#!/bin/perl -w
use strict;

pipe(READER,WRITER); # used for communication between child and parent

#$SIG{'CHLD'} = 'reaper'; # used for killing zombies

my $zahl = 0; # number of currently running children
my $zeile;    # row
my $pid;      # process ID

if (open FILE, "< /sls_backup/mdjanan/sleep.txt")
{
    while($zeile = <FILE>)
    {
        if ($zahl < 4)
        {
            $zahl++;          # increase number of children
            $pid = fork(); # a new child is born. yay :)
            print $pid."\n";
        }
        if($pid == 0)
        {
            # child-process
            #close WRITER;
            # wait for command from parent
            while (my $line = <READER>)
            {
                print "$line\n";
                exec($line); # execute command
            }
        }
        else
        {
            #close READER;
            # send child a command
            sleep 1;
            print WRITER $zeile;
            if($zahl == 4) # four children are running. wait till one of them finishes.
            {
                while(! wait()) # *waiting*
                {
                }
                print "returncode ".$?."\n";
                $zahl--; # decrease number of children
            }
        }
    }
}
else
{
    print "\nCan't open file /sls_backup/mdjanan/sleep.txt\n";
}
exit 0;

# Waits for zombies
#sub reaper
#{
#    wait(); # grab a zombie
#} # sub reaper