}
-Use @var{delim} as the field-separator character instead of the TAB
-character.
-
-@item -f @var{list}
-Use @var{list} as the list of fields to cut out.
-
-@item -s
-Suppress printing of lines that do not contain the field delimiter.
-@end table
-
-The @command{awk} implementation of @command{cut} uses the @code{getopt()}
library
-function (@pxref{Getopt Function})
-and the @code{join()} library function
-(@pxref{Join Function}).
-
-The current POSIX version of @command{cut} has options to cut fields based on
-both bytes and characters. This version does not attempt to implement those
options,
-as @command{awk} works exclusively in terms of characters.
-
-The program begins with a comment describing the options, the library
-functions needed, and a @code{usage()} function that prints out a usage
-message and exits. @code{usage()} is called if invalid arguments are
-supplied:
-
-@cindex @file{cut.awk} program
-@example
-@c file eg/prog/cut.awk
-# cut.awk --- implement cut in awk
-@c endfile
-@ignore
-@c file eg/prog/cut.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-@c endfile
-@end ignore
-@c file eg/prog/cut.awk
-
-# Options:
-# -c list Cut characters
-# -f list Cut fields
-# -d c Field delimiter character
-#
-# -s Suppress lines without the delimiter
-#
-# Requires getopt() and join() library functions
-
-@group
-function usage()
-@{
- print("usage: cut [-f list] [-d c] [-s] [files...]") > "/dev/stderr"
- print(" cut [-c list] [files...]") > "/dev/stderr"
- exit 1
-@}
-@end group
-@c endfile
-@end example
-
-@cindex @code{BEGIN} pattern @subentry running @command{awk} programs and
-@cindex @code{FS} variable @subentry running @command{awk} programs and
-Next comes a @code{BEGIN} rule that parses the command-line options.
-It sets @code{FS} to a single TAB character, because that is @command{cut}'s
-default field separator. The rule then sets the output field separator to be
the
-same as the input field separator. A loop using @code{getopt()} steps
-through the command-line options. Exactly one of the variables
-@code{by_fields} or @code{by_chars} is set to true, to indicate that
-processing should be done by fields or by characters, respectively.
-When cutting by characters, the output field separator is set to the null
-string:
-
-@example
-@c file eg/prog/cut.awk
-BEGIN @{
- FS = "\t" # default
- OFS = FS
- while ((c = getopt(ARGC, ARGV, "sf:c:d:")) != -1) @{
- if (c == "f") @{
- by_fields = 1
- fieldlist = Optarg
- @} else if (c == "c") @{
- by_chars = 1
- fieldlist = Optarg
- OFS = ""
- @} else if (c == "d") @{
- if (length(Optarg) > 1) @{
- printf("cut: using first character of %s" \
- " for delimiter\n", Optarg) > "/dev/stderr"
- Optarg = substr(Optarg, 1, 1)
- @}
- fs = FS = Optarg
- OFS = FS
- if (FS == " ") # defeat awk semantics
- FS = "[ ]"
- @} else if (c == "s")
- suppress = 1
- else
- usage()
- @}
-
- # Clear out options
- for (i = 1; i < Optind; i++)
- ARGV[i] = ""
-@c endfile
-@end example
-
-@cindex field separator @subentry spaces as
-The code must take
-special care when the field delimiter is a space. Using
-a single space (@code{@w{" "}}) for the value of @code{FS} is
-incorrect---@command{awk} would separate fields with runs of spaces,
-TABs, and/or newlines, and we want them to be separated with individual
-spaces.
-To this end, we save the original space character in the variable
-@code{fs} for later use; after setting @code{FS} to @code{@w{"[ ]"}} we can't
-use it directly to see if the field delimiter character is in the string.
-
-Also remember that after @code{getopt()} is through
-(as described in @ref{Getopt Function}),
-we have to
-clear out all the elements of @code{ARGV} from 1 to @code{Optind},
-so that @command{awk} does not try to process the command-line options
-as @value{FN}s.
-
-After dealing with the command-line options, the program verifies that the
-options make sense. Only one or the other of @option{-c} and @option{-f}
-should be used, and both require a field list. Then the program calls
-either @code{set_fieldlist()} or @code{set_charlist()} to pull apart the
-list of fields or characters:
-
-@example
-@c file eg/prog/cut.awk
- if (by_fields && by_chars)
- usage()
-
- if (by_fields == 0 && by_chars == 0)
- by_fields = 1 # default
-
-@group
- if (fieldlist == "") @{
- print "cut: needs list for -c or -f" > "/dev/stderr"
- exit 1
- @}
-@end group
-
- if (by_fields)
- set_fieldlist()
- else
- set_charlist()
-@}
-@c endfile
-@end example
-
-@code{set_fieldlist()} splits the field list apart at the commas
-into an array. Then, for each element of the array, it looks to
-see if the element is actually a range, and if so, splits it apart.
-The function checks the range
-to make sure that the first number is smaller than the second.
-Each number in the list is added to the @code{flist} array, which
-simply lists the fields that will be printed. Normal field splitting
-is used. The program lets @command{awk} handle the job of doing the
-field splitting:
-
-@example
-@c file eg/prog/cut.awk
-function set_fieldlist( n, m, i, j, k, f, g)
-@{
- n = split(fieldlist, f, ",")
- j = 1 # index in flist
- for (i = 1; i <= n; i++) @{
- if (index(f[i], "-") != 0) @{ # a range
- m = split(f[i], g, "-")
-@group
- if (m != 2 || g[1] >= g[2]) @{
- printf("cut: bad field list: %s\n",
- f[i]) > "/dev/stderr"
- exit 1
- @}
-@end group
- for (k = g[1]; k <= g[2]; k++)
- flist[j++] = k
- @} else
- flist[j++] = f[i]
- @}
- nfields = j - 1
-@}
-@c endfile
-@end example
-
-The @code{set_charlist()} function is more complicated than
-@code{set_fieldlist()}.
-The idea here is to use @command{gawk}'s @code{FIELDWIDTHS} variable
-(@pxref{Constant Size}),
-which describes constant-width input. When using a character list, that is
-exactly what we have.
-
-Setting up @code{FIELDWIDTHS} is more complicated than simply listing the
-fields that need to be printed. We have to keep track of the fields to
-print and also the intervening characters that have to be skipped.
-For example, suppose you wanted characters 1 through 8, 15, and
-22 through 35. You would use @samp{-c 1-8,15,22-35}. The necessary value
-for @code{FIELDWIDTHS} is @code{@w{"8 6 1 6 14"}}. This yields five
-fields, and the fields to print
-are @code{$1}, @code{$3}, and @code{$5}.
-The intermediate fields are @dfn{filler},
-which is stuff in between the desired data.
-@code{flist} lists the fields to print, and @code{t} tracks the
-complete field list, including filler fields:
-
-@example
-@c file eg/prog/cut.awk
-function set_charlist( field, i, j, f, g, n, m, t,
- filler, last, len)
-@{
- field = 1 # count total fields
- n = split(fieldlist, f, ",")
- j = 1 # index in flist
- for (i = 1; i <= n; i++) @{
- if (index(f[i], "-") != 0) @{ # range
- m = split(f[i], g, "-")
- if (m != 2 || g[1] >= g[2]) @{
- printf("cut: bad character list: %s\n",
- f[i]) > "/dev/stderr"
- exit 1
- @}
- len = g[2] - g[1] + 1
- if (g[1] > 1) # compute length of filler
- filler = g[1] - last - 1
- else
- filler = 0
-@group
- if (filler)
- t[field++] = filler
-@end group
- t[field++] = len # length of field
- last = g[2]
- flist[j++] = field - 1
- @} else @{
- if (f[i] > 1)
- filler = f[i] - last - 1
- else
- filler = 0
- if (filler)
- t[field++] = filler
- t[field++] = 1
- last = f[i]
- flist[j++] = field - 1
- @}
- @}
- FIELDWIDTHS = join(t, 1, field - 1)
- nfields = j - 1
-@}
-@c endfile
-@end example
-
-Next is the rule that processes the data. If the @option{-s} option
-is given, then @code{suppress} is true. The first @code{if} statement
-makes sure that the input record does have the field separator. If
-@command{cut} is processing fields, @code{suppress} is true, and the field
-separator character is not in the record, then the record is skipped.
-
-If the record is valid, then @command{gawk} has split the data
-into fields, either using the character in @code{FS} or using fixed-length
-fields and @code{FIELDWIDTHS}. The loop goes through the list of fields
-that should be printed. The corresponding field is printed if it contains
data.
-If the next field also has data, then the separator character is
-written out between the fields:
-
-@example
-@c file eg/prog/cut.awk
-@{
- if (by_fields && suppress && index($0, fs) == 0)
- next
-
- for (i = 1; i <= nfields; i++) @{
- if ($flist[i] != "") @{
- printf "%s", $flist[i]
- if (i < nfields && $flist[i+1] != "")
- printf "%s", OFS
- @}
- @}
- print ""
-@}
-@c endfile
-@end example
-
-This version of @command{cut} relies on @command{gawk}'s @code{FIELDWIDTHS}
-variable to do the character-based cutting. It is possible in
-other @command{awk} implementations to use @code{substr()}
-(@pxref{String Functions}), but
-it is also extremely painful.
-The @code{FIELDWIDTHS} variable supplies an elegant solution to the problem
-of picking the input line apart by characters.
-
-
-@node Egrep Program
-@subsection Searching for Regular Expressions in Files
-
-@cindex regular expressions @subentry searching for
-@cindex searching @subentry files for regular expressions
-@cindex files @subentry searching for regular expressions
-@cindex @command{egrep} utility
-The @command{grep} family of programs searches files for patterns.
-These programs have an unusual history.
-Initially there was @command{grep} (Global Regular Expression Print),
-which used what are now called Basic Regular Expressions (BREs).
-Later there was @command{egrep} (Extended @command{grep}) which used
-what are now called Extended Regular Expressions (EREs). (These are almost
-identical to those available in @command{awk}; @pxref{Regexp}).
-There was also @command{fgrep} (Fast @command{grep}), which searched
-for matches of one more fixed strings.
-
-POSIX chose to combine these three programs into one, simply named
-@command{grep}. On a POSIX system, @command{grep}'s default behavior
-is to search using BREs. You use @command{-E} to specify the use
-of EREs, and @option{-F} to specify searching for fixed strings.
-
-In practice, systems continue to come with separate @command{egrep}
-and @command{fgrep} utilities, for backwards compatibility. This
-@value{SECTION} provides an @command{awk} implementation of @command{egrep},
-which supports all of the POSIX-mandated options.
-You invoke it as follows:
-
-@display
-@command{egrep} [@var{options}] @code{'@var{pattern}'} @var{files} @dots{}
-@end display
-
-The @var{pattern} is a regular expression. In typical usage, the regular
-expression is quoted to prevent the shell from expanding any of the
-special characters as @value{FN} wildcards. Normally, @command{egrep}
-prints the lines that matched. If multiple @value{FN}s are provided on
-the command line, each output line is preceded by the name of the file
-and a colon.
-
-The options to @command{egrep} are as follows:
-
-@table @code
-@item -c
-Print a count of the lines that matched the pattern, instead of the
-lines themselves.
-
-@item -e @var{pattern}
-Use @var{pattern} as the regexp to match. The purpose of the @option{-e}
-option is to allow patterns that start with a @samp{-}.
-
-@item -i
-Ignore case distinctions in both the pattern and the input data.
-
-@item -l
-Only print (list) the names of the files that matched, not the lines that
matched.
-
-@item -q
-Be quiet. No output is produced and the exit value indicates whether
-the pattern was matched.
-
-@item -s
-Be silent. Do not print error messages for files that could
-not be opened.
-
-@item -v
-Invert the sense of the test. @command{egrep} prints the lines that do
-@emph{not} match the pattern and exits successfully if the pattern is not
-matched.
-
-@item -x
-Match the entire input line in order to consider the match as having
-succeeded.
-@end table
-
-This version uses the @code{getopt()} library function
-(@pxref{Getopt Function}) and @command{gawk}'s
-@code{BEGINFILE} and @code{ENDFILE} special patterns
-(@pxref{BEGINFILE/ENDFILE}).
-
-The program begins with descriptive comments and then a @code{BEGIN} rule
-that processes the command-line arguments with @code{getopt()}. The
@option{-i}
-(ignore case) option is particularly easy with @command{gawk}; we just use the
-@code{IGNORECASE} predefined variable
-(@pxref{Built-in Variables}):
-
-@cindex @file{egrep.awk} program
-@example
-@c file eg/prog/egrep.awk
-# egrep.awk --- simulate egrep in awk
-#
-@c endfile
-@ignore
-@c file eg/prog/egrep.awk
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised September 2020
-
-@c endfile
-@end ignore
-@c file eg/prog/egrep.awk
-# Options:
-# -c count of lines
-# -e argument is pattern
-# -i ignore case
-# -l print filenames only
-# -n add line number to output
-# -q quiet - use exit value
-# -s silent - don't print errors
-# -v invert test, success if no match
-# -x the entire line must match
-#
-# Requires getopt library function
-# Uses IGNORECASE, BEGINFILE and ENDFILE
-# Invoke using gawk -f egrep.awk -- options ...
-
-BEGIN @{
- while ((c = getopt(ARGC, ARGV, "ce:ilnqsvx")) != -1) @{
- if (c == "c")
- count_only++
- else if (c == "e")
- pattern = Optarg
- else if (c == "i")
- IGNORECASE = 1
- else if (c == "l")
- filenames_only++
- else if (c == "n")
- line_numbers++
- else if (c == "q")
- no_print++
- else if (c == "s")
- no_errors++
- else if (c == "v")
- invert++
- else if (c == "x")
- full_line++
- else
- usage()
- @}
-@c endfile
-@end example
-
-@noindent
-Note the comment about invocation: Because several of the options overlap
-with @command{gawk}'s, a @option{--} is needed to tell @command{gawk}
-to stop looking for options.
-
-Next comes the code that handles the @command{egrep}-specific behavior.
-@command{egrep} uses the first nonoption on the command line
-if no pattern is supplied with @option{-e}.
-If the pattern is empty, that means no pattern was supplied, so it's
-necessary to print an error message and exit.
-The @command{awk} command-line arguments up to @code{ARGV[Optind]}
-are cleared, so that @command{awk} won't try to process them as files. If no
-files are specified, the standard input is used, and if multiple files are
-specified, we make sure to note this so that the @value{FN}s can precede the
-matched lines in the output:
-
-@example
-@c file eg/prog/egrep.awk
- if (pattern == "")
- pattern = ARGV[Optind++]
-
- if (pattern == "")
- usage()
-
- for (i = 1; i < Optind; i++)
- ARGV[i] = ""
-
- if (Optind >= ARGC) @{
- ARGV[1] = "-"
- ARGC = 2
- @} else if (ARGC - Optind > 1)
- do_filenames++
-@}
-@c endfile
-@end example
-
-The @code{BEGINFILE} rule executes
-when each new file is processed. In this case, it is fairly simple; it
-initializes a variable @code{fcount} to zero. @code{fcount} tracks
-how many lines in the current file matched the pattern.
-
-Here also is where we implement the @option{-s} option. We check
-if @code{ERRNO} has been set, and if @option{-s} was supplied.
-In that case, it's necessary to move on to the next file. Otherwise
-@command{gawk} would exit with an error:
-
-@example
-@c file eg/prog/egrep.awk
-BEGINFILE @{
- fcount = 0
- if (ERRNO && no_errors)
- nextfile
-@}
-@c endfile
-@end example
-
-The @code{ENDFILE} rule executes after each file has been processed.
-It affects the output only when the user wants a count of the number of lines
that
-matched. @code{no_print} is true only if the exit status is desired.
-@code{count_only} is true if line counts are desired. @command{egrep}
-therefore only prints line counts if printing and counting are enabled.
-The output format must be adjusted depending upon the number of files to
-process. Finally, @code{fcount} is added to @code{total}, so that we
-know the total number of lines that matched the pattern:
-
-@example
-@c file eg/prog/egrep.awk
-ENDFILE @{
- if (! no_print && count_only) @{
- if (do_filenames)
- print file ":" fcount
- else
- print fcount
- @}
-
-@group
- total += fcount
-@}
-@end group
-@c endfile
-@end example
-
-The following rule does most of the work of matching lines. The variable
-@code{matches} is true (non-zero) if the line matched the pattern.
-If the user specified that the entire line must match (with @option{-x}),
-the code checks this condition by looking at the values of
-@code{RSTART} and @code{RLENGTH}. If those indicate that the match
-is not over the full line, @code{matches} is set to zero (false).
-
-If the user
-wants lines that did not match, we invert the sense of @code{matches}
-using the @samp{!} operator. We then increment @code{fcount} with the value of
-@code{matches}, which is either one or zero, depending upon a
-successful or unsuccessful match. If the line does not match, the
-@code{next} statement just moves on to the next input line.
-
-We make a number of additional tests, but only if we
-are not counting lines. First, if the user only wants the exit status
-(@code{no_print} is true), then it is enough to know that @emph{one}
-line in this file matched, and we can skip on to the next file with
-@code{nextfile}. Similarly, if we are only printing @value{FN}s, we can
-print the @value{FN}, and then skip to the next file with @code{nextfile}.
-Finally, each line is printed, with a leading @value{FN},
-optional colon and line number, and the final colon
-if necessary:
-
-@cindex @code{!} (exclamation point) @subentry @code{!} operator
-@cindex exclamation point (@code{!}) @subentry @code{!} operator
-@example
-@c file eg/prog/egrep.awk
-@{
- matches = match($0, pattern)
- if (matches && full_line && (RSTART != 1 || RLENGTH != length()))
- matches = 0
-
- if (invert)
- matches = ! matches
-
- fcount += matches # 1 or 0
-
- if (! matches)
- next
-
- if (! count_only) @{
- if (no_print)
- nextfile
-
- if (filenames_only) @{
- print FILENAME
- nextfile
- @}
-
- if (do_filenames)
- if (line_numbers)
- print FILENAME ":" FNR ":" $0
- else
- print FILENAME ":" $0
- else
- print
- @}
-@}
-@c endfile
-@end example
-
-The @code{END} rule takes care of producing the correct exit status. If
-there are no matches, the exit status is one; otherwise, it is zero:
-
-@example
-@c file eg/prog/egrep.awk
-END @{
- exit (total == 0)
-@}
-@c endfile
-@end example
-
-The @code{usage()} function prints a usage message in case of invalid options,
-and then exits:
-
-@example
-@c file eg/prog/egrep.awk
-function usage()
-@{
- print("Usage:\tegrep [-cilnqsvx] [-e pat] [files ...]") > "/dev/stderr"
- print("\tegrep [-cilnqsvx] pat [files ...]") > "/dev/stderr"
- exit 1
-@}
-@c endfile
-@end example
-
-@node Id Program
-@subsection Printing Out User Information
-
-@cindex printing @subentry user information
-@cindex users, information about @subentry printing
-@cindex @command{id} utility
-The @command{id} utility lists a user's real and effective user ID numbers,
-real and effective group ID numbers, and the user's group set, if any.
-@command{id} only prints the effective user ID and group ID if they are
-different from the real ones. If possible, @command{id} also supplies the
-corresponding user and group names. The output might look like this:
-
-@example
-$ @kbd{id}
-@print{} uid=1000(arnold) gid=1000(arnold)
groups=1000(arnold),4(adm),7(lp),27(sudo)
-@end example
-
-@cindex @code{PROCINFO} array @subentry user and group ID numbers and
-This information is part of what is provided by @command{gawk}'s
-@code{PROCINFO} array (@pxref{Built-in Variables}).
-However, the @command{id} utility provides a more palatable output than just
-individual numbers.
-
-The POSIX version of @command{id} takes several options that give you
-control over the output's format, such as printing only real ids, or printing
-only numbers or only names. Additionally, you can print the information
-for a specific user, instead of that of the current user.
-
-Here is a version of POSIX @command{id} written in @command{awk}.
-It uses the @code{getopt()} library function
-(@pxref{Getopt Function}),
-the user database library functions
-(@pxref{Passwd Functions}),
-and the group database library functions
-(@pxref{Group Functions})
-from @ref{Library Functions}.
-
-The program is moderately straightforward. All the work is done in the
-@code{BEGIN} rule.
-It starts with explanatory comments, a list of options,
-and then a @code{usage()} function:
-
-@cindex @file{id.awk} program
-@example
-@c file eg/prog/id.awk
-# id.awk --- implement id in awk
-#
-# Requires user and group library functions and getopt
-@c endfile
-@ignore
-@c file eg/prog/id.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised February 1996
-# Revised May 2014
-# Revised September 2014
-# Revised September 2020
-
-@c endfile
-@end ignore
-@c file eg/prog/id.awk
-# output is:
-# uid=12(foo) euid=34(bar) gid=3(baz) \
-# egid=5(blat) groups=9(nine),2(two),1(one)
-
-# Options:
-# -G Output all group ids as space separated numbers (ruid, euid, groups)
-# -g Output only the euid as a number
-# -n Output name instead of the numeric value (with -g/-G/-u)
-# -r Output ruid/rguid instead of effective id
-# -u Output only effective user id, as a number
-
-@group
-function usage()
-@{
- printf("Usage:\n" \
- "\tid [user]\n" \
- "\tid -G [-n] [user]\n" \
- "\tid -g [-nr] [user]\n" \
- "\tid -u [-nr] [user]\n") > "/dev/stderr"
-
- exit 1
-@}
-@end group
-@c endfile
-@end example
-
-The first step is to parse the options using @code{getopt()},
-and to set various flag variables according to the options given:
-
-@example
-@c file eg/prog/id.awk
-BEGIN @{
- # parse args
- while ((c = getopt(ARGC, ARGV, "Ggnru")) != -1) @{
- if (c == "G")
- groupset_only++
- else if (c == "g")
- egid_only++
- else if (c == "n")
- names_not_groups++
- else if (c == "r")
- real_ids_only++
- else if (c == "u")
- euid_only++
- else
- usage()
- @}
-@c endfile
-@end example
-
-The next step is to check that no conflicting options were
-provided. @option{-G} and @option{-r} are mutually exclusive.
-It is also not allowed to provide more than one user name
-on the command line:
-
-@example
-@c file eg/prog/id.awk
- if (groupset_only && real_ids_only)
- usage()
- else if (ARGC - Optind > 1)
- usage()
-@c endfile
-@end example
-
-The user and group ID numbers are obtained from
-@code{PROCINFO} for the current user, or from the
-user and password databases for a user supplied on
-the command line. In the latter case, @code{real_ids_only}
-is set, since it's not possible to print information about
-the effective user and group IDs:
-
-@example
-@c file eg/prog/id.awk
- if (ARGC - Optind == 0) @{
- # gather info for current user
- uid = PROCINFO["uid"]
- euid = PROCINFO["euid"]
- gid = PROCINFO["gid"]
- egid = PROCINFO["egid"]
- for (i = 1; ("group" i) in PROCINFO; i++)
- groupset[i] = PROCINFO["group" i]
- @} else @{
- fill_info_for_user(ARGV[ARGC-1])
- real_ids_only++
- @}
-@c endfile
-@end example
-
-The test in the @code{for} loop is worth noting.
-Any supplementary groups in the @code{PROCINFO} array have the
-indices @code{"group1"} through @code{"group@var{N}"} for some
-@var{N} (i.e., the total number of supplementary groups).
-However, we don't know in advance how many of these groups
-there are.
-
-This loop works by starting at one, concatenating the value with
-@code{"group"}, and then using @code{in} to see if that value is
-in the array (@pxref{Reference to Elements}). Eventually, @code{i} increments
past
-the last group in the array and the loop exits.
-
-The loop is also correct if there are @emph{no} supplementary
-groups; then the condition is false the first time it's
-tested, and the loop body never executes.
-
-
-Now, based on the options, we decide what information to print.
-For @option{-G} (print just the group set), we then select
-whether to print names or numbers. In either case, when done
-we exit:
-
-@example
-@c file eg/prog/id.awk
- if (groupset_only) @{
- if (names_not_groups) @{
- for (i = 1; i in groupset; i++) @{
- entry = getgrgid(groupset[i])
- name = get_first_field(entry)
- printf("%s", name)
- if ((i + 1) in groupset)
- printf(" ")
- @}
- @} else @{
- for (i = 1; i in groupset; i++) @{
- printf("%u", groupset[i])
- if ((i + 1) in groupset)
- printf(" ")
- @}
- @}
-
- print "" # final newline
- exit 0
- @}
-@c endfile
-@end example
-
-Otherwise, for @option{-g} (effective group ID only), we
-check if @option{-r} was also provided, in which case we
-use the real group ID. Then based on @option{-n}, we decide
-whether to print names or numbers. Here too, when done,
-we exit:
-
-@example
-@c file eg/prog/id.awk
- else if (egid_only) @{
- id = real_ids_only ? gid : egid
- if (names_not_groups) @{
- entry = getgrgid(id)
- name = get_first_field(entry)
- printf("%s\n", name)
- @} else @{
- printf("%u\n", id)
- @}
-
- exit 0
- @}
-@c endfile
-@end example
-
-The @code{get_first_field()} function extracts the group name from
-the group database entry for the given group ID.
-
-Similar processing logic applies to @option{-u} (effective user ID only),
-combined with @option{-r} and @option{-n}:
-
-@example
-@c file eg/prog/id.awk
- else if (euid_only) @{
- id = real_ids_only ? uid : euid
- if (names_not_groups) @{
- entry = getpwuid(id)
- name = get_first_field(entry)
- printf("%s\n", name)
- @} else @{
- printf("%u\n", id)
- @}
-
- exit 0
- @}
-@c endfile
-@end example
-
-At this point, we haven't exited yet, so we print
-the regular, default output, based either on the current
-user's information, or that of the user whose name was
-provided on the command line. We start with the real user ID:
-
-@example
-@c file eg/prog/id.awk
- printf("uid=%d", uid)
- pw = getpwuid(uid)
- print_first_field(pw)
-@c endfile
-@end example
-
-The @code{print_first_field()} function prints the user's
-login name from the password file entry, surrounded by
-parentheses. It is shown soon.
-Printing the effective user ID is next:
-
-@example
-@c file eg/prog/id.awk
- if (euid != uid && ! real_ids_only) @{
- printf(" euid=%d", euid)
- pw = getpwuid(euid)
- print_first_field(pw)
- @}
-@c endfile
-@end example
-
-Similar logic applies to the real and effective group IDs:
-
-@example
-@c file eg/prog/id.awk
- printf(" gid=%d", gid)
- pw = getgrgid(gid)
- print_first_field(pw)
-
- if (egid != gid && ! real_ids_only) @{
- printf(" egid=%d", egid)
- pw = getgrgid(egid)
- print_first_field(pw)
- @}
-@c endfile
-@end example
-
-Finally, we print the group set and the terminating newline:
-
-@example
-@c file eg/prog/id.awk
- for (i = 1; i in groupset; i++) @{
- if (i == 1)
- printf(" groups=")
- group = groupset[i]
- printf("%d", group)
- pw = getgrgid(group)
- print_first_field(pw)
- if ((i + 1) in groupset)
- printf(",")
- @}
-
- print ""
-@}
-@c endfile
-@end example
-
-The @code{get_first_field()} function extracts the first field
-from a password or group file entry for use as a user or group
-name. Fields are separated by @samp{:} characters:
-
-@example
-@c file eg/prog/id.awk
-function get_first_field(str, a)
-@{
- if (str != "") @{
- split(str, a, ":")
- return a[1]
- @}
-@}
-@c endfile
-@end example
-
-This function is then used by @code{print_first_field()} to
-output the given name surrounded by parentheses:
-
-@example
-@c file eg/prog/id.awk
-function print_first_field(str)
-@{
- first = get_first_field(str)
- printf("(%s)", first)
-@}
-@c endfile
-@end example
-
-These two functions simply isolate out some code that is used repeatedly,
-making the whole program shorter and cleaner. In particular, moving the
-check for the empty string into @code{get_first_field()} saves several
-lines of code.
-
-Finally, @code{fill_info_for_user()} fetches user, group, and group
-set information for the user named on the command. The code is fairly
-straightforward, merely requiring that we exit if the given user doesn't
-exist:
-
-@example
-@c file eg/prog/id.awk
-function fill_info_for_user(user,
- pwent, fields, groupnames, grent, groups, i)
-@{
- pwent = getpwnam(user)
- if (pwent == "") @{
- printf("id: '%s': no such user\n", user) > "/dev/stderr"
- exit 1
- @}
-
- split(pwent, fields, ":")
- uid = fields[3] + 0
- gid = fields[4] + 0
-@c endfile
-@end example
-
-Getting the group set is a little awkward. The library routine
-@code{getgruser()} returns a list of group @emph{names}. These
-have to be gone through and turned back into group numbers,
-so that the rest of the code will work as expected:
-
-@example
-@ignore
-@c file eg/prog/id.awk
-
-@c endfile
-@end ignore
-@c file eg/prog/id.awk
- groupnames = getgruser(user)
- split(groupnames, groups, " ")
- for (i = 1; i in groups; i++) @{
- grent = getgrnam(groups[i])
- split(grent, fields, ":")
- groupset[i] = fields[3] + 0
- @}
-@}
-@c endfile
-@end example
-
-@node Split Program
-@subsection Splitting a Large File into Pieces
-
-@cindex files @subentry splitting
-@cindex @code{split} utility
-The @command{split} utility splits large text files into smaller pieces.
-The usage follows the POSIX standard for @command{split} and is as follows:
-
-@display
-@command{split} [@option{-l} @var{count}] [@option{-a} @var{suffix-len}]
[@var{file} [@var{outname}]]
-@command{split} @option{-b} @var{N}[@code{k}|@code{m}]] [@option{-a}
@var{suffix-len}] [@var{file} [@var{outname}]]
-@end display
-
-By default, the output files are named @file{xaa}, @file{xab}, and so
-on. Each file has 1,000 lines in it, with the likely exception of the
-last file.
-
-The @command{split} program has evolved over time, and the current POSIX
-version is more complicated than the original Unix version. The options
-and what they do are as follows:
-
-@table @asis
-@item @option{-a} @var{suffix-len}
-Use @var{suffix-len} characters for the suffix. For example, if
@var{suffix-len}
-is four, the output files would range from @file{xaaaa} to @file{xzzzz}.
-
-@item @option{-b} @var{N}[@code{k}|@code{m}]]
-Instead of each file containing a specified number of lines, each file
-should have (at most) @var{N} bytes. Supplying a trailing @samp{k}
-multiplies @var{N} by 1,024, yielding kilobytes. Supplying a trailing
-@samp{m} multiplies @var{N} by 1,048,576 (@math{1,024 @value{TIMES} 1,024})
-yielding megabytes. (This option is mutually exclusive with @option{-l}).
-
-@item @option{-l} @var{count}
-Each file should have at most @var{count} lines, instead of the default
-1,000. (This option is mutually exclusive with @option{-b}).
-@end table
-
-If supplied, @var{file} is the input file to read. Otherwise standard
-input is processed. If supplied, @var{outname} is the leading prefix
-to use for @value{FN}s, instead of @samp{x}.
-
-@cindex @env{LC_ALL} environment variable
-@cindex environment variables @subentry @env{LC_ALL}
-In order to use the @option{-b} option, @command{gawk} should be invoked
-with its @option{-b} option (@pxref{Options}), or with the environment
-variable @env{LC_ALL} set to @samp{C}, so that each input byte is treated
-as a separate character.@footnote{Using @option{-b} twice requires
-separating @command{gawk}'s options from those of the program. For example:
-@samp{gawk -f getopt.awk -f split.awk -b -- -b 42m large-file.txt split-}.}
-
-Here is an implementation of @command{split} in @command{awk}. It uses the
-@code{getopt()} function presented in @ref{Getopt Function}.
-
-The program begins with a standard descriptive comment and then
-a @code{usage()} function describing the options. The variable
-@code{common} keeps the function's lines short so that they
-look nice on the page:
-
-@cindex @file{split.awk} program
-@example
-@c file eg/prog/split.awk
-# split.awk --- do split in awk
-#
-# Requires getopt() library function.
-@c endfile
-@ignore
-@c file eg/prog/split.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised slightly, May 2014
-# Rewritten September 2020
-
-@c endfile
-@end ignore
-@c file eg/prog/split.awk
-
-function usage( common)
-@{
- common = "[-a suffix-len] [file [outname]]"
- printf("usage: split [-l count] %s\n", common) > "/dev/stderr"
- printf(" split [-b N[k|m]] %s\n", common) > "/dev/stderr"
- exit 1
-@}
-@c endfile
-@end example
-
-Next, in a @code{BEGIN} rule we set the default values and parse the arguments.
-After that we initialize the data structures used to cycle the suffix
-from @samp{aa@dots{}} to @samp{zz@dots{}}. Finally we set the name of
-the first output file:
-
-@example
-@c file eg/prog/split.awk
-BEGIN @{
- # Set defaults:
- Suffix_length = 2
- Line_count = 1000
- Byte_count = 0
- Outfile = "x"
-
- parse_arguments()
-
- init_suffix_data()
-
- Output = (Outfile compute_suffix())
-@}
-@c endfile
-@end example
-
-Parsing the arguments is straightforward. The program follows our
-convention (@pxref{Library Names}) of having important global variables
-start with an uppercase letter:
-
-@example
-@c file eg/prog/split.awk
-function parse_arguments( i, c, l, modifier)
-@{
- while ((c = getopt(ARGC, ARGV, "a:b:l:")) != -1) @{
- if (c == "a")
- Suffix_length = Optarg + 0
- else if (c == "b") @{
- Byte_count = Optarg + 0
- Line_count = 0
-
- l = length(Optarg)
- modifier = substr(Optarg, l, 1)
- if (modifier == "k")
- Byte_count *= 1024
- else if (modifier == "m")
- Byte_count *= 1024 * 1024
- @} else if (c == "l") @{
- Line_count = Optarg + 0
- Byte_count = 0
- @} else
- usage()
- @}
-
- # Clear out options
- for (i = 1; i < Optind; i++)
- ARGV[i] = ""
-
- # Check for filename
- if (ARGV[Optind]) @{
- Optind++
-
- # Check for different prefix
- if (ARGV[Optind]) @{
- Outfile = ARGV[Optind]
- ARGV[Optind] = ""
-
- if (++Optind < ARGC)
- usage()
- @}
- @}
-@}
-@c endfile
-@end example
-
-Managing the @value{FN} suffix is interesting.
-Given a suffix of length three, say, the values go from
-@samp{aaa}, @samp{aab}, @samp{aac} and so on, all the way to
-@samp{zzx}, @samp{zzy}, and finally @samp{zzz}.
-There are two important aspects to this:
-
-@itemize @bullet
-@item
-We have to be
-able to easily generate these suffixes, and in particular
-easily handle ``rolling over''; for example, going from
-@samp{abz} to @samp{aca}.
-
-@item
-We have to tell when we've finished with the last file,
-so that if we still have more input data we can print an
-error message and exit. The trick is to handle this @emph{after}
-using the last suffix, and not when the final suffix is created.
-@end itemize
-
-The computation is handled by @code{compute_suffix()}.
-This function is called every time a new file is opened.
-
-The flow here is messy, because we want to generate @samp{zzzz} (say),
-and use it, and only produce an error after all the @value{FN}
-suffixes have been used up. The logical steps are as follows:
-
-@enumerate 1
-@item
-Generate the suffix, saving the value in @code{result} to return.
-To do this, the supplementary array @code{Suffix_ind} contains one
-element for each letter in the suffix. Each element ranges from 1 to
-26, acting as the index into a string containing all the lowercase
-letters of the English alphabet.
-It is initialized by @code{init_suffix_data()}.
-@code{result} is built up one letter at a time, using each @code{substr()}.
-
-@item
-Prepare the data structures for the next time @code{compute_suffix()}
-is called. To do this, we loop over @code{Suffix_ind}, @emph{backwards}.
-If the current element is less than 26, it's incremented and the loop
-breaks (@samp{abq} goes to @samp{abr}). Otherwise, the element is
-reset to one and we move down the list (@samp{abz} to @samp{aca}).
-Thus, the @code{Suffix_ind} array is always ``one step ahead'' of the actual
-@value{FN} suffix to be returned.
-
-@item
-Check if we've gone past the limit of possible @value{FN}s.
-If @code{Reached_last} is true, print a message and exit. Otherwise,
-check if @code{Suffix_ind} describes a suffix where all the letters are
-@samp{z}. If that's the case we're about to return the final suffix. If
-so, we set @code{Reached_last} to true so that the @emph{next} call to
-@code{compute_suffix()} will cause a failure.
-@end enumerate
-
-Physically, the steps in the function occur in the order 3, 1, 2:
-
-@example
-@c file eg/prog/split.awk
-function compute_suffix( i, result, letters)
-@{
- # Logical step 3
- if (Reached_last) @{
- printf("split: too many files!\n") > "/dev/stderr"
- exit 1
- @} else if (on_last_file())
- Reached_last = 1 # fail when wrapping after 'zzz'
-
- # Logical step 1
- result = ""
- letters = "abcdefghijklmnopqrstuvwxyz"
- for (i = 1; i <= Suffix_length; i++)
- result = result substr(letters, Suffix_ind[i], 1)
-
- # Logical step 2
- for (i = Suffix_length; i >= 1; i--) @{
- if (++Suffix_ind[i] > 26) @{
- Suffix_ind[i] = 1
- @} else
- break
- @}
-
- return result
-@}
-@c endfile
-@end example
-
-The @code{Suffix_ind} array and @code{Reached_last} are initialized
-by @code{init_suffix_data()}:
-
-@example
-@c file eg/prog/split.awk
-function init_suffix_data( i)
-@{
- for (i = 1; i <= Suffix_length; i++)
- Suffix_ind[i] = 1
-
- Reached_last = 0
-@}
-@c endfile
-@end example
-
-The function @code{on_last_file()} returns true if @code{Suffix_ind} describes
-a suffix where all the letters are @samp{z} by checking that all the elements
-in the array are equal to 26:
-
-@example
-@c file eg/prog/split.awk
-function on_last_file( i, on_last)
-@{
- on_last = 1
- for (i = 1; i <= Suffix_length; i++) @{
- on_last = on_last && (Suffix_ind[i] == 26)
- @}
-
- return on_last
-@}
-@c endfile
-@end example
-
-The actual work of splitting the input file is done by the next two rules.
-Since splitting by line count and splitting by byte count are mutually
-exclusive, we simply use two separate rules, one for when @code{Line_count}
-is greater than zero, and another for when @code{Byte_count} is greater than
zero.
-
-The variable @code{tcount} counts how many lines have been processed so far.
-When it exceeds @code{Line_count}, it's time to close the previous file and
-switch to a new one:
-
-@example
-@c file eg/prog/split.awk
-Line_count > 0 @{
- if (++tcount > Line_count) @{
- close(Output)
- Output = (Outfile compute_suffix())
- tcount = 1
- @}
- print > Output
-@}
-@c endfile
-@end example
-
-The rule for handling bytes is more complicated. Since lines most likely
-vary in length, the @code{Byte_count} boundary may be hit in the middle of
-an input record. In that case, @command{split} has to write enough of the
-first bytes of the input record to finish up @code{Byte_count} bytes, close
-the file, open a new file, and write the rest of the record to the new file.
-The logic here does all that:
-
-@example
-@c file eg/prog/split.awk
-Byte_count > 0 @{
- # `+ 1' is for the final newline
- if (tcount + length($0) + 1 > Byte_count) @{ # would overflow
- # compute leading bytes
- leading_bytes = Byte_count - tcount
-
- # write leading bytes
- printf("%s", substr($0, 1, leading_bytes)) > Output
-
- # close old file, open new file
- close(Output)
- Output = (Outfile compute_suffix())
-
- # set up first bytes for new file
- $0 = substr($0, leading_bytes + 1) # trailing bytes
- tcount = 0
- @}
-
- # write full record or trailing bytes
- tcount += length($0) + 1
- print > Output
-@}
-@c endfile
-@end example
-
-Finally, the @code{END} rule cleans up by closing the last output file:
-
-@example
-@c file eg/prog/split.awk
-END @{
- close(Output)
-@}
-@c endfile
-@end example
-
-@node Tee Program
-@subsection Duplicating Output into Multiple Files
-
-@cindex files @subentry multiple, duplicating output into
-@cindex output @subentry duplicating into files
-@cindex @code{tee} utility
-The @code{tee} program is known as a ``pipe fitting.'' @code{tee} copies
-its standard input to its standard output and also duplicates it to the
-files named on the command line. Its usage is as follows:
-
-@display
-@command{tee} [@option{-a}] @var{file} @dots{}
-@end display
-
-The @option{-a} option tells @code{tee} to append to the named files, instead
of
-truncating them and starting over.
-
-The @code{BEGIN} rule first makes a copy of all the command-line arguments
-into an array named @code{copy}.
-@code{ARGV[0]} is not needed, so it is not copied.
-@code{tee} cannot use @code{ARGV} directly, because @command{awk} attempts to
-process each @value{FN} in @code{ARGV} as input data.
-
-@cindex flag variables
-If the first argument is @option{-a}, then the flag variable
-@code{append} is set to true, and both @code{ARGV[1]} and
-@code{copy[1]} are deleted. If @code{ARGC} is less than two, then no
-@value{FN}s were supplied and @code{tee} prints a usage message and exits.
-Finally, @command{awk} is forced to read the standard input by setting
-@code{ARGV[1]} to @code{"-"} and @code{ARGC} to two:
-
-@cindex @file{tee.awk} program
-@example
-@c file eg/prog/tee.awk
-# tee.awk --- tee in awk
-#
-# Copy standard input to all named output files.
-# Append content if -a option is supplied.
-#
-@c endfile
-@ignore
-@c file eg/prog/tee.awk
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised December 1995
-
-@c endfile
-@end ignore
-@c file eg/prog/tee.awk
-BEGIN @{
- for (i = 1; i < ARGC; i++)
- copy[i] = ARGV[i]
-
- if (ARGV[1] == "-a") @{
- append = 1
- delete ARGV[1]
- delete copy[1]
- ARGC--
- @}
- if (ARGC < 2) @{
- print "usage: tee [-a] file ..." > "/dev/stderr"
- exit 1
- @}
- ARGV[1] = "-"
- ARGC = 2
-@}
-@c endfile
-@end example
-
-The following single rule does all the work. Because there is no pattern, it
is
-executed for each line of input. The body of the rule simply prints the
-line into each file on the command line, and then to the standard output:
-
-@example
-@c file eg/prog/tee.awk
-@{
- # moving the if outside the loop makes it run faster
- if (append)
- for (i in copy)
- print >> copy[i]
- else
- for (i in copy)
- print > copy[i]
- print
-@}
-@c endfile
-@end example
-
-@noindent
-It is also possible to write the loop this way:
-
-@example
-@group
-for (i in copy)
- if (append)
- print >> copy[i]
-@end group
-@group
- else
- print > copy[i]
-@end group
-@end example
-
-@noindent
-This is more concise, but it is also less efficient. The @samp{if} is
-tested for each record and for each output file. By duplicating the loop
-body, the @samp{if} is only tested once for each input record. If there are
-@var{N} input records and @var{M} output files, the first method only
-executes @var{N} @samp{if} statements, while the second executes
-@var{N}@code{*}@var{M} @samp{if} statements.
-
-Finally, the @code{END} rule cleans up by closing all the output files:
-
-@example
-@c file eg/prog/tee.awk
-END @{
- for (i in copy)
- close(copy[i])
-@}
-@c endfile
-@end example
-
-@node Uniq Program
-@subsection Printing Nonduplicated Lines of Text
-
-@cindex printing @subentry unduplicated lines of text
-@cindex text, printing @subentry unduplicated lines of
-@cindex @command{uniq} utility
-The @command{uniq} utility reads sorted lines of data on its standard
-input, and by default removes duplicate lines. In other words, it only
-prints unique lines---hence the name. @command{uniq} has a number of
-options. The usage is as follows:
-
-@display
-@command{uniq} [@option{-udc} [@code{-f @var{n}}] [@code{-s @var{n}}]]
[@var{inputfile} [@var{outputfile}]]
-@end display
-
-The options for @command{uniq} are:
-
-@table @code
-@item -d
-Print only repeated (duplicated) lines.
-
-@item -u
-Print only nonrepeated (unique) lines.
-
-@item -c
-Count lines. This option overrides @option{-d} and @option{-u}. Both repeated
-and nonrepeated lines are counted.
-
-@item -f @var{n}
-Skip @var{n} fields before comparing lines. The definition of fields
-is similar to @command{awk}'s default: nonwhitespace characters separated
-by runs of spaces and/or TABs.
-
-@item -s @var{n}
-Skip @var{n} characters before comparing lines. Any fields specified with
-@option{-f} are skipped first.
-
-@item @var{inputfile}
-Data is read from the input file named on the command line, instead of from
-the standard input.
-
-@item @var{outputfile}
-The generated output is sent to the named output file, instead of to the
-standard output.
-@end table
-
-Normally @command{uniq} behaves as if both the @option{-d} and
-@option{-u} options are provided.
-
-@command{uniq} uses the
-@code{getopt()} library function
-(@pxref{Getopt Function})
-and the @code{join()} library function
-(@pxref{Join Function}).
-
-The program begins with a @code{usage()} function and then a brief outline of
-the options and their meanings in comments:
-
-@cindex @file{uniq.awk} program
-@example
-@c file eg/prog/uniq.awk
-@group
-# uniq.awk --- do uniq in awk
-#
-# Requires getopt() and join() library functions
-@end group
-@c endfile
-@ignore
-@c file eg/prog/uniq.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Updated August 2020 to current POSIX
-@c endfile
-@end ignore
-@c file eg/prog/uniq.awk
-
-function usage()
-@{
- print("Usage: uniq [-udc [-f fields] [-s chars]] " \
- "[ in [ out ]]") > "/dev/stderr"
- exit 1
-@}
-
-# -c count lines. overrides -d and -u
-# -d only repeated lines
-# -u only nonrepeated lines
-# -f n skip n fields
-# -s n skip n characters, skip fields first
-@c endfile
-@end example
-
-The POSIX standard for @command{uniq} allows options to start with
-@samp{+} as well as with @samp{-}. An initial @code{BEGIN} rule
-traverses the arguments changing any leading @samp{+} to @samp{-}
-so that the @code{getopt()} function can parse the options:
-
-@example
-@c file eg/prog/uniq.awk
-# As of 2020, '+' can be used as the option character in addition to '-'
-# Previously allowed use of -N to skip fields and +N to skip
-# characters is no longer allowed, and not supported by this version.
-
-BEGIN @{
- # Convert + to - so getopt can handle things
- for (i = 1; i < ARGC; i++) @{
- first = substr(ARGV[i], 1, 1)
- if (ARGV[i] == "--" || (first != "-" && first != "+"))
- break
- else if (first == "+")
- # Replace "+" with "-"
- ARGV[i] = "-" substr(ARGV[i], 2)
- @}
-@}
-@c endfile
-@end example
-
-The next @code{BEGIN} rule deals with the command-line arguments and options.
-If no options are supplied, then the default is taken, to print both
-repeated and nonrepeated lines. The output file, if provided, is assigned
-to @code{outputfile}. Early on, @code{outputfile} is initialized to the
-standard output, @file{/dev/stdout}:
-
-@example
-@c file eg/prog/uniq.awk
-BEGIN @{
- count = 1
- outputfile = "/dev/stdout"
- opts = "udcf:s:"
- while ((c = getopt(ARGC, ARGV, opts)) != -1) @{
- if (c == "u")
- non_repeated_only++
- else if (c == "d")
- repeated_only++
- else if (c == "c")
- do_count++
- else if (c == "f")
- fcount = Optarg + 0
- else if (c == "s")
- charcount = Optarg + 0
- else
- usage()
- @}
-
- for (i = 1; i < Optind; i++)
- ARGV[i] = ""
-
- if (repeated_only == 0 && non_repeated_only == 0)
- repeated_only = non_repeated_only = 1
-
- if (ARGC - Optind == 2) @{
- outputfile = ARGV[ARGC - 1]
- ARGV[ARGC - 1] = ""
- @}
-@}
-@c endfile
-@end example
-
-The following function, @code{are_equal()}, compares the current line,
-@code{$0}, to the previous line, @code{last}. It handles skipping fields
-and characters. If no field count and no character count are specified,
-@code{are_equal()} returns one or zero depending upon the result of a
-simple string comparison of @code{last} and @code{$0}.
-
-Otherwise, things get more complicated. If fields have to be skipped,
-each line is broken into an array using @code{split()} (@pxref{String
-Functions}); the desired fields are then joined back into a line
-using @code{join()}. The joined lines are stored in @code{clast} and
-@code{cline}. If no fields are skipped, @code{clast} and @code{cline}
-are set to @code{last} and @code{$0}, respectively. Finally, if
-characters are skipped, @code{substr()} is used to strip off the leading
-@code{charcount} characters in @code{clast} and @code{cline}. The two
-strings are then compared and @code{are_equal()} returns the result:
-
-@example
-@c file eg/prog/uniq.awk
-@group
-function are_equal( n, m, clast, cline, alast, aline)
-@{
- if (fcount == 0 && charcount == 0)
- return (last == $0)
-@end group
-
- if (fcount > 0) @{
- n = split(last, alast)
- m = split($0, aline)
- clast = join(alast, fcount+1, n)
- cline = join(aline, fcount+1, m)
- @} else @{
- clast = last
- cline = $0
- @}
- if (charcount) @{
- clast = substr(clast, charcount + 1)
- cline = substr(cline, charcount + 1)
- @}
-@group
-
- return (clast == cline)
-@}
-@end group
-@c endfile
-@end example
-
-The following two rules are the body of the program. The first one is
-executed only for the very first line of data. It sets @code{last} equal to
-@code{$0}, so that subsequent lines of text have something to be compared to.
-
-The second rule does the work. The variable @code{equal} is one or zero,
-depending upon the results of @code{are_equal()}'s comparison. If
@command{uniq}
-is counting repeated lines, and the lines are equal, then it increments the
@code{count} variable.
-Otherwise, it prints the line and resets @code{count},
-because the two lines are not equal.
-
-If @command{uniq} is not counting, and if the lines are equal, @code{count} is
incremented.
-Nothing is printed, as the point is to remove duplicates.
-Otherwise, if @command{uniq} is counting repeated lines and more than
-one line is seen, or if @command{uniq} is counting nonrepeated lines
-and only one line is seen, then the line is printed, and @code{count}
-is reset.
-
-Finally, similar logic is used in the @code{END} rule to print the final
-line of input data:
-
-@example
-@c file eg/prog/uniq.awk
-NR == 1 @{
- last = $0
- next
-@}
-
-@{
- equal = are_equal()
-
- if (do_count) @{ # overrides -d and -u
- if (equal)
- count++
- else @{
- printf("%4d %s\n", count, last) > outputfile
- last = $0
- count = 1 # reset
- @}
- next
- @}
-
- if (equal)
- count++
- else @{
- if ((repeated_only && count > 1) ||
- (non_repeated_only && count == 1))
- print last > outputfile
- last = $0
- count = 1
- @}
-@}
-
-END @{
- if (do_count)
- printf("%4d %s\n", count, last) > outputfile
-@group
- else if ((repeated_only && count > 1) ||
- (non_repeated_only && count == 1))
- print last > outputfile
- close(outputfile)
-@}
-@end group
-@c endfile
-@end example
-
-As a side note, this program does not follow our recommended convention of
naming
-global variables with a leading capital letter. Doing that would
-make the program a little easier to follow.
-
-@ifset FOR_PRINT
-@cindex Kernighan, Brian @subentry quotes
-The logic for choosing which lines to print represents a @dfn{state
-machine}, which is ``a device which can be in one of a set number
-of stable conditions depending on its previous condition and on the
-present values of its inputs.''@footnote{This definition is from
-@uref{https://www.lexico.com/en/definition/state_machine}.} Brian
-Kernighan suggests that ``an alternative approach to state machines is
-to just read the input into an array, then use indexing. It's almost
-always easier code, and for most inputs where you would use this, just
-as fast.'' Consider how to rewrite the logic to follow this suggestion.
-@end ifset
-
-
-@node Wc Program
-@subsection Counting Things
-
-@cindex counting words, lines, characters, and bytes
-@cindex input files @subentry counting elements in
-@cindex words @subentry counting
-@cindex characters @subentry counting
-@cindex lines @subentry counting
-@cindex bytes @subentry counting
-@cindex @command{wc} utility
-The @command{wc} (word count) utility counts lines, words, characters
-and bytes in one or more input files.
-
-@menu
-* Bytes vs. Characters:: Modern character sets.
-* Using extensions:: A brief intro to extensions.
-* @command{wc} program:: Code for @file{wc.awk}.
-@end menu
-
-@node Bytes vs. Characters
-@subsubsection Modern Character Sets
-
-In the early days of computing, single bytes were used for storing
-characters. The most common character sets were ASCII and EBCDIC,
-which each provided all the English upper- and lowercase letters, the 10
-Hindu-Arabic numerals from 0 through 9, and a number of other standard
-punctuation and control characters.
-
-Today, the most popular character set in use is Unicode (of which ASCII
-is a pure subset). Unicode provides tens of thousands of unique characters
-(called @dfn{code points}) to cover most existing human languages (living
-and dead) and a number of nonhuman ones as well (such as Klingon and
-J.R.R.@: Tolkien's elvish languages).
-
-To save space in files, Unicode code points are @dfn{encoded}, where each
-character takes from one to four bytes in the file. UTF-8 is possibly
-the most popular of such @dfn{multibyte encodings}.
-
-The POSIX standard requires that @command{awk} function in terms
-of characters, not bytes. Thus in @command{gawk}, @code{length()},
-@code{substr()}, @code{split()}, @code{match()} and the other string
-functions (@pxref{String Functions}) all work in terms of characters in
-the local character set, and not in terms of bytes. (Not all @command{awk}
-implementations do so, though).
-
-There is no standard, built-in way to distinguish characters from bytes
-in an @command{awk} program. For an @command{awk} implementation of
-@command{wc}, which needs to make such a distinction, we will have to
-use an external extension.
-
-@node Using extensions
-@subsubsection A Brief Introduction To Extensions
-
-Loadable extensions are presented in full detail in @ref{Dynamic Extensions}.
-They provide a way to add functions to @command{gawk} which can call
-out to other facilities written in C or C++.
-
-For the purposes of
-@file{wc.awk}, it's enough to know that the extension is loaded
-with the @code{@@load} directive, and the additional function we
-will use is called @code{mbs_length()}. This function returns the
-number of bytes in a string, not the number of characters.
-
-The @code{"mbs"} extension comes from the @code{gawkextlib}
-project. @xref{gawkextlib} for more information.
-
-@node @command{wc} program
-@subsubsection Code for @file{wc.awk}
-
-The usage for @command{wc} is as follows:
-
-@display
-@command{wc} [@option{-lwcm}] [@var{files} @dots{}]
-@end display
-
-If no files are specified on the command line, @command{wc} reads its standard
-input. If there are multiple files, it also prints total counts for all
-the files. The options and their meanings are as follows:
-
-@table @code
-@item -c
-Count only bytes.
-Once upon a time, the @samp{c} in this option stood for ``characters.''
-But, as explained earlier, bytes and character are no longer synonymous
-with each other.
-
-@item -l
-Count only lines.
-
-@item -m
-Count only characters.
-
-@item -w
-Count only words.
-A ``word'' is a contiguous sequence of nonwhitespace characters, separated
-by spaces and/or TABs. Luckily, this is the normal way @command{awk} separates
-fields in its input data.
-@end table
-
-Implementing @command{wc} in @command{awk} is particularly elegant,
-because @command{awk} does a lot of the work for us; it splits lines into
-words (i.e., fields) and counts them, it counts lines (i.e., records),
-and it can easily tell us how long a line is in characters.
-
-This program uses the @code{getopt()} library function
-(@pxref{Getopt Function})
-and the file-transition functions
-(@pxref{Filetrans Function}).
-
-This version has one notable difference from older versions of
-@command{wc}: it always prints the counts in the order lines, words,
-characters and bytes. Older versions note the order of the @option{-l},
-@option{-w}, and @option{-c} options on the command line, and print the
-counts in that order. POSIX does not mandate this behavior, though.
-
-The @code{BEGIN} rule does the argument processing. The variable
-@code{print_total} is true if more than one file is named on the
-command line:
-
-@cindex @file{wc.awk} program
-@example
-@c file eg/prog/wc.awk
-# wc.awk --- count lines, words, characters, bytes
-@c endfile
-@ignore
-@c file eg/prog/wc.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised September 2020
-@c endfile
-@end ignore
-@c file eg/prog/wc.awk
-
-# Options:
-# -l only count lines
-# -w only count words
-# -c only count bytes
-# -m only count characters
-#
-# Default is to count lines, words, bytes
-#
-# Requires getopt() and file transition library functions
-# Requires mbs extension from gawkextlib
-
-@@load "mbs"
-
-BEGIN @{
- # let getopt() print a message about
- # invalid options. we ignore them
- while ((c = getopt(ARGC, ARGV, "lwcm")) != -1) @{
- if (c == "l")
- do_lines = 1
- else if (c == "w")
- do_words = 1
- else if (c == "c")
- do_bytes = 1
- else if (c == "m")
- do_chars = 1
- @}
- for (i = 1; i < Optind; i++)
- ARGV[i] = ""
-
- # if no options, do lines, words, bytes
- if (! do_lines && ! do_words && ! do_chars && ! do_bytes)
- do_lines = do_words = do_bytes = 1
-
- print_total = (ARGC - i > 1)
-@}
-@c endfile
-@end example
-
-The @code{beginfile()} function is simple; it just resets the counts of lines,
-words, characters and bytes to zero, and saves the current @value{FN} in
-@code{fname}:
-
-@example
-@c file eg/prog/wc.awk
-function beginfile(file)
-@{
- lines = words = chars = bytes = 0
- fname = FILENAME
-@}
-@c endfile
-@end example
-
-The @code{endfile()} function adds the current file's numbers to the
-running totals of lines, words, and characters. It then prints out those
-numbers for the file that was just read. It relies on @code{beginfile()}
-to reset the numbers for the following @value{DF}:
-
-@example
-@c file eg/prog/wc.awk
-function endfile(file)
-@{
- tlines += lines
- twords += words
- tchars += chars
- tbytes += bytes
- if (do_lines)
- printf "\t%d", lines
-@group
- if (do_words)
- printf "\t%d", words
-@end group
- if (do_chars)
- printf "\t%d", chars
- if (do_bytes)
- printf "\t%d", bytes
- printf "\t%s\n", fname
-@}
-@c endfile
-@end example
-
-There is one rule that is executed for each line. It adds the length of
-the record, plus one, to @code{chars}. Adding one plus the record length
-is needed because the newline character separating records (the value
-of @code{RS}) is not part of the record itself, and thus not included
-in its length. Similarly, it adds the length of the record in bytes,
-plus one, to @code{bytes}. Next, @code{lines} is incremented for each
-line read, and @code{words} is incremented by the value of @code{NF},
-which is the number of ``words'' on this line:
-
-@example
-@c file eg/prog/wc.awk
-# do per line
-@{
- chars += length($0) + 1 # get newline
- bytes += mbs_length($0) + 1
- lines++
- words += NF
-@}
-@c endfile
-@end example
-
-Finally, the @code{END} rule simply prints the totals for all the files:
-
-@example
-@c file eg/prog/wc.awk
-END @{
- if (print_total) @{
- if (do_lines)
- printf "\t%d", tlines
- if (do_words)
- printf "\t%d", twords
- if (do_chars)
- printf "\t%d", tchars
- if (do_bytes)
- printf "\t%d", tbytes
- print "\ttotal"
- @}
-@}
-@c endfile
-@end example
-
-@node Miscellaneous Programs
-@section A Grab Bag of @command{awk} Programs
-
-This @value{SECTION} is a large ``grab bag'' of miscellaneous programs.
-We hope you find them both interesting and enjoyable.
-
-@menu
-* Dupword Program:: Finding duplicated words in a document.
-* Alarm Program:: An alarm clock.
-* Translate Program:: A program similar to the @command{tr} utility.
-* Labels Program:: Printing mailing labels.
-* Word Sorting:: A program to produce a word usage count.
-* History Sorting:: Eliminating duplicate entries from a history
- file.
-* Extract Program:: Pulling out programs from Texinfo source
- files.
-* Simple Sed:: A Simple Stream Editor.
-* Igawk Program:: A wrapper for @command{awk} that includes
- files.
-* Anagram Program:: Finding anagrams from a dictionary.
-* Signature Program:: People do amazing things with too much time on
- their hands.
-@end menu
-
-@node Dupword Program
-@subsection Finding Duplicated Words in a Document
-
-@cindex words @subentry duplicate, searching for
-@cindex searching @subentry for words
-@cindex documents, searching
-A common error when writing large amounts of prose is to accidentally
-duplicate words. Typically you will see this in text as something like ``the
-the program does the following@dots{}'' When the text is online, often
-the duplicated words occur at the end of one line and at the
-@iftex
-the
-@end iftex
-beginning of
-another, making them very difficult to spot.
-@c as here!
-
-This program, @file{dupword.awk}, scans through a file one line at a time
-and looks for adjacent occurrences of the same word. It also saves the last
-word on a line (in the variable @code{prev}) for comparison with the first
-word on the next line.
-
-@cindex Texinfo
-The first two statements make sure that the line is all lowercase,
-so that, for example, ``The'' and ``the'' compare equal to each other.
-The next statement replaces nonalphanumeric and nonwhitespace characters
-with spaces, so that punctuation does not affect the comparison either.
-The characters are replaced with spaces so that formatting controls
-don't create nonsense words (e.g., the Texinfo @samp{@@code@{NF@}}
-becomes @samp{codeNF} if punctuation is simply deleted). The record is
-then resplit into fields, yielding just the actual words on the line,
-and ensuring that there are no empty fields.
-
-If there are no fields left after removing all the punctuation, the
-current record is skipped. Otherwise, the program loops through each
-word, comparing it to the previous one:
-
-@cindex @file{dupword.awk} program
-@example
-@c file eg/prog/dupword.awk
-# dupword.awk --- find duplicate words in text
-@c endfile
-@ignore
-@c file eg/prog/dupword.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# December 1991
-# Revised October 2000
-
-@c endfile
-@end ignore
-@c file eg/prog/dupword.awk
-@{
- $0 = tolower($0)
- gsub(/[^[:alnum:][:blank:]]/, " ");
- $0 = $0 # re-split
- if (NF == 0)
- next
- if ($1 == prev)
- printf("%s:%d: duplicate %s\n",
- FILENAME, FNR, $1)
- for (i = 2; i <= NF; i++)
- if ($i == $(i-1))
- printf("%s:%d: duplicate %s\n",
- FILENAME, FNR, $i)
- prev = $NF
-@}
-@c endfile
-@end example
-
-@node Alarm Program
-@subsection An Alarm Clock Program
-@cindex insomnia, cure for
-@cindex Robbins @subentry Arnold
-@quotation
-@i{Nothing cures insomnia like a ringing alarm clock.}
-@author Arnold Robbins
-@end quotation
-@cindex Quanstrom, Erik
-@ignore
-Date: Sat, 15 Feb 2014 16:47:09 -0500
-Subject: Re: 9atom install question
-Message-ID: <l2jcvx6j6mey60xnrkb0hhob.1392500829294@email.android.com>
-From: Erik Quanstrom <quanstro@quanstro.net>
-To: Aharon Robbins <arnold@skeeve.com>
-
-yes.
-
-- erik
-
-Aharon Robbins <arnold@skeeve.com> wrote:
-
->> sleep is for web developers.
->
->Can I quote you, in the gawk manual?
->
->Thanks,
->
->Arnold
-@end ignore
-@quotation
-@i{Sleep is for web developers.}
-@author Erik Quanstrom
-@end quotation
-
-@cindex time @subentry alarm clock example program
-@cindex alarm clock example program
-The following program is a simple ``alarm clock'' program.
-You give it a time of day and an optional message. At the specified time,
-it prints the message on the standard output. In addition, you can give it
-the number of times to repeat the message as well as a delay between
-repetitions.
-
-This program uses the @code{getlocaltime()} function from
-@ref{Getlocaltime Function}.
-
-@cindex ASCII
-All the work is done in the @code{BEGIN} rule. The first part is argument
-checking and setting of defaults: the delay, the count, and the message to
-print. If the user supplied a message without the ASCII BEL
-character (known as the ``alert'' character, @code{"\a"}), then it is added to
-the message. (On many systems, printing the ASCII BEL generates an
-audible alert. Thus, when the alarm goes off, the system calls attention
-to itself in case the user is not looking at the computer.)
-Just for a change, this program uses a @code{switch} statement
-(@pxref{Switch Statement}), but the processing could be done with a series of
-@code{if}-@code{else} statements instead.
-Here is the program:
-
-@cindex @file{alarm.awk} program
-@example
-@c file eg/prog/alarm.awk
-# alarm.awk --- set an alarm
-#
-# Requires getlocaltime() library function
-@c endfile
-@ignore
-@c file eg/prog/alarm.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised December 2010
-
-@c endfile
-@end ignore
-@c file eg/prog/alarm.awk
-# usage: alarm time [ "message" [ count [ delay ] ] ]
-
-BEGIN @{
- # Initial argument sanity checking
- usage1 = "usage: alarm time ['message' [count [delay]]]"
- usage2 = sprintf("\t(%s) time ::= hh:mm", ARGV[1])
-
- if (ARGC < 2) @{
- print usage1 > "/dev/stderr"
- print usage2 > "/dev/stderr"
- exit 1
- @}
- switch (ARGC) @{
- case 5:
- delay = ARGV[4] + 0
- # fall through
- case 4:
- count = ARGV[3] + 0
- # fall through
- case 3:
- message = ARGV[2]
- break
- default:
- if (ARGV[1] !~ /[[:digit:]]?[[:digit:]]:[[:digit:]]@{2@}/) @{
- print usage1 > "/dev/stderr"
- print usage2 > "/dev/stderr"
- exit 1
- @}
- break
- @}
-
- # set defaults for once we reach the desired time
- if (delay == 0)
- delay = 180 # 3 minutes
-@group
- if (count == 0)
- count = 5
-@end group
- if (message == "")
- message = sprintf("\aIt is now %s!\a", ARGV[1])
- else if (index(message, "\a") == 0)
- message = "\a" message "\a"
-@c endfile
-@end example
-
-The next @value{SECTION} of code turns the alarm time into hours and minutes,
-converts it (if necessary) to a 24-hour clock, and then turns that
-time into a count of the seconds since midnight. Next it turns the current
-time into a count of seconds since midnight. The difference between the two
-is how long to wait before setting off the alarm:
-
-@example
-@c file eg/prog/alarm.awk
- # split up alarm time
- split(ARGV[1], atime, ":")
- hour = atime[1] + 0 # force numeric
- minute = atime[2] + 0 # force numeric
-
- # get current broken down time
- getlocaltime(now)
-
- # if time given is 12-hour hours and it's after that
- # hour, e.g., `alarm 5:30' at 9 a.m. means 5:30 p.m.,
- # then add 12 to real hour
- if (hour < 12 && now["hour"] > hour)
- hour += 12
-
- # set target time in seconds since midnight
- target = (hour * 60 * 60) + (minute * 60)
-
- # get current time in seconds since midnight
- current = (now["hour"] * 60 * 60) + \
- (now["minute"] * 60) + now["second"]
-
- # how long to sleep for
- naptime = target - current
- if (naptime <= 0) @{
- print "alarm: time is in the past!" > "/dev/stderr"
- exit 1
- @}
-@c endfile
-@end example
-
-@cindex @command{sleep} utility
-Finally, the program uses the @code{system()} function
-(@pxref{I/O Functions})
-to call the @command{sleep} utility. The @command{sleep} utility simply pauses
-for the given number of seconds. If the exit status is not zero,
-the program assumes that @command{sleep} was interrupted and exits. If
-@command{sleep} exited with an OK status (zero), then the program prints the
-message in a loop, again using @command{sleep} to delay for however many
-seconds are necessary:
-
-@example
-@c file eg/prog/alarm.awk
- # zzzzzz..... go away if interrupted
- if (system(sprintf("sleep %d", naptime)) != 0)
- exit 1
-
- # time to notify!
- command = sprintf("sleep %d", delay)
- for (i = 1; i <= count; i++) @{
- print message
- # if sleep command interrupted, go away
- if (system(command) != 0)
- break
- @}
-
- exit 0
-@}
-@c endfile
-@end example
-
-@node Translate Program
-@subsection Transliterating Characters
-
-@cindex characters @subentry transliterating
-@cindex @command{tr} utility
-The system @command{tr} utility transliterates characters. For example, it is
-often used to map uppercase letters into lowercase for further processing:
-
-@example
-@var{generate data} | tr 'A-Z' 'a-z' | @var{process data} @dots{}
-@end example
-
-@command{tr} requires two lists of characters.@footnote{On some older
-systems, including Solaris, the system version of @command{tr} may require
-that the lists be written as range expressions enclosed in square brackets
-(@samp{[a-z]}) and quoted, to prevent the shell from attempting a
-@value{FN} expansion. This is not a feature.} When processing the input, the
-first character in the first list is replaced with the first character
-in the second list, the second character in the first list is replaced
-with the second character in the second list, and so on. If there are
-more characters in the ``from'' list than in the ``to'' list, the last
-character of the ``to'' list is used for the remaining characters in the
-``from'' list.
-
-Once upon a time,
-@c early or mid-1989!
-a user proposed adding a transliteration function
-to @command{gawk}.
-@c Wishing to avoid gratuitous new features,
-@c at least theoretically
-The following program was written to
-prove that character transliteration could be done with a user-level
-function. This program is not as complete as the system @command{tr} utility,
-but it does most of the job.
-
-The @command{translate} program was written long before @command{gawk}
-acquired the ability to split each character in a string into separate
-array elements. Thus, it makes repeated use of the @code{substr()},
-@code{index()}, and @code{gsub()} built-in functions (@pxref{String
-Functions}). There are two functions. The first, @code{stranslate()},
-takes three arguments:
-
-@table @code
-@item from
-A list of characters from which to translate
-
-@item to
-A list of characters to which to translate
-
-@item target
-The string on which to do the translation
-@end table
-
-Associative arrays make the translation part fairly easy. @code{t_ar} holds
-the ``to'' characters, indexed by the ``from'' characters. Then a simple
-loop goes through @code{from}, one character at a time. For each character
-in @code{from}, if the character appears in @code{target},
-it is replaced with the corresponding @code{to} character.
-
-The @code{translate()} function calls @code{stranslate()}, using @code{$0}
-as the target. The main program sets two global variables, @code{FROM} and
-@code{TO}, from the command line, and then changes @code{ARGV} so that
-@command{awk} reads from the standard input.
-
-Finally, the processing rule simply calls @code{translate()} for each record:
-
-@cindex @file{translate.awk} program
-@example
-@c file eg/prog/translate.awk
-# translate.awk --- do tr-like stuff
-@c endfile
-@ignore
-@c file eg/prog/translate.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# August 1989
-# February 2009 - bug fix
-
-@c endfile
-@end ignore
-@c file eg/prog/translate.awk
-# Bugs: does not handle things like tr A-Z a-z; it has
-# to be spelled out. However, if `to' is shorter than `from',
-# the last character in `to' is used for the rest of `from'.
-
-function stranslate(from, to, target, lf, lt, ltarget, t_ar, i, c,
- result)
-@{
- lf = length(from)
- lt = length(to)
- ltarget = length(target)
- for (i = 1; i <= lt; i++)
- t_ar[substr(from, i, 1)] = substr(to, i, 1)
- if (lt < lf)
- for (; i <= lf; i++)
- t_ar[substr(from, i, 1)] = substr(to, lt, 1)
- for (i = 1; i <= ltarget; i++) @{
- c = substr(target, i, 1)
- if (c in t_ar)
- c = t_ar[c]
- result = result c
- @}
- return result
-@}
-
-function translate(from, to)
-@{
- return $0 = stranslate(from, to, $0)
-@}
-
-# main program
-BEGIN @{
-@group
- if (ARGC < 3) @{
- print "usage: translate from to" > "/dev/stderr"
- exit
- @}
-@end group
- FROM = ARGV[1]
- TO = ARGV[2]
- ARGC = 2
- ARGV[1] = "-"
-@}
-
-@{
- translate(FROM, TO)
- print
-@}
-@c endfile
-@end example
-
-It is possible to do character transliteration in a user-level
-function, but it is not necessarily efficient, and we (the @command{gawk}
-developers) started to consider adding a built-in function. However,
-shortly after writing this program, we learned that Brian Kernighan
-had added the @code{toupper()} and @code{tolower()} functions to his
-@command{awk} (@pxref{String Functions}). These functions handle the
-vast majority of the cases where character transliteration is necessary,
-and so we chose to simply add those functions to @command{gawk} as well
-and then leave well enough alone.
-
-An obvious improvement to this program would be to set up the
-@code{t_ar} array only once, in a @code{BEGIN} rule. However, this
-assumes that the ``from'' and ``to'' lists
-will never change throughout the lifetime of the program.
-
-Another obvious improvement is to enable the use of ranges,
-such as @samp{a-z}, as allowed by the @command{tr} utility.
-Look at the code for @file{cut.awk} (@pxref{Cut Program})
-for inspiration.
-
-
-@node Labels Program
-@subsection Printing Mailing Labels
-
-@cindex printing @subentry mailing labels
-@cindex mailing labels, printing
-Here is a ``real-world''@footnote{``Real world'' is defined as
-``a program actually used to get something done.''}
-program. This
-script reads lists of names and
-addresses and generates mailing labels. Each page of labels has 20 labels
-on it, two across and 10 down. The addresses are guaranteed to be no more
-than five lines of data. Each address is separated from the next by a blank
-line.
-
-The basic idea is to read 20 labels' worth of data. Each line of each label
-is stored in the @code{line} array. The single rule takes care of filling
-the @code{line} array and printing the page when 20 labels have been read.
-
-The @code{BEGIN} rule simply sets @code{RS} to the empty string, so that
-@command{awk} splits records at blank lines
-(@pxref{Records}).
-It sets @code{MAXLINES} to 100, because 100 is the maximum number
-of lines on the page
-@iftex
-(@math{20 @cdot 5 = 100}).
-@end iftex
-@ifnottex
-@ifnotdocbook
-(20 * 5 = 100).
-@end ifnotdocbook
-@end ifnottex
-@docbook
-(20 ⋅ 5 = 100).
-@end docbook
-
-Most of the work is done in the @code{printpage()} function.
-The label lines are stored sequentially in the @code{line} array. But they
-have to print horizontally: @code{line[1]} next to @code{line[6]},
-@code{line[2]} next to @code{line[7]}, and so on. Two loops
-accomplish this. The outer loop, controlled by @code{i}, steps through
-every 10 lines of data; this is each row of labels. The inner loop,
-controlled by @code{j}, goes through the lines within the row.
-As @code{j} goes from 0 to 4, @samp{i+j} is the @code{j}th line in
-the row, and @samp{i+j+5} is the entry next to it. The output ends up
-looking something like this:
-
-@example
-line 1 line 6
-line 2 line 7
-line 3 line 8
-line 4 line 9
-line 5 line 10
-@dots{}
-@end example
-
-@noindent
-The @code{printf} format string @samp{%-41s} left-aligns
-the data and prints it within a fixed-width field.
-
-As a final note, an extra blank line is printed at lines 21 and 61, to keep
-the output lined up on the labels. This is dependent on the particular
-brand of labels in use when the program was written. You will also note
-that there are two blank lines at the top and two blank lines at the bottom.
-
-The @code{END} rule arranges to flush the final page of labels; there may
-not have been an even multiple of 20 labels in the data:
-
-@cindex @file{labels.awk} program
-@example
-@c file eg/prog/labels.awk
-# labels.awk --- print mailing labels
-@c endfile
-@ignore
-@c file eg/prog/labels.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# June 1992
-# December 2010, minor edits
-@c endfile
-@end ignore
-@c file eg/prog/labels.awk
-
-# Each label is 5 lines of data that may have blank lines.
-# The label sheets have 2 blank lines at the top and 2 at
-# the bottom.
-
-BEGIN @{ RS = "" ; MAXLINES = 100 @}
-
-function printpage( i, j)
-@{
- if (Nlines <= 0)
- return
-
- printf "\n\n" # header
-
- for (i = 1; i <= Nlines; i += 10) @{
- if (i == 21 || i == 61)
- print ""
- for (j = 0; j < 5; j++) @{
- if (i + j > MAXLINES)
- break
- printf " %-41s %s\n", line[i+j], line[i+j+5]
- @}
- print ""
- @}
-
- printf "\n\n" # footer
-
- delete line
-@}
-
-# main rule
-@{
- if (Count >= 20) @{
- printpage()
- Count = 0
- Nlines = 0
- @}
- n = split($0, a, "\n")
- for (i = 1; i <= n; i++)
- line[++Nlines] = a[i]
- for (; i <= 5; i++)
- line[++Nlines] = ""
- Count++
-@}
-
-END @{
- printpage()
-@}
-@c endfile
-@end example
-
-@node Word Sorting
-@subsection Generating Word-Usage Counts
-
-@cindex words @subentry usage counts, generating
-
-When working with large amounts of text, it can be interesting to know
-how often different words appear. For example, an author may overuse
-certain words, in which case he or she might wish to find synonyms to
substitute
-for words that appear too often. This @value{SUBSECTION} develops a
-program for counting words and presenting the frequency information
-in a useful format.
-
-At first glance, a program like this would seem to do the job:
-
-@example
-# wordfreq-first-try.awk --- print list of word frequencies
-
-@{
- for (i = 1; i <= NF; i++)
- freq[$i]++
-@}
-
-@group
-END @{
- for (word in freq)
- printf "%s\t%d\n", word, freq[word]
-@}
-@end group
-@end example
-
-The program relies on @command{awk}'s default field-splitting
-mechanism to break each line up into ``words'' and uses an
-associative array named @code{freq}, indexed by each word, to count
-the number of times the word occurs. In the @code{END} rule,
-it prints the counts.
-
-This program has several problems that prevent it from being
-useful on real text files:
-
-@itemize @value{BULLET}
-@item
-The @command{awk} language considers upper- and lowercase characters to be
-distinct. Therefore, ``bartender'' and ``Bartender'' are not treated
-as the same word. This is undesirable, because words are capitalized
-if they begin sentences in normal text, and a frequency analyzer should
-not be sensitive to capitalization.
-
-@item
-Words are detected using the @command{awk} convention that fields are
-separated just by whitespace. Other characters in the input (except
-newlines) don't have any special meaning to @command{awk}. This means that
-punctuation characters count as part of words.
-
-@item
-The output does not come out in any useful order. You're more likely to be
-interested in which words occur most frequently or in having an alphabetized
-table of how frequently each word occurs.
-@end itemize
-
-@cindex @command{sort} utility
-The first problem can be solved by using @code{tolower()} to remove case
-distinctions. The second problem can be solved by using @code{gsub()}
-to remove punctuation characters. Finally, we solve the third problem
-by using the system @command{sort} utility to process the output of the
-@command{awk} script. Here is the new version of the program:
-
-@cindex @file{wordfreq.awk} program
-@example
-@c file eg/prog/wordfreq.awk
-# wordfreq.awk --- print list of word frequencies
-
-@{
- $0 = tolower($0) # remove case distinctions
- # remove punctuation
- gsub(/[^[:alnum:]_[:blank:]]/, "", $0)
- for (i = 1; i <= NF; i++)
- freq[$i]++
-@}
-
-@c endfile
-END @{
- for (word in freq)
- printf "%s\t%d\n", word, freq[word]
-@}
-@end example
-
-The regexp @code{/[^[:alnum:]_[:blank:]]/} might have been written
-@code{/[[:punct:]]/}, but then underscores would also be removed,
-and we want to keep them.
-
-Assuming we have saved this program in a file named @file{wordfreq.awk},
-and that the data is in @file{file1}, the following pipeline:
-
-@example
-awk -f wordfreq.awk file1 | sort -k 2nr
-@end example
-
-@noindent
-produces a table of the words appearing in @file{file1} in order of
-decreasing frequency.
-
-The @command{awk} program suitably massages the
-data and produces a word frequency table, which is not ordered.
-The @command{awk} script's output is then sorted by the @command{sort}
-utility and printed on the screen.
-
-The options given to @command{sort}
-specify a sort that uses the second field of each input line (skipping
-one field), that the sort keys should be treated as numeric quantities
-(otherwise @samp{15} would come before @samp{5}), and that the sorting
-should be done in descending (reverse) order.
-
-The @command{sort} could even be done from within the program, by changing
-the @code{END} action to:
-
-@example
-@c file eg/prog/wordfreq.awk
-END @{
- sort = "sort -k 2nr"
- for (word in freq)
- printf "%s\t%d\n", word, freq[word] | sort
- close(sort)
-@}
-@c endfile
-@end example
-
-This way of sorting must be used on systems that do not
-have true pipes at the command-line (or batch-file) level.
-See the general operating system documentation for more information on how
-to use the @command{sort} program.
-
-@node History Sorting
-@subsection Removing Duplicates from Unsorted Text
-
-@cindex lines @subentry duplicate, removing
-The @command{uniq} program
-(@pxref{Uniq Program})
-removes duplicate lines from @emph{sorted} data.
-
-Suppose, however, you need to remove duplicate lines from a @value{DF} but
-that you want to preserve the order the lines are in. A good example of
-this might be a shell history file. The history file keeps a copy of all
-the commands you have entered, and it is not unusual to repeat a command
-several times in a row. Occasionally you might want to compact the history
-by removing duplicate entries. Yet it is desirable to maintain the order
-of the original commands.
-
-This simple program does the job. It uses two arrays. The @code{data}
-array is indexed by the text of each line.
-For each line, @code{data[$0]} is incremented.
-If a particular line has not
-been seen before, then @code{data[$0]} is zero.
-In this case, the text of the line is stored in @code{lines[count]}.
-Each element of @code{lines} is a unique command, and the indices of
-@code{lines} indicate the order in which those lines are encountered.
-The @code{END} rule simply prints out the lines, in order:
-
-@cindex Rakitzis, Byron
-@cindex @file{histsort.awk} program
-@example
-@c file eg/prog/histsort.awk
-# histsort.awk --- compact a shell history file
-# Thanks to Byron Rakitzis for the general idea
-@c endfile
-@ignore
-@c file eg/prog/histsort.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-@c endfile
-@end ignore
-@c file eg/prog/histsort.awk
-
-@group
-@{
- if (data[$0]++ == 0)
- lines[++count] = $0
-@}
-@end group
-
-@group
-END @{
- for (i = 1; i <= count; i++)
- print lines[i]
-@}
-@end group
-@c endfile
-@end example
-
-This program also provides a foundation for generating other useful
-information. For example, using the following @code{print} statement in the
-@code{END} rule indicates how often a particular command is used:
-
-@example
-print data[lines[i]], lines[i]
-@end example
-
-@noindent
-This works because @code{data[$0]} is incremented each time a line is
-seen.
-
-@c rick@openfortress.nl, Tue, 24 Dec 2019 13:43:06 +0100
-Rick van Rein offers the following one-liner to do the same job of
-removing duplicates from unsorted text:
-
-@example
-awk '@{ if (! seen[$0]++) print @}'
-@end example
-
-This can be simplified even further, at the risk of becoming
-almost too obscure:
-
-@example
-awk '! seen[$0]++'
-@end example
-
-@noindent
-This version uses the expression as a pattern, relying on
-@command{awk}'s default action of printing the line when
-the pattern is true.
-
-@node Extract Program
-@subsection Extracting Programs from Texinfo Source Files
-
-@cindex Texinfo @subentry extracting programs from source files
-@cindex files @subentry Texinfo, extracting programs from
-@ifnotinfo
-Both this chapter and the previous chapter
-(@ref{Library Functions})
-present a large number of @command{awk} programs.
-@end ifnotinfo
-@ifinfo
-The nodes
-@ref{Library Functions},
-and @ref{Sample Programs},
-are the top level nodes for a large number of @command{awk} programs.
-@end ifinfo
-If you want to experiment with these programs, it is tedious to type
-them in by hand. Here we present a program that can extract parts of a
-Texinfo input file into separate files.
-
-@cindex Texinfo
-This @value{DOCUMENT} is written in
@uref{https://www.gnu.org/software/texinfo/, Texinfo},
-the GNU Project's document formatting language.
-A single Texinfo source file can be used to produce both
-printed documentation, with @TeX{}, and online documentation.
-@ifnotinfo
-(Texinfo is fully documented in the book
-@cite{Texinfo---The GNU Documentation Format},
-available from the Free Software Foundation,
-and also available @uref{https://www.gnu.org/software/texinfo/manual/texinfo/,
online}.)
-@end ifnotinfo
-@ifinfo
-(The Texinfo language is described fully, starting with
-@ref{Top, , Texinfo, texinfo,Texinfo---The GNU Documentation Format}.)
-@end ifinfo
-
-For our purposes, it is enough to know three things about Texinfo input
-files:
-
-@itemize @value{BULLET}
-@item
-The ``at'' symbol (@samp{@@}) is special in Texinfo, much as
-the backslash (@samp{\}) is in C
-or @command{awk}. Literal @samp{@@} symbols are represented in Texinfo source
-files as @samp{@@@@}.
-
-@item
-Comments start with either @samp{@@c} or @samp{@@comment}.
-The file-extraction program works by using special comments that start
-at the beginning of a line.
-
-@item
-Lines containing @samp{@@group} and @samp{@@end group} commands bracket
-example text that should not be split across a page boundary.
-(Unfortunately, @TeX{} isn't always smart enough to do things exactly right,
-so we have to give it some help.)
-@end itemize
-
-The following program, @file{extract.awk}, reads through a Texinfo source
-file and does two things, based on the special comments.
-Upon seeing @samp{@w{@@c system @dots{}}},
-it runs a command, by extracting the command text from the
-control line and passing it on to the @code{system()} function
-(@pxref{I/O Functions}).
-Upon seeing @samp{@@c file @var{filename}}, each subsequent line is sent to
-the file @var{filename}, until @samp{@@c endfile} is encountered.
-The rules in @file{extract.awk} match either @samp{@@c} or
-@samp{@@comment} by letting the @samp{omment} part be optional.
-Lines containing @samp{@@group} and @samp{@@end group} are simply removed.
-@file{extract.awk} uses the @code{join()} library function
-(@pxref{Join Function}).
-
-The example programs in the online Texinfo source for @cite{@value{TITLE}}
-(@file{gawktexi.in}) have all been bracketed inside @samp{file} and
-@samp{endfile} lines. The @command{gawk} distribution uses a copy of
-@file{extract.awk} to extract the sample programs and install many
-of them in a standard directory where @command{gawk} can find them.
-The Texinfo file looks something like this:
-
-@example
-@dots{}
-This program has a @@code@{BEGIN@} rule
-that prints a nice message:
-
-@@example
-@@c file examples/messages.awk
-BEGIN @@@{ print "Don't panic!" @@@}
-@@c endfile
-@@end example
-
-It also prints some final advice:
-
-@@example
-@@c file examples/messages.awk
-END @@@{ print "Always avoid bored archaeologists!" @@@}
-@@c endfile
-@@end example
-@dots{}
-@end example
-
-@file{extract.awk} begins by setting @code{IGNORECASE} to one, so that
-mixed upper- and lowercase letters in the directives won't matter.
-
-The first rule handles calling @code{system()}, checking that a command is
-given (@code{NF} is at least three) and also checking that the command
-exits with a zero exit status, signifying OK:
-
-@cindex @file{extract.awk} program
-@example
-@c file eg/prog/extract.awk
-# extract.awk --- extract files and run programs from Texinfo files
-@c endfile
-@ignore
-@c file eg/prog/extract.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised September 2000
-@c endfile
-@end ignore
-@c file eg/prog/extract.awk
-
-BEGIN @{ IGNORECASE = 1 @}
-
-/^@@c(omment)?[ \t]+system/ @{
- if (NF < 3) @{
- e = ("extract: " FILENAME ":" FNR)
- e = (e ": badly formed `system' line")
- print e > "/dev/stderr"
- next
- @}
- $1 = ""
- $2 = ""
- stat = system($0)
- if (stat != 0) @{
- e = ("extract: " FILENAME ":" FNR)
- e = (e ": warning: system returned " stat)
- print e > "/dev/stderr"
- @}
-@}
-@c endfile
-@end example
-
-@noindent
-The variable @code{e} is used so that the rule
-fits nicely on the @value{PAGE}.
-
-The second rule handles moving data into files. It verifies that a
-@value{FN} is given in the directive. If the file named is not the
-current file, then the current file is closed. Keeping the current file
-open until a new file is encountered allows the use of the @samp{>}
-redirection for printing the contents, keeping open-file management
-simple.
-
-The @code{for} loop does the work. It reads lines using @code{getline}
-(@pxref{Getline}).
-For an unexpected end-of-file, it calls the @code{@w{unexpected_eof()}}
-function. If the line is an ``endfile'' line, then it breaks out of
-the loop.
-If the line is an @samp{@@group} or @samp{@@end group} line, then it
-ignores it and goes on to the next line.
-Similarly, comments within examples are also ignored.
-
-Most of the work is in the following few lines. If the line has no @samp{@@}
-symbols, the program can print it directly.
-Otherwise, each leading @samp{@@} must be stripped off.
-To remove the @samp{@@} symbols, the line is split into separate elements of
-the array @code{a}, using the @code{split()} function
-(@pxref{String Functions}).
-The @samp{@@} symbol is used as the separator character.
-Each element of @code{a} that is empty indicates two successive @samp{@@}
-symbols in the original line. For each two empty elements (@samp{@@@@} in
-the original file), we have to add a single @samp{@@} symbol back in.
-
-When the processing of the array is finished, @code{join()} is called with the
-value of @code{SUBSEP} (@pxref{Multidimensional}),
-to rejoin the pieces back into a single
-line. That line is then printed to the output file:
-
-@example
-@c file eg/prog/extract.awk
-/^@@c(omment)?[ \t]+file/ @{
- if (NF != 3) @{
- e = ("extract: " FILENAME ":" FNR ": badly formed `file' line")
- print e > "/dev/stderr"
- next
- @}
- if ($3 != curfile) @{
- if (curfile != "")
- filelist[curfile] = 1 # save to close later
- curfile = $3
- @}
-
- for (;;) @{
- if ((getline line) <= 0)
- unexpected_eof()
- if (line ~ /^@@c(omment)?[ \t]+endfile/)
- break
- else if (line ~ /^@@(end[ \t]+)?group/)
- continue
- else if (line ~ /^@@c(omment+)?[ \t]+/)
- continue
- if (index(line, "@@") == 0) @{
- print line > curfile
- continue
- @}
- n = split(line, a, "@@")
- # if a[1] == "", means leading @@,
- # don't add one back in.
- for (i = 2; i <= n; i++) @{
- if (a[i] == "") @{ # was an @@@@
- a[i] = "@@"
- if (a[i+1] == "")
- i++
- @}
- @}
-@group
- print join(a, 1, n, SUBSEP) > curfile
- @}
-@}
-@end group
-@c endfile
-@end example
-
-An important thing to note is the use of the @samp{>} redirection.
-Output done with @samp{>} only opens the file once; it stays open and
-subsequent output is appended to the file
-(@pxref{Redirection}).
-This makes it easy to mix program text and explanatory prose for the same
-sample source file (as has been done here!) without any hassle. The file is
-only closed when a new @value{DF} name is encountered or at the end of the
-input file.
-
-When a new @value{FN} is encountered, instead of closing the file,
-the program saves the name of the current file in @code{filelist}.
-This makes it possible to interleave the code for more than one file in
-the Texinfo input file. (Previous versions of this program @emph{did}
-close the file. But because of the @samp{>} redirection, a file whose
-parts were not all one after the other ended up getting clobbered.)
-An @code{END} rule then closes all the open files when processing
-is finished:
-
-@example
-@c file eg/prog/extract.awk
-@group
-END @{
- close(curfile) # close the last one
- for (f in filelist) # close all the rest
- close(f)
-@}
-@end group
-@c endfile
-@end example
-
-Finally, the function @code{@w{unexpected_eof()}} prints an appropriate
-error message and then exits:
-
-@example
-@c file eg/prog/extract.awk
-@group
-function unexpected_eof()
-@{
- printf("extract: %s:%d: unexpected EOF or error\n",
- FILENAME, FNR) > "/dev/stderr"
- exit 1
-@}
-@end group
-@c endfile
-@end example
-
-@node Simple Sed
-@subsection A Simple Stream Editor
-
-@cindex @command{sed} utility
-@cindex stream editors
-The @command{sed} utility is a @dfn{stream editor}, a program that reads a
-stream of data, makes changes to it, and passes it on.
-It is often used to make global changes to a large file or to a stream
-of data generated by a pipeline of commands.
-Although @command{sed} is a complicated program in its own right, its most
common
-use is to perform global substitutions in the middle of a pipeline:
-
-@example
-@var{command1} < orig.data | sed 's/old/new/g' | @var{command2} > result
-@end example
-
-Here, @samp{s/old/new/g} tells @command{sed} to look for the regexp
-@samp{old} on each input line and globally replace it with the text
-@samp{new} (i.e., all the occurrences on a line). This is similar to
-@command{awk}'s @code{gsub()} function
-(@pxref{String Functions}).
-
-The following program, @file{awksed.awk}, accepts at least two command-line
-arguments: the pattern to look for and the text to replace it with. Any
-additional arguments are treated as @value{DF} names to process. If none
-are provided, the standard input is used:
-
-@cindex Brennan, Michael
-@cindex @command{awksed.awk} program
-@c @cindex simple stream editor
-@c @cindex stream editor, simple
-@example
-@c file eg/prog/awksed.awk
-# awksed.awk --- do s/foo/bar/g using just print
-# Thanks to Michael Brennan for the idea
-@c endfile
-@ignore
-@c file eg/prog/awksed.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# August 1995
-@c endfile
-@end ignore
-@c file eg/prog/awksed.awk
-
-function usage()
-@{
- print "usage: awksed pat repl [files...]" > "/dev/stderr"
- exit 1
-@}
-
-@group
-BEGIN @{
- # validate arguments
- if (ARGC < 3)
- usage()
-@end group
-
- RS = ARGV[1]
- ORS = ARGV[2]
-
- # don't use arguments as files
- ARGV[1] = ARGV[2] = ""
-@}
-
-@group
-# look ma, no hands!
-@{
- if (RT == "")
- printf "%s", $0
- else
- print
-@}
-@end group
-@c endfile
-@end example
-
-The program relies on @command{gawk}'s ability to have @code{RS} be a regexp,
-as well as on the setting of @code{RT} to the actual text that terminates the
-record (@pxref{Records}).
-
-The idea is to have @code{RS} be the pattern to look for. @command{gawk}
-automatically sets @code{$0} to the text between matches of the pattern.
-This is text that we want to keep, unmodified. Then, by setting @code{ORS}
-to the replacement text, a simple @code{print} statement outputs the
-text we want to keep, followed by the replacement text.
-
-There is one wrinkle to this scheme, which is what to do if the last record
-doesn't end with text that matches @code{RS}. Using a @code{print}
-statement unconditionally prints the replacement text, which is not correct.
-However, if the file did not end in text that matches @code{RS}, @code{RT}
-is set to the null string. In this case, we can print @code{$0} using
-@code{printf}
-(@pxref{Printf}).
-
-The @code{BEGIN} rule handles the setup, checking for the right number
-of arguments and calling @code{usage()} if there is a problem. Then it sets
-@code{RS} and @code{ORS} from the command-line arguments and sets
-@code{ARGV[1]} and @code{ARGV[2]} to the null string, so that they are
-not treated as @value{FN}s
-(@pxref{ARGC and ARGV}).
-
-The @code{usage()} function prints an error message and exits.
-Finally, the single rule handles the printing scheme outlined earlier,
-using @code{print} or @code{printf} as appropriate, depending upon the
-value of @code{RT}.
-
-@node Igawk Program
-@subsection An Easy Way to Use Library Functions
-
-@cindex libraries of @command{awk} functions @subentry example program for
using
-@cindex functions @subentry library @subentry example program for using
-In @ref{Include Files}, we saw how @command{gawk} provides a built-in
-file-inclusion capability. However, this is a @command{gawk} extension.
-This @value{SECTION} provides the motivation for making file inclusion
-available for standard @command{awk}, and shows how to do it using a
-combination of shell and @command{awk} programming.
-
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-Using library functions in @command{awk} can be very beneficial. It
-encourages code reuse and the writing of general functions. Programs are
-smaller and therefore clearer.
-However, using library functions is only easy when writing @command{awk}
-programs; it is painful when running them, requiring multiple @option{-f}
-options. If @command{gawk} is unavailable, then so too is the @env{AWKPATH}
-environment variable and the ability to put @command{awk} functions into a
-library directory (@pxref{Options}).
-It would be nice to be able to write programs in the following manner:
-
-@example
-# library functions
-@@include getopt.awk
-@@include join.awk
-@dots{}
-
-# main program
-BEGIN @{
- while ((c = getopt(ARGC, ARGV, "a:b:cde")) != -1)
- @dots{}
- @dots{}
-@}
-@end example
-
-The following program, @file{igawk.sh}, provides this service.
-It simulates @command{gawk}'s searching of the @env{AWKPATH} variable
-and also allows @dfn{nested} includes (i.e., a file that is included
-with @code{@@include} can contain further @code{@@include} statements).
-@command{igawk} makes an effort to only include files once, so that nested
-includes don't accidentally include a library function twice.
-
-@command{igawk} should behave just like @command{gawk} externally. This
-means it should accept all of @command{gawk}'s command-line arguments,
-including the ability to have multiple source files specified via
-@option{-f} and the ability to mix command-line and library source files.
-
-The program is written using the POSIX Shell (@command{sh}) command
-language.@footnote{Fully explaining the @command{sh} language is beyond
-the scope of this book. We provide some minimal explanations, but see
-a good shell programming book if you wish to understand things in more
-depth.} It works as follows:
-
-@enumerate
-@item
-Loop through the arguments, saving anything that doesn't represent
-@command{awk} source code for later, when the expanded program is run.
-
-@item
-For any arguments that do represent @command{awk} text, put the arguments into
-a shell variable that will be expanded. There are two cases:
-
-@enumerate a
-@item
-Literal text, provided with @option{-e} or @option{--source}. This
-text is just appended directly.
-
-@item
-Source @value{FN}s, provided with @option{-f}. We use a neat trick and
-append @samp{@@include @var{filename}} to the shell variable's contents.
-Because the file-inclusion program works the way @command{gawk} does, this
-gets the text of the file included in the program at the correct point.
-@end enumerate
-
-@item
-Run an @command{awk} program (naturally) over the shell variable's contents to
expand
-@code{@@include} statements. The expanded program is placed in a second
-shell variable.
-
-@item
-Run the expanded program with @command{gawk} and any other original
command-line
-arguments that the user supplied (such as the @value{DF} names).
-@end enumerate
-
-This program uses shell variables extensively: for storing command-line
arguments and
-the text of the @command{awk} program that will expand the user's program, for
the
-user's original program, and for the expanded program. Doing so removes some
-potential problems that might arise were we to use temporary files instead,
-at the cost of making the script somewhat more complicated.
-
-The initial part of the program turns on shell tracing if the first
-argument is @samp{debug}.
-
-The next part loops through all the command-line arguments.
-There are several cases of interest:
-
-@c @asis for docbook
-@table @asis
-@item @option{--}
-This ends the arguments to @command{igawk}. Anything else should be passed on
-to the user's @command{awk} program without being evaluated.
-
-@item @option{-W}
-This indicates that the next option is specific to @command{gawk}. To make
-argument processing easier, the @option{-W} is appended to the front of the
-remaining arguments and the loop continues. (This is an @command{sh}
-programming trick. Don't worry about it if you are not familiar with
-@command{sh}.)
-
-@item @option{-v}, @option{-F}
-These are saved and passed on to @command{gawk}.
-
-@item @option{-f}, @option{--file}, @option{--file=}, @option{-Wfile=}
-The @value{FN} is appended to the shell variable @code{program} with an
-@code{@@include} statement.
-The @command{expr} utility is used to remove the leading option part of the
-argument (e.g., @samp{--file=}).
-(Typical @command{sh} usage would be to use the @command{echo} and
@command{sed}
-utilities to do this work. Unfortunately, some versions of @command{echo}
evaluate
-escape sequences in their arguments, possibly mangling the program text.
-Using @command{expr} avoids this problem.)
-
-@item @option{--source}, @option{--source=}, @option{-Wsource=}
-The source text is appended to @code{program}.
-
-@item @option{--version}, @option{-Wversion}
-@command{igawk} prints its version number, runs @samp{gawk --version}
-to get the @command{gawk} version information, and then exits.
-@end table
-
-If none of the @option{-f}, @option{--file}, @option{-Wfile},
@option{--source},
-or @option{-Wsource} arguments are supplied, then the first nonoption argument
-should be the @command{awk} program. If there are no command-line
-arguments left, @command{igawk} prints an error message and exits.
-Otherwise, the first argument is appended to @code{program}.
-In any case, after the arguments have been processed,
-the shell variable
-@code{program} contains the complete text of the original @command{awk}
-program.
-
-The program is as follows:
-
-@cindex @code{igawk.sh} program
-@example
-@c file eg/prog/igawk.sh
-#! /bin/sh
-# igawk --- like gawk but do @@include processing
-@c endfile
-@ignore
-@c file eg/prog/igawk.sh
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# July 1993
-# December 2010, minor edits
-@c endfile
-@end ignore
-@c file eg/prog/igawk.sh
-
-if [ "$1" = debug ]
-then
- set -x
- shift
-fi
-
-# A literal newline, so that program text is formatted correctly
-n='
-'
-
-# Initialize variables to empty
-program=
-opts=
-
-while [ $# -ne 0 ] # loop over arguments
-do
- case $1 in
- --) shift
- break ;;
-
- -W) shift
- # The $@{x?'message here'@} construct prints a
- # diagnostic if $x is the null string
- set -- -W"$@{@@?'missing operand'@}"
- continue ;;
-
- -[vF]) opts="$opts $1 '$@{2?'missing operand'@}'"
- shift ;;
-
- -[vF]*) opts="$opts '$1'" ;;
-
- -f) program="$program$n@@include $@{2?'missing operand'@}"
- shift ;;
-
- -f*) f=$(expr "$1" : '-f\(.*\)')
- program="$program$n@@include $f" ;;
-
- -[W-]file=*)
- f=$(expr "$1" : '-.file=\(.*\)')
- program="$program$n@@include $f" ;;
-
- -[W-]file)
- program="$program$n@@include $@{2?'missing operand'@}"
- shift ;;
-
- -[W-]source=*)
- t=$(expr "$1" : '-.source=\(.*\)')
- program="$program$n$t" ;;
-
- -[W-]source)
- program="$program$n$@{2?'missing operand'@}"
- shift ;;
-
- -[W-]version)
- echo igawk: version 3.0 1>&2
- gawk --version
- exit 0 ;;
-
- -[W-]*) opts="$opts '$1'" ;;
-
- *) break ;;
- esac
- shift
-done
-
-if [ -z "$program" ]
-then
- program=$@{1?'missing program'@}
- shift
-fi
-
-# At this point, `program' has the program.
-@c endfile
-@end example
-
-The @command{awk} program to process @code{@@include} directives
-is stored in the shell variable @code{expand_prog}. Doing this keeps
-the shell script readable. The @command{awk} program
-reads through the user's program, one line at a time, using @code{getline}
-(@pxref{Getline}). The input
-@value{FN}s and @code{@@include} statements are managed using a stack.
-As each @code{@@include} is encountered, the current @value{FN} is
-``pushed'' onto the stack and the file named in the @code{@@include}
-directive becomes the current @value{FN}. As each file is finished,
-the stack is ``popped,'' and the previous input file becomes the current
-input file again. The process is started by making the original file
-the first one on the stack.
-
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-The @code{pathto()} function does the work of finding the full path to
-a file. It simulates @command{gawk}'s behavior when searching the
-@env{AWKPATH} environment variable
-(@pxref{AWKPATH Variable}).
-If a @value{FN} has a @samp{/} in it, no path search is done.
-Similarly, if the @value{FN} is @code{"-"}, then that string is
-used as-is. Otherwise,
-the @value{FN} is concatenated with the name of each directory in
-the path, and an attempt is made to open the generated @value{FN}.
-The only way to test if a file can be read in @command{awk} is to go
-ahead and try to read it with @code{getline}; this is what @code{pathto()}
-does.@footnote{On some very old versions of @command{awk}, the test
-@samp{getline junk < t} can loop forever if the file exists but is empty.}
-If the file can be read, it is closed and the @value{FN}
-is returned:
-
-@ignore
-An alternative way to test for the file's existence would be to call
-@samp{system("test -r " t)}, which uses the @command{test} utility to
-see if the file exists and is readable. The disadvantage to this method
-is that it requires creating an extra process and can thus be slightly
-slower.
-@end ignore
-
-@example
-@c file eg/prog/igawk.sh
-expand_prog='
-
-function pathto(file, i, t, junk)
-@{
- if (index(file, "/") != 0)
- return file
-
- if (file == "-")
- return file
-
- for (i = 1; i <= ndirs; i++) @{
- t = (pathlist[i] "/" file)
-@group
- if ((getline junk < t) > 0) @{
- # found it
- close(t)
- return t
- @}
-@end group
- @}
- return ""
-@}
-@c endfile
-@end example
-
-The main program is contained inside one @code{BEGIN} rule. The first thing it
-does is set up the @code{pathlist} array that @code{pathto()} uses. After
-splitting the path on @samp{:}, null elements are replaced with @code{"."},
-which represents the current directory:
-
-@example
-@c file eg/prog/igawk.sh
-BEGIN @{
- path = ENVIRON["AWKPATH"]
- ndirs = split(path, pathlist, ":")
- for (i = 1; i <= ndirs; i++) @{
- if (pathlist[i] == "")
- pathlist[i] = "."
- @}
-@c endfile
-@end example
-
-The stack is initialized with @code{ARGV[1]}, which will be
@code{"/dev/stdin"}.
-The main loop comes next. Input lines are read in succession. Lines that
-do not start with @code{@@include} are printed verbatim.
-If the line does start with @code{@@include}, the @value{FN} is in @code{$2}.
-@code{pathto()} is called to generate the full path. If it cannot, then the
program
-prints an error message and continues.
-
-The next thing to check is if the file is included already. The
-@code{processed} array is indexed by the full @value{FN} of each included
-file and it tracks this information for us. If the file is
-seen again, a warning message is printed. Otherwise, the new @value{FN} is
-pushed onto the stack and processing continues.
-
-Finally, when @code{getline} encounters the end of the input file, the file
-is closed and the stack is popped. When @code{stackptr} is less than zero,
-the program is done:
-
-@example
-@c file eg/prog/igawk.sh
- stackptr = 0
- input[stackptr] = ARGV[1] # ARGV[1] is first file
-
- for (; stackptr >= 0; stackptr--) @{
- while ((getline < input[stackptr]) > 0) @{
- if (tolower($1) != "@@include") @{
- print
- continue
- @}
- fpath = pathto($2)
- if (fpath == "") @{
- printf("igawk: %s:%d: cannot find %s\n",
- input[stackptr], FNR, $2) > "/dev/stderr"
- continue
- @}
- if (! (fpath in processed)) @{
- processed[fpath] = input[stackptr]
- input[++stackptr] = fpath # push onto stack
- @} else
- print $2, "included in", input[stackptr],
- "already included in",
- processed[fpath] > "/dev/stderr"
- @}
- close(input[stackptr])
- @}
-@}' # close quote ends `expand_prog' variable
-
-processed_program=$(gawk -- "$expand_prog" /dev/stdin << EOF
-$program
-EOF
-)
-@c endfile
-@end example
-
-The shell construct @samp{@var{command} << @var{marker}} is called
-a @dfn{here document}. Everything in the shell script up to the
-@var{marker} is fed to @var{command} as input. The shell processes
-the contents of the here document for variable and command substitution
-(and possibly other things as well, depending upon the shell).
-
-The shell construct @samp{$(@dots{})} is called @dfn{command substitution}.
-The output of the command inside the parentheses is substituted
-into the command line.
-Because the result is used in a variable assignment,
-it is saved as a single string, even if the results contain whitespace.
-
-The expanded program is saved in the variable @code{processed_program}.
-It's done in these steps:
-
-@enumerate
-@item
-Run @command{gawk} with the @code{@@include}-processing program (the
-value of the @code{expand_prog} shell variable) reading standard input.
-
-@item
-Standard input is the contents of the user's program,
-from the shell variable @code{program}.
-Feed its contents to @command{gawk} via a here document.
-
-@item
-Save the results of this processing in the shell variable
-@code{processed_program} by using command substitution.
-@end enumerate
-
-The last step is to call @command{gawk} with the expanded program,
-along with the original
-options and command-line arguments that the user supplied:
-
-@example
-@c file eg/prog/igawk.sh
-eval gawk $opts -- '"$processed_program"' '"$@@"'
-@c endfile
-@end example
-
-The @command{eval} command is a shell construct that reruns the shell's parsing
-process. This keeps things properly quoted.
-
-This version of @command{igawk} represents the fifth version of this program.
-There are four key simplifications that make the program work better:
-
-@itemize @value{BULLET}
-@item
-Using @code{@@include} even for the files named with @option{-f} makes building
-the initial collected @command{awk} program much simpler; all the
-@code{@@include} processing can be done once.
-
-@item
-Not trying to save the line read with @code{getline}
-in the @code{pathto()} function when testing for the
-file's accessibility for use with the main program simplifies things
-considerably.
-
-@item
-Using a @code{getline} loop in the @code{BEGIN} rule does it all in one
-place. It is not necessary to call out to a separate loop for processing
-nested @code{@@include} statements.
-
-@item
-Instead of saving the expanded program in a temporary file, putting it in a
shell variable
-avoids some potential security problems.
-This has the disadvantage that the script relies upon more features
-of the @command{sh} language, making it harder to follow for those who
-aren't familiar with @command{sh}.
-@end itemize
-
-Also, this program illustrates that it is often worthwhile to combine
-@command{sh} and @command{awk} programming together. You can usually
-accomplish quite a lot, without having to resort to low-level programming
-in C or C++, and it is frequently easier to do certain kinds of string
-and argument manipulation using the shell than it is in @command{awk}.
-
-Finally, @command{igawk} shows that it is not always necessary to add new
-features to a program; they can often be layered on
top.@footnote{@command{gawk}
-does @code{@@include} processing itself in order to support the use
-of @command{awk} programs as Web CGI scripts.}
-
-Before @command{gawk} acquired its built-in @code{@@include} mechanism,
-@command{igawk} and its manual page were installed as part of the regular
-@command{gawk} installation (@samp{make install}). This is no longer
-done, because it's no longer necessary. But we've kept the program in this
-@value{DOCUMENT} for its educational value.
-
-@node Anagram Program
-@subsection Finding Anagrams from a Dictionary
-
-@cindex anagrams, finding
-An interesting programming challenge is to
-search for @dfn{anagrams} in a
-word list (such as
-@file{/usr/share/dict/words} on many GNU/Linux systems).
-One word is an anagram of another if both words contain
-the same letters
-(e.g., ``babbling'' and ``blabbing'').
-
-Column 2, Problem C, of Jon Bentley's @cite{Programming Pearls}, Second
-Edition, presents an elegant algorithm. The idea is to give words that
-are anagrams a common signature, sort all the words together by their
-signatures, and then print them. Dr.@: Bentley observes that taking the
-letters in each word and sorting them produces those common signatures.
-
-The following program uses arrays of arrays to bring together
-words with the same signature and array sorting to print the words
-in sorted order:
-
-@cindex @file{anagram.awk} program
-@example
-@c file eg/prog/anagram.awk
-# anagram.awk --- An implementation of the anagram-finding algorithm
-# from Jon Bentley's "Programming Pearls," 2nd edition.
-# Addison Wesley, 2000, ISBN 0-201-65788-0.
-# Column 2, Problem C, section 2.8, pp 18-20.
-@c endfile
-@ignore
-@c file eg/prog/anagram.awk
-#
-# This program requires gawk 4.0 or newer.
-# Required gawk-specific features:
-# - True multidimensional arrays
-# - split() with "" as separator splits out individual characters
-# - asort() and asorti() functions
-#
-# See https://savannah.gnu.org/projects/gawk.
-#
-# Arnold Robbins
-# arnold@@skeeve.com
-# Public Domain
-# January, 2011
-@c endfile
-@end ignore
-@c file eg/prog/anagram.awk
-
-/'s$/ @{ next @} # Skip possessives
-@c endfile
-@end example
-
-The program starts with a header, and then a rule to skip
-possessives in the dictionary file. The next rule builds
-up the data structure. The first dimension of the array
-is indexed by the signature; the second dimension is the word
-itself:
-
-@example
-@c file eg/prog/anagram.awk
-@{
- key = word2key($1) # Build signature
- data[key][$1] = $1 # Store word with signature
-@}
-@c endfile
-@end example
-
-The @code{word2key()} function creates the signature.
-It splits the word apart into individual letters,
-sorts the letters, and then joins them back together:
-
-@example
-@c file eg/prog/anagram.awk
-# word2key --- split word apart into letters, sort, and join back together
-
-function word2key(word, a, i, n, result)
-@{
- n = split(word, a, "")
- asort(a)
-
- for (i = 1; i <= n; i++)
- result = result a[i]
-
- return result
-@}
-@c endfile
-@end example
-
-Finally, the @code{END} rule traverses the array
-and prints out the anagram lists. It sends the output
-to the system @command{sort} command because otherwise
-the anagrams would appear in arbitrary order:
-
-@example
-@c file eg/prog/anagram.awk
-END @{
- sort = "sort"
- for (key in data) @{
- # Sort words with same key
- nwords = asorti(data[key], words)
- if (nwords == 1)
- continue
-
- # And print. Minor glitch: trailing space at end of each line
- for (j = 1; j <= nwords; j++)
- printf("%s ", words[j]) | sort
- print "" | sort
- @}
- close(sort)
-@}
-@c endfile
-@end example
-
-Here is some partial output when the program is run:
-
-@example
-$ @kbd{gawk -f anagram.awk /usr/share/dict/words | grep '^b'}
-@dots{}
-babbled blabbed
-babbler blabber brabble
-babblers blabbers brabbles
-babbling blabbing
-babbly blabby
-babel bable
-babels beslab
-babery yabber
-@dots{}
-@end example
-
-
-@node Signature Program
-@subsection And Now for Something Completely Different
-
-@cindex signature program
-@cindex Brini, Davide
-The following program was written by Davide Brini
-@c (@email{dave_br@@gmx.com})
-and is published on @uref{http://backreference.org/2011/02/03/obfuscated-awk/,
-his website}.
-It serves as his signature in the Usenet group @code{comp.lang.awk}.
-He supplies the following copyright terms:
-
-@quotation
-Copyright @copyright{} 2008 Davide Brini
-
-Copying and distribution of the code published in this page, with or without
-modification, are permitted in any medium without royalty provided the
copyright
-notice and this notice are preserved.
-@end quotation
-
-Here is the program:
-
-@example
-@group
-awk 'BEGIN@{O="~"~"~";o="=="=="==";o+=+o;x=O""O;while(X++<=x+o+o)c=c"%c";
-printf c,(x-O)*(x-O),x*(x-o)-o,x*(x-O)+x-O-o,+x*(x-O)-x+o,X*(o*o+O)+x-O,
-X*(X-x)-o*o,(x+X)*o*o+o,x*(X-x)-O-O,x-O+(O+o+X+x)*(o+O),X*X-X*(x-O)-x+O,
-O+X*(o*(o+O)+O),+x+O+X*o,x*(x-o),(o+X+x)*o*o-(x-O-O),O+(X-x)*(X+O),x-O@}'
-@end group
-@end example
-
-@cindex Johansen, Chris
-We leave it to you to determine what the program does. (If you are
-truly desperate to understand it, see Chris Johansen's explanation,
-which is embedded in the Texinfo source file for this @value{DOCUMENT}.)
-
-@ignore
-To: "Arnold Robbins" <arnold@skeeve.com>
-Date: Sat, 20 Aug 2011 13:50:46 -0400
-Subject: The GNU Awk User's Guide, Section 13.3.11
-From: "Chris Johansen" <johansen@main.nc.us>
-Message-ID: <op.v0iw6wlv7finx3@asusodin.thrudvang.lan>
-
-Arnold, you don't know me, but we have a tenuous connection. My wife is
-Barbara A. Field, FAIA, GIT '65 (B. Arch.).
-
-I have had a couple of paper copies of "Effective Awk Programming" for
-years, and now I'm going through a Kindle version of "The GNU Awk User's
-Guide" again. When I got to section 13.3.11, I reformatted and lightly
-commented Davide Brin's signature script to understand its workings.
-
-It occurs to me that this might have pedagogical value as an example
-(although imperfect) of the value of whitespace and comments, and a
-starting point for that discussion. It certainly helped _me_ understand
-what's going on. You are welcome to it, as-is or modified (subject to
-Davide's constraints, of course, which I think I have met).
-
-If I were to include it in a future edition, I would put it at some
-distance from section 13.3.11, say, as a note or an appendix, so as not to
-be a "spoiler" to the puzzle.
-
-Best regards,
---
-Chris Johansen {johansen at main dot nc dot us}
- . . . collapsing the probability wave function, sending ripples of
-certainty through the space-time continuum.
-
-
-#! /usr/bin/gawk -f
-
-# From "13.3.11 And Now For Something Completely Different"
-#
https://www.gnu.org/software/gawk/manual/html_node/Signature-Program.html#Signature-Program
-
-# Copyright @copyright{} 2008 Davide Brini
-
-# Copying and distribution of the code published in this page, with
-# or without modification, are permitted in any medium without
-# royalty provided the copyright notice and this notice are preserved.
-
-BEGIN {
- O = "~" ~ "~"; # 1
- o = "==" == "=="; # 1
- o += +o; # 2
- x = O "" O; # 11
-
-
- while ( X++ <= x + o + o ) c = c "%c";
-
- # O is 1
- # o is 2
- # x is 11
- # X is 17
- # c is "%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c"
-
- printf c,
- ( x - O )*( x - O), # 100 d
- x*( x - o ) - o, # 97 a
- x*( x - O ) + x - O - o, # 118 v
- +x*( x - O ) - x + o, # 101 e
- X*( o*o + O ) + x - O, # 95 _
- X*( X - x ) - o*o, # 98 b
- ( x + X )*o*o + o, # 114 r
- x*( X - x ) - O - O, # 64 @
- x - O + ( O + o + X + x )*( o + O ), # 103 g
- X*X - X*( x - O ) - x + O, # 109 m
- O + X*( o*( o + O ) + O ), # 120 x
- +x + O + X*o, # 46 .
- x*( x - o), # 99 c
- ( o + X + x )*o*o - ( x - O - O ), # 111 0
- O + ( X - x )*( X + O ), # 109 m
- x - O # 10 \n
-}
-@end ignore
-
-@node Programs Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-The programs provided in this @value{CHAPTER}
-continue on the theme that reading programs is an excellent way to learn
-Good Programming.
-
-@item
-Using @samp{#!} to make @command{awk} programs directly runnable makes
-them easier to use. Otherwise, invoke the program using @samp{awk
--f @dots{}}.
-
-@item
-Reimplementing standard POSIX programs in @command{awk} is a pleasant
-exercise; @command{awk}'s expressive power lets you write such programs
-in relatively few lines of code, yet they are functionally complete
-and usable.
-
-@item
-One of standard @command{awk}'s weaknesses is working with individual
-characters. The ability to use @code{split()} with the empty string as
-the separator can considerably simplify such tasks.
-
-@item
-The examples here demonstrate the usefulness of the library
-functions from @ref{Library Functions}
-for a number of real (if small) programs.
-
-@item
-Besides reinventing POSIX wheels, other programs solved a selection of
-interesting problems, such as finding duplicate words in text, printing
-mailing labels, and finding anagrams.
-
-@end itemize
-
-@c EXCLUDE START
-@node Programs Exercises
-@section Exercises
-
-@enumerate
-@item
-Rewrite @file{cut.awk} (@pxref{Cut Program})
-using @code{split()} with @code{""} as the separator.
-
-@item
-In @ref{Egrep Program}, we mentioned that @samp{egrep -i} could be
-simulated in versions of @command{awk} without @code{IGNORECASE} by
-using @code{tolower()} on the line and the pattern. In a footnote there,
-we also mentioned that this solution has a bug: the translated line is
-output, and not the original one. Fix this problem.
-@c Exercise: Fix this, w/array and new line as key to original line
-
-@item
-The POSIX version of @command{id} takes options that control which
-information is printed. Modify the @command{awk} version
-(@pxref{Id Program}) to accept the same arguments and perform in the
-same way.
-
-@item
-The @file{split.awk} program (@pxref{Split Program}) assumes
-that letters are contiguous in the character set,
-which isn't true for EBCDIC systems.
-Fix this problem.
-(Hint: Consider a different way to work through the alphabet,
-without relying on @code{ord()} and @code{chr()}.)
-
-@item
-@cindex Kernighan, Brian @subentry quotes
-In @file{uniq.awk} (@pxref{Uniq Program}, the
-logic for choosing which lines to print represents a @dfn{state
-machine}, which is ``a device which can be in one of a set number of stable
-conditions depending on its previous condition and on the present values
-of its inputs.''@footnote{This definition is from
-@uref{https://www.lexico.com/en/definition/state_machine}.}
-Brian Kernighan suggests that
-``an alternative approach to state machines is to just read
-the input into an array, then use indexing. It's almost always
-easier code, and for most inputs where you would use this, just
-as fast.'' Rewrite the logic to follow this
-suggestion.
-
-
-@item
-Why can't the @file{wc.awk} program (@pxref{Wc Program}) just
-use the value of @code{FNR} in @code{endfile()}?
-Hint: Examine the code in @ref{Filetrans Function}.
-
-@ignore
-@command{wc} can't just use the value of @code{FNR} in
-@code{endfile()}. If you examine the code in @ref{Filetrans Function},
-you will see that @code{FNR} has already been reset by the time
-@code{endfile()} is called.
-@end ignore
-
-@item
-Manipulation of individual characters in the @command{translate} program
-(@pxref{Translate Program}) is painful using standard @command{awk}
-functions. Given that @command{gawk} can split strings into individual
-characters using @code{""} as the separator, how might you use this
-feature to simplify the program?
-
-@item
-The @file{extract.awk} program (@pxref{Extract Program}) was written
-before @command{gawk} had the @code{gensub()} function. Use it
-to simplify the code.
-
-@item
-Compare the performance of the @file{awksed.awk} program
-(@pxref{Simple Sed}) with the more straightforward:
-
-@example
-BEGIN @{
- pat = ARGV[1]
- repl = ARGV[2]
- ARGV[1] = ARGV[2] = ""
-@}
-
-@{ gsub(pat, repl); print @}
-@end example
-
-@item
-What are the advantages and disadvantages of @file{awksed.awk} versus
-the real @command{sed} utility?
-
-@ignore
- Advantage: egrep regexps
- speed (?)
- Disadvantage: no & in replacement text
-
-Others?
-@end ignore
-
-@item
-In @ref{Igawk Program}, we mentioned that not trying to save the line
-read with @code{getline} in the @code{pathto()} function when testing
-for the file's accessibility for use with the main program simplifies
-things considerably. What problem does this engender though?
-@c answer, reading from "-" or /dev/stdin
-
-@cindex search paths
-@cindex search paths @subentry for source files
-@cindex source files, search path for
-@cindex files @subentry source, search path for
-@cindex directories @subentry searching @subentry for source files
-@item
-As an additional example of the idea that it is not always necessary to
-add new features to a program, consider the idea of having two files in
-a directory in the search path:
-
-@table @file
-@item default.awk
-This file contains a set of default library functions, such
-as @code{getopt()} and @code{assert()}.
-
-@item site.awk
-This file contains library functions that are specific to a site or
-installation; i.e., locally developed functions.
-Having a separate file allows @file{default.awk} to change with
-new @command{gawk} releases, without requiring the system administrator to
-update it each time by adding the local functions.
-@end table
-
-One user
-@c Karl Berry, karl@ileaf.com, 10/95
-suggested that @command{gawk} be modified to automatically read these files
-upon startup. Instead, it would be very simple to modify @command{igawk}
-to do this. Since @command{igawk} can process nested @code{@@include}
-directives, @file{default.awk} could simply contain @code{@@include}
-statements for the desired library functions.
-Make this change.
-
-@item
-Modify @file{anagram.awk} (@pxref{Anagram Program}), to avoid
-the use of the external @command{sort} utility.
-
-@end enumerate
-@c EXCLUDE END
-
-@ifnotinfo
-@part @value{PART3}Moving Beyond Standard @command{awk} with @command{gawk}
-@end ifnotinfo
-
-@ifdocbook
-Part III focuses on features specific to @command{gawk}.
-It contains the following chapters:
-
-@itemize @value{BULLET}
-@item
-@ref{Namespaces}
-
-@item
-@ref{Advanced Features}
-
-@item
-@ref{Internationalization}
-
-@item
-@ref{Debugger}
-
-@item
-@ref{Arbitrary Precision Arithmetic}
-
-@item
-@ref{Dynamic Extensions}
-@end itemize
-@end ifdocbook
-
-@node Advanced Features
-@chapter Advanced Features of @command{gawk}
-@cindex @command{gawk} @subentry features @subentry advanced
-@cindex advanced features @subentry @command{gawk}
-@ignore
-Contributed by: Peter Langston <pud!psl@bellcore.bellcore.com>
-
- Found in Steve English's "signature" line:
-
-"Write documentation as if whoever reads it is a violent psychopath
-who knows where you live."
-@end ignore
-@cindex Langston, Peter
-@cindex English, Steve
-@quotation
-@i{Write documentation as if whoever reads it is
-a violent psychopath who knows where you live.}
-@author Steve English, as quoted by Peter Langston
-@end quotation
-
-This @value{CHAPTER} discusses advanced features in @command{gawk}.
-It's a bit of a ``grab bag'' of items that are otherwise unrelated
-to each other.
-First, we look at a command-line option that allows @command{gawk} to recognize
-nondecimal numbers in input data, not just in @command{awk}
-programs.
-Then, @command{gawk}'s special features for sorting arrays are presented.
-Next, two-way I/O, discussed briefly in earlier parts of this
-@value{DOCUMENT}, is described in full detail, along with the basics
-of TCP/IP networking. We then see how @command{gawk}
-can @dfn{profile} an @command{awk} program, making it possible to tune
-it for performance.
-Next, we present an experimental feature that allows you to preserve
-the values of @command{awk} variables and arrays between runs of
@command{gawk}.
-Finally, we discuss the philosophy behind @command{gawk}'s extension
-mechanism.
-
-@c FULLXREF ON
-Additional advanced features are discussed in separate @value{CHAPTER}s of
their
-own:
-
-@itemize @value{BULLET}
-@item
-@ref{Internationalization}, discusses how to internationalize
-your @command{awk} programs, so that they can speak multiple
-national languages.
-
-@item
-@ref{Debugger}, describes @command{gawk}'s built-in command-line
-debugger for debugging @command{awk} programs.
-
-@item
-@ref{Arbitrary Precision Arithmetic}, describes how you can use
-@command{gawk} to perform arbitrary-precision arithmetic.
-
-@item
-@ref{Dynamic Extensions},
-discusses the ability to dynamically add new built-in functions to
-@command{gawk}.
-@end itemize
-@c FULLXREF OFF
-
-@menu
-* Nondecimal Data:: Allowing nondecimal input data.
-* Boolean Typed Values:: Values with @code{number|bool} type.
-* Array Sorting:: Facilities for controlling array traversal and
- sorting arrays.
-* Two-way I/O:: Two-way communications with another process.
-* TCP/IP Networking:: Using @command{gawk} for network programming.
-* Profiling:: Profiling your @command{awk} programs.
-* Persistent Memory:: Preserving data between runs.
-* Extension Philosophy:: What should be built-in and what should not.
-* Advanced Features Summary:: Summary of advanced features.
-@end menu
-
-@node Nondecimal Data
-@section Allowing Nondecimal Input Data
-@cindex @option{--non-decimal-data} option
-@cindex advanced features @subentry nondecimal input data
-@cindex input @subentry data, nondecimal
-@cindex constants @subentry nondecimal
-
-If you run @command{gawk} with the @option{--non-decimal-data} option,
-you can have nondecimal values in your input data:
-
-@example
-$ @kbd{echo 0123 123 0x123 |}
-> @kbd{gawk --non-decimal-data '@{ printf "%d, %d, %d\n", $1, $2, $3 @}'}
-@print{} 83, 123, 291
-@end example
-
-For this feature to work, write your program so that
-@command{gawk} treats your data as numeric:
-
-@example
-$ @kbd{echo 0123 123 0x123 | gawk '@{ print $1, $2, $3 @}'}
-@print{} 0123 123 0x123
-@end example
-
-@noindent
-The @code{print} statement treats its expressions as strings.
-Although the fields can act as numbers when necessary,
-they are still strings, so @code{print} does not try to treat them
-numerically. You need to add zero to a field to force it to
-be treated as a number. For example:
-
-@example
-$ @kbd{echo 0123 123 0x123 | gawk --non-decimal-data '}
-> @kbd{@{ print $1, $2, $3}
-> @kbd{print $1 + 0, $2 + 0, $3 + 0 @}'}
-@print{} 0123 123 0x123
-@print{} 83 123 291
-@end example
-
-Because it is common to have decimal data with leading zeros, and because
-using this facility could lead to surprising results, the default is to leave
it
-disabled. If you want it, you must explicitly request it.
-
-@cindex programming conventions @subentry @option{--non-decimal-data} option
-@cindex @option{--non-decimal-data} option @subentry @code{strtonum()}
function and
-@cindex @code{strtonum()} function (@command{gawk}) @subentry
@option{--non-decimal-data} option and
-@quotation CAUTION
-@emph{Use of this option is not recommended.}
-It can break old programs very badly.
-Instead, use the @code{strtonum()} function to convert your data
-(@pxref{String Functions}).
-This makes your programs easier to write and easier to read, and
-leads to less surprising results.
-
-This option may disappear in a future version of @command{gawk}.
-@end quotation
-
-@node Boolean Typed Values
-@section Boolean Typed Values
-
-Scalar values in @command{awk} are either numbers or strings.
-@command{gawk} also supports values of type @code{regexp}
-(@pxref{Strong Regexp Constants}).
-
-As described in @ref{Truth Values}, Boolean values in @command{awk}
-don't have a separate type: a value counts as ``true'' if it is nonzero
-or non-null, and as ``false'' otherwise.
-
-When interchanging data with languages that do have a real Boolean type,
-using a standard format such as JSON or XML, the lack of a true Boolean
-type in @command{awk} is problematic.
-(See, for example, the @code{json} extension provided by
-@uref{https://sourceforge.net/projects/gawkextlib, the @code{gawkextlib}
project}.)
-
-It's easy to import Boolean data into @command{awk}, but then the fact
-that it was originally Boolean is lost. Exporting data is even harder;
-there's no way to indicate that a value is really Boolean.
-
-To solve this problem, @command{gawk} provides a function named
@code{mkbool()}.
-It takes one argument, which is any @command{awk} expression, and it
-returns a value of Boolean type.
-
-The returned values are normal @command{awk} numeric values, with
-values of either one or zero,
-depending upon the truth
-value of the original expression passed in the call to @code{mkbool()}.
-
-The @code{typeof()} function (@pxref{Type Functions}) returns
-@code{"number|bool"} for these values.
-
-Thus Boolean-typed values @emph{are} numbers as far as @command{gawk}
-is concerned, except that extension code can treat them as Booleans
-if desired.
-
-While it would have been possible to add two new built-in variables
-of Boolean type named @code{TRUE} and @code{FALSE}, doing so would
-undoubtedly have broken many existing @command{awk} programs. Instead,
-having a ``generator'' function that creates Boolean values gives
-flexibility, without breaking as much existing code.
-
-@node Array Sorting
-@section Controlling Array Traversal and Array Sorting
-
-@command{gawk} lets you control the order in which a
-@samp{for (@var{indx} in @var{array})}
-loop traverses an array.
-
-In addition, two built-in functions, @code{asort()} and @code{asorti()},
-let you sort arrays based on the array values and indices, respectively.
-These two functions also provide control over the sorting criteria used
-to order the elements during sorting.
-
-@menu
-* Controlling Array Traversal:: How to use PROCINFO["sorted_in"].
-* Array Sorting Functions:: How to use @code{asort()} and @code{asorti()}.
-@end menu
-
-@node Controlling Array Traversal
-@subsection Controlling Array Traversal
-
-By default, the order in which a @samp{for (@var{indx} in @var{array})} loop
-scans an array is not defined; it is generally based upon
-the internal implementation of arrays inside @command{awk}.
-
-Often, though, it is desirable to be able to loop over the elements
-in a particular order that you, the programmer, choose. @command{gawk}
-lets you do this.
-
-@ref{Controlling Scanning} describes how you can assign special,
-predefined values to @code{PROCINFO["sorted_in"]} in order to
-control the order in which @command{gawk} traverses an array
-during a @code{for} loop.
-
-In addition, the value of @code{PROCINFO["sorted_in"]} can be a
-function name.@footnote{This is why the predefined sorting orders
-start with an @samp{@@} character, which cannot be part of an identifier.}
-This lets you traverse an array based on any custom criterion.
-The array elements are ordered according to the return value of this
-function. The comparison function should be defined with at least
-four arguments:
-
-@example
-function comp_func(i1, v1, i2, v2)
-@{
- @var{compare elements 1 and 2 in some fashion}
- @var{return < 0; 0; or > 0}
-@}
-@end example
-
-Here, @code{i1} and @code{i2} are the indices, and @code{v1} and @code{v2}
-are the corresponding values of the two elements being compared.
-Either @code{v1} or @code{v2}, or both, can be arrays if the array being
-traversed contains subarrays as values.
-(@xref{Arrays of Arrays} for more information about subarrays.)
-The three possible return values are interpreted as follows:
-
-@table @code
-@item comp_func(i1, v1, i2, v2) < 0
-Index @code{i1} comes before index @code{i2} during loop traversal.
-
-@item comp_func(i1, v1, i2, v2) == 0
-Indices @code{i1} and @code{i2}
-come together, but the relative order with respect to each other is undefined.
-
-@item comp_func(i1, v1, i2, v2) > 0
-Index @code{i1} comes after index @code{i2} during loop traversal.
-@end table
-
-Our first comparison function can be used to scan an array in
-numerical order of the indices:
-
-@example
-@group
-function cmp_num_idx(i1, v1, i2, v2)
-@{
- # numerical index comparison, ascending order
- return (i1 - i2)
-@}
-@end group
-@end example
-
-Our second function traverses an array based on the string order of
-the element values rather than by indices:
-
-@example
-function cmp_str_val(i1, v1, i2, v2)
-@{
- # string value comparison, ascending order
- v1 = v1 ""
- v2 = v2 ""
- if (v1 < v2)
- return -1
- return (v1 != v2)
-@}
-@end example
-
-The third
-comparison function makes all numbers, and numeric strings without
-any leading or trailing spaces, come out first during loop traversal:
-
-@example
-function cmp_num_str_val(i1, v1, i2, v2, n1, n2)
-@{
- # numbers before string value comparison, ascending order
- n1 = v1 + 0
- n2 = v2 + 0
- if (n1 == v1)
- return (n2 == v2) ? (n1 - n2) : -1
- else if (n2 == v2)
- return 1
- return (v1 < v2) ? -1 : (v1 != v2)
-@}
-@end example
-
-Here is a main program to demonstrate how @command{gawk}
-behaves using each of the previous functions:
-
-@example
-BEGIN @{
- data["one"] = 10
- data["two"] = 20
- data[10] = "one"
- data[100] = 100
- data[20] = "two"
-
- f[1] = "cmp_num_idx"
- f[2] = "cmp_str_val"
- f[3] = "cmp_num_str_val"
- for (i = 1; i <= 3; i++) @{
- printf("Sort function: %s\n", f[i])
- PROCINFO["sorted_in"] = f[i]
- for (j in data)
- printf("\tdata[%s] = %s\n", j, data[j])
- print ""
- @}
-@}
-@end example
-
-Here are the results when the program is run:
-
-@example
-$ @kbd{gawk -f compdemo.awk}
-@print{} Sort function: cmp_num_idx @ii{Sort by numeric index}
-@print{} data[two] = 20
-@print{} data[one] = 10 @ii{Both strings are numerically zero}
-@print{} data[10] = one
-@print{} data[20] = two
-@print{} data[100] = 100
-@print{}
-@print{} Sort function: cmp_str_val @ii{Sort by element values as strings}
-@print{} data[one] = 10
-@print{} data[100] = 100 @ii{String 100 is less than string 20}
-@print{} data[two] = 20
-@print{} data[10] = one
-@print{} data[20] = two
-@print{}
-@print{} Sort function: cmp_num_str_val @ii{Sort all numeric values before
all strings}
-@print{} data[one] = 10
-@print{} data[two] = 20
-@print{} data[100] = 100
-@print{} data[10] = one
-@print{} data[20] = two
-@end example
-
-Consider sorting the entries of a GNU/Linux system password file
-according to login name. The following program sorts records
-by a specific field position and can be used for this purpose:
-
-@example
-# passwd-sort.awk --- simple program to sort by field position
-# field position is specified by the global variable POS
-
-function cmp_field(i1, v1, i2, v2)
-@{
- # comparison by value, as string, and ascending order
- return v1[POS] < v2[POS] ? -1 : (v1[POS] != v2[POS])
-@}
-
-@{
- for (i = 1; i <= NF; i++)
- a[NR][i] = $i
-@}
-
-@group
-END @{
- PROCINFO["sorted_in"] = "cmp_field"
-@end group
- if (POS < 1 || POS > NF)
- POS = 1
-
- for (i in a) @{
- for (j = 1; j <= NF; j++)
- printf("%s%c", a[i][j], j < NF ? ":" : "")
- print ""
- @}
-@}
-@end example
-
-The first field in each entry of the password file is the user's login name,
-and the fields are separated by colons.
-Each record defines a subarray,
-with each field as an element in the subarray.
-Running the program produces the
-following output:
-
-@example
-$ @kbd{gawk -v POS=1 -F: -f sort.awk /etc/passwd}
-@print{} adm:x:3:4:adm:/var/adm:/sbin/nologin
-@print{} apache:x:48:48:Apache:/var/www:/sbin/nologin
-@print{} avahi:x:70:70:Avahi daemon:/:/sbin/nologin
-@dots{}
-@end example
-
-The comparison should normally always return the same value when given a
-specific pair of array elements as its arguments. If inconsistent
-results are returned, then the order is undefined. This behavior can be
-exploited to introduce random order into otherwise seemingly
-ordered data:
-
-@example
-function cmp_randomize(i1, v1, i2, v2)
-@{
- # random order (caution: this may never terminate!)
- return (2 - 4 * rand())
-@}
-@end example
-
-As already mentioned, the order of the indices is arbitrary if two
-elements compare equal. This is usually not a problem, but letting
-the tied elements come out in arbitrary order can be an issue, especially
-when comparing item values. The partial ordering of the equal elements
-may change the next time the array is traversed, if other elements are added
to or
-removed from the array. One way to resolve ties when comparing elements
-with otherwise equal values is to include the indices in the comparison
-rules. Note that doing this may make the loop traversal less efficient,
-so consider it only if necessary. The following comparison functions
-force a deterministic order, and are based on the fact that the
-(string) indices of two elements are never equal:
-
-@example
-function cmp_numeric(i1, v1, i2, v2)
-@{
- # numerical value (and index) comparison, descending order
- return (v1 != v2) ? (v2 - v1) : (i2 - i1)
-@}
-
-@group
-function cmp_string(i1, v1, i2, v2)
-@{
- # string value (and index) comparison, descending order
- v1 = v1 i1
- v2 = v2 i2
- return (v1 > v2) ? -1 : (v1 != v2)
-@}
-@end group
-@end example
-
-@c Avoid using the term ``stable'' when describing the unpredictable behavior
-@c if two items compare equal. Usually, the goal of a "stable algorithm"
-@c is to maintain the original order of the items, which is a meaningless
-@c concept for a list constructed from a hash.
-
-A custom comparison function can often simplify ordered loop
-traversal, and the sky is really the limit when it comes to
-designing such a function.
-
-When string comparisons are made during a sort, either for element
-values where one or both aren't numbers, or for element indices
-handled as strings, the value of @code{IGNORECASE}
-(@pxref{Built-in Variables}) controls whether
-the comparisons treat corresponding upper- and lowercase letters as
-equivalent or distinct.
-
-Another point to keep in mind is that in the case of subarrays,
-the element values can themselves be arrays; a production comparison
-function should use the @code{isarray()} function
-(@pxref{Type Functions})
-to check for this, and choose a defined sorting order for subarrays.
-
-@cindex POSIX mode
-All sorting based on @code{PROCINFO["sorted_in"]}
-is disabled in POSIX mode,
-because the @code{PROCINFO} array is not special in that case.
-
-As a side note, sorting the array indices before traversing
-the array has been reported to add a 15% to 20% overhead to the
-execution time of @command{awk} programs. For this reason,
-sorted array traversal is not the default.
-
-@c The @command{gawk}
-@c maintainers believe that only the people who wish to use a
-@c feature should have to pay for it.
-
-@node Array Sorting Functions
-@subsection Sorting Array Values and Indices with @command{gawk}
-
-@cindex arrays @subentry sorting @subentry @code{asort()} function
(@command{gawk})
-@cindex arrays @subentry sorting @subentry @code{asorti()} function
(@command{gawk})
-@cindexgawkfunc{asort}
-@cindex @code{asort()} function (@command{gawk}) @subentry arrays, sorting
-@cindex @code{asort()} function (@command{gawk}) @subentry side effects
-@cindexgawkfunc{asorti}
-@cindex @code{asorti()} function (@command{gawk}) @subentry arrays, sorting
-@cindex @code{asorti()} function (@command{gawk}) @subentry side effects
-@cindex sort function, arrays, sorting
-In most @command{awk} implementations, sorting an array requires writing
-a @code{sort()} function. This can be educational for exploring
-different sorting algorithms, but usually that's not the point of the program.
-@command{gawk} provides the built-in @code{asort()} and @code{asorti()}
-functions (@pxref{String Functions}) for sorting arrays. For example:
-
-@example
-@var{populate the array} data
-n = asort(data)
-for (i = 1; i <= n; i++)
- @var{do something with} data[i]
-@end example
-
-After the call to @code{asort()}, the array @code{data} is indexed from 1
-to some number @var{n}, the total number of elements in @code{data}.
-(This count is @code{asort()}'s return value.)
-@code{data[1]} @value{LEQ} @code{data[2]} @value{LEQ} @code{data[3]}, and so
on.
-The default comparison is based on the type of the elements
-(@pxref{Typing and Comparison}).
-All numeric values come before all string values,
-which in turn come before all subarrays.
-
-@cindex side effects @subentry @code{asort()} function
-@cindex side effects @subentry @code{asorti()} function
-An important side effect of calling @code{asort()} is that
-@emph{the array's original indices are irrevocably lost}.
-As this isn't always desirable, @code{asort()} accepts a
-second argument:
-
-@example
-@var{populate the array} source
-n = asort(source, dest)
-for (i = 1; i <= n; i++)
- @var{do something with} dest[i]
-@end example
-
-In this case, @command{gawk} copies the @code{source} array into the
-@code{dest} array and then sorts @code{dest}, destroying its indices.
-However, the @code{source} array is not affected.
-
-Often, what's needed is to sort on the values of the @emph{indices}
-instead of the values of the elements. To do that, use the
-@code{asorti()} function. The interface and behavior are identical to
-that of @code{asort()}, except that the index values are used for sorting
-and become the values of the result array:
-
-@example
-@{ source[$0] = some_func($0) @}
-
-END @{
- n = asorti(source, dest)
- for (i = 1; i <= n; i++) @{
- @ii{Work with sorted indices directly:}
- @var{do something with} dest[i]
- @dots{}
- @ii{Access original array via sorted indices:}
- @var{do something with} source[dest[i]]
- @}
-@}
-@end example
-
-So far, so good. Now it starts to get interesting. Both @code{asort()}
-and @code{asorti()} accept a third string argument to control comparison
-of array elements. When we introduced @code{asort()} and @code{asorti()}
-in @ref{String Functions}, we ignored this third argument; however,
-now is the time to describe how this argument affects these two functions.
-
-Basically, the third argument specifies how the array is to be sorted.
-There are two possibilities. As with @code{PROCINFO["sorted_in"]},
-this argument may be one of the predefined names that @command{gawk}
-provides (@pxref{Controlling Scanning}), or it may be the name of a
-user-defined function (@pxref{Controlling Array Traversal}).
-
-In the latter case, @emph{the function can compare elements in any way
-it chooses}, taking into account just the indices, just the values,
-or both. This is extremely powerful.
-
-Once the array is sorted, @code{asort()} takes the @emph{values} in
-their final order and uses them to fill in the result array, whereas
-@code{asorti()} takes the @emph{indices} in their final order and uses
-them to fill in the result array.
-
-@cindex reference counting, sorting arrays
-@quotation NOTE
-Copying array indices and elements isn't expensive in terms of memory.
-Internally, @command{gawk} maintains @dfn{reference counts} to data.
-For example, when @code{asort()} copies the first array to the second one,
-there is only one copy of the original array elements' data, even though
-both arrays use the values.
-@end quotation
-
-You may use the same array for both the first and second arguments to
-@code{asort()} and @code{asorti()}. Doing so only makes sense if you
-are also supplying the third argument, since @command{awk} doesn't
-provide a way to pass that third argument without also passing the first
-and second ones.
-
-@c Document It And Call It A Feature. Sigh.
-@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
-@cindex arrays @subentry sorting @subentry @code{IGNORECASE} variable and
-@cindex @code{IGNORECASE} variable @subentry array sorting functions and
-Because @code{IGNORECASE} affects string comparisons, the value
-of @code{IGNORECASE} also affects sorting for both @code{asort()} and
@code{asorti()}.
-Note also that the locale's sorting order does @emph{not}
-come into play; comparisons are based on character values only.@footnote{This
-is true because locale-based comparison occurs only when in
-POSIX-compatibility mode, and because @code{asort()} and @code{asorti()} are
-@command{gawk} extensions, they are not available in that case.}
-
-The following example demonstrates the use of a comparison function with
-@code{asort()}. The comparison function, @code{case_fold_compare()}, maps
-both values to lowercase in order to compare them ignoring case.
-
-@example
-@group
-# case_fold_compare --- compare as strings, ignoring case
-
-function case_fold_compare(i1, v1, i2, v2, l, r)
-@{
- l = tolower(v1)
-@end group
- r = tolower(v2)
-
- if (l < r)
- return -1
- else if (l == r)
- return 0
- else
- return 1
-@}
-@end example
-
-And here is the test program for it:
-
-@example
-# Test program
-
-BEGIN @{
- Letters = "abcdefghijklmnopqrstuvwxyz" \
- "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
- split(Letters, data, "")
-
- asort(data, result, "case_fold_compare")
-
- j = length(result)
- for (i = 1; i <= j; i++) @{
- printf("%s", result[i])
- if (i % (j/2) == 0)
- printf("\n")
- else
- printf(" ")
- @}
-@}
-@end example
-
-When run, we get the following:
-
-@example
-$ @kbd{gawk -f case_fold_compare.awk}
-@print{} A a B b c C D d e E F f g G H h i I J j k K l L M m
-@print{} n N O o p P Q q r R S s t T u U V v w W X x y Y z Z
-@end example
-
-@quotation NOTE
-``Under the hood,'' @command{gawk} uses the C library @code{qsort()}
-function to manage the sorting. @code{qsort()} can call itself
-recursively. This means that when you write a comparison function,
-you should be careful to avoid the use of global variables and arrays;
-use only local variables and arrays that you declare as additional
-parameters to the comparison function. Otherwise, you are likely to
-cause unintentional memory corruption in your global arrays and possibly
-cause @command{gawk} itself to fail.
-@end quotation
-
-@node Two-way I/O
-@section Two-Way Communications with Another Process
-
-@c 8/2014. Neither Mike nor BWK saw this as relevant. Commenting it out.
-@ignore
-@cindex Brennan, Michael
-@cindex programmers, attractiveness of
-@smallexample
-@c Path:
cssun.mathcs.emory.edu!gatech!newsxfer3.itd.umich.edu!news-peer.sprintlink.net!news-sea-19.sprintlink.net!news-in-west.sprintlink.net!news.sprintlink.net!Sprint!204.94.52.5!news.whidbey.com!brennan
-From: brennan@@whidbey.com (Mike Brennan)
-Newsgroups: comp.lang.awk
-Subject: Re: Learn the SECRET to Attract Women Easily
-Date: 4 Aug 1997 17:34:46 GMT
-@c Organization: WhidbeyNet
-@c Lines: 12
-Message-ID: <5s53rm$eca@@news.whidbey.com>
-@c References: <5s20dn$2e1@chronicle.concentric.net>
-@c Reply-To: brennan@whidbey.com
-@c NNTP-Posting-Host: asn202.whidbey.com
-@c X-Newsreader: slrn (0.9.4.1 UNIX)
-@c Xref: cssun.mathcs.emory.edu comp.lang.awk:5403
-
-On 3 Aug 1997 13:17:43 GMT, Want More Dates???
-<tracy78@@kilgrona.com> wrote:
->Learn the SECRET to Attract Women Easily
->
->The SCENT(tm) Pheromone Sex Attractant For Men to Attract Women
-
-The scent of awk programmers is a lot more attractive to women than
-the scent of perl programmers.
---
-Mike Brennan
-@c brennan@@whidbey.com
-@end smallexample
-@end ignore
-
-@cindex advanced features @subentry processes, communicating with
-@cindex processes, two-way communications with
-It is often useful to be able to
-send data to a separate program for
-processing and then read the result. This can always be
-done with temporary files:
-
-@example
-# Write the data for processing
-tempfile = ("mydata." PROCINFO["pid"])
-while (@var{not done with data})
- print @var{data} | ("subprogram > " tempfile)
-close("subprogram > " tempfile)
-
-# Read the results, remove tempfile when done
-while ((getline newdata < tempfile) > 0)
- @var{process} newdata @var{appropriately}
-close(tempfile)
-system("rm " tempfile)
-@end example
-
-@noindent
-This works, but not elegantly. Among other things, it requires that
-the program be run in a directory that cannot be shared among users;
-for example, @file{/tmp} will not do, as another user might happen
-to be using a temporary file with the same name.@footnote{Michael
-Brennan suggests the use of @command{rand()} to generate unique
-@value{FN}s. This is a valid point; nevertheless, temporary files
-remain more difficult to use than two-way pipes.} @c 8/2014
-
-@cindex coprocesses
-@cindex input/output @subentry two-way
-@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
-@cindex vertical bar (@code{|}) @subentry @code{|&} operator (I/O)
-@cindex @command{csh} utility @subentry @code{|&} operator, comparison with
-However, with @command{gawk}, it is possible to
-open a @emph{two-way} pipe to another process. The second process is
-termed a @dfn{coprocess}, as it runs in parallel with @command{gawk}.
-The two-way connection is created using the @samp{|&} operator
-(borrowed from the Korn shell, @command{ksh}):@footnote{This is very
-different from the same operator in the C shell and in Bash.}
-
-@example
-do @{
- print @var{data} |& "subprogram"
- "subprogram" |& getline results
-@} while (@var{data left to process})
-close("subprogram")
-@end example
-
-The first time an I/O operation is executed using the @samp{|&}
-operator, @command{gawk} creates a two-way pipeline to a child process
-that runs the other program. Output created with @code{print}
-or @code{printf} is written to the program's standard input, and
-output from the program's standard output can be read by the @command{gawk}
-program using @code{getline}.
-As is the case with processes started by @samp{|}, the subprogram
-can be any program, or pipeline of programs, that can be started by
-the shell.
-
-There are some cautionary items to be aware of:
-
-@itemize @value{BULLET}
-@item
-As the code inside @command{gawk} currently stands, the coprocess's
-standard error goes to the same place that the parent @command{gawk}'s
-standard error goes. It is not possible to read the child's
-standard error separately.
-
-@cindex deadlocks
-@cindex buffering @subentry input/output
-@cindex @code{getline} command @subentry deadlock and
-@item
-I/O buffering may be a problem. @command{gawk} automatically
-flushes all output down the pipe to the coprocess.
-However, if the coprocess does not flush its output,
-@command{gawk} may hang when doing a @code{getline} in order to read
-the coprocess's results. This could lead to a situation
-known as @dfn{deadlock}, where each process is waiting for the
-other one to do something.
-@end itemize
-
-@cindex @code{close()} function @subentry two-way pipes and
-It is possible to close just one end of the two-way pipe to
-a coprocess, by supplying a second argument to the @code{close()}
-function of either @code{"to"} or @code{"from"}
-(@pxref{Close Files And Pipes}).
-These strings tell @command{gawk} to close the end of the pipe
-that sends data to the coprocess or the end that reads from it,
-respectively.
-
-@cindex @command{sort} utility @subentry coprocesses and
-This is particularly necessary in order to use
-the system @command{sort} utility as part of a coprocess;
-@command{sort} must read @emph{all} of its input
-data before it can produce any output.
-The @command{sort} program does not receive an end-of-file indication
-until @command{gawk} closes the write end of the pipe.
-
-When you have finished writing data to the @command{sort}
-utility, you can close the @code{"to"} end of the pipe, and
-then start reading sorted data via @code{getline}.
-For example:
-
-@example
-BEGIN @{
- command = "LC_ALL=C sort"
- n = split("abcdefghijklmnopqrstuvwxyz", a, "")
-
- for (i = n; i > 0; i--)
- print a[i] |& command
- close(command, "to")
-
- while ((command |& getline line) > 0)
- print "got", line
- close(command)
-@}
-@end example
-
-This program writes the letters of the alphabet in reverse order, one
-per line, down the two-way pipe to @command{sort}. It then closes the
-write end of the pipe, so that @command{sort} receives an end-of-file
-indication. This causes @command{sort} to sort the data and write the
-sorted data back to the @command{gawk} program. Once all of the data
-has been read, @command{gawk} terminates the coprocess and exits.
-
-@cindex ASCII
-As a side note, the assignment @samp{LC_ALL=C} in the @command{sort}
-command ensures traditional Unix (ASCII) sorting from @command{sort}.
-This is not strictly necessary here, but it's good to know how to do this.
-
-Be careful when closing the @code{"from"} end of a two-way pipe; in this
-case @command{gawk} waits for the child process to exit, which may cause
-your program to hang. (Thus, this particular feature is of much less
-use in practice than being able to close the @code{"to"} end.)
-
-@quotation CAUTION
-Normally,
-it is a fatal error to write to the @code{"to"} end of a two-way
-pipe which has been closed, and it is also a fatal error to read
-from the @code{"from"} end of a two-way pipe that has been closed.
-
-You may set @code{PROCINFO["@var{command}", "NONFATAL"]} to
-make such operations become nonfatal. If you do so, you then need
-to check @code{ERRNO} after each @code{print}, @code{printf},
-or @code{getline}.
-@xref{Nonfatal}, for more information.
-@end quotation
-
-@cindex @command{gawk} @subentry @code{PROCINFO} array in
-@cindex @code{PROCINFO} array @subentry communications via ptys and
-You may also use pseudo-ttys (ptys) for
-two-way communication instead of pipes, if your system supports them.
-This is done on a per-command basis, by setting a special element
-in the @code{PROCINFO} array
-(@pxref{Auto-set}),
-like so:
-
-@example
-command = "sort -nr" # command, save in convenience variable
-PROCINFO[command, "pty"] = 1 # update PROCINFO
-print @dots{} |& command # start two-way pipe
-@dots{}
-@end example
-
-@noindent
-If your system does not have ptys, or if all the system's ptys are in use,
-@command{gawk} automatically falls back to using regular pipes.
-
-Using ptys usually avoids the buffer deadlock issues described earlier,
-at some loss in performance. This is because the tty driver buffers
-and sends data line-by-line. On systems with the @command{stdbuf}
-(part of the @uref{https://www.gnu.org/software/coreutils/coreutils.html,
-GNU Coreutils package}), you can use that program instead of ptys.
-
-Note also that ptys are not fully transparent. Certain binary control
-codes, such @kbd{Ctrl-d} for end-of-file, are interpreted by the tty
-driver and not passed through.
-
-@quotation CAUTION
-Finally, coprocesses open up the possibility of @dfn{deadlock} between
-@command{gawk} and the program running in the coprocess. This can occur
-if you send ``too much'' data to the coprocess before reading any back;
-each process is blocked writing data with no one available to read what
-they've already written. There is no workaround for deadlock; careful
-programming and knowledge of the behavior of the coprocess are required.
-@end quotation
-
-@c From email send January 4, 2018.
-The following example, due to Andrew Schorr, demonstrates how
-using ptys can help deal with buffering deadlocks.
-
-Suppose @command{gawk} were unable to add numbers.
-You could use a coprocess to do it. Here's an exceedingly
-simple program written for that purpose:
-
-@example
-$ @kbd{cat add.c}
-#include <stdio.h>
-
-int
-main(void)
-@{
- int x, y;
- while (scanf("%d %d", & x, & y) == 2)
- printf("%d\n", x + y);
- return 0;
-@}
-$ @kbd{cc -O add.c -o add} @ii{Compile the program}
-@end example
-
-You could then write an exceedingly simple @command{gawk} program
-to add numbers by passing them to the coprocess:
-
-@example
-$ @kbd{echo 1 2 |}
-> @kbd{gawk -v cmd=./add '@{ print |& cmd; cmd |& getline x; print x @}'}
-@end example
-
-And it would deadlock, because @file{add.c} fails to call
-@samp{setlinebuf(stdout)}. The @command{add} program freezes.
-
-Now try instead:
-
-@example
-$ @kbd{echo 1 2 |}
-> @kbd{gawk -v cmd=add 'BEGIN @{ PROCINFO[cmd, "pty"] = 1 @}}
-> @kbd{ @{ print |& cmd; cmd |& getline x; print x @}'}
-@print{} 3
-@end example
-
-By using a pty, @command{gawk} fools the standard I/O library into
-thinking it has an interactive session, so it defaults to line buffering.
-And now, magically, it works!
-
-@node TCP/IP Networking
-@section Using @command{gawk} for Network Programming
-@cindex advanced features @subentry network programming
-@cindex networks @subentry programming
-@cindex TCP/IP
-@cindex @code{/inet/@dots{}} special files (@command{gawk})
-@cindex files @subentry @code{/inet/@dots{}} (@command{gawk})
-@cindex @code{/inet4/@dots{}} special files (@command{gawk})
-@cindex files @subentry @code{/inet4/@dots{}} (@command{gawk})
-@cindex @code{/inet6/@dots{}} special files (@command{gawk})
-@cindex files @subentry @code{/inet6/@dots{}} (@command{gawk})
-@cindex @code{EMRED}
-@ifnotdocbook
-@quotation
-@code{EMRED}:@*
-@ @ @ @ @i{A host is a host from coast to coast,@*
-@ @ @ @ and nobody talks to a host that's close,@*
-@ @ @ @ unless the host that isn't close@*
-@ @ @ @ is busy, hung, or dead.}
-@author Mike O'Brien (aka Mr.@: Protocol)
-@end quotation
-@end ifnotdocbook
-
-@docbook
-<blockquote>
-<attribution>Mike O'Brien (aka Mr. Protocol)</attribution>
-<literallayout class="normal"><literal>EMRED</literal>:
- <emphasis>A host is a host from coast to
coast,</emphasis>
- <emphasis>and no-one can talk to host that's
close,</emphasis>
- <emphasis>unless the host that isn't close</emphasis>
- <emphasis>is busy, hung, or
dead.</emphasis></literallayout>
-</blockquote>
-@end docbook
-
-In addition to being able to open a two-way pipeline to a coprocess
-on the same system
-(@pxref{Two-way I/O}),
-it is possible to make a two-way connection to
-another process on another system across an IP network connection.
-
-You can think of this as just a @emph{very long} two-way pipeline to
-a coprocess.
-The way @command{gawk} decides that you want to use TCP/IP networking is
-by recognizing special @value{FN}s that begin with one of @samp{/inet/},
-@samp{/inet4/}, or @samp{/inet6/}.
-
-The full syntax of the special @value{FN} is
-@file{/@var{net-type}/@var{protocol}/@var{local-port}/@var{remote-host}/@var{remote-port}}.
-The components are:
-
-@table @var
-@item net-type
-Specifies the kind of Internet connection to make.
-Use @samp{/inet4/} to force IPv4, and
-@samp{/inet6/} to force IPv6.
-Plain @samp{/inet/} (which used to be the only option) uses
-the system default, most likely IPv4.
-
-@item protocol
-The protocol to use over IP. This must be either @samp{tcp}, or
-@samp{udp}, for a TCP or UDP IP connection,
-respectively. TCP should be used for most applications.
-
-@item local-port
-@cindex @code{getaddrinfo()} function (C library)
-@cindex C library functions @subentry @code{getaddrinfo()}
-The local TCP or UDP port number to use. Use a port number of @samp{0}
-when you want the system to pick a port. This is what you should do
-when writing a TCP or UDP client.
-You may also use a well-known service name, such as @samp{smtp}
-or @samp{http}, in which case @command{gawk} attempts to determine
-the predefined port number using the C @code{getaddrinfo()} function.
-
-@item remote-host
-The IP address or fully qualified domain name of the Internet
-host to which you want to connect.
-
-@item remote-port
-The TCP or UDP port number to use on the given @var{remote-host}.
-Again, use @samp{0} if you don't care, or else a well-known
-service name.
-@end table
-
-@cindex @command{gawk} @subentry @code{ERRNO} variable in
-@cindex @code{ERRNO} variable
-@quotation NOTE
-Failure in opening a two-way socket will result in a nonfatal error
-being returned to the calling code. The value of @code{ERRNO} indicates
-the error (@pxref{Auto-set}).
-@end quotation
-
-Consider the following very simple example:
-
-@example
-BEGIN @{
- Service = "/inet/tcp/0/localhost/daytime"
- Service |& getline
- print $0
- close(Service)
-@}
-@end example
-
-This program reads the current date and time from the local system's
-TCP @code{daytime} server.
-It then prints the results and closes the connection.
-
-Because this topic is extensive, the use of @command{gawk} for
-TCP/IP programming is documented separately.
-@ifinfo
-@xref{Top, , General Introduction, gawkinet, @value{GAWKINETTITLE}},
-@end ifinfo
-@ifnotinfo
-See
-@uref{https://www.gnu.org/software/gawk/manual/gawkinet/,
-@cite{@value{GAWKINETTITLE}}},
-which comes as part of the @command{gawk} distribution,
-@end ifnotinfo
-for a much more complete introduction and discussion, as well as
-extensive examples.
-
-@quotation NOTE
-@command{gawk} can only open direct sockets. There is currently
-no way to access services available over Secure Socket Layer
-(SSL); this includes any web service whose URL starts with @samp{https://}.
-@end quotation
-
-
-@node Profiling
-@section Profiling Your @command{awk} Programs
-@cindex @command{awk} programs @subentry profiling
-@cindex profiling @command{awk} programs
-@cindex @code{awkprof.out} file
-@cindex files @subentry @code{awkprof.out}
-
-You may produce execution traces of your @command{awk} programs.
-This is done by passing the option @option{--profile} to @command{gawk}.
-When @command{gawk} has finished running, it creates a profile of your program
in a file
-named @file{awkprof.out}. Because it is profiling, it also executes up to 45%
slower than
-@command{gawk} normally does.
-
-@cindex @option{--profile} option
-As shown in the following example,
-the @option{--profile} option can be used to change the name of the file
-where @command{gawk} will write the profile:
-
-@example
-gawk --profile=myprog.prof -f myprog.awk data1 data2
-@end example
-
-@noindent
-In the preceding example, @command{gawk} places the profile in
-@file{myprog.prof} instead of in @file{awkprof.out}.
-
-Here is a sample session showing a simple @command{awk} program,
-its input data, and the results from running @command{gawk} with the
-@option{--profile} option. First, the @command{awk} program:
-
-@example
-BEGIN @{ print "First BEGIN rule" @}
-
-END @{ print "First END rule" @}
-
-/foo/ @{
- print "matched /foo/, gosh"
- for (i = 1; i <= 3; i++)
- sing()
-@}
-
-@{
- if (/foo/)
- print "if is true"
- else
- print "else is true"
-@}
-
-BEGIN @{ print "Second BEGIN rule" @}
-
-END @{ print "Second END rule" @}
-
-function sing( dummy)
-@{
- print "I gotta be me!"
-@}
-@end example
-
-Following is the input data:
-
-@example
-foo
-bar
-baz
-foo
-junk
-@end example
-
-Here is the @file{awkprof.out} that results from running the
-@command{gawk} profiler on this program and data (this example also
-illustrates that @command{awk} programmers sometimes get up very early
-in the morning to work):
-
-@cindex @code{BEGIN} pattern @subentry profiling and
-@cindex @code{END} pattern @subentry profiling and
-@example
- # gawk profile, created Mon Sep 29 05:16:21 2014
-
- # BEGIN rule(s)
-
- BEGIN @{
- 1 print "First BEGIN rule"
- @}
-
- BEGIN @{
- 1 print "Second BEGIN rule"
- @}
-
- # Rule(s)
-
- 5 /foo/ @{ # 2
- 2 print "matched /foo/, gosh"
- 6 for (i = 1; i <= 3; i++) @{
- 6 sing()
- @}
- @}
-
- 5 @{
- 5 if (/foo/) @{ # 2
- 2 print "if is true"
- 3 @} else @{
- 3 print "else is true"
- @}
- @}
-
- # END rule(s)
-
- END @{
- 1 print "First END rule"
- @}
-
- END @{
- 1 print "Second END rule"
- @}
-
-
- # Functions, listed alphabetically
-
- 6 function sing(dummy)
- @{
- 6 print "I gotta be me!"
- @}
-@end example
-
-This example illustrates many of the basic features of profiling output.
-They are as follows:
-
-@itemize @value{BULLET}
-@item
-The program is printed in the order @code{BEGIN} rules,
-@code{BEGINFILE} rules,
-pattern--action rules,
-@code{ENDFILE} rules, @code{END} rules, and functions, listed
-alphabetically.
-Multiple @code{BEGIN} and @code{END} rules retain their
-separate identities, as do
-multiple @code{BEGINFILE} and @code{ENDFILE} rules.
-
-@cindex patterns @subentry counts, in a profile
-@item
-Pattern--action rules have two counts.
-The first count, to the left of the rule, shows how many times
-the rule's pattern was @emph{tested}.
-The second count, to the right of the rule's opening left brace
-in a comment,
-shows how many times the rule's action was @emph{executed}.
-The difference between the two indicates how many times the rule's
-pattern evaluated to false.
-
-@item
-Similarly,
-the count for an @code{if}-@code{else} statement shows how many times
-the condition was tested.
-To the right of the opening left brace for the @code{if}'s body
-is a count showing how many times the condition was true.
-The count for the @code{else}
-indicates how many times the test failed.
-
-@cindex loops @subentry count for header, in a profile
-@item
-The count for a loop header (such as @code{for}
-or @code{while}) shows how many times the loop test was executed.
-(Because of this, you can't just look at the count on the first
-statement in a rule to determine how many times the rule was executed.
-If the first statement is a loop, the count is misleading.)
-
-@cindex functions @subentry user-defined @subentry counts, in a profile
-@cindex user-defined @subentry functions @subentry counts, in a profile
-@item
-For user-defined functions, the count next to the @code{function}
-keyword indicates how many times the function was called.
-The counts next to the statements in the body show how many times
-those statements were executed.
-
-@cindex @code{@{@}} (braces)
-@cindex braces (@code{@{@}})
-@item
-The layout uses ``K&R'' style with TABs.
-Braces are used everywhere, even when
-the body of an @code{if}, @code{else}, or loop is only a single statement.
-
-@cindex @code{()} (parentheses) @subentry in a profile
-@cindex parentheses @code{()} @subentry in a profile
-@item
-Parentheses are used only where needed, as indicated by the structure
-of the program and the precedence rules.
-For example, @samp{(3 + 5) * 4} means add three and five, then multiply
-the total by four. However, @samp{3 + 5 * 4} has no parentheses, and
-means @samp{3 + (5 * 4)}.
-However, explicit parentheses in the source program are retained.
-
-@ignore
-@item
-All string concatenations are parenthesized too.
-(This could be made a bit smarter.)
-@end ignore
-
-@item
-Parentheses are used around the arguments to @code{print}
-and @code{printf} only when
-the @code{print} or @code{printf} statement is followed by a redirection.
-Similarly, if
-the target of a redirection isn't a scalar, it gets parenthesized.
-
-@item
-@command{gawk} supplies leading comments in
-front of the @code{BEGIN} and @code{END} rules,
-the @code{BEGINFILE} and @code{ENDFILE} rules,
-the pattern--action rules, and the functions.
-
-@item
-Functions are listed alphabetically. All functions in the @code{awk}
-namespace are listed first, in alphabetical order. Then come the
-functions in namespaces. The namespaces are listed in alphabetical order,
-and the functions within each namespace are listed alphabetically.
-
-@end itemize
-
-The profiled version of your program may not look exactly like what you
-typed when you wrote it. This is because @command{gawk} creates the
-profiled version by ``pretty-printing'' its internal representation of
-the program. The advantage to this is that @command{gawk} can produce
-a standard representation.
-Also, things such as:
-
-@example
-/foo/
-@end example
-
-@noindent
-come out as:
-
-@example
-/foo/ @{
- print
-@}
-@end example
-
-@noindent
-which is correct, but possibly unexpected.
-(If a program uses both @samp{print $0} and plain
-@samp{print}, that distinction is retained.)
-
-@cindex profiling @command{awk} programs @subentry dynamically
-@cindex @command{gawk} @subentry dynamic profiling
-@cindex @command{gawk} @subentry profiling programs
-@cindex dynamic profiling
-Besides creating profiles when a program has completed,
-@command{gawk} can produce a profile while it is running.
-This is useful if your @command{awk} program goes into an
-infinite loop and you want to see what has been executed.
-To use this feature, run @command{gawk} with the @option{--profile}
-option in the background:
-
-@example
-$ @kbd{gawk --profile -f myprog &}
-[1] 13992
-@end example
-
-@cindex @command{kill} command, dynamic profiling
-@cindex @code{USR1} signal, for dynamic profiling
-@cindex @code{SIGUSR1} signal, for dynamic profiling
-@cindex signals @subentry @code{USR1}/@code{SIGUSR1}, for profiling
-@noindent
-The shell prints a job number and process ID number; in this case, 13992.
-Use the @command{kill} command to send the @code{USR1} signal
-to @command{gawk}:
-
-@example
-$ @kbd{kill -USR1 13992}
-@end example
-
-@noindent
-As usual, the profiled version of the program is written to
-@file{awkprof.out}, or to a different file if one was specified with
-the @option{--profile} option.
-
-Along with the regular profile, as shown earlier, the profile file
-includes a trace of any active functions:
-
-@example
-# Function Call Stack:
-
-# 3. baz
-# 2. bar
-# 1. foo
-# -- main --
-@end example
-
-You may send @command{gawk} the @code{USR1} signal as many times as you like.
-Each time, the profile and function call trace are appended to the output
-profile file.
-
-@cindex @code{HUP} signal, for dynamic profiling
-@cindex @code{SIGHUP} signal, for dynamic profiling
-@cindex signals @subentry @code{HUP}/@code{SIGHUP}, for profiling
-If you use the @code{HUP} signal instead of the @code{USR1} signal,
-@command{gawk} produces the profile and the function call trace and then exits.
-
-@cindex @code{INT} signal (MS-Windows)
-@cindex @code{SIGINT} signal (MS-Windows)
-@cindex signals @subentry @code{INT}/@code{SIGINT} (MS-Windows)
-@cindex @code{QUIT} signal (MS-Windows)
-@cindex @code{SIGQUIT} signal (MS-Windows)
-@cindex signals @subentry @code{QUIT}/@code{SIGQUIT} (MS-Windows)
-When @command{gawk} runs on MS-Windows systems, it uses the
-@code{INT} and @code{QUIT} signals for producing the profile, and in
-the case of the @code{INT} signal, @command{gawk} exits. This is
-because these systems don't support the @command{kill} command, so the
-only signals you can deliver to a program are those generated by the
-keyboard. The @code{INT} signal is generated by the
-@kbd{Ctrl-c} or @kbd{Ctrl-BREAK} key, while the
-@code{QUIT} signal is generated by the @kbd{Ctrl-\} key.
-
-@cindex pretty printing
-Finally, @command{gawk} also accepts another option, @option{--pretty-print}.
-When called this way, @command{gawk} ``pretty-prints'' the program into
-@file{awkprof.out}, without any execution counts.
-
-@quotation NOTE
-Once upon a time, the @option{--pretty-print} option would also run
-your program. This is no longer the case.
-@end quotation
-
-@cindex profiling, pretty printing, difference with
-@cindex pretty printing @subentry profiling, difference with
-There is a significant difference between the output created when
-profiling, and that created when pretty-printing. Pretty-printed output
-preserves the original comments that were in the program, although their
-placement may not correspond exactly to their original locations in the
-source code. However, no comments should be lost.
-Also, @command{gawk} does the best it can to preserve
-the distinction between comments at the end of a statement and comments
-on lines by themselves. This isn't always perfect, though.
-
-However, as a deliberate design decision, profiling output @emph{omits}
-the original program's comments. This allows you to focus on the
-execution count data and helps you avoid the temptation to use the
-profiler for pretty-printing.
-
-Additionally, pretty-printed output does not have the leading indentation
-that the profiling output does. This makes it easy to pretty-print your
-code once development is completed, and then use the result as the final
-version of your program.
-
-Because the internal representation of your program is formatted to
-recreate an @command{awk} program, profiling and pretty-printing
-automatically disable @command{gawk}'s default optimizations.
-
-Profiling and pretty-printing also preserve the original format of numeric
-constants; if you used an octal or hexadecimal value in your source
-code, it will appear that way in the output.
-
-@node Persistent Memory
-@section Preserving Data Between Runs
-
-@cindex persistent memory
-@cindex PMA memory allocator
-Starting with @value{PVERSION} 5.2, @command{gawk} supports
-@dfn{persistent memory}. This experimental feature stores the values of
-all of @command{gawk}'s variables, arrays and user-defined functions
-in a persistent heap, which resides in a file in
-the filesystem. When persistent memory is not in use (the normal case),
-@command{gawk}'s data resides in ephemeral system memory.
-
-Persistent memory is enabled on certain 64-bit systems supporting the
@code{mmap()}
-and @code{munmap()} system calls. @command{gawk} must be compiled as a
-non-PIE (Position Independent Executable) binary, since the persistent
-store ends up holding pointers to functions held within the @command{gawk}
-executable. This also means that to use the persistent memory, you must
-use the same @command{gawk} executable from run to run.
-
-You can see if your version of @command{gawk} supports persistent
-memory like so:
-
-@example
-$ @kbd{gawk --version}
-@print{} GNU Awk 5.2.2, API 3.2, PMA Avon 8-g1, (GNU MPFR 4.1.0, GNU MP 6.2.1)
-@print{} Copyright (C) 1989, 1991-2023 Free Software Foundation.
-@dots{}
-@end example
-
-@noindent
-If you see the @samp{PMA} with a version indicator, then it's supported.
-
-@cindex @env{REALLY_USE_PERSIST_MALLOC} environment variable
-@cindex environment variables @subentry @env{REALLY_USE_PERSIST_MALLOC}
-As of this writing, persistent memory has only been tested on GNU/Linux,
-Cygwin, Solaris 2.11, Intel architecture macOS systems,
-FreeBSD 13.1 and OpenBSD 7.1.
-On all others, persistent memory is disabled by default. You can force
-it to be enabled by exporting the shell variable
-@env{REALLY_USE_PERSIST_MALLOC} with a nonempty value before
-running @command{configure} (@pxref{Quick Installation}).
-If you do so and all the tests pass, please let the maintainer know.
-
-To use persistent memory, follow these steps:
-
-@enumerate 1
-@item
-Create a new, empty sparse file of the desired size. For example, four
-gigabytes. On a GNU/Linux system, you can use the @command{truncate}
-utility:
-
-@example
-$ @kbd{truncate -s 4G data.pma}
-@end example
-
-@item
-It is recommended (but not required) to change the permissions on the
-file so that only the owner can read and write it:
-
-@example
-$ @kbd{chmod 0600 data.pma}
-@end example
-
-@cindex @env{GAWK_PERSIST_FILE} environment variable
-@cindex environment variables @subentry @env{GAWK_PERSIST_FILE}
-@item
-Provide the path to the data file in the @env{GAWK_PERSIST_FILE}
-environment variable. This is best done by placing the value in the
-environment just for the run of @command{gawk}, like so:
-
-@example
-$ @kbd{GAWK_PERSIST_FILE=data.pma gawk 'BEGIN @{ print ++i @}'}
-1
-@end example
-
-@item
-Use the same data file in subsequent runs to use the preserved data values:
-
-@example
-$ @kbd{GAWK_PERSIST_FILE=data.pma gawk 'BEGIN @{ print ++i @}'}
-2
-$ @kbd{GAWK_PERSIST_FILE=data.pma gawk 'BEGIN @{ print ++i @}'}
-3
-@end example
-
-@noindent
-As shown, in subsequent runs using the same data file, the values of
-@command{gawk}'s variables are preserved. However, @command{gawk}'s
-special variables, such as @code{NR}, are reset upon each run.
-Only the variables defined by the program are preserved across runs.
-
-@end enumerate
-
-Interestingly, the program that you execute need not be the same from
-run to run; the persistent store only maintains the values of variables,
-arrays, and user-defined functions, not the totality of @command{gawk}'s
-internal state. This lets you share data between unrelated programs,
-eliminating the need for scripts to communicate via text files.
-
-@cindex Kelly, Terence
-Terence Kelly, the author of the persistent memory allocator
-@command{gawk} uses, provides the following advice about the backing file:
-
-@quotation
-Regarding backing file size, I recommend making it far larger
-than all of the data that will ever reside in it, assuming
-that the file system supports sparse files. The ``pay only
-for what you use'' aspect of sparse files ensures that the
-actual storage resource footprint of the backing file will
-meet the application's needs but will be as small as
-possible. If the file system does @emph{not} support sparse
-files, there's a dilemma: Making the backing file too large
-is wasteful, but making it too small risks memory exhaustion,
-i.e., @code{pma_malloc()} returns @code{NULL}.
-But persistent @command{gawk} should
-still work even without sparse files.
-@ignore
-Note also that if the
-file system is encrypted, sparsity is no longer meaningful,
-even if the file system would otherwise support sparse files.
-At least this is true for some combinations of FS and FS
-encryption. Not sure if we need to say that here.
-@end ignore
-@end quotation
-
-You can disable the use of the persistent memory allocator in
-@command{gawk} with the @option{--disable-pma} option to the
@command{configure}
-command at the time that you build @command{gawk} (@pxref{Unix
-Installation}).
-
-@cindex @env{PMA_VERBOSITY} environment variable
-@cindex environment variables @subentry @env{PMA_VERBOSITY}
-You can set the @env{PMA_VERBOSITY} environment variable to a
-value between zero and three to control how much debugging
-and error information the persistent memory allocator will print.
-@command{gawk} sets the default to one. See the @file{support/pma.c}
-source code to understand what the different verbosity levels are.
-
-There are a few constraints on the use of persistent memory:
-
-@itemize @bullet
-@item
-If you use MPFR mode (the @option{-M} option) on the first run
-of a program using persistent memory, you @emph{must} continue
-to use it on all subsequent runs. Similarly, if you don't use @option{-M}
-on the first run, do not use it on any subsequent runs.
-
-Mixing and matching MPFR mode and regular mode with the same backing
-file is not allowed. @command{gawk} detects such a situation and issues
-a fatal error message.
-
-@item
-The GNU/Linux CIFS filesystem is known to not
-work well with the PMA allocator.
-Don't use a backing file on a CIFS filesystem.
-
-@item
-If @command{gawk} is run by the @command{root} user, then
-persistent memory is not allowed. This is to avoid the possibility
-of private data ``leaking'' into the backing file and being
-recovered later by an attacker.
-
-@item
-Over time, the backing file will be filled with memory ``leaked''
-by @command{gawk} as it runs. Most notably this is the memory used
-to compile your program into an internal form before running it,
-which happens each time, but there are other leakages as well.
-(For an extreme example of this, see
-@uref{https://lists.gnu.org/archive/html/bug-gawk/2023-04/msg00025.html,
-this thread} in the @EMAIL{bug-gawk@@gnu-org, bug-gawk at gnu.org}
-mailing list archives.) It is up to you to use @samp{du -sh
-@var{pmafile}} occasionally to monitor how full the file is, and
-arrange to dump any data you may need before the backing file becomes
-full.
-@end itemize
-
-Terence Kelly has provided a separate @cite{@value{PMGAWKTITLE}}
-document, which is included in the @command{gawk}
-distribution. It is worth reading.
-@ifinfo
-@xref{Top, , General Introduction, pm-gawk, @value{PMGAWKTITLE}}.
-@end ifinfo
-
-Here are additional articles and web links that provide more information about
-persistent memory and why it's useful in a scripting language like
-@command{gawk}.
-
-@cindex Kelly, Terence
-@table @asis
-@item @uref{https://web.eecs.umich.edu/~tpkelly/pma/}
-This is the canonical source for Terence Kelly's Persistent Memory
-Allocator (PMA). The latest source code and user manual
-will always be available at this location.
-Kelly may be reached directly at any of the following
-email addresses:
-@EMAIL{tpkelly@@acm.org, tpkelly AT acm.org},
-@EMAIL{tpkelly@@cs.princeton.edu, tpkelly AT cs.princeton.edu}, or
-@EMAIL{tpkelly@@eecs.umich.edu, tpkelly AT eecs.umich.edu}.
-
-@item @cite{Persistent Memory Allocation}
-Terence Kelly, Zi Fan Tan, Jianan Li, and Haris Volos,
-ACM @cite{Queue} magazine, Vol. 20 No. 2 (March/April 2022),
-@uref{https://dl.acm.org/doi/pdf/10.1145/3534855, PDF},
-@uref{https://queue.acm.org/detail.cfm?id=3534855, HTML}.
-This paper explains the design of the PMA
-allocator used in persistent @command{gawk}.
-
-@item @cite{Persistent Scripting}
-Zi Fan Tan, Jianan Li, Haris Volos, and Terence Kelly,
-Non-Volatile Memory Workshop (NVMW) 2022,
-@uref{http://nvmw.ucsd.edu/program/}.
-This paper motivates and describes a research prototype of persistent
-@command{gawk} and presents performance evaluations on Intel Optane
-non-volatile memory; note that the interface differs slightly.
-
-@item @cite{Persistent Memory Programming on Conventional Hardware}
-Terence Kelly,
-ACM @cite{Queue} magazine Vol. 17 No. 4 (July/Aug 2019),
-@uref{https://dl.acm.org/doi/pdf/10.1145/3358955.3358957, PDF},
-@uref{https://queue.acm.org/detail.cfm?id=3358957, HTML}.
-This paper describes simple techniques for persistent memory for C/C++
-code on conventional computers that lack non-volatile memory hardware.
-
-@item @cite{Is Persistent Memory Persistent?}
-Terence Kelly,
-ACM @cite{Queue} magazine Vol. 18 No. 2 (March/April 2020),
-@uref{https://dl.acm.org/doi/pdf/10.1145/3400899.3400902, PDF},
-@uref{https://queue.acm.org/detail.cfm?id=3400902, HTML}.
-This paper describes a simple and robust testbed for testing software
-against real power failures.
-
-@item @cite{Crashproofing the Original NoSQL Key/Value Store}
-Terence Kelly,
-ACM @cite{Queue} magazine Vol. 19 No. 4 (July/Aug 2021),
-@uref{https://dl.acm.org/doi/pdf/10.1145/3487019.3487353, PDF},
-@uref{https://queue.acm.org/detail.cfm?id=3487353, HTML}.
-This paper describes a crash-tolerance feature added to GNU DBM'
-(@code{gdbm}).
-@end table
-
-When Terence Kelly published his papers, his collaborators produced
-a prototype integration of PMA with @command{gawk}. That version used
-a (mandatory!) option @option{--persist=@var{file}} to specify the file
-for storing the persistent heap. If this option is given to @command{gawk},
-it produces a fatal error message instructing the user to use the
-@env{GAWK_PERSIST_FILE} environment variable instead. Except for this
-paragraph, that option is otherwise undocumented.
-
-The prototype only supported persistent data; it did not
-support persistent functions.
-
-As noted earlier, support for persistent memory is @emph{experimental}.
-If it becomes burdensome,@footnote{Meaning, there are too many
-bug reports, or too many strange differences in behavior from when
-@command{gawk} is run normally.} then the feature will be removed.
-
-@node Extension Philosophy
-@section Builtin Features versus Extensions
-
-As this and subsequent @value{CHAPTER}s show, @command{gawk} has a
-large number of extensions over standard @command{awk} built-in to
-the program. These have developed over time. More recently, the
-focus has moved to using the extension mechanism (@pxref{Dynamic Extensions})
-for adding features. This @value{SECTION} discusses the ``guiding philosophy''
-behind what should be added to the interpreter as a built-in
-feature versus what should be done in extensions.
-
-There are several goals:
-
-@enumerate 1
-@item
-Keep the language @command{awk}; it should not become unrecognizable, even
-if programs in it will only run on @command{gawk}.
-
-@item
-Keep the core from getting any larger unless absolutely necessary.
-
-@item
-Add new functionality either in @command{awk} scripts (@option{-f},
-@code{@@include}) or in loadable extensions written in C or C++
-(@option{-l}, @code{@@load}).
-
-@item
-Extend the core interpreter only if some feature is:
-
-@c sublist
-@enumerate A
-@item
-Truly desirable.
-@item
-Cannot be done via library files or loadable extensions.
-@item
-Can be implemented without too much pain in the core.
-@end enumerate
-@end enumerate
-Combining modules with @command{awk} files is a powerful technique.
-Some of the sample extensions demonstrate this.
-
-Loading extensions and library files should not be done automatically,
-because then there's overhead that most users don't want or need.
-
-@node Advanced Features Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-The @option{--non-decimal-data} option causes @command{gawk} to treat
-octal- and hexadecimal-looking input data as octal and hexadecimal.
-This option should be used with caution or not at all; use of @code{strtonum()}
-is preferable.
-Note that this option may disappear in a future version of @command{gawk}.
-
-@item
-You can take over complete control of sorting in @samp{for (@var{indx} in
@var{array})}
-array traversal by setting @code{PROCINFO["sorted_in"]} to the name of a
user-defined
-function that does the comparison of array elements based on index and value.
-
-@item
-Similarly, you can supply the name of a user-defined comparison function as the
-third argument to either @code{asort()} or @command{asorti()} to control how
-those functions sort arrays. Or you may provide one of the predefined control
-strings that work for @code{PROCINFO["sorted_in"]}.
-
-@item
-You can use the @samp{|&} operator to create a two-way pipe to a coprocess.
-You read from the coprocess with @code{getline} and write to it with
@code{print}
-or @code{printf}. Use @code{close()} to close off the coprocess completely, or
-optionally, close off one side of the two-way communications.
-
-@item
-By using special @value{FN}s with the @samp{|&} operator, you can open a
-TCP/IP (or UDP/IP) connection to remote hosts on the Internet. @command{gawk}
-supports both IPv4 and IPv6.
-
-@item
-You can generate statement count profiles of your program. This can help you
-determine which parts of your program may be taking the most time and let
-you tune them more easily. Sending the @code{USR1} signal while profiling
causes
-@command{gawk} to dump the profile and keep going, including a function call
stack.
-
-@item
-You can also just ``pretty-print'' the program.
-
-@item
-Persistent memory allows you to preserve the values of variables and arrays
-between runs of @command{gawk}. This feature is currently experimental.
-
-@item
-New features should be developed using the extension mechanism if possible;
-they should be added to the core interpreter only as a last resort.
-@end itemize
-
-
-@node Internationalization
-@chapter Internationalization with @command{gawk}
-
-@cindex Robbins @subentry Malka
-@cindex Moon, Sailor
-@cindex Sailor Moon @seeentry{Moon, Sailor}
-@quotation
-@i{Moon@dots{} Gorgeous@dots{} MEDITATION!}
-@author Pretty Guardian Sailor Moon Eternal, The Movie
-@end quotation
-
-@quotation
-@i{It probably sounded better in Japanese.}
-@author Malka Robbins
-@end quotation
-
-Once upon a time, computer makers
-wrote software that worked only in English.
-Eventually, hardware and software vendors noticed that if their
-systems worked in the native languages of non-English-speaking
-countries, they were able to sell more systems.
-As a result, internationalization and localization
-of programs and software systems became a common practice.
-
-@cindex internationalization @subentry localization
-@cindex @command{gawk} @subentry internationalization
@seeentry{internationalization}
-@cindex internationalization @subentry localization @subentry @command{gawk}
and
-For many years, the ability to provide internationalization
-was largely restricted to programs written in C and C++.
-This @value{CHAPTER} describes the underlying library @command{gawk}
-uses for internationalization, as well as how
-@command{gawk} makes internationalization
-features available at the @command{awk} program level.
-Having internationalization available at the @command{awk} level
-gives software developers additional flexibility---they are no
-longer forced to write in C or C++ when internationalization is
-a requirement.
-
-@menu
-* I18N and L10N:: Internationalization and Localization.
-* Explaining gettext:: How GNU @command{gettext} works.
-* Programmer i18n:: Features for the programmer.
-* Translator i18n:: Features for the translator.
-* I18N Example:: A simple i18n example.
-* Gawk I18N:: @command{gawk} is also internationalized.
-* I18N Summary:: Summary of I18N stuff.
-@end menu
-
-@node I18N and L10N
-@section Internationalization and Localization
-
-@cindex internationalization
-@cindex localization @seeentry{internationalization, localization}
-@cindex internationalization @subentry localization
-@dfn{Internationalization} means writing (or modifying) a program once,
-in such a way that it can use multiple languages without requiring
-further source code changes.
-@dfn{Localization} means providing the data necessary for an
-internationalized program to work in a particular language.
-Most typically, these terms refer to features such as the language
-used for printing error messages, the language used to read
-responses, and information related to how numerical and
-monetary values are printed and read.
-
-@node Explaining gettext
-@section GNU @command{gettext}
-
-@cindex internationalizing a program
-@cindex @command{gettext} library
-@command{gawk} uses GNU @command{gettext} to provide its internationalization
-features.
-The facilities in GNU @command{gettext} focus on messages: strings printed
-by a program, either directly or via formatting with @code{printf} or
-@code{sprintf()}.@footnote{For some operating systems, the @command{gawk}
-port doesn't support GNU @command{gettext}.
-Therefore, these features are not available
-if you are using one of those operating systems. Sorry.}
-
-@cindex portability @subentry @command{gettext} library and
-When using GNU @command{gettext}, each application has its own
-@dfn{text domain}. This is a unique name, such as @samp{kpilot} or
@samp{gawk},
-that identifies the application.
-A complete application may have multiple components---programs written
-in C or C++, as well as scripts written in @command{sh} or @command{awk}.
-All of the components use the same text domain.
-
-To make the discussion concrete, assume we're writing an application
-named @command{guide}. Internationalization consists of the
-following steps, in this order:
-
-@enumerate
-@item
-The programmer reviews the source for all of @command{guide}'s components
-and marks each string that is a candidate for translation.
-For example, @code{"`-F': option required"} is a good candidate for
translation.
-A table with strings of option names is not (e.g., @command{gawk}'s
-@option{--profile} option should remain the same, no matter what the local
-language).
-
-@cindex @code{textdomain()} function (C library)
-@cindex C library functions @subentry @code{textdomain()}
-@item
-The programmer indicates the application's text domain
-(@command{"guide"}) to the @command{gettext} library,
-by calling the @code{textdomain()} function.
-
-@cindex @code{.pot} files
-@cindex files @subentry @code{.pot}
-@cindex portable object @subentry template files
-@cindex files @subentry portable object @subentry template file (@file{.pot})
-@item
-Messages from the application are extracted from the source code and
-collected into a portable object template file (@file{guide.pot}),
-which lists the strings and their translations.
-The translations are initially empty.
-The original (usually English) messages serve as the key for
-lookup of the translations.
-
-@cindex @code{.po} files
-@cindex files @subentry @code{.po}
-@cindex portable object @subentry files
-@cindex files @subentry portable object
-@item
-For each language with a translator, @file{guide.pot}
-is copied to a portable object file (@code{.po})
-and translations are created and shipped with the application.
-For example, there might be a @file{fr.po} for a French translation.
-
-@cindex @code{.gmo} files
-@cindex files @subentry @code{.gmo}
-@cindex message object files
-@cindex files @subentry message object
-@item
-Each language's @file{.po} file is converted into a binary
-message object (@file{.gmo}) file.
-A message object file contains the original messages and their
-translations in a binary format that allows fast lookup of translations
-at runtime.
-
-@item
-When @command{guide} is built and installed, the binary translation files
-are installed in a standard place.
-
-@cindex @code{bindtextdomain()} function (C library)
-@cindex C library functions @subentry @code{bindtextdomain()}
-@item
-For testing and development, it is possible to tell @command{gettext}
-to use @file{.gmo} files in a different directory than the standard
-one by using the @code{bindtextdomain()} function.
-
-@cindex @code{.gmo} files @subentry specifying directory of
-@cindex files @subentry @code{.gmo} @subentry specifying directory of
-@cindex message object files @subentry specifying directory of
-@cindex files @subentry message object @subentry specifying directory of
-@item
-At runtime, @command{guide} looks up each string via a call
-to @code{gettext()}. The returned string is the translated string
-if available, or the original string if not.
-
-@item
-If necessary, it is possible to access messages from a different
-text domain than the one belonging to the application, without
-having to switch the application's default text domain back
-and forth.
-@end enumerate
-
-@cindex @code{gettext()} function (C library)
-@cindex C library functions @subentry @code{gettext()}
-In C (or C++), the string marking and dynamic translation lookup
-are accomplished by wrapping each string in a call to @code{gettext()}:
-
-@example
-printf("%s", gettext("Don't Panic!\n"));
-@end example
-
-The tools that extract messages from source code pull out all
-strings enclosed in calls to @code{gettext()}.
-
-@cindex @code{_} (underscore) @subentry C macro
-@cindex underscore (@code{_}) @subentry C macro
-The GNU @command{gettext} developers, recognizing that typing
-@samp{gettext(@dots{})} over and over again is both painful and ugly to look
-at, use the macro @samp{_} (an underscore) to make things easier:
-
-@example
-/* In the standard header file: */
-#define _(str) gettext(str)
-
-/* In the program text: */
-printf("%s", _("Don't Panic!\n"));
-@end example
-
-@cindex internationalization @subentry localization @subentry locale categories
-@cindex @command{gettext} library @subentry locale categories
-@cindex locale categories
-@noindent
-This reduces the typing overhead to just three extra characters per string
-and is considerably easier to read as well.
-
-There are locale @dfn{categories}
-for different types of locale-related information.
-The defined locale categories that @command{gettext} knows about are:
-
-@table @code
-@cindex @code{LC_MESSAGES} locale category
-@item LC_MESSAGES
-Text messages. This is the default category for @command{gettext}
-operations, but it is possible to supply a different one explicitly,
-if necessary. (It is almost never necessary to supply a different category.)
-
-@cindex sorting characters in different languages
-@cindex @code{LC_COLLATE} locale category
-@item LC_COLLATE
-Text-collation information (i.e., how different characters
-and/or groups of characters sort in a given language).
-
-@cindex @code{LC_CTYPE} locale category
-@item LC_CTYPE
-Character-type information (alphabetic, digit, upper- or lowercase, and
-so on) as well as character encoding.
-@ignore
-In June 2001 Bruno Haible wrote:
-- Description of LC_CTYPE: It determines both
- 1. character encoding,
- 2. character type information.
- (For example, in both KOI8-R and ISO-8859-5 the character type information
- is the same - cyrillic letters could as 'alpha' - but the encoding is
- different.)
-@end ignore
-This information is accessed via the
-POSIX character classes in regular expressions,
-such as @code{/[[:alnum:]]/}
-(@pxref{Bracket Expressions}).
-
-@cindex monetary information, localization
-@cindex currency symbols, localization
-@cindex internationalization @subentry localization @subentry monetary
information
-@cindex internationalization @subentry localization @subentry currency symbols
-@cindex @code{LC_MONETARY} locale category
-@item LC_MONETARY
-Monetary information, such as the currency symbol, and whether the
-symbol goes before or after a number.
-
-@cindex @code{LC_NUMERIC} locale category
-@item LC_NUMERIC
-Numeric information, such as which characters to use for the decimal
-point and the thousands separator.@footnote{Americans
-use a comma every three decimal places and a period for the decimal
-point, while many Europeans do exactly the opposite:
-1,234.56 versus 1.234,56.}
-
-@cindex time @subentry localization and
-@cindex dates @subentry information related to, localization
-@cindex @code{LC_TIME} locale category
-@item LC_TIME
-Time- and date-related information, such as 12- or 24-hour clock, month printed
-before or after the day in a date, local month abbreviations, and so on.
-
-@cindex @code{LC_ALL} locale category
-@item LC_ALL
-All of the above. (Not too useful in the context of @command{gettext}.)
-@end table
-
-@quotation NOTE
-@cindex @env{LANGUAGE} environment variable
-@cindex environment variables @subentry @env{LANGUAGE}
-As described in @ref{Locales}, environment variables with the same
-name as the locale categories (@env{LC_CTYPE}, @env{LC_ALL}, etc.)
-influence @command{gawk}'s behavior (and that of other utilities).
-
-Normally, these variables also affect how the @code{gettext} library
-finds translations. However, the @env{LANGUAGE} environment variable
-overrides the @env{LC_@var{xxx}} variables. Many GNU/Linux systems
-may define this variable without your knowledge, causing @command{gawk}
-to not find the correct translations. If this happens to you,
-look to see if @env{LANGUAGE} is defined, and if so, use the shell's
-@command{unset} command to remove it.
-@end quotation
-
-@cindex @env{GAWK_LOCALE_DIR} environment variable
-@cindex environment variables @subentry @env{GAWK_LOCALE_DIR}
-For testing translations of @command{gawk} itself, you can set
-the @env{GAWK_LOCALE_DIR} environment variable. See the documentation
-for the C @code{bindtextdomain()} function and also see
-@ref{Other Environment Variables}.
-
-@node Programmer i18n
-@section Internationalizing @command{awk} Programs
-@cindex @command{awk} programs @subentry internationalizing
-
-@command{gawk} provides the following variables for
-internationalization:
-
-@table @code
-@cindex @code{TEXTDOMAIN} variable
-@item TEXTDOMAIN
-This variable indicates the application's text domain.
-For compatibility with GNU @command{gettext}, the default
-value is @code{"messages"}.
-
-@cindex internationalization @subentry localization @subentry marked strings
-@cindex strings @subentry for localization
-@item _"your message here"
-String constants marked with a leading underscore
-are candidates for translation at runtime.
-String constants without a leading underscore are not translated.
-@end table
-
-@command{gawk} provides the following functions for
-internationalization:
-
-@table @code
-@cindexgawkfunc{dcgettext}
-@item @code{dcgettext(@var{string}} [@code{,} @var{domain} [@code{,}
@var{category}]]@code{)}
-Return the translation of @var{string} in
-text domain @var{domain} for locale category @var{category}.
-The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
-The default value for @var{category} is @code{"LC_MESSAGES"}.
-
-If you supply a value for @var{category}, it must be a string equal to
-one of the known locale categories described in
-@ifnotinfo
-the previous @value{SECTION}.
-@end ifnotinfo
-@ifinfo
-@ref{Explaining gettext}.
-@end ifinfo
-You must also supply a text domain. Use @code{TEXTDOMAIN} if
-you want to use the current domain.
-
-@quotation CAUTION
-The order of arguments to the @command{awk} version
-of the @code{dcgettext()} function is purposely different from the order for
-the C version. The @command{awk} version's order was
-chosen to be simple and to allow for reasonable @command{awk}-style
-default arguments.
-@end quotation
-
-@cindexgawkfunc{dcngettext}
-@item @code{dcngettext(@var{string1}, @var{string2}, @var{number}} [@code{,}
@var{domain} [@code{,} @var{category}]]@code{)}
-Return the plural form used for @var{number} of the
-translation of @var{string1} and @var{string2} in text domain
-@var{domain} for locale category @var{category}. @var{string1} is the
-English singular variant of a message, and @var{string2} is the English plural
-variant of the same message.
-The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
-The default value for @var{category} is @code{"LC_MESSAGES"}.
-
-The same remarks about argument order as for the @code{dcgettext()} function
apply.
-
-@cindex @code{.gmo} files @subentry specifying directory of
-@cindex files @subentry @code{.gmo} @subentry specifying directory of
-@cindex message object files @subentry specifying directory of
-@cindex files @subentry message object @subentry specifying directory of
-@cindexgawkfunc{bindtextdomain}
-@item @code{bindtextdomain(@var{directory}} [@code{,} @var{domain} ]@code{)}
-Change the directory in which
-@command{gettext} looks for @file{.gmo} files, in case they
-will not or cannot be placed in the standard locations
-(e.g., during testing).
-Return the directory in which @var{domain} is ``bound.''
-
-The default @var{domain} is the value of @code{TEXTDOMAIN}.
-If @var{directory} is the null string (@code{""}), then
-@code{bindtextdomain()} returns the current binding for the
-given @var{domain}.
-@end table
-
-To use these facilities in your @command{awk} program, follow these steps:
-
-@enumerate
-@cindex @code{BEGIN} pattern @subentry @code{TEXTDOMAIN} variable and
-@cindex @code{TEXTDOMAIN} variable @subentry @code{BEGIN} pattern and
-@item
-Set the variable @code{TEXTDOMAIN} to the text domain of
-your program. This is best done in a @code{BEGIN} rule
-(@pxref{BEGIN/END}),
-or it can also be done via the @option{-v} command-line
-option (@pxref{Options}):
-
-@example
-BEGIN @{
- TEXTDOMAIN = "guide"
- @dots{}
-@}
-@end example
-
-@cindex @code{_} (underscore) @subentry translatable strings
-@cindex underscore (@code{_}) @subentry translatable strings
-@item
-Mark all translatable strings with a leading underscore (@samp{_})
-character. It @emph{must} be adjacent to the opening
-quote of the string. For example:
-
-@example
-print _"hello, world"
-x = _"you goofed"
-printf(_"Number of users is %d\n", nusers)
-@end example
-
-@item
-If you are creating strings dynamically, you can
-still translate them, using the @code{dcgettext()}
-built-in function:@footnote{Thanks to Bruno Haible for this
-example.}
-
-@example
-if (groggy)
- message = dcgettext("%d customers disturbing me\n", "adminprog")
-else
- message = dcgettext("enjoying %d customers\n", "adminprog")
-printf(message, ncustomers)
-@end example
-
-Here, the call to @code{dcgettext()} supplies a different
-text domain (@code{"adminprog"}) in which to find the
-message, but it uses the default @code{"LC_MESSAGES"} category.
-
-The previous example only works if @code{ncustomers} is greater than one.
-This example would be better done with @code{dcngettext()}:
-
-@example
-if (groggy)
- message = dcngettext("%d customer disturbing me\n",
- "%d customers disturbing me\n",
- ncustomers, "adminprog")
-else
- message = dcngettext("enjoying %d customer\n",
- "enjoying %d customers\n",
- ncustomers, "adminprog")
-printf(message, ncustomers)
-@end example
-
-
-@cindex @code{LC_MESSAGES} locale category @subentry @code{bindtextdomain()}
function (@command{gawk})
-@item
-During development, you might want to put the @file{.gmo}
-file in a private directory for testing. This is done
-with the @code{bindtextdomain()} built-in function:
-
-@example
-BEGIN @{
- TEXTDOMAIN = "guide" # our text domain
- if (Testing) @{
- # where to find our files
- bindtextdomain("testdir")
- # joe is in charge of adminprog
- bindtextdomain("../joe/testdir", "adminprog")
- @}
- @dots{}
-@}
-@end example
-
-@end enumerate
-
-@xref{I18N Example}
-for an example program showing the steps to create
-and use translations from @command{awk}.
-
-@node Translator i18n
-@section Translating @command{awk} Programs
-
-@cindex @code{.po} files
-@cindex files @subentry @code{.po}
-@cindex portable object @subentry files
-@cindex files @subentry portable object
-Once a program's translatable strings have been marked, they must
-be extracted to create the initial @file{.pot} file.
-As part of translation, it is often helpful to rearrange the order
-in which arguments to @code{printf} are output.
-
-@command{gawk}'s @option{--gen-pot} command-line option extracts
-the messages and is discussed next.
-After that, @code{printf}'s ability to
-rearrange the order for @code{printf} arguments at runtime
-is covered.
-
-@menu
-* String Extraction:: Extracting marked strings.
-* Printf Ordering:: Rearranging @code{printf} arguments.
-* I18N Portability:: @command{awk}-level portability issues.
-@end menu
-
-@node String Extraction
-@subsection Extracting Marked Strings
-@cindex strings @subentry extracting
-@cindex @option{--gen-pot} option
-@cindex command line @subentry options @subentry string extraction
-@cindex string @subentry extraction (internationalization)
-@cindex marked string extraction (internationalization)
-@cindex extraction, of marked strings (internationalization)
-
-@cindex @option{--gen-pot} option
-Once your @command{awk} program is working, and all the strings have
-been marked and you've set (and perhaps bound) the text domain,
-it is time to produce translations.
-First, use the @option{--gen-pot} command-line option to create
-the initial @file{.pot} file:
-
-@example
-gawk --gen-pot -f guide.awk > guide.pot
-@end example
-
-@cindex @command{xgettext} utility
-When run with @option{--gen-pot}, @command{gawk} does not execute your
-program. Instead, it parses it as usual and prints all marked strings
-to standard output in the format of a GNU @command{gettext} Portable Object
-file. Also included in the output are any constant strings that
-appear as the first argument to @code{dcgettext()} or as the first and
-second argument to @code{dcngettext()}.@footnote{The
-@command{xgettext} utility that comes with GNU
-@command{gettext} can handle @file{.awk} files.}
-You should distribute the generated @file{.pot} file with
-your @command{awk} program; translators will eventually use it
-to provide you translations that you can also then distribute.
-@xref{I18N Example}
-for the full list of steps to go through to create and test
-translations for @command{guide}.
-
-@node Printf Ordering
-@subsection Rearranging @code{printf} Arguments
-
-@cindex @code{printf} statement @subentry positional specifiers
-@cindex positional specifiers, @code{printf} statement
-Format strings for @code{printf} and @code{sprintf()}
-(@pxref{Printf})
-present a special problem for translation.
-Consider the following:@footnote{This example is borrowed
-from the GNU @command{gettext} manual.}
-
-@example
-printf(_"String `%s' has %d characters\n",
- string, length(string)))
-@end example
-
-A possible German translation for this might be:
-
-@example
-"%d Zeichen lang ist die Zeichenkette `%s'\n"
-@end example
-
-The problem should be obvious: the order of the format
-specifications is different from the original!
-Even though @code{gettext()} can return the translated string
-at runtime,
-it cannot change the argument order in the call to @code{printf}.
-
-To solve this problem, @code{printf} format specifiers may have
-an additional optional element, which we call a @dfn{positional specifier}.
-For example:
-
-@example
-"%2$d Zeichen lang ist die Zeichenkette `%1$s'\n"
-@end example
-
-Here, the positional specifier consists of an integer count, which indicates
which
-argument to use, and a @samp{$}. Counts are one-based, and the
-format string itself is @emph{not} included. Thus, in the following
-example, @samp{string} is the first argument and @samp{length(string)} is the
second:
-
-@example
-$ @kbd{gawk 'BEGIN @{}
-> @kbd{string = "Don\47t Panic"}
-> @kbd{printf "%2$d characters live in \"%1$s\"\n",}
-> @kbd{string, length(string)}
-> @kbd{@}'}
-@print{} 11 characters live in "Don't Panic"
-@end example
-
-If present, positional specifiers come first in the format specification,
-before the flags, the field width, and/or the precision.
-
-Positional specifiers can be used with the dynamic field width and
-precision capability:
-
-@example
-$ @kbd{gawk 'BEGIN @{}
-> @kbd{printf("%*.*s\n", 10, 20, "hello")}
-> @kbd{printf("%3$*2$.*1$s\n", 20, 10, "hello")}
-> @kbd{@}'}
-@print{} hello
-@print{} hello
-@end example
-
-@quotation NOTE
-When using @samp{*} with a positional specifier, the @samp{*}
-comes first, then the integer position, and then the @samp{$}.
-This is somewhat counterintuitive.
-@end quotation
-
-@cindex @code{printf} statement @subentry positional specifiers @subentry
mixing with regular formats
-@cindex positional specifiers, @code{printf} statement @subentry mixing with
regular formats
-@cindex format specifiers @subentry mixing regular with positional specifiers
-@command{gawk} does not allow you to mix regular format specifiers
-and those with positional specifiers in the same string:
-
-@example
-@group
-$ @kbd{gawk 'BEGIN @{ printf "%d %3$s\n", 1, 2, "hi" @}'}
-@error{} gawk: cmd. line:1: fatal: must use `count$' on all formats or none
-@end group
-@end example
-
-@quotation NOTE
-There are some pathological cases that @command{gawk} may fail to
-diagnose. In such cases, the output may not be what you expect.
-It's still a bad idea to try mixing them, even if @command{gawk}
-doesn't detect it.
-@end quotation
-
-Although positional specifiers can be used directly in @command{awk} programs,
-their primary purpose is to help in producing correct translations of
-format strings into languages different from the one in which the program
-is first written.
-
-@node I18N Portability
-@subsection @command{awk} Portability Issues
-
-@cindex portability @subentry internationalization and
-@cindex internationalization @subentry localization @subentry portability and
-@command{gawk}'s internationalization features were purposely chosen to
-have as little impact as possible on the portability of @command{awk}
-programs that use them to other versions of @command{awk}.
-Consider this program:
-
-@example
-BEGIN @{
- TEXTDOMAIN = "guide"
- if (Test_Guide) # set with -v
- bindtextdomain("/test/guide/messages")
- print _"don't panic!"
-@}
-@end example
-
-@noindent
-As written, it won't work on other versions of @command{awk}.
-However, it is actually almost portable, requiring very little
-change:
-
-@itemize @value{BULLET}
-@cindex @code{TEXTDOMAIN} variable @subentry portability and
-@item
-Assignments to @code{TEXTDOMAIN} won't have any effect,
-because @code{TEXTDOMAIN} is not special in other @command{awk}
implementations.
-
-@item
-Non-GNU versions of @command{awk} treat marked strings
-as the concatenation of a variable named @code{_} with the string
-following it.@footnote{This is good fodder for an ``Obfuscated
-@command{awk}'' contest.} Typically, the variable @code{_} has
-the null string (@code{""}) as its value, leaving the original string constant
as
-the result.
-
-@item
-By defining ``dummy'' functions to replace @code{dcgettext()},
@code{dcngettext()},
-and @code{bindtextdomain()}, the @command{awk} program can be made to run, but
-all the messages are output in the original language.
-For example:
-
-@cindex @code{bindtextdomain()} function (@command{gawk}) @subentry
portability and
-@cindex @code{dcgettext()} function (@command{gawk}) @subentry portability and
-@cindex @code{dcngettext()} function (@command{gawk}) @subentry portability and
-@example
-@c file eg/lib/libintl.awk
-function bindtextdomain(dir, domain)
-@{
- return dir
-@}
-
-function dcgettext(string, domain, category)
-@{
- return string
-@}
-
-function dcngettext(string1, string2, number, domain, category)
-@{
- return (number == 1 ? string1 : string2)
-@}
-@c endfile
-@end example
-
-@item
-The use of positional specifications in @code{printf} or
-@code{sprintf()} is @emph{not} portable.
-To support @code{gettext()} at the C level, many systems' C versions of
-@code{sprintf()} do support positional specifiers. But it works only if
-enough arguments are supplied in the function call. Many versions of
-@command{awk} pass @code{printf} formats and arguments unchanged to the
-underlying C library version of @code{sprintf()}, but only one format and
-argument at a time. What happens if a positional specification is
-used is anybody's guess.
-However, because the positional specifications are primarily for use in
-@emph{translated} format strings, and because non-GNU @command{awk}s never
-retrieve the translated string, this should not be a problem in practice.
-@end itemize
-
-@node I18N Example
-@section A Simple Internationalization Example
-
-Now let's look at a step-by-step example of how to internationalize and
-localize a simple @command{awk} program, using @file{guide.awk} as our
-original source:
-
-@example
-@c file eg/prog/guide.awk
-BEGIN @{
- TEXTDOMAIN = "guide"
- bindtextdomain(".") # for testing
- print _"Don't Panic"
- print _"The Answer Is", 42
- print "Pardon me, Zaphod who?"
-@}
-@c endfile
-@end example
-
-@noindent
-Run @samp{gawk --gen-pot} to create the @file{.pot} file:
-
-@example
-$ @kbd{gawk --gen-pot -f guide.awk > guide.pot}
-@end example
-
-@noindent
-This produces:
-
-@example
-@c file eg/data/guide.po
-#: guide.awk:4
-msgid "Don't Panic"
-msgstr ""
-
-#: guide.awk:5
-msgid "The Answer Is"
-msgstr ""
-
-@c endfile
-@end example
-
-This original portable object template file is saved and reused for each
language
-into which the application is translated. The @code{msgid}
-is the original string and the @code{msgstr} is the translation.
-
-@quotation NOTE
-Strings not marked with a leading underscore do not
-appear in the @file{guide.pot} file.
-@end quotation
-
-Next, the messages must be translated.
-Here is a translation to a hypothetical dialect of English,
-called ``Mellow'':@footnote{Perhaps it would be better if it were
-called ``Hippy.'' Ah, well.}
-
-@example
-@group
-$ @kbd{cp guide.pot guide-mellow.po}
-@var{Add translations to} guide-mellow.po @dots{}
-@end group
-@end example
-
-@noindent
-Following are the translations:
-
-@example
-@c file eg/data/guide-mellow.po
-#: guide.awk:4
-msgid "Don't Panic"
-msgstr "Hey man, relax!"
-
-#: guide.awk:5
-msgid "The Answer Is"
-msgstr "Like, the scoop is"
-
-@c endfile
-@end example
-
-@cindex GNU/Linux
-@quotation NOTE
-The following instructions apply to GNU/Linux with the GNU C Library. Be
-aware that the actual steps may change over time, that the following
-description may not be accurate for all GNU/Linux distributions, and
-that things may work entirely differently on other operating systems.
-@end quotation
-
-The next step is to make the directory to hold the binary message object
-file and then to create the @file{guide.mo} file.
-The directory has the form @file{@var{locale}/LC_MESSAGES}, where
-@var{locale} is a locale name known to the C @command{gettext} routines.
-
-@cindex @env{LANGUAGE} environment variable
-@cindex environment variables @subentry @env{LANGUAGE}
-@cindex @env{LC_ALL} environment variable
-@cindex environment variables @subentry @env{LC_ALL}
-@cindex @env{LANG} environment variable
-@cindex environment variables @subentry @env{LANG}
-@cindex @env{LC_MESSAGES} environment variable
-@cindex environment variables @subentry @env{LC_MESSAGES}
-How do we know which locale to use? It turns out that there are
-four different environment variables used by the C @command{gettext} routines.
-In order, they are @env{$LANGUAGE}, @env{$LC_ALL}, @env{$LANG}, and
-@env{$LC_MESSAGES}.@footnote{Well, sort of. It seems that if @env{$LC_ALL}
-is set to @samp{C}, then no translations are done. Go figure.}
-Thus, we check the value of @env{$LANGUAGE}:
-
-@example
-$ @kbd{echo $LANGUAGE}
-@print{} en_US.UTF-8
-@end example
-
-@noindent
-We next make the directories:
-
-@example
-$ @kbd{mkdir en_US.UTF-8 en_US.UTF-8/LC_MESSAGES}
-@end example
-
-@cindex @code{.po} files @subentry converting to @code{.mo}
-@cindex files @subentry @code{.po} @subentry converting to @code{.mo}
-@cindex @code{.mo} files, converting from @code{.po}
-@cindex files @subentry @code{.mo}, converting from @code{.po}
-@cindex portable object @subentry files @subentry converting to message object
files
-@cindex files @subentry portable object @subentry converting to message object
files
-@cindex message object files @subentry converting from portable object files
-@cindex files @subentry message object @subentry converting from portable
object files
-@cindex @command{msgfmt} utility
-The @command{msgfmt} utility converts the human-readable
-@file{.po} file into a machine-readable @file{.mo} file.
-By default, @command{msgfmt} creates a file named @file{messages}.
-This file must be renamed and placed in the proper directory (using
-the @option{-o} option) so that @command{gawk} can find it:
-
-@example
-$ @kbd{msgfmt guide-mellow.po -o en_US.UTF-8/LC_MESSAGES/guide.mo}
-@end example
-
-Finally, we run the program to test it:
-
-@example
-$ @kbd{gawk -f guide.awk}
-@print{} Hey man, relax!
-@print{} Like, the scoop is 42
-@print{} Pardon me, Zaphod who?
-@end example
-
-If the three replacement functions for @code{dcgettext()}, @code{dcngettext()},
-and @code{bindtextdomain()}
-(@pxref{I18N Portability})
-are in a file named @file{libintl.awk},
-then we can run @file{guide.awk} unchanged as follows:
-
-@example
-$ @kbd{gawk --posix -f guide.awk -f libintl.awk}
-@print{} Don't Panic
-@print{} The Answer Is 42
-@print{} Pardon me, Zaphod who?
-@end example
-
-@node Gawk I18N
-@section @command{gawk} Can Speak Your Language
-
-@command{gawk} itself has been internationalized
-using the GNU @command{gettext} package.
-(GNU @command{gettext} is described in
-complete detail in
-@ifinfo
-@xref{Top, , GNU @command{gettext} utilities, gettext, GNU @command{gettext}
utilities}.)
-@end ifinfo
-@ifnotinfo
-@uref{https://www.gnu.org/software/gettext/manual/,
-@cite{GNU @command{gettext} utilities}}.)
-@end ifnotinfo
-As of this writing, the latest version of GNU @command{gettext} is
-@uref{ftp://ftp.gnu.org/gnu/gettext/gettext-0.19.8.1.tar.gz,
-@value{PVERSION} 0.19.8.1}.
-
-If a translation of @command{gawk}'s messages exists,
-then @command{gawk} produces usage messages, warnings,
-and fatal errors in the local language.
-
-@node I18N Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Internationalization means writing a program such that it can use multiple
-languages without requiring source code changes. Localization means
-providing the data necessary for an internationalized program to work
-in a particular language.
-
-@item
-@command{gawk} uses GNU @command{gettext} to let you internationalize
-and localize @command{awk} programs. A program's text domain identifies
-the program for grouping all messages and other data together.
-
-@item
-You mark a program's strings for translation by preceding them with
-an underscore. Once that is done, the strings are extracted into a
-@file{.pot} file. This file is copied for each language into a @file{.po}
-file, and the @file{.po} files are compiled into @file{.gmo} files for
-use at runtime.
-
-@item
-You can use positional specifications with @code{sprintf()} and
-@code{printf} to rearrange the placement of argument values in formatted
-strings and output. This is useful for the translation of format
-control strings.
-
-@item
-The internationalization features have been designed so that they
-can be easily worked around in a standard @command{awk}.
-
-@item
-@command{gawk} itself has been internationalized and ships with
-a number of translations for its messages.
-
-@end itemize
-
-
-@node Debugger
-@chapter Debugging @command{awk} Programs
-@cindex debugging @subentry @command{awk} programs
-
-@c The original text for this chapter was contributed by Efraim Yawitz.
-
-It would be nice if computer programs worked perfectly the first time they
-were run, but in real life, this rarely happens for programs of
-any complexity. Thus, most programming languages have facilities available
-for ``debugging'' programs, and @command{awk} is no exception.
-
-The @command{gawk} debugger is purposely modeled after
-@uref{https://www.gnu.org/software/gdb/, the GNU Debugger (GDB)}
-command-line debugger. If you are familiar with GDB, learning
-how to use @command{gawk} for debugging your programs is easy.
-
-@menu
-* Debugging:: Introduction to @command{gawk} debugger.
-* Sample Debugging Session:: Sample debugging session.
-* List of Debugger Commands:: Main debugger commands.
-* Readline Support:: Readline support.
-* Limitations:: Limitations and future plans.
-* Debugging Summary:: Debugging summary.
-@end menu
-
-@node Debugging
-@section Introduction to the @command{gawk} Debugger
-
-This @value{SECTION} introduces debugging in general and begins
-the discussion of debugging in @command{gawk}.
-
-@menu
-* Debugging Concepts:: Debugging in General.
-* Debugging Terms:: Additional Debugging Concepts.
-* Awk Debugging:: Awk Debugging.
-@end menu
-
-@node Debugging Concepts
-@subsection Debugging in General
-
-(If you have used debuggers in other languages, you may want to skip
-ahead to @ref{Awk Debugging}.)
-
-Of course, a debugging program cannot remove bugs for you, because it has
-no way of knowing what you or your users consider a ``bug'' versus a
-``feature.'' (Sometimes, we humans have a hard time with this ourselves.)
-In that case, what can you expect from such a tool? The answer to that
-depends on the language being debugged, but in general, you can expect at
-least the following:
-
-@cindex debugger @subentry capabilities
-@itemize @value{BULLET}
-@item
-The ability to watch a program execute its instructions one by one,
-giving you, the programmer, the opportunity to think about what is happening
-on a time scale of seconds, minutes, or hours, rather than the nanosecond
-time scale at which the code usually runs.
-
-@item
-The opportunity to not only passively observe the operation of your
-program, but to control it and try different paths of execution, without
-having to change your source files.
-
-@item
-The chance to see the values of data in the program at any point in
-execution, and also to change that data on the fly, to see how that
-affects what happens afterward. (This often includes the ability
-to look at internal data structures besides the variables you actually
-defined in your code.)
-
-@item
-The ability to obtain additional information about your program's state
-or even its internal structure.
-@end itemize
-
-All of these tools provide a great amount of help in using your own
-skills and understanding of the goals of your program to find where it
-is going wrong (or, for that matter, to better comprehend a perfectly
-functional program that you or someone else wrote).
-
-@node Debugging Terms
-@subsection Debugging Concepts
-
-@cindex debugger @subentry concepts
-Before diving in to the details, we need to introduce several
-important concepts that apply to just about all debuggers.
-The following list defines terms used throughout the rest of
-this @value{CHAPTER}:
-
-@table @dfn
-@cindex call stack @subentry explanation of
-@cindex stack frame (debugger)
-@item Stack frame
-Programs generally call functions during the course of their execution.
-One function can call another, or a function can call itself (recursion).
-You can view the chain of called functions (main program calls A, which
-calls B, which calls C), as a stack of executing functions: the currently
-running function is the topmost one on the stack, and when it finishes
-(returns), the next one down then becomes the active function.
-Such a stack is termed a @dfn{call stack}.
-
-For each function on the call stack, the system maintains a data area
-that contains the function's parameters, local variables, and return value,
-as well as any other ``bookkeeping'' information needed to manage the
-call stack. This data area is termed a @dfn{stack frame}.
-
-@command{gawk} also follows this model, and gives you
-access to the call stack and to each stack frame. You can see the
-call stack, as well as from where each function on the stack was
-invoked. Commands that print the call stack print information about
-each stack frame (as detailed later on).
-
-@item Breakpoint
-@cindex breakpoint
-During debugging, you often wish to let the program run until it
-reaches a certain point, and then continue execution from there one
-statement (or instruction) at a time. The way to do this is to set
-a @dfn{breakpoint} within the program. A breakpoint is where the
-execution of the program should break off (stop), so that you can
-take over control of the program's execution. You can add and remove
-as many breakpoints as you like.
-
-@item Watchpoint
-@cindex watchpoint (debugger)
-A watchpoint is similar to a breakpoint. The difference is that
-breakpoints are oriented around the code: stop when a certain point in the
-code is reached. A watchpoint, however, specifies that program execution
-should stop when a @emph{data value} is changed. This is useful, as
-sometimes it happens that a variable receives an erroneous value, and it's
-hard to track down where this happens just by looking at the code.
-By using a watchpoint, you can stop whenever a variable is assigned to,
-and usually find the errant code quite quickly.
-@end table
-
-@node Awk Debugging
-@subsection @command{awk} Debugging
-
-Debugging an @command{awk} program has some specific aspects that are
-not shared with programs written in other languages.
-
-First of all, the fact that @command{awk} programs usually take input
-line by line from a file or files and operate on those lines using specific
-rules makes it especially useful to organize viewing the execution of
-the program in terms of these rules. As we will see, each @command{awk}
-rule is treated almost like a function call, with its own specific block
-of instructions.
-
-In addition, because @command{awk} is by design a very concise language,
-it is easy to lose sight of everything that is going on ``inside''
-each line of @command{awk} code. The debugger provides the opportunity
-to look at the individual primitive instructions carried out
-by the higher-level @command{awk} commands.@footnote{The ``primitive
-instructions'' are defined by @command{gawk} itself; the debugger
-does not work at the level of machine instructions.}
-
-@node Sample Debugging Session
-@section Sample @command{gawk} Debugging Session
-@cindex sample debugging session
-@cindex example debugging session
-@cindex debugging @subentry example session
-
-In order to illustrate the use of @command{gawk} as a debugger, let's look at
a sample
-debugging session. We will use the @command{awk} implementation of the
-POSIX @command{uniq} command presented earlier (@pxref{Uniq Program})
-as our example.
-
-@menu
-* Debugger Invocation:: How to Start the Debugger.
-* Finding The Bug:: Finding the Bug.
-@end menu
-
-@node Debugger Invocation
-@subsection How to Start the Debugger
-@cindex starting the debugger
-@cindex debugger @subentry how to start
-
-Starting the debugger is almost exactly like running @command{gawk} normally,
-except you have to pass an additional option, @option{--debug}, or the
-corresponding short option, @option{-D}. The file(s) containing the
-program and any supporting code are given on the command line as arguments
-to one or more @option{-f} options. (@command{gawk} is not designed
-to debug command-line programs, only programs contained in files.)
-In our case, we invoke the debugger like this:
-
-@example
-$ @kbd{gawk -D -f getopt.awk -f join.awk -f uniq.awk -- -1 inputfile}
-@end example
-
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-@noindent
-where both @file{getopt.awk} and @file{uniq.awk} are in @env{$AWKPATH}.
-(Experienced users of GDB or similar debuggers should note that
-this syntax is slightly different from what you are used to.
-With the @command{gawk} debugger, you give the arguments for running the
program
-in the command line to the debugger rather than as part of the @code{run}
-command at the debugger prompt.)
-The @option{--} ends @command{gawk}'s command line options. It's not
-strictly necessary here, but it is needed if an option to the @command{awk}
-program conflicts with a @command{gawk} option.
-The @option{-1} is an option to @file{uniq.awk}.
-
-@cindex debugger @subentry prompt
-Instead of immediately running the program on @file{inputfile}, as
-@command{gawk} would ordinarily do, the debugger merely loads all
-the program source files, compiles them internally, and then gives
-us a prompt:
-
-@example
-gawk>
-@end example
-
-@noindent
-from which we can issue commands to the debugger. At this point, no
-code has been executed.
-
-@node Finding The Bug
-@subsection Finding the Bug
-
-Let's say that we are having a problem using (a faulty version of)
-@file{uniq.awk} in ``field-skipping'' mode, and it doesn't seem to be
-catching lines which should be identical when skipping the first field,
-such as:
-
-@example
-awk is a wonderful program!
-gawk is a wonderful program!
-@end example
-
-This could happen if we were thinking (C-like) of the fields in a record
-as being numbered in a zero-based fashion, so instead of the lines:
-
-@example
-clast = join(alast, fcount+1, n)
-cline = join(aline, fcount+1, m)
-@end example
-
-@noindent
-we wrote:
-
-@example
-clast = join(alast, fcount, n)
-cline = join(aline, fcount, m)
-@end example
-
-The first thing we usually want to do when trying to investigate a
-problem like this is to put a breakpoint in the program so that we can
-watch it at work and catch what it is doing wrong. A reasonable spot for
-a breakpoint in @file{uniq.awk} is at the beginning of the function
-@code{are_equal()}, which compares the current line with the previous one. To
set
-the breakpoint, use the @code{b} (breakpoint) command:
-
-@cindex debugger @subentry setting a breakpoint
-@cindex debugger @subentry commands @subentry @code{breakpoint}
-@cindex debugger @subentry commands @subentry @code{break}
-@cindex debugger @subentry commands @subentry @code{b} (@code{break})
-@example
-gawk> @kbd{b are_equal}
-@print{} Breakpoint 1 set at file `awklib/eg/prog/uniq.awk', line 63
-@end example
-
-The debugger tells us the file and line number where the breakpoint is.
-Now type @samp{r} or @samp{run} and the program runs until it hits
-the breakpoint for the first time:
-
-@cindex debugger @subentry running the program
-@cindex debugger @subentry commands @subentry @code{run}
-@example
-gawk> @kbd{r}
-@print{} Starting program:
-@print{} Stopping in Rule ...
-@print{} Breakpoint 1, are_equal(n, m, clast, cline, alast, aline)
- at `awklib/eg/prog/uniq.awk':63
-@print{} 63 if (fcount == 0 && charcount == 0)
-gawk>
-@end example
-
-Now we can look at what's going on inside our program. First of all,
-let's see how we got to where we are. At the prompt, we type @samp{bt}
-(short for ``backtrace''), and the debugger responds with a
-listing of the current stack frames:
-
-@cindex debugger @subentry stack frames, showing
-@cindex debugger @subentry commands @subentry @code{bt} (@code{backtrace})
-@cindex debugger @subentry commands @subentry @code{backtrace}
-@example
-gawk> @kbd{bt}
-@print{} #0 are_equal(n, m, clast, cline, alast, aline)
- at `awklib/eg/prog/uniq.awk':68
-@print{} #1 in main() at `awklib/eg/prog/uniq.awk':88
-@end example
-
-This tells us that @code{are_equal()} was called by the main program at
-line 88 of @file{uniq.awk}. (This is not a big surprise, because this
-is the only call to @code{are_equal()} in the program, but in more complex
-programs, knowing who called a function and with what parameters can be
-the key to finding the source of the problem.)
-
-Now that we're in @code{are_equal()}, we can start looking at the values
-of some variables. Let's say we type @samp{p n}
-(@code{p} is short for ``print''). We would expect to see the value of
-@code{n}, a parameter to @code{are_equal()}. Actually, the debugger
-gives us:
-
-@cindex debugger @subentry commands @subentry @code{print}
-@cindex debugger @subentry commands @subentry @code{p} (@code{print})
-@example
-gawk> @kbd{p n}
-@print{} n = untyped variable
-@end example
-
-@noindent
-In this case, @code{n} is an uninitialized local variable, because the
-function was called without arguments (@pxref{Function Calls}).
-
-A more useful variable to display might be the current record:
-
-@example
-gawk> @kbd{p $0}
-@print{} $0 = "gawk is a wonderful program!"
-@end example
-
-@noindent
-This might be a bit puzzling at first, as this is the second line of
-our test input. Let's look at @code{NR}:
-
-@example
-gawk> @kbd{p NR}
-@print{} NR = 2
-@end example
-
-@noindent
-So we can see that @code{are_equal()} was only called for the second record
-of the file. Of course, this is because our program contains a rule for
-@samp{NR == 1}:
-
-@example
-NR == 1 @{
- last = $0
- next
-@}
-@end example
-
-OK, let's just check that that rule worked correctly:
-
-@example
-gawk> @kbd{p last}
-@print{} last = "awk is a wonderful program!"
-@end example
-
-Everything we have done so far has verified that the program has worked as
-planned, up to and including the call to @code{are_equal()}, so the problem
must
-be inside this function. To investigate further, we must begin
-``stepping through'' the lines of @code{are_equal()}. We start by typing
-@samp{n} (for ``next''):
-
-@cindex debugger @subentry commands @subentry @code{n} (@code{next})
-@cindex debugger @subentry commands @subentry @code{next}
-@example
-@group
-gawk> @kbd{n}
-@print{} 66 if (fcount > 0) @{
-@end group
-@end example
-
-This tells us that @command{gawk} is now ready to execute line 66, which
-decides whether to give the lines the special ``field-skipping'' treatment
-indicated by the @option{-1} command-line option. (Notice that we skipped
-from where we were before, at line 63, to here, because the condition
-in line 63, @samp{if (fcount == 0 && charcount == 0)}, was false.)
-
-Continuing to step, we now get to the splitting of the current and
-last records:
-
-@example
-gawk> @kbd{n}
-@print{} 67 n = split(last, alast)
-gawk> @kbd{n}
-@print{} 68 m = split($0, aline)
-@end example
-
-At this point, we should be curious to see what our records were split
-into, so we try to look:
-
-@example
-gawk> @kbd{p n m alast aline}
-@print{} n = 5
-@print{} m = untyped variable
-@print{} alast = array, 5 elements
-@print{} aline = untyped variable
-@end example
-
-@noindent
-(The @code{p} command can take more than one argument, similar to
-@command{awk}'s @code{print} statement.)
-
-This is kind of disappointing, though. All we found out is that there
-are five elements in @code{alast}; @code{m} and @code{aline} don't have
-values because we are at line 68 but haven't executed it yet.
-This information is useful enough (we now know that
-none of the words were accidentally left out), but what if we want to see
-inside the array?
-
-@cindex debugger @subentry printing single array elements
-The first choice would be to use subscripts:
-
-@example
-gawk> @kbd{p alast[0]}
-@print{} "0" not in array `alast'
-@end example
-
-@noindent
-Oops!
-
-@example
-gawk> @kbd{p alast[1]}
-@print{} alast["1"] = "awk"
-@end example
-
-This would be kind of slow for a 100-member array, though, so
-@command{gawk} provides a shortcut (reminiscent of another language
-not to be mentioned):
-
-@cindex debugger @subentry printing all array elements
-@example
-gawk> @kbd{p @@alast}
-@print{} alast["1"] = "awk"
-@print{} alast["2"] = "is"
-@print{} alast["3"] = "a"
-@print{} alast["4"] = "wonderful"
-@print{} alast["5"] = "program!"
-@end example
-
-It looks like we got this far OK. Let's take another step
-or two:
-
-@example
-gawk> @kbd{n}
-@print{} 69 clast = join(alast, fcount, n)
-gawk> @kbd{n}
-@print{} 70 cline = join(aline, fcount, m)
-@end example
-
-Well, here we are at our error (sorry to spoil the suspense). What we
-had in mind was to join the fields starting from the second one to make
-the virtual record to compare, and if the first field were numbered zero,
-this would work. Let's look at what we've got:
-
-@example
-gawk> @kbd{p cline clast}
-@print{} cline = "gawk is a wonderful program!"
-@print{} clast = "awk is a wonderful program!"
-@end example
-
-Hey, those look pretty familiar! They're just our original, unaltered
-input records. A little thinking (the human brain is still the best
-debugging tool), and we realize that we were off by one!
-
-We get out of the debugger:
-
-@example
-gawk> @kbd{q}
-@print{} The program is running. Exit anyway (y/n)? @kbd{y}
-@end example
-
-@noindent
-Then we get into an editor:
-
-@example
-clast = join(alast, fcount+1, n)
-cline = join(aline, fcount+1, m)
-@end example
-
-@noindent
-and problem solved!
-
-@node List of Debugger Commands
-@section Main Debugger Commands
-
-The @command{gawk} debugger command set can be divided into the
-following categories:
-
-@itemize @value{BULLET}
-
-@item
-Breakpoint control
-
-@item
-Execution control
-
-@item
-Viewing and changing data
-
-@item
-Working with the stack
-
-@item
-Getting information
-
-@item
-Miscellaneous
-@end itemize
-
-@cindex debugger @subentry repeating commands
-Each of these are discussed in the following subsections.
-In the following descriptions, commands that may be abbreviated
-show the abbreviation on a second description line.
-A debugger command name may also be truncated if that partial
-name is unambiguous. The debugger has the built-in capability to
-automatically repeat the previous command just by hitting @kbd{Enter}.
-This works for the commands @code{list}, @code{next}, @code{nexti},
-@code{step}, @code{stepi}, and @code{continue} executed without any
-argument.
-
-@menu
-* Breakpoint Control:: Control of Breakpoints.
-* Debugger Execution Control:: Control of Execution.
-* Viewing And Changing Data:: Viewing and Changing Data.
-* Execution Stack:: Dealing with the Stack.
-* Debugger Info:: Obtaining Information about the Program and
- the Debugger State.
-* Miscellaneous Debugger Commands:: Miscellaneous Commands.
-@end menu
-
-@node Breakpoint Control
-@subsection Control of Breakpoints
-
-As we saw earlier, the first thing you probably want to do in a debugging
-session is to get your breakpoints set up, because your program
-will otherwise just run as if it was not under the debugger. The commands for
-controlling breakpoints are:
-
-@table @asis
-@cindex debugger @subentry commands @subentry @code{b} (@code{break})
-@cindex debugger @subentry commands @subentry @code{break}
-@cindex @code{break} debugger command
-@cindex @code{b} debugger command (alias for @code{break})
-@cindex set breakpoint
-@cindex breakpoint @subentry setting
-@item @code{break} [[@var{filename}@code{:}]@var{n} | @var{function}]
[@code{"@var{expression}"}]
-@itemx @code{b} [[@var{filename}@code{:}]@var{n} | @var{function}]
[@code{"@var{expression}"}]
-Without any argument, set a breakpoint at the next instruction
-to be executed in the selected stack frame.
-Arguments can be one of the following:
-
-@c @asis for docbook
-@c nested table
-@table @asis
-@item @var{n}
-Set a breakpoint at line number @var{n} in the current source file.
-
-@item @var{filename}@code{:}@var{n}
-Set a breakpoint at line number @var{n} in source file @var{filename}.
-
-@item @var{function}
-Set a breakpoint at entry to (the first instruction of)
-function @var{function}.
-@end table
-
-Each breakpoint is assigned a number that can be used to delete it from
-the breakpoint list using the @code{delete} command.
-
-With a breakpoint, you may also supply a condition. This is an
-@command{awk} expression (enclosed in double quotes) that the debugger
-evaluates whenever the breakpoint is reached. If the condition is true,
-then the debugger stops execution and prompts for a command. Otherwise,
-it continues executing the program.
-
-@cindex debugger @subentry commands @subentry @code{clear}
-@cindex @code{clear} debugger command
-@cindex delete breakpoint @subentry at location
-@cindex breakpoint @subentry at location, how to delete
-@item @code{clear} [[@var{filename}@code{:}]@var{n} | @var{function}]
-Without any argument, delete any breakpoint at the next instruction
-to be executed in the selected stack frame. If the program stops at
-a breakpoint, this deletes that breakpoint so that the program
-does not stop at that location again. Arguments can be one of the following:
-
-@c nested table
-@table @asis
-@item @var{n}
-Delete breakpoint(s) set at line number @var{n} in the current source file.
-
-@item @var{filename}@code{:}@var{n}
-Delete breakpoint(s) set at line number @var{n} in source file @var{filename}.
-
-@item @var{function}
-Delete breakpoint(s) set at entry to function @var{function}.
-@end table
-
-@cindex debugger @subentry commands @subentry @code{condition}
-@cindex @code{condition} debugger command
-@cindex breakpoint @subentry condition
-@item @code{condition} @var{n} @code{"@var{expression}"}
-Add a condition to existing breakpoint or watchpoint @var{n}. The
-condition is an @command{awk} expression @emph{enclosed in double quotes}
-that the debugger evaluates
-whenever the breakpoint or watchpoint is reached. If the condition is true,
then
-the debugger stops execution and prompts for a command. Otherwise,
-the debugger continues executing the program. If the condition expression is
-not specified, any existing condition is removed (i.e., the breakpoint or
-watchpoint is made unconditional).
-
-@cindex debugger @subentry commands @subentry @code{d} (@code{delete})
-@cindex debugger @subentry commands @subentry @code{delete}
-@cindex @code{delete} debugger command
-@cindex @code{d} debugger command (alias for @code{delete})
-@cindex delete breakpoint @subentry by number
-@cindex breakpoint @subentry delete by number
-@item @code{delete} [@var{n1 n2} @dots{}] [@var{n}--@var{m}]
-@itemx @code{d} [@var{n1 n2} @dots{}] [@var{n}--@var{m}]
-Delete specified breakpoints or a range of breakpoints. Delete
-all defined breakpoints if no argument is supplied.
-
-@cindex debugger @subentry commands @subentry @code{disable}
-@cindex @code{disable} debugger command
-@cindex disable breakpoint
-@cindex breakpoint @subentry how to disable or enable
-@item @code{disable} [@var{n1 n2} @dots{} | @var{n}--@var{m}]
-Disable specified breakpoints or a range of breakpoints. Without
-any argument, disable all breakpoints.
-
-@cindex debugger @subentry commands @subentry @code{e} (@code{enable})
-@cindex debugger @subentry commands @subentry @code{enable}
-@cindex @code{enable} debugger command
-@cindex @code{e} debugger command (alias for @code{enable})
-@cindex enable breakpoint
-@item @code{enable} [@code{del} | @code{once}] [@var{n1 n2} @dots{}]
[@var{n}--@var{m}]
-@itemx @code{e} [@code{del} | @code{once}] [@var{n1 n2} @dots{}]
[@var{n}--@var{m}]
-Enable specified breakpoints or a range of breakpoints. Without
-any argument, enable all breakpoints.
-Optionally, you can specify how to enable the breakpoints:
-
-@c nested table
-@table @code
-@item del
-Enable the breakpoints temporarily, then delete each one when
-the program stops at it.
-
-@item once
-Enable the breakpoints temporarily, then disable each one when
-the program stops at it.
-@end table
-
-@cindex debugger @subentry commands @subentry @code{ignore}
-@cindex @code{ignore} debugger command
-@cindex ignore breakpoint
-@item @code{ignore} @var{n} @var{count}
-Ignore breakpoint number @var{n} the next @var{count} times it is
-hit.
-
-@cindex debugger @subentry commands @subentry @code{t} (@code{tbreak})
-@cindex debugger @subentry commands @subentry @code{tbreak}
-@cindex @code{tbreak} debugger command
-@cindex @code{t} debugger command (alias for @code{tbreak})
-@cindex temporary breakpoint
-@item @code{tbreak} [[@var{filename}@code{:}]@var{n} | @var{function}]
-@itemx @code{t} [[@var{filename}@code{:}]@var{n} | @var{function}]
-Set a temporary breakpoint (enabled for only one stop).
-The arguments are the same as for @code{break}.
-@end table
-
-@node Debugger Execution Control
-@subsection Control of Execution
-
-Now that your breakpoints are ready, you can start running the program
-and observing its behavior. There are more commands for controlling
-execution of the program than we saw in our earlier example:
-
-@table @asis
-@cindex debugger @subentry commands @subentry @code{commands}
-@cindex @code{commands} debugger command
-@cindex debugger @subentry commands @subentry @code{silent}
-@cindex @code{silent} debugger command
-@cindex debugger @subentry commands @subentry @code{end}
-@cindex @code{end} debugger command
-@cindex breakpoint @subentry commands to execute at
-@cindex commands to execute at breakpoint
-@item @code{commands} [@var{n}]
-@itemx @code{silent}
-@itemx @dots{}
-@itemx @code{end}
-Set a list of commands to be executed upon stopping at
-a breakpoint or watchpoint. @var{n} is the breakpoint or watchpoint number.
-Without a number, the last one set is used. The actual commands follow,
-starting on the next line, and terminated by the @code{end} command.
-If the command @code{silent} is in the list, the usual messages about
-stopping at a breakpoint and the source line are not printed. Any command
-in the list that resumes execution (e.g., @code{continue}) terminates the list
-(an implicit @code{end}), and subsequent commands are ignored.
-For example:
-
-@example
-gawk> @kbd{commands}
-> @kbd{silent}
-> @kbd{printf "A silent breakpoint; i = %d\n", i}
-> @kbd{info locals}
-> @kbd{set i = 10}
-> @kbd{continue}
-> @kbd{end}
-gawk>
-@end example
-
-@cindex debugger @subentry commands @subentry @code{c} (@code{continue})
-@cindex debugger @subentry commands @subentry @code{continue}
-@cindex continue program, in debugger
-@cindex @code{continue} debugger command
-@item @code{continue} [@var{count}]
-@itemx @code{c} [@var{count}]
-Resume program execution. If continued from a breakpoint and @var{count} is
-specified, ignore the breakpoint at that location the next @var{count} times
-before stopping.
-
-@cindex debugger @subentry commands @subentry @code{finish}
-@cindex @code{finish} debugger command
-@item @code{finish}
-Execute until the selected stack frame returns.
-Print the returned value.
-
-@cindex debugger @subentry commands @subentry @code{n} (@code{next})
-@cindex debugger @subentry commands @subentry @code{next}
-@cindex @code{next} debugger command
-@cindex @code{n} debugger command (alias for @code{next})
-@cindex single-step execution, in the debugger
-@item @code{next} [@var{count}]
-@itemx @code{n} [@var{count}]
-Continue execution to the next source line, stepping over function calls.
-The argument @var{count} controls how many times to repeat the action, as
-in @code{step}.
-
-@cindex debugger @subentry commands @subentry @code{ni} (@code{nexti})
-@cindex debugger @subentry commands @subentry @code{nexti}
-@cindex @code{nexti} debugger command
-@cindex @code{ni} debugger command (alias for @code{nexti})
-@item @code{nexti} [@var{count}]
-@itemx @code{ni} [@var{count}]
-Execute one (or @var{count}) instruction(s), stepping over function calls.
-
-@cindex debugger @subentry commands @subentry @code{return}
-@cindex @code{return} debugger command
-@item @code{return} [@var{value}]
-Cancel execution of a function call. If @var{value} (either a string or a
-number) is specified, it is used as the function's return value. If used in a
-frame other than the innermost one (the currently executing function; i.e.,
-frame number 0), discard all inner frames in addition to the selected one,
-and the caller of that frame becomes the innermost frame.
-
-@cindex debugger @subentry commands @subentry @code{r} (@code{run})
-@cindex debugger @subentry commands @subentry @code{run}
-@cindex @code{run} debugger command
-@cindex @code{r} debugger command (alias for @code{run})
-@item @code{run}
-@itemx @code{r}
-Start/restart execution of the program. When restarting, the debugger
-retains the current breakpoints, watchpoints, command history,
-automatic display variables, and debugger options.
-
-@cindex debugger @subentry commands @subentry @code{s} (@code{step})
-@cindex debugger @subentry commands @subentry @code{step}
-@cindex @code{step} debugger command
-@cindex @code{s} debugger command (alias for @code{step})
-@item @code{step} [@var{count}]
-@itemx @code{s} [@var{count}]
-Continue execution until control reaches a different source line in the
-current stack frame, stepping inside any function called within
-the line. If the argument @var{count} is supplied, steps that many times
before
-stopping, unless it encounters a breakpoint or watchpoint.
-
-@cindex debugger @subentry commands @subentry @code{si} (@code{stepi})
-@cindex debugger @subentry commands @subentry @code{stepi}
-@cindex @code{stepi} debugger command
-@cindex @code{si} debugger command (alias for @code{stepi})
-@item @code{stepi} [@var{count}]
-@itemx @code{si} [@var{count}]
-Execute one (or @var{count}) instruction(s), stepping inside function calls.
-(For illustration of what is meant by an ``instruction'' in @command{gawk},
-see the output shown under @code{dump} in @ref{Miscellaneous Debugger
Commands}.)
-
-@cindex debugger @subentry commands @subentry @code{u} (@code{until})
-@cindex debugger @subentry commands @subentry @code{until}
-@cindex @code{until} debugger command
-@cindex @code{u} debugger command (alias for @code{until})
-@item @code{until} [[@var{filename}@code{:}]@var{n} | @var{function}]
-@itemx @code{u} [[@var{filename}@code{:}]@var{n} | @var{function}]
-Without any argument, continue execution until a line past the current
-line in the current stack frame is reached. With an argument,
-continue execution until the specified location is reached, or the current
-stack frame returns.
-@end table
-
-@node Viewing And Changing Data
-@subsection Viewing and Changing Data
-
-The commands for viewing and changing variables inside of @command{gawk} are:
-
-@table @asis
-@cindex debugger @subentry commands @subentry @code{display}
-@cindex @code{display} debugger command
-@item @code{display} [@var{var} | @code{$}@var{n}]
-Add variable @var{var} (or field @code{$@var{n}}) to the display list.
-The value of the variable or field is displayed each time the program stops.
-Each variable added to the list is identified by a unique number:
-
-@example
-gawk> @kbd{display x}
-@print{} 10: x = 1
-@end example
-
-@noindent
-This displays the assigned item number, the variable name, and its current
value.
-If the display variable refers to a function parameter, it is silently
-deleted from the list as soon as the execution reaches a context where
-no such variable of the given name exists.
-Without argument, @code{display} displays the current values of
-items on the list.
-
-@cindex debugger @subentry commands @subentry @code{eval}
-@cindex @code{eval} debugger command
-@cindex evaluate expressions, in debugger
-@item @code{eval "@var{awk statements}"}
-Evaluate @var{awk statements} in the context of the running program.
-You can do anything that an @command{awk} program would do: assign
-values to variables, call functions, and so on.
-
-@quotation NOTE
-You cannot use @code{eval} to execute a statement containing
-any of the following:
-@code{exit},
-@code{getline},
-@code{next},
-@code{nextfile},
-or
-@code{return}.
-@end quotation
-
-@item @code{eval} @var{param}, @dots{}
-@itemx @var{awk statements}
-@itemx @code{end}
-This form of @code{eval} is similar, but it allows you to define
-``local variables'' that exist in the context of the
-@var{awk statements}, instead of using variables or function
-parameters defined by the program.
-
-@cindex debugger @subentry commands @subentry @code{p} (@code{print})
-@cindex debugger @subentry commands @subentry @code{print}
-@cindex @code{print} debugger command
-@cindex @code{p} debugger command (alias for @code{print})
-@cindex print variables, in debugger
-@item @code{print} @var{var1}[@code{,} @var{var2} @dots{}]
-@itemx @code{p} @var{var1}[@code{,} @var{var2} @dots{}]
-Print the value of a @command{gawk} variable or field.
-Fields must be referenced by constants:
-
-@example
-gawk> @kbd{print $3}
-@end example
-
-@noindent
-This prints the third field in the input record (if the specified field does
not
-exist, it prints @samp{Null field}). A variable can be an array element, with
-the subscripts being constant string values. To print the contents of an array,
-prefix the name of the array with the @samp{@@} symbol:
-
-@example
-gawk> @kbd{print @@a}
-@end example
-
-@noindent
-This prints the indices and the corresponding values for all elements in
-the array @code{a}.
-
-@cindex debugger @subentry commands @subentry @code{printf}
-@cindex @code{printf} debugger command
-@item @code{printf} @var{format} [@code{,} @var{arg} @dots{}]
-Print formatted text. The @var{format} may include escape sequences,
-such as @samp{\n}
-(@pxref{Escape Sequences}).
-No newline is printed unless one is specified.
-
-@cindex debugger @subentry commands @subentry @code{set}
-@cindex @code{set} debugger command
-@cindex assign values to variables, in debugger
-@item @code{set} @var{var}@code{=}@var{value}
-Assign a constant (number or string) value to an @command{awk} variable
-or field.
-String values must be enclosed between double quotes (@code{"}@dots{}@code{"}).
-
-You can also set special @command{awk} variables, such as @code{FS},
-@code{NF}, @code{NR}, and so on.
-
-@cindex debugger @subentry commands @subentry @code{w} (@code{watch})
-@cindex debugger @subentry commands @subentry @code{watch}
-@cindex @code{watch} debugger command
-@cindex @code{w} debugger command (alias for @code{watch})
-@cindex set watchpoint
-@item @code{watch} @var{var} | @code{$}@var{n} [@code{"@var{expression}"}]
-@itemx @code{w} @var{var} | @code{$}@var{n} [@code{"@var{expression}"}]
-Add variable @var{var} (or field @code{$@var{n}}) to the watch list.
-The debugger then stops whenever
-the value of the variable or field changes. Each watched item is assigned a
-number that can be used to delete it from the watch list using the
-@code{unwatch} command.
-
-With a watchpoint, you may also supply a condition. This is an
-@command{awk} expression (enclosed in double quotes) that the debugger
-evaluates whenever the watchpoint is reached. If the condition is true,
-then the debugger stops execution and prompts for a command. Otherwise,
-@command{gawk} continues executing the program.
-
-@cindex debugger @subentry commands @subentry @code{undisplay}
-@cindex @code{undisplay} debugger command
-@cindex stop automatic display, in debugger
-@item @code{undisplay} [@var{n}]
-Remove item number @var{n} (or all items, if no argument) from the
-automatic display list.
-
-@cindex debugger @subentry commands @subentry @code{unwatch}
-@cindex @code{unwatch} debugger command
-@cindex delete watchpoint
-@item @code{unwatch} [@var{n}]
-Remove item number @var{n} (or all items, if no argument) from the
-watch list.
-
-@end table
-
-@node Execution Stack
-@subsection Working with the Stack
-
-Whenever you run a program that contains any function calls,
-@command{gawk} maintains a stack of all of the function calls leading up
-to where the program is right now. You can see how you got to where you are,
-and also move around in the stack to see what the state of things was in the
-functions that called the one you are in. The commands for doing this are:
-
-@table @asis
-@cindex debugger @subentry commands @subentry @code{bt} (@code{backtrace})
-@cindex debugger @subentry commands @subentry @code{backtrace}
-@cindex debugger @subentry commands @subentry @code{where} (@code{backtrace})
-@cindex @code{backtrace} debugger command
-@cindex @code{bt} debugger command (alias for @code{backtrace})
-@cindex @code{where} debugger command (alias for @code{backtrace})
-@cindex call stack @subentry display in debugger
-@cindex traceback, display in debugger
-@item @code{backtrace} [@var{count}]
-@itemx @code{bt} [@var{count}]
-@itemx @code{where} [@var{count}]
-Print a backtrace of all function calls (stack frames), or innermost
@var{count}
-frames if @var{count} > 0. Print the outermost @var{count} frames if
-@var{count} < 0. The backtrace displays the name and arguments to each
-function, the source @value{FN}, and the line number.
-The alias @code{where} for @code{backtrace} is provided for longtime
-GDB users who may be used to that command.
-
-@cindex debugger @subentry commands @subentry @code{down}
-@cindex @code{down} debugger command
-@item @code{down} [@var{count}]
-Move @var{count} (default 1) frames down the stack toward the innermost frame.
-Then select and print the frame.
-
-@cindex debugger @subentry commands @subentry @code{f} (@code{frame})
-@cindex debugger @subentry commands @subentry @code{frame}
-@cindex @code{frame} debugger command
-@cindex @code{f} debugger command (alias for @code{frame})
-@item @code{frame} [@var{n}]
-@itemx @code{f} [@var{n}]
-Select and print stack frame @var{n}. Frame 0 is the currently executing,
-or @dfn{innermost}, frame (function call); frame 1 is the frame that
-called the innermost one. The highest-numbered frame is the one for the
-main program. The printed information consists of the frame number,
-function and argument names, source file, and the source line.
-
-@cindex debugger @subentry commands @subentry @code{up}
-@cindex @code{up} debugger command
-@item @code{up} [@var{count}]
-Move @var{count} (default 1) frames up the stack toward the outermost frame.
-Then select and print the frame.
-@end table
-
-@node Debugger Info
-@subsection Obtaining Information About the Program and the Debugger State
-
-Besides looking at the values of variables, there is often a need to get
-other sorts of information about the state of your program and of the
-debugging environment itself. The @command{gawk} debugger has one command that
-provides this information, appropriately called @code{info}. @code{info}
-is used with one of a number of arguments that tell it exactly what
-you want to know:
-
-@table @asis
-@cindex debugger @subentry commands @subentry @code{i} (@code{info})
-@cindex debugger @subentry commands @subentry @code{info}
-@cindex @code{info} debugger command
-@cindex @code{i} debugger command (alias for @code{info})
-@item @code{info} @var{what}
-@itemx @code{i} @var{what}
-The value for @var{what} should be one of the following:
-
-@c nested table
-@table @code
-@item args
-@cindex show in debugger @subentry function arguments
-@cindex function arguments, show in debugger
-List arguments of the selected frame.
-
-@item break
-@cindex show in debugger @subentry breakpoints
-@cindex breakpoint @subentry show all in debugger
-List all currently set breakpoints.
-
-@item display
-@cindex automatic displays, in debugger
-List all items in the automatic display list.
-
-@item frame
-@cindex describe call stack frame, in debugger
-Give a description of the selected stack frame.
-
-@item functions
-@cindex list function definitions, in debugger
-@cindex function definitions, list in debugger
-List all function definitions including source @value{FN}s and
-line numbers.
-
-@item locals
-@cindex show in debugger @subentry local variables
-@cindex local variables @subentry show in debugger
-List local variables of the selected frame.
-
-@item source
-@cindex show in debugger @subentry name of current source file
-@cindex current source file, show in debugger
-@cindex source file, show in debugger
-Print the name of the current source file. Each time the program stops, the
-current source file is the file containing the current instruction.
-When the debugger first starts, the current source file is the first file
-included via the @option{-f} option. The
-@samp{list @var{filename}:@var{lineno}} command can
-be used at any time to change the current source.
-
-@item sources
-@cindex show in debugger @subentry all source files
-@cindex all source files, show in debugger
-List all program sources.
-
-@item variables
-@cindex list all global variables, in debugger
-@cindex global variables, show in debugger
-List all global variables.
-
-@item watch
-@cindex show in debugger @subentry watchpoints
-@cindex watchpoints, show in debugger
-List all items in the watch list.
-@end table
-@end table
-
-Additional commands give you control over the debugger, the ability to
-save the debugger's state, and the ability to run debugger commands
-from a file. The commands are:
-
-@table @asis
-@cindex debugger @subentry commands @subentry @code{o} (@code{option})
-@cindex debugger @subentry commands @subentry @code{option}
-@cindex @code{option} debugger command
-@cindex @code{o} debugger command (alias for @code{option})
-@cindex display debugger options
-@cindex debugger @subentry options
-@item @code{option} [@var{name}[@code{=}@var{value}]]
-@itemx @code{o} [@var{name}[@code{=}@var{value}]]
-Without an argument, display the available debugger options
-and their current values. @samp{option @var{name}} shows the current
-value of the named option. @samp{option @var{name}=@var{value}} assigns
-a new value to the named option.
-The available options are:
-
-@c nested table
-@c asis for docbook
-@table @asis
-@item @code{history_size}
-@cindex debugger @subentry history size
-Set the maximum number of lines to keep in the history file
-@file{./.gawk_history}. The default is 100.
-
-@item @code{listsize}
-@cindex debugger @subentry default list amount
-Specify the number of lines that @code{list} prints. The default is 15.
-
-@item @code{outfile}
-@cindex redirect @command{gawk} output, in debugger
-Send @command{gawk} output to a file; debugger output still goes
-to standard output. An empty string (@code{""}) resets output to
-standard output.
-
-@item @code{prompt}
-@cindex debugger @subentry prompt
-Change the debugger prompt. The default is @samp{@w{gawk> }}.
-
-@item @code{save_history} [@code{on} | @code{off}]
-@cindex debugger @subentry history file
-Save command history to file @file{./.gawk_history}.
-The default is @code{on}.
-
-@item @code{save_options} [@code{on} | @code{off}]
-@cindex save debugger options
-Save current options to file @file{./.gawkrc} upon exit.
-The default is @code{on}.
-Options are read back into the next session upon startup.
-
-@item @code{trace} [@code{on} | @code{off}]
-@cindex instruction tracing, in debugger
-@cindex debugger @subentry instruction tracing
-Turn instruction tracing on or off. The default is @code{off}.
-@end table
-
-@cindex debugger @subentry save commands to a file
-@item @code{save} @var{filename}
-Save the commands from the current session to the given @value{FN},
-so that they can be replayed using the @command{source} command.
-
-@item @code{source} @var{filename}
-@cindex debugger @subentry read commands from a file
-Run command(s) from a file; an error in any command does not
-terminate execution of subsequent commands. Comments (lines starting
-with @samp{#}) are allowed in a command file.
-Empty lines are ignored; they do @emph{not}
-repeat the last command.
-You can't restart the program by having more than one @code{run}
-command in the file. Also, the list of commands may include additional
-@code{source} commands; however, the @command{gawk} debugger will not source
the
-same file more than once in order to avoid infinite recursion.
-
-In addition to, or instead of, the @code{source} command, you can use
-the @option{-D @var{file}} or @option{--debug=@var{file}} command-line
-options to execute commands from a file non-interactively
-(@pxref{Options}).
-@end table
-
-@node Miscellaneous Debugger Commands
-@subsection Miscellaneous Commands
-
-There are a few more commands that do not fit into the
-previous categories, as follows:
-
-@table @asis
-@cindex debugger @subentry commands @subentry @code{dump}
-@cindex @code{dump} debugger command
-@item @code{dump} [@var{filename}]
-Dump byte code of the program to standard output or to the file
-named in @var{filename}. This prints a representation of the internal
-instructions that @command{gawk} executes to implement the @command{awk}
-commands in a program. This can be very enlightening, as the following
-partial dump of Davide Brini's obfuscated code
-(@pxref{Signature Program}) demonstrates:
-
-@smallexample
-@group
-gawk> @kbd{dump}
-@print{} # BEGIN
-@print{}
-@print{} [ 1:0xfcd340] Op_rule : [in_rule = BEGIN] [source_file =
brini.awk]
-@end group
-@print{} [ 1:0xfcc240] Op_push_i : "~" [MALLOC|STRING|STRCUR]
-@print{} [ 1:0xfcc2a0] Op_push_i : "~" [MALLOC|STRING|STRCUR]
-@print{} [ 1:0xfcc280] Op_match :
-@print{} [ 1:0xfcc1e0] Op_store_var : O
-@print{} [ 1:0xfcc2e0] Op_push_i : "==" [MALLOC|STRING|STRCUR]
-@print{} [ 1:0xfcc340] Op_push_i : "==" [MALLOC|STRING|STRCUR]
-@print{} [ 1:0xfcc320] Op_equal :
-@print{} [ 1:0xfcc200] Op_store_var : o
-@print{} [ 1:0xfcc380] Op_push : o
-@print{} [ 1:0xfcc360] Op_plus_i : 0 [MALLOC|NUMCUR|NUMBER]
-@print{} [ 1:0xfcc220] Op_push_lhs : o [do_reference = true]
-@print{} [ 1:0xfcc300] Op_assign_plus :
-@print{} [ :0xfcc2c0] Op_pop :
-@print{} [ 1:0xfcc400] Op_push : O
-@print{} [ 1:0xfcc420] Op_push_i : "" [MALLOC|STRING|STRCUR]
-@print{} [ :0xfcc4a0] Op_no_op :
-@print{} [ 1:0xfcc480] Op_push : O
-@print{} [ :0xfcc4c0] Op_concat : [expr_count = 3] [concat_flag = 0]
-@print{} [ 1:0xfcc3c0] Op_store_var : x
-@print{} [ 1:0xfcc440] Op_push_lhs : X [do_reference = true]
-@print{} [ 1:0xfcc3a0] Op_postincrement :
-@print{} [ 1:0xfcc4e0] Op_push : x
-@print{} [ 1:0xfcc540] Op_push : o
-@print{} [ 1:0xfcc500] Op_plus :
-@print{} [ 1:0xfcc580] Op_push : o
-@print{} [ 1:0xfcc560] Op_plus :
-@print{} [ 1:0xfcc460] Op_leq :
-@print{} [ :0xfcc5c0] Op_jmp_false : [target_jmp = 0xfcc5e0]
-@print{} [ 1:0xfcc600] Op_push_i : "%c" [MALLOC|STRING|STRCUR]
-@print{} [ :0xfcc660] Op_no_op :
-@print{} [ 1:0xfcc520] Op_assign_concat : c
-@print{} [ :0xfcc620] Op_jmp : [target_jmp = 0xfcc440]
-@dots{}
-@print{} [ 2:0xfcc5a0] Op_K_printf : [expr_count = 17] [redir_type
= ""]
-@print{} [ :0xfcc140] Op_no_op :
-@print{} [ :0xfcc1c0] Op_atexit :
-@print{} [ :0xfcc640] Op_stop :
-@print{} [ :0xfcc180] Op_no_op :
-@print{} [ :0xfcd150] Op_after_beginfile :
-@group
-@print{} [ :0xfcc160] Op_no_op :
-@print{} [ :0xfcc1a0] Op_after_endfile :
-gawk>
-@end group
-@end smallexample
-
-@cindex @code{exit} debugger command
-@cindex exit the debugger
-@item @code{exit}
-Exit the debugger.
-See the entry for @samp{quit}, later in this list.
-
-@cindex debugger @subentry commands @subentry @code{h} (@code{help})
-@cindex debugger @subentry commands @subentry @code{help}
-@cindex @code{help} debugger command
-@cindex @code{h} debugger command (alias for @code{help})
-@item @code{help}
-@itemx @code{h}
-Print a list of all of the @command{gawk} debugger commands with a short
-summary of their usage. @samp{help @var{command}} prints the information
-about the command @var{command}.
-
-@cindex debugger @subentry commands @subentry @code{l} (@code{list})
-@cindex debugger @subentry commands @subentry @code{list}
-@cindex @code{list} debugger command
-@cindex @code{l} debugger command (alias for @code{list})
-@item @code{list} [@code{-} | @code{+} | @var{n} |
@var{filename}@code{:}@var{n} | @var{n}--@var{m} | @var{function}]
-@itemx @code{l} [@code{-} | @code{+} | @var{n} | @var{filename}@code{:}@var{n}
| @var{n}--@var{m} | @var{function}]
-Print the specified lines (default 15) from the current source file
-or the file named @var{filename}. The possible arguments to @code{list}
-are as follows:
-
-@c nested table
-@table @asis
-@item @code{-} (Minus)
-Print lines before the lines last printed.
-
-@item @code{+}
-Print lines after the lines last printed.
-@code{list} without any argument does the same thing.
-
-@item @var{n}
-Print lines centered around line number @var{n}.
-
-@item @var{n}--@var{m}
-Print lines from @var{n} to @var{m}.
-
-@item @var{filename}@code{:}@var{n}
-Print lines centered around line number @var{n} in
-source file @var{filename}. This command may change the current source file.
-
-@item @var{function}
-Print lines centered around the beginning of the
-function @var{function}. This command may change the current source file.
-@end table
-
-@cindex debugger @subentry commands @subentry @code{q} (@code{quit})
-@cindex debugger @subentry commands @subentry @code{quit}
-@cindex @code{quit} debugger command
-@cindex @code{q} debugger command (alias for @code{quit})
-@cindex exit the debugger
-@item @code{quit}
-@itemx @code{q}
-Exit the debugger. Debugging is great fun, but sometimes we all have
-to tend to other obligations in life, and sometimes we find the bug
-and are free to go on to the next one! As we saw earlier, if you are
-running a program, the debugger warns you when you type
-@samp{q} or @samp{quit}, to make sure you really want to quit.
-
-@cindex debugger @subentry commands @subentry @code{trace}
-@cindex @code{trace} debugger command
-@item @code{trace} [@code{on} | @code{off}]
-Turn on or off continuous printing of the instructions that are about to
-be executed, along with the @command{awk} lines they
-implement. The default is @code{off}.
-
-It is to be hoped that most of the ``opcodes'' in these instructions are
-fairly self-explanatory, and using @code{stepi} and @code{nexti} while
-@code{trace} is on will make them into familiar friends.
-
-@end table
-
-@node Readline Support
-@section Readline Support
-@cindex command completion, in debugger
-@cindex debugger @subentry command completion
-@cindex history expansion, in debugger
-@cindex debugger @subentry history expansion
-
-If @command{gawk} is compiled with
-@uref{http://cnswww.cns.cwru.edu/php/chet/readline/readline.html,
-the GNU Readline library}, you can take advantage of that library's
-command completion and history expansion features. The following types
-of completion are available:
-
-@table @asis
-@item Command completion
-Command names.
-
-@item Source @value{FN} completion
-Source @value{FN}s. Relevant commands are
-@code{break},
-@code{clear},
-@code{list},
-@code{tbreak},
-and
-@code{until}.
-
-@item Argument completion
-Non-numeric arguments to a command.
-Relevant commands are @code{enable} and @code{info}.
-
-@item Variable name completion
-Global variable names, and function arguments in the current context
-if the program is running. Relevant commands are
-@code{display},
-@code{print},
-@code{set},
-and
-@code{watch}.
-
-@end table
-
-@node Limitations
-@section Limitations
-
-@cindex debugger @subentry limitations
-We hope you find the @command{gawk} debugger useful and enjoyable to work with,
-but as with any program, especially in its early releases, it still has
-some limitations. A few that it's worth being aware of are:
-
-@itemize @value{BULLET}
-@item
-At this point, the debugger does not give a detailed explanation of
-what you did wrong when you type in something it doesn't like. Rather, it just
-responds @samp{syntax error}. When you do figure out what your mistake was,
-though, you'll feel like a real guru.
-
-@item
-@c NOTE: no comma after the ref{} on purpose, due to following
-@c parenthetical remark.
-If you perused the dump of opcodes in @ref{Miscellaneous Debugger Commands}
-(or if you are already familiar with @command{gawk} internals),
-you will realize that much of the internal manipulation of data
-in @command{gawk}, as in many interpreters, is done on a stack.
-@code{Op_push}, @code{Op_pop}, and the like are the ``bread and butter'' of
-most @command{gawk} code.
-
-Unfortunately, as of now, the @command{gawk}
-debugger does not allow you to examine the stack's contents.
-That is, the intermediate results of expression evaluation are on the
-stack, but cannot be printed. Rather, only variables that are defined
-in the program can be printed. Of course, a workaround for
-this is to use more explicit variables at the debugging stage and then
-change back to obscure, perhaps more optimal code later.
-
-@item
-There is no way to look ``inside'' the process of compiling
-regular expressions to see if you got it right. As an @command{awk}
-programmer, you are expected to know the meaning of
-@code{/[^[:alnum:][:blank:]]/}.
-
-@item
-The @command{gawk} debugger is designed to be used by running a program (with
all its
-parameters) on the command line, as described in @ref{Debugger Invocation}.
-There is no way (as of now) to attach or ``break into'' a running program.
-This seems reasonable for a language that is used mainly for quickly
-executing, short programs.
-
-@item
-The @command{gawk} debugger only accepts source code supplied with the
@option{-f} option.
-If you have a shell script that provides an @command{awk} program as a command
-line parameter, and you need to use the debugger, you can write the script
-to a temporary file, and use that as the program, with the @option{-f} option.
This
-might look like this:
-
-@example
-cat << \EOF > /tmp/script.$$
-@dots{} @ii{Your program here}
-EOF
-gawk -D -f /tmp/script.$$
-rm /tmp/script.$$
-@end example
-@end itemize
-
-@ignore
-@c 11/2016: This no longer applies after all the type cleanup work that's been
done.
-One other point is worth discussing. Conventional debuggers run in a
-separate process (and thus address space) from the programs that they
-debug (the @dfn{debuggee}, if you will).
-
-The @command{gawk} debugger is different; it is an integrated part
-of @command{gawk} itself. This makes it possible, in rare cases,
-for @command{gawk} to become an excellent demonstrator of Heisenberg
-Uncertainty physics, where the mere act of observing something can change
-it. Consider the following:@footnote{Thanks to Hermann Peifer for
-this example.}
-
-@example
-$ @kbd{cat test.awk}
-@print{} @{ print typeof($1), typeof($2) @}
-$ @kbd{cat test.data}
-@print{} abc 123
-$ @kbd{gawk -f test.awk test.data}
-@print{} strnum strnum
-@end example
-
-This is all as expected: field data has the STRNUM attribute
-(@pxref{Variable Typing}). Now watch what happens when we run
-this program under the debugger:
-
-@example
-$ @kbd{gawk -D -f test.awk test.data}
-gawk> @kbd{w $1} @ii{Set watchpoint on} $1
-@print{} Watchpoint 1: $1
-gawk> @kbd{w $2} @ii{Set watchpoint on} $2
-@print{} Watchpoint 2: $2
-gawk> @kbd{r} @ii{Start the program}
-@print{} Starting program:
-@print{} Stopping in Rule ...
-@print{} Watchpoint 1: $1 @ii{Watchpoint fires}
-@print{} Old value: ""
-@print{} New value: "abc"
-@print{} main() at `test.awk':1
-@print{} 1 @{ print typeof($1), typeof($2) @}
-gawk> @kbd{n} @ii{Keep going @dots{}}
-@print{} Watchpoint 2: $2 @ii{Watchpoint fires}
-@print{} Old value: ""
-@print{} New value: "123"
-@print{} main() at `test.awk':1
-@print{} 1 @{ print typeof($1), typeof($2) @}
-gawk> @kbd{n} @ii{Get result from} typeof()
-@print{} strnum number @ii{Result for} $2 @ii{isn't right}
-@print{} Program exited normally with exit value: 0
-gawk> @kbd{quit}
-@end example
-
-In this case, the act of comparing the new value of @code{$2}
-with the old one caused @command{gawk} to evaluate it and determine that it
-is indeed a number, and this is reflected in the result of
-@code{typeof()}.
-
-Cases like this where the debugger is not transparent to the program's
-execution should be rare. If you encounter one, please report it
-(@pxref{Bugs}).
-@end ignore
-
-@ignore
-Look forward to a future release when these and other missing features may
-be added, and of course feel free to try to add them yourself!
-@end ignore
-
-@node Debugging Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Programs rarely work correctly the first time. Finding bugs
-is called debugging, and a program that helps you find bugs is a
-debugger. @command{gawk} has a built-in debugger that works very
-similarly to the GNU Debugger, GDB.
-
-@item
-Debuggers let you step through your program one statement at a time,
-examine and change variable and array values, and do a number of other
-things that let you understand what your program is actually doing (as
-opposed to what it is supposed to do).
-
-@item
-Like most debuggers, the @command{gawk} debugger works in terms of stack
-frames, and lets you set both breakpoints (stop at a point in the code)
-and watchpoints (stop when a data value changes).
-
-@item
-The debugger command set is fairly complete, providing control over
-breakpoints, execution, viewing and changing data, working with the stack,
-getting information, and other tasks.
-
-@item
-If the GNU Readline library is available when @command{gawk} is
-compiled, it is used by the debugger to provide command-line history
-and editing.
-
-@item
-Usually, the debugger does not affect the
-program being debugged, but occasionally it can.
-
-@end itemize
-
-@hyphenation{name-space name-spaces Name-space Name-spaces}
-@node Namespaces
-@chapter Namespaces in @command{gawk}
-
-This @value{CHAPTER} describes a feature that is specific to @command{gawk}.
-
-@quotation CAUTION
-This feature described in this chapter is new. It is entirely
-possible, and even likely, that there are dark corners (if not bugs)
-still lurking within the implementation. If you find any such,
-please report them (@xref{Bugs}).
-@end quotation
-
-@menu
-* Global Namespace:: The global namespace in standard
- @command{awk}.
-* Qualified Names:: How to qualify names with a namespace.
-* Default Namespace:: The default namespace.
-* Changing The Namespace:: How to change the namespace.
-* Naming Rules:: Namespace and Component Naming Rules.
-* Internal Name Management:: How names are stored internally.
-* Namespace Example:: An example of code using a namespace.
-* Namespace And Features:: Namespaces and other @command{gawk} features.
-* Namespace Summary:: Summarizing namespaces.
-@end menu
-
-@node Global Namespace
-@section Standard @command{awk}'s Single Namespace
-
-@cindex namespace @subentry definition of
-@cindex namespace @subentry standard @command{awk}, global
-In standard @command{awk}, there is a single, global, @dfn{namespace}.
-This means that @emph{all} function names and global variable names must
-be unique. For example, two different @command{awk} source files cannot
-both define a function named @code{min()}, or define the same identifier,
-used as a scalar in one and as an array in the other.
-
-This situation is okay when programs are small, say a few hundred
-lines, or even a few thousand, but it prevents the development of
-reusable libraries of @command{awk} functions, and can inadvertently
-cause independently-developed library files to accidentally step on each
-other's ``private'' global variables
-(@pxref{Library Names}).
-
-@cindex package, definition of
-@cindex module, definition of
-Most other programming languages solve this issue by providing some kind
-of namespace control: a way to say ``this function is in namespace @var{xxx},
-and that function is in namespace @var{yyy}.'' (Of course, there is then
-still a single namespace for the namespaces, but the hope is that there
-are much fewer namespaces in use by any given program, and thus much
-less chance for collisions.) These facilities are sometimes referred
-to as @dfn{packages} or @dfn{modules}.
-
-Starting with @value{PVERSION} 5.0, @command{gawk} provides a
-simple mechanism to put functions and global variables into separate
namespaces.
-
-@node Qualified Names
-@section Qualified Names
-
-@cindex qualified name @subentry definition of
-@cindex namespaces @subentry qualified names
-@cindex @code{:} (colon) @subentry @code{::} namespace separator
-@cindex colon (@code{:}) @subentry @code{::} namespace separator
-@cindex component name
-A @dfn{qualified name} is an identifier that includes a namespace name,
-the namespace separator @code{::}, and a @dfn{component} name. For example,
one
-might have a function named @code{posix::getpid()}. Here, the namespace
-is @code{posix} and the function name within the namespace (the component)
-is @code{getpid()}. The namespace and component names are separated by
-a double-colon. Only one such separator is allowed in a qualified name.
-
-@quotation NOTE
-Unlike C++, the @code{::} is @emph{not} an operator. No spaces are
-allowed between the namespace name, the @code{::}, and the component name.
-@end quotation
-
-@cindex qualified name @subentry use of
-You must use qualified names from one namespace to access variables
-and functions in another. This is especially important when using
-variable names to index the special @code{SYMTAB} array (@pxref{Auto-set}),
-and when making indirect function calls (@pxref{Indirect Calls}).
-
-@node Default Namespace
-@section The Default Namespace
-
-@cindex namespace @subentry default
-@cindex namespace @subentry @code{awk}
-@cindex @code{awk} @subentry namespace
-The default namespace, not surprisingly, is @code{awk}.
-All of the predefined @command{awk} and @command{gawk} variables
-are in this namespace, and thus have qualified names like
-@code{awk::ARGC}, @code{awk::NF}, and so on.
-
-@cindex uppercase names, namespace for
-Furthermore, even when you have changed the namespace for your
-current source file (@pxref{Changing The Namespace}), @command{gawk}
-forces unqualified identifiers whose names are all uppercase letters
-to be in the @code{awk} namespace. This makes it possible for you to easily
-reference @command{gawk}'s global variables from different namespaces.
-It also keeps your code looking natural.
-
-@node Changing The Namespace
-@section Changing The Namespace
-
-@cindex namespaces @subentry changing
-@cindex @code{@@} (at-sign) @subentry @code{@@namespace} directive
-@cindex at-sign (@code{@@}) @subentry @code{@@namespace} directive
-@cindex @code{@@namespace} directive @sortas{namespace directive}
-In order to set the current namespace, use an @code{@@namespace} directive
-at the top level of your program:
-
-@example
-@@namespace "passwd"
-
-BEGIN @{ @dots{} @}
-@dots{}
-@end example
-
-After this directive, all simple non-completely-uppercase identifiers are
-placed into the @code{passwd} namespace.
-
-You can change the namespace multiple times within a single
-source file, although this is likely to become confusing if you
-do it too much.
-
-@quotation NOTE
-Association of unqualified identifiers to a namespace is handled while
-@command{gawk} parses your program, @emph{before} it starts to run. There is
-no concept of a ``current'' namespace once your program starts executing.
-Be sure you understand this.
-@end quotation
-
-@cindex namespace @subentry implicit
-@cindex implicit namespace
-Each source file for @option{-i} and @option{-f} starts out with
-an implicit @samp{@@namespace "awk"}. Similarly, each chunk of
-command-line code supplied with @option{-e} has such an implicit
-initial statement (@pxref{Options}).
-
-@cindex current namespace, pushing and popping
-@cindex namespace @subentry pushing and popping
-Files included with @code{@@include} (@pxref{Include Files}) ``push''
-and ``pop'' the current namespace. That is, each @code{@@include} saves
-the current namespace and starts over with an implicit @samp{@@namespace
-"awk"} which remains in effect until an explicit @code{@@namespace}
-directive is seen. When @command{gawk} finishes processing the included
-file, the saved namespace is restored and processing continues where it
-left off in the original file.
-
-@cindex @code{@@} (at-sign) @subentry @code{@@namespace} directive @subentry
@code{BEGIN}, @code{BEGINFILE}, @code{END}, @code{ENDFILE} and
-@cindex at-sign (@code{@@}) @subentry @code{@@namespace} directive @subentry
@code{BEGIN}, @code{BEGINFILE}, @code{END}, @code{ENDFILE} and
-@cindex @code{BEGIN} pattern @subentry @code{@@namespace} directive and
-@cindex @code{BEGINFILE} pattern @subentry @code{@@namespace} directive and
-@cindex @code{END} pattern @subentry @code{@@namespace} directive and
-@cindex @code{ENDFILE} pattern @subentry @code{@@namespace} directive and
-@cindex @code{@@namespace} directive @sortas{namespace directive}
-The use of @code{@@namespace} has no influence upon the order of execution
-of @code{BEGIN}, @code{BEGINFILE}, @code{END}, and @code{ENDFILE} rules.
-
-@node Naming Rules
-@section Namespace and Component Naming Rules
-
-@cindex naming rules, namespace and component names
-@cindex namespaces @subentry naming rules
-@c not "component names" to merge with other index entry
-@cindex component name @subentry naming rules
-A number of rules apply to the namespace and component names, as follows.
-
-@itemize @bullet
-@item
-It is a syntax error to use qualified names for function parameter names.
-
-@item
-It is a syntax error to use any standard @command{awk} reserved word (such
-as @code{if} or @code{for}), or the name of any standard built-in function
-(such as @code{sin()} or @code{gsub()}) as either part of a qualified name.
-Thus, the following produces a syntax error:
-
-@example
-@@namespace "example"
-
-function gsub(str, pat, result) @{ @dots{} @}
-@end example
-
-@item
-Outside the @code{awk} namespace, the names of the additional @command{gawk}
-built-in functions (such as @code{gensub()} or @code{strftime()}) @emph{may}
-be used as component names. The same set of names may be used as namespace
-names, although this has the potential to be confusing.
-
-@item
-The additional @command{gawk} built-in functions may still be called
-from outside the @code{awk} namespace by qualifying them. For example,
-@code{awk::systime()}. Here is a somewhat silly example demonstrating
-this rule and the previous one:
-
-@example
-BEGIN @{
- print "in awk namespace, systime() =", systime()
-@}
-
-@@namespace "testing"
-
-function systime()
-@{
- print "in testing namespace, systime() =", awk::systime()
-@}
-
-BEGIN @{
- systime()
-@}
-@end example
-
-@noindent
-
-When run, it produces output like this:
-
-@example
-$ @kbd{gawk -f systime.awk}
-@print{} in awk namespace, systime() = 1500488503
-@print{} in testing namespace, systime() = 1500488503
-@end example
-
-@item
-@command{gawk} pre-defined variable names may be used:
-@code{NF::NR} is valid, if possibly not all that useful.
-@end itemize
-
-@node Internal Name Management
-@section Internal Name Management
-
-@cindex name management
-@cindex @code{awk} @subentry namespace @subentry identifier name storage
-@cindex @code{awk} @subentry namespace @subentry use for indirect function
calls
-For backwards compatibility, all identifiers in the @code{awk} namespace
-are stored internally as unadorned identifiers (that is, without a
-leading @samp{awk::}). This is mainly relevant
-when using such identifiers as indices for @code{SYMTAB}, @code{FUNCTAB},
-and @code{PROCINFO["identifiers"]} (@pxref{Auto-set}), and for use in
-indirect function calls (@pxref{Indirect Calls}).
-
-In program code, to refer to variables and functions in the @code{awk}
-namespace from another namespace, you must still use the @samp{awk::}
-prefix. For example:
-
-@example
-@@namespace "awk" @ii{This is the default namespace}
-
-BEGIN @{
- Title = "My Report" @ii{Qualified name is} awk::Title
-@}
-
-@@namespace "report" @ii{Now in} report @ii{namespace}
-
-function compute() @ii{This is really} report::compute()
-@{
- print awk::Title @ii{But would be} SYMTAB["Title"]
- @dots{}
-@}
-@end example
-
-@node Namespace Example
-@section Namespace Example
-
-@cindex namespace @subentry example code
-The following example is a revised version of the suite of routines
-developed in @ref{Passwd Functions}. See there for an explanation
-of how the code works.
-
-The formulation here, due mainly to Andrew Schorr, is rather elegant.
-All of the implementation functions and variables are in the
-@code{passwd} namespace, whereas the main interface functions are
-defined in the @code{awk} namespace.
-
-@example
-@c file eg/lib/ns_passwd.awk
-# ns_passwd.awk --- access password file information
-@c endfile
-@ignore
-@c file eg/lib/ns_passwd.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# May 1993
-# Revised October 2000
-# Revised December 2010
-#
-# Reworked for namespaces June 2017, with help from
-# Andrew J.@: Schorr, aschorr@@telemetry-investments.com
-@c endfile
-@end ignore
-@c file eg/lib/ns_passwd.awk
-
-@@namespace "passwd"
-
-BEGIN @{
- # tailor this to suit your system
- Awklib = "/usr/local/libexec/awk/"
-@}
-
-function Init( oldfs, oldrs, olddol0, pwcat, using_fw, using_fpat)
-@{
- if (Inited)
- return
-
- oldfs = FS
- oldrs = RS
- olddol0 = $0
- using_fw = (PROCINFO["FS"] == "FIELDWIDTHS")
- using_fpat = (PROCINFO["FS"] == "FPAT")
- FS = ":"
- RS = "\n"
-
- pwcat = Awklib "pwcat"
- while ((pwcat | getline) > 0) @{
- Byname[$1] = $0
- Byuid[$3] = $0
- Bycount[++Total] = $0
- @}
- close(pwcat)
- Count = 0
- Inited = 1
- FS = oldfs
- if (using_fw)
- FIELDWIDTHS = FIELDWIDTHS
- else if (using_fpat)
- FPAT = FPAT
- RS = oldrs
- $0 = olddol0
-@}
-
-function awk::getpwnam(name)
-@{
- Init()
- return Byname[name]
-@}
-
-function awk::getpwuid(uid)
-@{
- Init()
- return Byuid[uid]
-@}
-
-function awk::getpwent()
-@{
- Init()
- if (Count < Total)
- return Bycount[++Count]
- return ""
-@}
-
-function awk::endpwent()
-@{
- Count = 0
-@}
-@c endfile
-@end example
-
-As you can see, this version also follows the convention mentioned in
-@ref{Library Names}, whereby global variable and function names
-start with a capital letter.
-
-Here is a simple test program. Since it's in a separate file, unadorned
-identifiers are sought for in the @code{awk} namespace:
-
-@example
-BEGIN @{
- while ((p = getpwent()) != "")
- print p
-@}
-@end example
-
-@noindent
-
-Here's what happens when it's run:
-
-@example
-$ @kbd{gawk -f ns_passwd.awk -f testpasswd.awk}
-@print{} root:x:0:0:root:/root:/bin/bash
-@print{} daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
-@print{} bin:x:2:2:bin:/bin:/usr/sbin/nologin
-@print{} sys:x:3:3:sys:/dev:/usr/sbin/nologin
-@dots{}
-@end example
-
-@node Namespace And Features
-@section Namespaces and Other @command{gawk} Features
-
-This @value{SECTION} looks briefly at how the namespace facility interacts
-with other important @command{gawk} features.
-
-@cindex namespaces @subentry interaction with @subentry profiler
-@cindex namespaces @subentry interaction with @subentry pretty printer
-@cindex profiler, interaction with namespaces
-@cindex pretty printer, interaction with namespaces
-The profiler and pretty-printer (@pxref{Profiling}) have been enhanced
-to understand namespaces and the namespace naming rules presented in
-@ref{Naming Rules}. In particular, the output groups functions in the same
-namespace together, and has @code{@@namespace} directives in front
-of rules as necessary. This allows component names to be
-simple identifiers, instead of using qualified identifiers everywhere.
-
-@cindex namespaces @subentry interaction with @subentry debugger
-@cindex debugger @subentry interaction with namespaces
-Interaction with the debugger (@pxref{Debugging}) has not had to change
-(at least as of this writing). Some of the internal byte codes changed
-in order to accommodate namespaces, and the debugger's @code{dump} command
-was adjusted to match.
-
-@cindex namespaces @subentry interaction with @subentry extension API
-@cindex extension API @subentry interaction with namespaces
-The extension API (@pxref{Dynamic Extensions}) has always allowed for
-placing functions into a different namespace, although this was not
-previously implemented. However, the symbol lookup and symbol update
-routines did not have provision for including a namespace. That has now
-been corrected (@pxref{Symbol table by name}).
-@xref{Extension Sample Inplace}, for a nice example of an extension that
-leverages a namespace shared by cooperating @command{awk} and C code.
-
-@node Namespace Summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Standard @command{awk} provides a single namespace for all global
-identifiers (scalars, arrays, and functions). This is limiting when
-one wants to develop libraries of reusable functions or function suites.
-
-@item
-@command{gawk} provides multiple namespaces by using qualified names:
-names consisting of a namespace name, a double colon, @code{::}, and a
-component name. Namespace names might still possibly conflict, but this
-is true of any language providing namespaces, modules, or packages.
-
-@item
-The default namespace is @command{awk}. The rules for namespace and
-component names are provided in @ref{Naming Rules}. The rules are
-designed in such a way as to make namespace-aware code continue to
-look and work naturally while still providing the necessary power and
-flexibility.
-
-@item
-Other parts of @command{gawk} have been extended as necessary to integrate
-namespaces smoothly with their operation. This applies most notably to
-the profiler / pretty-printer (@pxref{Profiling}) and to the extension
-facility (@pxref{Dynamic Extensions}).
-
-@cindex namespaces @subentry backwards compatibility
-@item
-Overall, the namespace facility was designed and implemented such that
-backwards compatibility is paramount. Programs that don't use namespaces
-should see absolutely no difference in behavior when run by a namespace-capable
-version of @command{gawk}.
-@end itemize
-
-@node Arbitrary Precision Arithmetic
-@chapter Arithmetic and Arbitrary-Precision Arithmetic with @command{gawk}
-@cindex arbitrary precision
-@cindex multiple precision
-@cindex infinite precision
-@cindex floating-point @subentry numbers @subentry arbitrary-precision
-
-This @value{CHAPTER} introduces some basic concepts relating to
-how computers do arithmetic and defines some important terms.
-It then proceeds to describe floating-point arithmetic,
-which is what @command{awk} uses for all its computations, including a
-discussion of arbitrary-precision floating-point arithmetic, which is
-a feature available only in @command{gawk}. It continues on to present
-arbitrary-precision integers, and concludes with a description of some
-points where @command{gawk} and the POSIX standard are not quite in
-agreement.
-
-@quotation NOTE
-Most users of @command{gawk} can safely skip this chapter.
-But if you want to do scientific calculations with @command{gawk},
-this is the place to be.
-@end quotation
-
-@menu
-* Computer Arithmetic:: A quick intro to computer math.
-* Math Definitions:: Defining terms used.
-* MPFR features:: The MPFR features in @command{gawk}.
-* FP Math Caution:: Things to know.
-* Arbitrary Precision Integers:: Arbitrary Precision Integer Arithmetic with
- @command{gawk}.
-* Checking for MPFR:: How to check if MPFR is available.
-* POSIX Floating Point Problems:: Standards Versus Existing Practice.
-* Floating point summary:: Summary of floating point discussion.
-@end menu
-
-@node Computer Arithmetic
-@section A General Description of Computer Arithmetic
-
-Until now, we have worked with data as either numbers or
-strings. Ultimately, however, computers represent everything in terms
-of @dfn{binary digits}, or @dfn{bits}. A decimal digit can take on any
-of 10 values: zero through nine. A binary digit can take on any of two
-values, zero or one. Using binary, computers (and computer software)
-can represent and manipulate numerical and character data. In general,
-the more bits you can use to represent a particular thing, the greater
-the range of possible values it can take on.
-
-Modern computers support at least two, and often more, ways to do
-arithmetic. Each kind of arithmetic uses a different representation
-(organization of the bits) for the numbers. The kinds of arithmetic
-that interest us are:
-
-@table @asis
-@item Decimal arithmetic
-This is the kind of arithmetic you learned in elementary school, using
-paper and pencil (and/or a calculator). In theory, numbers can have an
-arbitrary number of digits on either side (or both sides) of the decimal
-point, and the results of a computation are always exact.
-
-Some modern systems can do decimal arithmetic in hardware, but usually you
-need a special software library to provide access to these instructions.
-There are also libraries that do decimal arithmetic entirely in software.
-
-Despite the fact that some users expect @command{gawk} to be performing
-decimal arithmetic,@footnote{We don't know why they expect this, but
-they do.} it does not do so.
-
-@item Integer arithmetic
-In school, integer values were referred to as ``whole'' numbers---that
-is, numbers without any fractional part, such as 1, 42, or @minus{}17.
-The advantage to integer numbers is that they represent values exactly.
-The disadvantage is that their range is limited.
-
-@cindex unsigned integers
-@cindex integers @subentry unsigned
-In computers, integer values come in two flavors: @dfn{signed} and
-@dfn{unsigned}. Signed values may be negative or positive, whereas
-unsigned values are always greater than or equal
-to zero.
-
-In computer systems, integer arithmetic is exact, but the possible
-range of values is limited. Integer arithmetic is generally faster than
-floating-point arithmetic.
-
-@cindex floating-point @subentry numbers
-@item Floating-point arithmetic
-Floating-point numbers represent what were called in school ``real''
-numbers (i.e., those that have a fractional part, such as 3.1415927).
-The advantage to floating-point numbers is that they can represent a
-much larger range of values than can integers. The disadvantage is that
-there are numbers that they cannot represent exactly.
-
-Modern systems support floating-point arithmetic in hardware, with a
-limited range of values. There are software libraries that allow
-the use of arbitrary-precision floating-point calculations.
-
-@cindex floating-point @subentry numbers @subentry single-precision
-@cindex floating-point @subentry numbers @subentry double-precision
-@cindex floating-point @subentry numbers @subentry arbitrary-precision
-@cindex single-precision
-@cindex double-precision
-@cindex arbitrary precision
-POSIX @command{awk} uses @dfn{double-precision} floating-point numbers, which
-can hold more digits than @dfn{single-precision} floating-point numbers.
-@command{gawk} has facilities for performing arbitrary-precision
-floating-point arithmetic, which we describe in more detail shortly.
-@end table
-
-Computers work with integer and floating-point values of different
-ranges. Integer values are usually either 32 or 64 bits in size.
-Single-precision floating-point values occupy 32 bits, whereas double-precision
-floating-point values occupy 64 bits.
-(Quadruple-precision floating point values also exist. They occupy 128 bits,
-but such numbers are not available in @command{awk}.)
-Floating-point values are always
-signed. The possible ranges of values are shown in @ref{table-numeric-ranges}
-and @ref{table-floating-point-ranges}.
-
-@float Table,table-numeric-ranges
-@caption{Value ranges for integer representations}
-@multitable @columnfractions .34 .33 .33
-@headitem Representation @tab Minimum value @tab Maximum value
-@item 32-bit signed integer @tab @minus{}2,147,483,648 @tab 2,147,483,647
-@item 32-bit unsigned integer @tab 0 @tab 4,294,967,295
-@item 64-bit signed integer @tab @minus{}9,223,372,036,854,775,808 @tab
9,223,372,036,854,775,807
-@item 64-bit unsigned integer @tab 0 @tab 18,446,744,073,709,551,615
-@end multitable
-@end float
-
-@float Table,table-floating-point-ranges
-@caption{Approximate value ranges for floating-point number representations}
-@multitable @columnfractions .38 .22 .22 .23
-@iftex
-@headitem Representation @tab @w{Minimum positive} @w{nonzero value} @tab
Minimum @w{finite value} @tab Maximum @w{finite value}
-@end iftex
-@ifnottex
-@headitem Representation @tab Minimum positive nonzero value @tab Minimum
finite value @tab Maximum finite value
-@end ifnottex
-@iftex
-@item @w{Single-precision floating-point} @tab @math{1.175494 @cdot 10^{-38}}
@tab @math{-3.402823 @cdot 10^{38}} @tab @math{3.402823 @cdot 10^{38}}
-@item @w{Double-precision floating-point} @tab @math{2.225074 @cdot 10^{-308}}
@tab @math{-1.797693 @cdot 10^{308}} @tab @math{1.797693 @cdot 10^{308}}
-@item @w{Quadruple-precision floating-point} @tab @math{3.362103 @cdot
10^{-4932}} @tab @math{-1.189731 @cdot 10^{4932}} @tab @math{1.189731 @cdot
10^{4932}}
-@end iftex
-@ifinfo
-@item Single-precision floating-point @tab 1.175494e-38 @tab -3.402823e+38
@tab 3.402823e+38
-@item Double-precision floating-point @tab 2.225074e-308 @tab -1.797693e+308
@tab 1.797693e+308
-@item Quadruple-precision floating-point @tab 3.362103e-4932 @tab
-1.189731e+4932 @tab 1.189731e+4932
-@end ifinfo
-@ifnottex
-@ifnotinfo
-@item Single-precision floating-point @tab 1.175494*10@sup{-38} @tab
-3.402823*10@sup{38} @tab 3.402823*10@sup{38}
-@item Double-precision floating-point @tab 2.225074*10@sup{-308} @tab
-1.797693*10@sup{308} @tab 1.797693*10@sup{308}
-@item Quadruple-precision floating-point @tab 3.362103*10@sup{-4932} @tab
-1.189731*10@sup{4932} @tab 1.189731*10@sup{4932}
-@end ifnotinfo
-@end ifnottex
-@end multitable
-@end float
-
-@node Math Definitions
-@section Other Stuff to Know
-
-The rest of this @value{CHAPTER} uses a number of terms. Here are some
-informal definitions that should help you work your way through the material
-here:
-
-@table @dfn
-@item Accuracy
-A floating-point calculation's accuracy is how close it comes
-to the real (paper and pencil) value.
-
-@item Error
-The difference between what the result of a computation ``should be''
-and what it actually is. It is best to minimize error as much
-as possible.
-
-@item Exponent
-The order of magnitude of a value;
-some number of bits in a floating-point value store the exponent.
-
-@item Inf
-A special value representing infinity. Operations involving another
-number and infinity produce infinity.
-
-@item NaN
-``Not a number.'' A special value that results from attempting a
-calculation that has no answer as a real number. @xref{Strange values},
-for more information about infinity and not-a-number values.
-
-@item Normalized
-How the significand (see later in this list) is usually stored. The
-value is adjusted so that the first bit is one, and then that leading
-one is assumed instead of physically stored. This provides one
-extra bit of precision.
-
-@item Precision
-The number of bits used to represent a floating-point number.
-The more bits, the more digits you can represent.
-Binary and decimal precisions are related approximately, according to the
-formula:
-
-@display
-@iftex
-@math{prec = 3.322 @cdot dps}
-@end iftex
-@ifnottex
-@ifnotdocbook
-@var{prec} = 3.322 * @var{dps}
-@end ifnotdocbook
-@end ifnottex
-@docbook
-<emphasis>prec</emphasis> = 3.322 ⋅ <emphasis>dps</emphasis>
-@end docbook
-@end display
-
-@noindent
-Here, @emph{prec} denotes the binary precision
-(measured in bits) and @emph{dps} (short for decimal places)
-is the decimal digits.
-
-@item Rounding mode
-How numbers are rounded up or down when necessary.
-More details are provided later.
-
-@item Significand
-A floating-point value consists of the significand multiplied by 10
-to the power of the exponent. For example, in @code{1.2345e67},
-the significand is @code{1.2345}.
-
-@item Stability
-From @uref{https://en.wikipedia.org/wiki/Numerical_stability,
-the Wikipedia article on numerical stability}:
-``Calculations that can be proven not to magnify approximation errors
-are called @dfn{numerically stable}.''
-@end table
-
-See @uref{https://en.wikipedia.org/wiki/Accuracy_and_precision,
-the Wikipedia article on accuracy and precision} for more information
-on some of those terms.
-
-On modern systems, floating-point hardware uses the representation and
-operations defined by the IEEE 754 standard.
-Three of the standard IEEE 754 types are 32-bit single precision,
-64-bit double precision, and 128-bit quadruple precision.
-The standard also specifies extended precision formats
-to allow greater precisions and larger exponent ranges.
-(@command{awk} uses only the 64-bit double-precision format.)
-
-@ref{table-ieee-formats} lists the precision and exponent
-field values for the basic IEEE 754 binary formats.
-
-@float Table,table-ieee-formats
-@caption{Basic IEEE format values}
-@multitable @columnfractions .20 .20 .20 .20 .20
-@headitem Name @tab Total bits @tab Precision @tab Minimum exponent @tab
Maximum exponent
-@item Single @tab 32 @tab 24 @tab @minus{}126 @tab +127
-@item Double @tab 64 @tab 53 @tab @minus{}1022 @tab +1023
-@item Quadruple @tab 128 @tab 113 @tab @minus{}16382 @tab +16383
-@end multitable
-@end float
-
-@quotation NOTE
-The precision numbers include the implied leading one that gives them
-one extra bit of significand.
-@end quotation
-
-@node MPFR features
-@section Arbitrary-Precision Arithmetic Features in @command{gawk}
-
-This @value{SECTION} briefly describes arbitrary-precision
-arithmetic in @command{gawk}.
-
-@menu
-* MPFR On Parole:: MPFR features are on parole!
-* MPFR Intro:: MPFR General introduction.
-@end menu
-
-@node MPFR On Parole
-@subsection Arbitrary Precision Arithmetic is On Parole!
-
-As of @value{PVERSION} 5.2,
-arbitrary precision arithmetic in @command{gawk}
-is ``on parole.'' The primary @command{gawk} maintainer is no
-longer maintaining it. Fortunately, a volunteer from the development
-team has agreed to take it over.
-
-This feature is on parole because its inclusion was a mistake. It has
-led to endless bug reports, misuse of the feature and public abuse of the
-maintainer, for no real increased value.
-
-@ignore
-If you use this feature, you should start working now to find a different
-toolset with which to accomplish your goals.@footnote{Of course, you can
-always continue to use a version of @command{gawk} that still supports
-arbitrary precision arithmetic. It simply will be unmaintained.}
-
-If the feature is very important to you, then consider if you are willing
-to volunteer to maintain it, so that it can continue to be included
-in @command{gawk}. If that is the case, contact the maintainer to discuss it
-with him. You may do so by submitting a bug report.
-@end ignore
-
-If the situation with support changes, the feature will be removed
-from @command{gawk}.
-
-If you use this feature, you should consider finding a different
-toolset with which to accomplish your goals.@footnote{Of course, you can
-always continue to use a version of @command{gawk} that still supports
-arbitrary precision arithmetic. It simply will be unmaintained.}
-
-@node MPFR Intro
-@subsection Arbitrary Precision Introduction
-
-By default, @command{gawk} uses the double-precision floating-point values
-supplied by the hardware of the system it runs on. However, if it was
-compiled to do so, and the @option{-M} command-line option is supplied,
-@command{gawk} uses the @uref{http://www.mpfr.org,
-GNU MPFR} and @uref{https://gmplib.org, GNU MP} (GMP) libraries for
-arbitrary-precision arithmetic on numbers. You can see if MPFR support
-is available like so:
-
-@example
-$ @kbd{gawk --version}
-@print{} GNU Awk 5.2.1, API 3.2, PMA Avon 8-g1, (GNU MPFR 4.1.0, GNU MP 6.2.1)
-@print{} Copyright (C) 1989, 1991-2022 Free Software Foundation.
-@dots{}
-@end example
-
-@noindent
-(You may see different version numbers than what's shown here. That's OK;
-what's important is to see that GNU MPFR and GNU MP are listed in
-the output.)
-
-Additionally, there are a few elements available in the @code{PROCINFO}
-array to provide information about the MPFR and GMP libraries
-(@pxref{Auto-set}).
-
-The MPFR library provides precise control over precisions and rounding
-modes, and gives correctly rounded, reproducible, platform-independent
-results. With the @option{-M} command-line option,
-all floating-point arithmetic operators and numeric functions
-can yield results to any desired precision level supported by MPFR.
-
-Two predefined variables, @code{PREC} and @code{ROUNDMODE},
-provide control over the working precision and the rounding mode.
-The precision and the rounding mode are set globally for every operation
-to follow.
-@xref{Setting precision} and @ref{Setting the rounding mode}
-for more information.
-
-@node FP Math Caution
-@section Floating-Point Arithmetic: Caveat Emptor!
-
-@quotation
-@i{Math class is tough!}
-@author Teen Talk Barbie, July 1992
-@end quotation
-
-This @value{SECTION} provides a high-level overview of the issues
-involved when doing lots of floating-point arithmetic.@footnote{There
-is a very nice @uref{http://www.validlab.com/goldberg/paper.pdf,
-paper on floating-point arithmetic} by David Goldberg, ``What Every
-Computer Scientist Should Know About Floating-Point Arithmetic,''
-@cite{ACM Computing Surveys} @strong{23}, 1 (1991-03): 5-48. This is
-worth reading if you are interested in the details, but it does require
-a background in computer science.}
-The discussion applies to both hardware and arbitrary-precision
-floating-point arithmetic.
-
-@quotation CAUTION
-The material here is purposely general. If you need to do serious
-computer arithmetic, you should do some research first, and not
-rely just on what we tell you.
-@end quotation
-
-@menu
-* Inexactness of computations:: Floating point math is not exact.
-* Getting Accuracy:: Getting more accuracy takes some work.
-* Try To Round:: Add digits and round.
-* Setting precision:: How to set the precision.
-* Setting the rounding mode:: How to set the rounding mode.
-@end menu
-
-@node Inexactness of computations
-@subsection Floating-Point Arithmetic Is Not Exact
-
-Binary floating-point representations and arithmetic are inexact.
-Simple values like 0.1 cannot be precisely represented using
-binary floating-point numbers, and the limited precision of
-floating-point numbers means that slight changes in
-the order of operations or the precision of intermediate storage
-can change the result. To make matters worse, with arbitrary-precision
-floating-point arithmetic, you can set the precision before starting a
-computation, but then you cannot be sure of the number of significant
-decimal places in the final result.
-
-@menu
-* Inexact representation:: Numbers are not exactly represented.
-* Comparing FP Values:: How to compare floating point values.
-* Errors accumulate:: Errors get bigger as they go.
-* Strange values:: A few words about infinities and NaNs.
-@end menu
-
-@node Inexact representation
-@subsubsection Many Numbers Cannot Be Represented Exactly
-
-So, before you start to write any code, you should think
-about what you really want and what's really happening. Consider the
-two numbers in the following example:
-
-@example
-x = 0.875 # 1/2 + 1/4 + 1/8
-y = 0.425
-@end example
-
-Unlike the number in @code{y}, the number stored in @code{x}
-is exactly representable
-in binary because it can be written as a finite sum of one or
-more fractions whose denominators are all powers of two.
-When @command{gawk} reads a floating-point number from
-program source, it automatically rounds that number to whatever
-precision your machine supports. If you try to print the numeric
-content of a variable using an output format string of @code{"%.17g"},
-it may not produce the same number as you assigned to it:
-
-@example
-$ @kbd{gawk 'BEGIN @{ x = 0.875; y = 0.425}
-> @kbd{ printf("%0.17g, %0.17g\n", x, y) @}'}
-@print{} 0.875, 0.42499999999999999
-@end example
-
-Often the error is so small you do not even notice it, and if you do,
-you can always specify how much precision you would like in your output.
-Usually this is a format string like @code{"%.15g"}, which, when
-used in the previous example, produces an output identical to the input.
-
-@node Comparing FP Values
-@subsubsection Be Careful Comparing Values
-
-Because the underlying representation can be a little bit off from the exact
value,
-comparing floating-point values to see if they are exactly equal is generally
a bad idea.
-Here is an example where it does not work like you would expect:
-
-@example
-$ @kbd{gawk 'BEGIN @{ print (0.1 + 12.2 == 12.3) @}'}
-@print{} 0
-@end example
-
-The general wisdom when comparing floating-point values is to see if
-they are within some small range of each other (called a @dfn{delta},
-or @dfn{tolerance}).
-You have to decide how small a delta is important to you. Code to do
-this looks something like the following:
-
-@example
-@group
-delta = 0.00001 # for example
-difference = abs(a - b) # subtract the two values
-if (difference < delta)
- # all ok
-else
- # not ok
-@end group
-@end example
-
-@noindent
-(We assume that you have a simple absolute value function named
-@code{abs()} defined elsewhere in your program.) If you write a
-function to compare values with a delta, you should be sure
-to use @samp{difference < abs(delta)} in case someone passes
-in a negative delta value.
-
-@node Errors accumulate
-@subsubsection Errors Accumulate
-
-The loss of accuracy during a single computation with floating-point
-numbers usually isn't enough to worry about. However, if you compute a
-value that is the result of a sequence of floating-point operations,
-the error can accumulate and greatly affect the computation itself.
-Here is an attempt to compute the value of @value{PI} using one of its
-many series representations:
-
-@example
-BEGIN @{
- x = 1.0 / sqrt(3.0)
- n = 6
- for (i = 1; i < 30; i++) @{
- n = n * 2.0
- x = (sqrt(x * x + 1) - 1) / x
- printf("%.15f\n", n * x)
- @}
-@}
-@end example
-
-When run, the early errors propagate through later computations,
-causing the loop to terminate prematurely after attempting to divide by zero:
-
-@example
-$ @kbd{gawk -f pi.awk}
-@print{} 3.215390309173475
-@print{} 3.159659942097510
-@print{} 3.146086215131467
-@print{} 3.142714599645573
-@dots{}
-@print{} 3.224515243534819
-@print{} 2.791117213058638
-@print{} 0.000000000000000
-@error{} gawk: pi.awk:6: fatal: division by zero attempted
-@end example
-
-Here is an additional example where the inaccuracies in internal
representations
-yield an unexpected result:
-
-@example
-$ @kbd{gawk 'BEGIN @{}
-> @kbd{for (d = 1.1; d <= 1.5; d += 0.1) # loop five times (?)}
-> @kbd{i++}
-> @kbd{print i}
-> @kbd{@}'}
-@print{} 4
-@end example
-
-@node Strange values
-@subsubsection Floating Point Values They Didn't Talk About In School
-
-Both IEEE 754 floating-point hardware, and MPFR, support two kinds of
-values that you probably didn't learn about in school. The first is
-@dfn{infinity}, a special value, that can be either negative or positive,
-and which is either smaller than any other value (negative infinity),
-or larger than any other value (positive infinity). When such values
-are generated, @command{gawk} prints them as either @samp{-inf} or
-@samp{+inf}, respectively. It accepts those strings as data input and
-converts them to the proper floating-point values internally.
-
-Infinity values of the same sign compare as equal to each other.
-Otherwise, operations (addition, subtraction, etc.) involving another
-number and infinity produce mathematically reasonable results.
-
-The second kind of value is ``not a number'', or NaN for
-short.@footnote{Thanks to Michael Brennan for this description, which we
-have paraphrased, and for the examples.} This is a special value that results
-from attempting a calculation that has no answer as a real number.
-In such a case, programs can either receive a floating-point exception,
-or get NaN back as the result. The IEEE 754 standard recommends
-that systems return NaN. Some examples:
-
-@table @code
-@item sqrt(-1)
-@iftex
-The @math{\sqrt{-1}}
-@end iftex
-@ifnottex
-This
-@end ifnottex
-makes sense in the range of complex numbers, but not in the
-range of real numbers, so the result is NaN.
-
-@item log(-8)
-@minus{}8 is out of the domain of @code{log()}, so the result is NaN.
-@end table
-
-NaN values are strange. In particular, they cannot be compared with other
-floating point values; any such comparison, except for ``is not equal
-to'', returns false. NaN values are so much unequal to other values that
-even comparing two identical NaN values with @code{!=} returns true!
-
-NaN values can also be signed, although it depends upon the implementation
-as to which sign you get for any operation that returns a NaN. For
-example, on some systems, @code{sqrt(-1)} returns a negative NaN. On
-others, it returns a positive NaN.
-
-When such values are generated, @command{gawk} prints them as either
-@samp{-nan} or @samp{+nan}, respectively. Here too, @command{gawk}
-accepts those strings as data input and converts them to the proper
-floating-point values internally.
-
-If you want to dive more deeply into this topic, you can find
-test programs in C, @command{awk} and Python in the directory
-@file{awklib/eg/test-programs} in the @command{gawk} distribution.
-These programs enable comparison among programming languages as to how
-they handle NaN and infinity values.
-
-@ignore
-@c file eg/test-programs/gen-float-table.awk
-function eq(left, right)
-@{
- return left == right
-@}
-
-function ne(left, right)
-@{
- return left != right
-@}
-
-function lt(left, right)
-@{
- return left < right
-@}
-
-function le(left, right)
-@{
- return left <= right
-@}
-
-function gt(left, right)
-@{
- return left > right
-@}
-
-function ge(left, right)
-@{
- return left >= right
-@}
-
-BEGIN @{
- nan = sqrt(-1)
- inf = -log(0)
- split("== != < <= > >=", names)
- names[3] = names[3] " "
- names[5] = names[5] " "
- split("eq ne lt le gt ge", funcs)
-
- compare[1] = 2.0
- compare[2] = values[1] = -sqrt(-1.0) # nan
- compare[3] = values[2] = sqrt(-1.0) # -nan
- compare[4] = values[3] = -log(0.0) # inf
- compare[5] = values[4] = log(0.0) # -inf
-
- for (i = 1; i in values; i++) @{
- for (j = 1; j in compare; j++) @{
- for (k = 1; k in names; k++) @{
- the_func = funcs[k]
- printf("%g %s %g -> %s\n",
- values[i],
- names[k],
- compare[j],
- @@the_func(values[i],
compare[j]) ?
- "True" : "False");
- @}
- printf("\n");
- @}
- @}
-@}
-@c endfile
-@end ignore
-
-@ignore
-@c file eg/test-programs/gen-float-table.c
-#include <stdio.h>
-#include <math.h>
-#include <stdbool.h>
-
-#define def_func(name, op) \
- bool name(double left, double right) @{ \
- return left op right; \
- @}
-
-def_func(eq, ==)
-def_func(ne, !=)
-def_func(lt, <)
-def_func(le, <=)
-def_func(gt, >)
-def_func(ge, >=)
-
-struct @{
- const char *name;
- bool (*func)(double left, double right);
-@} functions[] = @{
- @{ "==", eq @},
- @{ "!=", ne @},
- @{ "< ", lt @},
- @{ "<=", le @},
- @{ "> ", gt @},
- @{ ">=", ge @},
- @{ 0, 0 @}
-@};
-
-int main()
-@{
- double values[] = @{
- -sqrt(-1), // nan
- sqrt(-1), // -nan
- -log(0.0), // inf
- log(0.0) // -inf
- @};
- double compare[] = @{ 2.0,
- -sqrt(-1), // nan
- sqrt(-1), // -nan
- -log(0.0), // inf
- log(0.0) // -inf
- @};
-
- int i, j, k;
-
- for (i = 0; i < 4; i++) @{
- for (j = 0; j < 5; j++) @{
- for (k = 0; functions[k].name != NULL; k++) @{
- printf("%g %s %g -> %s\n", values[i],
- functions[k].name,
- compare[j],
- functions[k].func(values[i], compare[j]) ? "True" :
"False");
- @}
- printf("\n");
- @}
- @}
-
- return 0;
-@}
-@c endfile
-@end ignore
-
-@ignore
-@c file eg/test-programs/gen-float-table.py
-from math import *
-
-nan = float('NaN')
-inf = float('Inf')
-
-def eq(left, right):
- return left == right
-
-def ne(left, right):
- return left != right
-
-def lt(left, right):
- return left < right
-
-def le(left, right):
- return left <= right
-
-def gt(left, right):
- return left > right
-
-def ge(left, right):
- return left >= right
-
-func_map = {
- "==": eq,
- "!=": ne,
- "< ": lt,
- "<=": le,
- "> ": gt,
- ">=": ge,
-}
-
-compare = [2.0, nan, -nan, inf, -inf]
-values = [nan, -nan, inf, -inf]
-
-for i in range(len(values)):
- for j in range(len(compare)):
- for op in func_map:
- print("%g %s %g -> %s" %
- (values[i], op, compare[j], func_map[op](values[i],
compare[j])))
-
- print("")
-@c endfile
-@end ignore
-
-@node Getting Accuracy
-@subsection Getting the Accuracy You Need
-
-Can arbitrary-precision arithmetic give exact results? There are
-no easy answers. The standard rules of algebra often do not apply
-when using floating-point arithmetic.
-Among other things, the distributive and associative laws
-do not hold completely, and order of operation may be important
-for your computation. Rounding error, cumulative precision loss,
-and underflow are often troublesome.
-
-When @command{gawk} tests the expressions @samp{0.1 + 12.2} and
-@samp{12.3} for equality using the machine double-precision arithmetic,
-it decides that they are not equal! (@xref{Comparing FP Values}.)
-You can get the result you want by increasing the precision; 56 bits in
-this case does the job:
-
-@example
-$ @kbd{gawk -M -v PREC=56 'BEGIN @{ print (0.1 + 12.2 == 12.3) @}'}
-@print{} 1
-@end example
-
-If adding more bits is good, perhaps adding even more bits of
-precision is better?
-Here is what happens if we use an even larger value of @code{PREC}:
-
-@example
-$ @kbd{gawk -M -v PREC=201 'BEGIN @{ print (0.1 + 12.2 == 12.3) @}'}
-@print{} 0
-@end example
-
-This is not a bug in @command{gawk} or in the MPFR library.
-It is easy to forget that the finite number of bits used to store the value
-is often just an approximation after proper rounding.
-The test for equality succeeds if and only if @emph{all} bits in the two
operands
-are exactly the same. Because this is not necessarily true after floating-point
-computations with a particular precision and effective rounding mode,
-a straight test for equality may not work. Instead, compare the
-two numbers to see if they are within the desirable delta of each other.
-
-In applications where 15 or fewer decimal places suffice,
-hardware double-precision arithmetic can be adequate, and is usually much
faster.
-But you need to keep in mind that every floating-point operation
-can suffer a new rounding error with catastrophic consequences, as illustrated
-by our earlier attempt to compute the value of @value{PI}.
-Extra precision can greatly enhance the stability and the accuracy
-of your computation in such cases.
-
-Additionally, you should understand that
-repeated addition is not necessarily equivalent to multiplication
-in floating-point arithmetic. In the example in
-@ref{Errors accumulate}:
-
-@example
-$ @kbd{gawk 'BEGIN @{}
-> @kbd{for (d = 1.1; d <= 1.5; d += 0.1) # loop five times (?)}
-> @kbd{i++}
-> @kbd{print i}
-> @kbd{@}'}
-@print{} 4
-@end example
-
-@noindent
-you may or may not succeed in getting the correct result by choosing
-an arbitrarily large value for @code{PREC}. Reformulation of
-the problem at hand is often the correct approach in such situations.
-
-@node Try To Round
-@subsection Try a Few Extra Bits of Precision and Rounding
-
-Instead of arbitrary-precision floating-point arithmetic,
-often all you need is an adjustment of your logic
-or a different order for the operations in your calculation.
-The stability and the accuracy of the computation of @value{PI}
-in the earlier example can be enhanced by using the following
-simple algebraic transformation:
-
-@example
-(sqrt(x * x + 1) - 1) / x @equiv{} x / (sqrt(x * x + 1) + 1)
-@end example
-
-@noindent
-After making this change, the program converges to
-@value{PI} in under 30 iterations:
-
-@example
-$ @kbd{gawk -f pi2.awk}
-@print{} 3.215390309173473
-@print{} 3.159659942097501
-@print{} 3.146086215131436
-@print{} 3.142714599645370
-@print{} 3.141873049979825
-@dots{}
-@print{} 3.141592653589797
-@print{} 3.141592653589797
-@end example
-
-@node Setting precision
-@subsection Setting the Precision
-
-@command{gawk} uses a global working precision; it does not keep track of
-the precision or accuracy of individual numbers. Performing an arithmetic
-operation or calling a built-in function rounds the result to the current
-working precision. The default working precision is 53 bits, which you can
-modify using the predefined variable @code{PREC}. You can also set the
-value to one of the predefined case-insensitive strings
-shown in @ref{table-predefined-precision-strings},
-to emulate an IEEE 754 binary format.
-
-@float Table,table-predefined-precision-strings
-@caption{Predefined precision strings for @code{PREC}}
-@multitable {@code{"double"}} {12345678901234567890123456789012345}
-@headitem @code{PREC} @tab IEEE 754 binary format
-@item @code{"half"} @tab 16-bit half-precision
-@item @code{"single"} @tab Basic 32-bit single precision
-@item @code{"double"} @tab Basic 64-bit double precision
-@item @code{"quad"} @tab Basic 128-bit quadruple precision
-@item @code{"oct"} @tab 256-bit octuple precision
-@end multitable
-@end float
-
-The following example illustrates the effects of changing precision
-on arithmetic operations:
-
-@example
-$ @kbd{gawk -M -v PREC=100 'BEGIN @{ x = 1.0e-400; print x + 0}
-> @kbd{PREC = "double"; print x + 0 @}'}
-@print{} 1e-400
-@print{} 0
-@end example
-
-@quotation CAUTION
-Be wary of floating-point constants! When reading a floating-point
-constant from program source code, @command{gawk} uses the default
-precision (that of a C @code{double}), unless overridden by an assignment
-to the special variable @code{PREC} on the command line, to store it
-internally as an MPFR number. Changing the precision using @code{PREC}
-in the program text does @emph{not} change the precision of a constant.
-
-If you need to represent a floating-point constant at a higher precision
-than the default and cannot use a command-line assignment to @code{PREC},
-you should either specify the constant as a string, or as a rational
-number, whenever possible. The following example illustrates the
-differences among various ways to print a floating-point constant:
-
-@example
-$ @kbd{gawk -M 'BEGIN @{ PREC = 113; printf("%0.25f\n", 0.1) @}'}
-@print{} 0.1000000000000000055511151
-$ @kbd{gawk -M -v PREC=113 'BEGIN @{ printf("%0.25f\n", 0.1) @}'}
-@print{} 0.1000000000000000000000000
-$ @kbd{gawk -M 'BEGIN @{ PREC = 113; printf("%0.25f\n", "0.1") @}'}
-@print{} 0.1000000000000000000000000
-$ @kbd{gawk -M 'BEGIN @{ PREC = 113; printf("%0.25f\n", 1/10) @}'}
-@print{} 0.1000000000000000000000000
-@end example
-@end quotation
-
-@node Setting the rounding mode
-@subsection Setting the Rounding Mode
-
-@cindex @code{ROUNDMODE} variable
-The @code{ROUNDMODE} variable provides
-program-level control over the rounding mode.
-The correspondence between @code{ROUNDMODE} and the IEEE
-rounding modes is shown in @ref{table-gawk-rounding-modes}.
-
-@float Table,table-gawk-rounding-modes
-@caption{@command{gawk} rounding modes}
-@multitable @columnfractions .45 .30 .25
-@headitem Rounding mode @tab IEEE name @tab @code{ROUNDMODE}
-@item Round to nearest, ties to even @tab @code{roundTiesToEven} @tab
@code{"N"} or @code{"n"}
-@item Round toward positive infinity @tab @code{roundTowardPositive} @tab
@code{"U"} or @code{"u"}
-@item Round toward negative infinity @tab @code{roundTowardNegative} @tab
@code{"D"} or @code{"d"}
-@item Round toward zero @tab @code{roundTowardZero} @tab @code{"Z"} or
@code{"z"}
-@item Round away from zero @tab @tab @code{"A"} or @code{"a"}
-@end multitable
-@end float
-
-@code{ROUNDMODE} has the default value @code{"N"}, which
-selects the IEEE 754 rounding mode @code{roundTiesToEven}.
-In @ref{table-gawk-rounding-modes}, the value @code{"A"} selects
-rounding away from zero. This is only available if your version of the
-MPFR library supports it; otherwise, setting @code{ROUNDMODE} to @code{"A"}
-has no effect.
-
-The default mode @code{roundTiesToEven} is the most preferred,
-but the least intuitive. This method does the obvious thing for most values,
-by rounding them up or down to the nearest digit.
-For example, rounding 1.132 to two digits yields 1.13,
-and rounding 1.157 yields 1.16.
-
-However, when it comes to rounding a value that is exactly halfway between,
-things do not work the way you probably learned in school.
-In this case, the number is rounded to the nearest even digit.
-So rounding 0.125 to two digits rounds down to 0.12,
-but rounding 0.6875 to three digits rounds up to 0.688.
-You probably have already encountered this rounding mode when
-using @code{printf} to format floating-point numbers.
-For example:
-
-@example
-BEGIN @{
- x = -4.5
- for (i = 1; i < 10; i++) @{
- x += 1.0
- printf("%4.1f => %2.0f\n", x, x)
- @}
-@}
-@end example
-
-@noindent
-produces the following output when run on the author's system:@footnote{It
-is possible for the output to be completely different if the
-C library in your system does not use the IEEE 754 even-rounding
-rule to round halfway cases for @code{printf}.}
-
-@example
--3.5 => -4
--2.5 => -2
--1.5 => -2
--0.5 => 0
- 0.5 => 0
- 1.5 => 2
- 2.5 => 2
- 3.5 => 4
- 4.5 => 4
-@end example
-
-The theory behind @code{roundTiesToEven} is that it more or less evenly
-distributes upward and downward rounds of exact halves, which might
-cause any accumulating round-off error to cancel itself out. This is the
-default rounding mode for IEEE 754 computing functions and operators.
-
-@c January 2018. Thanks to nethox@gmail.com for the example.
-@sidebar Rounding Modes and Conversion
-It's important to understand that, along with @code{CONVFMT} and
-@code{OFMT}, the rounding mode affects how numbers are converted to strings.
-For example, consider the following program:
-
-@example
-BEGIN @{
- pi = 3.1416
- OFMT = "%.f" # Print value as integer
- print pi # ROUNDMODE = "N" by default.
- ROUNDMODE = "U" # Now change ROUNDMODE
- print pi
-@}
-@end example
-
-@noindent
-Running this program produces this output:
-
-@example
-$ @kbd{gawk -M -f roundmode.awk}
-@print{} 3
-@print{} 4
-@end example
-@end sidebar
-
-The other rounding modes are rarely used. Rounding toward positive infinity
-(@code{roundTowardPositive}) and toward negative infinity
-(@code{roundTowardNegative}) are often used to implement interval
-arithmetic, where you adjust the rounding mode to calculate upper and
-lower bounds for the range of output. The @code{roundTowardZero} mode can
-be used for converting floating-point numbers to integers. When rounding
-away from zero, the nearest number with magnitude greater than or equal to
-the value is selected.
-
-Some numerical analysts will tell you that your choice of rounding
-style has tremendous impact on the final outcome, and advise you to
-wait until final output for any rounding. Instead, you can often avoid
-round-off error problems by setting the precision initially to some
-value sufficiently larger than the final desired precision, so that
-the accumulation of round-off error does not influence the outcome.
-If you suspect that results from your computation are sensitive to
-accumulation of round-off error, look for a significant difference in
-output when you change the rounding mode to be sure.
-
-@node Arbitrary Precision Integers
-@section Arbitrary-Precision Integer Arithmetic with @command{gawk}
-@cindex integers @subentry arbitrary precision
-@cindex arbitrary precision @subentry integers
-
-When given the @option{-M} option,
-@command{gawk} performs all integer arithmetic using GMP arbitrary-precision
-integers. Any number that looks like an integer in a source
-or @value{DF} is stored as an arbitrary-precision integer. The size
-of the integer is limited only by the available memory. For example,
-the following computes
-@iftex
-@math{5^{4^{3^{2}}}},
-@end iftex
-@ifinfo
-5^4^3^2,
-@end ifinfo
-@ifnottex
-@ifnotinfo
-5@sup{4@sup{3@sup{2}}},
-@end ifnotinfo
-@end ifnottex
-the result of which is beyond the
-limits of ordinary hardware double-precision floating-point values:
-
-@example
-$ @kbd{gawk -M 'BEGIN @{}
-> @kbd{x = 5^4^3^2}
-> @kbd{print "number of digits =", length(x)}
-> @kbd{print substr(x, 1, 20), "...", substr(x, length(x) - 19, 20)}
-> @kbd{@}'}
-@print{} number of digits = 183231
-@print{} 62060698786608744707 ... 92256259918212890625
-@end example
-
-If instead you were to compute the same value using arbitrary-precision
-floating-point values, the precision needed for correct output (using
-the formula
-@iftex
-@math{prec = 3.322 @cdot dps})
-would be @math{3.322 @cdot 183231},
-@end iftex
-@ifnottex
-@ifnotdocbook
-@samp{prec = 3.322 * dps})
-would be 3.322 x 183231,
-@end ifnotdocbook
-@end ifnottex
-@docbook
-<emphasis>prec</emphasis> = 3.322 ⋅ <emphasis>dps</emphasis>)
-would be
-<emphasis>prec</emphasis> = 3.322 ⋅ 183231,
-@end docbook
-or 608693.
-
-The result from an arithmetic operation with an integer and a floating-point
value
-is a floating-point value with a precision equal to the working precision.
-The following program calculates the eighth term in
-Sylvester's sequence@footnote{Weisstein, Eric W.
-@cite{Sylvester's Sequence}. From MathWorld---A Wolfram Web Resource
-@w{(@url{http://mathworld.wolfram.com/SylvestersSequence.html}).}}
-using a recurrence:
-
-@example
-$ @kbd{gawk -M 'BEGIN @{}
-> @kbd{s = 2.0}
-> @kbd{for (i = 1; i <= 7; i++)}
-> @kbd{s = s * (s - 1) + 1}
-> @kbd{print s}
-> @kbd{@}'}
-@print{} 113423713055421845118910464
-@end example
-
-The output differs from the actual number, 113,423,713,055,421,844,361,000,443,
-because the default precision of 53 bits is not enough to represent the
-floating-point results exactly. You can either increase the precision
-(100 bits is enough in this case), or replace the floating-point constant
-@samp{2.0} with an integer, to perform all computations using integer
-arithmetic to get the correct output.
-
-Sometimes @command{gawk} must implicitly convert an arbitrary-precision
-integer into an arbitrary-precision floating-point value. This is
-primarily because the MPFR library does not always provide the relevant
-interface to process arbitrary-precision integers or mixed-mode numbers
-as needed by an operation or function. In such a case, the precision is
-set to the minimum value necessary for exact conversion, and the working
-precision is not used for this purpose. If this is not what you need or
-want, you can employ a subterfuge and convert the integer to floating
-point first, like this:
-
-@example
-gawk -M 'BEGIN @{ n = 13; print (n + 0.0) % 2.0 @}'
-@end example
-
-You can avoid this issue altogether by specifying the number as a
floating-point value
-to begin with:
-
-@example
-gawk -M 'BEGIN @{ n = 13.0; print n % 2.0 @}'
-@end example
-
-Note that for this particular example, it is likely best
-to just use the following:
-
-@example
-gawk -M 'BEGIN @{ n = 13; print n % 2 @}'
-@end example
-
-When dividing two arbitrary precision integers with either
-@samp{/} or @samp{%}, the result is typically an arbitrary
-precision floating point value (unless the denominator evenly
-divides into the numerator).
-@ifset INTDIV
-In order to do integer division
-or remainder with arbitrary precision integers, use the built-in
-@code{intdiv0()} function (@pxref{Numeric Functions}).
-
-You can simulate the @code{intdiv0()} function in standard @command{awk}
-using this user-defined function:
-
-@example
-@c file eg/lib/intdiv0.awk
-# intdiv0 --- do integer division
-
-@c endfile
-@ignore
-@c file eg/lib/intdiv0.awk
-#
-# Arnold Robbins, arnold@@skeeve.com, Public Domain
-# July, 2014
-#
-# Name changed from div() to intdiv()
-# April, 2015
-#
-# Changed to intdiv0()
-# April, 2016
-
-@c endfile
-
-@end ignore
-@c file eg/lib/intdiv0.awk
-function intdiv0(numerator, denominator, result)
-@{
- split("", result)
-
- numerator = int(numerator)
- denominator = int(denominator)
- result["quotient"] = int(numerator / denominator)
- result["remainder"] = int(numerator % denominator)
-
- return 0.0
-@}
-@c endfile
-@end example
-
-The following example program, contributed by Katie Wasserman,
-uses @code{intdiv0()} to
-compute the digits of @value{PI} to as many places as you
-choose to set:
-
-@example
-@c file eg/prog/pi.awk
-@group
-# pi.awk --- compute the digits of pi
-@c endfile
-@c endfile
-@ignore
-@c file eg/prog/pi.awk
-#
-# Katie Wasserman, katie@@wass.net
-# August 2014
-@c endfile
-@end ignore
-@c file eg/prog/pi.awk
-
-BEGIN @{
- digits = 100000
- two = 2 * 10 ^ digits
-@end group
- pi = two
- for (m = digits * 4; m > 0; --m) @{
- d = m * 2 + 1
- x = pi * m
- intdiv0(x, d, result)
- pi = result["quotient"]
- pi = pi + two
- @}
- print pi
-@}
-@c endfile
-@end example
-
-@ignore
-Date: Wed, 20 Aug 2014 10:19:11 -0400
-To: arnold@skeeve.com
-From: Katherine Wasserman <katie@wass.net>
-Subject: Re: computation of digits of pi?
-
-Arnold,
-
->The program that you sent to compute the digits of pi using div(). Is
->that some standard algorithm that every math student knows? If so,
->what's it called?
-
-It's not that well known but it's not that obscure either
-
-It's Euler's modification to Newton's method for calculating pi.
-
-Take a look at lines (23) - (25) here:
http://mathworld.wolfram.com/PiFormulas.htm
-
-The algorithm I wrote simply expands the multiply by 2 and works from the
innermost expression outwards. I used this to program HP calculators because
it's quite easy to modify for tiny memory devices with smallish word sizes.
-
-http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=899
-
--Katie
-@end ignore
-
-When asked about the algorithm used, Katie replied:
-
-@quotation
-It's not that well known but it's not that obscure either.
-It's Euler's modification to Newton's method for calculating pi.
-Take a look at lines (23) - (25) here:
@uref{http://mathworld.wolfram.com/PiFormulas.html}.
-
-The algorithm I wrote simply expands the multiply by 2 and works from
-the innermost expression outwards. I used this to program HP calculators
-because it's quite easy to modify for tiny memory devices with smallish
-word sizes. See
-@uref{http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=899}.
-@end quotation
-@end ifset
-
-@node Checking for MPFR
-@section How To Check If MPFR Is Available
-
-@cindex checking for MPFR
-@cindex MPFR, checking for
-Occasionally, you might like to be able to check if @command{gawk}
-was invoked with the @option{-M} option, enabling arbitrary-precision
-arithmetic. You can do so with the following function, contributed
-by Andrew Schorr:
-
-@example
-@c file eg/lib/have_mpfr.awk
-# adequate_math_precision --- return true if we have enough bits
-@c endfile
-@ignore
-@c file eg/lib/have_mpfr.awk
-#
-# Andrew Schorr, aschorr@@telemetry-investments.com, Public Domain
-# May 2017
-@c endfile
-@end ignore
-@c file eg/lib/have_mpfr.awk
-
-function adequate_math_precision(n)
-@{
- return (1 != (1+(1/(2^(n-1)))))
-@}
-@c endfile
-@end example
-
-Here is code that invokes the function in order to check
-if arbitrary-precision arithmetic is available:
-
-@example
-BEGIN @{
- # How many bits of mantissa precision are required
- # for this program to function properly?
- fpbits = 123
-
- # We hope that we were invoked with MPFR enabled. If so, the
- # following statement should configure calculations to our desired
- # precision.
- PREC = fpbits
-
- if (! adequate_math_precision(fpbits)) @{
- print("Error: insufficient computation precision available.\n" \
- "Try again with the -M argument?") > "/dev/stderr"
- # Note: you may need to set a flag here to bail out of END rules
- exit 1
- @}
-@}
-@end example
-
-Please be aware that @code{exit} will jump to the @code{END} rules, if present
(@pxref{Exit Statement}).
-
-@node POSIX Floating Point Problems
-@section Standards Versus Existing Practice
-
-Historically, @command{awk} has converted any nonnumeric-looking string
-to the numeric value zero, when required. Furthermore, the original
-definition of the language and the original POSIX standards specified that
-@command{awk} only understands decimal numbers (base 10), and not octal
-(base 8) or hexadecimal numbers (base 16).
-
-Changes in the language of the
-2001 and 2004 POSIX standards can be interpreted to imply that @command{awk}
-should support additional features. These features are:
-
-@itemize @value{BULLET}
-@item
-Interpretation of floating-point data values specified in hexadecimal
-notation (e.g., @code{0xDEADBEEF}). (Note: data values, @emph{not}
-source code constants.)
-
-@item
-Support for the special IEEE 754 floating-point values ``not a number''
-(NaN), positive infinity (``inf''), and negative infinity (``@minus{}inf'').
-In particular, the format for these values is as specified by the ISO 1999
-C standard, which ignores case and can allow implementation-dependent
additional
-characters after the @samp{nan} and allow either @samp{inf} or @samp{infinity}.
-@end itemize
-
-The first problem is that both of these are clear changes to historical
-practice:
-
-@itemize @value{BULLET}
-@item
-The @command{gawk} maintainer feels that supporting hexadecimal
-floating-point values, in particular, is ugly, and was never intended by the
-original designers to be part of the language.
-
-@item
-Allowing completely alphabetic strings to have valid numeric
-values is also a very severe departure from historical practice.
-@end itemize
-
-The second problem is that the @command{gawk} maintainer feels that this
-interpretation of the standard, which required a certain amount of
-``language lawyering'' to arrive at in the first place, was not even
-intended by the standard developers. In other words, ``We see how you
-got where you are, but we don't think that that's where you want to be.''
-
-Recognizing these issues, but attempting to provide compatibility
-with the earlier versions of the standard,
-the 2008 POSIX standard added explicit wording to allow, but not require,
-that @command{awk} support hexadecimal floating-point values and
-special values for ``not a number'' and infinity.
-
-Although the @command{gawk} maintainer continues to feel that
-providing those features is inadvisable,
-nevertheless, on systems that support IEEE floating point, it seems
-reasonable to provide @emph{some} way to support NaN and infinity values.
-The solution implemented in @command{gawk} is as follows:
-
-@itemize @value{BULLET}
-@item
-With the @option{--posix} command-line option, @command{gawk} becomes
-``hands off.'' String values are passed directly to the system library's
-@code{strtod()} function, and if it successfully returns a numeric value,
-that is what's used.@footnote{You asked for it, you got it.}
-By definition, the results are not portable across
-different systems. They are also a little surprising:
-
-@example
-$ @kbd{echo nanny | gawk --posix '@{ print $1 + 0 @}'}
-@print{} nan
-$ @kbd{echo 0xDeadBeef | gawk --posix '@{ print $1 + 0 @}'}
-@print{} 3735928559
-@end example
-
-@item
-Without @option{--posix}, @command{gawk} interprets the four string values
-@samp{+inf},
-@samp{-inf},
-@samp{+nan},
-and
-@samp{-nan}
-specially, producing the corresponding special numeric values.
-The leading sign acts a signal to @command{gawk} (and the user)
-that the value is really numeric. Hexadecimal floating point is
-not supported (unless you also use @option{--non-decimal-data},
-which is @emph{not} recommended). For example:
-
-@example
-$ @kbd{echo nanny | gawk '@{ print $1 + 0 @}'}
-@print{} 0
-$ @kbd{echo +nan | gawk '@{ print $1 + 0 @}'}
-@print{} +nan
-$ @kbd{echo 0xDeadBeef | gawk '@{ print $1 + 0 @}'}
-@print{} 0
-@end example
-
-@command{gawk} ignores case in the four special values.
-Thus, @samp{+nan} and @samp{+NaN} are the same.
-@end itemize
-
-@cindex POSIX mode
-Besides handling input, @command{gawk} also needs to print ``correct'' values
on
-output when a value is either NaN or infinity. Starting with @value{PVERSION}
-4.2.2, for such values @command{gawk} prints one of the four strings
-just described: @samp{+inf}, @samp{-inf}, @samp{+nan}, or @samp{-nan}.
-Similarly, in POSIX mode, @command{gawk} prints the result of
-the system's C @code{printf()} function using the @code{%g} format string
-for the value, whatever that may be.
-
-@quotation NOTE
-The sign used for NaN values can vary! The result depends upon both
-the underlying system architecture and the underlying library used to
-format NaN values. In particular, it's possible to get different results
-for the same function call depending upon whether or not @command{gawk}
-is running in MPFR mode (@option{-M}) or not. Caveat Emptor!
-@end quotation
-
-@node Floating point summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-Most computer arithmetic is done using either integers or floating-point
-values. Standard @command{awk} uses double-precision
-floating-point values.
-
-@item
-In the early 1990s Barbie mistakenly said, ``Math class is tough!''
-Although math isn't tough, floating-point arithmetic isn't the same
-as pencil-and-paper math, and care must be taken:
-
-@c nested list
-@itemize @value{MINUS}
-@item
-Not all numbers can be represented exactly.
-
-@item
-Comparing values should use a delta, instead of being done directly
-with @samp{==} and @samp{!=}.
-
-@item
-Errors accumulate.
-
-@item
-Operations are not always truly associative or distributive.
-@end itemize
-
-@item
-Increasing the accuracy can help, but it is not a panacea.
-
-@item
-Often, increasing the accuracy and then rounding to the desired
-number of digits produces reasonable results.
-
-@item
-Use @option{-M} (or @option{--bignum}) to enable MPFR
-arithmetic. Use @code{PREC} to set the precision in bits, and
-@code{ROUNDMODE} to set the IEEE 754 rounding mode.
-
-@item
-With @option{-M}, @command{gawk} performs
-arbitrary-precision integer arithmetic using the GMP library.
-This is faster and more space-efficient than using MPFR for
-the same calculations.
-
-@item
-There are several areas with respect to floating-point
-numbers where @command{gawk} disagrees with the POSIX standard.
-It pays to be aware of them.
-
-@item
-Overall, there is no need to be unduly suspicious about the results from
-floating-point arithmetic. The lesson to remember is that floating-point
-arithmetic is always more complex than arithmetic using pencil and
-paper. In order to take advantage of the power of floating-point arithmetic,
-you need to know its limitations and work within them. For most casual
-use of floating-point arithmetic, you will often get the expected result
-if you simply round the display of your final results to the correct number
-of significant decimal digits.
-
-@item
-As general advice, avoid presenting numerical data in a manner that
-implies better precision than is actually the case.
-
-@end itemize
-
-@node Dynamic Extensions
-@chapter Writing Extensions for @command{gawk}
-@cindex dynamically loaded extensions
-
-It is possible to add new functions written in C or C++ to @command{gawk} using
-dynamically loaded libraries. This facility is available on systems
-that support the C @code{dlopen()} and @code{dlsym()}
-functions. This @value{CHAPTER} describes how to create extensions
-using code written in C or C++.
-
-If you don't know anything about C programming, you can safely skip this
-@value{CHAPTER}, although you may wish to review the documentation on the
-extensions that come with @command{gawk} (@pxref{Extension Samples}),
-and the information on the @code{gawkextlib} project (@pxref{gawkextlib}).
-The sample extensions are automatically built and installed when
-@command{gawk} is.
-
-@quotation NOTE
-When @option{--sandbox} is specified, extensions are disabled
-(@pxref{Options}).
-@end quotation
-
-@menu
-* Extension Intro:: What is an extension.
-* Plugin License:: A note about licensing.
-* Extension Mechanism Outline:: An outline of how it works.
-* Extension API Description:: A full description of the API.
-* Finding Extensions:: How @command{gawk} finds compiled extensions.
-* Extension Example:: Example C code for an extension.
-* Extension Samples:: The sample extensions that ship with
- @command{gawk}.
-* gawkextlib:: The @code{gawkextlib} project.
-* Extension summary:: Extension summary.
-* Extension Exercises:: Exercises.
-@end menu
-
-@node Extension Intro
-@section Introduction
-
-@cindex plug-in
-An @dfn{extension} (sometimes called a @dfn{plug-in}) is a piece of
-external compiled code that @command{gawk} can load at runtime to
-provide additional functionality, over and above the built-in capabilities
-described in the rest of this @value{DOCUMENT}.
-
-Extensions are useful because they allow you (of course) to extend
-@command{gawk}'s functionality. For example, they can provide access to
-system calls (such as @code{chdir()} to change directory) and to other
-C library routines that could be of use. As with most software,
-``the sky is the limit''; if you can imagine something that you might
-want to do and can write in C or C++, you can write an extension to do it!
-
-Extensions are written in C or C++, using the @dfn{application programming
-interface} (API) defined for this purpose by the @command{gawk}
-developers. The rest of this @value{CHAPTER} explains
-the facilities that the API provides and how to use
-them, and presents a small example extension. In addition, it documents
-the sample extensions included in the @command{gawk} distribution
-and describes the @code{gawkextlib} project.
-@ifclear FOR_PRINT
-@xref{Extension Design}, for a discussion of the extension mechanism
-goals and design.
-@end ifclear
-@ifset FOR_PRINT
-See
@uref{https://www.gnu.org/software/gawk/manual/html_node/Extension-Design.html}
-for a discussion of the extension mechanism
-goals and design.
-@end ifset
-
-@node Plugin License
-@section Extension Licensing
-
-Every dynamic extension must be distributed under a license that is
-compatible with the GNU GPL (@pxref{Copying}).
-
-In order for the extension to tell @command{gawk} that it is
-properly licensed, the extension must define the global symbol
-@code{plugin_is_GPL_compatible}. If this symbol does not exist,
-@command{gawk} emits a fatal error and exits when it tries to load
-your extension.
-
-The declared type of the symbol should be @code{int}. It does not need
-to be in any allocated section, though. The code merely asserts that
-the symbol exists in the global scope. Something like this is enough:
-
-@example
-int plugin_is_GPL_compatible;
-@end example
-
-@node Extension Mechanism Outline
-@section How It Works at a High Level
-
-Communication between
-@command{gawk} and an extension is two-way. First, when an extension
-is loaded, @command{gawk} passes it a pointer to a @code{struct} whose fields
are
-function pointers.
-@ifnotdocbook
-This is shown in @ref{figure-load-extension}.
-@end ifnotdocbook
-@ifdocbook
-This is shown in @inlineraw{docbook, <xref linkend="figure-load-extension"/>}.
-@end ifdocbook
-
-@ifnotdocbook
-@float Figure,figure-load-extension
-@caption{Loading the extension}
-@center @image{gawk_api-figure1, , , Loading the extension}
-@end float
-@end ifnotdocbook
-
-@docbook
-<figure id="figure-load-extension" float="0">
-<title>Loading the extension</title>
-<mediaobject>
-<imageobject role="web"><imagedata fileref="api-figure1.png"
format="PNG"/></imageobject>
-</mediaobject>
-</figure>
-@end docbook
-
-The extension can call functions inside @command{gawk} through these
-function pointers, at runtime, without needing (link-time) access
-to @command{gawk}'s symbols. One of these function pointers is to a
-function for ``registering'' new functions.
-@ifnotdocbook
-This is shown in @ref{figure-register-new-function}.
-@end ifnotdocbook
-@ifdocbook
-This is shown in @inlineraw{docbook, <xref
linkend="figure-register-new-function"/>}.
-@end ifdocbook
-
-@ifnotdocbook
-@float Figure,figure-register-new-function
-@caption{Registering a new function}
-@center @image{gawk_api-figure2, , , Registering a new Function}
-@end float
-@end ifnotdocbook
-
-@docbook
-<figure id="figure-register-new-function" float="0">
-<title>Registering a new function</title>
-<mediaobject>
-<imageobject role="web"><imagedata fileref="api-figure2.png"
format="PNG"/></imageobject>
-</mediaobject>
-</figure>
-@end docbook
-
-In the other direction, the extension registers its new functions
-with @command{gawk} by passing function pointers to the functions that
-provide the new feature (@code{do_chdir()}, for example). @command{gawk}
-associates the function pointer with a name and can then call it, using a
-defined calling convention.
-@ifnotdocbook
-This is shown in @ref{figure-call-new-function}.
-@end ifnotdocbook
-@ifdocbook
-This is shown in @inlineraw{docbook, <xref
linkend="figure-call-new-function"/>}.
-@end ifdocbook
-
-@ifnotdocbook
-@float Figure,figure-call-new-function
-@caption{Calling the new function}
-@center @image{gawk_api-figure3, , , Calling the new function}
-@end float
-@end ifnotdocbook
-
-@docbook
-<figure id="figure-call-new-function" float="0">
-<title>Calling the new function</title>
-<mediaobject>
-<imageobject role="web"><imagedata fileref="api-figure3.png"
format="PNG"/></imageobject>
-</mediaobject>
-</figure>
-@end docbook
-
-The @code{do_@var{xxx}()} function, in turn, then uses the function
-pointers in the API @code{struct} to do its work, such as updating
-variables or arrays, printing messages, setting @code{ERRNO}, and so on.
-
-Convenience macros make calling through the function pointers look
-like regular function calls so that extension code is quite readable
-and understandable.
-
-Although all of this sounds somewhat complicated, the result is that
-extension code is quite straightforward to write and to read. You can
-see this in the sample extension @file{filefuncs.c} (@pxref{Extension
-Example}) and also in the @file{testext.c} code for testing the APIs.
-
-Some other bits and pieces:
-
-@itemize @value{BULLET}
-@item
-The API provides access to @command{gawk}'s @code{do_@var{xxx}} values,
-reflecting command-line options, like @code{do_lint}, @code{do_profiling},
-and so on (@pxref{Extension API Variables}).
-These are informational: an extension cannot affect their values
-inside @command{gawk}. In addition, attempting to assign to them
-produces a compile-time error.
-
-@item
-The API also provides major and minor version numbers, so that an
-extension can check if the @command{gawk} it is loaded with supports the
-facilities it was compiled with. (Version mismatches ``shouldn't''
-happen, but we all know how @emph{that} goes.)
-@xref{Extension Versioning} for details.
-@end itemize
-
-@node Extension API Description
-@section API Description
-@cindex extension API
-
-C or C++ code for an extension must include the header file
-@file{gawkapi.h}, which declares the functions and defines the data
-types used to communicate with @command{gawk}.
-This (rather large) @value{SECTION} describes the API in detail.
-
-@menu
-* Extension API Functions Introduction:: Introduction to the API functions.
-* General Data Types:: The data types.
-* Memory Allocation Functions:: Functions for allocating memory.
-* Constructor Functions:: Functions for creating values.
-* API Ownership of MPFR and GMP Values:: Managing MPFR and GMP Values.
-* Registration Functions:: Functions to register things with
- @command{gawk}.
-* Printing Messages:: Functions for printing messages.
-* Updating @code{ERRNO}:: Functions for updating @code{ERRNO}.
-* Requesting Values:: How to get a value.
-* Accessing Parameters:: Functions for accessing parameters.
-* Symbol Table Access:: Functions for accessing global
- variables.
-* Array Manipulation:: Functions for working with arrays.
-* Redirection API:: How to access and manipulate
- redirections.
-* Extension API Variables:: Variables provided by the API.
-* Extension API Boilerplate:: Boilerplate code for using the API.
-* Changes from API V1:: Changes from V1 of the API.
-@end menu
-
-@node Extension API Functions Introduction
-@subsection Introduction
-
-Access to facilities within @command{gawk} is achieved
-by calling through function pointers passed into your extension.
-
-API function pointers are provided for the following kinds of operations:
-
-@itemize @value{BULLET}
-@item
-Allocating, reallocating, and releasing memory.
-
-@item
-Registration functions. You may register:
-
-@c nested list
-@itemize @value{MINUS}
-@item
-Extension functions
-@item
-Exit callbacks
-@item
-A version string
-@item
-Input parsers
-@item
-Output wrappers
-@item
-Two-way processors
-@end itemize
-
-All of these are discussed in detail later in this @value{CHAPTER}.
-
-@item
-Printing fatal, warning, and ``lint'' warning messages.
-
-@item
-Updating @code{ERRNO}, or unsetting it.
-
-@item
-Accessing parameters, including converting an undefined parameter into
-an array.
-
-@item
-Symbol table access: retrieving a global variable, creating one,
-or changing one.
-
-@item
-Creating and releasing cached values; this provides an
-efficient way to use values for multiple variables and
-can be a big performance win.
-
-@item
-Manipulating arrays:
-
-@itemize @value{MINUS}
-@item
-Retrieving, adding, deleting, and modifying elements
-
-@item
-Getting the count of elements in an array
-
-@item
-Creating a new array
-
-@item
-Clearing an array
-
-@item
-Flattening an array for easy C-style looping over all its indices and elements
-@end itemize
-
-@item
-Accessing and manipulating redirections.
-
-@end itemize
-
-Some points about using the API:
-
-@itemize @value{BULLET}
-@item
-The following types, macros, and/or functions are referenced
-in @file{gawkapi.h}. For correct use, you must therefore include the
-corresponding standard header file @emph{before} including @file{gawkapi.h}.
-The list of macros and related header files is shown in
@ref{table-api-std-headers}.
-
-@float Table,table-api-std-headers
-@caption{Standard header files needed by API}
-@multitable {@code{memset()}, @code{memcpy()}} {@code{<sys/types.h>}}
-@headitem C entity @tab Header file
-@item @code{EOF} @tab @code{<stdio.h>}
-@item Values for @code{errno} @tab @code{<errno.h>}
-@item @code{FILE} @tab @code{<stdio.h>}
-@item @code{NULL} @tab @code{<stddef.h>}
-@item @code{memcpy()} @tab @code{<string.h>}
-@item @code{memset()} @tab @code{<string.h>}
-@item @code{size_t} @tab @code{<sys/types.h>}
-@item @code{struct stat} @tab @code{<sys/stat.h>}
-@end multitable
-@end float
-
-Due to portability concerns, especially to systems that are not
-fully standards-compliant, it is your responsibility
-to include the correct files in the correct way. This requirement
-is necessary in order to keep @file{gawkapi.h} clean, instead of becoming
-a portability hodge-podge as can be seen in some parts of
-the @command{gawk} source code.
-
-@item
-If your extension uses MPFR facilities, and you wish to receive such
-values from @command{gawk} and/or pass such values to it, you must include the
-@code{<mpfr.h>} header before including @code{<gawkapi.h>}.
-
-@item
-The @file{gawkapi.h} file may be included more than once without ill effect.
-Doing so, however, is poor coding practice.
-
-@item
-Although the API only uses ISO C 90 features, there is an exception; the
-``constructor'' functions use the @code{inline} keyword. If your compiler
-does not support this keyword, you should either place
-@samp{-Dinline=''} on your command line or use the GNU Autotools and include a
-@file{config.h} file in your extensions.
-
-@item
-All pointers filled in by @command{gawk} point to memory
-managed by @command{gawk} and should be treated by the extension as
-read-only.
-
-Memory for @emph{all} strings passed into @command{gawk}
-from the extension @emph{must} come from calling one of
-@code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()},
-and is managed by @command{gawk} from then on.
-
-Memory for MPFR/GMP values that come from @command{gawk}
-should also be treated as read-only. However, unlike strings,
-memory for MPFR/GMP values allocated by an extension and passed
-into @command{gawk} is @emph{copied} by @command{gawk}; the extension
-should then free the values itself to avoid memory leaks. This is
-discussed further in @strong{API Ownership of MPFR and GMP Values}.
-
-@item
-The API defines several simple @code{struct}s that map values as seen
-from @command{awk}. A value can be a @code{double}, a string, or an
-array (as in multidimensional arrays, or when creating a new array).
-
-String values maintain both pointer and length, because embedded @sc{nul}
-characters are allowed.
-
-@quotation NOTE
-By intent, @command{gawk} maintains strings using the current multibyte
-encoding (as defined by @env{LC_@var{xxx}} environment variables)
-and not using wide characters. This matches how @command{gawk} stores
-strings internally and also how characters are likely to be input into
-and output from files.
-@end quotation
-
-@quotation NOTE
-String values passed to an extension by @command{gawk} are always
-@sc{nul}-terminated. Thus it is safe to pass such string values to
-standard library and system routines. However, because @command{gawk}
-allows embedded @sc{nul} characters in string data, before using the data
-as a regular C string, you should check that the length for that string
-passed to the extension matches the return value of @code{strlen()}
-for it.
-@end quotation
-
-@item
-When retrieving a value (such as a parameter or that of a global variable
-or array element), the extension requests a specific type (number, string,
-scalar, value cookie, array, or ``undefined''). When the request is
-``undefined,'' the returned value will have the real underlying type.
-
-However, if the request and actual type don't match, the access function
-returns ``false'' and fills in the type of the actual value that is there,
-so that the extension can, e.g., print an error message
-(such as ``scalar passed where array expected'').
-
-@c This is documented in the header file and needs some expanding upon.
-@c The table there should be presented here
-@end itemize
-
-You may call the API functions by using the function pointers
-directly, but the interface is not so pretty. To make extension code look
-more like regular code, the @file{gawkapi.h} header file defines several
-macros that you should use in your code. This @value{SECTION} presents
-the macros as if they were functions.
-
-@node General Data Types
-@subsection General-Purpose Data Types
-
-@cindex Robbins @subentry Arnold
-@cindex Ramey, Chet
-@quotation
-@i{I have a true love/hate relationship with unions.}
-@author Arnold Robbins
-@end quotation
-
-@quotation
-@i{That's the thing about unions: the compiler will arrange things so they
-can accommodate both love and hate.}
-@author Chet Ramey
-@end quotation
-
-The extension API defines a number of simple types and structures for
-general-purpose use. Additional, more specialized, data structures are
-introduced in subsequent @value{SECTION}s, together with the functions
-that use them.
-
-The general-purpose types and structures are as follows:
-
-@table @code
-@item typedef void *awk_ext_id_t;
-A value of this type is received from @command{gawk} when an extension is
loaded.
-That value must then be passed back to @command{gawk} as the first parameter of
-each API function.
-
-@item #define awk_const @dots{}
-This macro expands to @samp{const} when compiling an extension,
-and to nothing when compiling @command{gawk} itself. This makes
-certain fields in the API data structures unwritable from extension code,
-while allowing @command{gawk} to use them as it needs to.
-
-@item typedef enum awk_bool @{
-@itemx @ @ @ @ awk_false = 0,
-@itemx @ @ @ @ awk_true
-@itemx @} awk_bool_t;
-A simple Boolean type.
-
-@item typedef struct awk_string @{
-@itemx @ @ @ @ char *str;@ @ @ @ @ @ /* data */
-@itemx @ @ @ @ size_t len;@ @ @ @ @ /* length thereof, in chars */
-@itemx @} awk_string_t;
-This represents a mutable string. @command{gawk}
-owns the memory pointed to if it supplied
-the value. Otherwise, it takes ownership of the memory pointed to.
-@emph{Such memory must come from calling one of the
-@code{gawk_malloc()}, @code{gawk_calloc()}, or
-@code{gawk_realloc()} functions!}
-
-As mentioned earlier, strings are maintained using the current
-multibyte encoding.
-
-@item typedef enum @{
-@itemx @ @ @ @ AWK_UNDEFINED,
-@itemx @ @ @ @ AWK_NUMBER,
-@itemx @ @ @ @ AWK_STRING,
-@itemx @ @ @ @ AWK_REGEX,
-@itemx @ @ @ @ AWK_STRNUM,
-@itemx @ @ @ @ AWK_ARRAY,
-@itemx @ @ @ @ AWK_SCALAR,@ @ @ @ @ @ @ @ @ /* opaque access to a variable */
-@itemx @ @ @ @ AWK_VALUE_COOKIE,@ @ @ /* for updating a previously created
value */
-@itemx @ @ @ @ AWK_BOOL
-@itemx @} awk_valtype_t;
-This @code{enum} indicates the type of a value.
-It is used in the following @code{struct}.
-
-@item typedef struct awk_value @{
-@itemx @ @ @ @ awk_valtype_t val_type;
-@itemx @ @ @ @ union @{
-@itemx @ @ @ @ @ @ @ @ awk_string_t@ @ @ @ @ @ @ s;
-@itemx @ @ @ @ @ @ @ @ awknum_t@ @ @ @ @ @ @ @ @ @ @ n;
-@itemx @ @ @ @ @ @ @ @ awk_array_t@ @ @ @ @ @ @ @ a;
-@itemx @ @ @ @ @ @ @ @ awk_scalar_t@ @ @ @ @ @ @ scl;
-@itemx @ @ @ @ @ @ @ @ awk_value_cookie_t@ vc;
-@itemx @ @ @ @ @ @ @ @ awk_bool_t@ @ @ @ @ @ @ @ @ b;
-@itemx @ @ @ @ @} u;
-@itemx @} awk_value_t;
-An ``@command{awk} value.''
-The @code{val_type} member indicates what kind of value the
-@code{union} holds, and each member is of the appropriate type.
-
-@item #define str_value@ @ @ @ @ @ u.s
-@itemx #define strnum_value@ @ @ str_value
-@itemx #define regex_value@ @ @ @ str_value
-@itemx #define num_value@ @ @ @ @ @ u.n.d
-@itemx #define num_type@ @ @ @ @ @ @ u.n.type
-@itemx #define num_ptr@ @ @ @ @ @ @ @ u.n.ptr
-@itemx #define array_cookie@ @ @ u.a
-@itemx #define scalar_cookie@ @ u.scl
-@itemx #define value_cookie@ @ @ u.vc
-@itemx #define bool_value@ @ @ @ @ u.b
-Using these macros makes accessing the fields of the @code{awk_value_t} more
-readable.
-
-@item enum AWK_NUMBER_TYPE @{
-@itemx @ @ @ @ AWK_NUMBER_TYPE_DOUBLE,
-@itemx @ @ @ @ AWK_NUMBER_TYPE_MPFR,
-@itemx @ @ @ @ AWK_NUMBER_TYPE_MPZ
-@itemx @};
-This @code{enum} is used in the following structure for defining the
-type of numeric value that is being worked with. It is declared at the
-top level of the file so that it works correctly for C++ as well as for C.
-
-@item typedef struct awk_number @{
-@itemx @ @ @ @ double d;
-@itemx @ @ @ @ enum AWK_NUMBER_TYPE type;
-@itemx @ @ @ @ void *ptr;
-@itemx @} awk_number_t;
-This represents a numeric value. Internally, @command{gawk} stores
-every number as either a C @code{double}, a GMP integer, or an MPFR
-arbitrary-precision floating-point value. In order to allow extensions
-to also support GMP and MPFR values, numeric values are passed in this
-structure.
-
-The double-precision @code{d} element is always populated
-in data received from @command{gawk}. In addition, by examining the
-@code{type} member, an extension can determine if the @code{ptr}
-member is either a GMP integer (type @code{mpz_ptr}), or an MPFR
-floating-point value (type @code{mpfr_ptr_t}), and cast it appropriately.
-
-@quotation CAUTION
-Any MPFR or MPZ values that you create and pass to @command{gawk}
-to save are @emph{copied}. This means you are responsible to release
-the storage once you're done with it. See the sample @code{intdiv}
-extension for some example code.
-@end quotation
-
-@item typedef void *awk_scalar_t;
-Scalars can be represented as an opaque type. These values are obtained
-from @command{gawk} and then passed back into it. This is discussed
-in a general fashion in the text following this list, and in more detail in
-@ref{Symbol table by cookie}.
-
-@item typedef void *awk_value_cookie_t;
-A ``value cookie'' is an opaque type representing a cached value.
-This is also discussed in a general fashion in the text following this list,
-and in more detail in @ref{Cached values}.
-
-@end table
-
-Scalar values in @command{awk} are numbers, strings, strnums, or typed
regexps. The
-@code{awk_value_t} struct represents values. The @code{val_type} member
-indicates what is in the @code{union}.
-
-Representing numbers is easy---the API uses a C @code{double}. Strings
-require more work. Because @command{gawk} allows embedded @sc{nul} bytes
-in string values, a string must be represented as a pair containing a
-data pointer and length. This is the @code{awk_string_t} type.
-
-A strnum (numeric string) value is represented as a string and consists
-of user input data that appears to be numeric.
-When an extension creates a strnum value, the result is a string flagged
-as user input. Subsequent parsing by @command{gawk} then determines whether it
-looks like a number and should be treated as a strnum, or as a regular string.
-
-This is useful in cases where an extension function would like to do something
-comparable to the @code{split()} function which sets the strnum attribute
-on the array elements it creates. For example, an extension that implements
-CSV splitting would want to use this feature. This is also useful for a
-function that retrieves a data item from a database. The PostgreSQL
-@code{PQgetvalue()} function, for example, returns a string that may be numeric
-or textual depending on the contents.
-
-Typed regexp values (@pxref{Strong Regexp Constants}) are not of
-much use to extension functions. Extension functions can tell that
-they've received them, and create them for scalar values. Otherwise,
-they can examine the text of the regexp through @code{regex_value.str}
-and @code{regex_value.len}.
-
-Identifiers (i.e., the names of global variables) can be associated
-with either scalar values or with arrays. In addition, @command{gawk}
-provides true arrays of arrays, where any given array element can
-itself be an array. Discussion of arrays is delayed until
-@ref{Array Manipulation}.
-
-The various macros listed earlier make it easier to use the elements
-of the @code{union} as if they were fields in a @code{struct}; this
-is a common coding practice in C. Such code is easier to write and to
-read, but it remains @emph{your} responsibility to make sure that
-the @code{val_type} member correctly reflects the type of the value in
-the @code{awk_value_t} struct.
-
-Conceptually, the first three members of the @code{union} (number, string,
-and array) are all that is needed for working with @command{awk} values.
-However, because the API provides routines for accessing and changing
-the value of a global scalar variable only by using the variable's name,
-there is a performance penalty: @command{gawk} must find the variable
-each time it is accessed and changed. This turns out to be a real issue,
-not just a theoretical one.
-
-Thus, if you know that your extension will spend considerable time
-reading and/or changing the value of one or more scalar variables, you
-can obtain a @dfn{scalar cookie}@footnote{See
-@uref{http://catb.org/jargon/html/C/cookie.html, the ``cookie'' entry in the
Jargon file} for a
-definition of @dfn{cookie}, and
@uref{http://catb.org/jargon/html/M/magic-cookie.html,
-the ``magic cookie'' entry in the Jargon file} for a nice example.
-@ifclear FOR_PRINT
-See also the entry for ``Cookie'' in the @ref{Glossary}.
-@end ifclear
-}
-object for that variable, and then use
-the cookie for getting the variable's value or for changing the variable's
-value.
-The @code{awk_scalar_t} type holds a scalar cookie, and the
-@code{scalar_cookie} macro provides access to the value of that type
-in the @code{awk_value_t} struct.
-Given a scalar cookie, @command{gawk} can directly retrieve or
-modify the value, as required, without having to find it first.
-
-The @code{awk_value_cookie_t} type and @code{value_cookie} macro are similar.
-If you know that you wish to
-use the same numeric or string @emph{value} for one or more variables,
-you can create the value once, retaining a @dfn{value cookie} for it,
-and then pass in that value cookie whenever you wish to set the value of a
-variable. This saves storage space within the running @command{gawk}
-process and reduces the time needed to create the value.
-
-@node Memory Allocation Functions
-@subsection Memory Allocation Functions and Convenience Macros
-@cindex allocating memory for extensions
-@cindex extensions @subentry loadable @subentry allocating memory
-@cindex memory, allocating for extensions
-
-The API provides a number of @dfn{memory allocation} functions for
-allocating memory that can be passed to @command{gawk}, as well as a number of
-convenience macros.
-This @value{SUBSECTION} presents them all as function prototypes, in
-the way that extension code would use them:
-
-@table @code
-@item void *gawk_malloc(size_t size);
-Call the correct version of @code{malloc()} to allocate storage that may
-be passed to @command{gawk}.
-
-@item void *gawk_calloc(size_t nmemb, size_t size);
-Call the correct version of @code{calloc()} to allocate storage that may
-be passed to @command{gawk}.
-
-@item void *gawk_realloc(void *ptr, size_t size);
-Call the correct version of @code{realloc()} to allocate storage that may
-be passed to @command{gawk}.
-
-@item void gawk_free(void *ptr);
-Call the correct version of @code{free()} to release storage that was
-allocated with @code{gawk_malloc()}, @code{gawk_calloc()}, or
@code{gawk_realloc()}.
-@end table
-
-The API has to provide these functions because it is possible
-for an extension to be compiled and linked against a different
-version of the C library than was used for the @command{gawk}
-executable.@footnote{This is more common on MS-Windows systems, but it
-can happen on Unix-like systems as well.} If @command{gawk} were
-to use its version of @code{free()} when the memory came from an
-unrelated version of @code{malloc()}, unexpected behavior would
-likely result.
-
-Three convenience macros may be used for allocating storage
-from @code{gawk_malloc()}, @code{gawk_calloc}, and
-@code{gawk_realloc()}. If the allocation fails, they cause @command{gawk}
-to exit with a fatal error message. They should be used as if they were
-procedure calls that do not return a value:
-
-@table @code
-@item #define emalloc(pointer, type, size, message) @dots{}
-The arguments to this macro are as follows:
-
-@c nested table
-@table @code
-@item pointer
-The pointer variable to point at the allocated storage.
-
-@item type
-The type of the pointer variable. This is used to create a cast for
-the call to @code{gawk_malloc()}.
-
-@item size
-The total number of bytes to be allocated.
-
-@item message
-A message to be prefixed to the fatal error message. Typically this is the name
-of the function using the macro.
-@end table
-
-@noindent
-For example, you might allocate a string value like so:
-
-@example
-@group
-awk_value_t result;
-char *message;
-const char greet[] = "Don't Panic!";
-
-emalloc(message, char *, sizeof(greet), "myfunc");
-strcpy(message, greet);
-make_malloced_string(message, strlen(message), & result);
-@end group
-@end example
-
-@sp 2
-@item #define ezalloc(pointer, type, size, message) @dots{}
-This is like @code{emalloc()}, but it calls @code{gawk_calloc()}
-instead of @code{gawk_malloc()}.
-The arguments are the same as for the @code{emalloc()} macro, but this
-macro guarantees that the memory returned is initialized to zero.
-
-@item #define erealloc(pointer, type, size, message) @dots{}
-This is like @code{emalloc()}, but it calls @code{gawk_realloc()}
-instead of @code{gawk_malloc()}.
-The arguments are the same as for the @code{emalloc()} macro.
-@end table
-
-Two additional functions allocate MPFR and GMP objects for use
-by extension functions that need to create and then return such
-values.
-
-@quotation NOTE
-These functions are obsolete. Extension functions that need local MPFR
-and GMP values should simply allocate them on the stack and clear them,
-as any other code would.
-@end quotation
-
-@noindent
-The functions are:
-
-@table @code
-@item void *get_mpfr_ptr();
-Allocate and initialize an MPFR object and return a pointer to it.
-If the allocation fails, @command{gawk} exits with a fatal
-``out of memory'' error. If @command{gawk} was compiled without
-MPFR support, calling this function causes a fatal error.
-
-@item void *get_mpz_ptr();
-Allocate and initialize a GMP object and return a pointer to it.
-If the allocation fails, @command{gawk} exits with a fatal
-``out of memory'' error. If @command{gawk} was compiled without
-MPFR support, calling this function causes a fatal error.
-@end table
-
-Both of these functions return @samp{void *}, since the @file{gawkapi.h}
-header file should not have dependency upon @code{<mpfr.h>} (and
@code{<gmp.h>},
-which is included from @code{<mpfr.h>}). The actual return values are of
-types @code{mpfr_ptr} and @code{mpz_ptr} respectively, and you should cast
-the return values appropriately before assigning the results to variables
-of the correct types.
-
-The memory allocated by these functions should be freed with
-@code{gawk_free()}.
-
-@node Constructor Functions
-@subsection Constructor Functions
-
-The API provides a number of @dfn{constructor} functions for creating
-string and numeric values, as well as a number of convenience macros.
-This @value{SUBSECTION} presents them all as function prototypes, in
-the way that extension code would use them:
-
-@table @code
-@item static inline awk_value_t *
-@itemx make_const_string(const char *string, size_t length, awk_value_t
*result);
-This function creates a string value in the @code{awk_value_t} variable
-pointed to by @code{result}. It expects @code{string} to be a C string constant
-(or other string data), and automatically creates a @emph{copy} of the data
-for storage in @code{result}. It returns @code{result}.
-
-@item static inline awk_value_t *
-@itemx make_malloced_string(const char *string, size_t length, awk_value_t
*result);
-This function creates a string value in the @code{awk_value_t} variable
-pointed to by @code{result}. It expects @code{string} to be a @samp{char *}
-value pointing to data previously obtained from @code{gawk_malloc()},
@code{gawk_calloc()}, or @code{gawk_realloc()}. The idea here
-is that the data is passed directly to @command{gawk}, which assumes
-responsibility for it. It returns @code{result}.
-
-@item static inline awk_value_t *
-@itemx make_null_string(awk_value_t *result);
-This specialized function creates a null string (the ``undefined'' value)
-in the @code{awk_value_t} variable pointed to by @code{result}.
-It returns @code{result}.
-
-@item static inline awk_value_t *
-@itemx make_number(double num, awk_value_t *result);
-This function simply creates a numeric value in the @code{awk_value_t} variable
-pointed to by @code{result}.
-
-@item static inline awk_value_t *
-@itemx make_number_mpz(void *mpz, awk_value_t *result);
-This function creates a GMP number value in @code{result}.
-The @code{mpz} must be from a call to @code{get_mpz_ptr()}
-(and thus be of real underlying type @code{mpz_ptr}).
-
-@item static inline awk_value_t *
-@itemx make_number_mpfr(void *mpfr, awk_value_t *result);
-This function creates an MPFR number value in @code{result}.
-The @code{mpfr} must be from a call to @code{get_mpfr_ptr()}.
-
-@item static inline awk_value_t *
-@itemx make_const_user_input(const char *string, size_t length, awk_value_t
*result);
-This function is identical to @code{make_const_string()}, but the string is
-flagged as user input that should be treated as a strnum value if the contents
-of the string are numeric.
-
-@item static inline awk_value_t *
-@itemx make_malloced_user_input(const char *string, size_t length, awk_value_t
*result);
-This function is identical to @code{make_malloced_string()}, but the string is
-flagged as user input that should be treated as a strnum value if the contents
-of the string are numeric.
-
-@item static inline awk_value_t *
-@itemx make_const_regex(const char *string, size_t length, awk_value_t
*result);
-This function creates a strongly typed regexp value by allocating a copy of
the string.
-@code{string} is the regular expression of length @code{len}.
-
-@item static inline awk_value_t *
-@itemx make_malloced_regex(const char *string, size_t length, awk_value_t
*result);
-This function creates a strongly typed regexp value. @code{string} is
-the regular expression of length @code{len}. It expects @code{string}
-to be a @samp{char *} value pointing to data previously obtained from
-@code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()}.
-
-@item static inline awk_value_t *
-@itemx make_bool(awk_bool_t boolval, awk_value_t *result);
-This function creates a boolean value in the @code{awk_value_t} variable
-pointed to by @code{result}.
-
-@end table
-
-@node API Ownership of MPFR and GMP Values
-@subsection Managing MPFR and GMP Values
-@cindex MPFR values, API ownership of
-@cindex GMP values, API ownership of
-@cindex API, ownership of MPFR and GMP values
-
-MPFR and GMP values are different from string values, where you can
-``take ownership'' of the value simply by assigning pointers. For example:
-
-@example
-char *p = gawk_malloc(42); p @ii{``owns'' the memory}
-char *q = p;
-p = NULL; @ii{now} q @ii{``owns'' it}
-@end example
-
-MPFR and GMP objects are indeed allocated on the stack or dynamically,
-but the MPFR and GMP libraries treat these objects as values, the same way that
-you would pass an @code{int} or a @code{double} by value. There is no
-way to ``transfer ownership'' of MPFR and GMP objects.
-
-The final results of an MPFR or GMP calculation should be passed back
-to @command{gawk}, by value, as you would a string or a @code{double}.
-@command{gawk} will take care of freeing the storage.
-
-Thus, code in an extension should look like this:
-
-@example
-mpz_t part1, part2, answer; @ii{declare local values}
-
-mpz_set_si(part1, 21); @ii{do some computations}
-mpz_set_si(part2, 21);
-mpz_add(answer, part1, part2);
-@dots{}
-/* assume that result is a parameter of type (awk_value_t *). */
-make_number_mpz(answer, & result); @ii{set it with final GMP value}
-
-mpz_clear(part1); @ii{release intermediate values}
-mpz_clear(part2);
-
-return result; @ii{value in @code{answer} managed by
@code{gawk}}
-@end example
-
-@node Registration Functions
-@subsection Registration Functions
-@cindex register loadable extension
-@cindex extensions @subentry loadable @subentry registration
-
-This @value{SECTION} describes the API functions for
-registering parts of your extension with @command{gawk}.
-
-@menu
-* Extension Functions:: Registering extension functions.
-* Exit Callback Functions:: Registering an exit callback.
-* Extension Version String:: Registering a version string.
-* Input Parsers:: Registering an input parser.
-* Output Wrappers:: Registering an output wrapper.
-* Two-way processors:: Registering a two-way processor.
-@end menu
-
-@node Extension Functions
-@subsubsection Registering An Extension Function
-
-Extension functions are described by the following record:
-
-@example
-@group
-typedef struct awk_ext_func @{
-@ @ @ @ const char *name;
-@ @ @ @ awk_value_t *(*const function)(int num_actual_args,
-@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
awk_value_t *result,
-@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ struct
awk_ext_func *finfo);
-@ @ @ @ const size_t max_expected_args;
-@ @ @ @ const size_t min_required_args;
-@ @ @ @ awk_bool_t suppress_lint;
-@ @ @ @ void *data; /* opaque pointer to any extra state */
-@} awk_ext_func_t;
-@end group
-@end example
-
-The fields are:
-
-@table @code
-@item const char *name;
-The name of the new function.
-@command{awk}-level code calls the function by this name.
-This is a regular C string.
-
-Function names must obey the rules for @command{awk}
-identifiers. That is, they must begin with either an English letter
-or an underscore, which may be followed by any number of
-letters, digits, and underscores.
-Letter case in function names is significant.
-
-@item awk_value_t *(*const function)(int num_actual_args,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t
*result,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ struct
awk_ext_func *finfo);
-This is a pointer to the C function that provides the extension's
-functionality.
-The function must fill in @code{*result} with either a number,
-a string, or a regexp.
-@command{gawk} takes ownership of any string memory.
-As mentioned earlier, string memory @emph{must} come from one of
-@code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()}.
-
-The @code{num_actual_args} argument tells the C function how many
-actual parameters were passed from the calling @command{awk} code.
-
-The @code{finfo} parameter is a pointer to the @code{awk_ext_func_t} for
-this function. The called function may access data within it as desired, or
not.
-
-The function must return the value of @code{result}.
-This is for the convenience of the calling code inside @command{gawk}.
-
-@item const size_t max_expected_args;
-This is the maximum number of arguments the function expects to receive.
-If called with more arguments than this, and if lint checking has
-been enabled, then @command{gawk} prints a warning message. For more
-information, see the entry for @code{suppress_lint}, later in this list.
-
-@item const size_t min_required_args;
-This is the minimum number of arguments the function expects to receive.
-If called with fewer arguments, @command{gawk} prints a fatal error
-message and exits.
-
-@item awk_bool_t suppress_lint;
-This flag tells @command{gawk} not to print a lint message if lint
-checking has been enabled and if more arguments were supplied in the call
-than expected. An extension function can tell if @command{gawk} already
-printed at least one such message by checking if @samp{num_actual_args >
-finfo->max_expected_args}. If so, and the function does not want more
-lint messages to be printed, it should set @code{finfo->suppress_lint}
-to @code{awk_true}.
-
-@item void *data;
-This is an opaque pointer to any data that an extension function may
-wish to have available when called. Passing the @code{awk_ext_func_t}
-structure to the extension function, and having this pointer available
-in it enable writing a single C or C++ function that implements multiple
-@command{awk}-level extension functions.
-@end table
-
-Once you have a record representing your extension function, you register
-it with @command{gawk} using this API function:
-
-@table @code
-@item awk_bool_t add_ext_func(const char *name_space, awk_ext_func_t *func);
-This function returns true upon success, false otherwise.
-The @code{name_space} parameter is the namespace in which to place
-the function (@pxref{Namespaces}).
-Use an empty string (@code{""}) or @code{"awk"} to place
-the function in the default @code{awk} namespace.
-The @code{func} pointer is the address of a
-@code{struct} representing your function, as just described.
-
-@command{gawk} does not modify what @code{func} points to, but the
-extension function itself receives this pointer and can modify what it
-points to, thus it is purposely not declared to be @code{const}.
-@end table
-
-The combination of @code{min_required_args}, @code{max_expected_args},
-and @code{suppress_lint} may be confusing. Here is how you should
-set things up.
-
-@table @asis
-@item Any number of arguments is valid
-Set @code{min_required_args} and @code{max_expected_args} to zero and
-set @code{suppress_lint} to @code{awk_true}.
-
-@item A minimum number of arguments is required, no limit on maximum number of
arguments
-Set @code{min_required_args} to the minimum required. Set
-@code{max_expected_args} to zero and
-set @code{suppress_lint} to @code{awk_true}.
-
-@item A minimum number of arguments is required, a maximum number is expected
-Set @code{min_required_args} to the minimum required. Set
-@code{max_expected_args} to the maximum expected.
-Set @code{suppress_lint} to @code{awk_false}.
-
-@item A minimum number of arguments is required, and no more than a maximum is
allowed
-Set @code{min_required_args} to the minimum required. Set
-@code{max_expected_args} to the maximum expected.
-Set @code{suppress_lint} to @code{awk_false}.
-In your extension function, check that @code{num_actual_args} does not
-exceed @code{f->max_expected_args}. If it does, issue a fatal error message.
-@end table
-
-@node Exit Callback Functions
-@subsubsection Registering An Exit Callback Function
-
-An @dfn{exit callback} function is a function that
-@command{gawk} calls before it exits.
-Such functions are useful if you have general ``cleanup'' tasks
-that should be performed in your extension (such as closing database
-connections or other resource deallocations).
-You can register such
-a function with @command{gawk} using the following function:
-
-@table @code
-@item void awk_atexit(void (*funcp)(void *data, int exit_status),
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ void *arg0);
-The parameters are:
-
-@c nested table
-@table @code
-@item funcp
-A pointer to the function to be called before @command{gawk} exits. The
@code{data}
-parameter will be the original value of @code{arg0}.
-The @code{exit_status} parameter is the exit status value that
-@command{gawk} intends to pass to the @code{exit()} system call.
-
-@item arg0
-A pointer to private data that @command{gawk} saves in order to pass to
-the function pointed to by @code{funcp}.
-@end table
-@end table
-
-Exit callback functions are called in last-in, first-out (LIFO)
-order---that is, in the reverse order in which they are registered with
-@command{gawk}.
-
-@node Extension Version String
-@subsubsection Registering An Extension Version String
-
-You can register a version string that indicates the name and
-version of your extension with @command{gawk}, as follows:
-
-@table @code
-@item void register_ext_version(const char *version);
-Register the string pointed to by @code{version} with @command{gawk}.
-Note that @command{gawk} does @emph{not} copy the @code{version} string, so
-it should not be changed.
-@end table
-
-@command{gawk} prints all registered extension version strings when it
-is invoked with the @option{--version} option.
-
-@node Input Parsers
-@subsubsection Customized Input Parsers
-@cindex customized input parser
-
-By default, @command{gawk} reads text files as its input. It uses the value
-of @code{RS} to find the end of an input record, and then uses @code{FS}
-(or @code{FIELDWIDTHS} or @code{FPAT}) to split it into fields (@pxref{Reading
Files}).
-Additionally, it sets the value of @code{RT} (@pxref{Built-in Variables}).
-
-If you want, you can provide your own custom input parser. An input
-parser's job is to return a record to the @command{gawk} record-processing
-code, along with indicators for the value and length of the data to be
-used for @code{RT}, if any.
-
-To provide an input parser, you must first provide two functions
-(where @var{XXX} is a prefix name for your extension):
-
-@table @code
-@item awk_bool_t @var{XXX}_can_take_file(const awk_input_buf_t *iobuf);
-This function examines the information available in @code{iobuf}
-(which we discuss shortly). Based on the information there, it
-decides if the input parser should be used for this file.
-If so, it should return true. Otherwise, it should return false.
-It should not change any state (variable values, etc.) within @command{gawk}.
-
-@item awk_bool_t @var{XXX}_take_control_of(awk_input_buf_t *iobuf);
-When @command{gawk} decides to hand control of the file over to the
-input parser, it calls this function. This function in turn must fill
-in certain fields in the @code{awk_input_buf_t} structure and ensure
-that certain conditions are true. It should then return true. If an
-error of some kind occurs, it should not fill in any fields and should
-return false; then @command{gawk} will not use the input parser.
-The details are presented shortly.
-@end table
-
-Your extension should package these functions inside an
-@code{awk_input_parser_t}, which looks like this:
-
-@example
-@group
-typedef struct awk_input_parser @{
- const char *name; /* name of parser */
- awk_bool_t (*can_take_file)(const awk_input_buf_t *iobuf);
- awk_bool_t (*take_control_of)(awk_input_buf_t *iobuf);
- awk_const struct awk_input_parser *awk_const next; /* for gawk */
-@} awk_input_parser_t;
-@end group
-@end example
-
-The fields are:
-
-@table @code
-@item const char *name;
-The name of the input parser. This is a regular C string.
-
-@item awk_bool_t (*can_take_file)(const awk_input_buf_t *iobuf);
-A pointer to your @code{@var{XXX}_can_take_file()} function.
-
-@item awk_bool_t (*take_control_of)(awk_input_buf_t *iobuf);
-A pointer to your @code{@var{XXX}_take_control_of()} function.
-
-@item awk_const struct input_parser *awk_const next;
-This is for use by @command{gawk};
-therefore it is marked @code{awk_const} so that the extension cannot
-modify it.
-@end table
-
-The steps are as follows:
-
-@enumerate
-@item
-Create a @code{static awk_input_parser_t} variable and initialize it
-appropriately.
-
-@item
-When your extension is loaded, register your input parser with
-@command{gawk} using the @code{register_input_parser()} API function
-(described next).
-@end enumerate
-
-An @code{awk_input_buf_t} looks like this:
-
-@example
-typedef struct awk_input @{
- const char *name; /* filename */
- int fd; /* file descriptor */
-#define INVALID_HANDLE (-1)
- void *opaque; /* private data for input parsers */
- int (*get_record)(char **out, struct awk_input *iobuf,
- int *errcode, char **rt_start, size_t *rt_len,
- const awk_fieldwidth_info_t **field_width);
- ssize_t (*read_func)();
- void (*close_func)(struct awk_input *iobuf);
- struct stat sbuf; /* stat buf */
-@} awk_input_buf_t;
-@end example
-
-The fields can be divided into two categories: those for use (initially,
-at least) by @code{@var{XXX}_can_take_file()}, and those for use by
-@code{@var{XXX}_take_control_of()}. The first group of fields and their uses
-are as follows:
-
-@table @code
-@item const char *name;
-The name of the file.
-
-@item int fd;
-A file descriptor for the file. @command{gawk} attempts to open
-the file for reading using the @code{open()} system call. If it was
-able to open the file, then @code{fd} will @emph{not} be equal to
-@code{INVALID_HANDLE}. Otherwise, it will.
-
-An extension can decide that it doesn't want to use the open file descriptor
-provided by @command{gawk}. In such a case it can close the file and
-set @code{fd} to @code{INVALID_HANDLE}, or it can leave it alone and
-keep it's own file descriptor in private data pointed to by the
-@code{opaque} pointer (see further in this list). In any case, if
-the file descriptor is valid, it should @emph{not} just overwrite the
-value with something else; doing so would cause a resource leak.
-
-@item struct stat sbuf;
-If the file descriptor is valid, then @command{gawk} will have filled
-in this structure via a call to the @code{fstat()} system call.
-Otherwise, if the @code{lstat()} system call is available, it will
-use that. If @code{lstat()} is not available, then it uses @code{stat()}.
-
-Getting the file's information allows extensions to check the type of
-the file even if it could not be opened. This occurs, for example,
-on Windows systems when trying to use @code{open()} on a directory.
-
-If @command{gawk} was not able to get the file information, then
-@code{sbuf} will be zeroed out. In particular, extension code
-can check if @samp{sbuf.st_mode == 0}. If that's true, then there
-is no information in @code{sbuf}.
-@end table
-
-The @code{@var{XXX}_can_take_file()} function should examine these
-fields and decide if the input parser should be used for the file.
-The decision can be made based upon @command{gawk} state (the value
-of a variable defined previously by the extension and set by
-@command{awk} code), the name of the
-file, whether or not the file descriptor is valid, the information
-in the @code{struct stat}, or any combination of these factors.
-
-Once @code{@var{XXX}_can_take_file()} has returned true, and
-@command{gawk} has decided to use your input parser, it calls
-@code{@var{XXX}_take_control_of()}. That function then fills
-either the @code{get_record} field or the @code{read_func} field in
-the @code{awk_input_buf_t}. It must also ensure that @code{fd} is @emph{not}
-set to @code{INVALID_HANDLE}. The following list describes the fields that
-may be filled by @code{@var{XXX}_take_control_of()}:
-
-@table @code
-@item void *opaque;
-This is used to hold any state information needed by the input parser
-for this file. It is ``opaque'' to @command{gawk}. The input parser
-is not required to use this pointer.
-
-@item int@ (*get_record)(char@ **out,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ struct@ awk_input *iobuf,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ int *errcode,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ char **rt_start,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ size_t *rt_len,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_fieldwidth_info_t
**field_width);
-This function pointer should point to a function that creates the input
-records. Said function is the core of the input parser. Its behavior
-is described in the text following this list.
-
-@item ssize_t (*read_func)(int, void *, size_t);
-This function pointer should point to a function that has the
-same behavior as the standard POSIX @code{read()} system call.
-It is an alternative to the @code{get_record} pointer. Its behavior
-is also described in the text following this list.
-
-@item void (*close_func)(struct awk_input *iobuf);
-This function pointer should point to a function that does
-the ``teardown.'' It should release any resources allocated by
-@code{@var{XXX}_take_control_of()}. It may also close the file. If it
-does so, it should set the @code{fd} field to @code{INVALID_HANDLE}.
-
-If @code{fd} is still not @code{INVALID_HANDLE} after the call to this
-function, @command{gawk} calls the regular @code{close()} system call.
-
-Having a ``teardown'' function is optional. If your input parser does
-not need it, do not set this field. Then, @command{gawk} calls the
-regular @code{close()} system call on the file descriptor, so it should
-be valid.
-@end table
-
-The @code{@var{XXX}_get_record()} function does the work of creating
-input records. The parameters are as follows:
-
-@table @code
-@item char **out
-This is a pointer to a @code{char *} variable that is set to point
-to the record. @command{gawk} makes its own copy of the data, so
-your extension must manage this storage.
-
-@item struct awk_input *iobuf
-This is the @code{awk_input_buf_t} for the file. Two of its fields should
-be used by your extension: @code{fd} for reading data, and @code{opaque}
-for managing any private state.
-
-@item int *errcode
-If an error occurs, @code{*errcode} should be set to an appropriate
-code from @code{<errno.h>}.
-
-@item char **rt_start
-@itemx size_t *rt_len
-If the concept of a ``record terminator'' makes sense, then
-@code{*rt_start} should be set to point to the data to be used for
-@code{RT}, and @code{*rt_len} should be set to the length of the
-data. Otherwise, @code{*rt_len} should be set to zero.
-Here too, @command{gawk} makes its own copy of this data, so your
-extension must manage this storage.
-
-@item const awk_fieldwidth_info_t **field_width
-If @code{field_width} is not @code{NULL}, then @code{*field_width} will be
initialized
-to @code{NULL}, and the function may set it to point to a structure
-supplying field width information to override the default
-field parsing mechanism. Note that this structure will not
-be copied by @command{gawk}; it must persist at least until the next call
-to @code{get_record} or @code{close_func}. Note also that @code{field_width} is
-@code{NULL} when @code{getline} is assigning the results to a variable, thus
-field parsing is not needed.
-
-If the parser sets @code{*field_width},
-then @command{gawk} uses this layout to parse the input record,
-and the @code{PROCINFO["FS"]} value will be @code{"API"} while this record
-is active in @code{$0}.
-The @code{awk_fieldwidth_info_t} data structure
-is described below.
-@end table
-
-The return value is the length of the buffer pointed to by
-@code{*out}, or @code{EOF} if end-of-file was reached or an
-error occurred.
-
-It is guaranteed that @code{errcode} is a valid pointer, so there is no
-need to test for a @code{NULL} value. @command{gawk} sets @code{*errcode}
-to zero, so there is no need to set it unless an error occurs.
-
-If an error does occur, the function should return @code{EOF} and set
-@code{*errcode} to a value greater than zero. In that case, if @code{*errcode}
-does not equal zero, @command{gawk} automatically updates
-the @code{ERRNO} variable based on the value of @code{*errcode}.
-(In general, setting @samp{*errcode = errno} should do the right thing.)
-
-As an alternative to supplying a function that returns an input record,
-you may instead supply a function that simply reads bytes, and let
-@command{gawk} parse the data into records. If you do so, the data
-should be returned in the multibyte encoding of the current locale.
-Such a function should follow the same behavior as the @code{read()}
-system call, and you fill in the @code{read_func} pointer with its
-address in the @code{awk_input_buf_t} structure.
-
-By default, @command{gawk} sets the @code{read_func} pointer to
-point to the @code{read()} system call. So your extension need not
-set this field explicitly.
-
-@quotation NOTE
-You must choose one method or the other: either a function that
-returns a record, or one that returns raw data. In particular,
-if you supply a function to get a record, @command{gawk} will
-call it, and will never call the raw read function.
-@end quotation
-
-@command{gawk} ships with a sample extension that reads directories,
-returning records for each entry in a directory (@pxref{Extension
-Sample Readdir}). You may wish to use that code as a guide for writing
-your own input parser.
-
-When writing an input parser, you should think about (and document)
-how it is expected to interact with @command{awk} code. You may want
-it to always be called, and to take effect as appropriate (as the
-@code{readdir} extension does). Or you may want it to take effect
-based upon the value of an @command{awk} variable, as the XML extension
-from the @code{gawkextlib} project does (@pxref{gawkextlib}).
-In the latter case, code in a @code{BEGINFILE} rule
-can look at @code{FILENAME} and @code{ERRNO} to decide whether or
-not to activate your input parser (@pxref{BEGINFILE/ENDFILE}).
-
-If you would like to override the default field parsing mechanism for a given
-record, then you must populate an @code{awk_fieldwidth_info_t} structure,
-which looks like this:
-
-@example
-typedef struct @{
- awk_bool_t use_chars; /* false ==> use bytes */
- size_t nf; /* number of fields in record (NF) */
- struct awk_field_info @{
- size_t skip; /* amount to skip before field starts */
- size_t len; /* length of field */
- @} fields[1]; /* actual dimension should be nf */
-@} awk_fieldwidth_info_t;
-@end example
-
-The fields are:
-
-@table @code
-@item awk_bool_t use_chars;
-Set this to @code{awk_true} if the field lengths are specified in terms
-of potentially multi-byte characters, and set it to @code{awk_false} if
-the lengths are in terms of bytes.
-Performance will be better if the values are supplied in
-terms of bytes.
-
-@item size_t nf;
-Set this to the number of fields in the input record, i.e. @code{NF}.
-
-@item struct awk_field_info fields[nf];
-This is a variable-length array whose actual dimension should be @code{nf}.
-For each field, the @code{skip} element should be set to the number
-of characters or bytes, as controlled by the @code{use_chars} flag,
-to skip before the start of this field. The @code{len} element provides
-the length of the field. The values in @code{fields[0]} provide the information
-for @code{$1}, and so on through the @code{fields[nf-1]} element containing
the information for @code{$NF}.
-@end table
-
-A convenience macro @code{awk_fieldwidth_info_size(numfields)} is provided to
-calculate the appropriate size of a variable-length
-@code{awk_fieldwidth_info_t} structure containing @code{numfields} fields.
This can
-be used as an argument to @code{malloc()} or in a union to allocate space
-statically. Please refer to the @code{readdir_test} sample extension for an
-example.
-
-You register your input parser with the following function:
-
-@table @code
-@item void register_input_parser(awk_input_parser_t *input_parser);
-Register the input parser pointed to by @code{input_parser} with
-@command{gawk}.
-@end table
-
-@node Output Wrappers
-@subsubsection Customized Output Wrappers
-@cindex customized output wrapper
-
-@cindex output wrapper
-An @dfn{output wrapper} is the mirror image of an input parser.
-It allows an extension to take over the output to a file opened
-with the @samp{>} or @samp{>>} I/O redirection operators (@pxref{Redirection}).
-
-The output wrapper is very similar to the input parser structure:
-
-@example
-typedef struct awk_output_wrapper @{
- const char *name; /* name of the wrapper */
- awk_bool_t (*can_take_file)(const awk_output_buf_t *outbuf);
- awk_bool_t (*take_control_of)(awk_output_buf_t *outbuf);
- awk_const struct awk_output_wrapper *awk_const next; /* for gawk */
-@} awk_output_wrapper_t;
-@end example
-
-The members are as follows:
-
-@table @code
-@item const char *name;
-This is the name of the output wrapper.
-
-@item awk_bool_t (*can_take_file)(const awk_output_buf_t *outbuf);
-This points to a function that examines the information in
-the @code{awk_output_buf_t} structure pointed to by @code{outbuf}.
-It should return true if the output wrapper wants to take over the
-file, and false otherwise. It should not change any state (variable
-values, etc.) within @command{gawk}.
-
-@item awk_bool_t (*take_control_of)(awk_output_buf_t *outbuf);
-The function pointed to by this field is called when @command{gawk}
-decides to let the output wrapper take control of the file. It should
-fill in appropriate members of the @code{awk_output_buf_t} structure,
-as described next, and return true if successful, false otherwise.
-
-@item awk_const struct output_wrapper *awk_const next;
-This is for use by @command{gawk};
-therefore it is marked @code{awk_const} so that the extension cannot
-modify it.
-@end table
-
-The @code{awk_output_buf_t} structure looks like this:
-
-@example
-typedef struct awk_output_buf @{
- const char *name; /* name of output file */
- const char *mode; /* mode argument to fopen */
- FILE *fp; /* stdio file pointer */
- awk_bool_t redirected; /* true if a wrapper is active */
- void *opaque; /* for use by output wrapper */
- size_t (*gawk_fwrite)(const void *buf, size_t size, size_t count,
- FILE *fp, void *opaque);
- int (*gawk_fflush)(FILE *fp, void *opaque);
- int (*gawk_ferror)(FILE *fp, void *opaque);
- int (*gawk_fclose)(FILE *fp, void *opaque);
-@} awk_output_buf_t;
-@end example
-
-Here too, your extension will define @code{@var{XXX}_can_take_file()}
-and @code{@var{XXX}_take_control_of()} functions that examine and update
-data members in the @code{awk_output_buf_t}.
-The data members are as follows:
-
-@table @code
-@item const char *name;
-The name of the output file.
-
-@item const char *mode;
-The mode string (as would be used in the second argument to @code{fopen()})
-with which the file was opened.
-
-@item FILE *fp;
-The @code{FILE} pointer from @code{<stdio.h>}. @command{gawk} opens the file
-before attempting to find an output wrapper.
-
-@item awk_bool_t redirected;
-This field must be set to true by the @code{@var{XXX}_take_control_of()}
function.
-
-@item void *opaque;
-This pointer is opaque to @command{gawk}. The extension should use it to store
-a pointer to any private data associated with the file.
-
-@item size_t (*gawk_fwrite)(const void *buf, size_t size, size_t count,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ FILE *fp, void *opaque);
-@itemx int (*gawk_fflush)(FILE *fp, void *opaque);
-@itemx int (*gawk_ferror)(FILE *fp, void *opaque);
-@itemx int (*gawk_fclose)(FILE *fp, void *opaque);
-These pointers should be set to point to functions that perform
-the equivalent function as the @code{<stdio.h>} functions do, if appropriate.
-@command{gawk} uses these function pointers for all output.
-@command{gawk} initializes the pointers to point to internal ``pass-through''
-functions that just call the regular @code{<stdio.h>} functions, so an
-extension only needs to redefine those functions that are appropriate for
-what it does.
-@end table
-
-The @code{@var{XXX}_can_take_file()} function should make a decision based
-upon the @code{name} and @code{mode} fields, and any additional state
-(such as @command{awk} variable values) that is appropriate.
-@command{gawk} attempts to open the named file for writing. The @code{fp}
-member will be @code{NULL} only if it fails.
-
-When @command{gawk} calls @code{@var{XXX}_take_control_of()}, that function
should fill
-in the other fields as appropriate, except for @code{fp}, which it should just
-use normally if it's not @code{NULL}.
-
-You register your output wrapper with the following function:
-
-@table @code
-@item void register_output_wrapper(awk_output_wrapper_t *output_wrapper);
-Register the output wrapper pointed to by @code{output_wrapper} with
-@command{gawk}.
-@end table
-
-@node Two-way processors
-@subsubsection Customized Two-way Processors
-@cindex customized two-way processor
-
-A @dfn{two-way processor} combines an input parser and an output wrapper for
-two-way I/O with the @samp{|&} operator (@pxref{Redirection}). It makes
identical
-use of the @code{awk_input_parser_t} and @code{awk_output_buf_t} structures
-as described earlier.
-
-A two-way processor is represented by the following structure:
-
-@example
-typedef struct awk_two_way_processor @{
- const char *name; /* name of the two-way processor */
- awk_bool_t (*can_take_two_way)(const char *name);
- awk_bool_t (*take_control_of)(const char *name,
- awk_input_buf_t *inbuf,
- awk_output_buf_t *outbuf);
- awk_const struct awk_two_way_processor *awk_const next; /* for gawk */
-@} awk_two_way_processor_t;
-@end example
-
-The fields are as follows:
-
-@table @code
-@item const char *name;
-The name of the two-way processor.
-
-@item awk_bool_t (*can_take_two_way)(const char *name);
-The function pointed to by this field should return true if it wants to take
over two-way I/O for this @value{FN}.
-It should not change any state (variable
-values, etc.) within @command{gawk}.
-
-@item awk_bool_t (*take_control_of)(const char *name,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
awk_input_buf_t *inbuf,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
awk_output_buf_t *outbuf);
-The function pointed to by this field should fill in the
@code{awk_input_buf_t} and
-@code{awk_output_buf_t} structures pointed to by @code{inbuf} and
-@code{outbuf}, respectively. These structures were described earlier.
-
-@item awk_const struct two_way_processor *awk_const next;
-This is for use by @command{gawk};
-therefore it is marked @code{awk_const} so that the extension cannot
-modify it.
-@end table
-
-As with the input parser and output processor, you provide
-``yes I can take this'' and ``take over for this'' functions,
-@code{@var{XXX}_can_take_two_way()} and @code{@var{XXX}_take_control_of()}.
-
-You register your two-way processor with the following function:
-
-@table @code
-@item void register_two_way_processor(awk_two_way_processor_t
*two_way_processor);
-Register the two-way processor pointed to by @code{two_way_processor} with
-@command{gawk}.
-@end table
-
-@node Printing Messages
-@subsection Printing Messages
-@cindex printing @subentry messages from extensions
-@cindex messages from extensions
-
-You can print different kinds of warning messages from your
-extension, as described here. Note that for these functions,
-you must pass in the extension ID received from @command{gawk}
-when the extension was loaded:@footnote{Because the API uses only ISO C 90
-features, it cannot make use of the ISO C 99 variadic macro feature to hide
-that parameter. More's the pity.}
-
-@table @code
-@item void fatal(awk_ext_id_t id, const char *format, ...);
-Print a message and then cause @command{gawk} to exit immediately.
-
-@item void nonfatal(awk_ext_id_t id, const char *format, ...);
-Print a nonfatal error message.
-
-@item void warning(awk_ext_id_t id, const char *format, ...);
-Print a warning message.
-
-@item void lintwarn(awk_ext_id_t id, const char *format, ...);
-Print a ``lint warning.'' Normally this is the same as printing a
-warning message, but if @command{gawk} was invoked with @samp{--lint=fatal},
-then lint warnings become fatal error messages.
-@end table
-
-All of these functions are otherwise like the C @code{printf()}
-family of functions, where the @code{format} parameter is a string
-with literal characters and formatting codes intermixed.
-
-@node Updating @code{ERRNO}
-@subsection Updating @code{ERRNO}
-
-The following functions allow you to update the @code{ERRNO}
-variable:
-
-@table @code
-@item void update_ERRNO_int(int errno_val);
-Set @code{ERRNO} to the string equivalent of the error code
-in @code{errno_val}. The value should be one of the defined
-error codes in @code{<errno.h>}, and @command{gawk} turns it
-into a (possibly translated) string using the C @code{strerror()} function.
-
-@item void update_ERRNO_string(const char *string);
-Set @code{ERRNO} directly to the string value of @code{ERRNO}.
-@command{gawk} makes a copy of the value of @code{string}.
-
-@item void unset_ERRNO(void);
-Unset @code{ERRNO}.
-@end table
-
-@node Requesting Values
-@subsection Requesting Values
-
-All of the functions that return values from @command{gawk}
-work in the same way. You pass in an @code{awk_valtype_t} value
-to indicate what kind of value you expect. If the actual value
-matches what you requested, the function returns true and fills
-in the @code{awk_value_t} result.
-Otherwise, the function returns false, and the @code{val_type}
-member indicates the type of the actual value. You may then
-print an error message or reissue the request for the actual
-value type, as appropriate. This behavior is summarized in
-@ref{table-value-types-returned}.
-
-@float Table,table-value-types-returned
-@caption{API value types returned}
-@docbook
-<informaltable>
-<tgroup cols="8">
- <colspec colname="c1"/>
- <colspec colname="c2"/>
- <colspec colname="c3"/>
- <colspec colname="c4"/>
- <colspec colname="c5"/>
- <colspec colname="c6"/>
- <colspec colname="c7"/>
- <colspec colname="c8"/>
- <colspec colname="c9"/>
- <spanspec spanname="hspan" namest="c3" nameend="c9" align="center"/>
- <thead>
- <row><entry></entry><entry spanname="hspan"><para>Type of Actual
Value</para></entry></row>
- <row>
- <entry></entry>
- <entry></entry>
- <entry><para>String</para></entry>
- <entry><para>Strnum</para></entry>
- <entry><para>Number</para></entry>
- <entry><para>Regex</para></entry>
- <entry><para>Bool</para></entry>
- <entry><para>Array</para></entry>
- <entry><para>Undefined</para></entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry></entry>
- <entry><para><emphasis role="bold">String</emphasis></para></entry>
- <entry><para>String</para></entry>
- <entry><para>String</para></entry>
- <entry><para>String</para></entry>
- <entry><para>String</para></entry>
- <entry><para>String</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- </row>
- <row>
- <entry></entry>
- <entry><para><emphasis role="bold">Strnum</emphasis></para></entry>
- <entry><para>false</para></entry>
- <entry><para>Strnum</para></entry>
- <entry><para>Strnum</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- </row>
- <row>
- <entry></entry>
- <entry><para><emphasis role="bold">Number</emphasis></para></entry>
- <entry><para>Number</para></entry>
- <entry><para>Number</para></entry>
- <entry><para>Number</para></entry>
- <entry><para>false</para></entry>
- <entry><para>Number</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- </row>
- <row>
- <entry><para><emphasis role="bold">Type</emphasis></para></entry>
- <entry><para><emphasis role="bold">Regex</emphasis></para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>Regex</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- </row>
- <row>
- <entry><para><emphasis role="bold">Requested</emphasis></para></entry>
- <entry><para><emphasis role="bold">Bool</emphasis></para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>Bool</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- </row>
- <row>
- <entry><para></para></entry>
- <entry><para><emphasis role="bold">Array</emphasis></para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>Array</para></entry>
- <entry><para>false</para></entry>
- </row>
- <row>
- <entry></entry>
- <entry><para><emphasis role="bold">Scalar</emphasis></para></entry>
- <entry><para>Scalar</para></entry>
- <entry><para>Scalar</para></entry>
- <entry><para>Scalar</para></entry>
- <entry><para>Scalar</para></entry>
- <entry><para>Scalar</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- </row>
- <row>
- <entry></entry>
- <entry><para><emphasis role="bold">Undefined</emphasis></para></entry>
- <entry><para>String</para></entry>
- <entry><para>Strnum</para></entry>
- <entry><para>Number</para></entry>
- <entry><para>Regex</para></entry>
- <entry><para>Bool</para></entry>
- <entry><para>Array</para></entry>
- <entry><para>Undefined</para></entry>
- </row>
- <row>
- <entry></entry>
- <entry><para><emphasis role="bold">Value cookie</emphasis></para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- <entry><para>false</para></entry>
- </row>
- </tbody>
-</tgroup>
-</informaltable>
-@end docbook
-
-@ifnotplaintext
-@ifnotdocbook
-@multitable @columnfractions .50 .50
-@headitem @tab Type of Actual Value
-@end multitable
-@c 10/2014: Thanks to Karl Berry for this bit to reduce the space:
-@tex
-\vglue-1.1\baselineskip
-@end tex
-@c @multitable @columnfractions .166 .166 .198 .15 .15 .166
-@multitable {Requested} {Undefined} {Number} {Number} {Scalar} {Regex}
{Number} {Array} {Undefined}
-@headitem @tab @tab String @tab Strnum @tab Number @tab Regex @tab Bool @tab
Array @tab Undefined
-@item @tab @b{String} @tab String @tab String @tab String @tab String @tab
String @tab false @tab false
-@item @tab @b{Strnum} @tab false @tab Strnum @tab Strnum @tab false @tab false
@tab false @tab false
-@item @tab @b{Number} @tab Number @tab Number @tab Number @tab false @tab
Number @tab false @tab false
-@item @b{Type} @tab @b{Regex} @tab false @tab false @tab false @tab Regex @tab
false @tab false @tab false
-@item @b{Requested} @tab @b{Bool} @tab false @tab false @tab false @tab false
@tab Bool @tab false @tab false
-@item @tab @b{Array} @tab false @tab false @tab false @tab false @tab false
@tab Array @tab false
-@item @tab @b{Scalar} @tab Scalar @tab Scalar @tab Scalar @tab Scalar @tab
Scalar @tab false @tab false
-@item @tab @b{Undefined} @tab String @tab Strnum @tab Number @tab Regex @tab
Bool @tab Array @tab Undefined
-@item @tab @b{Value cookie} @tab false @tab false @tab false @tab false @tab
false @tab false @tab false
-@end multitable
-@end ifnotdocbook
-@end ifnotplaintext
-@ifplaintext
-@verbatim
-
+----------------------------------------------------------------+
- | Type of Actual Value:
|
-
+--------+--------+--------+--------+--------+-------+-----------+
- | String | Strnum | Number | Regex | Bool | Array |
Undefined |
-+-----------+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | String | String | String | String | String | String | false |
false |
-|
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | Strnum | false | Strnum | Strnum | false | false | false |
false |
-|
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | Number | Number | Number | Number | false | Number | false |
false |
-|
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | Regex | false | false | false | Regex | false | false |
false |
-|
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| Type | Bool | false | false | false | false | Bool | false |
false |
-| Requested
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | Array | false | false | false | false | false | Array |
false |
-|
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | Scalar | Scalar | Scalar | Scalar | Scalar | Scalar | false |
false |
-|
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | Undefined | String | Strnum | Number | Regex | Bool | Array |
Undefined |
-|
+-----------+--------+--------+--------+--------+--------+-------+-----------+
-| | Value | false | false | false | false | false | false |
false |
-| | Cookie | | | | | | |
|
-+-----------+-----------+--------+--------+--------+--------+--------+-------+-----------+
-@end verbatim
-@end ifplaintext
-@end float
-
-@node Accessing Parameters
-@subsection Accessing and Updating Parameters
-
-Two functions give you access to the arguments (parameters)
-passed to your extension function. They are:
-
-@table @code
-@item awk_bool_t get_argument(size_t count,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
-Fill in the @code{awk_value_t} structure pointed to by @code{result}
-with the @code{count}th argument. Return true if the actual
-type matches @code{wanted}, and false otherwise. In the latter
-case, @code{result@w{->}val_type} indicates the actual type
-(@pxref{table-value-types-returned}). Counts are zero-based---the first
-argument is numbered zero, the second one, and so on. @code{wanted}
-indicates the type of value expected.
-
-@item awk_bool_t set_argument(size_t count, awk_array_t array);
-Convert a parameter that was undefined into an array; this provides
-call by reference for arrays. Return false if @code{count} is too big,
-or if the argument's type is not undefined. @xref{Array Manipulation}
-for more information on creating arrays.
-@end table
-
-@node Symbol Table Access
-@subsection Symbol Table Access
-@cindex accessing global variables from extensions
-
-Two sets of routines provide access to global variables, and one set
-allows you to create and release cached values.
-
-@menu
-* Symbol table by name:: Accessing variables by name.
-* Symbol table by cookie:: Accessing variables by ``cookie''.
-* Cached values:: Creating and using cached values.
-@end menu
-
-@node Symbol table by name
-@subsubsection Variable Access and Update by Name
-
-The following routines provide the ability to access and update
-global @command{awk}-level variables by name. In compiler terminology,
-identifiers of different kinds are termed @dfn{symbols}, thus the ``sym''
-in the routines' names. The data structure that stores information
-about symbols is termed a @dfn{symbol table}.
-The functions are as follows:
-
-@table @code
-@item awk_bool_t sym_lookup(const char *name,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
-Fill in the @code{awk_value_t} structure pointed to by @code{result}
-with the value of the variable named by the string @code{name}, which is
-a regular C string. @code{wanted} indicates the type of value expected.
-Return true if the actual type matches @code{wanted}, and false otherwise.
-In the latter case, @code{result->val_type} indicates the actual type
-(@pxref{table-value-types-returned}).
-
-@item awk_bool_t sym_lookup_ns(const char *name,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const char
*name_space,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
-This is like @code{sym_lookup()}, but the @code{name_space} parameter allows
you
-to specify which namespace @code{name} is part of. @code{name_space} cannot be
-@code{NULL}. If it is @code{""} or @code{"awk"}, then @code{name} is searched
-for in the default @code{awk} namespace.
-
-Note that @code{namespace} is a C++ keyword. For interoperability with C++,
-you should avoid using that identifier in C code.
-
-@item awk_bool_t sym_update(const char *name, awk_value_t *value);
-Update the variable named by the string @code{name}, which is a regular
-C string. The variable is added to @command{gawk}'s symbol table
-if it is not there. Return true if everything worked, and false otherwise.
-
-Changing types (scalar to array or vice versa) of an existing variable
-is @emph{not} allowed, nor may this routine be used to update an array.
-This routine cannot be used to update any of the predefined
-variables (such as @code{ARGC} or @code{NF}).
-
-@item awk_bool_t sym_update_ns(const char *name_space, const char *name,
awk_value_t *value);
-This is like @code{sym_update()}, but the @code{name_space} parameter allows
you
-to specify which namespace @code{name} is part of. @code{name_space} cannot be
-@code{NULL}. If it is @code{""} or @code{"awk"}, then @code{name} is searched
-for in the default @code{awk} namespace.
-@end table
-
-An extension can look up the value of @command{gawk}'s special variables.
-However, with the exception of the @code{PROCINFO} array, an extension
-cannot change any of those variables.
-
-When searching for or updating variables outside the @code{awk} namespace
-(@pxref{Namespaces}), function and variable names must be simple
-identifiers.@footnote{Allowing both namespace plus identifier and
-@code{foo::bar} would have been too confusing to document, and to code
-and test.} In addition, namespace names and variable and function names
-must follow the rules given in @ref{Naming Rules}.
-
-@node Symbol table by cookie
-@subsubsection Variable Access and Update by Cookie
-
-A @dfn{scalar cookie} is an opaque handle that provides access
-to a global variable or array. It is an optimization that
-avoids looking up variables in @command{gawk}'s symbol table every time
-access is needed. This was discussed earlier, in @ref{General Data Types}.
-
-@need 1500
-The following functions let you work with scalar cookies:
-
-@table @code
-@item awk_bool_t sym_lookup_scalar(awk_scalar_t cookie,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t
wanted,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t
*result);
-Retrieve the current value of a scalar cookie.
-Once you have obtained a scalar cookie using @code{sym_lookup()}, you can
-use this function to get its value more efficiently.
-Return false if the value cannot be retrieved.
-
-@item awk_bool_t sym_update_scalar(awk_scalar_t cookie, awk_value_t *value);
-Update the value associated with a scalar cookie. Return false if
-the new value is not of type @code{AWK_STRING}, @code{AWK_STRNUM},
@code{AWK_REGEX}, or @code{AWK_NUMBER}.
-Here too, the predefined variables may not be updated.
-@end table
-
-It is not obvious at first glance how to work with scalar cookies or
-what their @i{raison d'@^etre} really is. In theory, the @code{sym_lookup()}
-and @code{sym_update()} routines are all you really need to work with
-variables. For example, you might have code that looks up the value of
-a variable, evaluates a condition, and then possibly changes the value
-of the variable based on the result of that evaluation, like so:
-
-@example
-/* do_magic --- do something really great */
-
-static awk_value_t *
-do_magic(int nargs, awk_value_t *result)
-@{
- awk_value_t value;
-
- if ( sym_lookup("MAGIC_VAR", AWK_NUMBER, & value)
- && some_condition(value.num_value)) @{
- value.num_value += 42;
- sym_update("MAGIC_VAR", & value);
- @}
-
- return make_number(0.0, result);
-@}
-@end example
-
-@noindent
-This code looks (and is) simple and straightforward. So what's the problem?
-
-Well, consider what happens if @command{awk}-level code associated
-with your extension calls the @code{magic()} function (implemented in
-C by @code{do_magic()}), once per record, while processing hundreds
-of thousands or millions of records. The @code{MAGIC_VAR} variable is
-looked up in the symbol table once or twice per function call!
-
-The symbol table lookup is really pure overhead; it is considerably
-more efficient to get a cookie that represents the variable, and use
-that to get the variable's value and update it as needed.@footnote{The
-difference is measurable and quite real. Trust us.}
-
-Thus, the way to use cookies is as follows. First, install
-your extension's variable in @command{gawk}'s symbol table using
-@code{sym_update()}, as usual. Then get a scalar cookie for the variable
-using @code{sym_lookup()}:
-
-@example
-@group
-static awk_scalar_t magic_var_cookie; /* cookie for MAGIC_VAR */
-
-static void
-my_extension_init()
-@{
- awk_value_t value;
-@end group
-
- /* install initial value */
- sym_update("MAGIC_VAR", make_number(42.0, & value));
-
- /* get the cookie */
- sym_lookup("MAGIC_VAR", AWK_SCALAR, & value);
-
- /* save the cookie */
- magic_var_cookie = value.scalar_cookie;
- @dots{}
-@}
-@end example
-
-Next, use the routines in this @value{SECTION} for retrieving and updating
-the value through the cookie. Thus, @code{do_magic()} now becomes
-something like this:
-
-@example
-/* do_magic --- do something really great */
-
-static awk_value_t *
-do_magic(int nargs, awk_value_t *result)
-@{
- awk_value_t value;
-
- if ( sym_lookup_scalar(magic_var_cookie, AWK_NUMBER, & value)
- && some_condition(value.num_value)) @{
- value.num_value += 42;
- sym_update_scalar(magic_var_cookie, & value);
- @}
- @dots{}
-
- return make_number(0.0, result);
-@}
-@end example
-
-@quotation NOTE
-The previous code omitted error checking for
-presentation purposes. Your extension code should be more robust
-and carefully check the return values from the API functions.
-@end quotation
-
-@node Cached values
-@subsubsection Creating and Using Cached Values
-
-The routines in this @value{SECTION} allow you to create and release
-cached values. Like scalar cookies, in theory, cached values
-are not necessary. You can create numbers and strings using
-the functions in @ref{Constructor Functions}. You can then
-assign those values to variables using @code{sym_update()}
-or @code{sym_update_scalar()}, as you like.
-
-However, you can understand the point of cached values if you remember that
-@emph{every} string value's storage @emph{must} come from @code{gawk_malloc()},
-@code{gawk_calloc()}, or @code{gawk_realloc()}.
-If you have 20 variables, all of which have the same string value, you
-must create 20 identical copies of the string.@footnote{Numeric values
-are clearly less problematic, requiring only a C @code{double} to store.
-But of course, GMP and MPFR values @emph{do} take up more memory.}
-
-It is clearly more efficient, if possible, to create a value once, and
-then tell @command{gawk} to reuse the value for multiple variables. That
-is what the routines in this @value{SECTION} let you do. The functions are as
follows:
-
-@table @code
-@item awk_bool_t create_value(awk_value_t *value, awk_value_cookie_t *result);
-Create a cached string or numeric value from @code{value} for
-efficient later assignment. Only values of type @code{AWK_NUMBER},
@code{AWK_REGEX}, @code{AWK_STRNUM},
-and @code{AWK_STRING} are allowed. Any other type is rejected.
-@code{AWK_UNDEFINED} could be allowed, but doing so would result in
-inferior performance.
-
-@item awk_bool_t release_value(awk_value_cookie_t vc);
-Release the memory associated with a value cookie obtained
-from @code{create_value()}.
-@end table
-
-You use value cookies in a fashion similar to the way you use scalar cookies.
-In the extension initialization routine, you create the value cookie:
-
-@example
-static awk_value_cookie_t answer_cookie; /* static value cookie */
-
-static void
-my_extension_init()
-@{
- awk_value_t value;
- char *long_string;
- size_t long_string_len;
-
- /* code from earlier */
- @dots{}
- /* @dots{} fill in long_string and long_string_len @dots{} */
- make_malloced_string(long_string, long_string_len, & value);
- create_value(& value, & answer_cookie); /* create cookie */
- @dots{}
-@}
-@end example
-
-Once the value is created, you can use it as the value of any number
-of variables:
-
-@example
-static awk_value_t *
-do_magic(int nargs, awk_value_t *result)
-@{
- awk_value_t new_value;
-
- @dots{} /* as earlier */
-
- value.val_type = AWK_VALUE_COOKIE;
- value.value_cookie = answer_cookie;
- sym_update("VAR1", & value);
- sym_update("VAR2", & value);
- @dots{}
- sym_update("VAR100", & value);
- @dots{}
-@}
-@end example
-
-@noindent
-Using value cookies in this way saves considerable storage, as all of
-@code{VAR1} through @code{VAR100} share the same value.
-
-You might be wondering, ``Is this sharing problematic?
-What happens if @command{awk} code assigns a new value to @code{VAR1};
-are all the others changed too?''
-
-That's a great question. The answer is that no, it's not a problem.
-Internally, @command{gawk} uses @dfn{reference-counted strings}. This means
-that many variables can share the same string value, and @command{gawk}
-keeps track of the usage. When a variable's value changes, @command{gawk}
-simply decrements the reference count on the old value and updates
-the variable to use the new value.
-
-Finally, as part of your cleanup action (@pxref{Exit Callback Functions})
-you should release any cached values that you created, using
-@code{release_value()}.
-
-@node Array Manipulation
-@subsection Array Manipulation
-@cindex array manipulation in extensions
-@cindex extensions @subentry loadable @subentry array manipulation in
-
-The primary data structure@footnote{OK, the only data structure.} in
@command{awk}
-is the associative array (@pxref{Arrays}).
-Extensions need to be able to manipulate @command{awk} arrays.
-The API provides a number of data structures for working with arrays,
-functions for working with individual elements, and functions for
-working with arrays as a whole. This includes the ability to
-``flatten'' an array so that it is easy for C code to traverse
-every element in an array. The array data structures integrate
-nicely with the data structures for values to make it easy to
-both work with and create true arrays of arrays (@pxref{General Data Types}).
-
-@menu
-* Array Data Types:: Data types for working with arrays.
-* Array Functions:: Functions for working with arrays.
-* Flattening Arrays:: How to flatten arrays.
-* Creating Arrays:: How to create and populate arrays.
-@end menu
-
-@node Array Data Types
-@subsubsection Array Data Types
-
-The data types associated with arrays are as follows:
-
-@table @code
-@item typedef void *awk_array_t;
-If you request the value of an array variable, you get back an
-@code{awk_array_t} value. This value is opaque@footnote{It is also
-a ``cookie,'' but the @command{gawk} developers did not wish to overuse this
-term.} to the extension; it uniquely identifies the array but can
-only be used by passing it into API functions or receiving it from API
-functions. This is very similar to way @samp{FILE *} values are used
-with the @code{<stdio.h>} library routines.
-
-@item typedef struct awk_element @{
-@itemx @ @ @ @ /* convenience linked list pointer, not used by gawk */
-@itemx @ @ @ @ struct awk_element *next;
-@itemx @ @ @ @ enum @{
-@itemx @ @ @ @ @ @ @ @ AWK_ELEMENT_DEFAULT = 0,@ @ /* set by gawk */
-@itemx @ @ @ @ @ @ @ @ AWK_ELEMENT_DELETE = 1@ @ @ @ /* set by extension */
-@itemx @ @ @ @ @} flags;
-@itemx @ @ @ @ awk_value_t index;
-@itemx @ @ @ @ awk_value_t value;
-@itemx @} awk_element_t;
-The @code{awk_element_t} is a ``flattened''
-array element. @command{awk} produces an array of these
-inside the @code{awk_flat_array_t} (see the next item).
-Individual elements may be marked for deletion. New elements must be added
-individually, one at a time, using the separate API for that purpose.
-The fields are as follows:
-
-@c nested table
-@table @code
-@item struct awk_element *next;
-This pointer is for the convenience of extension writers. It allows
-an extension to create a linked list of new elements that can then be
-added to an array in a loop that traverses the list.
-
-@item enum @{ @dots{} @} flags;
-A set of flag values that convey information between the extension
-and @command{gawk}. Currently there is only one: @code{AWK_ELEMENT_DELETE}.
-Setting it causes @command{gawk} to delete the
-element from the original array upon release of the flattened array.
-
-@item index
-@itemx value
-The index and value of the element, respectively.
-@emph{All} memory pointed to by @code{index} and @code{value} belongs to
@command{gawk}.
-@end table
-
-@item typedef struct awk_flat_array @{
-@itemx @ @ @ @ awk_const void *awk_const opaque1;@ @ @ @ /* for use by gawk */
-@itemx @ @ @ @ awk_const void *awk_const opaque2;@ @ @ @ /* for use by gawk */
-@itemx @ @ @ @ awk_const size_t count;@ @ @ @ @ /* how many elements */
-@itemx @ @ @ @ awk_element_t elements[1];@ @ /* will be extended */
-@itemx @} awk_flat_array_t;
-This is a flattened array. When an extension gets one of these
-from @command{gawk}, the @code{elements} array is of actual
-size @code{count}.
-The @code{opaque1} and @code{opaque2} pointers are for use by @command{gawk};
-therefore they are marked @code{awk_const} so that the extension cannot
-modify them.
-@end table
-
-@node Array Functions
-@subsubsection Array Functions
-
-The following functions relate to individual array elements:
-
-@table @code
-@item awk_bool_t get_element_count(awk_array_t a_cookie, size_t *count);
-For the array represented by @code{a_cookie}, place in @code{*count}
-the number of elements it contains. A subarray counts as a single element.
-Return false if there is an error.
-
-@item awk_bool_t get_array_element(awk_array_t a_cookie,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const
awk_value_t *const index,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t
wanted,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t
*result);
-For the array represented by @code{a_cookie}, return in @code{*result}
-the value of the element whose index is @code{index}.
-@code{wanted} specifies the type of value you wish to retrieve.
-Return false if @code{wanted} does not match the actual type or if
-@code{index} is not in the array (@pxref{table-value-types-returned}).
-
-The value for @code{index} can be numeric, in which case @command{gawk}
-converts it to a string. Using nonintegral values is possible, but
-requires that you understand how such values are converted to strings
-(@pxref{Conversion}); thus, using integral values is safest.
-
-As with @emph{all} strings passed into @command{gawk} from an extension,
-the string value of @code{index} must come from @code{gawk_malloc()},
-@code{gawk_calloc()}, or @code{gawk_realloc()}, and
-@command{gawk} releases the storage.
-
-@item awk_bool_t set_array_element(awk_array_t a_cookie,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const@
awk_value_t *const index,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const@
awk_value_t *const value);
-In the array represented by @code{a_cookie}, create or modify
-the element whose index is given by @code{index}.
-The @code{ARGV} and @code{ENVIRON} arrays may not be changed,
-although the @code{PROCINFO} array can be.
-
-@item awk_bool_t set_array_element_by_elem(awk_array_t a_cookie,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
@ awk_element_t element);
-Like @code{set_array_element()}, but take the @code{index} and @code{value}
-from @code{element}. This is a convenience macro.
-
-@item awk_bool_t del_array_element(awk_array_t a_cookie,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const
awk_value_t* const index);
-Remove the element with the given index from the array
-represented by @code{a_cookie}.
-Return true if the element was removed, or false if the element did
-not exist in the array.
-@end table
-
-The following functions relate to arrays as a whole:
-
-@table @code
-@item awk_array_t create_array(void);
-Create a new array to which elements may be added.
-@xref{Creating Arrays} for a discussion of how to
-create a new array and add elements to it.
-
-@item awk_bool_t clear_array(awk_array_t a_cookie);
-Clear the array represented by @code{a_cookie}.
-Return false if there was some kind of problem, true otherwise.
-The array remains an array, but after calling this function, it
-has no elements. This is equivalent to using the @code{delete}
-statement (@pxref{Delete}).
-
-@item awk_bool_t destroy_array(awk_array_t a_cookie);
-Clear the array represented by @code{a_cookie} and release the array
-allocated by @code{create_array}.
-Return false if there was some kind of problem, true otherwise.
-The array will no longer exist and cannot be used again.
-
-@item awk_bool_t flatten_array_typed(awk_array_t a_cookie,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
awk_flat_array_t **data,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
awk_valtype_t index_type,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
awk_valtype_t value_type);
-For the array represented by @code{a_cookie}, create an @code{awk_flat_array_t}
-structure and fill it in with indices and values of the requested types.
-Set the pointer whose address is passed as @code{data}
-to point to this structure.
-Return true upon success, or false otherwise.
-@ifset FOR_PRINT
-See the next @value{SECTION}
-@end ifset
-@ifclear FOR_PRINT
-@xref{Flattening Arrays},
-@end ifclear
-for a discussion of how to
-flatten an array and work with it.
-
-@item awk_bool_t flatten_array(awk_array_t a_cookie, awk_flat_array_t **data);
-For the array represented by @code{a_cookie}, create an @code{awk_flat_array_t}
-structure and fill it in with @code{AWK_STRING} indices and
-@code{AWK_UNDEFINED} values.
-This is superseded by @code{flatten_array_typed()}.
-It is provided as a macro, and remains for convenience and for source code
-compatibility with the previous version of the API.
-
-@item awk_bool_t release_flattened_array(awk_array_t a_cookie,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
awk_flat_array_t *data);
-When done with a flattened array, release the storage using this function.
-You must pass in both the original array cookie and the address of
-the created @code{awk_flat_array_t} structure.
-The function returns true upon success, false otherwise.
-@end table
-
-@node Flattening Arrays
-@subsubsection Working With All The Elements of an Array
-
-To @dfn{flatten} an array is to create a structure that
-represents the full array in a fashion that makes it easy
-for C code to traverse the entire array. Some of the code
-in @file{extension/testext.c} does this, and also serves
-as a nice example showing how to use the APIs.
-
-We walk through that part of the code one step at a time.
-First, the @command{gawk} script that drives the test extension:
-
-@example
-@@load "testext"
-BEGIN @{
- n = split("blacky rusty sophie raincloud lucky", pets)
- printf("pets has %d elements\n", length(pets))
- ret = dump_array_and_delete("pets", "3")
- printf("dump_array_and_delete(pets) returned %d\n", ret)
- if ("3" in pets)
- printf("dump_array_and_delete() did NOT remove index \"3\"!\n")
- else
- printf("dump_array_and_delete() did remove index \"3\"!\n")
- print ""
-@}
-@end example
-
-@noindent
-This code creates an array with @code{split()} (@pxref{String Functions})
-and then calls @code{dump_array_and_delete()}. That function looks up
-the array whose name is passed as the first argument, and
-deletes the element at the index passed in the second argument.
-The @command{awk} code then prints the return value and checks if the element
-was indeed deleted. Here is the C code that implements
-@code{dump_array_and_delete()}. It has been edited slightly for
-presentation.
-
-The first part declares variables, sets up the default
-return value in @code{result}, and checks that the function
-was called with the correct number of arguments:
-
-@example
-static awk_value_t *
-dump_array_and_delete(int nargs, awk_value_t *result)
-@{
- awk_value_t value, value2, value3;
- awk_flat_array_t *flat_array;
- size_t count;
- char *name;
- int i;
-
- assert(result != NULL);
- make_number(0.0, result);
-
- if (nargs != 2) @{
- printf("dump_array_and_delete: nargs not right "
- "(%d should be 2)\n", nargs);
- goto out;
- @}
-@end example
-
-The function then proceeds in steps, as follows. First, retrieve
-the name of the array, passed as the first argument, followed by
-the array itself. If either operation fails, print an
-error message and return:
-
-@example
- /* get argument named array as flat array and print it */
- if (get_argument(0, AWK_STRING, & value)) @{
- name = value.str_value.str;
- if (sym_lookup(name, AWK_ARRAY, & value2))
- printf("dump_array_and_delete: sym_lookup of %s passed\n",
- name);
- else @{
- printf("dump_array_and_delete: sym_lookup of %s failed\n",
- name);
- goto out;
- @}
- @} else @{
- printf("dump_array_and_delete: get_argument(0) failed\n");
- goto out;
- @}
-@end example
-
-For testing purposes and to make sure that the C code sees
-the same number of elements as the @command{awk} code,
-the second step is to get the count of elements in the array
-and print it:
-
-@example
- if (! get_element_count(value2.array_cookie, & count)) @{
- printf("dump_array_and_delete: get_element_count failed\n");
- goto out;
- @}
-
- printf("dump_array_and_delete: incoming size is %lu\n",
- (unsigned long) count);
-@end example
-
-The third step is to actually flatten the array, and then
-to double-check that the count in the @code{awk_flat_array_t}
-is the same as the count just retrieved:
-
-@example
- if (! flatten_array_typed(value2.array_cookie, & flat_array,
- AWK_STRING, AWK_UNDEFINED)) @{
- printf("dump_array_and_delete: could not flatten array\n");
- goto out;
- @}
-
- if (flat_array->count != count) @{
- printf("dump_array_and_delete: flat_array->count (%lu)"
- " != count (%lu)\n",
- (unsigned long) flat_array->count,
- (unsigned long) count);
- goto out;
- @}
-@end example
-
-The fourth step is to retrieve the index of the element
-to be deleted, which was passed as the second argument.
-Remember that argument counts passed to @code{get_argument()}
-are zero-based, and thus the second argument is numbered one:
-
-@example
- if (! get_argument(1, AWK_STRING, & value3)) @{
- printf("dump_array_and_delete: get_argument(1) failed\n");
- goto out;
- @}
-@end example
-
-The fifth step is where the ``real work'' is done. The function
-loops over every element in the array, printing the index and
-element values. In addition, upon finding the element with the
-index that is supposed to be deleted, the function sets the
-@code{AWK_ELEMENT_DELETE} bit in the @code{flags} field
-of the element. When the array is released, @command{gawk}
-traverses the flattened array, and deletes any elements that
-have this flag bit set:
-
-@example
- for (i = 0; i < flat_array->count; i++) @{
- printf("\t%s[\"%.*s\"] = %s\n",
- name,
- (int) flat_array->elements[i].index.str_value.len,
- flat_array->elements[i].index.str_value.str,
- valrep2str(& flat_array->elements[i].value));
-
- if (strcmp(value3.str_value.str,
- flat_array->elements[i].index.str_value.str) == 0) @{
- flat_array->elements[i].flags |= AWK_ELEMENT_DELETE;
- printf("dump_array_and_delete: marking element \"%s\" "
- "for deletion\n",
- flat_array->elements[i].index.str_value.str);
- @}
- @}
-@end example
-
-The sixth step is to release the flattened array. This tells
-@command{gawk} that the extension is no longer using the array,
-and that it should delete any elements marked for deletion.
-@command{gawk} also frees any storage that was allocated,
-so you should not use the pointer (@code{flat_array} in this
-code) once you have called @code{release_flattened_array()}:
-
-@example
- if (! release_flattened_array(value2.array_cookie, flat_array)) @{
- printf("dump_array_and_delete: could not release flattened array\n");
- goto out;
- @}
-@end example
-
-Finally, because everything was successful, the function sets the
-return value to success, and returns:
-
-@example
-@group
- make_number(1.0, result);
-out:
- return result;
-@}
-@end group
-@end example
-
-Here is the output from running this part of the test:
-
-@example
-pets has 5 elements
-dump_array_and_delete: sym_lookup of pets passed
-dump_array_and_delete: incoming size is 5
- pets["1"] = "blacky"
- pets["2"] = "rusty"
- pets["3"] = "sophie"
-dump_array_and_delete: marking element "3" for deletion
- pets["4"] = "raincloud"
- pets["5"] = "lucky"
-dump_array_and_delete(pets) returned 1
-dump_array_and_delete() did remove index "3"!
-@end example
-
-@node Creating Arrays
-@subsubsection How To Create and Populate Arrays
-
-Besides working with arrays created by @command{awk} code, you can
-create arrays and populate them as you see fit, and then @command{awk}
-code can access them and manipulate them.
-
-There are two important points about creating arrays from extension code:
-
-@itemize @value{BULLET}
-@item
-You must install a new array into @command{gawk}'s symbol
-table immediately upon creating it. Once you have done so,
-you can then populate the array.
-
-@ignore
-Strictly speaking, this is required only
-for arrays that will have subarrays as elements; however it is
-a good idea to always do this. This restriction may be relaxed
-in a subsequent revision of the API.
-@end ignore
-
-Similarly, if installing a new array as a subarray of an existing array,
-you must add the new array to its parent before adding any elements to it.
-
-Thus, the correct way to build an array is to work ``top down.'' Create
-the array, and immediately install it in @command{gawk}'s symbol table
-using @code{sym_update()}, or install it as an element in a previously
-existing array using @code{set_array_element()}. We show example code shortly.
-
-@item
-Due to @command{gawk} internals, after using @code{sym_update()} to install an
array
-into @command{gawk}, you have to retrieve the array cookie from the value
-passed in to @command{sym_update()} before doing anything else with it, like
so:
-
-@example
-awk_value_t val;
-awk_array_t new_array;
-
-new_array = create_array();
-val.val_type = AWK_ARRAY;
-val.array_cookie = new_array;
-
-/* install array in the symbol table */
-sym_update("array", & val);
-
-new_array = val.array_cookie; /* YOU MUST DO THIS */
-@end example
-
-If installing an array as a subarray, you must also retrieve the value
-of the array cookie after the call to @code{set_element()}.
-@end itemize
-
-The following C code is a simple test extension to create an array
-with two regular elements and with a subarray. The leading @code{#include}
-directives and boilerplate variable declarations
-(@pxref{Extension API Boilerplate})
-are omitted for brevity.
-The first step is to create a new array and then install it
-in the symbol table:
-
-@example
-@ignore
-#ifdef HAVE_CONFIG_H
-#include <config.h>
-#endif
-
-#include <stdio.h>
-#include <assert.h>
-#include <errno.h>
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-
-#include <sys/types.h>
-#include <sys/stat.h>
-
-#include "gawkapi.h"
-
-static const gawk_api_t *api; /* for convenience macros to work */
-static awk_ext_id_t ext_id;
-static const char *ext_version = "testarray extension: version 1.0";
-
-int plugin_is_GPL_compatible;
-
-@end ignore
-/* create_new_array --- create a named array */
-
-static void
-create_new_array()
-@{
- awk_array_t a_cookie;
- awk_array_t subarray;
- awk_value_t index, value;
-
- a_cookie = create_array();
- value.val_type = AWK_ARRAY;
- value.array_cookie = a_cookie;
-
- if (! sym_update("new_array", & value))
- printf("create_new_array: sym_update(\"new_array\") failed!\n");
- a_cookie = value.array_cookie;
-@end example
-
-@noindent
-Note how @code{a_cookie} is reset from the @code{array_cookie} field in
-the @code{value} structure.
-
-The second step is to install two regular values into @code{new_array}:
-
-@example
- (void) make_const_string("hello", 5, & index);
- (void) make_const_string("world", 5, & value);
- if (! set_array_element(a_cookie, & index, & value)) @{
- printf("fill_in_array: set_array_element failed\n");
- return;
- @}
-
- (void) make_const_string("answer", 6, & index);
- (void) make_number(42.0, & value);
- if (! set_array_element(a_cookie, & index, & value)) @{
- printf("fill_in_array: set_array_element failed\n");
- return;
- @}
-@end example
-
-The third step is to create the subarray and install it:
-
-@example
- (void) make_const_string("subarray", 8, & index);
- subarray = create_array();
- value.val_type = AWK_ARRAY;
- value.array_cookie = subarray;
- if (! set_array_element(a_cookie, & index, & value)) @{
- printf("fill_in_array: set_array_element failed\n");
- return;
- @}
- subarray = value.array_cookie;
-@end example
-
-The final step is to populate the subarray with its own element:
-
-@example
- (void) make_const_string("foo", 3, & index);
- (void) make_const_string("bar", 3, & value);
- if (! set_array_element(subarray, & index, & value)) @{
- printf("fill_in_array: set_array_element failed\n");
- return;
- @}
-@}
-@ignore
-static awk_ext_func_t func_table[] = @{
- @{ NULL, NULL, 0 @}
-@};
-
-/* init_testarray --- additional initialization function */
-
-static awk_bool_t init_testarray(void)
-@{
- create_new_array();
-
- return awk_true;
-@}
-
-static awk_bool_t (*init_func)(void) = init_testarray;
-
-dl_load_func(func_table, testarray, "")
-@end ignore
-@end example
-
-Here is a sample script that loads the extension
-and then dumps the array:
-
-@example
-@@load "subarray"
-
-function dumparray(name, array, i)
-@{
- for (i in array)
- if (isarray(array[i]))
- dumparray(name "[\"" i "\"]", array[i])
- else
- printf("%s[\"%s\"] = %s\n", name, i, array[i])
-@}
-
-BEGIN @{
- dumparray("new_array", new_array);
-@}
-@end example
-
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-Here is the result of running the script:
-
-@example
-$ @kbd{AWKLIBPATH=$PWD gawk -f subarray.awk}
-@print{} new_array["subarray"]["foo"] = bar
-@print{} new_array["hello"] = world
-@print{} new_array["answer"] = 42
-@end example
-
-@noindent
-(@xref{Finding Extensions} for more information on the
-@env{AWKLIBPATH} environment variable.)
-
-@node Redirection API
-@subsection Accessing and Manipulating Redirections
-
-The following function allows extensions to access and manipulate redirections.
-
-@table @code
-@item awk_bool_t get_file(const char *name,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ size_t name_len,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const char *filetype,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ int fd,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_input_buf_t **ibufp,
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_output_buf_t **obufp);
-Look up file @code{name} in @command{gawk}'s internal redirection table.
-If @code{name} is @code{NULL} or @code{name_len} is zero, return
-data for the currently open input file corresponding to @code{FILENAME}.
-(This does not access the @code{filetype} argument, so that may be undefined).
-If the file is not already open, attempt to open it.
-The @code{filetype} argument must be zero-terminated and should be one of:
-
-@table @code
-@item ">"
-A file opened for output.
-
-@item ">>"
-A file opened for append.
-
-@item "<"
-A file opened for input.
-
-@item "|>"
-A pipe opened for output.
-
-@item "|<"
-A pipe opened for input.
-
-@item "|&"
-A two-way coprocess.
-@end table
-
-On error, return @code{awk_false}. Otherwise, return
-@code{awk_true}, and return additional information about the redirection
-in the @code{ibufp} and @code{obufp} pointers.
-
-For input redirections, the @code{*ibufp} value should be non-@code{NULL},
-and @code{*obufp} should be @code{NULL}. For output redirections,
-the @code{*obufp} value should be non-@code{NULL}, and @code{*ibufp}
-should be @code{NULL}. For two-way coprocesses, both values should
-be non-@code{NULL}.
-
-In the usual case, the extension is interested in @code{(*ibufp)->fd}
-and/or @code{fileno((*obufp)->fp)}. If the file is not already
-open, and the @code{fd} argument is nonnegative, @command{gawk}
-will use that file descriptor instead of opening the file in the
-usual way. If @code{fd} is nonnegative, but the file exists already,
-@command{gawk} ignores @code{fd} and returns the existing file. It is
-the caller's responsibility to notice that neither the @code{fd} in
-the returned @code{awk_input_buf_t} nor the @code{fd} in the returned
-@code{awk_output_buf_t} matches the requested value.
-
-Note that supplying a file descriptor is currently @emph{not} supported
-for pipes. However, supplying a file descriptor should work for input,
-output, append, and two-way (coprocess) sockets. If @code{filetype}
-is two-way, @command{gawk} assumes that it is a socket! Note that in
-the two-way case, the input and output file descriptors may differ.
-To check for success, you must check whether either matches.
-@end table
-
-It is anticipated that this API function will be used to implement I/O
-multiplexing and a socket library.
-
-@node Extension API Variables
-@subsection API Variables
-
-The API provides two sets of variables. The first provides information
-about the version of the API (both with which the extension was compiled,
-and with which @command{gawk} was compiled). The second provides
-information about how @command{gawk} was invoked.
-
-@menu
-* Extension Versioning:: API Version information.
-* Extension GMP/MPFR Versioning:: Version information about GMP and MPFR.
-* Extension API Informational Variables:: Variables providing information about
- @command{gawk}'s invocation.
-@end menu
-
-@node Extension Versioning
-@subsubsection API Version Constants and Variables
-@cindex API @subentry version
-@cindex extension API @subentry version number
-
-The API provides both a ``major'' and a ``minor'' version number.
-The API versions are available at compile time as C preprocessor defines
-to support conditional compilation, and as enum constants to facilitate
-debugging:
-
-@float Table,gawk-api-version
-@caption{gawk API version constants}
-@multitable {@b{API Version}} {@code{gawk_api_major_version}}
{@code{GAWK_API_MAJOR_VERSION}}
-@headitem API Version @tab C Preprocessor Define @tab enum constant
-@item Major @tab @code{gawk_api_major_version} @tab
@code{GAWK_API_MAJOR_VERSION}
-@item Minor @tab @code{gawk_api_minor_version} @tab
@code{GAWK_API_MINOR_VERSION}
-@end multitable
-@end float
-
-The minor version increases when new functions are added to the API. Such
-new functions are always added to the end of the API @code{struct}.
-
-The major version increases (and the minor version is reset to zero) if any
-of the data types change size or member order, or if any of the existing
-functions change signature.
-
-It could happen that an extension may be compiled against one version
-of the API but loaded by a version of @command{gawk} using a different
-version. For this reason, the major and minor API versions of the
-running @command{gawk} are included in the API @code{struct} as read-only
-constant integers:
-
-@table @code
-@item api->major_version
-The major version of the running @command{gawk}.
-
-@item api->minor_version
-The minor version of the running @command{gawk}.
-@end table
-
-It is up to the extension to decide if there are API incompatibilities.
-Typically, a check like this is enough:
-
-@example
-if ( api->major_version != GAWK_API_MAJOR_VERSION
- || api->minor_version < GAWK_API_MINOR_VERSION) @{
- fprintf(stderr, "foo_extension: version mismatch with gawk!\n");
- fprintf(stderr, "\tmy version (%d, %d), gawk version (%d, %d)\n",
- GAWK_API_MAJOR_VERSION, GAWK_API_MINOR_VERSION,
- api->major_version, api->minor_version);
- exit(1);
-@}
-@end example
-
-Such code is included in the boilerplate @code{dl_load_func()} macro
-provided in @file{gawkapi.h} (discussed in
-@ref{Extension API Boilerplate}).
-
-@node Extension GMP/MPFR Versioning
-@subsubsection GMP and MPFR Version Information
-
-The API also includes information about the versions of GMP and MPFR
-with which the running @command{gawk} was compiled (if any).
-They are included in the API @code{struct} as read-only
-constant integers:
-
-@table @code
-@item api->gmp_major_version
-The major version of the GMP library used to compile @command{gawk}.
-
-@item api->gmp_minor_version
-The minor version of the GMP library used to compile @command{gawk}.
-
-@item api->mpfr_major_version
-The major version of the MPFR library used to compile @command{gawk}.
-
-@item api->mpfr_minor_version
-The minor version of the MPFR library used to compile @command{gawk}.
-@end table
-
-These fields are set to zero if @command{gawk} was compiled without
-MPFR support.
-
-You can check if the versions of MPFR and GMP that you are using match those
-of @command{gawk} with the following macro:
-
-@table @code
-@item check_mpfr_version(extension)
-The @code{extension} is the extension id passed to all the other macros
-and functions defined in @file{gawkapi.h}. If you have not included
-the @code{<mpfr.h>} header file, then this macro will be defined to do nothing.
-
-If you have included that file, then this macro compares the MPFR
-and GMP major and minor versions against those of the library you are
-compiling against. If your libraries are newer than @command{gawk}'s, it
-produces a fatal error message.
-
-The @code{dl_load_func()} macro (@pxref{Extension API Boilerplate})
-calls @code{check_mpfr_version()}.
-@end table
-
-@node Extension API Informational Variables
-@subsubsection Informational Variables
-@cindex API @subentry informational variables
-@cindex extension API @subentry informational variables
-
-The API provides access to several variables that describe
-whether the corresponding command-line options were enabled when
-@command{gawk} was invoked. The variables are:
-
-@table @code
-@item do_csv
-This variable is true if @command{gawk} was invoked with @option{--csv} option.
-
-@item do_debug
-This variable is true if @command{gawk} was invoked with @option{--debug}
option.
-
-@item do_lint
-This variable is true if @command{gawk} was invoked with @option{--lint}
option.
-
-@item do_mpfr
-This variable is true if @command{gawk} was invoked with @option{--bignum}
option.
-
-@item do_profile
-This variable is true if @command{gawk} was invoked with @option{--profile}
option.
-
-@item do_sandbox
-This variable is true if @command{gawk} was invoked with @option{--sandbox}
option.
-
-@item do_traditional
-This variable is true if @command{gawk} was invoked with
@option{--traditional} option.
-@end table
-
-The value of @code{do_lint} can change if @command{awk} code
-modifies the @code{LINT} predefined variable (@pxref{Built-in Variables}).
-The others should not change during execution.
-
-@node Extension API Boilerplate
-@subsection Boilerplate Code
-
-As mentioned earlier (@pxref{Extension Mechanism Outline}), the function
-definitions as presented are really macros. To use these macros, your
-extension must provide a small amount of boilerplate code (variables and
-functions) toward the top of your source file, using predefined names
-as described here. The boilerplate needed is also provided in comments
-in the @file{gawkapi.h} header file:
-
-@example
-@group
-/* Boilerplate code: */
-int plugin_is_GPL_compatible;
-
-static gawk_api_t *const api;
-@end group
-static awk_ext_id_t ext_id;
-static const char *ext_version = NULL; /* or @dots{} = "some string" */
-
-static awk_ext_func_t func_table[] = @{
- @{ "name", do_name, 1, 0, awk_false, NULL @},
- /* @dots{} */
-@};
-
-/* EITHER: */
-
-static awk_bool_t (*init_func)(void) = NULL;
-
-/* OR: */
-
-static awk_bool_t
-init_my_extension(void)
-@{
- @dots{}
-@}
-
-static awk_bool_t (*init_func)(void) = init_my_extension;
-
-dl_load_func(func_table, some_name, "name_space_in_quotes")
-@end example
-
-These variables and functions are as follows:
-
-@table @code
-@item int plugin_is_GPL_compatible;
-This asserts that the extension is compatible with
-@ifclear FOR_PRINT
-the GNU GPL (@pxref{Copying}).
-@end ifclear
-@ifset FOR_PRINT
-the GNU GPL.
-@end ifset
-If your extension does not have this, @command{gawk}
-will not load it (@pxref{Plugin License}).
-
-@item static gawk_api_t *const api;
-This global @code{static} variable should be set to point to
-the @code{gawk_api_t} pointer that @command{gawk} passes to your
-@code{dl_load()} function. This variable is used by all of the macros.
-
-@item static awk_ext_id_t ext_id;
-This global static variable should be set to the @code{awk_ext_id_t}
-value that @command{gawk} passes to your @code{dl_load()} function.
-This variable is used by all of the macros.
-
-@item static const char *ext_version = NULL; /* or @dots{} = "some string" */
-This global @code{static} variable should be set either
-to @code{NULL}, or to point to a string giving the name and version of
-your extension.
-
-@item static awk_ext_func_t func_table[] = @{ @dots{} @};
-This is an array of one or more @code{awk_ext_func_t} structures,
-as described earlier (@pxref{Extension Functions}).
-It can then be looped over for multiple calls to
-@code{add_ext_func()}.
-
-@c Use @var{OR} for docbook
-@item static awk_bool_t (*init_func)(void) = NULL;
-@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @var{OR}
-@itemx static awk_bool_t init_my_extension(void) @{ @dots{} @}
-@itemx static awk_bool_t (*init_func)(void) = init_my_extension;
-If you need to do some initialization work, you should define a
-function that does it (creates variables, opens files, etc.)
-and then define the @code{init_func} pointer to point to your
-function.
-The function should return @code{awk_false} upon failure, or @code{awk_true}
-if everything goes well.
-
-If you don't need to do any initialization, define the pointer and
-initialize it to @code{NULL}.
-
-@item dl_load_func(func_table, some_name, "name_space_in_quotes")
-This macro expands to a @code{dl_load()} function that performs
-all the necessary initializations.
-@end table
-
-The point of all the variables and arrays is to let the
-@code{dl_load()} function (from the @code{dl_load_func()}
-macro) do all the standard work. It does the following:
-
-@enumerate 1
-@item
-Check the API versions. If the extension major version does not match
-@command{gawk}'s, or if the extension minor version is greater than
-@command{gawk}'s, it prints a fatal error message and exits.
-
-@item
-Check the MPFR and GMP versions. If there is a mismatch, it prints
-a fatal error message and exits.
-
-@item
-Load the functions defined in @code{func_table}.
-If any of them fails to load, it prints a warning message but
-continues on.
-
-@item
-If the @code{init_func} pointer is not @code{NULL}, call the
-function it points to. If it returns @code{awk_false}, print a
-warning message.
-
-@item
-If @code{ext_version} is not @code{NULL}, register
-the version string with @command{gawk}.
-@end enumerate
-
-
-@node Changes from API V1
-@subsection Changes From Version 1 of the API
-
-The current API is @emph{not} binary compatible with version 1 of the API.
-You will have to recompile your extensions in order to use them with
-the current version of @command{gawk}.
-
-Fortunately, at the possible expense of some compile-time warnings, the API
remains
-source-code--compatible with the previous API. The major differences are
-the additional members in the @code{awk_ext_func_t} structure, and the
-addition of the third argument to the C implementation function
-(@pxref{Extension Functions}).
-
-Here is a list of individual features that changed from version 1 to
-version 2 of the API:
-
-@itemize @bullet
-
-@item
-Numeric values can now have MPFR/MPZ variants
-(@pxref{General Data Types}).
-
-@item
-There are new string types: @code{AWK_REGEX} and @code{AWK_STRNUM}
-(@pxref{General Data Types}).
-
-@item
-The @code{ezalloc()} macro is new
-(@pxref{Memory Allocation Functions}).
-
-@item
-The @code{awk_ext_func_t} structure changed. Instead of
-@code{num_expected_args}, it now has @code{max_expected} and
-@code{min_required}
-(@pxref{Extension Functions}).
-
-@item
-For @code{get_record()}, an input parser can now specify field widths
-(@pxref{Input Parsers}).
-
-@item
-Extensions can now produce nonfatal error messages
-(@pxref{Printing Messages}).
-
-@item
-When flattening an array, you can now specify the index and value types
-(@pxref{Array Functions}).
-
-@item
-The @code{get_file()} API is new
-(@pxref{Redirection API}).
-@end itemize
-
-@node Finding Extensions
-@section How @command{gawk} Finds Extensions
-@cindex extensions @subentry loadable @subentry search path
-@cindex finding extensions
-
-Compiled extensions have to be installed in a directory where
-@command{gawk} can find them. If @command{gawk} is configured and
-built in the default fashion, the directory in which to find
-extensions is @file{/usr/local/lib/gawk}. You can also specify a search
-path with a list of directories to search for compiled extensions.
-@xref{AWKLIBPATH Variable} for more information.
-
-@node Extension Example
-@section Example: Some File Functions
-@cindex extensions @subentry loadable @subentry example
-
-@quotation
-@i{No matter where you go, there you are.}
-@author Buckaroo Banzai
-@end quotation
-
-@c It's enough to show chdir and stat, no need for fts
-
-Two useful functions that are not in @command{awk} are @code{chdir()} (so
-that an @command{awk} program can change its directory) and @code{stat()}
-(so that an @command{awk} program can gather information about a file).
-In order to illustrate the API in action, this @value{SECTION} implements
-these functions for @command{gawk} in an extension.
-
-@menu
-* Internal File Description:: What the new functions will do.
-* Internal File Ops:: The code for internal file operations.
-* Using Internal File Ops:: How to use an external extension.
-@end menu
-
-@node Internal File Description
-@subsection Using @code{chdir()} and @code{stat()}
-
-This @value{SECTION} shows how to use the new functions at
-the @command{awk} level once they've been integrated into the
-running @command{gawk} interpreter. Using @code{chdir()} is very
-straightforward. It takes one argument, the new directory to change to:
-
-@example
-@@load "filefuncs"
-@dots{}
-newdir = "/home/arnold/funstuff"
-ret = chdir(newdir)
-if (ret < 0) @{
- printf("could not change to %s: %s\n", newdir, ERRNO) > "/dev/stderr"
- exit 1
-@}
-@dots{}
-@end example
-
-The return value is negative if the @code{chdir()} failed, and
-@code{ERRNO} (@pxref{Built-in Variables}) is set to a string indicating
-the error.
-
-Using @code{stat()} is a bit more complicated. The C @code{stat()}
-function fills in a structure that has a fair amount of information.
-The right way to model this in @command{awk} is to fill in an associative
-array with the appropriate information:
-
-@c broke printf for page breaking
-@example
-file = "/home/arnold/.profile"
-ret = stat(file, fdata)
-if (ret < 0) @{
- printf("could not stat %s: %s\n",
- file, ERRNO) > "/dev/stderr"
- exit 1
-@}
-printf("size of %s is %d bytes\n", file, fdata["size"])
-@end example
-
-The @code{stat()} function always clears the data array, even if
-the @code{stat()} fails. It fills in the following elements:
-
-@table @code
-@item "name"
-The name of the file that was @code{stat()}ed.
-
-@item "dev"
-@itemx "ino"
-The file's device and inode numbers, respectively.
-
-@item "mode"
-The file's mode, as a numeric value. This includes both the file's
-type and its permissions.
-
-@item "nlink"
-The number of hard links (directory entries) the file has.
-
-@item "uid"
-@itemx "gid"
-The numeric user and group ID numbers of the file's owner.
-
-@item "size"
-The size in bytes of the file.
-
-@item "blocks"
-The number of disk blocks the file actually occupies. This may not
-be a function of the file's size if the file has holes.
-
-@item "atime"
-@itemx "mtime"
-@itemx "ctime"
-The file's last access, modification, and inode update times,
-respectively. These are numeric timestamps, suitable for formatting
-with @code{strftime()}
-(@pxref{Time Functions}).
-
-@item "pmode"
-The file's ``printable mode.'' This is a string representation of
-the file's type and permissions, such as is produced by
-@samp{ls -l}---for example, @code{"drwxr-xr-x"}.
-
-@item "type"
-A printable string representation of the file's type. The value
-is one of the following:
-
-@table @code
-@item "blockdev"
-@itemx "chardev"
-The file is a block or character device (``special file'').
-
-@ignore
-@item "door"
-The file is a Solaris ``door'' (special file used for
-interprocess communications).
-@end ignore
-
-@item "directory"
-The file is a directory.
-
-@item "fifo"
-The file is a named pipe (also known as a FIFO).
-
-@item "file"
-The file is just a regular file.
-
-@item "socket"
-The file is an @code{AF_UNIX} (``Unix domain'') socket in the
-filesystem.
-
-@item "symlink"
-The file is a symbolic link.
-@end table
-
-@c 5/2013: Thanks to Corinna Vinschen for this information.
-@item "devbsize"
-The size of a block for the element indexed by @code{"blocks"}.
-This information is derived from either the @code{DEV_BSIZE}
-constant defined in @code{<sys/param.h>} on most systems,
-or the @code{S_BLKSIZE} constant in @code{<sys/stat.h>} on BSD systems.
-For some other systems, @dfn{a priori} knowledge is used to provide
-a value. Where no value can be determined, it defaults to 512.
-@end table
-
-Several additional elements may be present, depending upon the operating
-system and the type of the file. You can test for them in your @command{awk}
-program by using the @code{in} operator
-(@pxref{Reference to Elements}):
-
-@table @code
-@item "blksize"
-The preferred block size for I/O to the file. This field is not
-present on all POSIX-like systems in the C @code{stat} structure.
-
-@item "linkval"
-If the file is a symbolic link, this element is the name of the
-file the link points to (i.e., the value of the link).
-
-@item "rdev"
-@itemx "major"
-@itemx "minor"
-If the file is a block or character device file, then these values
-represent the numeric device number and the major and minor components
-of that number, respectively.
-@end table
-
-@node Internal File Ops
-@subsection C Code for @code{chdir()} and @code{stat()}
-
-Here is the C code for these extensions.@footnote{This version is
-edited slightly for presentation. See @file{extension/filefuncs.c}
-in the @command{gawk} distribution for the complete version.}
-
-The file includes a number of standard header files, and then includes
-the @file{gawkapi.h} header file, which provides the API definitions.
-Those are followed by the necessary variable declarations
-to make use of the API macros and boilerplate code
-(@pxref{Extension API Boilerplate}):
-
-@example
-#ifdef HAVE_CONFIG_H
-#include <config.h>
-#endif
-
-#include <stdio.h>
-#include <assert.h>
-#include <errno.h>
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-
-#include <sys/types.h>
-#include <sys/stat.h>
-
-#include "gawkapi.h"
-
-#include "gettext.h"
-#define _(msgid) gettext(msgid)
-#define N_(msgid) msgid
-
-#include "gawkfts.h"
-#include "stack.h"
-
-static const gawk_api_t *api; /* for convenience macros to work */
-static awk_ext_id_t ext_id;
-static awk_bool_t init_filefuncs(void);
-static awk_bool_t (*init_func)(void) = init_filefuncs;
-static const char *ext_version = "filefuncs extension: version 1.0";
-
-int plugin_is_GPL_compatible;
-@end example
-
-@cindex programming conventions @subentry @command{gawk} extensions
-By convention, for an @command{awk} function @code{foo()}, the C function
-that implements it is called @code{do_foo()}. The function should have
-two arguments. The first is an @code{int}, usually called @code{nargs},
-that represents the number of actual arguments for the function.
-The second is a pointer to an @code{awk_value_t} structure, usually named
-@code{result}:
-
-@example
-@group
-/* do_chdir --- provide dynamically loaded chdir() function for gawk */
-
-static awk_value_t *
-do_chdir(int nargs, awk_value_t *result, struct awk_ext_func *unused)
-@end group
-@{
- awk_value_t newdir;
- int ret = -1;
-
- assert(result != NULL);
-@end example
-
-The @code{newdir}
-variable represents the new directory to change to, which is retrieved
-with @code{get_argument()}. Note that the first argument is
-numbered zero.
-
-If the argument is retrieved successfully, the function calls the
-@code{chdir()} system call. Otherwise, if the @code{chdir()} fails,
-it updates @code{ERRNO}:
-
-@example
- if (get_argument(0, AWK_STRING, & newdir)) @{
- ret = chdir(newdir.str_value.str);
- if (ret < 0)
- update_ERRNO_int(errno);
- @}
-@end example
-
-Finally, the function returns the return value to the @command{awk} level:
-
-@example
- return make_number(ret, result);
-@}
-@end example
-
-The @code{stat()} extension is more involved. First comes a function
-that turns a numeric mode into a printable representation
-(e.g., octal @code{0644} becomes @samp{-rw-r--r--}). This is omitted here for
brevity:
-
-@example
-/* format_mode --- turn a stat mode field into something readable */
-
-static char *
-format_mode(unsigned long fmode)
-@{
- @dots{}
-@}
-@end example
-
-Next comes a function for reading symbolic links, which is also
-omitted here for brevity:
-
-@example
-/* read_symlink --- read a symbolic link into an allocated buffer.
- @dots{} */
-
-static char *
-read_symlink(const char *fname, size_t bufsize, ssize_t *linksize)
-@{
- @dots{}
-@}
-@end example
-
-Two helper functions simplify entering values in the
-array that will contain the result of the @code{stat()}:
-
-@example
-/* array_set --- set an array element */
-
-static void
-array_set(awk_array_t array, const char *sub, awk_value_t *value)
-@{
- awk_value_t index;
-
- set_array_element(array,
- make_const_string(sub, strlen(sub), & index),
- value);
-
-@}
-
-/* array_set_numeric --- set an array element with a number */
-
-static void
-array_set_numeric(awk_array_t array, const char *sub, double num)
-@{
- awk_value_t tmp;
-
- array_set(array, sub, make_number(num, & tmp));
-@}
-@end example
-
-The following function does most of the work to fill in
-the @code{awk_array_t} result array with values obtained
-from a valid @code{struct stat}. This work is done in a separate function
-to support the @code{stat()} function for @command{gawk} and also
-to support the @code{fts()} extension, which is included in
-the same file but whose code is not shown here
-(@pxref{Extension Sample File Functions}).
-
-The first part of the function is variable declarations,
-including a table to map file types to strings:
-
-@example
-/* fill_stat_array --- do the work to fill an array with stat info */
-
-static int
-fill_stat_array(const char *name, awk_array_t array, struct stat *sbuf)
-@{
- char *pmode; /* printable mode */
- const char *type = "unknown";
- awk_value_t tmp;
- static struct ftype_map @{
- unsigned int mask;
- const char *type;
- @} ftype_map[] = @{
- @{ S_IFREG, "file" @},
- @{ S_IFBLK, "blockdev" @},
- @{ S_IFCHR, "chardev" @},
- @{ S_IFDIR, "directory" @},
-#ifdef S_IFSOCK
- @{ S_IFSOCK, "socket" @},
-#endif
-#ifdef S_IFIFO
- @{ S_IFIFO, "fifo" @},
-#endif
-#ifdef S_IFLNK
- @{ S_IFLNK, "symlink" @},
-#endif
-#ifdef S_IFDOOR /* Solaris weirdness */
- @{ S_IFDOOR, "door" @},
-#endif
- @};
- int j, k;
-@end example
-
-The destination array is cleared, and then code fills in
-various elements based on values in the @code{struct stat}:
-
-@example
- /* empty out the array */
- clear_array(array);
-
- /* fill in the array */
- array_set(array, "name", make_const_string(name, strlen(name),
- & tmp));
- array_set_numeric(array, "dev", sbuf->st_dev);
- array_set_numeric(array, "ino", sbuf->st_ino);
- array_set_numeric(array, "mode", sbuf->st_mode);
- array_set_numeric(array, "nlink", sbuf->st_nlink);
- array_set_numeric(array, "uid", sbuf->st_uid);
- array_set_numeric(array, "gid", sbuf->st_gid);
- array_set_numeric(array, "size", sbuf->st_size);
- array_set_numeric(array, "blocks", sbuf->st_blocks);
- array_set_numeric(array, "atime", sbuf->st_atime);
- array_set_numeric(array, "mtime", sbuf->st_mtime);
- array_set_numeric(array, "ctime", sbuf->st_ctime);
-
- /* for block and character devices, add rdev,
- major and minor numbers */
- if (S_ISBLK(sbuf->st_mode) || S_ISCHR(sbuf->st_mode)) @{
- array_set_numeric(array, "rdev", sbuf->st_rdev);
- array_set_numeric(array, "major", major(sbuf->st_rdev));
- array_set_numeric(array, "minor", minor(sbuf->st_rdev));
- @}
-@end example
-
-@noindent
-The latter part of the function makes selective additions
-to the destination array, depending upon the availability of
-certain members and/or the type of the file. It then returns zero,
-for success:
-
-@example
-@group
-#ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
- array_set_numeric(array, "blksize", sbuf->st_blksize);
-#endif
-@end group
-
- pmode = format_mode(sbuf->st_mode);
- array_set(array, "pmode", make_const_string(pmode, strlen(pmode),
- & tmp));
-
- /* for symbolic links, add a linkval field */
- if (S_ISLNK(sbuf->st_mode)) @{
- char *buf;
- ssize_t linksize;
-
- if ((buf = read_symlink(name, sbuf->st_size,
- & linksize)) != NULL)
- array_set(array, "linkval",
- make_malloced_string(buf, linksize, & tmp));
- else
- warning(ext_id, _("stat: unable to read symbolic link `%s'"),
- name);
- @}
-
- /* add a type field */
- type = "unknown"; /* shouldn't happen */
- for (j = 0, k = sizeof(ftype_map)/sizeof(ftype_map[0]); j < k; j++) @{
- if ((sbuf->st_mode & S_IFMT) == ftype_map[j].mask) @{
- type = ftype_map[j].type;
- break;
- @}
- @}
-
- array_set(array, "type", make_const_string(type, strlen(type), & tmp));
-
- return 0;
-@}
-@end example
-
-The third argument to @code{stat()} was not discussed previously. This
-argument is optional. If present, it causes @code{do_stat()} to use
-the @code{stat()} system call instead of the @code{lstat()} system
-call. This is done by using a function pointer: @code{statfunc}.
-@code{statfunc} is initialized to point to @code{lstat()} (instead
-of @code{stat()}) to get the file information, in case the file is a
-symbolic link. However, if the third argument is included, @code{statfunc}
-is set to point to @code{stat()}, instead.
-
-Here is the @code{do_stat()} function, which starts with
-variable declarations and argument checking:
-
-@example
-/* do_stat --- provide a stat() function for gawk */
-
-static awk_value_t *
-do_stat(int nargs, awk_value_t *result, struct awk_ext_func *unused)
-@{
- awk_value_t file_param, array_param;
- char *name;
- awk_array_t array;
- int ret;
- struct stat sbuf;
- /* default is lstat() */
- int (*statfunc)(const char *path, struct stat *sbuf) = lstat;
-
- assert(result != NULL);
-@end example
-
-Then comes the actual work. First, the function gets the arguments.
-Next, it gets the information for the file. If the called function
-(@code{lstat()} or @code{stat()}) returns an error, the code sets
-@code{ERRNO} and returns:
-
-@example
- /* file is first arg, array to hold results is second */
- if ( ! get_argument(0, AWK_STRING, & file_param)
- || ! get_argument(1, AWK_ARRAY, & array_param)) @{
- warning(ext_id, _("stat: bad parameters"));
- return make_number(-1, result);
- @}
-
- if (nargs == 3) @{
- statfunc = stat;
- @}
-
- name = file_param.str_value.str;
- array = array_param.array_cookie;
-
- /* always empty out the array */
- clear_array(array);
-
- /* stat the file; if error, set ERRNO and return */
- ret = statfunc(name, & sbuf);
-@group
- if (ret < 0) @{
- update_ERRNO_int(errno);
- return make_number(ret, result);
- @}
-@end group
-@end example
-
-The tedious work is done by @code{fill_stat_array()}, shown
-earlier. When done, the function returns the result from
@code{fill_stat_array()}:
-
-@example
-@group
- ret = fill_stat_array(name, array, & sbuf);
-
- return make_number(ret, result);
-@}
-@end group
-@end example
-
-Finally, it's necessary to provide the ``glue'' that loads the
-new function(s) into @command{gawk}.
-
-The @code{filefuncs} extension also provides an @code{fts()}
-function, which we omit here
-(@pxref{Extension Sample File Functions}).
-For its sake, there is an initialization
-function:
-
-@example
-/* init_filefuncs --- initialization routine */
-
-static awk_bool_t
-init_filefuncs(void)
-@{
- @dots{}
-@}
-@end example
-
-We are almost done. We need an array of @code{awk_ext_func_t}
-structures for loading each function into @command{gawk}:
-
-@example
-static awk_ext_func_t func_table[] = @{
- @{ "chdir", do_chdir, 1, 1, awk_false, NULL @},
- @{ "stat", do_stat, 3, 2, awk_false, NULL @},
- @dots{}
-@};
-@end example
-
-Each extension must have a routine named @code{dl_load()} to load
-everything that needs to be loaded. It is simplest to use the
-@code{dl_load_func()} macro in @code{gawkapi.h}:
-
-@example
-/* define the dl_load() function using the boilerplate macro */
-
-dl_load_func(func_table, filefuncs, "")
-@end example
-
-And that's it!
-
-@node Using Internal File Ops
-@subsection Integrating the Extensions
-
-@cindex @command{gawk} @subentry interpreter, adding code to
-Now that the code is written, it must be possible to add it at
-runtime to the running @command{gawk} interpreter. First, the
-code must be compiled. Assuming that the functions are in
-a file named @file{filefuncs.c}, and @var{idir} is the location
-of the @file{gawkapi.h} header file,
-the following steps@footnote{In practice, you would probably want to
-use the GNU Autotools (Automake, Autoconf, Libtool, and @command{gettext}) to
-configure and build your libraries. Instructions for doing so are beyond
-the scope of this @value{DOCUMENT}. @xref{gawkextlib} for Internet links to
-the tools.} create a GNU/Linux shared library:
-
-@example
-$ @kbd{gcc -fPIC -shared -DHAVE_CONFIG_H -c -O -g -I@var{idir} filefuncs.c}
-$ @kbd{gcc -o filefuncs.so -shared filefuncs.o}
-@end example
-
-Once the library exists, it is loaded by using the @code{@@load} keyword:
-
-@example
-# file testff.awk
-@@load "filefuncs"
-
-BEGIN @{
- "pwd" | getline curdir # save current directory
- close("pwd")
-
- chdir("/tmp")
- system("pwd") # test it
- chdir(curdir) # go back
-
- print "Info for testff.awk"
- ret = stat("testff.awk", data)
- print "ret =", ret
- for (i in data)
- printf "data[\"%s\"] = %s\n", i, data[i]
- print "testff.awk modified:",
- strftime("%m %d %Y %H:%M:%S", data["mtime"])
-
- print "\nInfo for JUNK"
- ret = stat("JUNK", data)
- print "ret =", ret
- for (i in data)
- printf "data[\"%s\"] = %s\n", i, data[i]
- print "JUNK modified:", strftime("%m %d %Y %H:%M:%S", data["mtime"])
-@}
-@end example
-
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-The @env{AWKLIBPATH} environment variable tells
-@command{gawk} where to find extensions (@pxref{Finding Extensions}).
-We set it to the current directory and run the program:
-
-@example
-$ @kbd{AWKLIBPATH=$PWD gawk -f testff.awk}
-@print{} /tmp
-@print{} Info for testff.awk
-@print{} ret = 0
-@print{} data["blksize"] = 4096
-@print{} data["devbsize"] = 512
-@print{} data["mtime"] = 1412004710
-@print{} data["mode"] = 33204
-@print{} data["type"] = file
-@print{} data["dev"] = 2053
-@print{} data["gid"] = 1000
-@print{} data["ino"] = 10358899
-@print{} data["ctime"] = 1412004710
-@print{} data["blocks"] = 8
-@print{} data["nlink"] = 1
-@print{} data["name"] = testff.awk
-@print{} data["atime"] = 1412004716
-@print{} data["pmode"] = -rw-rw-r--
-@print{} data["size"] = 666
-@print{} data["uid"] = 1000
-@print{} testff.awk modified: 09 29 2014 18:31:50
-@print{}
-@print{} Info for JUNK
-@print{} ret = -1
-@print{} JUNK modified: 01 01 1970 02:00:00
-@end example
-
-@node Extension Samples
-@section The Sample Extensions in the @command{gawk} Distribution
-@cindex extensions @subentry loadable @subentry distributed with @command{gawk}
-
-This @value{SECTION} provides a brief overview of the sample extensions
-that come in the @command{gawk} distribution. Some of them are intended
-for production use (e.g., the @code{filefuncs}, @code{readdir}, and
-@code{inplace} extensions). Others mainly provide example code that
-shows how to use the extension API.
-
-@menu
-* Extension Sample File Functions:: The file functions sample.
-* Extension Sample Fnmatch:: An interface to @code{fnmatch()}.
-* Extension Sample Fork:: An interface to @code{fork()} and other
- process functions.
-* Extension Sample Inplace:: Enabling in-place file editing.
-* Extension Sample Ord:: Character to value to character
- conversions.
-* Extension Sample Readdir:: An interface to @code{readdir()}.
-* Extension Sample Revout:: Reversing output sample output wrapper.
-* Extension Sample Rev2way:: Reversing data sample two-way processor.
-* Extension Sample Read write array:: Serializing an array to a file.
-* Extension Sample Readfile:: Reading an entire file into a string.
-* Extension Sample Time:: An interface to @code{gettimeofday()}
- and @code{sleep()}.
-* Extension Sample API Tests:: Tests for the API.
-@end menu
-
-@node Extension Sample File Functions
-@subsection File-Related Functions
-
-The @code{filefuncs} extension provides three different functions, as follows.
-The usage is:
-
-@table @asis
-@item @code{@@load "filefuncs"}
-This is how you load the extension.
-
-@cindex @code{chdir()} extension function
-@item @code{result = chdir("/some/directory")}
-The @code{chdir()} function is a direct hook to the @code{chdir()}
-system call to change the current directory. It returns zero
-upon success or a value less than zero upon error.
-In the latter case, it updates @code{ERRNO}.
-
-@cindex @code{stat()} extension function
-@item @code{result = stat("/some/path", statdata} [@code{, follow}]@code{)}
-The @code{stat()} function provides a hook into the
-@code{stat()} system call.
-It returns zero upon success or a value less than zero upon error.
-In the latter case, it updates @code{ERRNO}.
-
-By default, it uses the @code{lstat()} system call. However, if passed
-a third argument, it uses @code{stat()} instead.
-
-In all cases, it clears the @code{statdata} array.
-When the call is successful, @code{stat()} fills the @code{statdata}
-array with information retrieved from the filesystem, as follows:
-
-@multitable @columnfractions .15 .50 .20
-@headitem Subscript @tab Field in @code{struct stat} @tab File type
-@item @code{"name"} @tab The @value{FN} @tab All
-@item @code{"dev"} @tab @code{st_dev} @tab All
-@item @code{"ino"} @tab @code{st_ino} @tab All
-@item @code{"mode"} @tab @code{st_mode} @tab All
-@item @code{"nlink"} @tab @code{st_nlink} @tab All
-@item @code{"uid"} @tab @code{st_uid} @tab All
-@item @code{"gid"} @tab @code{st_gid} @tab All
-@item @code{"size"} @tab @code{st_size} @tab All
-@item @code{"atime"} @tab @code{st_atime} @tab All
-@item @code{"mtime"} @tab @code{st_mtime} @tab All
-@item @code{"ctime"} @tab @code{st_ctime} @tab All
-@item @code{"rdev"} @tab @code{st_rdev} @tab Device files
-@item @code{"major"} @tab @code{st_major} @tab Device files
-@item @code{"minor"} @tab @code{st_minor} @tab Device files
-@item @code{"blksize"} @tab @code{st_blksize} @tab All
-@item @code{"pmode"} @tab A human-readable version of the mode value, like
that printed by
-@command{ls} (for example, @code{"-rwxr-xr-x"}) @tab All
-@item @code{"linkval"} @tab The value of the symbolic link @tab Symbolic links
-@item @code{"type"} @tab The type of the file as a string---one of
-@code{"file"},
-@code{"blockdev"},
-@code{"chardev"},
-@code{"directory"},
-@code{"socket"},
-@code{"fifo"},
-@code{"symlink"},
-@code{"door"},
-or
-@code{"unknown"}
-(not all systems support all file types) @tab All
-@end multitable
-
-@cindex @code{fts()} extension function
-@item @code{flags = or(FTS_PHYSICAL, ...)}
-@itemx @code{result = fts(pathlist, flags, filedata)}
-Walk the file trees provided in @code{pathlist} and fill in the
-@code{filedata} array, as described next. @code{flags} is the bitwise
-OR of several predefined values, also described in a moment.
-Return zero if there were no errors, otherwise return @minus{}1.
-@end table
-
-The @code{fts()} function provides a hook to the C library @code{fts()}
-routines for traversing file hierarchies. Instead of returning data
-about one file at a time in a stream, it fills in a multidimensional
-array with data about each file and directory encountered in the requested
-hierarchies.
-
-The arguments are as follows:
-
-@table @code
-@item pathlist
-An array of @value{FN}s. The element values are used; the index values are
ignored.
-
-@item flags
-This should be the bitwise OR of one or more of the following
-predefined constant flag values. At least one of
-@code{FTS_LOGICAL} or @code{FTS_PHYSICAL} must be provided; otherwise
-@code{fts()} returns an error value and sets @code{ERRNO}.
-The flags are:
-
-@c nested table
-@table @code
-@item FTS_LOGICAL
-Do a ``logical'' file traversal, where the information returned for
-a symbolic link refers to the linked-to file, and not to the symbolic
-link itself. This flag is mutually exclusive with @code{FTS_PHYSICAL}.
-
-@item FTS_PHYSICAL
-Do a ``physical'' file traversal, where the information returned for a
-symbolic link refers to the symbolic link itself. This flag is mutually
-exclusive with @code{FTS_LOGICAL}.
-
-@item FTS_NOCHDIR
-As a performance optimization, the C library @code{fts()} routines
-change directory as they traverse a file hierarchy. This flag disables
-that optimization.
-
-@item FTS_COMFOLLOW
-Immediately follow a symbolic link named in @code{pathlist},
-whether or not @code{FTS_LOGICAL} is set.
-
-@item FTS_SEEDOT
-By default, the C library @code{fts()} routines do not return entries for
-@file{.} (dot) and @file{..} (dot-dot). This option causes entries for
-dot-dot to also be included. (The extension always includes an entry
-for dot; more on this in a moment.)
-
-@item FTS_XDEV
-During a traversal, do not cross onto a different mounted filesystem.
-@end table
-
-@item filedata
-The @code{filedata} array holds the results.
-@code{fts()} first clears it. Then it creates
-an element in @code{filedata} for every element in @code{pathlist}.
-The index is the name of the directory or file given in @code{pathlist}.
-The element for this index is itself an array. There are two cases:
-
-@c nested table
-@table @emph
-@item The path is a file
-In this case, the array contains two or three elements:
-
-@c doubly nested table
-@table @code
-@item "path"
-The full path to this file, starting from the ``root'' that was given
-in the @code{pathlist} array.
-
-@item "stat"
-This element is itself an array, containing the same information as provided
-by the @code{stat()} function described earlier for its
-@code{statdata} argument. The element may not be present if
-the @code{stat()} system call for the file failed.
-
-@item "error"
-If some kind of error was encountered, the array will also
-contain an element named @code{"error"}, which is a string describing the
error.
-@end table
-
-@item The path is a directory
-In this case, the array contains one element for each entry in the
-directory. If an entry is a file, that element is the same as for files, just
-described. If the entry is a directory, that element is (recursively)
-an array describing the subdirectory. If @code{FTS_SEEDOT} was provided
-in the flags, then there will also be an element named @code{".."}. This
-element will be an array containing the data as provided by @code{stat()}.
-
-In addition, there will be an element whose index is @code{"."}.
-This element is an array containing the same two or three elements as
-for a file: @code{"path"}, @code{"stat"}, and @code{"error"}.
-@end table
-@end table
-
-The @code{fts()} function returns zero if there were no errors.
-Otherwise, it returns @minus{}1.
-
-@quotation NOTE
-The @code{fts()} extension does not exactly mimic the
-interface of the C library @code{fts()} routines, choosing instead to
-provide an interface that is based on associative arrays, which is
-more comfortable to use from an @command{awk} program. This includes the
-lack of a comparison function, because @command{gawk} already provides
-powerful array sorting facilities. Although an @code{fts_read()}-like
-interface could have been provided, this felt less natural than simply
-creating a multidimensional array to represent the file hierarchy and
-its information.
-@end quotation
-
-See @file{test/fts.awk} in the @command{gawk} distribution for an example
-use of the @code{fts()} extension function.
-
-@node Extension Sample Fnmatch
-@subsection Interface to @code{fnmatch()}
-
-This extension provides an interface to the C library
-@code{fnmatch()} function. The usage is:
-
-@table @code
-@item @@load "fnmatch"
-This is how you load the extension.
-
-@cindex @code{fnmatch()} extension function
-@item result = fnmatch(pattern, string, flags)
-The return value is zero on success, @code{FNM_NOMATCH}
-if the string did not match the pattern, or
-a different nonzero value if an error occurred.
-@end table
-
-In addition to the @code{fnmatch()} function, the @code{fnmatch} extension
-adds one constant (@code{FNM_NOMATCH}), and an array of flag values
-named @code{FNM}.
-
-The arguments to @code{fnmatch()} are:
-
-@table @code
-@item pattern
-The @value{FN} wildcard to match
-
-@item string
-The @value{FN} string
-
-@item flag
-Either zero, or the bitwise OR of one or more of the
-flags in the @code{FNM} array
-@end table
-
-The flags are as follows:
-
-@multitable @columnfractions .25 .75
-@headitem Array element @tab Corresponding flag defined by @code{fnmatch()}
-@item @code{FNM["CASEFOLD"]} @tab @code{FNM_CASEFOLD}
-@item @code{FNM["FILE_NAME"]} @tab @code{FNM_FILE_NAME}
-@item @code{FNM["LEADING_DIR"]} @tab @code{FNM_LEADING_DIR}
-@item @code{FNM["NOESCAPE"]} @tab @code{FNM_NOESCAPE}
-@item @code{FNM["PATHNAME"]} @tab @code{FNM_PATHNAME}
-@item @code{FNM["PERIOD"]} @tab @code{FNM_PERIOD}
-@end multitable
-
-Here is an example:
-
-@example
-@@load "fnmatch"
-@dots{}
-flags = or(FNM["PERIOD"], FNM["NOESCAPE"])
-if (fnmatch("*.a", "foo.c", flags) == FNM_NOMATCH)
- print "no match"
-@end example
-
-@node Extension Sample Fork
-@subsection Interface to @code{fork()}, @code{wait()}, and @code{waitpid()}
-
-The @code{fork} extension adds three functions, as follows:
-
-@table @code
-@item @@load "fork"
-This is how you load the extension.
-
-@cindex @code{fork()} extension function
-@item pid = fork()
-This function creates a new process. The return value is zero in the
-child and the process ID number of the child in the parent, or @minus{}1
-upon error. In the latter case, @code{ERRNO} indicates the problem.
-In the child, @code{PROCINFO["pid"]} and @code{PROCINFO["ppid"]} are
-updated to reflect the correct values.
-
-@cindex @code{waitpid()} extension function
-@item ret = waitpid(pid)
-This function takes a numeric argument, which is the process ID to
-wait for. The return value is that of the
-@code{waitpid()} system call.
-
-@cindex @code{wait()} extension function
-@item ret = wait()
-This function waits for the first child to die.
-The return value is that of the
-@code{wait()} system call.
-@end table
-
-There is no corresponding @code{exec()} function.
-
-Here is an example:
-
-@example
-@@load "fork"
-@dots{}
-if ((pid = fork()) == 0)
- print "hello from the child"
-else
- print "hello from the parent"
-@end example
-
-@node Extension Sample Inplace
-@subsection Enabling In-Place File Editing
-
-@cindex @code{inplace} extension
-The @code{inplace} extension emulates GNU @command{sed}'s @option{-i} option,
-which performs ``in-place'' editing of each input file.
-It uses the bundled @file{inplace.awk} include file to invoke the extension
-properly. This extension makes use of the namespace facility to place
-all the variables and functions in the @code{inplace} namespace
-(@pxref{Namespaces}):
-
-@example
-@c file eg/lib/inplace.awk
-@group
-# inplace --- load and invoke the inplace extension.
-@c endfile
-@ignore
-@c file eg/lib/inplace.awk
-#
-# Copyright (C) 2013, 2017, 2019 the Free Software Foundation, Inc.
-#
-# This file is part of GAWK, the GNU implementation of the
-# AWK Programming Language.
-#
-# GAWK is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 3 of the License, or
-# (at your option) any later version.
-#
-# GAWK is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, write to the Free Software
-# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
USA
-#
-# Andrew J. Schorr, aschorr@@telemetry-investments.com
-# January 2013
-#
-# Revised for namespaces
-# Arnold Robbins, arnold@@skeeve.com
-# July 2017
-# June 2019, add backwards compatibility
-@c endfile
-@end ignore
-@c file eg/lib/inplace.awk
-
-@@load "inplace"
-
-# Please set inplace::suffix to make a backup copy. For example, you may
-# want to set inplace::suffix to .bak on the command line or in a BEGIN rule.
-
-# Before there were namespaces in gawk, this extension used
-# INPLACE_SUFFIX as the variable for making backup copies. We allow this
-# too, so that any code that used the previous version continues to work.
-
-# By default, each filename on the command line will be edited inplace.
-# But you can selectively disable this by adding an inplace::enable=0 argument
-# prior to files that you do not want to process this way. You can then
-# reenable it later on the commandline by putting inplace::enable=1 before
files
-# that you wish to be subject to inplace editing.
-
-# N.B. We call inplace::end() in the BEGINFILE and END rules so that any
-# actions in an ENDFILE rule will be redirected as expected.
-
-@@namespace "inplace"
-@end group
-
-@group
-BEGIN @{
- enable = 1 # enabled by default
-@}
-@end group
-
-@group
-BEGINFILE @{
- sfx = (suffix ? suffix : awk::INPLACE_SUFFIX)
- if (filename != "")
- end(filename, sfx)
- if (enable)
- begin(filename = FILENAME, sfx)
- else
- filename = ""
-@}
-@end group
-
-@group
-END @{
- if (filename != "")
- end(filename, (suffix ? suffix : awk::INPLACE_SUFFIX))
-@}
-@end group
-@c endfile
-@end example
-
-For each regular file that is processed, the extension redirects
-standard output to a temporary file configured to have the same owner
-and permissions as the original. After the file has been processed,
-the extension restores standard output to its original destination.
-If @code{inplace::suffix} is not an empty string, the original file is
-linked to a backup @value{FN} created by appending that suffix. Finally,
-the temporary file is renamed to the original @value{FN}.
-
-Note that the use of this feature can be controlled by placing
-@samp{inplace::enable=0} on the command-line prior to listing files that
-should not be processed this way. You can reenable inplace editing by adding
-an @samp{inplace::enable=1} argument prior to files that should be subject
-to inplace editing.
-
-The @code{inplace::filename} variable serves to keep track of the
-current @value{FN} so as to not invoke @code{inplace::end()} before
-processing the first file.
-
-If any error occurs, the extension issues a fatal error to terminate
-processing immediately without damaging the original file.
-
-Here are some simple examples:
-
-@example
-$ @kbd{gawk -i inplace '@{ gsub(/foo/, "bar") @}; @{ print @}' file1 file2
file3}
-@end example
-
-To keep a backup copy of the original files, try this:
-
-@example
-$ @kbd{gawk -i inplace -v inplace::suffix=.bak '@{ gsub(/foo/, "bar") @}}
-> @kbd{@{ print @}' file1 file2 file3}
-@end example
-
-Please note that, while the extension does attempt to preserve ownership and
permissions, it makes no attempt to copy the ACLs from the original file.
-
-If the program dies prematurely, as might happen if an unhandled signal is
received, a temporary file may be left behind.
-
-@node Extension Sample Ord
-@subsection Character and Numeric values: @code{ord()} and @code{chr()}
-
-The @code{ordchr} extension adds two functions, named
-@code{ord()} and @code{chr()}, as follows:
-
-@table @code
-@item @@load "ordchr"
-This is how you load the extension.
-
-@cindex @code{ord()} extension function
-@item number = ord(string)
-Return the numeric value of the first character in @code{string}.
-
-@cindex @code{chr()} extension function
-@item char = chr(number)
-Return a string whose first character is that represented by @code{number}.
-@end table
-
-These functions are inspired by the Pascal language functions
-of the same name. Here is an example:
-
-@example
-@@load "ordchr"
-@dots{}
-printf("The numeric value of 'A' is %d\n", ord("A"))
-printf("The string value of 65 is %s\n", chr(65))
-@end example
-
-@node Extension Sample Readdir
-@subsection Reading Directories
-
-The @code{readdir} extension adds an input parser for directories.
-The usage is as follows:
-
-@cindex @code{readdir} extension
-@example
-@@load "readdir"
-@end example
-
-When this extension is in use, instead of skipping directories named
-on the command line (or with @code{getline}),
-they are read, with each entry returned as a record.
-
-The record consists of three fields separated by forward slash characters.
-The first two are the inode number and the @value{FN}, and the third field
-is a single letter indicating the type of the file. The letters and their
-corresponding file types are shown in @ref{table-readdir-file-types}.
-
-@float Table,table-readdir-file-types
-@caption{File types returned by the @code{readdir} extension}
-@multitable @columnfractions .1 .9
-@headitem Letter @tab File type
-@item @code{b} @tab Block device
-@item @code{c} @tab Character device
-@item @code{d} @tab Directory
-@item @code{f} @tab Regular file
-@item @code{l} @tab Symbolic link
-@item @code{p} @tab Named pipe (FIFO)
-@item @code{s} @tab Socket
-@end multitable
-@end float
-
-On systems where the directory entry contains the file type, the third
-field is filled in from that information.
-On systems without the file type information, the extension falls back
-to calling the @code{stat()} system call
-in order to provide the information.
-Thus the third field should never be @samp{u} (for ``unknown'').
-
-Normally, when reading directories, you should set @code{FS}
-equal to @code{"/"}. However, you may instead chose to create
-@code{PROCINFO["readdir_override"]} (with any value). If this element
-exists when the directory is opened, then the extension automatically
-sets the fields in each record for you.
-
-By default, if a directory cannot be opened (due to permission problems,
-for example), @command{gawk} will exit. As with regular files, this
-situation can be handled using a @code{BEGINFILE} rule that checks
-@code{ERRNO} and prints an error or otherwise handles the problem.
-
-Here is an example:
-
-@example
-@@load "readdir"
-@dots{}
-BEGIN @{ FS = "/" @}
-@{ print "@value{FN} is", $2 @}
-@end example
-
-@node Extension Sample Revout
-@subsection Reversing Output
-
-The @code{revoutput} extension adds a simple output wrapper that reverses
-the characters in each output line. Its main purpose is to show how to
-write an output wrapper, although it may be mildly amusing for the unwary.
-Here is an example:
-
-@cindex @code{revoutput} extension
-@example
-@@load "revoutput"
-
-BEGIN @{
- REVOUT = 1
- print "don't panic" > "/dev/stdout"
-@}
-@end example
-
-The output from this program is @samp{cinap t'nod}.
-
-@node Extension Sample Rev2way
-@subsection Two-Way I/O Example
-
-The @code{revtwoway} extension adds a simple two-way processor that
-reverses the characters in each line sent to it for reading back by
-the @command{awk} program. Its main purpose is to show how to write
-a two-way processor, although it may also be mildly amusing.
-The following example shows how to use it:
-
-@cindex @code{revtwoway} extension
-@example
-@@load "revtwoway"
-
-BEGIN @{
- cmd = "/magic/mirror"
- print "don't panic" |& cmd
- cmd |& getline result
- print result
- close(cmd)
-@}
-@end example
-
-The output from this program
-@ifnotinfo
-also is:
-@end ifnotinfo
-@ifinfo
-is:
-@end ifinfo
-@samp{cinap t'nod}.
-
-@node Extension Sample Read write array
-@subsection Dumping and Restoring an Array
-
-The @code{rwarray} extension adds four functions,
-named @code{writea()}, @code{reada()},
-@code{writeall()} and @code{readall()}, as follows:
-
-@table @code
-@item @@load "rwarray"
-This is how you load the extension.
-
-@cindex @code{writea()} extension function
-@item ret = writea(file, array)
-This function takes a string argument, which is the name of the file
-to which to dump the array, and the array itself as the second argument.
-@code{writea()} understands arrays of arrays. It returns one on
-success, or zero upon failure.
-
-@cindex @code{reada()} extension function
-@item ret = reada(file, array)
-@code{reada()} is the inverse of @code{writea()};
-it reads the file named as its first argument, filling in
-the array named as the second argument. It clears the array first.
-Here too, the return value is one on success, or zero upon failure.
-
-@cindex @code{writeall()} extension function
-@item ret = writeall(file)
-This function takes a string argument, which is the name of the file
-to which to dump the state of all variables.
-Calling this function
-is completely equivalent to calling
-@code{writea(file, SYMTAB)}.
-It returns one on success, or zero upon failure
-
-@cindex @code{readall()} extension function
-@item ret = readall(file)
-This function takes a string argument, which is the name of the
-file from which to read the contents of various global variables.
-For each variable in the file, the data is loaded unless the variable
-has already been assigned a value or used as an array.
-In that case, the data for that variable
-in the file is ignored.
-It returns one on success, or zero upon failure.
-@end table
-
-The array created by @code{reada()} is identical to that written by
-@code{writea()} in the sense that the contents are the same. However,
-due to implementation issues, the array traversal order of the re-created
-array is likely to be different from that of the original array. As array
-traversal order in @command{awk} is by default undefined, this is (technically)
-not a problem. If you need to guarantee a particular traversal
-order, use the array sorting features in @command{gawk} to do so
-(@pxref{Array Sorting}).
-
-The file contains binary data. All integral values are written in network
-byte order. However, double-precision floating-point values are written
-as native binary data. Thus, arrays containing only string data can
-theoretically be dumped on systems with one byte order and restored on
-systems with a different one, but this has not been tried.
-
-Note that the @code{writeall()} and @code{readall()} functions provide
-a mechanism for maintaining persistent state across repeated invocations of a
-program. If, for example, a program calculates some statistics based on the
-data in a series of files, it could save state using @code{writeall()} after
-processing N files, and then reload the state using @code{readall()} when
-the N+1st file arrives to update the results.
-
-Here is an example:
-
-@example
-@@load "rwarray"
-@dots{}
-ret = writea("arraydump.bin", array)
-@dots{}
-ret = reada("arraydump.bin", array)
-@dots{}
-ret = writeall("globalstate.bin")
-@dots{}
-ret = readall("globalstate.bin")
-@end example
-
-@node Extension Sample Readfile
-@subsection Reading an Entire File
-
-The @code{readfile} extension adds a single function
-named @code{readfile()}, and an input parser:
-
-@table @code
-@item @@load "readfile"
-This is how you load the extension.
-
-@cindex @code{readfile()} extension function
-@item result = readfile("/some/path")
-The argument is the name of the file to read. The return value is a
-string containing the entire contents of the requested file. Upon error,
-the function returns the empty string and sets @code{ERRNO}.
-
-@item BEGIN @{ PROCINFO["readfile"] = 1 @}
-In addition, the extension adds an input parser that is activated if
-@code{PROCINFO["readfile"]} exists.
-When activated, each input file is returned in its entirety as @code{$0}.
-@code{RT} is set to the null string.
-@end table
-
-Here is an example:
-
-@example
-@@load "readfile"
-@dots{}
-contents = readfile("/path/to/file");
-if (contents == "" && ERRNO != "") @{
- print("problem reading file", ERRNO) > "/dev/stderr"
- ...
-@}
-@end example
-
-@node Extension Sample Time
-@subsection Extension Time Functions
-
-The @code{time} extension adds three functions, named @code{gettimeofday()}
-@code{sleep()}, and @code{strptime()}, as follows:
-
-@table @code
-@item @@load "time"
-This is how you load the extension.
-
-@cindex @code{gettimeofday()} extension function
-@item the_time = gettimeofday()
-Return the time in seconds that has elapsed since 1970-01-01 UTC as a
-floating-point value. If the time is unavailable on this platform, return
-@minus{}1 and set @code{ERRNO}. The returned time should have sub-second
-precision, but the actual precision may vary based on the platform.
-If the standard C @code{gettimeofday()} system call is available on this
-platform, then it simply returns the value. Otherwise, if on MS-Windows,
-it tries to use @code{GetSystemTimeAsFileTime()}.
-
-@cindex @code{sleep()} extension function
-@item result = sleep(@var{seconds})
-Attempt to sleep for @var{seconds} seconds. If @var{seconds} is negative,
-or the attempt to sleep fails, return @minus{}1 and set @code{ERRNO}.
-Otherwise, return zero after sleeping for the indicated amount of time.
-Note that @var{seconds} may be a floating-point (nonintegral) value.
-Implementation details: depending on platform availability, this function
-tries to use @code{nanosleep()} or @code{select()} to implement the delay.
-
-@cindex @code{strptime()} extension function
-@item timeval = strptime(@var{string}, @var{format})
-This function takes two arguments, a string representing a date and
-time, and a format string describing the data in the string. It
-calls the C library @code{strptime()} function with the given values.
-If the parsing succeeds, the results are passed to the C library
-@code{mktime()} function, and its result is returned, expressing
-the time in seconds since the epoch in the current local timezone,
-regardless of any timezone specified in the string arguments. (This
-is the same as @command{gawk}'s built-in @code{systime()} function.)
-Otherwise it returns @minus{}1 upon error. In the latter case,
-
-Note that the underlying @code{strptime()} C library routine apparently
-ignores any time zone indication in the date string, producing values
-relative to the current time zone.
-@ignore
-It might be better to have this
-routine return a string similar to what @command{gawk}'s @code{mktime()}
-function expects, but we ran out of energy.
-@end ignore
-@end table
-
-@node Extension Sample API Tests
-@subsection API Tests
-@cindex @code{testext} extension
-
-The @code{testext} extension exercises parts of the extension API that
-are not tested by the other samples. The @file{extension/testext.c}
-file contains both the C code for the extension and @command{awk}
-test code inside C comments that run the tests. The testing framework
-extracts the @command{awk} code and runs the tests. See the source file
-for more information.
-
-@node gawkextlib
-@section The @code{gawkextlib} Project
-@cindex extensions @subentry loadable @subentry @code{gawkextlib} project
-
-@cindex @code{gawkextlib} project
-The @uref{https://sourceforge.net/projects/gawkextlib/, @code{gawkextlib}}
-project provides a number of @command{gawk} extensions, including one for
-processing XML files. This is the evolution of the original @command{xgawk}
-(XML @command{gawk}) project.
-
-There are a number of extensions. Some of the more interesting ones are:
-
-@itemize @value{BULLET}
-@item
-@code{abort} extension. It allows you to exit immediately from your
-@command{awk} program without running the @code{END} rules.
-
-@item
-@code{json} extension.
-This serializes a multidimensional array into a JSON string, and
-can deserialize a JSON string into a @command{gawk} array.
-This extension is interesting since it is written in C++ instead of C.
-
-@item
-MPFR library extension.
-This provides access to a number of MPFR functions that @command{gawk}'s
-native MPFR support does not.
-
-@item
-Select extension. It provides functionality based on the
-@code{select()} system call.
-
-@item
-XML parser extension, using the @uref{https://expat.sourceforge.net, Expat}
-XML parsing library
-@end itemize
-
-@cindex @command{git} utility
-You can check out the code for the @code{gawkextlib} project
-using the @uref{https://git-scm.com, Git} distributed source
-code control system. The command is as follows:
-
-@example
-git clone git://git.code.sf.net/p/gawkextlib/code gawkextlib-code
-@end example
-
-@cindex RapidJson JSON parser library
-You will need to have the @uref{http://www.rapidjson.org, RapidJson}
-JSON parser library installed in order to build and use the @code{json}
extension.
-
-@cindex Expat XML parser library
-You will need to have the @uref{https://expat.sourceforge.net, Expat}
-XML parser library installed in order to build and use the XML extension.
-
-In addition, you must have the GNU Autotools installed
-(@uref{https://www.gnu.org/software/autoconf, Autoconf},
-@uref{https://www.gnu.org/software/automake, Automake},
-@uref{https://www.gnu.org/software/libtool, Libtool},
-and
-@uref{https://www.gnu.org/software/gettext, GNU @command{gettext}}).
-
-The simple recipe for building and testing @code{gawkextlib} is as follows.
-First, build and install @command{gawk}:
-
-@example
-cd .../path/to/gawk/code
-./configure --prefix=/tmp/newgawk @ii{Install in /tmp/newgawk for now}
-make && make check @ii{Build and check that all is OK}
-make install @ii{Install gawk}
-@end example
-
-Next, go to @url{https://sourceforge.net/projects/gawkextlib/files} to
-download @code{gawkextlib} and any extensions that you would like to build.
-The @file{README} file at that site explains how to build the code. If you
-installed @command{gawk} in a non-standard location, you will need to
-specify @samp{./configure --with-gawk=@var{/path/to/gawk}} to find it.
-You may need to use the @command{sudo} utility
-to install both @command{gawk} and @code{gawkextlib}, depending upon
-how your system works.
-
-If you write an extension that you wish to share with other
-@command{gawk} users, consider doing so through the
-@code{gawkextlib} project.
-See the project's website for more information.
-
-@node Extension summary
-@section Summary
-
-@itemize @value{BULLET}
-@item
-You can write extensions (sometimes called plug-ins) for @command{gawk}
-in C or C++ using the application programming interface (API) defined
-by the @command{gawk} developers.
-
-@item
-Extensions must have a license compatible with the GNU General Public
-License (GPL), and they must assert that fact by declaring a variable
-named @code{plugin_is_GPL_compatible}.
-
-@item
-Communication between @command{gawk} and an extension is two-way.
-@command{gawk} passes a @code{struct} to the extension that contains
-various data fields and function pointers. The extension can then call
-into @command{gawk} via the supplied function pointers to accomplish
-certain tasks.
-
-@item
-One of these tasks is to ``register'' the name and implementation of
-new @command{awk}-level functions with @command{gawk}. The implementation
-takes the form of a C function pointer with a defined signature.
-By convention, implementation functions are named @code{do_@var{XXXX}()}
-for some @command{awk}-level function @code{@var{XXXX}()}.
-
-@item
-The API is defined in a header file named @file{gawkapi.h}. You must include
-a number of standard header files @emph{before} including it in your source
file.
-
-@item
-API function pointers are provided for the following kinds of operations:
-
-@itemize @value{BULLET}
-@item
-Allocating, reallocating, and releasing memory
-
-@item
-Registration functions (you may register
-extension functions,
-exit callbacks,
-a version string,
-input parsers,
-output wrappers,
-and two-way processors)
-
-@item
-Printing fatal, nonfatal, warning, and ``lint'' warning messages
-
-@item
-Updating @code{ERRNO}, or unsetting it
-
-@item
-Accessing parameters, including converting an undefined parameter into
-an array
-
-@item
-Symbol table access (retrieving a global variable, creating one,
-or changing one)
-
-@item
-Creating and releasing cached values; this provides an
-efficient way to use values for multiple variables and
-can be a big performance win
-
-@item
-Manipulating arrays
-(retrieving, adding, deleting, and modifying elements;
-getting the count of elements in an array;
-creating a new array;
-clearing an array;
-and
-flattening an array for easy C-style looping over all its indices and elements)
-@end itemize
-
-@item
-The API defines a number of standard data types for representing
-@command{awk} values, array elements, and arrays.
-
-@item
-The API provides convenience functions for constructing values.
-It also provides memory management functions to ensure compatibility
-between memory allocated by @command{gawk} and memory allocated by an
-extension.
-
-@item
-@emph{All} memory passed from @command{gawk} to an extension must be
-treated as read-only by the extension.
-
-@item
-@emph{All} memory passed from an extension to @command{gawk} must come from
-the API's memory allocation functions. @command{gawk} takes responsibility for
-the memory and releases it when appropriate.
-
-@item
-The API provides information about the running version of @command{gawk} so
-that an extension can make sure it is compatible with the @command{gawk}
-that loaded it.
-
-@item
-It is easiest to start a new extension by copying the boilerplate code
-described in this @value{CHAPTER}. Macros in the @file{gawkapi.h} header
-file make this easier to do.
-
-@item
-The @command{gawk} distribution includes a number of small but useful
-sample extensions. The @code{gawkextlib} project includes several more
-(larger) extensions. If you wish to write an extension and contribute it
-to the community of @command{gawk} users, the @code{gawkextlib} project
-is the place to do so.
-
-@end itemize
-
-@c EXCLUDE START
-@node Extension Exercises
-@section Exercises
-
-@enumerate
-@item
-Add functions to implement system calls such as @code{chown()},
-@code{chmod()}, and @code{umask()} to the file operations extension
-presented in @ref{Internal File Ops}.
-
-@c Idea from comp.lang.awk, February 2015
-@item
-Write an input parser that prints a prompt if the input is
-a from a ``terminal'' device. You can use the @code{isatty()}
-function to tell if the input file is a terminal. (Hint: this function
-is usually expensive to call; try to call it just once.)
-The content of the prompt should come from a variable settable
-by @command{awk}-level code.
-You can write the prompt to standard error. However,
-for best results, open a new file descriptor (or file pointer)
-on @file{/dev/tty} and print the prompt there, in case standard
-error has been redirected.
-
-Why is standard error a better
-choice than standard output for writing the prompt?
-Which reading mechanism should you replace, the one to get
-a record, or the one to read raw bytes?
-
-@item
-Write a wrapper script that provides an interface similar to
-@samp{sed -i} for the ``inplace'' extension presented in
-@ref{Extension Sample Inplace}.
-
-@end enumerate
-@c EXCLUDE END
-
-@ifnotinfo
-@part @value{PART4}Appendices
-@end ifnotinfo
-
-@ifdocbook
-
-@ifclear FOR_PRINT
-Part IV contains the appendices (including the two licenses that cover
-the @command{gawk} source code and this @value{DOCUMENT}, respectively)
-and the Glossary:
-@end ifclear
-
-@ifset FOR_PRINT
-Part IV contains three appendices, the last of which is the license that
-covers the @command{gawk} source code:
-@end ifset
-
-@itemize @value{BULLET}
-@item
-@ref{Language History}
-
-@item
-@ref{Installation}
-
-@ifclear FOR_PRINT
-@item
-@ref{Notes}
-
-@item
-@ref{Basic Concepts}
-
-@item
-@ref{Glossary}
-@end ifclear
-
-@item
-@ref{Copying}
-
-@ifclear FOR_PRINT
-@item
-@ref{GNU Free Documentation License}
-@end ifclear
-@end itemize
-@end ifdocbook
-
-@node Language History
-@appendix The Evolution of the @command{awk} Language
-
-This @value{DOCUMENT} describes the GNU implementation of @command{awk},
-which follows the POSIX specification. Many longtime @command{awk}
-users learned @command{awk} programming with the original @command{awk}
-implementation in Version 7 Unix. (This implementation was the basis for
-@command{awk} in Berkeley Unix, through 4.3-Reno. Subsequent versions
-of Berkeley Unix, and, for a while, some systems derived from 4.4BSD-Lite,
used various
-versions of @command{gawk} for their @command{awk}.) This @value{CHAPTER}
-briefly describes the evolution of the @command{awk} language, with
-cross-references to other parts of the @value{DOCUMENT} where you can
-find more information.
-
-@ifset FOR_PRINT
-To save space, we have omitted
-information on the history of features in @command{gawk} from this
-edition. You can find it in the
-@uref{https://www.gnu.org/software/gawk/manual/html_node/Feature-History.html,
-online documentation}.
-@end ifset
-
-@menu
-* V7/SVR3.1:: The major changes between V7 and System V
- Release 3.1.
-* SVR4:: Minor changes between System V Releases 3.1
- and 4.
-* POSIX:: New features from the POSIX standard.
-* BTL:: New features from Brian Kernighan's version of
- @command{awk}.
-* POSIX/GNU:: The extensions in @command{gawk} not in POSIX
- @command{awk}.
-* Feature History:: The history of the features in @command{gawk}.
-* Common Extensions:: Common Extensions Summary.
-* Ranges and Locales:: How locales used to affect regexp ranges.
-* Contributors:: The major contributors to @command{gawk}.
-* History summary:: History summary.
-@end menu
-
-@node V7/SVR3.1
-@appendixsec Major Changes Between V7 and SVR3.1
-@cindex @command{awk} @subentry versions of
-@cindex @command{awk} @subentry versions of @subentry changes between V7 and
SVR3.1
-
-The @command{awk} language evolved considerably between the release of
-Version 7 Unix (1978) and the new version that was first made generally
available in
-System V Release 3.1 (1987). This @value{SECTION} summarizes the changes, with
-cross-references to further details:
-
-@itemize @value{BULLET}
-@item
-The requirement for @samp{;} to separate rules on a line
-(@pxref{Statements/Lines})
-
-@item
-User-defined functions and the @code{return} statement
-(@pxref{User-defined})
-
-@item
-The @code{delete} statement (@pxref{Delete})
-
-@item
-The @code{do}-@code{while} statement
-(@pxref{Do Statement})
-
-@item
-The built-in functions @code{atan2()}, @code{cos()}, @code{sin()},
@code{rand()}, and
-@code{srand()} (@pxref{Numeric Functions})
-
-@item
-The built-in functions @code{gsub()}, @code{sub()}, and @code{match()}
-(@pxref{String Functions})
-
-@item
-The built-in functions @code{close()} and @code{system()}
-(@pxref{I/O Functions})
-
-@item
-The @code{ARGC}, @code{ARGV}, @code{FNR}, @code{RLENGTH}, @code{RSTART},
-and @code{SUBSEP} predefined variables (@pxref{Built-in Variables})
-
-@item
-Assignable @code{$0} (@pxref{Changing Fields})
-
-@item
-The conditional expression using the ternary operator @samp{?:}
-(@pxref{Conditional Exp})
-
-@item
-The expression @samp{@var{indx} in @var{array}} outside of @code{for}
-statements (@pxref{Reference to Elements})
-
-@item
-The exponentiation operator @samp{^}
-(@pxref{Arithmetic Ops}) and its assignment operator
-form @samp{^=} (@pxref{Assignment Ops})
-
-@item
-C-compatible operator precedence, which breaks some old @command{awk}
-programs (@pxref{Precedence})
-
-@item
-Regexps as the value of @code{FS}
-(@pxref{Field Separators}) and as the
-third argument to the @code{split()} function
-(@pxref{String Functions}), rather than using only the first character
-of @code{FS}
-
-@item
-Dynamic regexps as operands of the @samp{~} and @samp{!~} operators
-(@pxref{Computed Regexps})
-
-@item
-The escape sequences @samp{\b}, @samp{\f}, and @samp{\r}
-(@pxref{Escape Sequences})
-
-@item
-Redirection of input for the @code{getline} function
-(@pxref{Getline})
-
-@item
-Multiple @code{BEGIN} and @code{END} rules
-(@pxref{BEGIN/END})
-
-@item
-Multidimensional arrays
-(@pxref{Multidimensional})
-@end itemize
-
-@node SVR4
-@appendixsec Changes Between SVR3.1 and SVR4
-
-@cindex @command{awk} @subentry versions of @subentry changes between SVR3.1
and SVR4
-The System V Release 4 (1989) version of Unix @command{awk} added these
features
-(some of which originated in @command{gawk}):
-
-@itemize @value{BULLET}
-@item
-The @code{ENVIRON} array (@pxref{Built-in Variables})
-@c gawk and MKS awk
-
-@item
-Multiple @option{-f} options on the command line
-(@pxref{Options})
-@c MKS awk
-
-@item
-The @option{-v} option for assigning variables before program execution begins
-(@pxref{Options})
-@c GNU, Bell Laboratories & MKS together
-
-@item
-The @option{--} signal for terminating command-line options
-
-@item
-The @samp{\a}, @samp{\v}, and @samp{\x} escape sequences
-(@pxref{Escape Sequences})
-@c GNU, for ANSI C compat
-
-@item
-A defined return value for the @code{srand()} built-in function
-(@pxref{Numeric Functions})
-
-@item
-The @code{toupper()} and @code{tolower()} built-in string functions
-for case translation
-(@pxref{String Functions})
-
-@item
-A cleaner specification for the @samp{%c} format-control letter in the
-@code{printf} function
-(@pxref{Control Letters})
-
-@item
-The ability to dynamically pass the field width and precision (@code{"%*.*d"})
-in the argument list of @code{printf} and @code{sprintf()}
-(@pxref{Control Letters})
-
-@item
-The use of regexp constants, such as @code{/foo/}, as expressions, where
-they are equivalent to using the matching operator, as in @samp{$0 ~ /foo/}
-(@pxref{Using Constant Regexps})
-
-@item
-Processing of escape sequences inside command-line variable assignments
-(@pxref{Assignment Options})
-@end itemize
-
-@node POSIX
-@appendixsec Changes Between SVR4 and POSIX @command{awk}
-@cindex @command{awk} @subentry versions of @subentry changes between SVR4 and
POSIX @command{awk}
-@cindex POSIX @command{awk} @subentry changes in @command{awk} versions
-
-The POSIX Command Language and Utilities standard for @command{awk} (1992)
-introduced the following changes into the language:
-
-@itemize @value{BULLET}
-@item
-The use of @option{-W} for implementation-specific options
-(@pxref{Options})
-
-@item
-The use of @code{CONVFMT} for controlling the conversion of numbers
-to strings (@pxref{Conversion})
-
-@item
-The concept of a numeric string and tighter comparison rules to go
-with it (@pxref{Typing and Comparison})
-
-@item
-The use of predefined variables as function parameter names is forbidden
-(@pxref{Definition Syntax})
-
-@item
-More complete documentation of many of the previously undocumented
-features of the language
-@end itemize
-
-In 2012, a number of extensions that had been commonly available for
-many years were finally added to POSIX. They are:
-
-@itemize @value{BULLET}
-@item
-The @code{fflush()} built-in function for flushing buffered output
-(@pxref{I/O Functions})
-
-@item
-The @code{nextfile} statement
-(@pxref{Nextfile Statement})
-
-@item
-The ability to delete all of an array at once with @samp{delete @var{array}}
-(@pxref{Delete})
-
-@end itemize
-
-@xref{Common Extensions} for a list of common extensions
-not permitted by the POSIX standard.
-
-The 2018 POSIX standard can be found online at
-@url{https://pubs.opengroup.org/onlinepubs/9699919799/}.
-
-
-@node BTL
-@appendixsec Extensions in Brian Kernighan's @command{awk}
-
-@cindex @command{awk} @subentry versions of @seealso{Brian Kernighan's
@command{awk}}
-@cindex extensions @subentry Brian Kernighan's @command{awk}
-@cindex Brian Kernighan's @command{awk} @subentry extensions
-@cindex Kernighan, Brian
-Brian Kernighan
-has made his version available via his home page
-(@pxref{Other Versions}).
-
-This @value{SECTION} describes common extensions that
-originally appeared in his version of @command{awk}:
-
-@itemize @value{BULLET}
-@item
-The @samp{**} and @samp{**=} operators
-(@pxref{Arithmetic Ops}
-and
-@ref{Assignment Ops})
-
-@item
-The use of @code{func} as an abbreviation for @code{function}
-(@pxref{Definition Syntax})
-
-@item
-The @code{fflush()} built-in function for flushing buffered output
-(@pxref{I/O Functions})
-
-@ignore
-@item
-The @code{SYMTAB} array, that allows access to @command{awk}'s internal symbol
-table. This feature was never documented for his @command{awk}, largely because
-it is somewhat shakily implemented. For instance, you cannot access arrays
-or array elements through it
-@end ignore
-@end itemize
-
-@xref{Common Extensions} for a full list of the extensions
-available in his @command{awk}.
-
-@node POSIX/GNU
-@appendixsec Extensions in @command{gawk} Not in POSIX @command{awk}
-
-@cindex compatibility mode (@command{gawk}) @subentry extensions
-@cindex extensions @subentry in @command{gawk}, not in POSIX @command{awk}
-@cindex POSIX @subentry @command{gawk} extensions not included in
-The GNU implementation, @command{gawk}, adds a large number of features.
-They can all be disabled with either the @option{--traditional} or
-@option{--posix} options
-(@pxref{Options}).
-
-A number of features have come and gone over the years. This @value{SECTION}
-summarizes the additional features over POSIX @command{awk} that are
-in the current version of @command{gawk}.
-
-@itemize @value{BULLET}
-
-@item
-Additional predefined variables:
-
-@itemize @value{MINUS}
-@item
-The
-@code{ARGIND},
-@code{BINMODE},
-@code{ERRNO},
-@code{FIELDWIDTHS},
-@code{FPAT},
-@code{IGNORECASE},
-@code{LINT},
-@code{PROCINFO},
-@code{RT},
-and
-@code{TEXTDOMAIN}
-variables
-(@pxref{Built-in Variables})
-@end itemize
-
-@item
-Special files in I/O redirections:
-
-@itemize @value{MINUS}
-@item
-The @file{/dev/stdin}, @file{/dev/stdout}, @file{/dev/stderr}, and
-@file{/dev/fd/@var{N}} special @value{FN}s
-(@pxref{Special Files})
-
-@item
-The @file{/inet}, @file{/inet4}, and @file{/inet6} special files for
-TCP/IP networking using @samp{|&} to specify which version of the
-IP protocol to use
-(@pxref{TCP/IP Networking})
-@end itemize
-
-@item
-Changes and/or additions to the language:
-
-@itemize @value{MINUS}
-@item
-The @samp{\x} escape sequence
-(@pxref{Escape Sequences})
-
-@item
-Full support for both POSIX and GNU regexps
-(@pxref{Regexp})
-
-@item
-The ability for @code{FS} and for the third
-argument to @code{split()} to be null strings
-(@pxref{Single Character Fields})
-
-@item
-The ability for @code{RS} to be a regexp
-(@pxref{Records})
-
-@item
-The ability to use octal and hexadecimal constants in @command{awk}
-program source code
-(@pxref{Nondecimal-numbers})
-
-@item
-The @samp{|&} operator for two-way I/O to a coprocess
-(@pxref{Two-way I/O})
-
-@item
-Indirect function calls
-(@pxref{Indirect Calls})
-
-@item
-Directories on the command line produce a warning and are skipped
-(@pxref{Command-line directories})
-
-@item
-Output with @code{print} and @code{printf} need not be fatal
-(@pxref{Nonfatal})
-@end itemize
-
-@item
-New keywords:
-
-@itemize @value{MINUS}
-@item
-The @code{BEGINFILE} and @code{ENDFILE} special patterns
-(@pxref{BEGINFILE/ENDFILE})
-
-@item
-The @code{switch} statement
-(@pxref{Switch Statement})
-@end itemize
-
-@item
-Changes to standard @command{awk} functions:
-
-@itemize @value{MINUS}
-@item
-The optional second argument to @code{close()} that allows closing one end
-of a two-way pipe to a coprocess
-(@pxref{Two-way I/O})
-
-@item
-POSIX compliance for @code{gsub()} and @code{sub()} with @option{--posix}
-
-@item
-The @code{length()} function accepts an array argument
-and returns the number of elements in the array
-(@pxref{String Functions})
-
-@item
-The optional third argument to the @code{match()} function
-for capturing text-matching subexpressions within a regexp
-(@pxref{String Functions})
-
-@item
-Positional specifiers in @code{printf} formats for
-making translations easier
-(@pxref{Printf Ordering})
-
-@item
-The @code{split()} function's additional optional fourth
-argument, which is an array to hold the text of the field separators
-(@pxref{String Functions})
-@end itemize
-
-@item
-Additional functions only in @command{gawk}:
-
-@itemize @value{MINUS}
-@item
-The @code{gensub()}, @code{patsplit()}, and @code{strtonum()} functions
-for more powerful text manipulation
-(@pxref{String Functions})
-
-@item
-The @code{asort()} and @code{asorti()} functions for sorting arrays
-(@pxref{Array Sorting})
-
-@item
-The @code{mktime()}, @code{systime()}, and @code{strftime()}
-functions for working with timestamps
-(@pxref{Time Functions})
-
-@item
-The
-@code{and()},
-@code{compl()},
-@code{lshift()},
-@code{or()},
-@code{rshift()},
-and
-@code{xor()}
-functions for bit manipulation
-(@pxref{Bitwise Functions})
-@c In 4.1, and(), or() and xor() grew the ability to take > 2 arguments
-
-@item
-The @code{isarray()} function to check if a variable is an array or not
-(@pxref{Type Functions})
-
-@item
-The @code{bindtextdomain()}, @code{dcgettext()}, and @code{dcngettext()}
-functions for internationalization
-(@pxref{Programmer i18n})
-
-@ifset INTDIV
-@item
-The @code{intdiv0()} function for doing integer
-division and remainder
-(@pxref{Numeric Functions})
-@end ifset
-@end itemize
-
-@item
-Changes and/or additions in the command-line options:
-
-@itemize @value{MINUS}
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-@item
-The @env{AWKPATH} environment variable for specifying a path search for
-the @option{-f} command-line option
-(@pxref{Options})
-
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-@item
-The @env{AWKLIBPATH} environment variable for specifying a path search for
-the @option{-l} command-line option
-(@pxref{Options})
-
-@item
-The
-@option{-b},
-@option{-c},
-@option{-C},
-@option{-d},
-@option{-D},
-@option{-e},
-@option{-E},
-@option{-g},
-@option{-h},
-@option{-i},
-@option{-l},
-@option{-L},
-@option{-M},
-@option{-n},
-@option{-N},
-@option{-o},
-@option{-O},
-@option{-p},
-@option{-P},
-@option{-r},
-@option{-s},
-@option{-S},
-@option{-t},
-and
-@option{-V}
-short options. Also, the
-ability to use GNU-style long-named options that start with @option{--},
-and the
-@option{--assign},
-@option{--bignum},
-@option{--characters-as-bytes},
-@option{--copyright},
-@option{--debug},
-@option{--dump-variables},
-@option{--exec},
-@option{--field-separator},
-@option{--file},
-@option{--gen-pot},
-@option{--help},
-@option{--include},
-@option{--lint},
-@option{--lint-old},
-@option{--load},
-@option{--non-decimal-data},
-@option{--optimize},
-@option{--no-optimize},
-@option{--posix},
-@option{--pretty-print},
-@option{--profile},
-@option{--re-interval},
-@option{--sandbox},
-@option{--source},
-@option{--traditional},
-@option{--use-lc-numeric},
-and
-@option{--version}
-long options
-(@pxref{Options}).
-@end itemize
-
-@c new ports
-
-@item
-Support for the following obsolete systems was removed from the code
-and the documentation for @command{gawk} @value{PVERSION} 4.0:
-
-@c nested table
-@itemize @value{MINUS}
-@item
-Amiga
-
-@item
-Atari
-
-@item
-BeOS
-
-@item
-Cray
-
-@item
-MIPS RiscOS
-
-@item
-MS-DOS with the Microsoft Compiler
-
-@item
-MS-Windows with the Microsoft Compiler
-
-@item
-NeXT
-
-@item
-SunOS 3.x, Sun 386 (Road Runner)
-
-@item
-Tandem (non-POSIX)
-
-@item
-Prestandard VAX C compiler for VAX/VMS
-
-@item
-GCC for Alpha has not been tested for a while.
-
-@end itemize
-
-@item
-Support for the following obsolete system was removed from the code
-for @command{gawk} @value{PVERSION} 4.1:
-
-@c nested table
-@itemize @value{MINUS}
-@item
-Ultrix
-@end itemize
-
-@item
-Support for the following systems was removed from the code
-for @command{gawk} @value{PVERSION} 4.2:
-
-@c nested table
-@itemize @value{MINUS}
-@item
-MirBSD
-
-@item
-GNU/Linux on Alpha
-@end itemize
-
-@item
-Support for the following systems was removed from the code
-for @command{gawk} @value{PVERSION} 5.2:
-
-
-@c nested table
-@itemize @value{MINUS}
-@item
-OS/2
-
-@item
-DJGPP
-
-@item
-VAX/VMS
-
-@end itemize
-
-@c XXX ADD MORE STUFF HERE
-@end itemize
-
-
-@c This does not need to be in the formal book.
-@ifclear FOR_PRINT
-@node Feature History
-@appendixsec History of @command{gawk} Features
-
-@ignore
-See the thread:
-https://groups.google.com/forum/#!topic/comp.lang.awk/SAUiRuff30c
-This motivated me to add this section.
-@end ignore
-
-@ignore
-I've tried to follow this general order, esp.@: for the 3.0 and 3.1 sections:
- variables
- special files
- language changes (e.g., hex constants)
- differences in standard awk functions
- new gawk functions
- new keywords
- new command-line options
- behavioral changes
- extension API changes
- new / deprecated / removed ports
- installation time stuff
-Within each category, be alphabetical.
-@end ignore
-
-This @value{SECTION} describes the features in @command{gawk}
-over and above those in POSIX @command{awk},
-in the order they were added to @command{gawk}.
-
-Version 2.10 of @command{gawk} introduced the following features:
-
-@itemize @value{BULLET}
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-@item
-The @env{AWKPATH} environment variable for specifying a path search for
-the @option{-f} command-line option
-(@pxref{Options}).
-
-@item
-The @code{IGNORECASE} variable and its effects
-(@pxref{Case-sensitivity}).
-
-@item
-The @file{/dev/stdin}, @file{/dev/stdout}, @file{/dev/stderr} and
-@file{/dev/fd/@var{N}} special @value{FN}s
-(@pxref{Special Files}).
-@end itemize
-
-Version 2.13 of @command{gawk} introduced the following features:
-
-@itemize @value{BULLET}
-@item
-The @code{FIELDWIDTHS} variable and its effects
-(@pxref{Constant Size}).
-
-@item
-The @code{systime()} and @code{strftime()} built-in functions for obtaining
-and printing timestamps
-(@pxref{Time Functions}).
-
-@item
-Additional command-line options
-(@pxref{Options}):
-
-@itemize @value{MINUS}
-@item
-The @option{-W lint} option to provide error and portability checking
-for both the source code and at runtime.
-
-@item
-The @option{-W compat} option to turn off the GNU extensions.
-
-@item
-The @option{-W posix} option for full POSIX compliance.
-@end itemize
-@end itemize
-
-Version 2.14 of @command{gawk} introduced the following feature:
-
-@itemize @value{BULLET}
-@item
-The @code{next file} statement for skipping to the next @value{DF}
-(@pxref{Nextfile Statement}).
-@end itemize
-
-Version 2.15 of @command{gawk} introduced the following features:
-
-@itemize @value{BULLET}
-@item
-New variables (@pxref{Built-in Variables}):
-
-@itemize @value{MINUS}
-@item
-@code{ARGIND}, which tracks the movement of @code{FILENAME}
-through @code{ARGV}.
-
-@item
-@code{ERRNO}, which contains the system error message when
-@code{getline} returns @minus{}1 or @code{close()} fails.
-@end itemize
-
-@item
-The @file{/dev/pid}, @file{/dev/ppid}, @file{/dev/pgrpid}, and
-@file{/dev/user} special @value{FN}s. These have since been removed.
-
-@item
-The ability to delete all of an array at once with @samp{delete @var{array}}
-(@pxref{Delete}).
-
-@item
-Command-line option changes
-(@pxref{Options}):
-
-@itemize @value{MINUS}
-@item
-The ability to use GNU-style long-named options that start with @option{--}.
-
-@item
-The @option{--source} option for mixing command-line and library-file
-source code.
-@end itemize
-@end itemize
-
-Version 3.0 of @command{gawk} introduced the following features:
-
-@itemize @value{BULLET}
-@item
-New or changed variables:
-
-@itemize @value{MINUS}
-@item
-@code{IGNORECASE} changed, now applying to string comparison as well
-as regexp operations
-(@pxref{Case-sensitivity}).
-
-@item
-@code{RT}, which contains the input text that matched @code{RS}
-(@pxref{Records}).
-@end itemize
-
-@item
-Full support for both POSIX and GNU regexps
-(@pxref{Regexp}).
-
-@item
-The @code{gensub()} function for more powerful text manipulation
-(@pxref{String Functions}).
-
-@item
-The @code{strftime()} function acquired a default time format,
-allowing it to be called with no arguments
-(@pxref{Time Functions}).
-
-@item
-The ability for @code{FS} and for the third
-argument to @code{split()} to be null strings
-(@pxref{Single Character Fields}).
-
-@item
-The ability for @code{RS} to be a regexp
-(@pxref{Records}).
-
-@item
-The @code{next file} statement became @code{nextfile}
-(@pxref{Nextfile Statement}).
-
-@item
-The @code{fflush()} function from
-BWK @command{awk}
-(then at Bell Laboratories;
-@pxref{I/O Functions}).
-
-@item
-New command-line options:
-
-@itemize @value{MINUS}
-@item
-The @option{--lint-old} option to
-warn about constructs that are not available in
-the original Version 7 Unix version of @command{awk}
-(@pxref{V7/SVR3.1}).
-
-@item
-The @option{-m} option from BWK @command{awk}. (Brian was
-still at Bell Laboratories at the time.) This was later removed from
-both his @command{awk} and from @command{gawk}.
-
-@item
-The @option{--re-interval} option to provide interval expressions in regexps
-(@pxref{Regexp Operators}).
-
-@item
-The @option{--traditional} option was added as a better name for
-@option{--compat} (@pxref{Options}).
-@end itemize
-
-@item
-The use of GNU Autoconf to control the configuration process
-(@pxref{Quick Installation}).
-
-@item
-Amiga support.
-This has since been removed.
-
-@end itemize
-
-Version 3.1 of @command{gawk} introduced the following features:
-
-@itemize @value{BULLET}
-@item
-New variables
-(@pxref{Built-in Variables}):
-
-@itemize @value{MINUS}
-@item
-@code{BINMODE}, for non-POSIX systems,
-which allows binary I/O for input and/or output files
-(@pxref{PC Using}).
-
-@item
-@code{LINT}, which dynamically controls lint warnings.
-
-@item
-@code{PROCINFO}, an array for providing process-related information.
-
-@item
-@code{TEXTDOMAIN}, for setting an application's internationalization text
domain
-(@pxref{Internationalization}).
-@end itemize
-
-@item
-The ability to use octal and hexadecimal constants in @command{awk}
-program source code
-(@pxref{Nondecimal-numbers}).
-
-@item
-The @samp{|&} operator for two-way I/O to a coprocess
-(@pxref{Two-way I/O}).
-
-@item
-The @file{/inet} special files for TCP/IP networking using @samp{|&}
-(@pxref{TCP/IP Networking}).
-
-@item
-The optional second argument to @code{close()} that allows closing one end
-of a two-way pipe to a coprocess
-(@pxref{Two-way I/O}).
-
-@item
-The optional third argument to the @code{match()} function
-for capturing text-matching subexpressions within a regexp
-(@pxref{String Functions}).
-
-@item
-Positional specifiers in @code{printf} formats for
-making translations easier
-(@pxref{Printf Ordering}).
-
-@item
-A number of new built-in functions:
-
-@itemize @value{MINUS}
-@item
-The @code{asort()} and @code{asorti()} functions for sorting arrays
-(@pxref{Array Sorting}).
-
-@item
-The @code{bindtextdomain()}, @code{dcgettext()} and @code{dcngettext()}
functions
-for internationalization
-(@pxref{Programmer i18n}).
-
-@item
-The @code{extension()} function and the ability to add
-new built-in functions dynamically. This has seen removed.
-It was replaced by the new extension mechanism.
-@xref{Dynamic Extensions}.
-
-@item
-The @code{mktime()} function for creating timestamps
-(@pxref{Time Functions}).
-
-@item
-The @code{and()}, @code{or()}, @code{xor()}, @code{compl()},
-@code{lshift()}, @code{rshift()}, and @code{strtonum()} functions
-(@pxref{Bitwise Functions}).
-@end itemize
-
-@item
-@cindex @code{next file} statement
-The support for @samp{next file} as two words was removed completely
-(@pxref{Nextfile Statement}).
-
-@item
-Additional command-line options
-(@pxref{Options}):
-
-@itemize @value{MINUS}
-@item
-The @option{--dump-variables} option to print a list of all global variables.
-
-@item
-The @option{--exec} option, for use in CGI scripts.
-
-@item
-The @option{--gen-po} command-line option and the use of a leading
-underscore to mark strings that should be translated
-(@pxref{String Extraction}).
-
-@item
-The @option{--non-decimal-data} option to allow non-decimal
-input data
-(@pxref{Nondecimal Data}).
-
-@item
-The @option{--profile} option and @command{pgawk}, the
-profiling version of @command{gawk}, for producing execution
-profiles of @command{awk} programs
-(@pxref{Profiling}).
-
-@item
-The @option{--use-lc-numeric} option to force @command{gawk}
-to use the locale's decimal point for parsing input data
-(@pxref{Conversion}).
-@end itemize
-
-@item
-The use of GNU Automake to help in standardizing the configuration process
-(@pxref{Quick Installation}).
-
-@item
-The use of GNU @command{gettext} for @command{gawk}'s own message output
-(@pxref{Gawk I18N}).
-
-@item
-BeOS support. This was later removed.
-
-@item
-Tandem support. This was later removed.
-
-@item
-The Atari port became officially unsupported and was
-later removed entirely.
-
-@item
-The source code changed to use ISO C standard-style function definitions.
-
-@item
-POSIX compliance for @code{sub()} and @code{gsub()}
-(@pxref{Gory Details}).
-
-@item
-The @code{length()} function was extended to accept an array argument
-and return the number of elements in the array
-(@pxref{String Functions}).
-
-@item
-The @code{strftime()} function acquired a third argument to
-enable printing times as UTC
-(@pxref{Time Functions}).
-@end itemize
-
-Version 4.0 of @command{gawk} introduced the following features:
-
-@itemize @value{BULLET}
-
-@item
-Variable additions:
-
-@itemize @value{MINUS}
-@item
-@code{FPAT}, which allows you to specify a regexp that matches
-the fields, instead of matching the field separator
-(@pxref{Splitting By Content}).
-
-@item
-If @code{PROCINFO["sorted_in"]} exists, @samp{for (iggy in foo)} loops sort the
-indices before looping over them. The value of this element
-provides control over how the indices are sorted before the loop
-traversal starts
-(@pxref{Controlling Scanning}).
-
-@item
-@code{PROCINFO["strftime"]}, which holds
-the default format for @code{strftime()}
-(@pxref{Time Functions}).
-@end itemize
-
-@item
-The special files @file{/dev/pid}, @file{/dev/ppid}, @file{/dev/pgrpid}
-and @file{/dev/user} were removed.
-
-@item
-Support for IPv6 was added via the @file{/inet6} special file.
-@file{/inet4} forces IPv4 and @file{/inet} chooses the system
-default, which is probably IPv4
-(@pxref{TCP/IP Networking}).
-
-@item
-The use of @samp{\s} and @samp{\S} escape sequences in regular expressions
-(@pxref{GNU Regexp Operators}).
-
-@item
-Interval expressions became part of default regular expressions
-(@pxref{Regexp Operators}).
-
-@item
-POSIX character classes work even with @option{--traditional}
-(@pxref{Regexp Operators}).
-
-@item
-@code{break} and @code{continue} became invalid outside a loop,
-even with @option{--traditional}
-(@pxref{Break Statement}, and also see
-@ref{Continue Statement}).
-
-@item
-@code{fflush()}, @code{nextfile}, and @samp{delete @var{array}}
-are allowed if @option{--posix} or @option{--traditional}, since they
-are all now part of POSIX.
-
-@item
-An optional third argument to
-@code{asort()} and @code{asorti()}, specifying how to sort
-(@pxref{String Functions}).
-
-@item
-The behavior of @code{fflush()} changed to match BWK @command{awk}
-and for POSIX; now both @samp{fflush()} and @samp{fflush("")}
-flush all open output redirections
-(@pxref{I/O Functions}).
-
-@item
-The @code{isarray()}
-function which distinguishes if an item is an array
-or not, to make it possible to traverse arrays of arrays
-(@pxref{Type Functions}).
-
-@item
-The @code{patsplit()}
-function which gives the same capability as @code{FPAT}, for splitting
-(@pxref{String Functions}).
-
-@item
-An optional fourth argument to the @code{split()} function,
-which is an array to hold the values of the separators
-(@pxref{String Functions}).
-
-@item
-Arrays of arrays
-(@pxref{Arrays of Arrays}).
-
-@item
-The @code{BEGINFILE} and @code{ENDFILE} special patterns
-(@pxref{BEGINFILE/ENDFILE}).
-
-@item
-Indirect function calls
-(@pxref{Indirect Calls}).
-
-@item
-@code{switch} / @code{case} are enabled by default
-(@pxref{Switch Statement}).
-
-@item
-Command-line option changes
-(@pxref{Options}):
-
-@itemize @value{MINUS}
-@item
-The @option{-b} and @option{--characters-as-bytes} options
-which prevent @command{gawk} from treating input as a multibyte string.
-
-@item
-The redundant @option{--compat}, @option{--copyleft}, and @option{--usage}
-long options were removed.
-
-@item
-The @option{--gen-po} option was finally renamed to the correct
@option{--gen-pot}.
-
-@item
-The @option{--sandbox} option which disables certain features.
-
-@item
-All long options acquired corresponding short options, for use in @samp{#!}
scripts.
-@end itemize
-
-@item
-Directories named on the command line now produce a warning, not a fatal
-error, unless @option{--posix} or @option{--traditional} are used
-(@pxref{Command-line directories}).
-
-@item
-The @command{gawk} internals were rewritten, bringing the @command{dgawk}
-debugger and possibly improved performance
-(@pxref{Debugger}).
-
-@item
-Per the GNU Coding Standards, dynamic extensions must now define
-a global symbol indicating that they are GPL-compatible
-(@pxref{Plugin License}).
-
-@item
-@cindex POSIX mode
-In POSIX mode, string comparisons use @code{strcoll()} / @code{wcscoll()}
-(@pxref{POSIX String Comparison}).
-
-@item
-The option for raw sockets was removed, since it was never implemented
-(@pxref{TCP/IP Networking}).
-
-@item
-Ranges of the form @samp{[d-h]} are treated as if they were in the
-C locale, no matter what kind of regexp is being used, and even if
-@option{--posix}
-(@pxref{Ranges and Locales}).
-
-@item
-Support was removed for the following systems:
-
-@itemize @value{MINUS}
-@item
-Atari
-
-@item
-Amiga
-
-@item
-BeOS
-
-@item
-Cray
-
-@item
-MIPS RiscOS
-
-@item
-MS-DOS with the Microsoft Compiler
-
-@item
-MS-Windows with the Microsoft Compiler
-
-@item
-NeXT
-
-@item
-SunOS 3.x, Sun 386 (Road Runner)
-
-@item
-Tandem (non-POSIX)
-
-@item
-Prestandard VAX C compiler for VAX/VMS
-@end itemize
-@end itemize
-
-Version 4.1 of @command{gawk} introduced the following features:
-
-@itemize @value{BULLET}
-
-@item
-Three new arrays:
-@code{SYMTAB}, @code{FUNCTAB}, and @code{PROCINFO["identifiers"]}
-(@pxref{Auto-set}).
-
-@item
-The three executables @command{gawk}, @command{pgawk}, and @command{dgawk},
were merged into
-one, named just @command{gawk}. As a result the command-line options changed.
-
-@item
-Command-line option changes
-(@pxref{Options}):
-
-@itemize @value{MINUS}
-@item
-The @option{-D} option invokes the debugger.
-
-@item
-The @option{-i} and @option{--include} options
-load @command{awk} library files.
-
-@item
-The @option{-l} and @option{--load} options load compiled dynamic extensions.
-
-@item
-The @option{-M} and @option{--bignum} options enable MPFR.
-
-@item
-The @option{-o} option only does pretty-printing.
-
-@item
-The @option{-p} option is used for profiling.
-
-@item
-The @option{-R} option was removed.
-@end itemize
-
-@item
-Support for high precision arithmetic with MPFR
-(@pxref{Arbitrary Precision Arithmetic}).
-
-@item
-The @code{and()}, @code{or()} and @code{xor()} functions
-changed to allow any number of arguments,
-with a minimum of two
-(@pxref{Bitwise Functions}).
-
-@item
-The dynamic extension interface was completely redone
-(@pxref{Dynamic Extensions}).
-
-@item
-Redirected @code{getline} became allowed inside
-@code{BEGINFILE} and @code{ENDFILE}
-(@pxref{BEGINFILE/ENDFILE}).
-
-@item
-Support for nonfatal I/O
-(@pxref{Nonfatal}).
-
-@item
-The @code{where} command was added to the debugger
-(@pxref{Execution Stack}).
-
-@item
-Support for Ultrix was removed.
-
-@end itemize
-
-Version 4.2 of @command{gawk} introduced the following changes:
-
-@itemize @bullet
-@item
-Changes to @code{ENVIRON} are reflected into @command{gawk}'s
-environment and that of programs that it runs.
-@xref{Auto-set}.
-
-@item
-@code{FIELDWIDTHS} was enhanced to allow skipping characters
-before assigning a value to a field
-(@pxref{Splitting By Content}).
-
-@item
-The @code{PROCINFO["argv"]} array.
-@xref{Auto-set}.
-
-@item
-The maximum number of hexadecimal digits in @samp{\x} escapes
-is now two.
-@xref{Escape Sequences}.
-
-@item
-Strongly typed regexp constants of the form @samp{@@/@dots{}/}
-(@pxref{Strong Regexp Constants}).
-
-@item
-The bitwise functions changed, making negative arguments into
-a fatal error (@pxref{Bitwise Functions}).
-
-@ifset INTDIV
-@item
-The @code{intdiv0()} function.
-@xref{Numeric Functions}.
-@end ifset
-
-@item
-The @code{mktime()} function now accepts an optional
-second argument
-(@pxref{Time Functions}).
-
-@item
-The @code{typeof()} function (@pxref{Type Functions}).
-
-@item
-Optimizations are enabled by default. Use @option{-s} /
-@option{--no-optimize} to disable optimizations.
-
-@item
-For many years, POSIX specified that default field splitting
-only allowed spaces and tabs to separate fields, and this was
-how @command{gawk} behaved with @option{--posix}. As of 2013,
-the standard restored historical behavior, and now default
-field splitting with @option{--posix} also allows newlines to
-separate fields.
-
-@item
-Nonfatal output with @code{print} and @code{printf}.
-@xref{Nonfatal}.
-
-@item
-Retryable I/O via @code{PROCINFO[@var{input-file}, "RETRY"]};
-(@pxref{Retrying Input}).
-
-@item
-Changes to the pretty-printer (@pxref{Profiling}):
-
-@c nested table
-@itemize @value{MINUS}
-@item
-The @option{--pretty-print} option no longer runs the @command{awk}
-program too.
-
-@item
-Comments in the source program are preserved and placed into the
-output file.
-
-@item
-Explicit parentheses for expressions
-in the input are preserved in the generated output.
-@end itemize
-
-@item
-Improvements to the extension API
-(@pxref{Dynamic Extensions}):
-
-@c nested
-@itemize @value{MINUS}
-@item
-The @code{get_file()} function to access open redirections.
-
-@item
-The @code{nonfatal()} function for generating nonfatal error messages.
-
-@item
-Support for GMP and MPFR values.
-
-@item
-Input parsers can now override the default field parsing mechanism
-by specifying explicit locations.
-@end itemize
-
-@item
-Shell startup files are supplied with the distribution and
-installed by @samp{make install} (@pxref{Shell Startup Files}).
-
-@item
-The @command{igawk} program and its manual page are no longer
-installed when @command{gawk} is built.
-@xref{Igawk Program}.
-
-@item
-Support for MirBSD was removed.
-
-@item
-Support for GNU/Linux on Alpha was removed.
-
-@end itemize
-
-Version 5.0 added the following features:
-
-@itemize
-@item
-The @code{PROCINFO["platform"]} array element, which allows you
-to write code that takes the operating system / platform into account.
-@end itemize
-
-Version 5.1 was created to release @command{gawk} with a correct
-major version number for the API. This was overlooked for version 5.0,
-unfortunately. It added the following features:
-
-@itemize
-@item
-The index for this manual was completely reworked.
-
-@item
-Support was added for MSYS2.
-
-@item
-@code{asort()} and @code{asorti()} were changed to
-allow @code{FUNCTAB} and @code{SYMTAB} as the first argument if a
-second destination array is supplied (@pxref{String Functions}).
-
-@item
-The @option{-I}/@option{--trace} options were added to
-print a trace of the byte codes as they execute (@pxref{Options}).
-
-@item
-@code{$0} and the fields are now cleared before starting a
-@code{BEGINFILE} rule (@pxref{BEGINFILE/ENDFILE}).
-
-@item
-Several example programs in the manual were updated to their modern
-POSIX equivalents.
-
-@item
-The ``no effect'' lint warnings from @option{--lint} were fixed up
-and now behave more sanely (@pxref{Options}).
-
-@item
-Handling of Infinity and NaN values were improved.
-@xref{Math Definitions}, and also see
-@ref{POSIX Floating Point Problems}.
-@end itemize
-
-Version 5.2 added the following features:
-
-@itemize
-@item
-The @code{mkbool()} built-in function
-(@pxref{Boolean Functions}).
-
-@item
-Interval expressions in regular expressions are
-enabled by default (@pxref{Interval Expressions}).
-
-@item
-Support for the FNV1-A hash algorithm for its hash function
-(@pxref{Other Environment Variables}).
-
-@item
-The @command{gawkbug} script for reporting bugs
-(@pxref{Bug address}).
-
-@cindex Kelly, Terence
-@item
-Terence Kelly's persistent memory allocator (PMA) was
-added, allowing the use of persistent data on certain systems
-(@pxref{Persistent Memory}).
-
-@item
-@code{PROCINFO["pma"]} exists if the PMA allocator is compiled
-in (@pxref{Auto-set}).
-
-@end itemize
-
-Version 5.3 added the following features:
-
-@itemize
-@item
-Comma separated value (CSV) field splitting and the @option{--csv}
-command-line option
-(@pxref{Comma Separated Fields}).
-
-@item
-@code{PROCINFO["CSV"]} exists if @command{gawk} was invoked
-with @option{--csv} (@pxref{Auto-set}).
-
-@item
-The @code{do_csv} API information variable
-(@pxref{Extension API Informational Variables}).
-
-@item
-The ability to make @command{gawk} buffer output to pipes
-(@pxref{Noflush}).
-
-@item
-The @samp{\u} escape sequence
-(@pxref{Escape Sequences}).
-
-@item
-The need for GNU @code{libsigsegv} was removed from @command{gawk}.
-The value-add was never very much and it caused problems in some
-environments.
-
-@end itemize
-
-@c XXX ADD MORE STUFF HERE
-@end ifclear
-
-@node Common Extensions
-@appendixsec Common Extensions Summary
-
-@cindex extensions @subentry Brian Kernighan's @command{awk}
-@cindex extensions @subentry @command{mawk}
-The following table summarizes the common extensions supported
-by @command{gawk}, Brian Kernighan's @command{awk}, and @command{mawk},
-the three most widely used freely available versions of @command{awk}
-(@pxref{Other Versions}).
-
-@multitable {@file{/dev/stderr} special file} {BWK @command{awk}}
{@command{mawk}} {@command{gawk}} {Now standard}
-@headitem Feature @tab BWK @command{awk} @tab @command{mawk} @tab
@command{gawk} @tab Now standard
-@item @code{**} and @code{**=} operators @tab X @tab @tab X @tab
-@item @samp{\x} escape sequence @tab X @tab X @tab X @tab
-@item @samp{\u} escape sequence @tab X @tab @tab X @tab
-@item @file{/dev/stdin} special file @tab X @tab X @tab X @tab
-@item @file{/dev/stdout} special file @tab X @tab X @tab X @tab
-@item @file{/dev/stderr} special file @tab X @tab X @tab X @tab
-@item @code{BINMODE} variable @tab @tab X @tab X @tab
-@item CSV support @tab X @tab @tab X @tab
-@item @code{FS} as null string @tab X @tab X @tab X @tab
-@item @code{delete} without subscript @tab X @tab X @tab X @tab X
-@item @code{fflush()} function @tab X @tab X @tab X @tab X
-@item @code{func} keyword @tab X @tab @tab X @tab
-@item @code{length()} of an array @tab X @tab X @tab X @tab
-@item @code{nextfile} statement @tab X @tab X @tab X @tab X
-@item @code{RS} as regexp @tab X @tab X @tab X @tab
-@item Time-related functions @tab @tab X @tab X @tab
-@end multitable
-
-@node Ranges and Locales
-@appendixsec Regexp Ranges and Locales: A Long Sad Story
-
-This @value{SECTION} describes the confusing history of ranges within
-regular expressions and their interactions with locales, and how this
-affected different versions of @command{gawk}.
-
-@cindex ASCII
-@cindex EBCDIC
-The original Unix tools that worked with regular expressions defined
-character ranges (such as @samp{[a-z]}) to match any character between
-the first character in the range and the last character in the range,
-inclusive. Ordering was based on the numeric value of each character
-in the machine's native character set. Thus, on ASCII-based systems,
-@samp{[a-z]} matched all the lowercase letters, and only the lowercase
-letters, as the numeric values for the letters from @samp{a} through
-@samp{z} were contiguous. (On an EBCDIC system, the range @samp{[a-z]}
-includes additional nonalphabetic characters as well.)
-
-Almost all introductory Unix literature explained range expressions
-as working in this fashion, and in particular, would teach that the
-``correct'' way to match lowercase letters was with @samp{[a-z]}, and
-that @samp{[A-Z]} was the ``correct'' way to match uppercase letters.
-And indeed, this was true.@footnote{And Life was good.}
-
-The 1992 POSIX standard introduced the idea of locales (@pxref{Locales}).
-Because many locales include other letters besides the plain 26
-letters of the English alphabet, the POSIX standard added
-character classes (@pxref{Bracket Expressions}) as a way to match
-different kinds of characters besides the traditional ones in the ASCII
-character set.
-
-However, the standard @emph{changed} the interpretation of range expressions.
-In the @code{"C"} and @code{"POSIX"} locales, a range expression like
-@samp{[a-dx-z]} is still equivalent to @samp{[abcdxyz]}, as in ASCII.
-But outside those locales, the ordering was defined to be based on
-@dfn{collation order}.
-
-What does that mean?
-In many locales, @samp{A} and @samp{a} are both less than @samp{B}.
-In other words, these locales sort characters in dictionary order,
-and @samp{[a-dx-z]} is typically not equivalent to @samp{[abcdxyz]};
-instead, it might be equivalent to @samp{[ABCXYabcdxyz]}, for example.
-
-This point needs to be emphasized: much literature teaches that you should
-use @samp{[a-z]} to match a lowercase character. But on systems with
-non-ASCII locales, this also matches all of the uppercase characters
-except @samp{A} or @samp{Z}! This was a continuous cause of confusion, even
well
-into the twenty-first century.
-
-To demonstrate these issues, the following example uses the @code{sub()}
-function, which does text replacement (@pxref{String Functions}). Here,
-the intent is to remove trailing uppercase characters:
-
-@example
-$ @kbd{echo something1234abc | gawk-3.1.8 '@{ sub("[A-Z]*$", ""); print @}'}
-@print{} something1234a
-@end example
-
-@noindent
-This output is unexpected, as the @samp{bc} at the end of
-@samp{something1234abc} should not normally match @samp{[A-Z]*}.
-This result is due to the locale setting (and thus you may not see
-it on your system).
-
-@cindex Unicode
-@cindex ASCII
-Similar considerations apply to other ranges. For example, @samp{["-/]}
-is perfectly valid in ASCII, but is not valid in many Unicode locales,
-such as @code{en_US.UTF-8}.
-
-Early versions of @command{gawk} used regexp matching code that was not
-locale-aware, so ranges had their traditional interpretation.
-
-When @command{gawk} switched to using locale-aware regexp matchers,
-the problems began; especially as both GNU/Linux and commercial Unix
-vendors started implementing non-ASCII locales, @emph{and making them
-the default}. Perhaps the most frequently asked question became something
-like, ``Why does @samp{[A-Z]} match lowercase letters?!?''
-
-@cindex Berry, Karl
-This situation existed for close to 10 years, if not more, and
-the @command{gawk} maintainer grew weary of trying to explain that
-@command{gawk} was being nicely standards-compliant, and that the issue
-was in the user's locale. During the development of @value{PVERSION} 4.0,
-he modified @command{gawk} to always treat ranges in the original,
-pre-POSIX fashion, unless @option{--posix} was used
(@pxref{Options}).@footnote{And
-thus was born the Campaign for Rational Range Interpretation (or
-RRI). A number of GNU tools have already implemented this change,
-or will soon. Thanks to Karl Berry for coining the phrase ``Rational
-Range Interpretation.''}
-
-Fortunately, shortly before the final release of @command{gawk} 4.0,
-the maintainer learned that the 2008 standard had changed the
-definition of ranges, such that outside the @code{"C"} and @code{"POSIX"}
-locales, the meaning of range expressions was @emph{undefined}.@footnote{See
-@uref{https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05,
the standard}
-and
-@uref{https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xbd_chap09.html#tag_21_09_03_05,
its rationale}.}
-
-By using this lovely technical term, the standard gives license
-to implementers to implement ranges in whatever way they choose.
-The @command{gawk} maintainer chose to apply the pre-POSIX meaning
-both with the default regexp matching and when @option{--traditional} or
-@option{--posix} are used.
-In all cases @command{gawk} remains POSIX-compliant.
-
-@node Contributors
-@appendixsec Major Contributors to @command{gawk}
-@cindex @command{gawk} @subentry list of contributors to
-@quotation
-@i{Always give credit where credit is due.}
-@author Anonymous
-@end quotation
-
-This @value{SECTION} names the major contributors to @command{gawk}
-and/or this @value{DOCUMENT}, in approximate chronological order:
-
-@itemize @value{BULLET}
-@item
-@cindex Aho, Alfred
-@cindex Weinberger, Peter
-@cindex Kernighan, Brian
-Dr.@: Alfred V.@: Aho,
-Dr.@: Peter J.@: Weinberger, and
-Dr.@: Brian W.@: Kernighan, all of Bell Laboratories,
-designed and implemented Unix @command{awk},
-from which @command{gawk} gets the majority of its feature set.
-
-@item
-@cindex Rubin, Paul
-Paul Rubin
-did the initial design and implementation in 1986, and wrote
-the first draft (around 40 pages) of this @value{DOCUMENT}.
-
-@item
-@cindex Fenlason, Jay
-Jay Fenlason
-finished the initial implementation.
-
-@item
-@cindex Close, Diane
-Diane Close
-revised the first draft of this @value{DOCUMENT}, bringing it
-to around 90 pages.
-
-@item
-@cindex Stallman, Richard
-Richard Stallman
-helped finish the implementation and the initial draft of this
-@value{DOCUMENT}.
-He is also the founder of the FSF and the GNU Project.
-
-@item
-@cindex Woods, John
-John Woods
-contributed parts of the code (mostly fixes) in
-the initial version of @command{gawk}.
-
-@item
-@cindex Trueman, David
-In 1988,
-David Trueman
-took over primary maintenance of @command{gawk},
-making it compatible with ``new'' @command{awk}, and
-greatly improving its performance.
-
-@item
-@cindex Kwok, Conrad
-@cindex Garfinkle, Scott
-@cindex Williams, Kent
-Conrad Kwok,
-Scott Garfinkle,
-and
-Kent Williams
-did the initial ports to MS-DOS with various versions of MSC.
-
-@item
-@cindex Rankin, Pat
-Pat Rankin
-provided the VMS port and its documentation.
-
-@item
-@cindex Peterson, Hal
-Hal Peterson
-provided help in porting @command{gawk} to Cray systems.
-(This is no longer supported.)
-
-@item
-@cindex Rommel, Kai Uwe
-Kai Uwe Rommel
-provided the initial port to OS/2 and its documentation.
-
-@item
-@cindex Jaegermann, Michal
-Michal Jaegermann
-provided the port to Atari systems and its documentation.
-(This port is no longer supported.)
-He continues to provide portability checking,
-and has done a lot of work to make sure @command{gawk}
-works on non-32-bit systems.
-
-@item
-@cindex Fish, Fred
-Fred Fish
-provided the port to Amiga systems and its documentation.
-(With Fred's sad passing, this is no longer supported.)
-
-@item
-@cindex Deifik, Scott
-Scott Deifik
-formerly maintained the MS-DOS port using DJGPP.
-
-@item
-@cindex Zaretskii, Eli
-Eli Zaretskii
-currently maintains the MS-Windows port using MinGW.
-
-@item
-@cindex Grigera, Juan
-Juan Grigera
-provided a port to Windows32 systems.
-(This is no longer supported.)
-
-
-@item
-@cindex Hankerson, Darrel
-For many years,
-Dr.@: Darrel Hankerson
-acted as coordinator for the various ports to different PC platforms
-and created binary distributions for various PC operating systems.
-He was also instrumental in keeping the documentation up to date for
-the various PC platforms.
-
-@item
-@cindex Zoulas, Christos
-Christos Zoulas
-provided the @code{extension()}
-built-in function for dynamically adding new functions.
-(This was obsoleted at @command{gawk} 4.1.)
-
-@item
-@cindex Kahrs, J@"urgen
-J@"urgen Kahrs
-contributed the initial version of the TCP/IP networking
-code and documentation, and motivated the inclusion of the @samp{|&} operator.
-
-@item
-@cindex Davies, Stephen
-Stephen Davies
-provided the initial port to Tandem systems and its documentation.
-(However, this is no longer supported.)
-He was also instrumental in the initial work to integrate the
-byte-code internals into the @command{gawk} code base.
-Additionally, he did most of the work enabling the pretty-printer
-to preserve and output comments.
-
-@item
-@cindex Woehlke, Matthew
-Matthew Woehlke
-provided improvements for Tandem's POSIX-compliant systems.
-
-@item
-@cindex Brown, Martin
-Martin Brown
-provided the port to BeOS and its documentation.
-(This is no longer supported.)
-
-@item
-@cindex Peters, Arno
-Arno Peters
-did the initial work to convert @command{gawk} to use
-GNU Automake and GNU @command{gettext}.
-
-@item
-@cindex Broder, Alan J.@:
-Alan J.@: Broder
-provided the initial version of the @code{asort()} function
-as well as the code for the optional third argument to the
-@code{match()} function.
-
-@item
-@cindex Buening, Andreas
-Andreas Buening
-updated the @command{gawk} port for OS/2.
-
-@item
-@cindex Hasegawa, Isamu
-Isamu Hasegawa,
-of IBM in Japan, contributed support for multibyte characters.
-
-@item
-@cindex Benzinger, Michael
-Michael Benzinger contributed the initial code for @code{switch} statements.
-
-@item
-@cindex McPhee, Patrick T.J.@:
-Patrick T.J.@: McPhee contributed the code for dynamic loading in Windows32
-environments.
-(This is no longer supported.)
-
-@item
-@cindex Wallin, Anders
-Anders Wallin helped keep the VMS port going for several years.
-
-@item
-@cindex Gordon, Assaf
-Assaf Gordon contributed the initial code to implement the
-@option{--sandbox} option.
-
-@item
-@cindex Haque, John
-John Haque made the following contributions:
-
-@itemize @value{MINUS}
-@item
-The modifications to convert @command{gawk}
-into a byte-code interpreter, including the debugger
-
-@item
-The addition of true arrays of arrays
-
-@item
-The additional modifications for support of arbitrary-precision arithmetic
-
-@item
-The initial text of
-@ref{Arbitrary Precision Arithmetic}
-
-@item
-The work to merge the three versions of @command{gawk}
-into one, for the 4.1 release
-
-@item
-Improved array internals for arrays indexed by integers
-
-@item
-The improved array sorting features were also driven by John, together
-with Pat Rankin
-@end itemize
-
-@cindex Papadopoulos, Panos
-@item
-Panos Papadopoulos contributed the original text for @ref{Include Files}.
-
-@item
-@cindex Yawitz, Efraim
-Efraim Yawitz contributed the original text for @ref{Debugger}.
-
-@item
-@cindex Schorr, Andrew
-The development of the extension API first released with
-@command{gawk} 4.1 was driven primarily by
-Arnold Robbins and Andrew Schorr, with notable contributions from
-the rest of the development team.
-
-@cindex Malmberg, John
-@item
-John Malmberg contributed significant improvements to the
-OpenVMS port and the related documentation.
-
-@item
-@cindex Colombo, Antonio
-Antonio Giovanni Colombo rewrote a number of examples in the early
-chapters that were severely dated, for which I am incredibly grateful.
-He also provided and maintains the Italian translation.
-
-@item
-@cindex Curreli, Marco
-Marco Curreli, together with Antonio Colombo, translated this
-@value{DOCUMENT} into Italian. It is included in the @command{gawk}
-distribution.
-
-@item
-@cindex Guerrero, Juan Manuel
-Juan Manuel Guerrero took over maintenance of the DJGPP port.
-
-@item
-@cindex Jannick
-``Jannick'' provided support for MSYS2.
-
-@item
-@cindex Robbins @subentry Arnold
-Arnold Robbins
-has been working on @command{gawk} since 1988, at first
-helping David Trueman, and as the primary maintainer since around 1994.
-@end itemize
-
-@node History summary
-@appendixsec Summary
-
-@itemize @value{BULLET}
-@item
-The @command{awk} language has evolved over time. The first release
-was with V7 Unix, circa 1978. In 1987, for System V Release 3.1,
-major additions, including user-defined functions, were made to the language.
-Additional changes were made for System V Release 4, in 1989.
-Since then, further minor changes have happened under the auspices of the
-POSIX standard.
-
-@item
-Brian Kernighan's @command{awk} provides a small number of extensions
-that are implemented in common with other versions of @command{awk}.
-
-@item
-@command{gawk} provides a large number of extensions over POSIX @command{awk}.
-They can be disabled with either the @option{--traditional} or @option{--posix}
-options.
-
-@item
-@cindex ASCII
-@cindex EBCDIC
-The interaction of POSIX locales and regexp matching in @command{gawk} has
been confusing over
-the years. Today, @command{gawk} implements Rational Range Interpretation,
where
-ranges of the form @samp{[a-z]} match @emph{only} the characters numerically
between
-@samp{a} through @samp{z} in the machine's native character set. Usually this
is ASCII,
-but it can be EBCDIC on IBM S/390 systems.
-
-@item
-Many people have contributed to @command{gawk} development over the years.
-We hope that the list provided in this @value{CHAPTER} is complete and gives
-the appropriate credit where credit is due.
-
-@end itemize
-
-@node Installation
-@appendix Installing @command{gawk}
-
-@c last two commas are part of see also
-@cindex operating systems
-@cindex operating systems @seealso{GNU/Linux}
-@cindex operating systems @seealso{PC operating systems}
-@cindex operating systems @seealso{Unix}
-@cindex @command{gawk} @subentry installing
-@cindex installing @command{gawk}
-This appendix provides instructions for installing @command{gawk} on the
-various platforms that are supported by the developers. The primary
-developer supports GNU/Linux (and Unix), whereas the other ports are
-contributed.
-@xref{Bugs}
-for the email addresses of the people who maintain
-the respective ports.
-
-@menu
-* Gawk Distribution:: What is in the @command{gawk} distribution.
-* Unix Installation:: Installing @command{gawk} under various
- versions of Unix.
-* Non-Unix Installation:: Installation on Other Operating Systems.
-* Bugs:: Reporting Problems and Bugs.
-* Other Versions:: Other freely available @command{awk}
- implementations.
-* Installation summary:: Summary of installation.
-@end menu
-
-@node Gawk Distribution
-@appendixsec The @command{gawk} Distribution
-@cindex source code @subentry @command{gawk}
-
-This @value{SECTION} describes how to get the @command{gawk}
-distribution, how to extract it, and then what is in the various files and
-subdirectories.
-
-@menu
-* Getting:: How to get the distribution.
-* Extracting:: How to extract the distribution.
-* Distribution contents:: What is in the distribution.
-@end menu
-
-@node Getting
-@appendixsubsec Getting the @command{gawk} Distribution
-@cindex @command{gawk} @subentry source code, obtaining
-There are two ways to get GNU software:
-
-@itemize @value{BULLET}
-@item
-Copy it from someone else who already has it.
-
-@cindex FSF (Free Software Foundation)
-@cindex Free Software Foundation (FSF)
-@item
-Retrieve @command{gawk}
-from the Internet host
-@code{ftp.gnu.org}, in the directory @file{/gnu/gawk}.
-Both anonymous @command{ftp} and @code{http} access are supported.
-If you have the @command{wget} program, you can use a command like
-the following:
-
-@example
-wget
https://ftp.gnu.org/gnu/gawk/gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
-@end example
-@end itemize
-
-The GNU software archive is mirrored around the world.
-The up-to-date list of mirror sites is available from
-@uref{https://www.gnu.org/order/ftp.html, the main FSF website}.
-Try to use one of the mirrors; they
-will be less busy, and you can usually find one closer to your site.
-
-You may also retrieve the @command{gawk} source code from the official
-Git repository; for more information see @ref{Accessing The Source}.
-
-@node Extracting
-@appendixsubsec Extracting the Distribution
-@command{gawk} is distributed as several @command{tar} files compressed with
-different compression programs: @command{gzip}, @command{bzip2},
-and @command{xz}. For simplicity, the rest of these instructions assume
-you are using the one compressed with the GNU Gzip program (@command{gzip}).
-
-Once you have the distribution (e.g.,
-@file{gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz}),
-use @command{gzip} to expand the
-file and then use @command{tar} to extract it. You can use the following
-pipeline to produce the @command{gawk} distribution:
-
-@example
-gzip -d -c gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz | tar -xvpf -
-@end example
-
-On a system with GNU @command{tar}, you can let @command{tar}
-do the decompression for you:
-
-@example
-tar -xvpzf gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
-@end example
-
-@noindent
-Extracting the archive
-creates a directory named @file{gawk-@value{VERSION}.@value{PATCHLEVEL}}
-in the current directory.
-
-The distribution @value{FN} is of the form
-@file{gawk-@var{V}.@var{R}.@var{P}.tar.gz}.
-The @var{V} represents the major version of @command{gawk},
-the @var{R} represents the current release of version @var{V}, and
-the @var{P} represents a @dfn{patch level}, meaning that minor bugs have
-been fixed in the release. The current patch level is @value{PATCHLEVEL},
-but when retrieving distributions, you should get the version with the highest
-version, release, and patch level. (Note, however, that patch levels greater
than
-or equal to 60 denote ``beta'' or nonproduction software; you might not want
-to retrieve such a version unless you don't mind experimenting.)
-If you are not on a Unix or GNU/Linux system, you need to make other
arrangements
-for getting and extracting the @command{gawk} distribution. You should consult
-a local expert.
-
-@node Distribution contents
-@appendixsubsec Contents of the @command{gawk} Distribution
-@cindex @command{gawk} @subentry distribution
-
-The @command{gawk} distribution has a number of C source files,
-documentation files,
-subdirectories, and files related to the configuration process
-(@pxref{Unix Installation}),
-as well as several subdirectories related to different non-Unix
-operating systems:
-
-@table @asis
-@item Various @samp{.c}, @samp{.y}, and @samp{.h} files
-These files contain the actual @command{gawk} source code.
-@end table
-
-@table @file
-@item support/*
-C header and source files for routines that @command{gawk}
-uses, but that are not part of its core functionality.
-For example, argument parsing, regular expression matching,
-and random number generating routines are all kept here.
-
-@item ABOUT-NLS
-A file containing information about GNU @command{gettext} and translations.
-
-@item AUTHORS
-A file with some information about the authorship of @command{gawk}.
-It exists only to satisfy the pedants at the Free Software Foundation.
-
-@item README
-@itemx README_d/README.*
-Descriptive files: @file{README} for @command{gawk} under Unix and the
-rest for the various hardware and software combinations.
-
-@item INSTALL
-A file providing an overview of the configuration and installation process.
-
-@item ChangeLog
-A detailed list of source code changes as bugs are fixed or improvements made.
-There are similar files in all of the subdirectories.
-
-@item ChangeLog.0
-@itemx ChangeLog.1
-Older lists of source code changes.
-There are similar files in all of the subdirectories.
-
-@item NEWS
-A list of changes to @command{gawk} since the last release or patch.
-There may be similar files in other subdirectories.
-
-@item NEWS.0
-@itemx NEWS.1
-Older lists of changes to @command{gawk}.
-There may be similar files in other subdirectories.
-
-@item COPYING
-The GNU General Public License.
-
-@item POSIX.STD
-A description of behaviors in the POSIX standard for @command{awk} that
-are left undefined, or where @command{gawk} may not comply fully, as well
-as a list of things that the POSIX standard should describe but does not.
-
-@cindex artificial intelligence, @command{gawk} and
-@item doc/awkforai.txt
-Pointers to the original draft of
-a short article describing why @command{gawk} is a good language for
-artificial intelligence (AI) programming.
-
-@item doc/bc_notes
-A brief description of @command{gawk}'s ``byte code'' internals.
-
-@item doc/README.card
-@itemx doc/ad.block
-@itemx doc/awkcard.in
-@itemx doc/cardfonts
-@itemx doc/colors
-@itemx doc/macros
-@itemx doc/no.colors
-@itemx doc/setter.outline
-The @command{troff} source for a five-color @command{awk} reference card.
-A modern version of @command{troff} such as GNU @command{troff}
(@command{groff}) is
-needed to produce the color version. See the file @file{README.card}
-for instructions if you have an older @command{troff}.
-
-@item doc/gawk.1
-The @command{troff} source for a manual page describing @command{gawk}.
-This is distributed for the convenience of Unix users.
-
-@cindex Texinfo
-@item doc/gawktexi.in
-@itemx doc/sidebar.awk
-The Texinfo source file for this @value{DOCUMENT}.
-It should be processed by @file{doc/sidebar.awk}
-before processing with @command{texi2dvi} or @command{texi2pdf}
-to produce a printed document, and
-with @command{makeinfo} to produce an Info or HTML file.
-The @file{Makefile} takes care of this processing and produces
-printable output via @command{texi2dvi} or @command{texi2pdf}.
-
-@item doc/gawk.texi
-The file produced after processing @file{gawktexi.in}
-with @file{sidebar.awk}.
-
-@item doc/gawk.info
-The generated Info file for this @value{DOCUMENT}.
-
-@item doc/gawkinet.texi
-The Texinfo source file for
-@ifinfo
-@ref{Top, , General Introduction, gawkinet, @value{GAWKINETTITLE}}.
-@end ifinfo
-@ifnotinfo
-@cite{@value{GAWKINETTITLE}}.
-@end ifnotinfo
-It should be processed with @TeX{}
-(via @command{texi2dvi} or @command{texi2pdf})
-to produce a printed document and
-with @command{makeinfo} to produce an Info or HTML file.
-
-@item doc/gawkinet.info
-The generated Info file for
-@cite{@value{GAWKINETTITLE}}.
-
-@item doc/gawkworkflow.texi
-The Texinfo source file for
-@ifinfo
-@ref{Top, , General Introduction, gawkworkflow, @value{GAWKWORKFLOWTITLE}}.
-@end ifinfo
-@ifnotinfo
-@cite{@value{GAWKWORKFLOWTITLE}}.
-@end ifnotinfo
-It should be processed with @TeX{}
-(via @command{texi2dvi} or @command{texi2pdf})
-to produce a printed document and
-with @command{makeinfo} to produce an Info or HTML file.
-
-@item doc/gawkworkflow.info
-The generated Info file for
-@cite{@value{GAWKWORKFLOWTITLE}}.
-
-@item doc/pm-gawk.texi
-The Texinfo source file for
-@ifinfo
-@ref{Top, , General Introduction, pm-gawk, @value{PMGAWKTITLE}}.
-@end ifinfo
-@ifnotinfo
-@cite{@value{PMGAWKTITLE}}.
-@end ifnotinfo
-It should be processed with @TeX{}
-(via @command{texi2dvi} or @command{texi2pdf})
-to produce a printed document and
-with @command{makeinfo} to produce an Info or HTML file.
-
-@item doc/pm-gawk.info
-The generated Info file for
-@cite{@value{PMGAWKTITLE}}.
-
-@item doc/pm-gawk.1
-The @command{troff} source for a manual page describing the
-persistent memory features presented in @ref{Persistent Memory}.
-
-@item doc/igawk.1
-The @command{troff} source for a manual page describing the @command{igawk}
-program presented in
-@ref{Igawk Program}.
-(Since @command{gawk} can do its own @code{@@include} processing,
-neither @command{igawk} nor @file{igawk.1} are installed.)
-
-@item doc/it/*
-Files for the Italian translation of this @value{DOCUMENT}, produced and
-contributed by Antonio Colombo and Marco Curreli.
-
-@item doc/Makefile.in
-The input file used during the configuration process to generate the
-actual @file{Makefile} for creating the documentation.
-
-@item Makefile.am
-@itemx */Makefile.am
-Files used by the GNU Automake software for generating
-the @file{Makefile.in} files used by Autoconf and
-@command{configure}.
-
-@item Makefile.in
-@itemx aclocal.m4
-@itemx build-aux/*
-@itemx configh.in
-@itemx configure.ac
-@itemx configure
-@itemx custom.h
-@itemx missing_d/*
-@itemx m4/*
-These files and subdirectories are used when configuring and compiling
-@command{gawk} for various Unix systems. Most of them are explained
-in @ref{Unix Installation}. The rest are there to support the main
-infrastructure.
-
-@item po/*
-The @file{po} library contains message translations.
-
-@item awklib/extract.awk
-@itemx awklib/Makefile.am
-@itemx awklib/Makefile.in
-@itemx awklib/eg/*
-The @file{awklib} directory contains a copy of @file{extract.awk}
-(@pxref{Extract Program}),
-which can be used to extract the sample programs from the Texinfo
-source file for this @value{DOCUMENT}. It also contains a @file{Makefile.in}
file, which
-@command{configure} uses to generate a @file{Makefile}.
-@file{Makefile.am} is used by GNU Automake to create @file{Makefile.in}.
-The library functions from
-@ref{Library Functions},
-are included as ready-to-use files in the @command{gawk} distribution.
-They are installed as part of the installation process.
-The rest of the programs in this @value{DOCUMENT} are available in appropriate
-subdirectories of @file{awklib/eg}.
-
-@item extension/*
-The source code, manual pages, and infrastructure files for
-the sample extensions included with @command{gawk}.
-@xref{Dynamic Extensions}, for more information.
-
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-@item extras/*
-Additional non-essential files. Currently, this directory contains some shell
-startup files to be installed in @file{/etc/profile.d} to aid in manipulating
-the @env{AWKPATH} and @env{AWKLIBPATH} environment variables.
-@xref{Shell Startup Files}, for more information.
-
-@item posix/*
-Files needed for building @command{gawk} on POSIX-compliant systems.
-
-@item pc/*
-Files needed for building @command{gawk} under MS-Windows
-(@pxref{PC Installation} for details).
-
-@item vms/*
-Files needed for building @command{gawk} under OpenVMS
-(@pxref{OpenVMS Installation} for details).
-
-@item test/*
-A test suite for
-@command{gawk}. You can use @samp{make check} from the top-level
@command{gawk}
-directory to run your version of @command{gawk} against the test suite.
-If @command{gawk} successfully passes @samp{make check}, then you can
-be confident of a successful port.
-@end table
-
-@node Unix Installation
-@appendixsec Compiling and Installing @command{gawk} on Unix-Like Systems
-
-Usually, you can compile and install @command{gawk} by typing only two
-commands. However, if you use an unusual system, you may need
-to configure @command{gawk} for your system yourself.
-
-@menu
-* Quick Installation:: Compiling @command{gawk} under Unix.
-* Shell Startup Files:: Shell convenience functions.
-* Additional Configuration Options:: Other compile-time options.
-* Configuration Philosophy:: How it's all supposed to work.
-* Compiling from Git:: Compiling from Git.
-* Building the Documentation:: Building the Documentation.
-@end menu
-
-@node Quick Installation
-@appendixsubsec Compiling @command{gawk} for Unix-Like Systems
-
-@menu
-* Compiling with MPFR:: Building with MPFR.
-@end menu
-
-The normal installation steps should work on all modern commercial
-Unix-derived systems, GNU/Linux, BSD-based systems, and the Cygwin
-environment for MS-Windows.
-
-After you have extracted the @command{gawk} distribution, @command{cd}
-to @file{gawk-@value{VERSION}.@value{PATCHLEVEL}}. As with most GNU
-software, you configure @command{gawk} for your system by running the
-@command{configure} program. This program is a Bourne shell script that
-is generated automatically using GNU Autoconf.
-@ifnotinfo
-(The Autoconf software is
-described fully in
-@cite{Autoconf---Generating Automatic Configuration Scripts},
-which can be found online at
-@uref{https://www.gnu.org/software/autoconf/manual/index.html,
-the Free Software Foundation's website}.)
-@end ifnotinfo
-@ifinfo
-(The Autoconf software is described fully starting with
-@ref{Top, , Autoconf, autoconf,Autoconf---Generating Automatic Configuration
Scripts}.)
-@end ifinfo
-
-To configure @command{gawk}, simply run @command{configure}:
-
-@example
-sh ./configure
-@end example
-
-This produces a @file{Makefile} and @file{config.h} tailored to your system.
-The @file{config.h} file describes various facts about your system.
-You might want to edit the @file{Makefile} to
-change the @code{CFLAGS} variable, which controls
-the command-line options that are passed to the C compiler (such as
-optimization levels or compiling for debugging).
-
-Alternatively, you can add your own values for most @command{make}
-variables on the command line, such as @code{CC} and @code{CFLAGS}, when
-running @command{configure}:
-
-@example
-CC=cc CFLAGS=-g sh ./configure
-@end example
-
-@noindent
-See the file @file{INSTALL} in the @command{gawk} distribution for
-all the details.
-
-After you have run @command{configure} and possibly edited the @file{Makefile},
-type:
-
-@example
-make
-@end example
-
-@noindent
-Shortly thereafter, you should have an executable version of @command{gawk}.
-That's all there is to it!
-To verify that @command{gawk} is working properly,
-run @samp{make check}. All of the tests should succeed.
-If these steps do not work, or if any of the tests fail,
-check the files in the @file{README_d} directory to see if you've
-found a known problem. If the failure is not described there,
-send in a bug report (@pxref{Bugs}).
-
-Of course, once you've built @command{gawk}, it is likely that you will
-wish to install it. To do so, you need to run the command @samp{make
-install}, as a user with the appropriate permissions. How to do this
-varies by system, but on many systems you can use the @command{sudo}
-command to do so. The command then becomes @samp{sudo make install}. It
-is likely that you will be asked for your password, and you will have
-to have been set up previously as a user who is allowed to run the
-@command{sudo} command.
-
-
-@node Compiling with MPFR
-@appendixsubsubsec Building With MPFR
-
-@cindex MPFR library, building with
-Use of the MPFR library with @command{gawk}
-is an optional feature: if you have the MPFR and GMP libraries already
installed
-when you configure and build @command{gawk},
-@command{gawk} automatically will be able to use them.
-
-You can install these libraries from source code by fetching them
-from the GNU distribution site at @code{ftp.gnu.org}.
-
-Most modern systems provide package managers which save you the trouble
-of building from source. They fetch and install the library header files
-and binaries for you. You will need to research how to do this for
-your particular system.
-
-@node Shell Startup Files
-@appendixsubsec Shell Startup Files
-
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-@cindex @env{AWKLIBPATH} environment variable
-@cindex environment variables @subentry @env{AWKLIBPATH}
-The distribution contains shell startup files @file{gawk.sh} and
-@file{gawk.csh}, containing functions to aid in manipulating
-the @env{AWKPATH} and @env{AWKLIBPATH} environment variables.
-On a Fedora GNU/Linux system, these files should be installed in
@file{/etc/profile.d};
-on other platforms, the appropriate location may be different.
-
-@table @command
-
-@cindex @command{gawkpath_default} shell function
-@cindex shell function @subentry @command{gawkpath_default}
-@item gawkpath_default
-Reset the @env{AWKPATH} environment variable to its default value.
-
-@cindex @command{gawkpath_prepend} shell function
-@cindex shell function @subentry @command{gawkpath_prepend}
-@item gawkpath_prepend
-Add the argument to the front of the @env{AWKPATH} environment variable.
-
-@cindex @command{gawkpath_append} shell function
-@cindex shell function @subentry @command{gawkpath_append}
-@item gawkpath_append
-Add the argument to the end of the @env{AWKPATH} environment variable.
-
-@cindex @command{gawklibpath_default} shell function
-@cindex shell function @subentry @command{gawklibpath_default}
-@item gawklibpath_default
-Reset the @env{AWKLIBPATH} environment variable to its default value.
-
-@cindex @command{gawklibpath_prepend} shell function
-@cindex shell function @subentry @command{gawklibpath_prepend}
-@item gawklibpath_prepend
-Add the argument to the front of the @env{AWKLIBPATH} environment variable.
-
-@cindex @command{gawklibpath_append} shell function
-@cindex shell function @subentry @command{gawklibpath_append}
-@item gawklibpath_append
-Add the argument to the end of the @env{AWKLIBPATH} environment variable.
-
-@end table
-
-
-@node Additional Configuration Options
-@appendixsubsec Additional Configuration Options
-@cindex @command{gawk} @subentry configuring @subentry options
-@cindex configuration options, @command{gawk}
-
-There are several additional options you may use on the @command{configure}
-command line when compiling @command{gawk} from scratch, including:
-
-@table @code
-
-@cindex @option{--disable-extensions} configuration option
-@cindex configuration option @subentry @option{--disable-extensions}
-@item --disable-extensions
-Disable the extension mechanism within @command{gawk}. With this
-option, it is not possible to use dynamic extensions. This also
-disables configuring and building the sample extensions in the
-@file{extension} directory.
-
-This option may be useful for cross-compiling.
-The default action is to dynamically check if the extensions
-can be configured and compiled.
-
-@cindex @option{--disable-lint} configuration option
-@cindex configuration option @subentry @option{--disable-lint}
-@item --disable-lint
-Disable all lint checking within @command{gawk}. The
-@option{--lint} and @option{--lint-old} options
-(@pxref{Options})
-are accepted, but silently do nothing.
-Similarly, setting the @code{LINT} variable
-(@pxref{User-modified})
-has no effect on the running @command{awk} program.
-
-When used with the GNU Compiler Collection's (GCC's)
-automatic dead-code-elimination, this option
-cuts almost 23K bytes off the size of the @command{gawk}
-executable on GNU/Linux x86_64 systems. Results on other systems and
-with other compilers are likely to vary.
-Using this option may bring you some slight performance improvement.
-
-@quotation CAUTION
-Using this option will cause some of the tests in the test suite
-to fail. This option may be removed at a later date.
-@end quotation
-
-@cindex @option{--disable-mpfr} configuration option
-@cindex configuration option @subentry @option{--disable-mpfr}
-@item --disable-mpfr
-Skip checking for the MPFR and GMP libraries. This is useful
-mainly for the developers, to make sure nothing breaks if
-MPFR support is not available.
-
-@cindex @option{--disable-nls} configuration option
-@cindex configuration option @subentry @option{--disable-nls}
-@item --disable-nls
-Disable all message-translation facilities.
-This is usually not desirable, but it may bring you some slight performance
-improvement.
-
-@cindex @option{--enable-versioned-extension-dir} configuration option
-@cindex configuration option @subentry
@option{--enable-versioned-extension-dir}
-@item --enable-versioned-extension-dir
-Use a versioned directory for extensions. The directory name will
-include the major and minor API versions in it. This makes it possible
-to keep extensions for different API versions on the same system
-without their conflicting with one another.
-
-@end table
-
-Use the command @samp{./configure --help} to see the full list of
-options supplied by @command{configure}.
-
-@node Configuration Philosophy
-@appendixsubsec The Configuration Process
-
-@cindex @command{gawk} @subentry configuring
-This @value{SECTION} is of interest only if you know something about using the
-C language and Unix-like operating systems.
-
-The source code for @command{gawk} generally attempts to adhere to formal
-standards wherever possible. This means that @command{gawk} uses library
-routines that are specified by the ISO C standard and by the POSIX
-operating system interface standard.
-The @command{gawk} source code requires using an ISO C compiler (the 1999
-standard).
-
-Many Unix systems do not support all of either the ISO or the
-POSIX standards. The @file{missing_d} subdirectory in the @command{gawk}
-distribution contains replacement versions of those functions that are
-most likely to be missing.
-
-The @file{config.h} file that @command{configure} creates contains
-definitions that describe features of the particular operating system
-where you are attempting to compile @command{gawk}. The three things
-described by this file are: what header files are available, so that
-they can be correctly included, what (supposedly) standard functions
-are actually available in your C libraries, and various miscellaneous
-facts about your operating system. For example, there may not be an
-@code{st_blksize} element in the @code{stat} structure. In this case,
-@samp{HAVE_STRUCT_STAT_ST_BLKSIZE} is undefined.
-
-@cindex @code{custom.h} file
-It is possible for your C compiler to lie to @command{configure}. It may
-do so by not exiting with an error when a library function is not
-available. To get around this, edit the @file{custom.h} file.
-Use an @samp{#ifdef} that is appropriate for your system, and either
-@code{#define} any constants that @command{configure} should have defined but
-didn't, or @code{#undef} any constants that @command{configure} defined and
-should not have. The @file{custom.h} file is automatically included by
-the @file{config.h} file.
-
-It is also possible that the @command{configure} program generated by
-Autoconf will not work on your system in some other fashion.
-If you do have a problem, the @file{configure.ac} file is the input for
-Autoconf. You may be able to change this file and generate a
-new version of @command{configure} that works on your system
-(@pxref{Bugs}
-for information on how to report problems in configuring @command{gawk}).
-The same mechanism may be used to send in updates to @file{configure.ac}
-and/or @file{custom.h}.
-
-@node Compiling from Git
-@appendixsubsec Compiling from Git
-
-Building @command{gawk} directly from the development source control
-repository is possible, but not recommended for everyday users, as the
-code may not be as stable as released versions are. If you really do
-want to do that, here are the steps:
-
-@example
-git clone https://git.savannah.gnu.org/r/gawk.git
-cd gawk
-./bootstrap.sh && ./configure && make && make check
-@end example
-
-@node Building the Documentation
-@appendixsubsec Building the Documentation
-
-@cindex documentation @subentry building @subentry Info files
-The generated Info documentation is included in the distribution
-@command{tar} files and in the Git source code repository; you should
-not need to rebuild it. However, if it needs to be done, simply running
-@command{make} will do it, assuming that you have a recent enough version
-of @command{makeinfo} installed.
-
-@cindex documentation @subentry building @subentry PDF
-If you wish to build the PDF version of the manuals, you will need
-to have @TeX{} installed, and possibly additional packages that
-provide the necessary fonts and tools, such as @command{dvi2pdf}
-and @command{ps2pdf}. You will also need GNU Troff (@command{groff})
-installed in order to format the reference card and the manual page
-(@pxref{Distribution contents}). Managing this process is beyond the
-scope of this @value{DOCUMENT}.
-
-Assuming you have all you need, then the following commands produce the
-PDF versions of the documentation:
-
-@example
-cd doc
-make pdf
-@end example
-
-@noindent
-This creates PDF versions of all three Texinfo documents included
-in the distribution, as well as of the manual page and the reference card.
-
-@cindex documentation @subentry building @subentry HTML
-Similarly, if you have a recent enough version of @command{makeinfo},
-you can make the HTML version of the manuals with:
-
-@example
-cd doc
-make html
-@end example
-
-@noindent
-This creates HTML versions of all three Texinfo documents included
-in the distribution.
-
-@node Non-Unix Installation
-@appendixsec Installation on Other Operating Systems
-
-This @value{SECTION} describes how to install @command{gawk} on
-various non-Unix systems.
-
-@menu
-* PC Installation:: Installing and Compiling @command{gawk} on
- Microsoft Windows.
-* OpenVMS Installation:: Installing @command{gawk} on OpenVMS.
-@end menu
-
-@node PC Installation
-@appendixsubsec Installation on MS-Windows
-
-@cindex PC operating systems, @command{gawk} on @subentry installing
-@cindex operating systems @subentry PC, @command{gawk} on @subentry installing
-This @value{SECTION} covers installation and usage of @command{gawk}
-on Intel architecture machines running any version of MS-Windows.
-In this @value{SECTION}, the term ``Windows32''
-refers to any of Microsoft Windows 95/98/ME/NT/2000/XP/Vista/7/8/10/11.
-
-See also the @file{README_d/README.pc} file in the distribution.
-
-@menu
-* PC Binary Installation:: Installing a prepared distribution.
-* PC Compiling:: Compiling @command{gawk} for Windows32.
-* PC Using:: Running @command{gawk} on Windows32.
-* Cygwin:: Building and running @command{gawk} for
- Cygwin.
-* MSYS:: Using @command{gawk} In The MSYS Environment.
-@end menu
-
-@node PC Binary Installation
-@appendixsubsubsec Installing a Prepared Distribution for MS-Windows Systems
-@cindex installing @command{gawk} @subentry MS-Windows
-
-@cindex @env{Path} environment variable
-@cindex environment variables @subentry @env{Path}
-The only supported binary distribution for MS-Windows systems
-is that provided by Eli Zaretskii's
@uref{https://sourceforge.net/projects/ezwinports/,
-``ezwinports''} project. Install the compiled @command{gawk} from there.
-Note that to run that port, you need to have the
-@file{libgcc_s_dw2-1.dll} file installed on your system. This file is
-part of the GCC distribution, and should reside either in the same
-directory where you install @file{gawk.exe} or somewhere on your
-system's @env{Path}. You can download this file from
-@uref{https://osdn.net/projects/mingw/releases, the MinGW site}; look under the
-``MinGW.org Compiler Collection (GCC)'' for the @code{LibGCC-1.DLL}
-download.
-
-@node PC Compiling
-@appendixsubsubsec Compiling @command{gawk} for PC Operating Systems
-
-@command{gawk} can be compiled for Windows32 using MinGW (Windows32).
-The file @file{README_d/README.pc} in the @command{gawk} distribution
-contains additional notes, and @file{pc/Makefile} contains important
-information on compilation options.
-
-@cindex compiling @command{gawk} @subentry for MS-Windows
-To build @command{gawk} for Windows32, copy the files in
-the @file{pc} directory (@emph{except} for @file{ChangeLog}) to the
-directory with the rest of the @command{gawk} sources, then invoke
-@command{make} with the appropriate target name as an argument to
-build @command{gawk}. The @file{Makefile} copied from the @file{pc}
-directory contains a configuration section with comments and may need
-to be edited in order to work with your @command{make} utility.
-
-The @file{Makefile} supports a number of targets for building various
-Windows32 versions. A list of targets is printed if the
-@command{make} command is given without a target. As an example,
-to build a native MS-Windows binary of @command{gawk} using the MinGW tools,
-type @samp{make mingw32}.
-
-@node PC Using
-@appendixsubsubsec Using @command{gawk} on PC Operating Systems
-@cindex operating systems @subentry PC, @command{gawk} on
-@cindex PC operating systems, @command{gawk} on
-
-Information in this section applies to the MinGW
-port of @command{gawk}. @xref{Cygwin} for information
-about the Cygwin port.
-
-Under MS-Windows, the MinGW environment supports
-both the @samp{|&} operator and TCP/IP networking
-(@pxref{TCP/IP Networking}).
-
-@cindex search paths
-@cindex search paths @subentry for source files
-@cindex @command{gawk} @subentry MS-Windows version of
-@cindex @code{;} (semicolon) @subentry @env{AWKPATH} variable and
-@cindex semicolon (@code{;}) @subentry @env{AWKPATH} variable and
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-The MS-Windows version of @command{gawk} searches for
-program files as described in @ref{AWKPATH Variable}. However,
-semicolons (rather than colons) separate elements in the @env{AWKPATH}
-variable. If @env{AWKPATH} is not set or is empty, then the default
-search path is @samp{@w{.;c:/lib/awk;c:/gnu/lib/awk}}.
-
-@cindex common extensions @subentry @code{BINMODE} variable
-@cindex extensions @subentry common @subentry @code{BINMODE} variable
-@cindex differences in @command{awk} and @command{gawk} @subentry
@code{BINMODE} variable
-@cindex @code{BINMODE} variable
-Under MS-Windows,
-@command{gawk} (and many other text programs) silently
-translates end-of-line @samp{\r\n} to @samp{\n} on input and @samp{\n}
-to @samp{\r\n} on output. A special @code{BINMODE} variable @value{COMMONEXT}
-allows control over these translations and is interpreted as follows:
-
-@itemize @value{BULLET}
-@item
-If @code{BINMODE} is @code{"r"} or one,
-then
-binary mode is set on read (i.e., no translations on reads).
-
-@item
-If @code{BINMODE} is @code{"w"} or two,
-then
-binary mode is set on write (i.e., no translations on writes).
-
-@item
-If @code{BINMODE} is @code{"rw"} or @code{"wr"} or three,
-binary mode is set for both read and write.
-
-@item
-@code{BINMODE=@var{non-null-string}} is
-the same as @samp{BINMODE=3} (i.e., no translations on
-reads or writes). However, @command{gawk} issues a warning
-message if the string is not one of @code{"rw"} or @code{"wr"}.
-@end itemize
-
-@noindent
-The modes for standard input and standard output are set one time
-only (after the
-command line is read, but before processing any of the @command{awk} program).
-Setting @code{BINMODE} for standard input or
-standard output is accomplished by using an
-appropriate @samp{-v BINMODE=@var{N}} option on the command line.
-@code{BINMODE} is set at the time a file or pipe is opened and cannot be
-changed midstream.
-
-On POSIX-compatible systems, this variable's value has no effect.
-Thus, if you think your program will run on multiple different systems
-and that you may need to use @code{BINMODE}, you should simply set it
-(in the program or on the command line) unconditionally, and not worry
-about the operating system on which your program is running.
-
-The name @code{BINMODE} was chosen to match @command{mawk}
-(@pxref{Other Versions}).
-@command{mawk} and @command{gawk} handle @code{BINMODE} similarly; however,
-@command{mawk} adds a @samp{-W BINMODE=@var{N}} option and an environment
-variable that can set @code{BINMODE}, @code{RS}, and @code{ORS}. The
-files @file{binmode[1-3].awk} (under @file{gnu/lib/awk} in some of the
-prepared binary distributions) have been chosen to match @command{mawk}'s
@samp{-W
-BINMODE=@var{N}} option. These can be changed or discarded; in particular,
-the setting of @code{RS} giving the fewest ``surprises'' is open to debate.
-@command{mawk} uses @samp{RS = "\r\n"} if binary mode is set on read, which is
-appropriate for files with the MS-DOS-style end-of-line.
-
-To illustrate, the following examples set binary mode on writes for standard
-output and other files, and set @code{ORS} as the ``usual'' MS-DOS-style
-end-of-line:
-
-@example
-gawk -v BINMODE=2 -v ORS="\r\n" @dots{}
-@end example
-
-@noindent
-or:
-
-@example
-gawk -v BINMODE=w -f binmode2.awk @dots{}
-@end example
-
-@noindent
-These give the same result as the @samp{-W BINMODE=2} option in
-@command{mawk}.
-The following changes the record separator to @code{"\r\n"} and sets binary
-mode on reads, but does not affect the mode on standard input:
-
-@example
-gawk -v RS="\r\n" -e "BEGIN @{ BINMODE = 1 @}" @dots{}
-@end example
-
-@noindent
-or:
-
-@example
-gawk -f binmode1.awk @dots{}
-@end example
-
-@noindent
-With proper quoting, in the first example the setting of @code{RS} can be
-moved into the @code{BEGIN} rule.
-
-@node Cygwin
-@appendixsubsubsec Using @command{gawk} In The Cygwin Environment
-@cindex compiling @command{gawk} @subentry for Cygwin
-
-@command{gawk} can be built and used ``out of the box'' under MS-Windows
-if you are using the @uref{http://www.cygwin.com, Cygwin environment}.
-This environment provides an excellent simulation of GNU/Linux, using
-Bash, GCC, GNU Make,
-and other GNU programs. Compilation and installation for Cygwin is the
-same as for a Unix system:
-
-@example
-tar -xvpzf gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
-cd gawk-@value{VERSION}.@value{PATCHLEVEL}
-./configure
-make && make check
-@end example
-
-When compared to GNU/Linux on the same system, the @samp{configure}
-step on Cygwin takes considerably longer. However, it does finish,
-and then the @samp{make} proceeds as usual.
-
-@cindex installing @command{gawk} @subentry Cygwin
-You may also install @command{gawk} using the regular Cygwin installer.
-In general Cygwin supplies the latest released version.
-
-Recent versions of Cygwin open all files in binary mode. This means
-that you should use @samp{RS = "\r?\n"} in order to be able to
-handle standard MS-Windows text files with carriage-return plus
-line-feed line endings.
-
-The Cygwin environment supports
-both the @samp{|&} operator and TCP/IP networking
-(@pxref{TCP/IP Networking}).
-
-@node MSYS
-@appendixsubsubsec Using @command{gawk} In The MSYS Environment
-
-In the MSYS environment under MS-Windows, @command{gawk} automatically
-uses binary mode for reading and writing files. Thus, there is no
-need to use the @code{BINMODE} variable.
-
-This can cause problems with other Unix-like components that have
-been ported to MS-Windows that expect @command{gawk} to do automatic
-translation of @code{"\r\n"}, because it won't.
-
-Under MSYS2, compilation using the standard @samp{./configure && make}
-recipe works ``out of the box.''
-
-@node OpenVMS Installation
-@appendixsubsec Compiling and Installing @command{gawk} on OpenVMS
-
-@c based on material from Pat Rankin <rankin@eql.caltech.edu>
-@c now rankin@pactechdata.com
-@c now r.pat.rankin@gmail.com
-
-@cindex @command{gawk} @subentry OpenVMS version of
-@cindex installing @command{gawk} @subentry OpenVMS
-This @value{SUBSECTION} describes how to compile and install @command{gawk}
under OpenVMS.
-
-@menu
-* OpenVMS Compilation:: How to compile @command{gawk} under OpenVMS.
-* OpenVMS Dynamic Extensions:: Compiling @command{gawk} dynamic extensions
- on OpenVMS.
-* OpenVMS Installation Details:: How to install @command{gawk} under OpenVMS.
-* OpenVMS Running:: How to run @command{gawk} under OpenVMS.
-* OpenVMS GNV:: The OpenVMS GNV Project.
-@end menu
-
-@node OpenVMS Compilation
-@appendixsubsubsec Compiling @command{gawk} on OpenVMS
-@cindex compiling @command{gawk} @subentry for OpenVMS
-
-To compile @command{gawk} under OpenVMS, there is a @code{DCL} command
procedure
-that issues all the necessary @code{CC} and @code{LINK} commands. There is
-also a @file{Makefile} for use with the @code{MMS} and @code{MMK} utilities.
-From the source directory, use either:
-
-@example
-$ @kbd{@@[.vms]vmsbuild.com}
-@end example
-
-@noindent
-or:
-
-@example
-$ @kbd{MMS/DESCRIPTION=[.vms]descrip.mms gawk}
-@end example
-
-@noindent
-or:
-
-@example
-$ @kbd{MMK/DESCRIPTION=[.vms]descrip.mms gawk}
-@end example
-
-Note that the @command{vmsbuild.com} method of building is no longer being
-maintained and is planned to be removed in the future.
-
-@command{MMK} is an open source, free, near-clone of @command{MMS} and
-can better handle ODS-5 volumes with upper- and lowercase @value{FN}s.
-@command{MMK} is available from @uref{https://github.com/endlesssoftware/mmk}.
-
-With ODS-5 volumes and extended parsing enabled, the case of the target
-parameter may need to be exact.
-
-@command{gawk} has been tested using these VMS Software, Inc.@:
-Community editions:
-
-@itemize @bullet
-@item
-HP C V7.3-010 on OpenVMS Alpha V8.4-2L1.
-
-@item
-HP C V7.3-020 on OpenVMS IA64 V8.4-2L3.@footnote{The IA64 architecture
-is also known as ``Itanium.''}
-@end itemize
-
-Due to HPE cancelling the Hobbyist licensing program, no more testing is
-being done on older releases of OpenVMS.
-
-@xref{OpenVMS GNV} for information on building
-@command{gawk} as a PCSI kit that is compatible with the GNV product.
-
-@node OpenVMS Dynamic Extensions
-@appendixsubsubsec Compiling @command{gawk} Dynamic Extensions on OpenVMS
-
-The extensions that have been ported to OpenVMS can be built using one of
-the following commands:
-
-@example
-$ @kbd{MMS/DESCRIPTION=[.vms]descrip.mms extensions}
-@end example
-
-@noindent
-or:
-
-@example
-$ @kbd{MMK/DESCRIPTION=[.vms]descrip.mms extensions}
-@end example
-
-@command{gawk} uses @code{AWKLIBPATH} as either an environment variable
-or a logical name to find the dynamic extensions.
-
-Dynamic extensions need to be compiled with the same compiler options for
-floating-point, pointer size, and symbol name handling as were used
-to compile @command{gawk} itself.
-Alpha and Itanium should use IEEE floating point. The pointer size is 32 bits,
-and the symbol name handling should be exact case with CRC shortening for
-symbols longer than 32 bits.
-
-@example
-/name=(as_is,short)
-/float=ieee/ieee_mode=denorm_results
-@end example
-
-Compile-time macros need to be defined before the first OpenVMS-supplied
-header file is included, as follows:
-
-@example
-#if (__CRTL_VER >= 70200000)
-#define _LARGEFILE 1
-#endif
-
-#ifdef __CRTL_VER
-#if __CRTL_VER >= 80200000
-#define _USE_STD_STAT 1
-#endif
-#endif
-@end example
-
-If you are writing your own extensions to run on OpenVMS, you must supply these
-definitions yourself. The @file{config.h} file created when building
@command{gawk}
-on OpenVMS does this for you; if instead you use that file or a similar one,
then you
-must remember to include it before any OpenVMS-supplied header files.
-
-@node OpenVMS Installation Details
-@appendixsubsubsec Installing @command{gawk} on OpenVMS
-
-To use @command{gawk}, all you need is a ``foreign'' command, which is a
-@code{DCL} symbol whose value begins with a dollar sign. For example:
-
-@example
-$ @kbd{GAWK :== $disk1:[gnubin]gawk}
-@end example
-
-@noindent
-Substitute the actual location of @command{gawk.exe} for
-@samp{$disk1:[gnubin]}. The symbol should be placed in the
-@file{login.com} of any user who wants to run @command{gawk},
-so that it is defined every time the user logs on.
-Alternatively, the symbol may be placed in the system-wide
-@file{sylogin.com} procedure, which allows all users
-to run @command{gawk}.
-
-If your @command{gawk} was installed by a PCSI kit into the
-@file{GNV$GNU:} directory tree, the program will be known as
-@file{GNV$GNU:[bin]gnv$gawk.exe} and the help file will be
-@file{GNV$GNU:[vms_help]gawk.hlp}.
-
-The PCSI kit also installs a @file{GNV$GNU:[vms_bin]gawk_verb.cld} file
-that can be used to add @command{gawk} and @command{awk} as DCL commands.
-
-For just the current process you can use:
-
-@example
-$ @kbd{set command gnv$gnu:[vms_bin]gawk_verb.cld}
-@end example
-
-Or the system manager can use @file{GNV$GNU:[vms_bin]gawk_verb.cld} to
-add the @command{gawk} and @command{awk} commands to the system-wide
@samp{DCLTABLES}.
-
-The DCL syntax is documented in the @file{gawk.hlp} file.
-
-Optionally, the @file{gawk.hlp} entry can be loaded into an OpenVMS help
library:
-
-@example
-$ @kbd{LIBRARY/HELP sys$help:helplib [.vms]gawk.hlp}
-@end example
-
-@noindent
-(You may want to substitute a site-specific help library rather than
-the standard OpenVMS library @samp{HELPLIB}.) After loading the help text,
-the command:
-
-@example
-$ @kbd{HELP GAWK}
-@end example
-
-@noindent
-provides information about both the @command{gawk} implementation and the
-@command{awk} programming language.
-
-The logical name @samp{AWK_LIBRARY} can designate a default location
-for @command{awk} program files. For the @option{-f} option, if the specified
-@value{FN} has no device or directory path information in it, @command{gawk}
-looks in the current directory first, then in the directory specified
-by the translation of @samp{AWK_LIBRARY} if the file is not found.
-If, after searching in both directories, the file still is not found,
-@command{gawk} appends the suffix @samp{.awk} to the @value{FN} and retries
-the file search. If @samp{AWK_LIBRARY} has no definition, a default value
-of @samp{SYS$LIBRARY:} is used for it.
-
-@node OpenVMS Running
-@appendixsubsubsec Running @command{gawk} on OpenVMS
-
-Command-line parsing and quoting conventions are significantly different
-on OpenVMS, so examples in this @value{DOCUMENT} or from other sources often
need minor
-changes. They @emph{are} minor though, and all @command{awk} programs
-should run correctly.
-
-Here are a couple of trivial tests:
-
-@example
-$ @kbd{gawk -- "BEGIN @{print ""Hello, World!""@}"}
-$ @kbd{gawk -"W" version}
-! could also be -"W version" or "-W version"
-@end example
-
-@noindent
-Note that uppercase and mixed-case text must be quoted.
-
-The OpenVMS port of @command{gawk} includes a @code{DCL}-style interface in
addition
-to the original shell-style interface (see the help entry for details).
-One side effect of dual command-line parsing is that if there is only a
-single parameter (as in the quoted program string), the command
-becomes ambiguous. To work around this, the normally optional @option{--}
-flag is required to force Unix-style parsing rather than @code{DCL} parsing.
-If any other dash-type options (or multiple parameters such as @value{DF}s to
-process) are present, there is no ambiguity and @option{--} can be omitted.
-
-@cindex exit status, of @command{gawk} @subentry on OpenVMS
-The @code{exit} value is a Unix-style value and is encoded into an OpenVMS exit
-status value when the program exits.
-
-The OpenVMS severity bits will be set based on the @code{exit} value.
-A failure is indicated by 1, and OpenVMS sets the @code{ERROR} status.
-A fatal error is indicated by 2, and OpenVMS sets the @code{FATAL} status.
-All other values will have the @code{SUCCESS} status. The exit value is
-encoded to comply with OpenVMS coding standards and will have the
-@code{C_FACILITY_NO} of @code{0x350000} with the constant @code{0xA000}
-added to the number shifted over by 3 bits to make room for the severity codes.
-
-To extract the actual @command{gawk} exit code from the OpenVMS status, use:
-
-@example
-unix_status = (vms_status .and. %x7f8) / 8
-@end example
-
-@noindent
-A C program that uses @code{exec()} to call @command{gawk} will get the
original
-Unix-style exit value.
-
-OpenVMS reports time values in GMT unless one of the @code{SYS$TIMEZONE_RULE}
-or @code{TZ} logical names is set.
-
-@cindex search paths
-@cindex search paths @subentry for source files
-@cindex @env{AWKPATH} environment variable
-@cindex environment variables @subentry @env{AWKPATH}
-The default search path, when looking for @command{awk} program files specified
-by the @option{-f} option, is @code{"SYS$DISK:[],AWK_LIBRARY:"}. The logical
-name @env{AWKPATH} can be used to override this default. The format
-of @env{AWKPATH} is a comma-separated list of directory specifications.
-When defining it, the value should be quoted so that it retains a single
-translation and not a multitranslation @code{RMS} searchlist.
-
-@cindex redirection @subentry on OpenVMS
-This restriction also applies to running @command{gawk} under GNV,
-as redirection is always to a DCL command.
-
-If you are redirecting data to an OpenVMS command or utility, the current
-implementation requires setting up an OpenVMS foreign command that runs
-a command file before invoking @command{gawk}.
-(This restriction may be removed in a future release of @command{gawk} on
OpenVMS.)
-
-Without this command file, the input data will also appear prepended
-to the output data.
-
-This also allows simulating POSIX commands that are not found on OpenVMS or the
-use of GNV utilities.
-
-The example below is for @command{gawk} redirecting data to the OpenVMS
-@command{sort} command.
-
-@example
-$ sort = "@@device:[dir]vms_gawk_sort.com"
-@end example
-
-The command file needs to be of the format in the example below.
-
-The first line inhibits the passed input data from also showing up in the
-output. It must be in the format in the example.
-
-The next line creates a foreign command that overrides the outer foreign
-command which prevents an infinite recursion of command files.
-
-The next to the last command redirects @code{sys$input} to be
-@code{sys$command}, in order to pick up the data that is being redirected
-to the command.
-
-The last line runs the actual command. It must be the last command as the data
-redirected from @command{gawk} will be read when the command file ends.
-
-@example
-$!'f$verify(0,0)'
-$ sort := sort
-$ define/user sys$input sys$command:
-$ sort sys$input: sys$output:
-@end example
-
-@node OpenVMS GNV
-@appendixsubsubsec The OpenVMS GNV Project
-
-The OpenVMS GNV package provides a build environment similar to POSIX with
ports
-of a collection of open source tools. The @command{gawk} found in the GNV
-base kit is an older port. Currently, the GNV project is being reorganized
-to supply individual PCSI packages for each component.
-See @w{@uref{https://sourceforge.net/p/gnv/wiki/InstallingGNVPackages/}.}
-
-The normal build procedure for @command{gawk} produces a program that
-is suitable for use with GNV.
-
-The file @file{vms/gawk_build_steps.txt} in the distribution documents
-the procedure for building an OpenVMS PCSI kit that is compatible with GNV.
-
-@node Bugs
-@appendixsec Reporting Problems and Bugs
-@cindex archaeologists
-@quotation
-@i{There is nothing more dangerous than a bored archaeologist.}
-@author Douglas Adams, @cite{The Hitchhiker's Guide to the Galaxy}
-@end quotation
-@c the radio show, not the book. :-)
-
-@cindex debugging @command{gawk}, bug reports
-@cindex troubleshooting @subentry @command{gawk} @subentry bug reports
-If you have problems with @command{gawk} or think that you have found a bug,
-report it to the developers; we cannot promise to do anything,
-but we might well want to fix it.
-
-@menu
-* Bug definition:: Defining what is and is not a bug.
-* Bug address:: Where to send reports to.
-* Usenet:: Where not to send reports to.
-* Performance bugs:: What to do if you think there is a performance
- issue.
-* Asking for help:: Dealing with non-bug questions.
-* Maintainers:: Maintainers of non-*nix ports.
-@end menu
-
-@node Bug definition
-@appendixsubsec Defining What Is and What Is Not A Bug
-
-Before talking about reporting bugs, let's define what is a bug,
-and what is not.
-
-A bug is:
-
-@itemize @bullet
-@item
-When @command{gawk} behaves differently from what's described
-in the POSIX standard, and that difference is not mentioned
-in this @value{DOCUMENT} as being done on purpose.
-
-@item
-When @command{gawk} behaves differently from what's described
-in this @value{DOCUMENT}.
-
-@item
-When @command{gawk} behaves differently from other @command{awk}
-implementations in particular circumstances, and that behavior cannot
-be attributed to an additional feature in @command{gawk}.
-
-@item
-Something that is obviously wrong, such as a core dump.
-
-@item
-When this @value{DOCUMENT} is unclear or ambiguous about a particular
-feature's behavior.
-@end itemize
-
-The following things are @emph{not} bugs, and should not be reported
-to the bug mailing list. You can ask about them on the ``help'' mailing
-list (@pxref{Asking for help}), but don't be surprised if you get an
-answer of the form ``that's how @command{gawk} behaves and it isn't
-going to change.'' Here's the list:
-
-@itemize @bullet
-@item
-Missing features, for any definition of @dfn{feature}. For example,
-additional built-in arithmetic functions, or additional ways to split
-fields or records, or anything else.
-
-The number of features that @command{gawk} does @emph{not} have is
-by definition infinite. It cannot be all things to all people.
-In short, just because @command{gawk} doesn't do what @emph{you}
-think it should, it's not necessarily a bug.
-
-@item
-Behaviors that are defined by the POSIX standard and/or for historical
-compatibility with Unix @command{awk}. Even if you happen to dislike
-those behaviors, they're not going to change: changing them would
-break millions of existing @command{awk} programs.
-
-@item
-Behaviors that differ from how it's done in other languages. @command{awk}
-and @command{gawk} stand on their own and do not have to follow the crowd.
-This is particularly true when the requested behavior change would break
-backwards compatibility.
-
-This applies also to differences in behavior between @command{gawk}
-and other language compilers and interpreters, such as wishes for more
-detailed descriptions of what the problem is when a syntax error is
-encountered.
-
-@item
-Documentation issues of the form ``the manual doesn't tell me how to
-do XYZ.'' The manual is not a cookbook to solve every little problem
-you may have. Its purpose is to teach you how to solve your problems
-on your own.
-
-@item
-General questions and discussion about @command{awk} programming or
-why @command{gawk} behaves the way it does. For that use the ``help''
-mailing list: see @ref{Asking for help}.
-@end itemize
-
-For more information, see @uref{http://www.skeeve.com/fork-my-code.html,
-@cite{Fork My Code, Please!---An Open Letter To Those of You Who Are Unhappy}},
-by Arnold Robbins and Chet Ramey.
-
-@sidebar A Note About Fuzzers
-In recent years, people have been running ``fuzzers'' to generate
-invalid @command{awk} programs in order to find and report (so-called)
-bugs in @command{gawk}.
-
-In general, such reports are not of much practical use. The programs
-they create are not realistic and the bugs found are generally from
-some kind of memory corruption that is fatal anyway.
-
-So, if you want to run a fuzzer against @command{gawk} and report the
-results, you may do so, but be aware that such reports don't carry the
-same weight as reports of real bugs do.
-@end sidebar
-
-@node Bug address
-@appendixsubsec Submitting Bug Reports
-
-Before reporting a bug, make sure you have really found a genuine bug.
-
-Here are the steps for submitting a bug report. Following them will
-make both your life and the lives of the maintainers much easier.
-
-@enumerate 1
-@item
-Make sure that what you want to report is appropriate.
-@xref{Bug definition}. If it's not, you are wasting your
-time and ours.
-
-@item
-Verify that you have the latest version of @command{gawk}.
-Many bugs (usually subtle ones) are fixed at each release, and if yours
-is out-of-date, the problem may already have been solved.
-
-@cindex @env{LC_ALL} environment variable
-@cindex environment variables @subentry @env{LC_ALL}
-@item
-Please see if setting the environment variable @env{LC_ALL}
-to @code{LC_ALL=C} causes things to behave as you expect. If so, it's
-a locale issue, and may or may not really be a bug.
-
-@item
-Carefully reread the documentation and see if it says you can do
-what you're trying to do. If it's not clear whether you should be able
-to do something or not, report that too; it's a bug in the documentation!
-
-@item
-Before reporting a bug or trying to fix it yourself, try to isolate it
-to the smallest possible @command{awk} program and input @value{DF} that
-reproduce the problem.
-
-@item
-@cindex @command{gawkbug} utility
-Use the @command{gawkbug} program to submit the bug report. This
-program sets up a bug report template and opens it in your editor.
-You then need to edit it appropriately to include:
-
-@c nested list
-@itemize @bullet
-@item
-The program and @value{DF}.
-
-@item
-The exact results
-@command{gawk} gave you. Also say what you expected to occur; this helps
-us decide whether the problem is really in the documentation.
-
-@item
-A fix if you have one.
-@end itemize
-
-@item
-Do @emph{not} send screenshots. Instead, use copy/paste to send text, or
-send files.
-
-@c @item
-@c Do send files as attachments, instead of inline. This avoids corruption
-@c by mailer programs out in the wilds of the Internet.
-
-@item
-Please be sure to send all mail in @emph{plain text},
-not (or not exclusively) in HTML.
-
-@item
-@emph{All email must be in English. This is the only language
-understood in common by all the maintainers.}
-@end enumerate
-
-@cindex @email{bug-gawk@@gnu.org} bug reporting address
-@cindex email address for bug reports, @email{bug-gawk@@gnu.org}
-@cindex bug reports, email address, @email{bug-gawk@@gnu.org}
-The @command{gawkbug} program sends email to
-@EMAIL{bug-gawk@@gnu.org,bug dash gawk at gnu dot org}.
-
-The @command{gawk} maintainers subscribe to this address, and
-thus they will receive your bug report.
-Do @emph{not} send mail to the maintainers directly;
-the bug reporting address is preferred because the
-email list is archived at the GNU Project.
-
-If you are using OpenVMS or the MinGW build of @command{gawk},
-the @command{gawkbug} script won't be available. Please send
-the previously listed information directly in an email to
-the bug list. Please send any test program or data files
-as attachments, instead of inline in the email, to avoid
-their being mangled by various mail systems.
-
-@quotation NOTE
-Many distributions of GNU/Linux and the various BSD-based operating systems
-have their own bug reporting systems. If you report a bug using your
distribution's
-bug reporting system, you should also send a copy to
-@EMAIL{bug-gawk@@gnu.org,bug dash gawk at gnu dot org}.
-
-This is for two reasons. First, although some distributions forward
-bug reports ``upstream'' to the GNU mailing list, many don't, so there is a
good
-chance that the @command{gawk} maintainers won't even see the bug report!
Second,
-mail to the GNU list is archived, and having everything at the GNU Project
-keeps things self-contained and not dependent on other organizations.
-@end quotation
-
-Please note: We ask that you follow the
-@uref{https://gnu.org/philosophy/kind-communication.html,
-GNU Kind Communication Guidelines} in your correspondence on the
-list (as well as off of it).
-
-@node Usenet
-@appendixsubsec Please Don't Post Bug Reports to USENET
-
-@quotation
-@c Date: Sun, 17 May 2015 19:50:14 -0400
-@c From: Chet Ramey <chet.ramey@case.edu>
-@c Reply-To: chet.ramey@case.edu
-@c Organization: ITS, Case Western Reserve University
-@c To: Aharon Robbins <arnold@skeeve.com>
-@c CC: chet.ramey@case.edu
-I gave up on Usenet a couple of years ago and haven't really looked back.
-It's like sports talk radio---you feel smarter for not having read it.
-@author Chet Ramey
-@end quotation
-
-@cindex @code{comp.lang.awk} newsgroup
-Please do @emph{not} try to report bugs in @command{gawk} by posting to the
-Usenet/Internet newsgroup @code{comp.lang.awk}. Although some of the
-@command{gawk} developers occasionally read this news group, the primary
-@command{gawk} maintainer no longer does. Thus it's virtually guaranteed
-that he will @emph{not} see your posting.
-
-If you really don't care about the previous paragraph and continue to
-post bug reports in @code{comp.lang.awk}, then understand that you're
-not reporting bugs, you're just whining.
-
-Similarly, posting bug reports or questions in web forums (such
-as @uref{https://stackoverflow.com/, Stack Overflow}) may get you
-an answer, but it won't be from the @command{gawk} maintainers,
-who do not spend their time in web forums. The steps described here are
-the only officially recognized way for reporting bugs. Really.
-
-@ignore
-And another one:
-
-Date: Thu, 11 Jun 2015 09:00:56 -0400
-From: Chet Ramey <chet.ramey@case.edu>
-
-My memory was imperfect. Back in June 2009, I wrote:
-
-"That's the nice thing about open source, right? You can take your ball
-and run to another section of the playground. Then, if you like mixing
-metaphors, you can throw rocks from there."
-@end ignore
-
-@node Performance bugs
-@appendixsubsec What To Do If You Think There Is A Performance Issue
-
-@cindex performance, checking issues
-@cindex profiling, compiling @command{gawk} for
-If you think that @command{gawk} is too slow at doing a particular task,
-you should investigate before sending in a bug report. Here are the steps
-to follow:
-
-@enumerate 1
-@item
-Run @command{gawk} with the @option{--profile} option (@pxref{Options})
-to see what your
-program is doing. It may be that you have written it in an inefficient manner.
-For example, you may be doing something for every record that could be done
-just once, for every file.
-(Use a @code{BEGINFILE} rule; @pxref{BEGINFILE/ENDFILE}.)
-Or you may be doing something for every file that only needs to be done
-once per run of the program.
-(Use a @code{BEGIN} rule; @pxref{BEGIN/END}.)
-
-@item
-If profiling at the @command{awk} level doesn't help, then you will
-need to compile @command{gawk} itself for profiling at the C language level.
-
-To do that, start with the latest released version of
-@command{gawk}. Unpack the source code in a new directory, and configure
-it:
-
-@example
-$ @kbd{tar -xpzvf gawk-X.Y.Z.tar.gz}
-@print{} @dots{} @ii{Output omitted}
-$ @kbd{cd gawk-X.Y.Z}
-$ @kbd{./configure}
-@print{} @dots{} @ii{Output omitted}
-@end example
-
-@item
-Edit the files @file{Makefile} and @file{support/Makefile}.
-Change every instance of @option{-O2} or @option{-O} to @option{-pg}.
-This causes @command{gawk} to be compiled for profiling.
-
-@item
-Compile the program by running the @command{make} command:
-
-@example
-@group
-$ @kbd{make}
-@print{} @dots{} @ii{Output omitted}
-@end group
-@end example
-
-@item
-Run the freshly compiled @command{gawk} on a @emph{real} program,
-using @emph{real} data. Using an artificial program to try to time one
-particular feature of @command{gawk} is useless; real @command{awk} programs
-generally spend most of their time doing I/O, not computing. If you want to
prove
-that something is slow, it @emph{must} be done using a real program and real
data.
-
-Use a data file that is large enough for the statistical profiling to measure
-where @command{gawk} spends its time. It should be at least 100 megabytes in
size.
-
-@example
-$ @kbd{./gawk -f realprogram.awk realdata > /dev/null}
-@end example
-
-@item
-When done, you should have a file in the current directory named
@file{gmon.out}.
-Run the command @samp{gprof gawk gmon.out > gprof.out}.
-
-@item
-Submit a bug report explaining what you think is slow. Include the
@file{gprof.out}
-file with it.
-
-Preferably, you should also submit the program and the data, or else indicate
where to
-get the data if the file is large.
-
-@item
-If you have not submitted your program and data, be prepared to apply patches
and
-rerun the profiling in order to see if the patches were effective.
-
-@end enumerate
-
-If you are incapable or unwilling to do the steps listed above, then you will
-just have to live with @command{gawk} as it is.
-
-@node Asking for help
-@appendixsubsec Where To Send Non-bug Questions
-
-If you have questions related to @command{awk} programming, or why
@command{gawk}
-behaves a certain way, or any other @command{awk}- or @command{gawk}-related
issue,
-please @emph{do not} send it to the bug reporting address.
-
-As of July, 2021, there is a separate mailing list for this purpose:
-@EMAIL{help-gawk@@gnu.org, help dash gawk at gnu dot org}.
-Anything that is not a bug report should be sent to that list.
-
-@quotation NOTE
-If you disregard these directions and send non-bug mails to the bug list,
-you will be told to use the help list.
-After two such requests you will be silently @emph{blacklisted} from the bug
list.
-@end quotation
-
-Please note: As with the bug list, we ask that you follow the
-@uref{https://gnu.org/philosophy/kind-communication.html,
-GNU Kind Communication Guidelines} in your correspondence on the help
-list (as well as off of it).
-
-@cindex Proulx, Bob
-If you wish to the subscribe to the list, in order to help out
-others, or to learn from others, here are instructions, courtesy
-of Bob Proulx:
-
-@table @emph
-@item Subscribe by email
-
-Send an email message to
-@EMAIL{help-gawk-request@@gnu.org, help dash gawk dash request at gnu dot org}
-with ``subscribe'' in
-the body of the message. The subject does not matter and is not used.
-
-@item Subscribe by web form
-
-To use the web interface visit
-@uref{https://lists.gnu.org/mailman/listinfo/help-gawk,
-the list information page}.
-Use the
-subscribe form to fill out your email address and submit using the
-@code{Subscribe} button.
-
-@item Reply to the confirmation message
-
-In both cases then reply to the confirmation message that is sent to
-your address in reply.
-@end table
-
-Bob mentions that you may also use email for subscribing and
-unsubscribing. For example:
-
-@example
-$ @kbd{echo help | mailx -s request help-gawk-request@@gnu.org}
-$ @kbd{echo subscribe | mailx -s request help-gawk-request@@gnu.org}
-$ @kbd{echo unsubscribe | mailx -s request help-gawk-request@@gnu.org}
-@end example
-
-@node Maintainers
-@appendixsubsec Reporting Problems with Non-Unix Ports
-
-If you find bugs in one of the non-Unix ports of @command{gawk},
-send an email to the bug list, with a copy to the
-person who maintains that port. The maintainers are named in the following
list,
-as well as in the @file{README} file in the @command{gawk} distribution.
-Information in the @file{README} file should be considered authoritative
-if it conflicts with this @value{DOCUMENT}.
-
-The people maintaining the various @command{gawk} ports are:
-
-@c put the index entries outside the table, for docbook
-@cindex Buening, Andreas
-@cindex Malmberg, John
-@cindex G., Daniel Richard
-@cindex Robbins @subentry Arnold
-@cindex Zaretskii, Eli
-@multitable {MS-Windows with MinGW}
{123456789012345678901234567890123456789001234567890}
-@item Unix and POSIX systems @tab Arnold Robbins,
@EMAIL{arnold@@skeeve.com,arnold at skeeve dot com}
-
-@item MS-Windows with MinGW @tab Eli Zaretskii, @EMAIL{eliz@@gnu.org,eliz at
gnu dot org}
-
-@item OpenVMS @tab John Malmberg, @EMAIL{wb8tyw@@qsl.net,wb8tyw at qsl dot net}
-
-@item z/OS (OS/390) @tab Daniel Richard G.@: @EMAIL{skunk@@iSKUNK.ORG,skunk at
iSKUNK dot ORG}
-@end multitable
-
-If your bug is also reproducible under Unix, send a copy of your
-report to the @EMAIL{bug-gawk@@gnu.org,bug dash gawk at gnu dot org} email
list as well.
-
-@node Other Versions
-@appendixsec Other Freely Available @command{awk} Implementations
-@cindex @command{awk} @subentry implementations
-@ignore
-From: emory!amc.com!brennan (Michael Brennan)
-Subject: C++ comments in awk programs
-To: arnold@gnu.ai.mit.edu (Arnold Robbins)
-Date: Wed, 4 Sep 1996 08:11:48 -0700 (PDT)
-
-@end ignore
-@cindex Brennan, Michael
-@ifnotdocbook
-@quotation
-@i{It's kind of fun to put comments like this in your awk code:}@*
-@ @ @ @ @ @ @code{// Do C++ comments work? answer: yes! of course}
-@author Michael Brennan
-@end quotation
-@end ifnotdocbook
-
-@docbook
-<blockquote><attribution>Michael Brennan</attribution>
-<literallayout><emphasis>It's kind of fun to put comments like this in your
awk code.</emphasis>
- <literal>// Do C++ comments work? answer:
yes! of course</literal></literallayout>
-</blockquote>
-@end docbook
-
-There are a number of other freely available @command{awk} implementations.
-This @value{SECTION} briefly describes where to get them:
-
-@table @asis
-@cindex Kernighan, Brian
-@cindex source code @subentry Brian Kernighan's @command{awk}
-@cindex @command{awk} @subentry versions of @seealso{Brian Kernighan's
@command{awk}}
-@cindex Brian Kernighan's @command{awk} @subentry source code
-@item Unix @command{awk}
-Brian Kernighan, one of the original designers of Unix @command{awk},
-has made his implementation of
-@command{awk} freely available.
-You can retrieve it from GitHub:
-
-@cindex @command{git} utility
-@example
-git clone https://github.com/onetrueawk/awk bwkawk
-@end example
-
-@noindent
-This command creates a copy of the @uref{https://git-scm.com, Git}
-repository in a directory named @file{bwkawk}. If you omit the last argument
-from the @command{git} command line, the repository copy is created in a
-directory named @file{awk}.
-
-This version requires an ISO C (1990 standard) compiler; the C compiler
-from GCC (the GNU Compiler Collection) works quite nicely.
-
-To build it, review the settings in the @file{makefile}, and then just run
-@command{make}. Note that the result of compilation is named
-@command{a.out}; you will have to rename it to something reasonable.
-
-@xref{Common Extensions}
-for a list of extensions in this @command{awk} that are not in POSIX
@command{awk}.
-
-As a side note, Dan Bornstein has created a Git repository tracking
-all the versions of BWK @command{awk} that he could find. It's
-available at @uref{https://github.com/danfuzz/one-true-awk}.
-
-@cindex Brennan, Michael
-@cindex @command{mawk} utility
-@cindex source code @subentry @command{mawk}
-@item @command{mawk}
-Michael Brennan wrote an independent implementation of @command{awk},
-called @command{mawk}. It is available under the
-@ifclear FOR_PRINT
-GPL (@pxref{Copying}),
-@end ifclear
-@ifset FOR_PRINT
-GPL,
-@end ifset
-just as @command{gawk} is.
-
-The original distribution site for the @command{mawk} source code
-no longer has it. A copy is available at
-@uref{http://www.skeeve.com/gawk/mawk1.3.3.tar.gz}.
-
-In 2009, Thomas Dickey took on @command{mawk} maintenance.
-Basic information is available on
-@uref{http://www.invisible-island.net/mawk, the project's web page}.
-The download URL is
-@url{http://invisible-island.net/datafiles/release/mawk.tar.gz}.
-
-Once you have it,
-@command{gunzip} may be used to decompress this file. Installation
-is similar to @command{gawk}'s
-(@pxref{Unix Installation}).
-
-@xref{Common Extensions}
-for a list of extensions in @command{mawk} that are not in POSIX @command{awk}.
-
-@item @command{mawk} 2.0
-In 2016, Michael Brennan resumed @command{mawk} development.
-His development snapshots are available via Git from the project's
-@uref{https://github.com/mikebrennan000/mawk-2, GitHub page}.
-
-@cindex Sumner, Andrew
-@cindex @command{awka} compiler for @command{awk}
-@cindex source code @subentry @command{awka}
-@item @command{awka}
-Written by Andrew Sumner,
-@command{awka} translates @command{awk} programs into C, compiles them,
-and links them with a library of functions that provide the core
-@command{awk} functionality.
-It also has a number of extensions.
-
-Both the @command{awk} translator and the library are released under the GPL.
-
-To get @command{awka}, go to @url{https://sourceforge.net/projects/awka}.
-@c You can reach Andrew Sumner at @email{andrew@@zbcom.net}.
-@c andrewsumner@@yahoo.net
-
-The project seems to be frozen; no new code changes have been made
-since approximately 2001.
-
-@item Revive Awka
-This project, available at @uref{https://github.com/noyesno/awka},
-intends to fix bugs in @command{awka} and add more features.
-
-@cindex Beebe, Nelson H.F.@:
-@cindex @command{pawk} (profiling version of Brian Kernighan's @command{awk})
-@cindex source code @subentry @command{pawk} (profiling version of Brian
Kernighan's @command{awk})
-@item @command{pawk}
-Nelson H.F.@: Beebe at the University of Utah has modified
-BWK @command{awk} to provide timing and profiling information.
-It is different from @command{gawk} with the @option{--profile} option
-(@pxref{Profiling})
-in that it uses CPU-based profiling, not line-count
-profiling. You may find it at either
-@uref{ftp://ftp.math.utah.edu/pub/pawk/pawk-20030606.tar.gz}
-or
-@uref{http://www.math.utah.edu/pub/pawk/pawk-20030606.tar.gz}.
-
-@item BusyBox @command{awk}
-@cindex BusyBox Awk
-@cindex source code @subentry BusyBox Awk
-BusyBox is a GPL-licensed program providing small versions of many
-applications within a single executable. It is aimed at embedded systems.
-It includes a full implementation of POSIX @command{awk}. When building
-it, be careful not to do @samp{make install} as it will overwrite
-copies of other applications in your @file{/usr/local/bin}. For more
-information, see the @uref{https://busybox.net, project's home page}.
-
-@cindex OpenSolaris
-@cindex Solaris, POSIX-compliant @command{awk}
-@cindex source code @subentry Solaris @command{awk}
-@item The OpenSolaris POSIX @command{awk}
-The versions of @command{awk} in @file{/usr/xpg4/bin} and
-@file{/usr/xpg6/bin} on Solaris are more or less POSIX-compliant.
-They are based on the @command{awk} from Mortice Kern Systems for PCs.
-We were able to make this code compile and work under GNU/Linux
-with 1--2 hours of work. Making it more generally portable (using
-GNU Autoconf and/or Automake) would take more work, and this
-has not been done, at least to our knowledge.
-
-@cindex Illumos, POSIX-compliant @command{awk}
-@cindex source code @subentry Illumos @command{awk}
-The source code used to be available from the OpenSolaris website.
-However, that project was ended and the website shut down. Fortunately, the
-@uref{https://wiki.illumos.org/display/illumos/illumos+Home, Illumos project}
-makes this implementation available. You can view the files one at a time from
-@uref{https://github.com/joyent/illumos-joyent/blob/master/usr/src/cmd/awk_xpg4}.
-
-@cindex @command{frawk}
-@cindex source code @subentry @command{frawk}
-@item @command{frawk}
-This is a language for writing short programs. ``To a first
-approximation, it is an implementation of the AWK language;
-many common @command{awk} programs produce equivalent output
-when passed to @command{frawk}.'' However, it has a number of
-important additional features. The code is available at
-@uref{https://github.com/ezrosent/frawk}.
-
-@cindex @command{goawk}
-@cindex Go implementation of @command{awk}
-@cindex source code @subentry @command{goawk}
-@cindex programming languages @subentry Go
-@item @command{goawk}
-This is an @command{awk} interpreter written in the
-@uref{https://golang.org/, Go programming language}.
-It implements POSIX @command{awk}, with a few minor extensions.
-Source code is available from @uref{https://github.com/benhoyt/goawk}.
-The author wrote a nice
-@uref{https://benhoyt.com/writings/goawk/, article}
-describing the implementation.
-
-@cindex @command{AWKgo}
-@cindex @command{awk} to Go translator
-@cindex source code @subentry @command{AWKgo}
-@cindex programming languages @subentry Go
-@item @command{AWKgo}
-This is an @command{awk} to Go translator.
-It was written by the author of @command{goawk}.
-(See the previous entry in this list.) Source code is
-available from
-@uref{https://github.com/benhoyt/goawk/tree/master/awkgo}.
-The author's article about it is at
-@uref{https://benhoyt.com/writings/awkgo/}.
-
-@cindex @command{jawk}
-@cindex Java implementation of @command{awk}
-@cindex source code @subentry @command{jawk}
-@item @command{jawk}
-This is an interpreter for @command{awk} written in Java. It claims
-to be a full interpreter, although because it uses Java facilities
-for I/O and for regexp matching, the language it supports is different
-from POSIX @command{awk}. More information is available on the
-@uref{http://jawk.sourceforge.net, project's home page}.
-
-@item Hoijui's @command{jawk}
-This project, available at @uref{https://github.com/hoijui/Jawk},
-is another @command{awk} interpreter written in Java. It uses
-modern Java build tools.
-
-@item Libmawk
-@cindex libmawk
-@cindex source code @subentry libmawk
-This is an embeddable @command{awk} interpreter derived from
-@command{mawk}. For more information, see
-@uref{http://repo.hu/projects/libmawk/}.
-
-@cindex source code @subentry embeddable @command{awk} interpreter
-@cindex Neacsu, Mircea
-@item Mircea Neacsu's Embeddable @command{awk}
-Mircea Neacsu has created an embeddable @command{awk}
-interpreter, based on BWK awk. It's available
-at @uref{https://github.com/neacsum/awk}.
-
-@item @code{pawk}
-@cindex source code @subentry @command{pawk} (Python version)
-@cindex @code{pawk}, @command{awk}-like facilities for Python
-This is a Python module that claims to bring @command{awk}-like
-features to Python. See @uref{https://github.com/alecthomas/pawk}
-for more information. (This is not related to Nelson Beebe's
-modified version of BWK @command{awk}, described earlier.)
-
-@item @command{awkcc}
-@cindex source code @subentry @command{awkcc}
-@cindex @command{awkcc}, @command{awk} to C translator
-@cindex Ramming, J.@: Christopher
-This is an early adaptation of Unix @command{awk} that
-translates @command{awk} into C code. It was done by
-J.@: Christopher Ramming at Bell Labs, circa 1988.
-It's available at @uref{https://github.com/nokia/awkcc}.
-Bringing this up to date would be an interesting
-software engineering exercise.
-
-@item @w{QSE @command{awk}}
-@cindex QSE @command{awk}
-@cindex source code @subentry QSE @command{awk}
-This is an embeddable @command{awk} interpreter. For more information,
-see @uref{https://code.google.com/p/qse/}. @c and
@uref{http://awk.info/?tools/qse}.
-
-@item @command{QTawk}
-@cindex QuikTrim Awk
-@cindex source code @subentry QuikTrim Awk
-This is an independent implementation of @command{awk} distributed
-under the GPL. It has a large number of extensions over standard
-@command{awk} and may not be 100% syntactically compatible with it.
-See @uref{http://www.quiktrim.org/QTawk.html} for more information,
-including the manual. The download link there is out of date; see
-@uref{http://www.quiktrim.org/#AdditionalResources} for the latest
-download link.
-
-The project may also be frozen; no new code changes have been made
-since approximately 2014.
-
-@item @command{cppawk}
-@cindex @command{cppawk}
-@cindex source code @subentry @command{cppawk}
-Quoting from the web page, ``@command{cppawk} is a tiny shell script that is
-used like @command{awk}. It invokes the C preprocessor (GNU @command{cpp}) on
the Awk
-code and calls Awk on the result.'' This program may be of use if
-the way @command{gawk}'s @code{@@include} facility works doesn't suit
-your needs. For more information, see
@uref{https://www.kylheku.com/cgit/cppawk/}.
-
-@item Other versions
-See also the ``Versions and implementations'' section of the
-@uref{https://en.wikipedia.org/wiki/Awk_language#Versions_and_implementations,
-Wikipedia article} on @command{awk} for information on additional versions.
-
-@end table
-
-An interesting collection of library functions is available
-at @uref{https://github.com/e36freak/awk-libs}.
-
-An interesting collection of @command{gawk} extensions is
-available @uref{https://github.com/su8/gawk-extensions}.
-
-@node Installation summary
-@appendixsec Summary
-
-@itemize @value{BULLET}
-@item
-The @command{gawk} distribution is available from the GNU Project's main
-distribution site, @code{ftp.gnu.org}. The canonical build recipe is:
-
-@example
-wget
https://ftp.gnu.org/gnu/gawk/gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
-tar -xvpzf gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
-cd gawk-@value{VERSION}.@value{PATCHLEVEL}
-./configure && make && make check
-@end example
-
-@quotation NOTE
-Because of the @samp{https://} URL, you may have to supply the
-@option{--no-check-certificate} option to @command{wget} to download
-the file.
-@end quotation
-
-@item
-@command{gawk} may be built on non-POSIX systems as well. The currently
-supported systems are MS-Windows using
-MSYS, MSYS2, MinGW, and Cygwin,
-and OpenVMS.
-Instructions for each system are included in this @value{APPENDIX}.
-
-@item
-Bug reports should be sent via email to @EMAIL{bug-gawk@@gnu.org, bug dash
gawk at gnu dot org}.
-Bug reports should be in English and should include the version of
@command{gawk},
-how it was compiled, and a short program and @value{DF} that demonstrate
-the problem.
-
-@item
-Non-bug emails should be sent to @EMAIL{help-gawk@@gnu.org, help dash gawk at
gnu dot org}.
-Repeatedly sending non-bug emails to the bug list will get you blacklisted
from it.
-
-@item
-There are a number of other freely available @command{awk}
-implementations. Many are POSIX-compliant; others are less so.
-
-@end itemize
-
-
-@ifclear FOR_PRINT
-@node Notes
-@appendix Implementation Notes
-@cindex @command{gawk} @subentry implementation issues
-@cindex implementation issues, @command{gawk}
-
-This appendix contains information mainly of interest to implementers and
-maintainers of @command{gawk}. Everything in it applies specifically to
-@command{gawk} and not to other implementations.
-
-@menu
-* Compatibility Mode:: How to disable certain @command{gawk}
- extensions.
-* Additions:: Making Additions To @command{gawk}.
-* Future Extensions:: New features that may be implemented one day.
-* Implementation Limitations:: Some limitations of the implementation.
-* Extension Design:: Design notes about the extension API.
-* Notes summary:: Summary of implementation notes.
-@end menu
-
-@node Compatibility Mode
-@appendixsec Downward Compatibility and Debugging
-@cindex @command{gawk} @subentry implementation issues @subentry downward
compatibility
-@cindex @command{gawk} @subentry implementation issues @subentry debugging
-@cindex troubleshooting @subentry @command{gawk}
-@cindex implementation issues, @command{gawk} @subentry debugging
-
-@xref{POSIX/GNU},
-for a summary of the GNU extensions to the @command{awk} language and program.
-All of these features can be turned off by invoking @command{gawk} with the
-@option{--traditional} option or with the @option{--posix} option.
-
-If @command{gawk} is compiled for debugging with @samp{-DDEBUG}, then there
-is one more option available on the command line:
-
-@table @code
-@item -Y
-@itemx --parsedebug
-Print out the parse stack information as the program is being parsed.
-@end table
-
-This option is intended only for serious @command{gawk} developers
-and not for the casual user. It probably has not even been compiled into
-your version of @command{gawk}, since it slows down execution.
-
-@node Additions
-@appendixsec Making Additions to @command{gawk}
-
-If you find that you want to enhance @command{gawk} in a significant
-fashion, you are perfectly free to do so. That is the point of having
-free software; the source code is available and you are free to change
-it as you want (@pxref{Copying}).
-
-This @value{SECTION} discusses the ways you might want to change @command{gawk}
-as well as any considerations you should bear in mind.
-
-@menu
-* Accessing The Source:: Accessing the Git repository.
-* Adding Code:: Adding code to the main body of
- @command{gawk}.
-* New Ports:: Porting @command{gawk} to a new operating
- system.
-* Derived Files:: Why derived files are kept in the Git
- repository.
-@end menu
-
-@node Accessing The Source
-@appendixsubsec Accessing The @command{gawk} Git Repository
-
-As @command{gawk} is Free Software, the source code is always available.
-@ref{Gawk Distribution} describes how to get and build the formal,
-released versions of @command{gawk}.
-
-@cindex @command{git} utility
-However, if you want to modify @command{gawk} and contribute back your
-changes, you will probably wish to work with the development version.
-To do so, you will need to access the @command{gawk} source code
-repository. The code is maintained using the
-@uref{https://git-scm.com, Git distributed version control system}.
-You will need to install it if your system doesn't have it.
-Once you have done so, use the command:
-
-@example
-git clone git://git.savannah.gnu.org/gawk.git
-@end example
-
-@noindent
-This clones the @command{gawk} repository. If you are behind a
-firewall that does not allow you to use the Git native protocol, you
-can still access the repository using:
-
-@example
-git clone https://git.savannah.gnu.org/r/gawk.git
-@end example
-
-@noindent
-(Using the @code{https} URL is considered to be more secure.)
-
-Once you have made changes, you can use @samp{git diff} to produce a
-patch, and send that to the @command{gawk} maintainer; see @ref{Bugs},
-for how to do that.
-
-Once upon a time there was Git--CVS gateway for use by people who could
-not install Git. However, this gateway no longer works, so you may have
-better luck using a more modern version control system like Bazaar,
-that has a Git plug-in for working with Git repositories.
-
-@node Adding Code
-@appendixsubsec Adding New Features
-
-@cindex adding @subentry features to @command{gawk}
-@cindex features @subentry adding to @command{gawk}
-@cindex @command{gawk} @subentry features @subentry adding
-You are free to add any new features you like to @command{gawk}.
-However, if you want your changes to be incorporated into the @command{gawk}
-distribution, there are several steps that you need to take in order to
-make it possible to include them:
-
-@enumerate 1
-@item
-Discuss the proposed new feature with the @command{gawk} maintainer.
-The bug list may be used for this. Even if I don't
-wish to include your feature, be aware that you are still free to
-add it and distribute your own ``fork'' of @command{gawk}.
-
-@item
-Before building the new feature into @command{gawk} itself,
-consider writing it as an extension
-(@pxref{Dynamic Extensions}).
-If that's not possible, continue with the rest of the steps in this list.
-
-@item
-Be prepared to sign the appropriate paperwork.
-In order for the FSF to distribute your changes, you must either place
-those changes in the public domain and submit a signed statement to that
-effect, or assign the copyright in your changes to the FSF.
-Both of these actions are easy to do and @emph{many} people have done so
-already. If you have questions, please contact me
-(@pxref{Bugs}),
-or @EMAIL{assign@@gnu.org,assign at gnu dot org}.
-
-@item
-Get the latest version.
-It is much easier for me to integrate changes if they are relative to
-the most recent distributed version of @command{gawk}, or better yet,
-relative to the latest code in the Git repository. If your version of
-@command{gawk} is very old, I may not be able to integrate your changes at all.
-(@xref{Getting},
-for information on getting the latest version of @command{gawk}.)
-
-@item
-@ifnotinfo
-Follow the @cite{GNU Coding Standards}.
-@end ifnotinfo
-@ifinfo
-@xref{Top, , Version, standards, GNU Coding Standards}.
-@end ifinfo
-This document describes how GNU software should be written. If you haven't
-read it, please do so, preferably @emph{before} starting to modify
@command{gawk}.
-(The @cite{GNU Coding Standards} are available from
-the GNU Project's
-@uref{https://www.gnu.org/prep/standards/, website}.
-Texinfo, Info, and DVI versions are also available.)
-
-@cindex @command{gawk} @subentry coding style in
-@item
-Use the @command{gawk} coding style.
-The C code for @command{gawk} follows the instructions in the
-@cite{GNU Coding Standards}, with minor exceptions. The code is formatted
-using the traditional ``K&R'' style, particularly as regards to the placement
-of braces and the use of TABs. In brief, the coding rules for @command{gawk}
-are as follows:
-
-@itemize @value{BULLET}
-@item
-Use ANSI/ISO style (prototype) function headers when defining functions.
-
-@item
-Put the name of the function at the beginning of its own line.
-
-@item
-Use @samp{#elif} instead of nesting @samp{#if} inside @samp{#else}.
-
-@item
-Put the return type of the function, even if it is @code{int}, on the
-line above the line with the name and arguments of the function.
-
-@item
-Put spaces around parentheses used in control structures
-(@code{if}, @code{while}, @code{for}, @code{do}, and @code{switch}).
-
-@item
-Do not parenthesize the expression used with @code{return}.
-
-@item
-Do not put spaces in front of parentheses used in function calls.
-
-@item
-Put spaces around all C operators and after commas in function calls.
-
-@item
-Do not use the comma operator to produce multiple side effects, except
-in @code{for} loop initialization and increment parts, and in macro bodies.
-
-@item
-Use real TABs for indenting, not spaces.
-
-@item
-Use the ``K&R'' brace layout style.
-
-@item
-Use comparisons against @code{NULL} and @code{'\0'} in the conditions of
-@code{if}, @code{while}, and @code{for} statements, as well as in the
@code{case}s
-of @code{switch} statements, instead of just the
-plain pointer or character value.
-
-@item
-Do not, @emph{under any circumstances}, use the @samp{-1 == foo} or
-@samp{0 >= bar} style of comparison expressions. I have known about
-it for decades, and I understand why some people like it. Nonetheless,
-I abhor it with a passion, and code that uses it will never be accepted.
-
-@item
-Use @code{true} and @code{false} for @code{bool} values,
-the @code{NULL} symbolic constant for pointer values,
-and the character constant @code{'\0'} where appropriate, instead of @code{1}
-and @code{0}.
-
-@item
-Provide one-line descriptive comments for each function.
-
-@item
-Do not use the @code{alloca()} function for allocating memory off the
-stack. Its use causes more portability trouble than is worth the minor
-benefit of not having to free the storage. Instead, use @code{malloc()}
-and @code{free()}.
-
-@item
-Do not use comparisons of the form @samp{! strcmp(a, b)} or similar.
-As Henry Spencer once said, ``@code{strcmp()} is not a boolean!''
-Instead, use @samp{strcmp(a, b) == 0}.
-
-@item
-If adding new bit flag values, use explicit hexadecimal constants
-(@code{0x001}, @code{0x002}, @code{0x004}, and so on) instead of
-shifting one left by successive amounts (@samp{(1<<0)}, @samp{(1<<1)},
-and so on).
-@end itemize
-
-@quotation NOTE
-If I have to reformat your code to follow the coding style used in
-@command{gawk}, I may not bother to integrate your changes at all.
-@end quotation
-
-@cindex Texinfo
-@item
-Update the documentation.
-Along with your new code, please supply new sections and/or chapters
-for this @value{DOCUMENT}. If at all possible, please use real
-Texinfo, instead of just supplying unformatted ASCII text (although
-even that is better than no documentation at all).
-Conventions to be followed in @cite{@value{TITLE}} are provided
-after the @samp{@@bye} at the end of the Texinfo source file.
-If possible, please update the @command{man} page as well.
-
-You will also have to sign paperwork for your documentation changes.
-
-@cindex @command{git} utility
-@item
-Submit changes as unified diffs.
-Use @samp{diff -u -r -N} to compare
-the original @command{gawk} source tree with your version.
-I recommend using the GNU version of @command{diff}, or best of all,
-@samp{git diff} or @samp{git format-patch}.
-Send the output produced by @command{diff} to me when you
-submit your changes.
-(@xref{Bugs}, for the electronic mail
-information.)
-
-Using this format makes it easy for me to apply your changes to the
-master version of the @command{gawk} source code (using @command{patch}).
-If I have to apply the changes manually, using a text editor, I may
-not do so, particularly if there are lots of changes.
-
-@item
-Include an entry for the @file{ChangeLog} file with your submission.
-This helps further minimize the amount of work I have to do,
-making it easier for me to accept patches.
-It is simplest if you just make this part of your diff.
-@end enumerate
-
-Although this sounds like a lot of work, please remember that while you
-may write the new code, I have to maintain it and support it. If it
-isn't possible for me to do that with a minimum of extra work, then I
-probably will not.
-
-@node New Ports
-@appendixsubsec Porting @command{gawk} to a New Operating System
-@cindex portability @subentry @command{gawk}
-@cindex operating systems @subentry porting @command{gawk} to
-
-@cindex porting @command{gawk}
-If you want to port @command{gawk} to a new operating system, there are
-several steps:
-
-@enumerate 1
-@item
-Follow the guidelines in
-@ifinfo
-@ref{Adding Code},
-@end ifinfo
-@ifnotinfo
-the previous @value{SECTION}
-@end ifnotinfo
-concerning coding style, submission of diffs, and so on.
-
-@item
-Be prepared to sign the appropriate paperwork.
-In order for the FSF to distribute your code, you must either place
-your code in the public domain and submit a signed statement to that
-effect, or assign the copyright in your code to the FSF.
-Both of these actions are easy to do and @emph{many} people have done so
-already. If you have questions, please contact me, or
-@EMAIL{gnu@@gnu.org, gnu at gnu dot org}.
-
-@item
-When doing a port, bear in mind that your code must coexist peacefully
-with the rest of @command{gawk} and the other ports. Avoid gratuitous
-changes to the system-independent parts of the code. If at all possible,
-avoid sprinkling @samp{#ifdef}s just for your port throughout the
-code.
-
-If the changes needed for a particular system affect too much of the
-code, I probably will not accept them. In such a case, you can, of course,
-distribute your changes on your own, as long as you comply
-with the GPL
-(@pxref{Copying}).
-
-@item
-A number of the files that come with @command{gawk} are maintained by other
-people. Thus, you should not change them
-unless it is for a very good reason; i.e., changes are not out of the
-question, but changes to these files are scrutinized extra carefully.
-These are all the files in the @file{support} directory
-within the @command{gawk} distribution. See there.
-
-@item
-A number of other files are provided by the GNU
-Autotools (Autoconf, Automake, and GNU @command{gettext}).
-You should not change them either, unless it is for a very
-good reason. The files are
-@file{ABOUT-NLS},
-@file{config.guess},
-@file{config.rpath},
-@file{config.sub},
-@file{depcomp},
-@file{INSTALL},
-@file{install-sh},
-@file{missing},
-@file{mkinstalldirs},
-and
-@file{ylwrap}.
-
-@item
-Be willing to continue to maintain the port.
-Non-Unix operating systems are supported by volunteers who maintain
-the code needed to compile and run @command{gawk} on their systems. If no-one
-volunteers to maintain a port, it becomes unsupported and it may
-be necessary to remove it from the distribution.
-
-@item
-Supply an appropriate @file{gawkmisc.???} file.
-Each port has its own @file{gawkmisc.???} that implements certain
-operating system specific functions. This is cleaner than a plethora of
-@samp{#ifdef}s scattered throughout the code. The @file{gawkmisc.c} in
-the main source directory includes the appropriate
-@file{gawkmisc.???} file from each subdirectory.
-Be sure to update it as well.
-
-Each port's @file{gawkmisc.???} file has a suffix reminiscent of the machine
-or operating system for the port---for example, @file{pc/gawkmisc.pc} and
-@file{vms/gawkmisc.vms}. The use of separate suffixes, instead of plain
-@file{gawkmisc.c}, makes it possible to move files from a port's subdirectory
-into the main subdirectory, without accidentally destroying the real
-@file{gawkmisc.c} file. (Currently, this is only an issue for the
-PC operating system ports.)
-
-@item
-Supply a @file{Makefile} as well as any other C source and header files that
are
-necessary for your operating system. All your code should be in a
-separate subdirectory, with a name that is the same as, or reminiscent
-of, either your operating system or the computer system. If possible,
-try to structure things so that it is not necessary to move files out
-of the subdirectory into the main source directory. If that is not
-possible, then be sure to avoid using names for your files that
-duplicate the names of files in the main source directory.
-
-@item
-Update the documentation.
-Please write a section (or sections) for this @value{DOCUMENT} describing the
-installation and compilation steps needed to compile and/or install
-@command{gawk} for your system.
-@end enumerate
-
-Following these steps makes it much easier to integrate your changes
-into @command{gawk} and have them coexist happily with other
-operating systems' code that is already there.
-
-In the code that you supply and maintain, feel free to use a
-coding style and brace layout that suits your taste.
-
-@node Derived Files
-@appendixsubsec Why Generated Files Are Kept In Git
-
-@cindex Git, use of for @command{gawk} source code
-@c From emails written March 22, 2012, to the gawk developers list.
-
-If you look at the @command{gawk} source in the Git
-repository, you will notice that it includes files that are automatically
-generated by GNU infrastructure tools, such as @file{Makefile.in} from
-Automake and even @file{configure} from Autoconf.
-
-This is different from many Free Software projects that do not store
-the derived files, because that keeps the repository less cluttered,
-and it is easier to see the substantive changes when comparing versions
-and trying to understand what changed between commits.
-
-However, there are several reasons why the @command{gawk} maintainer
-likes to have everything in the repository.
-
-First, because it is then easy to reproduce any given version completely,
-without relying upon the availability of (older, likely obsolete, and
-maybe even impossible to find) other tools.
-
-As an extreme example, if you ever even think about trying to compile,
-oh, say, the V7 @command{awk}, you will discover that not only do you
-have to bootstrap the V7 @command{yacc} to do so, but you also need the
-V7 @command{lex}. And the latter is pretty much impossible to bring up
-on a modern GNU/Linux system.@footnote{We tried. It was painful.}
-
-(Or, let's say @command{gawk} 1.2 required @command{bison} whatever-it-was
-in 1989 and that there was no @file{awkgram.c} file in the repository. Is
-there a guarantee that we could find that @command{bison} version? Or that
-@emph{it} would build?)
-
-If the repository has all the generated files, then it's easy to just check
-them out and build. (Or @emph{easier}, depending upon how far back we go.)
-
-And that brings us to the second (and stronger) reason why all the files
-really need to be in Git. It boils down to who do you cater
-to---the @command{gawk} developer(s), or the user who just wants to check
-out a version and try it out?
-
-The @command{gawk} maintainer
-wants it to be possible for any interested @command{awk} user in the
-world to just clone the repository, check out the branch of interest and
-build it, without their having to have the correct version(s) of the
-autotools.@footnote{There is one GNU program that is (in our opinion)
-severely difficult to bootstrap from the Git repository. For
-example, on the author's old (but still working) PowerPC Macintosh with
-macOS 10.5, it was necessary to bootstrap a ton of software, starting
-with Git itself, in order to try to work with the latest code.
-It's not pleasant, and especially on older systems, it's a big waste
-of time.
-
-Starting with the latest tarball was no picnic either. The maintainers
-had dropped @file{.gz} and @file{.bz2} files and only distribute
-@file{.tar.xz} files. It was necessary to bootstrap @command{xz} first!}
-That is the point of the @file{bootstrap.sh} file. It touches the
-various other files in the right order such that
-
-@example
-# The canonical incantation for building GNU software:
-./bootstrap.sh && ./configure && make
-@end example
-
-@noindent
-will @emph{just work}.
-
-This is extremely important for the @code{master} and
-@code{gawk-@var{X}.@var{Y}-stable} branches.
-
-Further, the @command{gawk} maintainer would argue that it's also
-important for the @command{gawk} developers. When he tried to check out
-the @code{xgawk} branch@footnote{A branch (since removed) created by one of
the other
-developers that did not include the generated files.} to build it, he
-couldn't. (No @file{ltmain.sh} file, and he had no idea how to create it,
-and that was not the only problem.)
-
-He felt @emph{extremely} frustrated. With respect to that branch,
-the maintainer is no different than Jane User who wants to try to build
-@code{gawk-4.1-stable} or @code{master} from the repository.
-
-Thus, the maintainer thinks that it's not just important, but critical,
-that for any given branch, the above incantation @emph{just works}.
-
-@c Added 9/2014:
-A third reason to have all the files is that without them, using @samp{git
-bisect} to try to find the commit that introduced a bug is exceedingly
-difficult. The maintainer tried to do that on another project that
-requires running bootstrapping scripts just to create @command{configure}
-and so on; it was really painful. When the repository is self-contained,
-using @command{git bisect} in it is very easy.
-
-@c So - that's my reasoning and philosophy.
-
-What are some of the consequences and/or actions to take?
-
-@enumerate 1
-@item
-We don't mind that there are differing files in the different branches
-as a result of different versions of the autotools.
-
-@enumerate A
-@item
-It's the maintainer's job to merge them and he will deal with it.
-
-@item
-He is really good at @samp{git diff x y > /tmp/diff1 ; gvim /tmp/diff1} to
-remove the diffs that aren't of interest in order to review code.
-@end enumerate
-
-@item
-It would certainly help if everyone used the same versions of the GNU tools
-as he does, which in general are the latest released versions of
-Automake,
-Autoconf,
-@command{bison},
-GNU @command{gettext},
-and
-Libtool.
-
-@ignore
-If it would help if I sent out an ``I just upgraded to version x.y
-of tool Z'' kind of message to this list, I can do that. Up until
-now it hasn't been a real issue since I'm the only one who's been
-dorking with the configuration machinery.
-@end ignore
-
-@c @enumerate A
-@c @item
-@cindex @env{PATH} environment variable
-@cindex environment variables @subentry @env{PATH}
-Installing from source is quite easy. It's how the maintainer worked for years
-(and still works).
-He had @file{/usr/local/bin} at the front of his @env{PATH} and just did:
-
-@example
-wget
https://ftp.gnu.org/gnu/@var{package}/@var{package}-@var{x}.@var{y}.@var{z}.tar.gz
-tar -xpzvf @var{package}-@var{x}.@var{y}.@var{z}.tar.gz
-cd @var{package}-@var{x}.@var{y}.@var{z}
-./configure && make && make check
-make install # as root
-@end example
-
-@quotation NOTE
-Because of the @samp{https://} URL, you may have to supply the
-@option{--no-check-certificate} option to @command{wget} to download
-the file.
-@end quotation
-
-@c @item
-@ignore
-These days the maintainer uses Ubuntu 12.04 which is medium current, but
-he is already doing the above for Automake, Autoconf, and @command{bison}.
-@end ignore
-
-@ignore
-(C. Rant: Recent Linux versions with GNOME 3 really suck. What
- are all those people thinking? Fedora 15 was such a bust it drove
- me to Ubuntu, but Ubuntu 11.04 and 11.10 are totally unusable from
- a UI perspective. Bleah.)
-@end ignore
-@c @end enumerate
-
-@ignore
-@item
-If someone still feels really strongly about all this, then perhaps they
-can have two branches, one for their development with just the clean
-changes, and one that is buildable (xgawk and xgawk-buildable, maybe).
-Or, as I suggested in another mail, make commits in pairs, the first with
-the "real" changes and the second with "everything else needed for
- building".
-@end ignore
-@end enumerate
-
-Most of the above was originally written by the maintainer to other
-@command{gawk} developers. It raised the objection from one of
-the developers ``@dots{} that anybody pulling down the source from
-Git is not an end user.''
-
-However, this is not true. There are ``power @command{awk} users''
-who can build @command{gawk} (using the magic incantation shown previously)
-but who can't program in C. Thus, the major branches should be
-kept buildable all the time.
-
-It was then suggested that there be a @command{cron} job to create
-nightly tarballs of ``the source.'' Here, the problem is that there
-are source trees, corresponding to the various branches! So,
-nightly tarballs aren't the answer, especially as the repository can go
-for weeks without significant change being introduced.
-
-Fortunately, the Git server can meet this need. For any given
-branch named @var{branchname}, use:
-
-@example
-wget
https://git.savannah.gnu.org/cgit/gawk.git/snapshot/gawk-@var{branchname}.tar.gz
-@end example
-
-@noindent
-to retrieve a snapshot of the given branch.
-
-@node Future Extensions
-@appendixsec Probable Future Extensions
-@ignore
-From emory!scalpel.netlabs.com!lwall Tue Oct 31 12:43:17 1995
-Return-Path: <emory!scalpel.netlabs.com!lwall>
-Message-Id: <9510311732.AA28472@scalpel.netlabs.com>
-To: arnold@skeeve.atl.ga.us (Arnold D. Robbins)
-Subject: Re: May I quote you?
-In-Reply-To: Your message of "Tue, 31 Oct 95 09:11:00 EST."
- <m0tAHPQ-00014MC@skeeve.atl.ga.us>
-Date: Tue, 31 Oct 95 09:32:46 -0800
-From: Larry Wall <emory!scalpel.netlabs.com!lwall>
-
-: Greetings. I am working on the release of gawk 3.0. Part of it will be a
-: thoroughly updated manual. One of the sections deals with planned future
-: extensions and enhancements. I have the following at the beginning
-: of it:
-:
-: @cindex PERL
-: @cindex Wall, Larry
-: @display
-: @i{AWK is a language similar to PERL, only considerably more elegant.} @*
-: Arnold Robbins
-: @sp 1
-: @i{Hey!} @*
-: Larry Wall
-: @end display
-:
-: Before I actually release this for publication, I wanted to get your
-: permission to quote you. (Hopefully, in the spirit of much of GNU, the
-: implied humor is visible... :-)
-
-I think that would be fine.
-
-Larry
-@end ignore
-@cindex Perl
-@cindex Wall, Larry
-@cindex Robbins @subentry Arnold
-@quotation
-@i{AWK is a language similar to PERL, only considerably more elegant.}
-@author Arnold Robbins
-@end quotation
-
-@quotation
-@i{Hey!}
-@author Larry Wall
-@end quotation
-
-The @file{TODO} file in the @code{master} branch of the @command{gawk}
-Git repository lists possible future enhancements. Some of these relate
-to the source code, and others to possible new features. Please see
-that file for the list.
-@xref{Additions},
-if you are interested in tackling any of the projects listed there.
-
-@node Implementation Limitations
-@appendixsec Some Limitations of the Implementation
-
-This following table describes limits of @command{gawk} on a Unix-like
-system (although it is variable even then). Other systems may have
-different limits.
-
-@multitable @columnfractions .40 .60
-@headitem Item @tab Limit
-@item Characters in a character class @tab 2^(number of bits per byte)
-@item Length of input record in bytes @tab @code{ULONG_MAX}
-@item Length of output record @tab Unlimited
-@item Length of source line @tab Unlimited
-@item Number of fields in a record @tab @code{ULONG_MAX}
-@item Number of file redirections @tab Unlimited
-@item Number of input records in one file @tab @code{MAX_LONG}
-@item Number of input records total @tab @code{MAX_LONG}
-@item Number of pipe redirections @tab min(number of processes per user,
number of open files)
-@item Numeric values @tab Double-precision floating point (if not using MPFR)
-@item Size of a field in bytes @tab @code{ULONG_MAX}
-@item Size of a literal string in bytes @tab @code{ULONG_MAX}
-@item Size of a printf string in bytes @tab @code{ULONG_MAX}
-@end multitable
-
-@node Extension Design
-@appendixsec Extension API Design
-
-This @value{SECTION} documents the design of the extension API,
-including a discussion of some of the history and problems that needed
-to be solved.
-
-The first version of extensions for @command{gawk} was developed in
-the mid-1990s and released with @command{gawk} 3.1 in the late 1990s.
-The basic mechanisms and design remained unchanged for close to 15 years,
-until 2012.
-
-The old extension mechanism used data types and functions from
-@command{gawk} itself, with a ``clever hack'' to install extension
-functions.
-
-@command{gawk} included some sample extensions, of which a few were
-really useful. However, it was clear from the outset that the extension
-mechanism was bolted onto the side and was not really well thought out.
-
-@menu
-* Old Extension Problems:: Problems with the old mechanism.
-* Extension New Mechanism Goals:: Goals for the new mechanism.
-* Extension Other Design Decisions:: Some other design decisions.
-* Extension Future Growth:: Some room for future growth.
-@end menu
-
-@node Old Extension Problems
-@appendixsubsec Problems With The Old Mechanism
-
-The old extension mechanism had several problems:
-
-@itemize @value{BULLET}
-@item
-It depended heavily upon @command{gawk} internals. Any time the
-@code{NODE} structure@footnote{A critical central data structure
-inside @command{gawk}.} changed, an extension would have to be
-recompiled. Furthermore, to really write extensions required understanding
-something about @command{gawk}'s internal functions. There was some
-documentation in this @value{DOCUMENT}, but it was quite minimal.
-
-@item
-Being able to call into @command{gawk} from an extension required linker
-facilities that are common on Unix-derived systems but that did
-not work on MS-Windows systems; users wanting extensions on MS-Windows
-had to statically link them into @command{gawk}, even though MS-Windows
supports
-dynamic loading of shared objects.
-
-@item
-The API would change occasionally as @command{gawk} changed; no compatibility
-between versions was ever offered or planned for.
-@end itemize
-
-Despite the drawbacks, the @command{xgawk} project developers forked
-@command{gawk} and developed several significant extensions. They also
-enhanced @command{gawk}'s facilities relating to file inclusion and
-shared object access.
-
-A new API was desired for a long time, but only in 2012 did the
-@command{gawk} maintainer and the @command{xgawk} developers finally
-start working on it together. More information about the @command{xgawk}
-project is provided in @ref{gawkextlib}.
-
-@node Extension New Mechanism Goals
-@appendixsubsec Goals For A New Mechanism
-
-Some goals for the new API were:
-
-@itemize @value{BULLET}
-@item
-The API should be independent of @command{gawk} internals. Changes in
-@command{gawk} internals should not be visible to the writer of an
-extension function.
-
-@item
-The API should provide @emph{binary} compatibility across @command{gawk}
-releases as long as the API itself does not change.
-
-@item
-The API should enable extensions written in C or C++ to have roughly the
-same ``appearance'' to @command{awk}-level code as @command{awk}
-functions do. This means that extensions should have:
-
-@itemize @value{MINUS}
-@item
-The ability to access function parameters.
-
-@item
-The ability to turn an undefined parameter into an array (call by reference).
-
-@item
-The ability to create, access and update global variables.
-
-@item
-Easy access to all the elements of an array at once (``array flattening'')
-in order to loop over all the element in an easy fashion for C code.
-
-@item
-The ability to create arrays (including @command{gawk}'s true
-arrays of arrays).
-@end itemize
-@end itemize
-
-Some additional important goals were:
-
-@itemize @value{BULLET}
-@item
-The API should use only features in ISO C 90, so that extensions
-can be written using the widest range of C and C++ compilers. The header
-should include the appropriate @samp{#ifdef __cplusplus} and @samp{extern "C"}
-magic so that a C++ compiler could be used. (If using C++, the runtime
-system has to be smart enough to call any constructors and destructors,
-as @command{gawk} is a C program. As of this writing, this has not been
-tested.)
-
-@item
-The API mechanism should not require access to @command{gawk}'s
-symbols@footnote{The @dfn{symbols} are the variables and functions
-defined inside @command{gawk}. Access to these symbols by code
-external to @command{gawk} loaded dynamically at runtime is
-problematic on MS-Windows.} by the compile-time or dynamic linker,
-in order to enable creation of extensions that also work on MS-Windows.
-@end itemize
-
-During development, it became clear that there were other features
-that should be available to extensions, which were also subsequently
-provided:
-
-@itemize @value{BULLET}
-@item
-Extensions should have the ability to hook into @command{gawk}'s
-I/O redirection mechanism. In particular, the @command{xgawk}
-developers provided a so-called ``open hook'' to take over reading
-records. During development, this was generalized to allow
-extensions to hook into input processing, output processing, and
-two-way I/O.
-
-@item
-An extension should be able to provide a ``call back'' function
-to perform cleanup actions when @command{gawk} exits.
-
-@item
-An extension should be able to provide a version string so that
-@command{gawk}'s @option{--version} option can provide information
-about extensions as well.
-@end itemize
-
-The requirement to avoid access to @command{gawk}'s symbols is, at first
-glance, a difficult one to meet.
-
-One design, apparently used by Perl and Ruby and maybe others, would
-be to make the mainline @command{gawk} code into a library, with the
-@command{gawk} utility a small C @code{main()} function linked against
-the library.
-
-This seemed like the tail wagging the dog, complicating build and
-installation and making a simple copy of the @command{gawk} executable
-from one system to another (or one place to another on the same
-system!) into a chancy operation.
-
-Pat Rankin suggested the solution that was adopted.
-@xref{Extension Mechanism Outline}, for the details.
-
-@node Extension Other Design Decisions
-@appendixsubsec Other Design Decisions
-
-As an arbitrary design decision, extensions can read the values of
-predefined variables and arrays (such as @code{ARGV} and @code{FS}), but cannot
-change them, with the exception of @code{PROCINFO}.
-
-The reason for this is to prevent an extension function from affecting
-the flow of an @command{awk} program outside its control. While a real
-@command{awk} function can do what it likes, that is at the discretion
-of the programmer. An extension function should provide a service or
-make a C API available for use within @command{awk}, and not mess with
-@code{FS} or @code{ARGC} and @code{ARGV}.
-
-In addition, it becomes easy to start down a slippery slope. How
-much access to @command{gawk} facilities do extensions need?
-Do they need @code{getline}? What about calling @code{gsub()} or
-compiling regular expressions? What about calling into @command{awk}
-functions? (@emph{That} would be messy.)
-
-In order to avoid these issues, the @command{gawk} developers chose
-to start with the simplest, most basic features that are still truly useful.
-
-Another decision is that although @command{gawk} provides nice things like
-MPFR, and arrays indexed internally by integers, these features are not
-being brought out to the API in order to keep things simple and close to
-traditional @command{awk} semantics. (In fact, arrays indexed internally
-by integers are so transparent that they aren't even documented!)
-
-Additionally, all functions in the API check that their pointer
-input parameters are not @code{NULL}. If they are, they return an error.
-(It is a good idea for extension code to verify that
-pointers received from @command{gawk} are not @code{NULL}.
-Such a thing should not happen, but the @command{gawk} developers
-are only human, and they have been known to occasionally make
-mistakes.)
-
-With time, the API will undoubtedly evolve; the @command{gawk} developers
-expect this to be driven by user needs. For now, the current API seems
-to provide a minimal yet powerful set of features for creating extensions.
-
-@node Extension Future Growth
-@appendixsubsec Room For Future Growth
-
-The API can later be expanded, in at least the following way:
-
-@itemize @value{BULLET}
-@item
-@command{gawk} passes an ``extension id'' into the extension when it
-first loads the extension. The extension then passes this id back
-to @command{gawk} with each function call. This mechanism allows
-@command{gawk} to identify the extension calling into it, should it need
-to know.
-
-@end itemize
-
-Of course, as of this writing, no decisions have been made with respect
-to the above.
-
-@node Notes summary
-@appendixsec Summary
-
-@itemize @value{BULLET}
-@item
-@command{gawk}'s extensions can be disabled with either the
-@option{--traditional} option or with the @option{--posix} option.
-The @option{--parsedebug} option is available if @command{gawk} is
-compiled with @samp{-DDEBUG}.
-
-@item
-The source code for @command{gawk} is maintained in a publicly
-accessible Git repository. Anyone may check it out and view the source.
-
-@item
-Contributions to @command{gawk} are welcome. Following the steps
-outlined in this @value{CHAPTER} will make it easier to integrate
-your contributions into the code base.
-This applies both to new feature contributions and to ports to
-additional operating systems.
-
-@item
-@command{gawk} has some limits---generally those that are imposed by
-the machine architecture.
-
-@item
-The extension API design was intended to solve a number of problems
-with the previous extension mechanism, enable features needed by
-the @code{xgawk} project, and provide binary compatibility going forward.
-
-@item
-The previous extension mechanism is no longer supported and was
-removed from the code base with the 4.2 release.
-
-@end itemize
-
-
-@node Basic Concepts
-@appendix Basic Programming Concepts
-@cindex programming @subentry concepts
-@cindex programming @subentry concepts
-
-This @value{APPENDIX} attempts to define some of the basic concepts
-and terms that are used throughout the rest of this @value{DOCUMENT}.
-As this @value{DOCUMENT} is specifically about @command{awk},
-and not about computer programming in general, the coverage here
-is by necessity fairly cursory and simplistic.
-(If you need more background, there are many
-other introductory texts that you should refer to instead.)
-
-@menu
-* Basic High Level:: The high level view.
-* Basic Data Typing:: A very quick intro to data types.
-@end menu
-
-@node Basic High Level
-@appendixsec What a Program Does
-
-@cindex processing data
-At the most basic level, the job of a program is to process
-some input data and produce results.
-@ifnotdocbook
-See @ref{figure-general-flow}.
-@end ifnotdocbook
-@ifdocbook
-See @inlineraw{docbook, <xref linkend="figure-general-flow"/>}.
-@end ifdocbook
-
-@ifnotdocbook
-@float Figure,figure-general-flow
-@caption{General Program Flow}
-@center @image{gawk_general-program, , , General program flow}
-@end float
-@end ifnotdocbook
-
-@docbook
-<figure id="figure-general-flow" float="0">
-<title>General Program Flow</title>
-<mediaobject>
-<imageobject role="web"><imagedata fileref="general-program.png"
format="PNG"/></imageobject>
-</mediaobject>
-</figure>
-@end docbook
-
-@cindex compiled programs
-@cindex interpreted programs
-The ``program'' in the figure can be either a compiled
-program@footnote{Compiled programs are typically written
-in lower-level languages such as C, C++, or Ada,
-and then translated, or @dfn{compiled}, into a form that
-the computer can execute directly.}
-(such as @command{ls}),
-or it may be @dfn{interpreted}. In the latter case, a machine-executable
-program such as @command{awk} reads your program, and then uses the
-instructions in your program to process the data.
-
-@cindex programming @subentry basic steps
-When you write a program, it usually consists
-of the following, very basic set of steps,
-@ifnotdocbook
-as shown in @ref{figure-process-flow}:
-@end ifnotdocbook
-@ifdocbook
-as shown in @inlineraw{docbook, <xref linkend="figure-process-flow"/>}:
-@end ifdocbook
-
-@ifnotdocbook
-@float Figure,figure-process-flow
-@caption{Basic Program Steps}
-@center @image{gawk_process-flow, , , Basic Program Stages}
-@end float
-@end ifnotdocbook
-
-@docbook
-<figure id="figure-process-flow" float="0">
-<title>Basic Program Stages</title>
-<mediaobject>
-<imageobject role="web"><imagedata fileref="process-flow.png"
format="PNG"/></imageobject>
-</mediaobject>
-</figure>
-@end docbook
-
-@table @asis
-@item Initialization
-These are the things you do before actually starting to process
-data, such as checking arguments, initializing any data you need
-to work with, and so on.
-This step corresponds to @command{awk}'s @code{BEGIN} rule
-(@pxref{BEGIN/END}).
-
-If you were baking a cake, this might consist of laying out all the
-mixing bowls and the baking pan, and making sure you have all the
-ingredients that you need.
-
-@item Processing
-This is where the actual work is done. Your program reads data,
-one logical chunk at a time, and processes it as appropriate.
-
-In most programming languages, you have to manually manage the reading
-of data, checking to see if there is more each time you read a chunk.
-@command{awk}'s pattern-action paradigm
-(@pxref{Getting Started})
-handles the mechanics of this for you.
-
-In baking a cake, the processing corresponds to the actual labor:
-breaking eggs, mixing the flour, water, and other ingredients, and then
putting the cake
-into the oven.
-
-@item Clean Up
-Once you've processed all the data, you may have things you need to
-do before exiting.
-This step corresponds to @command{awk}'s @code{END} rule
-(@pxref{BEGIN/END}).
-
-After the cake comes out of the oven, you still have to wrap it in
-plastic wrap to keep anyone from tasting it, as well as wash
-the mixing bowls and utensils.
-@end table
-
-@cindex algorithms
-An @dfn{algorithm} is a detailed set of instructions necessary to accomplish
-a task, or process data. It is much the same as a recipe for baking
-a cake. Programs implement algorithms. Often, it is up to you to design
-the algorithm and implement it, simultaneously.
-
-@cindex records
-@cindex fields
-The ``logical chunks'' we talked about previously are called @dfn{records},
-similar to the records a company keeps on employees, a school keeps for
-students, or a doctor keeps for patients.
-Each record has many component parts, such as first and last names,
-date of birth, address, and so on. The component parts are referred
-to as the @dfn{fields} of the record.
-
-The act of reading data is termed @dfn{input}, and that of
-generating results, not too surprisingly, is termed @dfn{output}.
-They are often referred to together as ``input/output,''
-and even more often, as ``I/O'' for short.
-(You will also see ``input'' and ``output'' used as verbs.)
-
-@cindex data-driven languages
-@cindex languages, data-driven
-@command{awk} manages the reading of data for you, as well as the
-breaking it up into records and fields. Your program's job is to
-tell @command{awk} what to do with the data. You do this by describing
-@dfn{patterns} in the data to look for, and @dfn{actions} to execute
-when those patterns are seen. This @dfn{data-driven} nature of
-@command{awk} programs usually makes them both easier to write
-and easier to read.
-
-@node Basic Data Typing
-@appendixsec Data Values in a Computer
-
-@cindex variables
-In a program,
-you keep track of information and values in things called @dfn{variables}.
-A variable is just a name for a given value, such as @code{first_name},
-@code{last_name}, @code{address}, and so on.
-@command{awk} has several predefined variables, and it has
-special names to refer to the current input record
-and the fields of the record.
-You may also group multiple
-associated values under one name, as an array.
-
-@cindex values @subentry numeric
-@cindex values @subentry string
-@cindex scalar values
-Data, particularly in @command{awk}, consists of either numeric
-values, such as 42 or 3.1415927, or string values.
-String values are essentially anything that's not a number, such as a name.
-Strings are sometimes referred to as @dfn{character data}, since they
-store the individual characters that comprise them.
-Individual variables, as well as numeric and string variables, are
-referred to as @dfn{scalar} values.
-Groups of values, such as arrays, are not scalars.
-
-@ref{Computer Arithmetic}, provided a basic introduction to numeric
-types (integer and floating-point) and how they are used in a computer.
-Please review that information, including a number of caveats that
-were presented.
-
-@cindex null strings
-While you are probably used to the idea of a number without a value (i.e.,
zero),
-it takes a bit more getting used to the idea of zero-length character data.
-Nevertheless, such a thing exists.
-It is called the @dfn{null string}.
-The null string is character data that has no value.
-In other words, it is empty. It is written in @command{awk} programs
-like this: @code{""}.
-
-Humans are used to working in decimal; i.e., base 10. In base 10,
-numbers go from 0 to 9, and then ``roll over'' into the next
-@iftex
-column. (Remember grade school? @math{42 = 4\times 10 + 2}.)
-@end iftex
-@ifnottex
-column. (Remember grade school? 42 = 4 x 10 + 2.)
-@end ifnottex
-
-There are other number bases though. Computers commonly use base 2
-or @dfn{binary}, base 8 or @dfn{octal}, and base 16 or @dfn{hexadecimal}.
-In binary, each column represents two times the value in the column to
-its right. Each column may contain either a 0 or a 1.
-@iftex
-Thus, binary 1010 represents @math{(1\times 8) + (0\times 4) + (1\times 2) +
(0\times 1)}, or decimal 10.
-@end iftex
-@ifnottex
-Thus, binary 1010 represents (1 x 8) + (0 x 4) + (1 x 2)
-+ (0 x 1), or decimal 10.
-@end ifnottex
-Octal and hexadecimal are discussed more in
-@ref{Nondecimal-numbers}.
-
-At the very lowest level, computers store values as groups of binary digits,
-or @dfn{bits}. Modern computers group bits into groups of eight, called
@dfn{bytes}.
-Advanced applications sometimes have to manipulate bits directly,
-and @command{gawk} provides functions for doing so.
-
-Programs are written in programming languages.
-Hundreds, if not thousands, of programming languages exist.
-One of the most popular is the C programming language.
-The C language had a very strong influence on the design of
-the @command{awk} language.
-
-@cindex Kernighan, Brian
-@cindex Ritchie, Dennis
-There have been several versions of C. The first is often referred to
-as ``K&R'' C, after the initials of Brian Kernighan and Dennis Ritchie,
-the authors of the first book on C. (Dennis Ritchie created the language,
-and Brian Kernighan was one of the creators of @command{awk}.)
-
-In the mid-1980s, an effort began to produce an international standard
-for C. This work culminated in 1989, with the production of the ANSI
-standard for C. This standard became an ISO standard in 1990.
-In 1999, a revised ISO C standard was approved and released.
-Where it makes sense, POSIX @command{awk} is compatible with 1999 ISO C.
-
-
-@node Glossary
-@unnumbered Glossary
-
-@table @asis
-@item Action
-A series of @command{awk} statements attached to a rule. If the rule's
-pattern matches an input record, @command{awk} executes the
-rule's action. Actions are always enclosed in braces.
-(@xref{Action Overview}.)
-
-@cindex Ada programming language
-@cindex programming languages @subentry Ada
-@item Ada
-A programming language originally defined by the U.S.@: Department of
-Defense for embedded programming. It was designed to enforce good
-Software Engineering practices.
-
-@cindex Spencer, Henry
-@cindex @command{sed} utility
-@cindex amazing @command{awk} assembler (@command{aaa})
-@cindex @command{aaa} (amazing @command{awk} assembler) program
-@item Amazing @command{awk} Assembler
-Henry Spencer at the University of Toronto wrote a retargetable assembler
-completely as @command{sed} and @command{awk} scripts. It is thousands
-of lines long, including machine descriptions for several eight-bit
-microcomputers. It is a good example of a program that would have been
-better written in another language.
-@c You can get it from @uref{http://awk.info/?awk100/aaa}.
-
-@cindex amazingly workable formatter (@command{awf})
-@cindex @command{awf} (amazingly workable formatter) program
-@item Amazingly Workable Formatter (@command{awf})
-Henry Spencer at the University of Toronto wrote a formatter that accepts
-a large subset of the @samp{nroff -ms} and @samp{nroff -man} formatting
-commands, using @command{awk} and @command{sh}.
-@c It is available
-@c from @uref{http://awk.info/?tools/awf}.
-
-@item Anchor
-The regexp metacharacters @samp{^} and @samp{$}, which force the match
-to the beginning or end of the string, respectively.
-
-@cindex ANSI
-@item ANSI
-The American National Standards Institute. This organization produces
-many standards, among them the standards for the C and C++ programming
-languages.
-These standards often become international standards as well. See also
-``ISO.''
-
-@item Argument
-An argument can be two different things. It can be an option or a
-@value{FN} passed to a command while invoking it from the command line, or
-it can be something passed to a @dfn{function} inside a program, e.g.
-inside @command{awk}.
-
-In the latter case, an argument can be passed to a function in two ways.
-Either it is given to the called function by value, i.e., a copy of the
-value of the variable is made available to the called function, but the
-original variable cannot be modified by the function itself; or it is
-given by reference, i.e., a pointer to the interested variable is passed to
-the function, which can then directly modify it. In @command{awk}
-scalars are passed by value, and arrays are passed by reference.
-See ``Pass By Value/Reference.''
-
-@item Array
-A grouping of multiple values under the same name.
-Most languages just provide sequential arrays.
-@command{awk} provides associative arrays.
-
-@item Assertion
-A statement in a program that a condition is true at this point in the program.
-Useful for reasoning about how a program is supposed to behave.
-
-@item Assignment
-An @command{awk} expression that changes the value of some @command{awk}
-variable or data object. An object that you can assign to is called an
-@dfn{lvalue}. The assigned values are called @dfn{rvalues}.
-@xref{Assignment Ops}.
-
-@item Associative Array
-Arrays in which the indices may be numbers or strings, not just
-sequential integers in a fixed range.
-
-@item @command{awk} Language
-The language in which @command{awk} programs are written.
-
-@item @command{awk} Program
-An @command{awk} program consists of a series of @dfn{patterns} and
-@dfn{actions}, collectively known as @dfn{rules}. For each input record
-given to the program, the program's rules are all processed in turn.
-@command{awk} programs may also contain function definitions.
-
-@item @command{awk} Script
-Another name for an @command{awk} program.
-
-@item Bash
-The GNU version of the standard shell
-@ifnotinfo
-(the @b{B}ourne-@b{A}gain @b{SH}ell).
-@end ifnotinfo
-@ifinfo
-(the Bourne-Again SHell).
-@end ifinfo
-See also ``Bourne Shell.''
-
-@item Binary
-Base-two notation, where the digits are @code{0}--@code{1}. Since
-electronic circuitry works ``naturally'' in base 2 (just think of Off/On),
-everything inside a computer is calculated using base 2. Each digit
-represents the presence (or absence) of a power of 2 and is called a
-@dfn{bit}. So, for example, the base-two number @code{10101} is
-@iftex
-the same as decimal 21, (@math{(1\times 16) + (1\times 4) + (1\times 1)}).
-@end iftex
-@ifnottex
-the same as decimal 21, ((1 x 16) + (1 x 4) + (1 x 1)).
-@end ifnottex
-
-Since base-two numbers quickly become
-very long to read and write, they are usually grouped by 3 (i.e., they are
-read as octal numbers), or by 4 (i.e., they are read as hexadecimal
-numbers). There is no direct way to insert base 2 numbers in a C program.
-If need arises, such numbers are usually inserted as octal or hexadecimal
-numbers. The number of base-two digits that fit into registers used for
-representing integer numbers in computers is a rough indication of the
-computing power of the computer itself. Most computers nowadays use 64
-bits for representing integer numbers in their registers, but 32-bit,
-16-bit and 8-bit registers have been widely used in the past.
-@xref{Nondecimal-numbers}.
-@item Bit
-Short for ``Binary Digit.''
-All values in computer memory ultimately reduce to binary digits: values
-that are either zero or one.
-Groups of bits may be interpreted differently---as integers,
-floating-point numbers, character data, addresses of other
-memory objects, or other data.
-@command{awk} lets you work with floating-point numbers and strings.
-@command{gawk} lets you manipulate bit values with the built-in
-functions described in
-@ref{Bitwise Functions}.
-
-Computers are often defined by how many bits they use to represent integer
-values. Typical systems are 32-bit systems, but 64-bit systems are
-becoming increasingly popular, and 16-bit systems have essentially
-disappeared.
-
-@item Boolean Expression
-Named after the English mathematician Boole. See also ``Logical Expression.''
-
-@item Bourne Shell
-The standard shell (@file{/bin/sh}) on Unix and Unix-like systems,
-originally written by Steven R.@: Bourne at Bell Laboratories.
-Many shells (Bash, @command{ksh}, @command{pdksh}, @command{zsh}) are
-generally upwardly compatible with the Bourne shell.
-
-@item Braces
-The characters @samp{@{} and @samp{@}}. Braces are used in
-@command{awk} for delimiting actions, compound statements, and function
-bodies.
-
-@item Bracket Expression
-Inside a @dfn{regular expression}, an expression included in square
-brackets, meant to designate a single character as belonging to a
-specified character class. A bracket expression can contain a list of one
-or more characters, like @samp{[abc]}, a range of characters, like
-@samp{[A-Z]}, or a name, delimited by @samp{:}, that designates a known set
-of characters, like @samp{[:digit:]}. The form of bracket expression
-enclosed between @samp{:} is independent of the underlying representation
-of the character themselves, which could utilize the ASCII, EBCDIC, or
-Unicode codesets, depending on the architecture of the computer system, and on
-localization.
-See also ``Regular Expression.''
-
-@item Built-in Function
-The @command{awk} language provides built-in functions that perform various
-numerical, I/O-related, and string computations. Examples are
-@code{sqrt()} (for the square root of a number) and @code{substr()} (for a
-substring of a string).
-@command{gawk} provides functions for timestamp management, bit manipulation,
-array sorting, type checking,
-and runtime string translation.
-(@xref{Built-in}.)
-
-@item Built-in Variable
-@code{ARGC},
-@code{ARGV},
-@code{CONVFMT},
-@code{ENVIRON},
-@code{FILENAME},
-@code{FNR},
-@code{FS},
-@code{NF},
-@code{NR},
-@code{OFMT},
-@code{OFS},
-@code{ORS},
-@code{RLENGTH},
-@code{RSTART},
-@code{RS},
-and
-@code{SUBSEP}
-are the variables that have special meaning to @command{awk}.
-In addition,
-@code{ARGIND},
-@code{BINMODE},
-@code{ERRNO},
-@code{FIELDWIDTHS},
-@code{FPAT},
-@code{IGNORECASE},
-@code{LINT},
-@code{PROCINFO},
-@code{RT},
-and
-@code{TEXTDOMAIN}
-are the variables that have special meaning to @command{gawk}.
-Changing some of them affects @command{awk}'s running environment.
-(@xref{Built-in Variables}.)
-
-@item C
-The system programming language that most GNU software is written in. The
-@command{awk} programming language has C-like syntax, and this @value{DOCUMENT}
-points out similarities between @command{awk} and C when appropriate.
-
-In general, @command{gawk} attempts to be as similar to the 1990 version
-of ISO C as makes sense.
-
-@item C Shell
-The C Shell (@command{csh} or its improved version, @command{tcsh}) is a Unix
shell that was
-created by Bill Joy in the late 1970s. The C shell was differentiated from
-other shells by its interactive features and overall style, which
-looks more like C. The C Shell is not backward compatible with the Bourne
-Shell, so special attention is required when converting scripts
-written for other Unix shells to the C shell, especially with regard to the
management of
-shell variables.
-See also ``Bourne Shell.''
-
-@item C++
-A popular object-oriented programming language derived from C.
-
-@item Character Class
-See ``Bracket Expression.''
-
-@item Character List
-See ``Bracket Expression.''
-
-@cindex ASCII
-@cindex ISO @subentry ISO 8859-1 character set
-@cindex ISO @subentry ISO Latin-1 character set
-@cindex character sets (machine character encodings)
-@cindex Unicode
-@item Character Set
-The set of numeric codes used by a computer system to represent the
-characters (letters, numbers, punctuation, etc.) of a particular country
-or place. The most common character set in use today is ASCII (American
-Standard Code for Information Interchange). Many European
-countries use an extension of ASCII known as ISO-8859-1 (ISO Latin-1).
-The @uref{http://www.unicode.org, Unicode character set} is
-increasingly popular and standard, and is particularly
-widely used on GNU/Linux systems.
-
-@cindex Kernighan, Brian
-@cindex Bentley, Jon
-@cindex @command{chem} utility
-@item CHEM
-A preprocessor for @command{pic} that reads descriptions of molecules
-and produces @command{pic} input for drawing them.
-It was written in @command{awk}
-by Brian Kernighan and Jon Bentley, and is available from
-@uref{http://netlib.org/typesetting/chem}.
-
-@item Comparison Expression
-A relation that is either true or false, such as @samp{a < b}.
-Comparison expressions are used in @code{if}, @code{while}, @code{do},
-and @code{for}
-statements, and in patterns to select which input records to process.
-(@xref{Typing and Comparison}.)
-
-@cindex compiled programs
-@item Compiler
-A program that translates human-readable source code into
-machine-executable object code. The object code is then executed
-directly by the computer.
-See also ``Interpreter.''
-
-@item Complemented Bracket Expression
-The negation of a @dfn{bracket expression}. All that is @emph{not}
-described by a given bracket expression. The symbol @samp{^} precedes
-the negated bracket expression. E.g.: @samp{[^[:digit:]]}
-designates whatever character is not a digit. @samp{[^bad]}
-designates whatever character is not one of the letters @samp{b}, @samp{a},
-or @samp{d}.
-See ``Bracket Expression.''
-
-@item Compound Statement
-A series of @command{awk} statements, enclosed in curly braces. Compound
-statements may be nested.
-(@xref{Statements}.)
-
-@item Computed Regexps
-See ``Dynamic Regular Expressions.''
-
-@item Concatenation
-Concatenating two strings means sticking them together, one after another,
-producing a new string. For example, the string @samp{foo} concatenated with
-the string @samp{bar} gives the string @samp{foobar}.
-(@xref{Concatenation}.)
-
-@item Conditional Expression
-An expression using the @samp{?:} ternary operator, such as
-@samp{@var{expr1} ? @var{expr2} : @var{expr3}}. The expression
-@var{expr1} is evaluated; if the result is true, the value of the whole
-expression is the value of @var{expr2}; otherwise the value is
-@var{expr3}. In either case, only one of @var{expr2} and @var{expr3}
-is evaluated. (@xref{Conditional Exp}.)
-
-@item Control Statement
-A control statement is an instruction to perform a given operation or a set
-of operations inside an @command{awk} program, if a given condition is
-true. Control statements are: @code{if}, @code{for}, @code{while}, and
-@code{do}
-(@pxref{Statements}).
-
-@cindex McIlroy, Doug
-@cindex cookie
-@item Cookie
-A peculiar goodie, token, saying or remembrance
-produced by or presented to a program. (With thanks to Professor Doug McIlroy.)
-@ignore
-From: Doug McIlroy <doug@cs.dartmouth.edu>
-Date: Sat, 13 Oct 2012 19:55:25 -0400
-To: arnold@skeeve.com
-Subject: Re: origin of the term "cookie"?
-
-I believe the term "cookie", for a more or less inscrutable
-saying or crumb of information, was injected into Unix
-jargon by Bob Morris, who used the word quite frequently.
-It had no fixed meaning as it now does in browsers.
-
-The word had been around long before it was recognized in
-the 8th edition glossary (earlier editions had no glossary):
-
-cookie a peculiar goodie, token, saying or remembrance
-returned by or presented to a program. [I would say that
-"returned by" would better read "produced by", and assume
-responsibility for the inexactitude.]
-
-Doug McIlroy
-
-From: Doug McIlroy <doug@cs.dartmouth.edu>
-Date: Sun, 14 Oct 2012 10:08:43 -0400
-To: arnold@skeeve.com
-Subject: Re: origin of the term "cookie"?
-
-> Can I forward your email to Eric Raymond, for possible addition to the
-> Jargon File?
-
-Sure. I might add that I don't know how "cookie" entered Morris's
-vocabulary. Certainly "values of beta give rise to dom!" (see google)
-was an early, if not the earliest Unix cookie. The fact that it was
-found lying around on a model 37 teletype (which had Greek beta in
-its type box) suggests that maybe it was seen to be like milk and
-cookies laid out for Santa Claus. Morris was wont to make such
-connections.
-
-Doug
-@end ignore
-
-@item Coprocess
-A subordinate program with which two-way communications is possible.
-
-@item Curly Braces
-See ``Braces.''
-
-@cindex dark corner
-@item Dark Corner
-An area in the language where specifications often were (or still
-are) not clear, leading to unexpected or undesirable behavior.
-Such areas are marked in this @value{DOCUMENT} with
-@iftex
-the picture of a flashlight in the margin
-@end iftex
-@ifnottex
-``(d.c.)'' in the text
-@end ifnottex
-and are indexed under the heading ``dark corner.''
-
-@item Data Driven
-A description of @command{awk} programs, where you specify the data you
-are interested in processing, and what to do when that data is seen.
-
-@item Data Objects
-These are numbers and strings of characters. Numbers are converted into
-strings and vice versa, as needed.
-(@xref{Conversion}.)
-
-@item Deadlock
-The situation in which two communicating processes are each waiting
-for the other to perform an action.
-
-@item Debugger
-A program used to help developers remove ``bugs'' from (de-bug)
-their programs.
-
-@item Double Precision
-An internal representation of numbers that can have fractional parts.
-Double precision numbers keep track of more digits than do single precision
-numbers, but operations on them are sometimes more expensive. This is the way
-@command{awk} stores numeric values. It is the C type @code{double}.
-
-@item Dynamic Regular Expression
-A dynamic regular expression is a regular expression written as an
-ordinary expression. It could be a string constant, such as
-@code{"foo"}, but it may also be an expression whose value can vary.
-(@xref{Computed Regexps}.)
-
-@item Empty String
-See ``Null String.''
-
-@cindex environment, definition of
-@item Environment
-A collection of strings, of the form @samp{@var{name}=@var{val}}, that each
-program has available to it. Users generally place values into the
-environment in order to provide information to various programs. Typical
-examples are the environment variables @env{HOME} and @env{PATH}.
-
-@cindex epoch, definition of
-@item Epoch
-The date used as the ``beginning of time'' for timestamps.
-Time values in most systems are represented as seconds since the epoch,
-with library functions available for converting these values into
-standard date and time formats.
-
-The epoch on Unix and POSIX systems is 1970-01-01 00:00:00 UTC.
-See also ``GMT'' and ``UTC.''
-
-@item Escape Sequences
-@cindex ASCII
-A special sequence of characters used for describing nonprinting
-characters, such as @samp{\n} for newline or @samp{\033} for the ASCII
-ESC (Escape) character. (@xref{Escape Sequences}.)
-
-@item Extension
-An additional feature or change to a programming language or
-utility not defined by that language's or utility's standard.
-@command{gawk} has (too) many extensions over POSIX @command{awk}.
-
-@item FDL
-See ``Free Documentation License.''
-
-@item Field
-When @command{awk} reads an input record, it splits the record into pieces
-separated by whitespace (or by a separator regexp that you can
-change by setting the predefined variable @code{FS}). Such pieces are
-called fields. If the pieces are of fixed length, you can use the built-in
-variable @code{FIELDWIDTHS} to describe their lengths.
-If you wish to specify the contents of fields instead of the field
-separator, you can use the predefined variable @code{FPAT} to do so.
-(@xref{Field Separators},
-@ref{Constant Size},
-and
-@ref{Splitting By Content}.)
-
-@item Flag
-A variable whose truth value indicates the existence or nonexistence
-of some condition.
-
-@item Floating-Point Number
-Often referred to in mathematical terms as a ``rational'' or real number,
-this is just a number that can have a fractional part.
-See also ``Double Precision'' and ``Single Precision.''
-
-@item Format
-Format strings control the appearance of output in the
-@code{strftime()} and @code{sprintf()} functions, and in the
-@code{printf} statement as well. Also, data conversions from numbers to
strings
-are controlled by the format strings contained in the predefined variables
-@code{CONVFMT} and @code{OFMT}. (@xref{Control Letters}.)
-
-@item Fortran
-Shorthand for FORmula TRANslator, one of the first programming languages
-available for scientific calculations. It was created by John Backus,
-and has been available since 1957. It is still in use today.
-
-@item Free Documentation License
-This document describes the terms under which this @value{DOCUMENT}
-is published and may be copied. (@xref{GNU Free Documentation License}.)
-
-@cindex FSF (Free Software Foundation)
-@cindex Free Software Foundation (FSF)
-@cindex Stallman, Richard
-@item Free Software Foundation
-A nonprofit organization dedicated
-to the production and distribution of freely distributable software.
-It was founded by Richard M.@: Stallman, the author of the original
-Emacs editor. GNU Emacs is the most widely used version of Emacs today.
-
-@item FSF
-See ``Free Software Foundation.''
-
-@item Function
-A part of an @command{awk} program that can be invoked from every point of
-the program, to perform a task. @command{awk} has several built-in
-functions.
-Users can define their own functions in every part of the program.
-Function can be recursive, i.e., they may invoke themselves.
-@xref{Functions}.
-In @command{gawk} it is also possible to have functions shared
-among different programs, and included where required using the
-@code{@@include} directive
-(@pxref{Include Files}).
-In @command{gawk} the name of the function that should be invoked
-can be generated at run time, i.e., dynamically.
-The @command{gawk} extension API provides constructor functions
-(@pxref{Constructor Functions}).
-
-
-@item @command{gawk}
-The GNU implementation of @command{awk}.
-
-@cindex GPL (General Public License)
-@item General Public License
-This document describes the terms under which @command{gawk} and its source
-code may be distributed. (@xref{Copying}.)
-
-@item GMT
-``Greenwich Mean Time.''
-This is the old term for UTC.
-It is the time of day used internally for Unix and POSIX systems.
-See also ``Epoch'' and ``UTC.''
-
-@cindex FSF (Free Software Foundation)
-@cindex Free Software Foundation (FSF)
-@cindex GNU Project
-@item GNU
-``GNU's not Unix''. An on-going project of the Free Software Foundation
-to create a complete, freely distributable, POSIX-compliant computing
-environment.
-
-@item GNU/Linux
-A variant of the GNU system using the Linux kernel, instead of the
-Free Software Foundation's Hurd kernel.
-The Linux kernel is a stable, efficient, full-featured clone of Unix that has
-been ported to a variety of architectures.
-It is most popular on PC-class systems, but runs well on a variety of
-other systems too.
-The Linux kernel source code is available under the terms of the GNU General
-Public License, which is perhaps its most important aspect.
-
-@item GPL
-See ``General Public License.''
-
-@item Hexadecimal
-Base 16 notation, where the digits are @code{0}--@code{9} and
-@code{A}--@code{F}, with @samp{A}
-representing 10, @samp{B} representing 11, and so on, up to @samp{F} for 15.
-Hexadecimal numbers are written in C using a leading @samp{0x},
-@iftex
-to indicate their base. Thus, @code{0x12} is 18 (@math{(1\times 16) + 2}).
-@end iftex
-@ifnottex
-to indicate their base. Thus, @code{0x12} is 18 ((1 x 16) + 2).
-@end ifnottex
-@xref{Nondecimal-numbers}.
-
-@item I/O
-Abbreviation for ``Input/Output,'' the act of moving data into and/or
-out of a running program.
-
-@item Input Record
-A single chunk of data that is read in by @command{awk}. Usually, an
@command{awk} input
-record consists of one line of text.
-(@xref{Records}.)
-
-@item Integer
-A whole number, i.e., a number that does not have a fractional part.
-
-@item Internationalization
-The process of writing or modifying a program so
-that it can use multiple languages without requiring
-further source code changes.
-
-@cindex interpreted programs
-@item Interpreter
-A program that reads human-readable source code directly, and uses
-the instructions in it to process data and produce results.
-@command{awk} is typically (but not always) implemented as an interpreter.
-See also ``Compiler.''
-
-@item Interval Expression
-A component of a regular expression that lets you specify repeated matches of
-some part of the regexp. Interval expressions were not originally available
-in @command{awk} programs.
-
-@cindex ISO
-@item ISO
-The International Organization for Standardization.
-This organization produces international standards for many things, including
-programming languages, such as C and C++.
-In the computer arena, important standards like those for C, C++, and POSIX
-become both American national and ISO international standards simultaneously.
-This @value{DOCUMENT} refers to Standard C as ``ISO C'' throughout.
-See @uref{https://www.iso.org/iso/home/about.htm, the ISO website} for more
-information about the name of the organization and its language-independent
-three-letter acronym.
-
-@cindex Java programming language
-@cindex programming languages @subentry Java
-@item Java
-A modern programming language originally developed by Sun Microsystems
-(now Oracle) supporting Object-Oriented programming. Although usually
-implemented by compiling to the instructions for a standard virtual
-machine (the JVM), the language can be compiled to native code.
-
-@item Keyword
-In the @command{awk} language, a keyword is a word that has special
-meaning. Keywords are reserved and may not be used as variable names.
-
-@command{gawk}'s keywords are:
-@code{BEGIN},
-@code{BEGINFILE},
-@code{END},
-@code{ENDFILE},
-@code{break},
-@code{case},
-@code{continue},
-@code{default},
-@code{delete},
-@code{do@dots{}while},
-@code{else},
-@code{exit},
-@code{for@dots{}in},
-@code{for},
-@code{function},
-@code{func},
-@code{if},
-@code{next},
-@code{nextfile},
-@code{switch},
-and
-@code{while}.
-
-@item Korn Shell
-The Korn Shell (@command{ksh}) is a Unix shell which was developed by David
Korn at Bell
-Laboratories in the early 1980s. The Korn Shell is backward-compatible with
the Bourne
-shell and includes many features of the C shell.
-See also ``Bourne Shell.''
-
-@cindex LGPL (Lesser General Public License)
-@cindex Lesser General Public License (LGPL)
-@cindex GNU Lesser General Public License
-@item Lesser General Public License
-This document describes the terms under which binary library archives
-or shared objects,
-and their source code may be distributed.
-
-@item LGPL
-See ``Lesser General Public License.''
-
-@item Linux
-See ``GNU/Linux.''
-
-@item Localization
-The process of providing the data necessary for an
-internationalized program to work in a particular language.
-
-@item Logical Expression
-An expression using the operators for logic, AND, OR, and NOT, written
-@samp{&&}, @samp{||}, and @samp{!} in @command{awk}. Often called @dfn{Boolean
-expressions}, after the mathematician who pioneered this kind of
-mathematical logic.
-
-@item Lvalue
-An expression that can appear on the left side of an assignment
-operator. In most languages, lvalues can be variables or array
-elements. In @command{awk}, a field designator can also be used as an
-lvalue.
-
-@item Matching
-The act of testing a string against a regular expression. If the
-regexp describes the contents of the string, it is said to @dfn{match} it.
-
-@item Metacharacters
-Characters used within a regexp that do not stand for themselves.
-Instead, they denote regular expression operations, such as repetition,
-grouping, or alternation.
-
-@item Nesting
-Nesting is where information is organized in layers, or where objects
-contain other similar objects.
-In @command{gawk} the @code{@@include}
-directive can be nested. The ``natural'' nesting of arithmetic and
-logical operations can be changed using parentheses
-(@pxref{Precedence}).
-
-@item No-op
-An operation that does nothing.
-
-@item Null String
-A string with no characters in it. It is represented explicitly in
-@command{awk} programs by placing two double quote characters next to
-each other (@code{""}). It can appear in input data by having two successive
-occurrences of the field separator appear next to each other.
-
-@item Number
-A numeric-valued data object. Modern @command{awk} implementations use
-double precision floating-point to represent numbers.
-Ancient @command{awk} implementations used single precision floating-point.
-
-@item Octal
-Base-eight notation, where the digits are @code{0}--@code{7}.
-Octal numbers are written in C using a leading @samp{0},
-@iftex
-to indicate their base. Thus, @code{013} is 11 (@math{(1\times 8) + 3}).
-@end iftex
-@ifnottex
-to indicate their base. Thus, @code{013} is 11 ((1 x 8) + 3).
-@end ifnottex
-@xref{Nondecimal-numbers}.
-
-@item Output Record
-A single chunk of data that is written out by @command{awk}. Usually, an
-@command{awk} output record consists of one or more lines of text.
-@xref{Records}.
-
-@item Pattern
-Patterns tell @command{awk} which input records are interesting to which
-rules.
-
-A pattern is an arbitrary conditional expression against which input is
-tested. If the condition is satisfied, the pattern is said to @dfn{match}
-the input record. A typical pattern might compare the input record against
-a regular expression. (@xref{Pattern Overview}.)
-
-@item PEBKAC
-An acronym describing what is possibly the most frequent
-source of computer usage problems. (Problem Exists Between
-Keyboard And Chair.)
-
-@item Plug-in
-See ``Extensions.''
-
-@item POSIX
-The name for a series of standards
-that specify a Portable Operating System interface. The ``IX'' denotes
-the Unix heritage of these standards. The main standard of interest for
-@command{awk} users is
-@cite{IEEE Standard for Information Technology, Standard 1003.1@sup{TM}-2017
-(Revision of IEEE Std 1003.1-2008)}.
-The 2018 POSIX standard can be found online at
-@url{https://pubs.opengroup.org/onlinepubs/9699919799/}.
-
-@item Precedence
-The order in which operations are performed when operators are used
-without explicit parentheses.
-
-@item Private
-Variables and/or functions that are meant for use exclusively by library
-functions and not for the main @command{awk} program. Special care must be
-taken when naming such variables and functions.
-(@xref{Library Names}.)
-
-@item Range (of input lines)
-A sequence of consecutive lines from the input file(s). A pattern
-can specify ranges of input lines for @command{awk} to process or it can
-specify single lines. (@xref{Pattern Overview}.)
-
-@item Record
-See ``Input record'' and ``Output record.''
-
-@item Recursion
-When a function calls itself, either directly or indirectly.
-If this is clear, stop, and proceed to the next entry.
-Otherwise, refer to the entry for ``recursion.''
-
-@item Redirection
-Redirection means performing input from something other than the standard input
-stream, or performing output to something other than the standard output
stream.
-
-You can redirect input to the @code{getline} statement using
-the @samp{<}, @samp{|}, and @samp{|&} operators.
-You can redirect the output of the @code{print} and @code{printf} statements
-to a file or a system command, using the @samp{>}, @samp{>>}, @samp{|}, and
@samp{|&}
-operators.
-(@xref{Getline},
-and @ref{Redirection}.)
-
-@item Reference Counts
-An internal mechanism in @command{gawk} to minimize the amount of memory
-needed to store the value of string variables. If the value assumed by
-a variable is used in more than one place, only one copy of the value
-itself is kept, and the associated reference count is increased when the
-same value is used by an additional variable, and decreased when the related
-variable is no longer in use. When the reference count goes to zero,
-the memory space used to store the value of the variable is freed.
-
-@item Regexp
-See ``Regular Expression.''
-
-@item Regular Expression
-A regular expression (``regexp'' for short) is a pattern that denotes a
-set of strings, possibly an infinite set. For example, the regular expression
-@samp{R.*xp} matches any string starting with the letter @samp{R}
-and ending with the letters @samp{xp}. In @command{awk}, regular expressions
are
-used in patterns and in conditional expressions. Regular expressions may
contain
-escape sequences. (@xref{Regexp}.)
-
-@item Regular Expression Constant
-A regular expression constant is a regular expression written within
-slashes, such as @code{/foo/}. This regular expression is chosen
-when you write the @command{awk} program and cannot be changed during
-its execution. (@xref{Regexp Usage}.)
-
-@item Regular Expression Operators
-See ``Metacharacters.''
-
-@item Rounding
-Rounding the result of an arithmetic operation can be tricky.
-More than one way of rounding exists, and in @command{gawk}
-it is possible to choose which method should be used in a program.
-@xref{Setting the rounding mode}.
-
-@item Rule
-A segment of an @command{awk} program that specifies how to process single
-input records. A rule consists of a @dfn{pattern} and an @dfn{action}.
-@command{awk} reads an input record; then, for each rule, if the input record
-satisfies the rule's pattern, @command{awk} executes the rule's action.
-Otherwise, the rule does nothing for that input record.
-
-@item Rvalue
-A value that can appear on the right side of an assignment operator.
-In @command{awk}, essentially every expression has a value. These values
-are rvalues.
-
-@item Scalar
-A single value, be it a number or a string.
-Regular variables are scalars; arrays and functions are not.
-
-@item Search Path
-In @command{gawk}, a list of directories to search for @command{awk} program
source files.
-In the shell, a list of directories to search for executable programs.
-
-@item @command{sed}
-See ``Stream Editor.''
-
-@item Seed
-The initial value, or starting point, for a sequence of random numbers.
-
-@item Shell
-The command interpreter for Unix and POSIX-compliant systems.
-The shell works both interactively, and as a programming language
-for batch files, or shell scripts.
-
-@item Short-Circuit
-The nature of the @command{awk} logical operators @samp{&&} and @samp{||}.
-If the value of the entire expression is determinable from evaluating just
-the lefthand side of these operators, the righthand side is not
-evaluated.
-(@xref{Boolean Ops}.)
-
-@item Side Effect
-A side effect occurs when an expression has an effect aside from merely
-producing a value. Assignment expressions, increment and decrement
-expressions, and function calls have side effects.
-(@xref{Assignment Ops}.)
-
-@item Single Precision
-An internal representation of numbers that can have fractional parts.
-Single precision numbers keep track of fewer digits than do double precision
-numbers, but operations on them are sometimes less expensive in terms of CPU
time.
-This is the type used by some ancient versions of @command{awk} to store
-numeric values. It is the C type @code{float}.
-
-@item Space
-The character generated by hitting the space bar on the keyboard.
-
-@item Special File
-A @value{FN} interpreted internally by @command{gawk}, instead of being handed
-directly to the underlying operating system---for example, @file{/dev/stderr}.
-(@xref{Special Files}.)
-
-@item Statement
-An expression inside an @command{awk} program in the action part
-of a pattern--action rule, or inside an
-@command{awk} function. A statement can be a variable assignment,
-an array operation, a loop, etc.
-
-@item Stream Editor
-A program that reads records from an input stream and processes them one
-or more at a time. This is in contrast with batch programs, which may
-expect to read their input files in entirety before starting to do
-anything, as well as with interactive programs which require input from the
-user.
-
-@item String
-A datum consisting of a sequence of characters, such as @samp{I am a
-string}. Constant strings are written with double quotes in the
-@command{awk} language and may contain escape sequences.
-(@xref{Escape Sequences}.)
-
-@item Tab
-The character generated by hitting the @kbd{TAB} key on the keyboard.
-It usually expands to up to eight spaces upon output.
-
-@item Text Domain
-A unique name that identifies an application.
-Used for grouping messages that are translated at runtime
-into the local language.
-
-@item Timestamp
-A value in the ``seconds since the epoch'' format used by Unix
-and POSIX systems. Used for the @command{gawk} functions
-@code{mktime()}, @code{strftime()}, and @code{systime()}.
-See also ``Epoch,'' ``GMT,'' and ``UTC.''
-
-@cindex GNU/Linux
-@cindex Unix
-@cindex BSD-based operating systems
-@cindex NetBSD
-@cindex FreeBSD
-@cindex OpenBSD
-@item Unix
-A computer operating system originally developed in the early 1970's at
-AT&T Bell Laboratories. It initially became popular in universities around
-the world and later moved into commercial environments as a software
-development system and network server system. There are many commercial
-versions of Unix, as well as several work-alike systems whose source code
-is freely available (such as GNU/Linux, @uref{http://www.netbsd.org, NetBSD},
-@uref{https://www.freebsd.org, FreeBSD}, and @uref{http://www.openbsd.org,
OpenBSD}).
-
-@item UTC
-The accepted abbreviation for ``Universal Coordinated Time.''
-This is standard time in Greenwich, England, which is used as a
-reference time for day and date calculations.
-See also ``Epoch'' and ``GMT.''
-
-@item Variable
-A name for a value. In @command{awk}, variables may be either scalars
-or arrays.
-
-@item Whitespace
-A sequence of space, TAB, or newline characters occurring inside an input
-record or a string.
-
-@end table
-
-@end ifclear
-
-@c The GNU General Public License.
-@node Copying
-@unnumbered GNU General Public License
-@ifnotdocbook
-@center Version 3, 29 June 2007
-@end ifnotdocbook
-@docbook
-<subtitle>Version 3, 29 June 2007</subtitle>
-@end docbook
-
-@c This file is intended to be included within another document,
-@c hence no sectioning command or @node.
-
-@display
-Copyright @copyright{} 2007 Free Software Foundation, Inc.
@url{https://fsf.org/}
-
-Everyone is permitted to copy and distribute verbatim copies of this
-license document, but changing it is not allowed.
-@end display
-
-@c fakenode --- for prepinfo
-@heading Preamble
-
-The GNU General Public License is a free, copyleft license for
-software and other kinds of works.
-
-The licenses for most software and other practical works are designed
-to take away your freedom to share and change the works. By contrast,
-the GNU General Public License is intended to guarantee your freedom
-to share and change all versions of a program---to make sure it remains
-free software for all its users. We, the Free Software Foundation,
-use the GNU General Public License for most of our software; it
-applies also to any other work released this way by its authors. You
-can apply it to your programs, too.
-
-When we speak of free software, we are referring to freedom, not
-price. Our General Public Licenses are designed to make sure that you
-have the freedom to distribute copies of free software (and charge for
-them if you wish), that you receive source code or can get it if you
-want it, that you can change the software or use pieces of it in new
-free programs, and that you know you can do these things.
-
-To protect your rights, we need to prevent others from denying you
-these rights or asking you to surrender the rights. Therefore, you
-have certain responsibilities if you distribute copies of the
-software, or if you modify it: responsibilities to respect the freedom
-of others.
-
-For example, if you distribute copies of such a program, whether
-gratis or for a fee, you must pass on to the recipients the same
-freedoms that you received. You must make sure that they, too,
-receive or can get the source code. And you must show them these
-terms so they know their rights.
-
-Developers that use the GNU GPL protect your rights with two steps:
-(1) assert copyright on the software, and (2) offer you this License
-giving you legal permission to copy, distribute and/or modify it.
-
-For the developers' and authors' protection, the GPL clearly explains
-that there is no warranty for this free software. For both users' and
-authors' sake, the GPL requires that modified versions be marked as
-changed, so that their problems will not be attributed erroneously to
-authors of previous versions.
-
-Some devices are designed to deny users access to install or run
-modified versions of the software inside them, although the
-manufacturer can do so. This is fundamentally incompatible with the
-aim of protecting users' freedom to change the software. The
-systematic pattern of such abuse occurs in the area of products for
-individuals to use, which is precisely where it is most unacceptable.
-Therefore, we have designed this version of the GPL to prohibit the
-practice for those products. If such problems arise substantially in
-other domains, we stand ready to extend this provision to those
-domains in future versions of the GPL, as needed to protect the
-freedom of users.
-
-Finally, every program is threatened constantly by software patents.
-States should not allow patents to restrict development and use of
-software on general-purpose computers, but in those that do, we wish
-to avoid the special danger that patents applied to a free program
-could make it effectively proprietary. To prevent this, the GPL
-assures that patents cannot be used to render the program non-free.
-
-The precise terms and conditions for copying, distribution and
-modification follow.
-
-@c fakenode --- for prepinfo
-@heading TERMS AND CONDITIONS
-
-@enumerate 0
-@item Definitions.
-
-``This License'' refers to version 3 of the GNU General Public License.
-
-``Copyright'' also means copyright-like laws that apply to other kinds
-of works, such as semiconductor masks.
-
-``The Program'' refers to any copyrightable work licensed under this
-License. Each licensee is addressed as ``you''. ``Licensees'' and
-``recipients'' may be individuals or organizations.
-
-To ``modify'' a work means to copy from or adapt all or part of the work
-in a fashion requiring copyright permission, other than the making of
-an exact copy. The resulting work is called a ``modified version'' of
-the earlier work or a work ``based on'' the earlier work.
-
-A ``covered work'' means either the unmodified Program or a work based
-on the Program.
-
-To ``propagate'' a work means to do anything with it that, without
-permission, would make you directly or secondarily liable for
-infringement under applicable copyright law, except executing it on a
-computer or modifying a private copy. Propagation includes copying,
-distribution (with or without modification), making available to the
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-
-To ``convey'' a work means any kind of propagation that enables other
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-conveying.
-
-An interactive user interface displays ``Appropriate Legal Notices'' to
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-tells the user that there is no warranty for the work (except to the
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-menu, a prominent item in the list meets this criterion.
-
-@item Source Code.
-
-The ``source code'' for a work means the preferred form of the work for
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-The ``System Libraries'' of an executable work include anything, other
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-The Corresponding Source need not include anything that users can
-regenerate automatically from other parts of the Corresponding Source.
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-The Corresponding Source for a work in source code form is that same
-work.
-
-@item Basic Permissions.
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-All rights granted under this License are granted for the term of
-copyright on the Program, and are irrevocable provided the stated
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-permission to run the unmodified Program. The output from running a
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-You may make, run and propagate covered works that you do not convey,
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-copyrighted material outside their relationship with you.
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-Conveying under any other circumstances is permitted solely under the
-conditions stated below. Sublicensing is not allowed; section 10
-makes it unnecessary.
-
-@item Protecting Users' Legal Rights From Anti-Circumvention Law.
-
-No covered work shall be deemed part of an effective technological
-measure under any applicable law fulfilling obligations under article
-11 of the WIPO copyright treaty adopted on 20 December 1996, or
-similar laws prohibiting or restricting circumvention of such
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-When you convey a covered work, you waive any legal power to forbid
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-respect to the covered work, and you disclaim any intention to limit
-operation or modification of the work as a means of enforcing, against
-the work's users, your or third parties' legal rights to forbid
-circumvention of technological measures.
-
-@item Conveying Verbatim Copies.
-
-You may convey verbatim copies of the Program's source code as you
-receive it, in any medium, provided that you conspicuously and
-appropriately publish on each copy an appropriate copyright notice;
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-notices''.
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-@item
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-@item
-Convey individual copies of the object code with a copy of the written
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-@item
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-@item Additional Terms.
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-Additional terms, permissive or non-permissive, may be stated in the
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-@item Acceptance Not Required for Having Copies.
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-@item Automatic Licensing of Downstream Recipients.
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-@item Patents.
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-Nothing in this License shall be construed as excluding or limiting
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-@item No Surrender of Others' Freedom.
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-@item Use with the GNU Affero General Public License.
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-@item Revised Versions of this License.
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-@item Interpretation of Sections 15 and 16.
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-@heading How to Apply These Terms to Your New Programs
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-@ifclear FOR_PRINT
-@c The GNU Free Documentation License.
-@node GNU Free Documentation License
-@unnumbered GNU Free Documentation License
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-<subtitle>Version 1.3, 3 November 2008</subtitle>
-@end docbook
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Inc.
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-@enumerate 0
-@item
-PREAMBLE
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-@item
-APPLICABILITY AND DEFINITIONS
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-
-The ``Title Page'' means, for a printed book, the title page itself,
-plus such following pages as are needed to hold, legibly, the material
-this License requires to appear in the title page. For works in
-formats which do not have any title page as such, ``Title Page'' means
-the text near the most prominent appearance of the work's title,
-preceding the beginning of the body of the text.
-
-The ``publisher'' means any person or entity that distributes copies
-of the Document to the public.
-
-A section ``Entitled XYZ'' means a named subunit of the Document whose
-title either is precisely XYZ or contains XYZ in parentheses following
-text that translates XYZ in another language. (Here XYZ stands for a
-specific section name mentioned below, such as ``Acknowledgements'',
-``Dedications'', ``Endorsements'', or ``History''.) To ``Preserve the Title''
-of such a section when you modify the Document means that it remains a
-section ``Entitled XYZ'' according to this definition.
-
-The Document may include Warranty Disclaimers next to the notice which
-states that this License applies to the Document. These Warranty
-Disclaimers are considered to be included by reference in this
-License, but only as regards disclaiming warranties: any other
-implication that these Warranty Disclaimers may have is void and has
-no effect on the meaning of this License.
-
-@item
-VERBATIM COPYING
-
-You may copy and distribute the Document in any medium, either
-commercially or noncommercially, provided that this License, the
-copyright notices, and the license notice saying this License applies
-to the Document are reproduced in all copies, and that you add no other
-conditions whatsoever to those of this License. You may not use
-technical measures to obstruct or control the reading or further
-copying of the copies you make or distribute. However, you may accept
-compensation in exchange for copies. If you distribute a large enough
-number of copies you must also follow the conditions in section 3.
-
-You may also lend copies, under the same conditions stated above, and
-you may publicly display copies.
-
-@item
-COPYING IN QUANTITY
-
-If you publish printed copies (or copies in media that commonly have
-printed covers) of the Document, numbering more than 100, and the
-Document's license notice requires Cover Texts, you must enclose the
-copies in covers that carry, clearly and legibly, all these Cover
-Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
-the back cover. Both covers must also clearly and legibly identify
-you as the publisher of these copies. The front cover must present
-the full title with all words of the title equally prominent and
-visible. You may add other material on the covers in addition.
-Copying with changes limited to the covers, as long as they preserve
-the title of the Document and satisfy these conditions, can be treated
-as verbatim copying in other respects.
-
-If the required texts for either cover are too voluminous to fit
-legibly, you should put the first ones listed (as many as fit
-reasonably) on the actual cover, and continue the rest onto adjacent
-pages.
-
-If you publish or distribute Opaque copies of the Document numbering
-more than 100, you must either include a machine-readable Transparent
-copy along with each Opaque copy, or state in or with each Opaque copy
-a computer-network location from which the general network-using
-public has access to download using public-standard network protocols
-a complete Transparent copy of the Document, free of added material.
-If you use the latter option, you must take reasonably prudent steps,
-when you begin distribution of Opaque copies in quantity, to ensure
-that this Transparent copy will remain thus accessible at the stated
-location until at least one year after the last time you distribute an
-Opaque copy (directly or through your agents or retailers) of that
-edition to the public.
-
-It is requested, but not required, that you contact the authors of the
-Document well before redistributing any large number of copies, to give
-them a chance to provide you with an updated version of the Document.
-
-@item
-MODIFICATIONS
-
-You may copy and distribute a Modified Version of the Document under
-the conditions of sections 2 and 3 above, provided that you release
-the Modified Version under precisely this License, with the Modified
-Version filling the role of the Document, thus licensing distribution
-and modification of the Modified Version to whoever possesses a copy
-of it. In addition, you must do these things in the Modified Version:
-
-@enumerate A
-@item
-Use in the Title Page (and on the covers, if any) a title distinct
-from that of the Document, and from those of previous versions
-(which should, if there were any, be listed in the History section
-of the Document). You may use the same title as a previous version
-if the original publisher of that version gives permission.
-
-@item
-List on the Title Page, as authors, one or more persons or entities
-responsible for authorship of the modifications in the Modified
-Version, together with at least five of the principal authors of the
-Document (all of its principal authors, if it has fewer than five),
-unless they release you from this requirement.
-
-@item
-State on the Title page the name of the publisher of the
-Modified Version, as the publisher.
-
-@item
-Preserve all the copyright notices of the Document.
-
-@item
-Add an appropriate copyright notice for your modifications
-adjacent to the other copyright notices.
-
-@item
-Include, immediately after the copyright notices, a license notice
-giving the public permission to use the Modified Version under the
-terms of this License, in the form shown in the Addendum below.
-
-@item
-Preserve in that license notice the full lists of Invariant Sections
-and required Cover Texts given in the Document's license notice.
-
-@item
-Include an unaltered copy of this License.
-
-@item
-Preserve the section Entitled ``History'', Preserve its Title, and add
-to it an item stating at least the title, year, new authors, and
-publisher of the Modified Version as given on the Title Page. If
-there is no section Entitled ``History'' in the Document, create one
-stating the title, year, authors, and publisher of the Document as
-given on its Title Page, then add an item describing the Modified
-Version as stated in the previous sentence.
-
-@item
-Preserve the network location, if any, given in the Document for
-public access to a Transparent copy of the Document, and likewise
-the network locations given in the Document for previous versions
-it was based on. These may be placed in the ``History'' section.
-You may omit a network location for a work that was published at
-least four years before the Document itself, or if the original
-publisher of the version it refers to gives permission.
-
-@item
-For any section Entitled ``Acknowledgements'' or ``Dedications'', Preserve
-the Title of the section, and preserve in the section all the
-substance and tone of each of the contributor acknowledgements and/or
-dedications given therein.
-
-@item
-Preserve all the Invariant Sections of the Document,
-unaltered in their text and in their titles. Section numbers
-or the equivalent are not considered part of the section titles.
-
-@item
-Delete any section Entitled ``Endorsements''. Such a section
-may not be included in the Modified Version.
-
-@item
-Do not retitle any existing section to be Entitled ``Endorsements'' or
-to conflict in title with any Invariant Section.
-
-@item
-Preserve any Warranty Disclaimers.
-@end enumerate
-
-If the Modified Version includes new front-matter sections or
-appendices that qualify as Secondary Sections and contain no material
-copied from the Document, you may at your option designate some or all
-of these sections as invariant. To do this, add their titles to the
-list of Invariant Sections in the Modified Version's license notice.
-These titles must be distinct from any other section titles.
-
-You may add a section Entitled ``Endorsements'', provided it contains
-nothing but endorsements of your Modified Version by various
-parties---for example, statements of peer review or that the text has
-been approved by an organization as the authoritative definition of a
-standard.
-
-You may add a passage of up to five words as a Front-Cover Text, and a
-passage of up to 25 words as a Back-Cover Text, to the end of the list
-of Cover Texts in the Modified Version. Only one passage of
-Front-Cover Text and one of Back-Cover Text may be added by (or
-through arrangements made by) any one entity. If the Document already
-includes a cover text for the same cover, previously added by you or
-by arrangement made by the same entity you are acting on behalf of,
-you may not add another; but you may replace the old one, on explicit
-permission from the previous publisher that added the old one.
-
-The author(s) and publisher(s) of the Document do not by this License
-give permission to use their names for publicity for or to assert or
-imply endorsement of any Modified Version.
-
-@item
-COMBINING DOCUMENTS
-
-You may combine the Document with other documents released under this
-License, under the terms defined in section 4 above for modified
-versions, provided that you include in the combination all of the
-Invariant Sections of all of the original documents, unmodified, and
-list them all as Invariant Sections of your combined work in its
-license notice, and that you preserve all their Warranty Disclaimers.
-
-The combined work need only contain one copy of this License, and
-multiple identical Invariant Sections may be replaced with a single
-copy. If there are multiple Invariant Sections with the same name but
-different contents, make the title of each such section unique by
-adding at the end of it, in parentheses, the name of the original
-author or publisher of that section if known, or else a unique number.
-Make the same adjustment to the section titles in the list of
-Invariant Sections in the license notice of the combined work.
-
-In the combination, you must combine any sections Entitled ``History''
-in the various original documents, forming one section Entitled
-``History''; likewise combine any sections Entitled ``Acknowledgements'',
-and any sections Entitled ``Dedications''. You must delete all
-sections Entitled ``Endorsements.''
-
-@item
-COLLECTIONS OF DOCUMENTS
-
-You may make a collection consisting of the Document and other documents
-released under this License, and replace the individual copies of this
-License in the various documents with a single copy that is included in
-the collection, provided that you follow the rules of this License for
-verbatim copying of each of the documents in all other respects.
-
-You may extract a single document from such a collection, and distribute
-it individually under this License, provided you insert a copy of this
-License into the extracted document, and follow this License in all
-other respects regarding verbatim copying of that document.
-
-@item
-AGGREGATION WITH INDEPENDENT WORKS
-
-A compilation of the Document or its derivatives with other separate
-and independent documents or works, in or on a volume of a storage or
-distribution medium, is called an ``aggregate'' if the copyright
-resulting from the compilation is not used to limit the legal rights
-of the compilation's users beyond what the individual works permit.
-When the Document is included in an aggregate, this License does not
-apply to the other works in the aggregate which are not themselves
-derivative works of the Document.
-
-If the Cover Text requirement of section 3 is applicable to these
-copies of the Document, then if the Document is less than one half of
-the entire aggregate, the Document's Cover Texts may be placed on
-covers that bracket the Document within the aggregate, or the
-electronic equivalent of covers if the Document is in electronic form.
-Otherwise they must appear on printed covers that bracket the whole
-aggregate.
-
-@item
-TRANSLATION
-
-Translation is considered a kind of modification, so you may
-distribute translations of the Document under the terms of section 4.
-Replacing Invariant Sections with translations requires special
-permission from their copyright holders, but you may include
-translations of some or all Invariant Sections in addition to the
-original versions of these Invariant Sections. You may include a
-translation of this License, and all the license notices in the
-Document, and any Warranty Disclaimers, provided that you also include
-the original English version of this License and the original versions
-of those notices and disclaimers. In case of a disagreement between
-the translation and the original version of this License or a notice
-or disclaimer, the original version will prevail.
-
-If a section in the Document is Entitled ``Acknowledgements'',
-``Dedications'', or ``History'', the requirement (section 4) to Preserve
-its Title (section 1) will typically require changing the actual
-title.
-
-@item
-TERMINATION
-
-You may not copy, modify, sublicense, or distribute the Document
-except as expressly provided under this License. Any attempt
-otherwise to copy, modify, sublicense, or distribute it is void, and
-will automatically terminate your rights under this License.
-
-However, if you cease all violation of this License, then your license
-from a particular copyright holder is reinstated (a) provisionally,
-unless and until the copyright holder explicitly and finally
-terminates your license, and (b) permanently, if the copyright holder
-fails to notify you of the violation by some reasonable means prior to
-60 days after the cessation.
-
-Moreover, your license from a particular copyright holder is
-reinstated permanently if the copyright holder notifies you of the
-violation by some reasonable means, this is the first time you have
-received notice of violation of this License (for any work) from that
-copyright holder, and you cure the violation prior to 30 days after
-your receipt of the notice.
-
-Termination of your rights under this section does not terminate the
-licenses of parties who have received copies or rights from you under
-this License. If your rights have been terminated and not permanently
-reinstated, receipt of a copy of some or all of the same material does
-not give you any rights to use it.
-
-@item
-FUTURE REVISIONS OF THIS LICENSE
-
-The Free Software Foundation may publish new, revised versions
-of the GNU Free Documentation License from time to time. Such new
-versions will be similar in spirit to the present version, but may
-differ in detail to address new problems or concerns. See
-@uref{https://www.gnu.org/copyleft/}.
-
-Each version of the License is given a distinguishing version number.
-If the Document specifies that a particular numbered version of this
-License ``or any later version'' applies to it, you have the option of
-following the terms and conditions either of that specified version or
-of any later version that has been published (not as a draft) by the
-Free Software Foundation. If the Document does not specify a version
-number of this License, you may choose any version ever published (not
-as a draft) by the Free Software Foundation. If the Document
-specifies that a proxy can decide which future versions of this
-License can be used, that proxy's public statement of acceptance of a
-version permanently authorizes you to choose that version for the
-Document.
-
-@item
-RELICENSING
-
-``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
-World Wide Web server that publishes copyrightable works and also
-provides prominent facilities for anybody to edit those works. A
-public wiki that anybody can edit is an example of such a server. A
-``Massive Multiauthor Collaboration'' (or ``MMC'') contained in the
-site means any set of copyrightable works thus published on the MMC
-site.
-
-``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
-license published by Creative Commons Corporation, a not-for-profit
-corporation with a principal place of business in San Francisco,
-California, as well as future copyleft versions of that license
-published by that same organization.
-
-``Incorporate'' means to publish or republish a Document, in whole or
-in part, as part of another Document.
-
-An MMC is ``eligible for relicensing'' if it is licensed under this
-License, and if all works that were first published under this License
-somewhere other than this MMC, and subsequently incorporated in whole
-or in part into the MMC, (1) had no cover texts or invariant sections,
-and (2) were thus incorporated prior to November 1, 2008.
-
-The operator of an MMC Site may republish an MMC contained in the site
-under CC-BY-SA on the same site at any time before August 1, 2009,
-provided the MMC is eligible for relicensing.
-
-@end enumerate
-
-@c fakenode --- for prepinfo
-@unnumberedsec ADDENDUM: How to use this License for your documents
-
-To use this License in a document you have written, include a copy of
-the License in the document and put the following copyright and
-license notices just after the title page:
-
-@smallexample
-@group
- Copyright (C) @var{year} @var{your name}.
- Permission is granted to copy, distribute and/or modify this document
- under the terms of the GNU Free Documentation License, Version 1.3
- or any later version published by the Free Software Foundation;
- with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
- Texts. A copy of the license is included in the section entitled ``GNU
- Free Documentation License''.
-@end group
-@end smallexample
-
-If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
-replace the ``with@dots{}Texts.'' line with this:
-
-@smallexample
-@group
- with the Invariant Sections being @var{list their titles}, with
- the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
- being @var{list}.
-@end group
-@end smallexample
-
-If you have Invariant Sections without Cover Texts, or some other
-combination of the three, merge those two alternatives to suit the
-situation.
-
-If your document contains nontrivial examples of program code, we
-recommend releasing these examples in parallel under your choice of
-free software license, such as the GNU General Public License,
-to permit their use in free software.
-
-@end ifclear
-
-@ifnotdocbook
-@node Index
-@unnumbered Index
-@end ifnotdocbook
-@printindex cp
-
-@bye
-
-Unresolved Issues:
-------------------
-1. From ADR.
-
- Robert J. Chassell points out that awk programs should have some indication
- of how to use them. It would be useful to perhaps have a "programming
- style" section of the manual that would include this and other tips.
-
-Consistency issues:
- /.../ regexps are in @code, not @samp
- ".." strings are in @code, not @samp
- no @print before @dots
- values of expressions in the text (@code{x} has the value 15),
- should be in roman, not @code
- Use TAB and not tab
- Use ESC and not ESCAPE
- Use space and not blank to describe the space bar's character
- The term "blank" is thus basically reserved for "blank lines" etc.
- To make dark corners work, the @value{DARKCORNER} has to be outside
- closing `.' of a sentence and after (pxref{...}).
- Make sure that each @value{DARKCORNER} has an index entry, and
- also that each `@cindex dark corner' has an @value{DARKCORNER}.
- " " should have an @w{} around it
- Use "non-" only with language names or acronyms, or the words bug and
option and null
- Use @command{ftp} when talking about anonymous ftp
- Use uppercase and lowercase, not "upper-case" and "lower-case"
- or "upper case" and "lower case"
- Use "single precision" and "double precision", not "single-precision"
or "double-precision"
- Use alphanumeric, not alpha-numeric
- Use POSIX-compliant, not POSIX compliant
- Use --foo, not -Wfoo when describing long options
- Use "Bell Laboratories", but not "Bell Labs".
- Use "behavior" instead of "behaviour".
- Use "coprocess" instead of "co-process".
- Use "zeros" instead of "zeroes".
- Use "nonzero" not "non-zero".
- Use "runtime" not "run time" or "run-time".
- Use "command-line" as an adjective and "command line" as a noun.
- Use "online" not "on-line".
- Use "whitespace" not "white space".
- Use "Input/Output", not "input/output". Also "I/O", not "i/o".
- Use "lefthand"/"righthand", not "left-hand"/"right-hand".
- Use "workaround", not "work-around".
- Use "startup"/"cleanup", not "start-up"/"clean-up"
- Use "filesystem", not "file system"
- Use @code{do}, and not @code{do}-@code{while}, except where
- actually discussing the do-while.
- Use "versus" in text and "vs." in index entries
- Use @code{"C"} for the C locale, not ``C'' or @samp{C}.
- The words "a", "and", "as", "between", "for", "from", "in", "of",
- "on", "that", "the", "to", "with", and "without",
- should not be capitalized in @chapter, @section etc.
- "Into" and "How" should.
- Search for @dfn; make sure important items are also indexed.
- "e.g." should always be followed by a comma.
- "i.e." should always be followed by a comma.
- The numbers zero through ten should be spelled out, except when
- talking about file descriptor numbers. > 10 and < 0, it's
- ok to use numbers.
- For most cases, do NOT put a comma before "and", "or" or "but".
- But exercise taste with this rule.
- Don't show the awk command with a program in quotes when it's
- just the program. I.e.
-
- {
- ....
- }
-
- not
- awk '{
- ...
- }'
-
- Do show it when showing command-line arguments, data files, etc, even
- if there is no output shown.
-
- Use numbered lists only to show a sequential series of steps.
-
- Use @code{xxx} for the xxx operator in indexing statements, not @samp.
- Use MS-Windows not MS Windows
- Use MS-DOS not MS DOS
- Use an empty set of parentheses after built-in and awk function names.
- Use "multiFOO" without a hyphen.
- Use "time zone" as two words, not "timezone".
-
-Date: Wed, 13 Apr 94 15:20:52 -0400
-From: rms@gnu.org (Richard Stallman)
-To: gnu-prog@gnu.org
-Subject: A reminder: no pathnames in GNU
-
-It's a GNU convention to use the term "file name" for the name of a
-file, never "pathname". We use the term "path" for search paths,
-which are lists of file names. Using it for a single file name as
-well is potentially confusing to users.
-
-So please check any documentation you maintain, if you think you might
-have used "pathname".
-
-Note that "file name" should be two words when it appears as ordinary
-text. It's ok as one word when it's a metasyntactic variable, though.
-
-------------------------
-ORA uses filename, thus the macro.
-
-Suggestions:
-------------
-
-Better sidebars can almost sort of be done with:
-
- @ifdocbook
- @macro @sidebar{title, content}
- @inlinefmt{docbook, <sidebar><title>}
- \title\
- @inlinefmt{docbook, </title>}
- \content\
- @inlinefmt{docbook, </sidebar>}
- @end macro
- @end ifdocbook
-
-
- @ifnotdocbook
- @macro @sidebar{title, content}
- @cartouche
- @center @b{\title\}
-
- \content\
- @end cartouche
- @end macro
- @end ifnotdocbook
-
-But to use it you have to say
-
- @sidebar{Title Here,
- @include file-with-content
- }
-
-which sorta sucks.
-
-TODO:
diff --git a/doc/sidebar.awk b/doc/sidebar.awk
deleted file mode 100644
index ca485fa1..00000000
--- a/doc/sidebar.awk
+++ /dev/null
@@ -1,67 +0,0 @@
-# sidebar.awk --- add support for sidebars, other stuff to gawk.texi
-
-# Copyright (C) 2013, 2016 the Free Software Foundation, Inc.
-#
-# This file is part of GAWK, the GNU implementation of the
-# AWK Programming Language.
-#
-# GAWK is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 3 of the License, or
-# (at your option) any later version.
-#
-# GAWK is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, write to the Free Software
-# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
USA
-
-BEGIN {
- print "% ****************************************************"
- print "% * DO NOT MODIFY THIS FILE!!!! *"
- print "% * It was generated from gawktexi.in by sidebar.awk *"
- print "% * Edit gawktexi.in instead. *"
- print "% ****************************************************"
-}
-
-/^@sidebar/ {
- sub(/^@sidebar[ \t]+/, "", $0)
- title = $0
- body = ""
- collecting = 1
- next
-}
-
-/^@end[ \t]+sidebar[ \t]*$/ {
- collecting = 0
- printf "@cindex sidebar @subentry %s\n", title
- printf "@ifdocbook\n"
- printf "@docbook\n"
- printf "<sidebar><title>%s</title>\n", title
- printf "@end docbook\n"
- print body
- print ""
- printf "@docbook\n"
- printf "</sidebar>\n"
- printf "@end docbook\n"
- printf "@end ifdocbook\n\n"
-
- printf "@ifnotdocbook\n"
- printf "@cartouche\n"
- printf "@center @b{%s}\n\n", title
- print body
- printf "@end cartouche\n"
- printf "@end ifnotdocbook\n"
- body = ""
- next
-}
-
-collecting == 1 {
- body = body RS $0
- next
-}
-
-{ print }
diff --git a/doc/texinfo.tex b/doc/texinfo.tex
index e8c382f5..c96d4d7b 100644
--- a/doc/texinfo.tex
+++ b/doc/texinfo.tex
@@ -1,5 +1,5 @@
% texinfo.tex -- TeX macros to handle Texinfo files.
-%
+%
% Load plain if necessary, i.e., if running under initex.
\expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi
%
@@ -212,7 +212,7 @@
% @errormsg{MSG}. Do the index-like expansions on MSG, but if things
% aren't perfect, it's not the end of the world, being an error message,
% after all.
-%
+%
\def\errormsg{\begingroup \indexnofonts \doerrormsg}
\def\doerrormsg#1{\errmessage{#1}}
@@ -425,7 +425,7 @@
}%
}
-% First remove any @comment, then any @c comment. Pass the result on to
+% First remove any @comment, then any @c comment. Pass the result on to
% \argremovespace.
\def\argremovecomment#1\comment#2\ArgTerm{\argremovec #1\c\ArgTerm}
\def\argremovec#1\c#2\ArgTerm{\argremovespace#1$ $\ArgTerm}
@@ -1026,8 +1026,8 @@ where each line of input produces a line of output.}
end
end
}
- % The -2 in the arguments here gives all the input to TeX catcode 12
- % (other) or 10 (space), preventing undefined control sequence errors. See
+ % The -2 in the arguments here gives all the input to TeX catcode 12
+ % (other) or 10 (space), preventing undefined control sequence errors. See
% https://lists.gnu.org/archive/html/bug-texinfo/2019-08/msg00031.html
%
\endgroup
@@ -1129,7 +1129,7 @@ where each line of input produces a line of output.}
% for display in the outlines, and in other places. Thus, we have to
% double any backslashes. Otherwise, a name like "\node" will be
% interpreted as a newline (\n), followed by o, d, e. Not good.
-%
+%
% See http://www.ntg.nl/pipermail/ntg-pdftex/2004-July/000654.html and
% related messages. The final outcome is that it is up to the TeX user
% to double the backslashes and otherwise make the string valid, so
@@ -1421,7 +1421,7 @@ output) for that.)}
% We use the node names as the destinations.
%
% Currently we prefix the section name with the section number
- % for chapter and appendix headings only in order to avoid too much
+ % for chapter and appendix headings only in order to avoid too much
% horizontal space being required in the PDF viewer.
\def\numchapentry##1##2##3##4{%
\dopdfoutline{##2 ##1}{count-\expnumber{chap##2}}{##3}{##4}}%
@@ -1444,7 +1444,7 @@ output) for that.)}
% their "best" equivalent, based on the @documentencoding. Too
% much work for too little return. Just use the ASCII equivalents
% we use for the index sort strings.
- %
+ %
\indexnofonts
\setupdatafile
% We can have normal brace characters in the PDF outlines, unlike
@@ -1670,7 +1670,7 @@ output) for that.)}
% We use node names as destinations.
%
% Currently we prefix the section name with the section number
- % for chapter and appendix headings only in order to avoid too much
+ % for chapter and appendix headings only in order to avoid too much
% horizontal space being required in the PDF viewer.
\def\partentry##1##2##3##4{}% ignore parts in the outlines
\def\numchapentry##1##2##3##4{%
@@ -2697,7 +2697,7 @@ end
}
% Commands to set the quote options.
-%
+%
\parseargdef\codequoteundirected{%
\def\temp{#1}%
\ifx\temp\onword
@@ -2743,7 +2743,7 @@ end
% If we are in a monospaced environment, however, 1) always use \ttsl,
% and 2) do not add an italic correction.
\def\dosmartslant#1#2{%
- \ifusingtt
+ \ifusingtt
{{\ttsl #2}\let\next=\relax}%
{\def\next{{#1#2}\smartitaliccorrection}}%
\next
@@ -2922,7 +2922,7 @@ end
\gdef\codedash{\futurelet\next\codedashfinish}
\gdef\codedashfinish{%
\normaldash % always output the dash character itself.
- %
+ %
% Now, output a discretionary to allow a line break, unless
% (a) the next character is a -, or
% (b) the preceding character is a -, or
@@ -3028,7 +3028,7 @@ end
% For pdfTeX and LuaTeX
\ifurefurlonlylink
% PDF plus option to not display url, show just arg
- \unhbox0
+ \unhbox0
\else
% PDF, normally display both arg and url for consistency,
% visibility, if the pdf is eventually used to print, etc.
@@ -3041,7 +3041,7 @@ end
% For XeTeX
\ifurefurlonlylink
% PDF plus option to not display url, show just arg
- \unhbox0
+ \unhbox0
\else
% PDF, normally display both arg and url for consistency,
% visibility, if the pdf is eventually used to print, etc.
@@ -3099,10 +3099,10 @@ end
}
}
-% By default we'll break after the special characters, but some people like to
-% break before the special chars, so allow that. Also allow no breaking at
+% By default we'll break after the special characters, but some people like to
+% break before the special chars, so allow that. Also allow no breaking at
% all, for manual control.
-%
+%
\parseargdef\urefbreakstyle{%
\def\txiarg{#1}%
\ifx\txiarg\wordnone
@@ -3121,10 +3121,10 @@ end
\def\wordnone{none}
% Allow a ragged right output to aid breaking long URL's. There can
-% be a break at the \allowbreak with no extra glue (if the existing stretch in
+% be a break at the \allowbreak with no extra glue (if the existing stretch in
% the line is sufficient), a break at the \penalty with extra glue added
% at the end of the line, or no break at all here.
-% Changing the value of the penalty and/or the amount of stretch affects how
+% Changing the value of the penalty and/or the amount of stretch affects how
% preferable one choice is over the other.
\def\urefallowbreak{%
\penalty0\relax
@@ -3339,7 +3339,7 @@ $$%
% @inlinefmt{FMTNAME,PROCESSED-TEXT} and @inlineraw{FMTNAME,RAW-TEXT}.
% Ignore unless FMTNAME == tex; then it is like @iftex and @tex,
% except specified as a normal braced arg, so no newlines to worry about.
-%
+%
\def\outfmtnametex{tex}
%
\long\def\inlinefmt#1{\doinlinefmt #1,\finish}
@@ -3347,7 +3347,7 @@ $$%
\def\inlinefmtname{#1}%
\ifx\inlinefmtname\outfmtnametex \ignorespaces #2\fi
}
-%
+%
% @inlinefmtifelse{FMTNAME,THEN-TEXT,ELSE-TEXT} expands THEN-TEXT if
% FMTNAME is tex, else ELSE-TEXT.
\long\def\inlinefmtifelse#1{\doinlinefmtifelse #1,,,\finish}
@@ -3363,7 +3363,7 @@ $$%
% *right* brace they would have to use a command anyway, so they may as
% well use a command to get a left brace too. We could re-use the
% delimiter character idea from \verb, but it seems like overkill.
-%
+%
\long\def\inlineraw{\tex \doinlineraw}
\long\def\doinlineraw#1{\doinlinerawtwo #1,\finish}
\def\doinlinerawtwo#1,#2,\finish{%
@@ -3649,7 +3649,7 @@ $$%
% for non-CM glyphs. That is ec* for regular text and tc* for the text
% companion symbols (LaTeX TS1 encoding). Both are part of the ec
% package and follow the same conventions.
-%
+%
\def\ecfont{\etcfont{e}}
\def\tcfont{\etcfont{t}}
%
@@ -3731,7 +3731,7 @@ $$%
after the title page.}}%
\def\setshortcontentsaftertitlepage{%
\errmessage{@setshortcontentsaftertitlepage has been removed as a Texinfo
- command; move your @shortcontents and @contents commands if you
+ command; move your @shortcontents and @contents commands if you
want the contents after the title page.}}%
\parseargdef\shorttitlepage{%
@@ -3785,7 +3785,7 @@ $$%
% don't worry much about spacing, ragged right. This should be used
% inside a \vbox, and fonts need to be set appropriately first. \par should
% be specified before the end of the \vbox, since a vbox is a group.
-%
+%
\def\raggedtitlesettings{%
\rm
\hyphenpenalty=10000
@@ -4611,7 +4611,7 @@ $$%
% Like \expandablevalue, but completely expandable (the \message in the
% definition above operates at the execution level of TeX). Used when
% writing to auxiliary files, due to the expansion that \write does.
-% If flag is undefined, pass through an unexpanded @value command: maybe it
+% If flag is undefined, pass through an unexpanded @value command: maybe it
% will be set by the time it is read back in.
%
% NB flag names containing - or _ may not work here.
@@ -4635,7 +4635,7 @@ $$%
% @ifset VAR ... @end ifset reads the `...' iff VAR has been defined
% with @set.
-%
+%
% To get the special treatment we need for `@end ifset,' we call
% \makecond and then redefine.
%
@@ -4668,7 +4668,7 @@ $$%
% without the @) is in fact defined. We can only feasibly check at the
% TeX level, so something like `mathcode' is going to considered
% defined even though it is not a Texinfo command.
-%
+%
\makecond{ifcommanddefined}
\def\ifcommanddefined{\parsearg{\doifcmddefined{\let\next=\ifcmddefinedfail}}}
%
@@ -4774,7 +4774,7 @@ $$%
\def\docodeindex#1{\edef\indexname{#1}\parsearg\docodeindexxxx}
\def\docodeindexxxx #1{\docind{\indexname}{#1}}
-
+
% \definedummyword defines \#1 as \string\#1\space, thus effectively
% preventing its expansion. This is used only for control words,
% not control letters, because the \space would be incorrect for
@@ -4791,7 +4791,7 @@ $$%
\def\definedummyword #1{\def#1{\string#1\space}}%
\def\definedummyletter#1{\def#1{\string#1}}%
-% Used for the aux, toc and index files to prevent expansion of Texinfo
+% Used for the aux, toc and index files to prevent expansion of Texinfo
% commands. Most of the commands are controlled through the
% \ifdummies conditional.
%
@@ -5081,7 +5081,7 @@ $$%
\let\value\indexnofontsvalue
}
-
+
% #1 is the index name, #2 is the entry text.
@@ -5122,7 +5122,7 @@ $$%
\ifx\suffix\indexisfl\def\suffix{f1}\fi
% Open the file
\immediate\openout\csname#1indfile\endcsname \jobname.\suffix
- % Using \immediate above here prevents an object entering into the current
+ % Using \immediate above here prevents an object entering into the current
% box, which could confound checks such as those in \safewhatsit for
% preceding skips.
\typeout{Writing index file \jobname.\suffix}%
@@ -5174,7 +5174,7 @@ $$%
\ifx\segment\isfinish
\else
%
- % Fully expand the segment, throwing away any @sortas directives, and
+ % Fully expand the segment, throwing away any @sortas directives, and
% trim spaces.
\edef\trimmed{\segment}%
\edef\trimmed{\expandafter\eatspaces\expandafter{\trimmed}}%
@@ -5238,12 +5238,12 @@ $$%
% the current value of \escapechar.
\def\escapeisbackslash{\escapechar=`\\}
-% Use \ in index files by default. texi2dvi didn't support @ as the escape
-% character (as it checked for "\entry" in the files, and not "@entry"). When
-% the new version of texi2dvi has had a chance to become more prevalent, then
-% the escape character can change back to @ again. This should be an easy
-% change to make now because both @ and \ are only used as escape characters in
-% index files, never standing for themselves.
+% Use \ in index files by default. texi2dvi didn't support @ as the escape
+% character (as it checked for "\entry" in the files, and not "@entry"). When
+% the new version of texi2dvi has had a chance to become more prevalent, then
+% the escape character can change back to @ again. This should be an easy
+% change to make now because both @ and \ are only used as escape characters
in
+% index files, never standing for themselves.
%
\set txiindexescapeisbackslash
@@ -5266,7 +5266,7 @@ $$%
\def\}{\rbracechar{}}%
\uccode`\~=`\\ \uppercase{\def~{\backslashchar{}}}%
%
- % Split the entry into primary entry and any subentries, and get the index
+ % Split the entry into primary entry and any subentries, and get the index
% sort key.
\splitindexentry\indextext
%
@@ -5447,18 +5447,18 @@ $$%
\uccode`\~=`\\ \uppercase{\if\noexpand~}\noexpand#1
\ifflagclear{txiskipindexfileswithbackslash}{%
\errmessage{%
-ERROR: A sorted index file in an obsolete format was skipped.
+ERROR: A sorted index file in an obsolete format was skipped.
To fix this problem, please upgrade your version of 'texi2dvi'
or 'texi2pdf' to that at <https://ftp.gnu.org/gnu/texinfo>.
-If you are using an old version of 'texindex' (part of the Texinfo
+If you are using an old version of 'texindex' (part of the Texinfo
distribution), you may also need to upgrade to a newer version (at least 6.0).
You may be able to typeset the index if you run
'texindex \jobname.\indexname' yourself.
-You could also try setting the 'txiindexescapeisbackslash' flag by
+You could also try setting the 'txiindexescapeisbackslash' flag by
running a command like
-'texi2dvi -t "@set txiindexescapeisbackslash" \jobname.texi'. If you do
+'texi2dvi -t "@set txiindexescapeisbackslash" \jobname.texi'. If you do
this, Texinfo will try to use index files in the old format.
-If you continue to have problems, deleting the index files and starting again
+If you continue to have problems, deleting the index files and starting again
might help (with 'rm \jobname.?? \jobname.??s')%
}%
}{%
@@ -5531,7 +5531,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% bottom of a column to reduce an increase in inter-line spacing.
\nobreak
\vskip 0pt plus 5\baselineskip
- \penalty -300
+ \penalty -300
\vskip 0pt plus -5\baselineskip
%
% Typeset the initial. Making this add up to a whole number of
@@ -5851,7 +5851,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\newbox\balancedcolumns
\setbox\balancedcolumns=\vbox{shouldnt see this}%
%
-% Only called for the last of the double column material. \doublecolumnout
+% Only called for the last of the double column material. \doublecolumnout
% does the others.
\def\balancecolumns{%
\setbox0 = \vbox{\unvbox\PAGE}% like \box255 but more efficient, see p.120.
@@ -5879,7 +5879,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}%
% Now the left column is in box 1, and the right column in box 3.
%
- % Check whether the left column has come out higher than the page itself.
+ % Check whether the left column has come out higher than the page itself.
% (Note that we have doubled \vsize for the double columns, so
% the actual height of the page is 0.5\vsize).
\ifdim2\ht1>\vsize
@@ -6176,7 +6176,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\let\top\unnumbered
% Sections.
-%
+%
\outer\parseargdef\numberedsec{\numhead1{#1}} % normally calls seczzz
\def\seczzz#1{%
\global\subsecno=0 \global\subsubsecno=0 \global\advance\secno by 1
@@ -6199,7 +6199,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}
% Subsections.
-%
+%
% normally calls numberedsubseczzz:
\outer\parseargdef\numberedsubsec{\numhead2{#1}}
\def\numberedsubseczzz#1{%
@@ -6224,7 +6224,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}
% Subsubsections.
-%
+%
% normally numberedsubsubseczzz:
\outer\parseargdef\numberedsubsubsec{\numhead3{#1}}
\def\numberedsubsubseczzz#1{%
@@ -7409,7 +7409,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% @indentedblock is like @quotation, but indents only on the left and
% has no optional argument.
-%
+%
\makedispenvdef{indentedblock}{\indentedblockstart}
%
\def\indentedblockstart{%
@@ -7723,7 +7723,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% @deftypefnnewline on|off says whether the return type of typed functions
% are printed on their own line. This affects @deftypefn, @deftypefun,
% @deftypeop, and @deftypemethod.
-%
+%
\parseargdef\deftypefnnewline{%
\def\temp{#1}%
\ifx\temp\onword
@@ -7893,7 +7893,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\tclose{\temp}% typeset the return type
\ifrettypeownline
% put return type on its own line; prohibit line break following:
- \hfil\vadjust{\nobreak}\break
+ \hfil\vadjust{\nobreak}\break
\else
\space % type on same line, so just followed by a space
\fi
@@ -8043,7 +8043,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\scantokens{#1@comment}%
%
% The \comment is to remove the \newlinechar added by \scantokens, and
- % can be noticed by \parsearg. Note \c isn't used because this means cedilla
+ % can be noticed by \parsearg. Note \c isn't used because this means
cedilla
% in math mode.
}
@@ -8238,7 +8238,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% list to some hook where the argument is to be expanded. If there are
% less than 10 arguments that hook is to be replaced by ##N where N
% is the position in that list, that is to say the macro arguments are to be
-% defined `a la TeX in the macro body.
+% defined `a la TeX in the macro body.
%
% That gets used by \mbodybackslash (above).
%
@@ -8272,7 +8272,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
%
% Read recursive and nonrecursive macro bodies. (They're different since
% rec and nonrec macros end differently.)
-%
+%
% We are in \macrobodyctxt, and the \xdef causes backslashes in the macro
% body to be transformed.
% Set \macrobody to the body of the macro, and call \macrodef.
@@ -8307,7 +8307,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% twice the \macarg.BLAH macros does not cost too much processing power.
\def\parsemmanyargdef@@#1,{%
\if#1;\let\next=\relax
- \else
+ \else
\let\next=\parsemmanyargdef@@
\edef\tempb{\eatspaces{#1}}%
\expandafter\def\expandafter\tempa
@@ -8392,7 +8392,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% Replace arguments by their values in the macro body, and place the result
% in macro \@tempa.
-%
+%
\def\macvalstoargs@{%
% To do this we use the property that token registers that are \the'ed
% within an \edef expand only once. So we are going to place all argument
@@ -8416,9 +8416,9 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\expandafter\def\expandafter\@tempa\expandafter{\@tempc}%
}
-% Define the named-macro outside of this group and then close this group.
-%
-\def\macargexpandinbody@{%
+% Define the named-macro outside of this group and then close this group.
+%
+\def\macargexpandinbody@{%
\expandafter
\endgroup
\macargdeflist@
@@ -8456,7 +8456,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
}
% Trailing missing arguments are set to empty.
-%
+%
\def\setemptyargvalues@{%
\ifx\paramlist\nilm@
\let\next\macargexpandinbody@
@@ -8534,7 +8534,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\else % at most 9
\ifnum\paramno<10\relax
% @MACNAME sets the context for reading the macro argument
- % @MACNAME@@ gets the argument, processes backslashes and appends a
+ % @MACNAME@@ gets the argument, processes backslashes and appends a
% comma.
% @MACNAME@@@ removes braces surrounding the argument list.
% @MACNAME@@@@ scans the macro body with arguments substituted.
@@ -8578,11 +8578,11 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% Call #1 with a list of tokens #2, with any doubled backslashes in #2
% compressed to one.
%
-% This implementation works by expansion, and not execution (so we cannot use
-% \def or similar). This reduces the risk of this failing in contexts where
-% complete expansion is done with no execution (for example, in writing out to
+% This implementation works by expansion, and not execution (so we cannot use
+% \def or similar). This reduces the risk of this failing in contexts where
+% complete expansion is done with no execution (for example, in writing out to
% an auxiliary file for an index entry).
-%
+%
% State is kept in the input stream: the argument passed to
% @look_ahead, @gobble_and_check_finish and @add_segment is
%
@@ -8604,11 +8604,11 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% #3 - NEXT_TOKEN
% #4 used to look ahead
%
-% If the next token is not a backslash, process the rest of the argument;
+% If the next token is not a backslash, process the rest of the argument;
% otherwise, remove the next token.
@gdef@look_ahead#1!#2#3#4{%
@ifx#4\%
- @expandafter@gobble_and_check_finish
+ @expandafter@gobble_and_check_finish
@else
@expandafter@add_segment
@fi#1!{#2}#4#4%
@@ -8632,9 +8632,9 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% #3 - NEXT_TOKEN
% #4 is input stream until next backslash
%
-% Input stream is either at the start of the argument, or just after a
-% backslash sequence, either a lone backslash, or a doubled backslash.
-% NEXT_TOKEN contains the first token in the input stream: if it is \finish,
+% Input stream is either at the start of the argument, or just after a
+% backslash sequence, either a lone backslash, or a doubled backslash.
+% NEXT_TOKEN contains the first token in the input stream: if it is \finish,
% finish; otherwise, append to ARG_RESULT the segment of the argument up until
% the next backslash. PENDING_BACKSLASH contains a backslash to represent
% a backslash just before the start of the input stream that has not been
@@ -8646,13 +8646,13 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% append the pending backslash to the result, followed by the next segment
@expandafter@is_fi@look_ahead#1#2#4!{\}@fi
% this @fi is discarded by @look_ahead.
- % we can't get rid of it with \expandafter because we don't know how
+ % we can't get rid of it with \expandafter because we don't know how
% long #4 is.
}
% #1 - THE_MACRO
% #2 - ARG_RESULT
-% #3 discards the res of the conditional in @add_segment, and @is_fi ends the
+% #3 discards the res of the conditional in @add_segment, and @is_fi ends the
% conditional.
@gdef@call_the_macro#1#2!#3@fi{@is_fi #1{#2}}
@@ -8664,7 +8664,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% for reading the argument (slightly different in the two cases). Then,
% to read the argument, in the whole-line case, it then calls the regular
% \parsearg MAC; in the lbrace case, it calls \passargtomacro MAC.
-%
+%
\def\braceorline#1{\let\macnamexxx=#1\futurelet\nchar\braceorlinexxx}
\def\braceorlinexxx{%
\ifx\nchar\bgroup
@@ -8787,7 +8787,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% Used so that the @top node doesn't have to be wrapped in an @ifnottex
% conditional.
-% \doignore goes to more effort to skip nested conditionals but we don't need
+% \doignore goes to more effort to skip nested conditionals but we don't need
% that here.
\def\omittopnode{%
\ifx\lastnode\wordTop
@@ -8869,7 +8869,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
% automatically in xrefs, if the third arg is not explicitly specified.
% This was provided as a "secret" @set xref-automatic-section-title
% variable, now it's official.
-%
+%
\parseargdef\xrefautomaticsectiontitle{%
\def\temp{#1}%
\ifx\temp\onword
@@ -8885,7 +8885,7 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\fi\fi
}
-%
+%
% @xref, @pxref, and @ref generate cross-references. For \xrefX, #1 is
% the node name, #2 the name of the Info cross-reference, #3 the printed
% node name, #4 the name of the Info file, #5 the name of the printed
@@ -9083,20 +9083,20 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\space\putwordpage\tie\refx{#1-pg}}
% Output a cross-manual xref to #1. Used just above (twice).
-%
+%
% Only include the text "Section ``foo'' in" if the foo is neither
% missing or Top. Thus, @xref{,,,foo,The Foo Manual} outputs simply
% "see The Foo Manual", the idea being to refer to the whole manual.
-%
+%
% But, this being TeX, we can't easily compare our node name against the
% string "Top" while ignoring the possible spaces before and after in
% the input. By adding the arbitrary 7sp below, we make it much less
% likely that a real node name would have the same width as "Top" (e.g.,
% in a monospaced font). Hopefully it will never happen in practice.
-%
+%
% For the same basic reason, we retypeset the "Top" at every
% reference, since the current font is indeterminate.
-%
+%
\def\crossmanualxref#1{%
\setbox\toprefbox = \hbox{Top\kern7sp}%
\setbox2 = \hbox{\ignorespaces \printedrefname \unskip \kern7sp}%
@@ -9188,9 +9188,9 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\fi
}
-% This is the macro invoked by entries in the aux file. Define a control
-% sequence for a cross-reference target (we prepend XR to the control sequence
-% name to avoid collisions). The value is the page number. If this is a float
+% This is the macro invoked by entries in the aux file. Define a control
+% sequence for a cross-reference target (we prepend XR to the control sequence
+% name to avoid collisions). The value is the page number. If this is a
float
% type, we have more work to do.
%
\def\xrdef#1#2{%
@@ -9206,10 +9206,10 @@ might help (with 'rm \jobname.?? \jobname.??s')%
\bgroup
\expandafter\gdef\csname XR\safexrefname\endcsname{#2}%
\egroup
- % We put the \gdef inside a group to avoid the definitions building up on
- % TeX's save stack, which can cause it to run out of space for aux files with
+ % We put the \gdef inside a group to avoid the definitions building up on
+ % TeX's save stack, which can cause it to run out of space for aux files
with
% thousands of lines. \gdef doesn't use the save stack, but \csname does
- % when it defines an unknown control sequence as \relax.
+ % when it defines an unknown control sequence as \relax.
%
% Was that xref control sequence that we just defined for a float?
\expandafter\iffloat\csname XR\safexrefname\endcsname
@@ -10406,7 +10406,7 @@ directory should work if nowhere else does.}
\uppercase{.}
\endgroup
\else
- \errhelp = \EMsimple
+ \errhelp = \EMsimple
\errmessage{Unicode character U+#1 not supported, sorry}%
\fi
\else
@@ -10439,7 +10439,7 @@ directory should work if nowhere else does.}
\countUTFz = "#1\relax
\begingroup
\parseXMLCharref
-
+
% Give \u8:... its definition. The sequence of seven \expandafter's
% expands after the \gdef three times, e.g.
%
@@ -10451,7 +10451,7 @@ directory should work if nowhere else does.}
\expandafter\expandafter
\expandafter\expandafter
\expandafter\gdef \UTFviiiTmp{#2}%
- %
+ %
\expandafter\ifx\csname uni:#1\endcsname \relax \else
\message{Internal error, already defined: #1}%
\fi
@@ -10490,7 +10490,7 @@ directory should work if nowhere else does.}
\divide\countUTFz by 64
\countUTFy = \countUTFz % Save to be the future value of \countUTFz.
\multiply\countUTFz by 64
-
+
% \countUTFz is now \countUTFx with the last 5 bits cleared. Subtract
% in order to get the last five bits.
\advance\countUTFx by -\countUTFz
@@ -10525,7 +10525,7 @@ directory should work if nowhere else does.}
% U+0080..U+00FF =
https://en.wikipedia.org/wiki/Latin-1_Supplement_(Unicode_block)
% U+0100..U+017F = https://en.wikipedia.org/wiki/Latin_Extended-A
% U+0180..U+024F = https://en.wikipedia.org/wiki/Latin_Extended-B
-%
+%
% Many of our renditions are less than wonderful, and all the missing
% characters are available somewhere. Loading the necessary fonts
% awaits user request. We can't truly support Unicode without
@@ -11770,7 +11770,7 @@ directory should work if nowhere else does.}
\def\texinfochars{%
\let< = \activeless
\let> = \activegtr
- \let~ = \activetilde
+ \let~ = \activetilde
\let^ = \activehat
\setregularquotes
\let\b = \strong
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 6 +
NEWS | 6 +-
README | 8 +-
awklib/ChangeLog | 4 +
awklib/Makefile.am | 4 +-
awklib/Makefile.in | 4 +-
build-aux/ChangeLog | 4 +
build-aux/texinfo.tex | 190 +-
doc/ChangeLog | 8 +
doc/Makefile.am | 8 +-
doc/Makefile.in | 8 +-
doc/gawk.info | 7144 ++++----
doc/gawk.texi | 1174 +-
doc/gawktexi.in | 47551 ------------------------------------------------
doc/sidebar.awk | 67 -
doc/texinfo.tex | 190 +-
16 files changed, 3809 insertions(+), 52567 deletions(-)
delete mode 100644 doc/gawktexi.in
delete mode 100644 doc/sidebar.awk
hooks/post-receive
--
gawk
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Arnold Robbins <=