Re: Glib::IO watcher unbuffered?

[zentara <zentara1 sbcglobal net>]

On Fri, 19 Jan 2007 09:24:53 +0100
"Philipp E. Letschert" <phil uni-koblenz de> wrote:

> I would like to have unbuffered output processing from an external command
> (command prints a line, sleeps, prints a line, sleeps ...):

>    else {
>        my $line = <$pipe>;

> I tried to have $line processed without delay (autoflush all handles
> everywhere...), but the watcher only prints bunches of lines after some longer
> delay. 
> Why does the buffering happen and how to turn it off?

I think your problem is that <> blocks until it hits an EOF, but your
pipe never sends it.  It's a common problem with running top thru
a pipe. Try using sysread:

#!/usr/bin/perl -w
use strict;
use Glib  qw(TRUE FALSE);
use Gtk2 -init;
use Gtk2::Helper;

open(FH, "top -b |") or die "$!\n";

my $helper_tag = Gtk2::Helper->add_watch(fileno FH, 'in',sub{
                        &watch_callback('FH');
            });

#standard window creation, placement, and signal connecting
my $window = Gtk2::Window->new('toplevel');
$window->signal_connect('delete_event' => sub { exit;});
$window->set_border_width(5);
$window->set_position('center_always');

my $hbox = Gtk2::HBox->new();
$hbox->set( "border_width" => 0 );
$window->add($hbox);

my $scroll   = Gtk2::ScrolledWindow->new;
$scroll->set_size_request(600,600);
my $textview = Gtk2::TextView->new;
my $buffer = $textview->get_buffer;
create_tags($buffer);

$scroll->add($textview);
$hbox->pack_start($scroll,1, 1, 1 ); # expand?, fill?, padding;

$window->show_all();

#our main event-loop
Gtk2->main;

sub watch_callback {

        my ($fh) = @_;
        
        my $line;
        #read 1000 caracters of the buffer
        #$fh->sysread($line,1000);
        sysread(FH,$line,4096);
          
        #remove the newline
        chomp $line;
        
        if($line){
           $buffer->insert_with_tags_by_name($buffer->get_end_iter, $line,'blue');
        }else{
           Gtk2::Helper->remove_watch($helper_tag);                              
        }

        # need the main iteration here 
        Gtk2->main_iteration while Gtk2->events_pending;
        $textview->scroll_to_iter($buffer->get_end_iter,0,0,0,0);

        #important so we can loop again 
        return 1;
}
#########################################################3
sub create_tags{
  my $buffer = shift; 

   $buffer->create_tag('blue',
           foreground => 'blue',
           );

   $buffer->create_tag('col',
           foreground => 'green',
           );

}
#############################################################################
__END__


zentara


-- 
I'm not really a human, but I play one on earth.
http://zentara.net/japh.html