Again a process question from me. I'm very interested in this topic and I do a lot of experiments to learn more about it.

Now my goal is it to kill, suspend and resume a process from a TK GUI in Windows XP.

Again I was inspired from the Code of BrowserUK from this thread: http://www.perlmonks.org/?node_id=470827

First the code of the child process.

child.pl:

use strict;
use warnings;

$|=1;
print "$_\n" and select(undef,undef,undef,0.1) for 1 .. 1000;
[download]

Here the code of the father process which is using open to let the child process run.

father_open.pl

#!perl -slw
use strict;
use threads;
use threads::shared;
use Thread::Queue;

## A shared var to communicate progess between work thread and TK
my $Q = new Thread::Queue;
my $pid:shared;

sub work{
    $pid = open (CHILD_PROC, "perl child.pl |") or die $!;

    while( <CHILD_PROC> ) {
        $Q->enqueue( $_ );
    }
    close( CHILD_PROC );
}

threads->new( \&work )->detach;

use Tk;
use Tk::ProgressBar;

my $mw = MainWindow->new;                                
my $pb = $mw->ProgressBar()->pack();

my $repeat;
$repeat = $mw->repeat( 100 => sub {
    while( $Q->pending ) {
        my $progress = $Q->dequeue;
        return unless $progress;
        $repeat->cancel if $progress == 100;
        $pb->value( $progress )
    }
                       } );

$mw->Button('-text' => 'Cancel',
            '-command' => sub{ kill 9, $pid; exit(0); })->pack();

# No suspend and kill button because
# the signals SIGSTOP and SIGCONT do not exist for Windows 

$mw->MainLoop;
[download]

This code starts the child process sucessfully and it is possible to kill the child process. But I did NOT know how to supsend or resume the child process because after googling I had the knowledge that the signals SIGSTOP and SIGCONT do NOT exist for a Windows OS.

That's why I continued looking in google, CPAN, PerlMonks,... . So I found the Win32::Process module which allows it to suspend and resume a process.

Here you see the code of the father process using Win32::Process instead of open.

father_win32_process.pl

#!perl -slw
use strict;
use threads;
use threads::shared;
use Thread::Queue;

use Win32::Process;
use Win32;

use Data::Dumper;

sub ErrorReport
{
    print Win32::FormatMessage( Win32::GetLastError() );
}

## A shared var to communicate progess between work thread and TK
my $Q = new Thread::Queue;
my $ProcessObj_as_string:shared;
my $ProcessObj;

sub work{
    # save STDOUT
    open(my $STDOUT_ORIG, ">&", \*STDOUT) or die;

    # connect TO_CHILD_PROC with CHILD_PROC
    pipe(CHILD_PROC, TO_CHILD_PROC);

    # change STDOUT to TO_CHILD_PROC
    # --> STDOUT of child process is set to TO_CHILD_PROC and
    #     this is connected via pipe with CHILD_PROC
    open(STDOUT, ">&", \*TO_CHILD_PROC);
    
    Win32::Process::Create($ProcessObj,
                           "C:\\Perl\\bin\\perl.exe",
                           "perl child.pl",
                           1,
                           NORMAL_PRIORITY_CLASS,
                           ".")|| die ErrorReport();

    $ProcessObj_as_string = Dumper($ProcessObj);
    
    # restore STDOUT
    open(STDOUT, ">&", $STDOUT_ORIG) or die;

    while( <CHILD_PROC> )
    {
        chomp($_);
        $Q->enqueue( $_ );          
    }     
     
    close( CHILD_PROC );
}

threads->new( \&work )->detach;

use Tk;
use Tk::ProgressBar;

my $mw = MainWindow->new;                                
my $pb = $mw->ProgressBar()->pack();

my $repeat;
$repeat = $mw->repeat( 100 => sub {
    while( $Q->pending ) {
        my $progress = $Q->dequeue;
        return unless $progress;
        $repeat->cancel if $progress == 100;
        $pb->value( $progress );            
    }
} );

$mw->Button('-text' => 'Cancel',
            '-command' =>
            sub
            {
                my $VAR1;
                $ProcessObj = eval($ProcessObj_as_string);
                $ProcessObj->Kill(0);
                exit 0;
            })->pack();

$mw->Button('-text' => 'Suspend',
            '-command' =>
            sub
            {
                my $VAR1;
                $ProcessObj = eval($ProcessObj_as_string);
                $ProcessObj->Suspend();
            })->pack();

$mw->Button('-text' => 'Resume',
            '-command' =>
            sub
            {
                my $VAR1;
                $ProcessObj = eval($ProcessObj_as_string);
                $ProcessObj->Resume();
            })->pack();

$mw->MainLoop;
[download]

This code is also able to start successfully the child process and the child process can successfully be killed. It is also possible to suspend the child process. But afterwards it is NOT possible to resume it.

What am I doing wrong? Why is the suspending/resuming functionality NOT working properly in my code?

Is there perhaps any other solution to achieve my goal to kill/suspend/resume a process from a TK GUI in Windows?

Thank you very much!

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