run process in background without being adopted by

Question

If I run an external process via a perl program,the perl program will remain the parent of the process. Making process management easy.

system('sleep 3000'); # perl is still the parent

However if I try to run the process in the background so that the program does not have to wait for the process to exit...

system('sleep 3000 &'); 

The sleep process will be adopted by the systems init process and is no longer associated with the program that executed it.

What is the proper way to handle process management in this situation. How can I emulate running the process in the background but maintain process ancestry?

Answer 1

fork/exec and wait().

Fork creates the child process by creating a copy of the parent, the parent receives the process id of the child, and calls wait() on the child process id.

Meanwhile, the child process uses exec() to overlay itself (a copy of the parent) with the process that you wish to execute.

If you need more than one concurrent background job, I recommend Parallel::ForkManager.

Answer 2

You can use threads,

use threads;
my $t = async { system('sleep 3000'); };

# do something in parallel ..

# wait for thread to finish 
$t->join;

or fork

sub fasync(&) {
  my ($worker) = @_;

  my $pid = fork() // die "can't fork!"; 
  if (!$pid) { $worker->(); exit(0); }

  return sub {
    my ($flags) = @_;
    return waitpid($pid, $flags // 0);
  }
}

my $t = fasync { system('sleep 3000'); };

# do something in parallel ..

# wait for fork to finish 
$t->();