in reply to Re^3: Running a C program from Perl
in thread Running a C program from Perl

Hmmm,

I think it looks like I and to some extent you, are barking up the wrong tree (well on linux & AIX anyway) - consider the following behaviour exhibited by both Linux 2.6.28-11-generic and AIX 5.3: 

user@unforgiven:~$ egrepa
bash: egrepa: command not found
user@unforgiven:~$ egrepa >/dev/null
bash: egrepa: command not found
user@unforgiven:~$ egrepa >/dev/null 2>&1
user@unforgiven:~$ perl -e '$res = `egrepa 2>&1`; print $res'
user@unforgiven:~$

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Personally, I would expect the one-liner to print bash: egrepa: command not found - as it does if entered from command line - but doesn't.

If, however, as you suggest, a valid command is used with invalid opts, then the re-direction works as expected and the error is seen (on both platforms).

A user level that continues to overstate my experience :-))

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Re^5: Running a C program from Perl
by ikegami (Patriarch) on May 27, 2009 at 13:45 UTC

    Personally, I would expect the one-liner to print bash: egrepa: command not found - as it does if entered from command line - but doesn't.

    The shell was never invoked, so how can it display an error message? It's up to you to do your own error checking. 

    $ perl -e'$res = `egrepa 2>&1`; print "$?:$!\n"; print $res'
-1:No such file or directory
(( Perl tried to execute egrepa, couldn't, and returned an error.
   Perl doesn't output error messages for you. ))

$ perl -e'$res = `egrepa "" 2>&1`; print "$?:$!\n"; print $res'
32512:
sh: egrepa: command not found
(( Perl sees a shell command, and successfully executed the shell.
   The shell couldn't execute egrapa "", so it displayed and 
   returned an error. ))

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