So you want to exit all children when you get the signal? Or just the child that recieved the signal?

Finishing a child is easy enough - you can call the $pm->finish if (...signal...).

To kill all children you'll have to keep a track of the currently active pids for the children and kill them yourself, Parallel::ForkManager doesn't have built in facilities for this ( as far as i am aware at least! ). Information on how to do this can be found in : Parallel::ForkManager question.

I am not sure what the best way to set off the infanticide would be though, I guess having a subroutine which accesses the list of pids, but there might well be stability issues, i.e. the child calls the sub, which kills the child... so you would have to make sure it is the original parent process that does the killing, and i am not sure how you would do this.

This way seems nasty though, and hopefully someone has a better idea!

I also just found this :

Parallel::Forker
Which has a lot of the functionality you described - It has been very recently updated, and I haven't checked it out as yet, but certainly looks like a good alternative to Parallel::ForkManager when you want a little more control...
HTH
Just a something something...

I can think of a few ways...

• signals (kill parent, parent kills children, or kill process group)
• shared memory
• trigger file of some sort
• some other IPC-type mechanism

I read the Synopsis and Description of Parallel::ForkManager because I was puzzled by the "and next" semantics in the call to start(). In the docs, it says, "The "and next" skips the internal loop in the parent process." Which internal loop is this? The surrounding foreach? Wouldn't that cause the rest of the foreach code to be skipped for the current iteration? In short, I'm still not clear on why the "and next" is required, and what it actually does. Would anyone be willing and able to comment on this? Thanks in advance.

start/fork duplicates the current process, and both the original process (parent) and the copy (child) continue executing from that same point

#!/usr/bin/perl --

use strict;
use warnings;

use Parallel::ForkManager;


my $pm = new Parallel::ForkManager(3);
for my $data ( 0 .. 2 ){
    my $pid = $pm->start and next; ## WITH NEXT
#    my $pid = $pm->start ;        ## WITHOUT NEXT
    print "data ($data) pid ($pid) \$\$($$)\n";
    $pm->finish; # Terminates the child process
}
__END__
[download]

The above program (with next) outputs

data (0) pid (0) $$(-1792)
data (1) pid (0) $$(-1856)
data (2) pid (0) $$(-1916)
[download]

The above program modified (without next) outputs

data (0) pid (-1944) $$(1992)
data (1) pid (-1656) $$(1992)
data (1) pid (0) $$(-1656)
data (0) pid (0) $$(-1944)
data (2) pid (-1924) $$(1992)
data (2) pid (0) $$(-1924)
[download]

When pid is 0, it is the child process, when it is not zero, it is the parent process.

Fork (operating system)

Mr. Peabody Explains fork()

You answered my question perfectly (I confess I'm new to the IPC game; actually I started reading that part of the Llama today). Good links. :)

In regards to the original question...I found this code on wikipedia, and it seems to do what you want(?).

#!/usr/bin/perl
 
$pid = fork();    #Declare fork
if ($pid == 0) {  #Jump into the Child process
    for ($j = 0; $j < 10; $j++) {
        print "child: $j\n";
        sleep 1;
    }
    exit(0);  #Exit the fork [child process]
} elsif ($pid > 0) {
    for ($i = 0; $i < 10; $i++) {
        print "parent: $i\n";
        sleep 1;
    }
    exit(0);  #Exit parent
}
[download]

So the thing here is to test the pid. In your code, you would say:

$pm->finish if ($pid == 0 && $content =~ m/string/);
#...no match, do more work...
$pm->finish;
[download]

Or am I totally missing the boat here (likely)? :)