use Tk 800.000;
use strict;
use Tk::LineNumberText;
use IPC::Run qw(start finish);

my $MW = MainWindow->new;

my $cmd_output = $MW->LineNumberText(-widget=>'ROText')->pack(-fill=>'both',-expand=>1);

my $harness = start(['cmd.exe','/C','echo hello'] , '<' ,\undef , ">pipe", \*OUT,debug=>999) || die $!;

$MW->fileevent(\*OUT,'readable',[\&mycb,\*OUT,$harness]);

MainLoop;


sub mycb {
  $cmd_output->insert('end',"Callback called\n");
  my ($fh, $harness) = @_;
  my $n = sysread( $fh, my $buf, 8192 );

  if($n) {
     $cmd_output->insert('end',$buf);
     return;
  }

  $cmd_output->insert('end',"WARNING: $!") if not defined $n;
  $MW->fileevent( $fh, 'readable', '' );
  close $fh;
  $harness->finish;
}