Re: [bug-gawk] Potential awk bug in comment line with combination # and ' characters.

[Aharon Robbins]

Hello. Re the below.

You are running into shell quoting issues and not awk issues.  When you
have a script of the form:

        awk 'line 1 ...
             line 2 ...
             ....
             line N'  data

The single quotes enclose the entire program, including the embedded
newlines, and turn it into a single argument.

Single quotes don't provide any mechansims for embedded single quotes. So
if you have

        awk '.....
             # '|' ...' 

You actually have two commands separated by a shell pipe.  The way to
verify this is to put the suspect program into a separate file, without the
leading and closing quotes, and run the file with awk -f prog.awk.  I
suspect that you will then get the behavior you expect.

Thanks,

Arnold

P.S. The current version of gawk is 4.0.1; you should upgrade, or get
your GNU/Linux vendor to do so.  Thanks.

> From: Dave <address@hidden>
> To: address@hidden
> Date: Sun, 24 Jun 2012 10:54:02 -0400
>
> TO: address@hidden
>
> From David M. Boulin
>      address@hidden
> Date: 6-24-2012
>
> Summary of suspected COMMENT LINE   awk bug:
>  1) Combinations with # followed by one or more "'" give errors or
> unpredictable
>       results as shown below. These include  # '   and     # '|'  ,    etc.
>
>  2) Note:from "info awk":   Definition of a comment:
>                       Comments  begin  with  the ???#??? character, and 
> continue
>                               until the end of the line.
>                       As far a I can tell there are no stated exemptions
>                        on what characters can be used in a comment line.
> ===============================================================================
> OS:           Linux 3.0.0-21-generic (i686)
> awk version:  GNU Awk 3.1.8
> C compiler:   GNU C Compiler version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3)
> Distribution: Ubuntu 11.10
> value of LC_ALL= null initially
> value of LC_ALL= C  No change to results posted below after setting this
> and
>                     re-executing the awk script file..
> ===============================================================================
>
>
>
> ===============================================================================
>  The AWK program is in a file called 'testit' which is executable
> (-rwxrw-r--):
>  It's contents followd:
>  awk '
> # Prog testit to demo a bug. Change comment line below and see NOTES for
> results:
> #  
>         { print "Hello World" }
>      ' datafile
>
> ===============================================================================
>
>
> ===============================================================================
> Contents of the datafile:
> $ cat datafile
> LineFromDataFile
> $ 
> ===============================================================================
>
>
> ===============================================================================
> By changing the 3rd line which initial consisting only of a pound sign
> #  to 
>  the following list of string examples, then execute via ./testit,  you
>  will get the results shown (some spaced deleted in error line for
> brevity).
>
> Content of
> third line:   Results                                 Comment
> ---------       -------                                       -------
> # Hi          Hello World                             As expected
> # " "         Hello World                             As expected
>
> #Use '|' blabla       ./testit:line 5:$' blabla\n\t{ print "Hello World" }\n':
> command not found
> # '|'         ./testit: line 5: $'\n\t{ print "Hello World" }\n ':
> command not found
> # '           ./testit: line 8: syntax error: unexpected end of file
> # ' '         No output - no reported errors
> # 'x'         Hello World  - no reported errors
> ===============================================================================
>
> From "info awk" page:
> BUG REPORTS
>        If you find a  bug  in  gawk,  please  send  electronic  mail
> to 
>         address@hidden 
>
> Hope this has been of some help. 
> I look forward to your reply,
>   Dave