comment on

Update: Simplified problem temporarily by removing requirement of stderr

A bucket-load of XP to the monk that can make this work:

use strict; $|++;

if( $ARGV[0] eq 'child' )
{
  sleep 1; print STDOUT "stdout1\n";
  sleep 1; print STDOUT "stdout2\n";
  sleep 1; print STDOUT "stdout3\n";
  sleep 1; print STDOUT "stdout4\n";
  exit;
}

use Tk;
use Tk::ROText;
my $mw = MainWindow->new;
my $text = $mw->ROText()->pack( -fill => 'both', -expand => 1 );

use IO::Handle;
my $stdout = IO::Handle->new();

my $pid = open( $stdout, "$0 child |" ) || die;
$stdout->autoflush( 1 );

$mw->fileevent( $stdout, readable => \&read_stdout );

MainLoop;


sub read_stdout
{
  print "read_stdout()\n";
  my $num = $stdout->sysread( my $buffer, 1024 );
  print "sysread() got $num bytes:\n[$buffer]\n";
  $text->insert( 'end', $buffer );
}
[download]

Original code:

use strict; $|++;

if( $ARGV[0] eq 'child' )
{
  sleep 1; print STDOUT "stdout1\n";
  sleep 1; print STDERR "stderr1\n";
  sleep 1; print STDOUT "stdout2\n";
  sleep 1; print STDERR "stderr2\n";
  exit;
}

use Tk;
use Tk::ROText;
my $mw = MainWindow->new;
my $text = $mw->ROText()->pack( -fill => 'both', -expand => 1 );
$text->tagConfigure( 'red', -foreground => 'red' );

use IO::Handle;
my $stdin = IO::Handle->new();
my $stdout = IO::Handle->new();
my $stderr = IO::Handle->new();

use IPC::Open3;
my $pid = open3( $stdin, $stdout, $stderr, "$0 child" ) || die;
$stdin->close;
$stdout->autoflush( 1 );
$stderr->autoflush( 1 );

$mw->fileevent( $stdout, readable => \&read_stdout );
$mw->fileevent( $stderr, readable => \&read_stderr );

MainLoop;


sub read_stdout
{
  print "read_stdout()\n";
  my $num = $stdout->sysread( my $buffer, 1024 );
  print "sysread() got $num bytes:\n[$buffer]\n";
  $text->insert( 'end', $buffer );
}

sub read_stderr
{
  print "read_stderr()\n";
  my $num = $stderr->sysread( my $buffer, 1024 );
  print "sysread() got $num bytes:\n[$buffer]\n";
  $text->insert( 'end', $buffer, 'red' );
}
[download]

This is a simplified exmaple of what i want to achieve, which basically is to see the stdout ~~and stderr~~ of a program in a Tk widget. Note there are numerous problems here, such as being able to perform a non-blocking read (on win32!), ~~avoiding deadlock between stdout and stderr~~, and keeping the MainLoop running. You can assume the child is never going to need stdin, and will run for a long time (ie, a daemon).

- ><iper

use japh; print;
[download]

In reply to capture output of a daemon in a tk widget on win32 by xiper

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