Example of Parallel::ForkManager, with setuid() and with returning data to parent, using /dev/shm for temp storage

forkmanager_example.pl

#!/usr/bin/perl
use strict;
use warnings;
use Parallel::ForkManager 1.7.6;
use Data::Dumper;
use POSIX qw(setuid setgid);
use File::Temp;

# We make a temp tmp dir in memory (/dev/shm/) instead of built in /tmp/ (for speedy access)
my $tmpdir =  mkdtemp("/dev/shm/$0.XXXXXXXXX") ;
# Make perms like /tmp/
chmod oct(1777), $tmpdir;


# INIT ForkManager to 10 forks and our custom tmp dir
my $pm = new Parallel::ForkManager(10, $tmpdir);


##-- Setup a callback for when a child finishes
$pm->run_on_finish( sub {
    my ($pid, $exit_code, $ident, $exit_signal, $core_dump, $data_structure_reference) = @_;

    print "\n** $ident just finished ".
      "with PID $pid and exit code: $exit_code\n";

    print Dumper($data_structure_reference);
});


##-- Main loop

foreach ((1,2,3,4,5,6)) {
  $pm->start("Proc $_") and next;
  
  ## -- We are now the child process

  setuid(33);
  setgid(33);
  
  # Store some data to return
  my %res;
  $res{$_} = " pid $$";
  $res{'id'} = `id`;

  $pm->finish(0,\%res);
  
}

$pm->wait_all_children;


rmdir $tmpdir;