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Old 03-28-2008, 02:11 AM   #1
sudhap85
LQ Newbie
 
Registered: Mar 2008
Posts: 3

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How to redirect the output of exec command output in perl?


In my code i want to redirect the o/p of exec to one file is it possible?


else {

if ($pid = fork) {

}

elsif (defined $pid) {

chdir $chdir if $chdir;

eval $extra if $extra;

exec $cmd or die "Unable to exec $cmd: $!\n";

} else {

die "Unable to fork: $!\n";

}

}


here $cmd am passing one processor cmd line args.so i want to preserve the o/p of that processor in to one file.

Can anyone help me?


sudha
 
Old 03-28-2008, 09:29 AM   #2
theNbomr
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Registered: Aug 2005
Distribution: OpenSuse, Fedora, Redhat, Debian
Posts: 5,395
Blog Entries: 2

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This small example should explain:
Code:
#! /bin/perl -w
use strict;

    # open a command with command's output piped back to us
    #
    open( DIR, "ls|" ) || die "No ls"; 
    while( <DIR> ){      # read command's output from the pipe
        print $_;        # do something with what we read back from the proces
    } 
    close DIR;         # be done
    exit;
You can use the same technique to pipe standard input into the command (but not both input & output).
No explicit fork() necessary. See also, readpipe.

--- rod.

Last edited by theNbomr; 03-28-2008 at 09:30 AM.
 
Old 03-28-2008, 04:35 PM   #3
prad77
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Registered: Mar 2008
Posts: 101

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The output of a command is directed to STDOUT. we can redirect this to a file for our use.

To read both a command's STDOUT and its STDERR separately, it's easiest and
safest to redirect them separately to files, and then read from those files
when the program is done: system("program args 1>/tmp/program.stdout 2>/tmp/program.stderr");

Gentoo

Last edited by prad77; 04-17-2008 at 03:29 AM.
 
Old 08-28-2009, 03:35 PM   #4
guivho
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Registered: Jan 2009
Posts: 3

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This is probably far too late to be helpful, but I bumped into this thread just now. You could add the desired redirection to your 'exec' command, e.g.:

exec "$cmd 1>stdout.text 2>stderr.txt" or die "Unable to exec $cmd: $!\n";

Hope this helps,

guivho
 
  


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