Re: Re: Re: Handling program output in real time

[Anonymous Monk]

IO::Pty may help you (system dependent), if your monitor program can emulate a terminal (tty) the xfer program will give it line buffered output (which is what you want).

[dvergin]

I have stared very hard at the docs for IO::Pty and I can't dope out how to use it here. No doubt this is in part because I don't understand what is meant by: "the creation of a pseudo tty". (The topic is outside my normal field of Perl endeavors.)

Can you show how IO::Pty could be used to modify the second program in the OP (the program with PIPE1 in it) so that it would process the output from blackbox.pl in real time (leaving blackbox.pl untouched)?

Regarding the "system dependent" issue, I am running Linux 7.3 with the 2.4.20-20.7 kernel. I gather from the docs for IO::Tty that I sould be okay in that respect.

[Anonymous Monk]

Not pretty, and perhaps there are better ways, but this may get you started anyway:

#!/usr/bin/perl -w
use strict;
use IO::Pty;

my $pty = new IO::Pty;
my $slave = $pty->slave();

my $pid = fork();
die "Couldn't fork: $!" unless defined $pid;

if($pid){  # dup STDOUT to Pty and run external program:
    $pty->close_slave();
    open(STDOUT, ">&",$pty)||die $!;
    system "perl blackbox.pl";
    print "\cD"; # send ^d to end 

} else {    # this is your monitoring process
    $pty->make_slave_controlling_terminal();
    print "*$_" while <$slave>;
    exit;
}
__END__

Works for me on Linux.

[etcshadow]

There's also a snippet here that does this.