Sometimes there is a need to capture the output from another perl program and display it in your program. Especially when you use Pterl/Tk and want to invoke a perl program to do something, you want to capture the standard output of the other program “in real time.” Here is a way to do it:
program 1 (call it a): 

#!/usr/local/bin/perl -w 
$|=1; #flush the standard output

use strict;

sub printMsg {
   foreach (0.. 10) {
       sleep(1);
       print "$_\n";
   }
}

printMsg();
#### end of program

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program 2 
#!/usr/local/bin/perl -w
open(FD,"a|");
while (<FD>) {
  print $_;
}

[download]
Idea is to use a pipe. Any comments?

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Re: capturing output from another perl program
by Zaxo (Archbishop) on Aug 21, 2004 at 00:02 UTC

    That's one of my favorite ways to do it. You may want to adopt perl 5.6+ notation for piped open, use a lexical file handle, and keep the child pid, 

    {
    my $cpid = open my $fd, '-|', 'a' or die $!;
    print while <$fd>;
}

    [download]
    The three-arg form of open is preferred because it separates the open mode from the file name, and it can take modifiers like ':raw' to activate IO layers, remove the need for binmode, etc.

    Your app could have done this with backticks, but not so well.

    After Compline,
    Zaxo

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[d/l]
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