Re: Constructing STDIN for an external progam

[Ovid]

You want to read perlopentut. That should answer your questions. Specifically, I think you don't want system but instead want to open the external command with a leading pipe.

  open(PRINTER, "| lpr -Plp1")    || die "can't run lpr: $!";
  print PRINTER "stuff\n";
  close(PRINTER)                  || die "can't close lpr: $!";

However, you'll also want to read perlsec.

[Thelonius]

To build on Ovid's response, this should do what you want:

use strict;

my $cmdout = join " ", "perl printout.pl", @ARGV;
open OUT, "|$cmdout" or die "Cannot run $cmdout: $!\n";
while (<STDIN>) {
  s/essage/assage/sg;
  print OUT $_ or die "Error writing to $cmdout: $!\n";
}
close STDIN;
close OUT or die "Error closing $cmdout: $!\n";

[ikegami]

What if one of the args was two words? or it's? Your code won't work in those everyday situations, nevermind the security implications. You've invoking the shell without quoting and escaping your command. Use IPC::Open3, IPC::Run or IPC::Run3 to avoid having to do so.