Worth reading are Bidirectional Communication with Another Process

Bidirectional Communication with Yourself

Also worth investigating are IPC::Open3::Simple and/or IPC::Run3

#!/usr/bin/perl
use warnings; 
use strict;
use threads;
use threads::shared;

# original idea from BrowserUK at  
# http://perlmonks.org?node_id=493754

for my $file ( map{ glob $_ } @ARGV ) {
  open my $fh, '<', $file or warn "$file : $!" and next;
  printf "From main: %s", scalar <$fh> for 1 .. 10;
  printf "Fileno:%d\n", fileno $fh;
  threads->create( \&thread, fileno( $fh ) )->detach;
  printf 'paused:';<STDIN>;
}


sub thread{
my( $fileno ) = @_;
open my $fh, "<&=$fileno" or warn $! and die;
printf "%d:%s", threads->self->tid, $_ while defined( $_ = <$fh> );
close $fh;
}
[download]

Hm. You want to spawn a thread, execute an external process from within that thread and then leave that thread doing nothing whilst your main thread reads from the process. And once the external process finishes, have the thread terminate.

Why? Why complicate things by having the thread start the process and then do nothing, if you want the main thread to read the data? Forget the thread, it is achieving nothing but complication. Just run the external process from the main thread in any of the normal ways backticks, piped open IPC::open.

Well, the idea is that the external process generates data and the main thread reads this data simultaneously. I might be thinking too complicated when considering an empty thread, but how could I do it?

Some pseudo to illustrate my point:

-MAIN: Create new external process
-----> EXTERNAL: <generates data>
MAIN: <while data is being generated>
MAIN: do something with it.
-----> EXTERNAL: <exits>
MAIN: <no more data>
MAIN: <exits>

Q: If you were to do this with sharing the streams "STDOUT" and "STDERR", how would you?

If you need the output from both stdout and stderr via a single stream:

#main

my $kid = open my $fh, "theExternalProcess 2>&1 |" or die $!;
while( <$fh> ) {
    ## Read the output from theExternalProcess
}
## You'll end up here when the kid goes away
[download]

If you need to keep stdout and stderr separate, then see IPC::Open3 or IPC::Run.

---

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