#!/usr/bin/perl -w

use strict;

use POSIX qw(:signal_h :errno_h :sys_wait_h);



sub sched{

  my $file = shift || die "Missing parameter for subroutine call\n";
  my $time = shift || die "Missing second parameter on subroutine call+\n";
  my $chd = shift;
  sleep 5;
  my $cmd = `cat $file`;
  print " Child $chd in sched \n";
  print $cmd;   
}

# main program

my $pid; # process id
my $counter = 0;

my %children; # Hashtable to hold all pids of our children

my @childs; # will hold all pids of our children

$SIG{CHLD} = 

 sub{
    my $pid;
    my $j = -1;
    $pid = waitpid(-1, &WNOHANG);
    if (WIFEXITED($?)) {                       # Remove the child that just died
        if($children{$pid}){;
		$j = $children{$pid};
		delete $children{$pid};		 
		delete $childs[$j];
		print "Process $pid exited $j and $#childs\n";	
 
	}
        
    }
         
 };


$SIG{TERM} =
  sub{
        kill -9, @childs;
    	exit(0)
  }; # allow to end program by pressinc Ctrl-C or a kill call

#this will hold all of our tasks
my @tasks = (
  {
    file => "msg.1",
    time => 10,
  },
  {
    file => "msg.2",
    time => 2,
  },
  {
    file => "msg.3",
    time => 5,
  },
);

# looping through the array of hashes and forking with each element

my $j =0;

FORLOOP: for my $i ( 0..$#tasks){

	 FORK: {
	 
	   if ($pid = fork){            # first fork
	     # we are parent
             push @childs,$pid;
	     $children{$pid} = $#childs;
	     print "Parent forked child # ===> $#childs,  pid = $pid \n";
	     next FORLOOP;     	     
	   }elsif (defined $pid){       # so we are a child
	     print "Executing child $j \n";
	     sched($tasks[$i]{file},$tasks[$i]{time}, $j);
	     print "Done! pid = $pid\n";
	     exit(0);  
	   }elsif ($! =~/No more process/){
	     sleep 5;
	     redo FORK;
	   }else{
	     die "Something is wrong: $!\n";
	   }
	 }

}
print "started all children   $#childs \n";

while ($#childs > -1 ){;}  #Exit after all children are dead.