#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use IPC::Open3;
require Tk::ROText;

$|=1;

my $mw = new MainWindow;

my $entry=$mw->Entry(-width => 80)->pack;

$mw->Button(-text => 'Execute',
        -command => \&send_to_shell)->pack;

my $textwin =$mw->Scrolled('ROText',
       -width => 80,
       -bg =>'white',    
       -height => 24,
       )->pack;

$textwin->tagConfigure( 'err', -foreground => 'red' );

my $pid = open3( \*IN, \*OUT, \*ERR, '/bin/bash' ) or warn "$!\n";

$mw->fileevent( \*OUT, readable => \&read_stdout );
$mw->fileevent( \*ERR, readable => \&read_stderr );

$entry->bind('<Return>',[\&send_to_shell]);
$entry->focus;

MainLoop;

sub read_stdout {
    
    if( sysread( OUT, my $buffer, 1024 ) > 0 ){
       $textwin->insert( 'end', $buffer );
       $textwin->see('end');
      }
}

sub read_stderr {
    if( sysread(ERR, my $buffer, 1024 ) > 0 ){
      $textwin->insert( 'end', $buffer, 'err' );
      $textwin->see('end');
    }
}

    
sub send_to_shell {
   my $cmd= $entry->get();
   print IN "$cmd\n";
}