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Re: [bug-gawk] zerofile function

From: Manuel Collado
Subject: Re: [bug-gawk] zerofile function
Date: Fri, 17 May 2013 10:37:56 +0200
User-agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/17.0 Thunderbird/17.0 
First af all, some advice:

- Please don't top-post.
- Please respond to the bug-gawk list instead of or in addition to my personal e-mail address. 
- Please post just plain text and not HTML.
- Please quote the relevant parts of the original message, and not the whole stuff.
(Disclaimer: I'm quoting the full thread so others can see the whole stuff you sent just to my personal address)
Short answer: Your original code (at the end of this long post) is correct. Don't spoil it.
And now, look below to see my responses to some specific parts of your messages. 


El 16/05/2013 23:32, david ward escribió:

Sorry to exhaust you with my mistakes but correcting all references TO ARGV
to ARGC I still get the same errors. My main programming language is C++
hence the mistake. I have manage to find some errors in the functions
presented in the manual so please don't dismiss me too lightly


Don't worry. We are always willing to help interested people.
But, your original code is correct, so don't try to amend it. Doing so just makes things worse. 



On Thu, May 16, 2013 at 10:09 PM, david ward <address@hidden> wrote:


/gawk/awkscripts-> gawk -f  ./zerofile.awk  -f ./zerofile_funct.awk  -f
./checkzero.awk ./tee2  ./empty  ./tee3   ./empty2
gawk: ./zerofile.awk:18:              zerofile(ARGC[Argind], Argind) # get
syntax error for ARGV[Argind]
gawk: ./zerofile.awk:18:                                  ^ use of
non-array as array

gawk: ./zerofile_funct.awk:2: function zerofile(ARGC[Argind], Argind )
gawk: ./zerofile_funct.awk:2:                       ^ syntax error
gawk: ./zerofile_funct.awk:2: error: function `zerofile': can't use
special variable `ARGC' as a function parameter
~/gawk/awkscripts->
ARGC is a scalar variable (the number or arguments), ARGV is the array of arguments. So ARGV[x]is correct, but ARGC[x] doesn't makes sense.
In addition, ARGC is a special variable, so you can't use this name for a formal argument of a function. 



On Thu, May 16, 2013 at 10:06 PM, david ward <address@hidden> wrote:


Noticed that I did not make changes to the files correctly. Making these
corrections does not alter the error message:


As said, making such corrections makes the things worse.



#!/usr/bin/gawk -f
# All known awk implementations silently skip over zero-length files.
This is a by-product of awk's implicit
# read-a-record-and-match-against-the-rules loop:
#  when 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
data file, WITHOUT executing any
# user-level awk program code.
# Using gawk's ARGIND variable , it is possible to detect when an empty
data file
# has been skipped.

      # zerofile.awk --- library file to process empty input files


      BEGIN { Argind = 0 }

      ARGIND > Argind + 1 {

          for (Argind++; Argind < ARGIND; Argind++)
              zerofile(ARGC[Argind], Argind) # get syntax error for
ARGV[Argind]


      }

      ARGIND != Argind { Argind = ARGIND }

      END {
          d = ARGV[Argind]
          if (ARGIND > Argind)
              for (Argind++; Argind <= ARGIND; Argind++)
                   zerofile(ARG[Argind], Argind)


      }
#!/usr/bin/gawk -f
function zerofile(ARGC[Argind], Argind )
{
    print ARGIND,Argind, ARGV[Argind]

}
#!/usr/bin/gawk -f
    {print}



On Thu, May 16, 2013 at 9:52 PM, david ward <address@hidden> wrote:


Doesn't work  with gawk 4.0.2 on Ubuntu 12.04
removing the assignment to v in the source code I get


See the previous comment



1037  16/05/13 21:45:45 history
~/gawk/awkscripts-> gawk -f  ./zerofile.awk  -f ./zerofile_funct.awk  -f
./checkzero.awk ./tee2  ./empty  ./tee3   ./empty2
gawk: ./zerofile_funct.awk:2: function zerofile(ARGC{Argind], Argind )
gawk: ./zerofile_funct.awk:2:                       ^ syntax error
gawk: ./zerofile_funct.awk:2: error: function `zerofile': can't use
special variable `ARGC' as a function parameter
~/gawk/awkscripts->
#!/usr/bin/gawk -f
# All known awk implementations silently skip over zero-length files.
This is a by-product of awk's implicit
# read-a-record-and-match-against-the-rules loop:
#  when 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
data file, WITHOUT executing any
# user-level awk program code.
# Using gawk's ARGIND variable , it is possible to detect when an empty
data file
# has been skipped.

      # zerofile.awk --- library file to process empty input files


      BEGIN { Argind = 0 }

      ARGIND > Argind + 1 {
           # v = ARGV[Argind]

          for (Argind++; Argind < ARGIND; Argind++)
              zerofile(a, Argind) # get syntax error for ARGV[Argind]
submitted bug report apparently works ok in
                                  # in 4.0.1 on windows XP


      }

      ARGIND != Argind { Argind = ARGIND }

      END {
          d = ARGV[Argind]
          if (ARGIND > Argind)
              for (Argind++; Argind <= ARGIND; Argind++)
                  zerofile(d, Argind)

      }
  #!/usr/bin/gawk -f
function zerofile(ARGC{Argind], Argind )
{
    print ARGIND,Argind, ARGV[Argind]

}



On Thu, May 16, 2013 at 3:42 PM, Manuel Collado <address@hidden>wrote:


El 16/05/2013 14:23, david ward escribió:

  I don't know if this a bug or not but I get a syntax error when when

trying to pass ARGC[Argind] to zerofile. gawk version: 4.0.2 OS:
Ubuntu 12.4

#!/usr/bin/gawk -f
# All known awk implementations silently skip over zero-length files.
This is a by-product of awk's implicit
# read-a-record-and-match-**against-the-rules loop:
#  when 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
data file, WITHOUT executing any
# user-level awk program code.
# Using gawk's ARGIND variable , it is possible to detect when an empty
data file
# has been skipped.

       # zerofile.awk --- library file to process empty input files


       BEGIN { Argind = 0 }

       ARGIND > Argind + 1 {
             v = ARGV[Argind]
           for (Argind++; Argind < ARGIND; Argind++)
               zerofile(a, Argind) # get syntax error for ARGV[Argind]

       }

       ARGIND != Argind { Argind = ARGIND }

       END {
           d = ARGV[Argind]
           if (ARGIND > Argind)
               for (Argind++; Argind <= ARGIND; Argind++)
                   zerofile(d, Argind)

       }
   my zerofile function
#!/usr/bin/gawk -f
function zerofile(a, Argind )
{
     print ARGIND,Argind, ARGV[Argind]

}
I wrote this to understand  how the post increment operator  took
effect
on the parameters



Works Ok with GNU Awk 4.0.1 on Windows XP. No syntax errors, gives
expected output.


Tested also with GAWK 4.0.2. Same (good) results.

Regards.
--
Manuel Collado - http://lml.ls.fi.upm.es/~mcollado
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