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

sudhap85 · 03-28-2008, 03:11 AM

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

theNbomr · 03-28-2008, 10:29 AM

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.

prad77 · 03-28-2008, 05:35 PM

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

guivho · 08-28-2009, 04:35 PM

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