#!/usr/bin/perl

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

$SIG{CHLD} = \&REAPER;
my (@all_kids, @dead_kids);
my @array = qw(a b c d e f g h);

for (1 .. 10) {
    my $pid = fork();
    if ($pid) {
        push (@all_kids, $pid);
    }
    elsif ($pid == 0) {
        print "@array\n\n";
        sleep 5;
        exit (0);
    }
    else {
        die "Could not fork: $!\n";
    }

    print "Running another child process - $pid.\n";
}

print "All child processes have been ran.\n";
print "@all_kids\n";

$SIG{INT} = \&tsktsk;

foreach (@all_kids) {
    waitpid ($_, 0);
}

print "All child processes are finished.\n";

sub tsktsk {
    print "Ctrl-C Trap\n";

    my %alive_kids;
    for my $i (@all_kids, @dead_kids) {
        $alive_kids{$i}++;
    }

    for (sort keys %alive_kids) {
        print "$_\n" if ( $alive_kids{$_} == 1 );
    }
    exit;
}

sub REAPER {
  my $pid;
  $pid = waitpid(-1, &WNOHANG);

  if ($pid == -1) { }
  elsif ( WIFEXITED($?) ) {
      print "Process $pid exited.\n";
      push( @dead_kids, $pid )
  }
  else {
      print "False alarm on $pid.\n";
  }

  $SIG{CHLD} = \&REAPER;
}