[gawk-diffs] [SCM] gawk branch, gawk-4.2-stable, updated. gawk-4.1.0-2991-g1bc2871

[Arnold Robbins]

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- Log -----------------------------------------------------------------
http://git.sv.gnu.org/cgit/gawk.git/commit/?id=1bc2871bbe4ae6b99fd1862a412440672846bc05

commit 1bc2871bbe4ae6b99fd1862a412440672846bc05
Author: Arnold D. Robbins <address@hidden>
Date:   Wed Jul 25 20:39:39 2018 +0300

    Add example on buffering and ptys to the doc.

diff --git a/doc/ChangeLog b/doc/ChangeLog
index 3f05800..1c21510 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,8 @@
+2018-07-25         Arnold D. Robbins     <address@hidden>
+
+       * gawktexi.in (Two-way I/O): Add a nice example on buffering
+       and ptys from Andrew Schorr.
+
 2018-07-10         Arnold D. Robbins     <address@hidden>
 
        * gawktexi.in (Control Letters): Add a note about output of NaN and
diff --git a/doc/gawk.info b/doc/gawk.info
index dc1aa07..807fe8a 100644
--- a/doc/gawk.info
+++ b/doc/gawk.info
@@ -20429,6 +20429,46 @@ driver and not passed through.
      deadlock; careful programming and knowledge of the behavior of the
      coprocess are required.
 
+   The following example, due to Andrew Schorr, demonstrates how using
+ptys can help deal with buffering deadlocks.
+
+   Suppose 'gawk' were unable to add numbers.  You could use a coprocess
+to do it.  Here's an exceedingly simple program written for that
+purpose:
+
+     $ 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;
+     }
+     $ cc -O add.c -o add      Compile the program
+
+   You could then write an exceedingly simple 'gawk' program to add
+numbers by passing them to the coprocess:
+
+     $ echo 1 2 |
+     > gawk -v cmd=./add '{ print |& cmd; cmd |& getline x; print x }'
+
+   And it would deadlock, because 'add.c' fails to call
+'setlinebuf(stdout)'.  The 'add' program freezes.
+
+   Now try instead:
+
+     $ echo 1 2 |
+     > gawk -v cmd=add 'BEGIN { PROCINFO[cmd, "pty"] = 1 }
+     >                  { print |& cmd; cmd |& getline x; print x }'
+     -| 3
+
+   By using a pty, '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!
+
    ---------- Footnotes ----------
 
    (1) Michael Brennan suggests the use of 'rand()' to generate unique
@@ -36419,223 +36459,223 @@ Ref: Controlling Array Traversal-Footnote-1820186
 Node: Array Sorting Functions820304
 Ref: Array Sorting Functions-Footnote-1825395
 Node: Two-way I/O825591
-Ref: Two-way I/O-Footnote-1832143
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-Ref: Old Extension Problems-Footnote-11235335
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-Ref: Basic High Level-Footnote-11249788
-Node: Basic Data Typing1249973
-Node: Glossary1253301
-Node: Copying1285139
-Node: GNU Free Documentation License1322682
-Node: Index1347802
+Ref: Two-way I/O-Footnote-1833311
+Ref: Two-way I/O-Footnote-2833498
+Node: TCP/IP Networking833580
+Node: Profiling836698
+Ref: Profiling-Footnote-1845370
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+Node: Internationalization847537
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+Ref: Explaining gettext-Footnote-1855596
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+Ref: Programmer i18n-Footnote-1860895
+Node: Translator i18n860944
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+Ref: String Extraction-Footnote-1862870
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+Ref: I18N Example-Footnote-1871131
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+Node: I18N Summary871849
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+Node: Debugging874213
+Node: Debugging Concepts874654
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+Node: Readline Support910875
+Node: Limitations911771
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+Node: Arbitrary Precision Arithmetic915159
+Node: Computer Arithmetic916644
+Ref: table-numeric-ranges920410
+Ref: table-floating-point-ranges920903
+Ref: Computer Arithmetic-Footnote-1921561
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+Ref: table-ieee-formats924934
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+Ref: FP Math Caution-Footnote-1928432
+Node: Inexactness of computations928801
+Node: Inexact representation929761
+Node: Comparing FP Values931121
+Node: Errors accumulate932203
+Node: Getting Accuracy933636
+Node: Try To Round936346
+Node: Setting precision937245
+Ref: table-predefined-precision-strings937942
+Node: Setting the rounding mode939772
+Ref: table-gawk-rounding-modes940146
+Ref: Setting the rounding mode-Footnote-1944077
+Node: Arbitrary Precision Integers944256
+Ref: Arbitrary Precision Integers-Footnote-1947431
+Node: Checking for MPFR947580
+Node: POSIX Floating Point Problems949054
+Ref: POSIX Floating Point Problems-Footnote-1953339
+Node: Floating point summary953377
+Node: Dynamic Extensions955567
+Node: Extension Intro957120
+Node: Plugin License958386
+Node: Extension Mechanism Outline959183
+Ref: figure-load-extension959622
+Ref: figure-register-new-function961187
+Ref: figure-call-new-function962279
+Node: Extension API Description964341
+Node: Extension API Functions Introduction965983
+Node: General Data Types971523
+Ref: General Data Types-Footnote-1979884
+Node: Memory Allocation Functions980183
+Ref: Memory Allocation Functions-Footnote-1984393
+Node: Constructor Functions984492
+Node: Registration Functions988078
+Node: Extension Functions988763
+Node: Exit Callback Functions993978
+Node: Extension Version String995228
+Node: Input Parsers995891
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+Ref: Printing Messages-Footnote-11016560
+Node: Updating ERRNO1016713
+Node: Requesting Values1017452
+Ref: table-value-types-returned1018189
+Node: Accessing Parameters1019125
+Node: Symbol Table Access1020360
+Node: Symbol table by name1020872
+Node: Symbol table by cookie1022661
+Ref: Symbol table by cookie-Footnote-11026846
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+Ref: Array Manipulation-Footnote-11031690
+Node: Array Data Types1031727
+Ref: Array Data Types-Footnote-11034385
+Node: Array Functions1034477
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+Node: Extension API Variables1053551
+Node: Extension Versioning1054262
+Ref: gawk-api-version1054691
+Node: Extension GMP/MPFR Versioning1056422
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+Node: Non-Unix Installation1178258
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+Ref: figure-process-flow1247655
+Ref: Basic High Level-Footnote-11250956
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+Node: Glossary1254469
+Node: Copying1286307
+Node: GNU Free Documentation License1323850
+Node: Index1348970
 
 End Tag Table
diff --git a/doc/gawk.texi b/doc/gawk.texi
index 3b7c2bf..675985e 100644
--- a/doc/gawk.texi
+++ b/doc/gawk.texi
@@ -28652,6 +28652,53 @@ they've already written.  There is no workaround for 
deadlock; careful
 programming and knowledge of the behavior of the coprocess are required.
 @end quotation
 
address@hidden 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: 
+
address@hidden
+$ @kbd{cat add.c}
+#include <stdio.h> 
+
+int 
+main(void) 
address@hidden 
+    int x, y; 
+    while (scanf("%d %d", & x, & y) == 2) 
+        printf("%d\n", x + y); 
+    return 0; 
address@hidden 
+$ @kbd{cc -O add.c -o add}     @ii{Compile the program}
address@hidden example
+
+You could then write an exceedingly simple @command{gawk} program
+to add numbers by passing them to the coprocess:
+
address@hidden
+$ @kbd{echo 1 2 |}
+> @kbd{gawk -v cmd=./add '@{ print |& cmd; cmd |& getline x; print x @}'}
address@hidden example
+
+And it would deadlock, because @file{add.c} fails to call
address@hidden(stdout)}. The @command{add} program freezes. 
+
+Now try instead: 
+
address@hidden
+$ @kbd{echo 1 2 |}
+> @kbd{gawk -v cmd=add 'BEGIN @{ PROCINFO[cmd, "pty"] = 1 @}}
+> @kbd{                 @{ print |& cmd; cmd |& getline x; print x @}'}
address@hidden 3 
address@hidden 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, network programming
diff --git a/doc/gawktexi.in b/doc/gawktexi.in
index 8c4cb89..795c5c0 100644
--- a/doc/gawktexi.in
+++ b/doc/gawktexi.in
@@ -27665,6 +27665,53 @@ they've already written.  There is no workaround for 
deadlock; careful
 programming and knowledge of the behavior of the coprocess are required.
 @end quotation
 
address@hidden 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: 
+
address@hidden
+$ @kbd{cat add.c}
+#include <stdio.h> 
+
+int 
+main(void) 
address@hidden 
+    int x, y; 
+    while (scanf("%d %d", & x, & y) == 2) 
+        printf("%d\n", x + y); 
+    return 0; 
address@hidden 
+$ @kbd{cc -O add.c -o add}     @ii{Compile the program}
address@hidden example
+
+You could then write an exceedingly simple @command{gawk} program
+to add numbers by passing them to the coprocess:
+
address@hidden
+$ @kbd{echo 1 2 |}
+> @kbd{gawk -v cmd=./add '@{ print |& cmd; cmd |& getline x; print x @}'}
address@hidden example
+
+And it would deadlock, because @file{add.c} fails to call
address@hidden(stdout)}. The @command{add} program freezes. 
+
+Now try instead: 
+
address@hidden
+$ @kbd{echo 1 2 |}
+> @kbd{gawk -v cmd=add 'BEGIN @{ PROCINFO[cmd, "pty"] = 1 @}}
+> @kbd{                 @{ print |& cmd; cmd |& getline x; print x @}'}
address@hidden 3 
address@hidden 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, network programming

-----------------------------------------------------------------------

Summary of changes:
 doc/ChangeLog   |   5 +
 doc/gawk.info   | 476 ++++++++++++++++++++++++++++++--------------------------
 doc/gawk.texi   |  47 ++++++
 doc/gawktexi.in |  47 ++++++
 4 files changed, 357 insertions(+), 218 deletions(-)


hooks/post-receive
-- 
gawk