Re: capturing output from running process crashes gtk2

[zentara <zentara1 sbcglobal net>]

On Wed, 2 Aug 2006 14:50:37 +0200 
"Ratcliffe, Jeffrey (Peters)" <Jeffrey Ratcliffe External eads com> wrote:


> Right. Almost there. The following script works, but gives me the warning "Name "main::WRITE" used only 
> once: possible typo at ./test_dialog3 line 23." If I replace \*WRITE with 0, then I get the error message 
> "open3: close(0) failed: Bad file descriptor at ./test_dialog3 line 23".
>
> How do I write it so as to avoid the warning?

As a followup to my last post, you could try to just
automatically send "\n" to WRITE where needed, but then
you lose control over stopping the scan with Control-D.

I've indicated some pseudo code below, where the print would go.

> #!/usr/bin/perl -w
>
> use strict;
> use Gtk2 -init;
> use IPC::Open3;
>
> my $script = <<END;
> #!/bin/bash
> while [ 0 ]
> do
> let ++page
> echo "Scanning page \$page" > "/dev/stderr"
> sleep 5
> echo "Scanned page \$page. (scanner status = 5)" > "/dev/stderr"
> done
> END
>
> open SCRIPT, "> test_scan" or die "Can't open script";
> print SCRIPT $script;
> close SCRIPT;
> chmod 0755, "test_scan"; # u+rwx,go+rw
>
> my $pid = open3(\*WRITE, 0 ,\*ERROR, "./test_scan" );
>
> my $dialog = Gtk2::Dialog->new ("Scanning...", undef,
>                                'destroy-with-parent',
>                                'gtk-cancel' => 'cancel');
> my $label = Gtk2::Label->new ("Scanning...");
> $dialog->vbox->add ($label);
>
> # Ensure that the dialog box is destroyed when the user responds.
> $dialog->signal_connect (response => sub { $_[0]->destroy;
>                                           local $SIG{HUP} = 'IGNORE';
>                                           kill HUP => $pid;
>                                           Gtk2->main_quit;
>                                         });
> $dialog->show_all;
>
> Glib::IO->add_watch(fileno(ERROR), 'in', sub {
>                             my $line;
>                             sysread ERROR, $line, 1024;
>                             if ($line =~ /Scanning page ([0-9]*)/) {
>                              $label->set_text("Scanning page $1...");
####################################################################                                
                                #may cause excessive scanning
                                #it may be possible to regex the $line, and only
                                #send the "\n" where you want to continue
                                print WRITE "\n";   #tells scanimage to continue
####################################################################
>                             }
>                             return 1;
>                            });
>
> Gtk2->main;
>
> __END__

Joe

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