#!/usr/bin/perl -w 
use strict;

$SIG{CHLD}=\&catchChildDeath;

#  Track how many children we have running
our $children=0;

#   Limits on min and max for number of children to run
my $min_child=5;
my $max_child=10;

#   Enable or disable our ability to spawn
my $spawnEnabled=1;

# Run until killed
while(1){
    spawn();
    sleep 5;
}

exit(0);

#  Deal with the death of a child.  A sad event to be sure. 
sub catchChildDeath{
    printf "Death of child noted.\n";
    $children--;
    $children = ( $children < 0 ? 0 : $children);
    unless ($spawnEnabled){
        $spawnEnabled = ( $children < $min_child ? 1 : 0 );
    }
    printf "There are %d children running\n",$children;

}

#  Spawn if we must, or not.
sub spawn{

    unless ( $spawnEnabled ) {
        if ($children <= $min_child ){
            $spawnEnabled=1;
        } else {
            return unless $spawnEnabled;
        }
    }
    if ( fork()){
        $children++;
        $spawnEnabled = 0 if $children > $max_child;
        printf "%d children running\n",$children;
    } else {
        kidPlay();
    }
}

#   This encapsulates the behavior of the child. 
sub kidPlay{
    my $iter=0;
    printf "Child PID: %d\n",$$;
    while($iter++ < 10){
        sleep 1;
    }
    printf "Child PID: %d exiting..",$$;
    exit(0);
}