When using fork and exec, is there a way of not waiting for the child to complete? What I mean is that have fork create 3 clones of itself and not single or not wait for the child to finish and fork another child process and then round them up in the end.

I really find it difficult to understand what you're asking, sorry for this.

When fork() is called, you end up having two processes: the parent and the child. They both execute the same code (your Perl script), but you can understand if you're in the child testing whether the call returned 0. Then, you're supposed to call exec() (if you really need it) passing the control to the process you want to execute, but this isn't necessary if the code is in the parent script!

The two processes created by fork() are independent, so they will be both running after the call, if this is what you're worried about. Unlike system(), which waits for the child process to complete, after fork() you can do whatever you want in the parent process, even calling fork() two more times to complete the creation of your three subprocesses.

Simple snippet:

#!/usr/bin/perl
use strict;
use warnings;
sub child {
   print("Hey, I'm child $$\n");
   sleep(2 + rand(5));
   print("$$ exiting...\n");
   exit(0);
}

foreach (1 .. 3) {
   my $pid = fork;
   die "fork(): $@, stopped" unless defined($pid);
   child() unless $pid;
}

# Only the parent reaches this point
wait foreach (1 .. 3);
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which yelds, for example

Hey, I'm child 1048
Hey, I'm child 1368
Hey, I'm child 424
1368 exiting...
424 exiting...
1048 exiting...
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Flavio

Don't fool yourself.

I've had some good luck with Parallel::ForkManager and POE. The POE cookbook certainly has some great examples.

system "task1 &";
system "task2 &";
system "task3 &";
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