You really should use fileevent to read any sort of filehandle with Tk. Here is an example to demonstrate. I used IPC3 instead of a piped open because it is just eaiser to deal with the separate STDOUT and STDERR from the pipe. If you want to use the piped open form, you may want to look into the 2>&1 bash shell trick to combine your stdout and stderr. IPC3 makes it easier to keep them separate. Also in this example, there is some additional error checking you need to do, like preventing the program from crashing if you kill the toplevel. I left that out for simplicity.

Here is the sender script for testing (also leftout ROText, but that is easy): 

#!/usr/bin/perl
use warnings;
use strict;
$| = 1;
my $count = 0;
while(1){
 $count++;
 print "$count\n";
 warn "\tuh oh warning $count\n";
 sleep 1;
}

[download]

And here is the IPC3-Tk example. 

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

my $mw = new MainWindow;
$mw->geometry("600x400");

$mw->Button(-text => "See STDERR", -command => \&do_Toplevel)->pack();

my $tout = $mw->Scrolled(
    'Text',
    -foreground => 'white',
    -background => 'black',
    -width  => 80,
    -height => 20,
                 )->pack;

my $top =  $mw->Toplevel();
$top->withdraw;

my $terr = $top->Scrolled(
    'Text',
    -foreground => 'hotpink',
    -background => 'black',
    -width  => 80,
    -height => 20,
)->pack;

my $pid = open3( 0, \*OUT, \*ERR, "$0-sender" );
#the 0 is for ignoring \*IN  (STDIN) 
$mw->fileevent( \*OUT, 'readable', \&write_out );
$mw->fileevent( \*ERR, 'readable', \&write_err );

MainLoop;
##################################################### 
sub do_Toplevel {
  if (! Exists($top)) {
  $top = $mw->Toplevel(  );
  $top->title("T-ERR");
  $top->Button(-text => "Close",
          -command => sub { $top->withdraw })->pack;
        } else {
           $top->deiconify(  );
           $top->raise(  );
          }
 }
############################################################# 
sub write_out {
    my $str = <OUT>;
    $tout->insert( "1.0", $str );
    $tout->see("1.0");
}
#################################################### 
sub write_err {
    my $str = <ERR>;
    $terr->insert( "1.0", $str );
    $terr->see("1.0");
}
__END__

[download]
I'm not really a human, but I play one on earth. flash japh

In reply to Re: Trying to update a Tk:ROText widget as input is received from a backticked program by zentara
in thread Trying to update a Tk:ROText widget as input is received from a backticked program by mears

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.