jeanluca has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks

I have this external program that when started requires some input. For example, I could do something like
#! /usr/bin/perl

open OUT,"| ./progX" or die ;
print OUT "X\n\n1\n2\n\n\n" ;
close OUT ;

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This works just fine.
However, before progX terminates it writes some useful information to STDOUT. Normally I would do something like
open OUT,"| ./progX > output" or die ;

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 Than I would open the 'output' file and read the content.
This works great (as long as I have write permissions so I can create the output file).
For some reason this approach doesn't feel right. So is there a better way to catch the output directly in my perl program ?

ThnX
LuCa

Replies are listed 'Best First'.
Re: need to read/write from/to an external program
by davorg (Chancellor) on Feb 21, 2007 at 15:31 UTC
[reply]
Re: need to read/write from/to an external program
by jeanluca (Deacon) on Feb 21, 2007 at 16:08 UTC
    thnx davorg

    that works great!!.
    I only don't understand how I should use the *Reader and *Writer together with 'use warnings' and 'use strict'.
    For now (without strict and warnings) I have 
    #! /usr/bin/perl
use FileHandle;
use IPC::Open2;

$pid = open2(*Reader, *Writer, "./progX" );
print Writer "X\n\n1\n2\n\n\n" ;

{ local $/ ;
  $inp = <Reader> ;
}
# or @inp = <Reader>
close Writer, Reader ;

print "Reader: $inp\n" ;

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[reply]
[d/l]

      You have the syntax for close wrong. It takes just one argument, so Reader is parsed as a bareword and not a filehandle. Simply: 

      close Writer;
close Reader;

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      ... instead of trying to close both with one statement.

      print "Just another Perl ${\(trickster and hacker)},"
      The Sidhekin proves Sidhe did it!

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