A timer calling sysread at a fast interval will not block.... the <> operator might. Sysread will try to read the pipe every 10 ms (or so), and if nothing is there, will just let the timer go on to the next round. Tk will remain responsive.

I think its easier for people to switch to linux, than to figure out hacks to make win32 work. :-)

A timer calling sysread at a fast interval will not block

Why do you say sysread won't block?

than to figure out hacks to make win32 work. :-)

Win32 works fine. It's fighting Perl on Win32 that requires effort.

Why do you say sysread won't block?

This script does it, by adding the O_NONBLOCK flag to the piped open. top is set to give output every 10 secs, yet the Tk gui is still running fine.

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = MainWindow->new(-background => 'gray50');

my $text = $mw->Scrolled('Text')->pack();

my $pid;
my $startb = $mw->Button( -text => 'Start',
                -command=> \&work,
                 )->pack();

my $count = 0;
my $label = $mw->Label(-textvariable=>\$count)->pack();

my $testtimer = $mw->repeat(500,
                   sub { $count++}  );

my $stopb = $mw->Button( -text => 'Exit',
                -command=>sub{
                 kill 9,$pid;
                 exit;
              },
                 )->pack();

MainLoop;
#####################################

sub work{

$startb->configure(-state=>'disabled');

use Fcntl;
   #long 10 second delay between outputs
  $pid = open (my $fh, "top -b -d 10 |" ) or warn "$!\n";

  fcntl($fh, F_SETFL, O_NONBLOCK) || die "$!\n"; 
# Set the non-block flags  

   my $repeater; 
   $repeater = $mw->repeat(10,
          sub {
                if(my $bytes = sysread( $fh, my $buf, 1024)){;
            $text->insert('end',$buf);    
                $text->see('end');         
          }
      }
     );             
}
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