Anyways, with the lack of details, I think you probably need to kill the $pid of program_ipc, otherwise post details of what this program outputs, and how it operates.

In the meantime, try something like the following, and remember, you may need to use Proc::Killfam instead of a plain kill, depending on whether you get the pid of any shell running the program.

#!/usr/bin/perl
# tktail pathname
use warnings;
use strict;
use Tk;

my $pid = open(H, "tail -f -n 25 $ARGV[0]|") or die ;

my $mw = MainWindow->new;
my $t = $mw->Text(-width => 80, -height => 25, -wrap => 'none');
$t->pack(-expand => 1);
$mw->fileevent('H', 'readable', [\&fill_text_widget, $t]);
$mw->OnDestroy(\&quitCB);
MainLoop;

sub fill_text_widget {
my($widget) = @_;
my $text = <H>;
$widget->insert('end', $text);
$widget->yview('end');
} # end fill_text_widget

sub quitCB {
kill 9,$pid or die $!;
exit;
}
[download]

Thanks for the responses.

By 'receive commands', I just mean that some other program writes a text message to the file that the tk-program is looking at (through the fileevent method). The tk-program then gets a call to the _process_fileevent method, reads the file handle and does whatever it says.

I am attempting to use the 'kill 9' command from your code however I and using the FileHandle module to open the pipe so I don't now how to get the pid of the tail process. Any suggestions?

$fh = FileHandle->new("tail -f -n 25 command_file |");

Thanks again Brian

I don't now how to get the pid of the tail process. Any suggestions?

$fh = FileHandle->new("tail -f -n 25 command_file |");

The only way to get the $pid is to use a piped-open as described in perldoc perlipc, or use something like IPC::Open3, but you sometimes get a shell pid, which then executes your program.

So use something like this:

my $fh = new FileHandle;
my $pid = open( $fh , "tail -f -n 25 command_file  | ") or die ;
#.....
# now you can check the output of ps to see if you get a shell $pid 
# or just your process $pid
# then to make sure you kill all shells and commands, if you see
# the $pid is the shell

use Proc::Killfam;
$mw->protocol('WM_DELETE_WINDOW' => sub {
                       killfam 9,$pid;
                       exit;
                      });
# or put the killfam in the callback of an Exit button, etc
[download]

Before I get slapped on the wrist for using killfam 9, remember that 9 is an instant kill, you may want to use a softer signal like 15, to allow the program to gracefully close.

---

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh

It's been a while since I've seen actual FileHandle usage. You don't need it; assuming you're using a perl newer than 5.00505:

open(my $fh, '-|', qw( tail -f -n command_file)) || die("Unable to run tail: $!.\n");

You can pass a single string, but whenever possible, call system(), open(), etc. with a list for the command; it's safer, because you're guaranteed not to get filtered through /bin/sh.

Anyway how the program being called and how it executed, yo will need to manager if you're invoking it from the Tk program. You had not told in which operational system you're running that, but for UNIX like systems you should look at the functions fork, open, waitpid and POSIX signals.

If you have control of the program being executed (you can modify it's source code), this will be even easier.

Regarding the See IO::Select to try to use non-blocking reading.

Thanks for the response,

The OS is CentOs Linux. The program that is sending the command to the Tk-program is external and unrelated.

Are you suggesting that the fileevent method is not the best way to listen and process external commands in a non-blocking way?

Thanks Brian