There probably isn't a way to do it with one process. However, you can use one process to display whatever is sent through a socket (or named pipe ...) and just connect STDERR to the socket. E.g. here's the program to show the output:
#!perl -w
# usage: showerr.pl port
use IO::Socket;
use strict;

$| = 1;

$SIG{CHLD} = 'IGNORE';
my $localport = shift;
my $socklisten = IO::Socket::INET->new(LocalPort => $localport,
                                   Listen   => 2,
                                   Reuse   => 1,
                                   Proto    => 'tcp')
             or die "Cannot open sock on $localport: $!\n";

while (my $readport = $socklisten->accept) {
  print "Accepted new connection at ", scalar(localtime), "\n";
  print while <$readport>;
  print "Connection closed at ", scalar(localtime), "\n";
}

[download]
You can start that program independently or you could have the main program start it as below (in which case you would want to take out the outer while loop (replace while with if)):
#!perl -w
use IO::Socket;
use strict;

my $errsocket = "1999";

system("start showerr.pl 1999");
sleep(5);


*STDERR = IO::Socket::INET->new(
        Proto     => "tcp",
        PeerAddr  => "localhost:$errsocket",
        Timeout   => 30,
     )
     or die "cannot create socketremote: $!\n";



warn "This is a test";

print STDERR "testing\n";

sleep(10);

[download]
Note that there's an awkward sleep() here to wait an undetermined time for the listener to start. This race condition could be fixed, but it might be simpler to just run the showerr program independently first.

In reply to Re: Open a second DOS window by Thelonius
in thread Open a second DOS window by bart

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