How can get a filehandle for a Perl program's output?

Question

I have an encrypted file X1, I have a Perl program P1 that decrypts the X1. I am parsing the decrypted file using a Perl program p2.

X1--P1(decrypter) --> X2(plain text file) --p2(parser) --> parse output

My parser is based on XML::Parser. It can work with a filehandle to the decrypted file. Now I am getting the X2 and storing it in the file system and reading it in the P2 and parsing it. Is there way I can directly get the filehandle over the P1's output and use that filehandle in the P2 to parse it directly with out requiring a temporary file?

Answer 1

I'm not sure I entirely understand what you're getting at, but it sounds like you just want to use pipes. You can do that at the shell by redirecting one program's STDOUT to another's STDIN

$ foo | bar

Or you can do it within Perl by opening a pipe directly to another program.

See also IPC::Open3 if you need control over STDERR.

Answer 2

Why don't you just make your programs read from STDIN and write to STDOUT and pipe the commands together on the command line?

Answer 3

Say you're using very weak encryption:

#! /usr/bin/perl

print <<EOXML;
<doc>
  <elem attr="Hello, world!" />
</doc>
EOXML

Using open $fh, "-|", ... will create a pipe connected to the standard output of a child process:

#! /usr/bin/perl

use warnings;
use strict;

open my $decrypted, "-|", "./decrypt"
  or die "$0: open: $!";

while (<$decrypted>) {
  print "got: $_";
}

Output:

got: <doc>
got:   <elem attr="Hello, world!" />
got: </doc>