#!/usr/bin/perl -w
use strict;
use Net::Ping;
use Getopt::Std;
$|++;

my %opts;
getopts('?ht:s:',\%opts);
if ($opts{'h'} or $opts{'?'}) {
  print "Usage:\n";
  print "\t$0 [-t timeout] [-s subnet]\n";
  exit;
}
$opts{'t'} ||= 5;
unless ($opts{'s'}) {
  print "Enter subnet: ";
  chomp($opts{'s'} = <STDIN>);
}
$opts{'s'} =~ s/^(\d+)\.(\d+)\.(\d+).*/$1.$2.$3/ or die "Bad subnet format: use xxx.xxx.xxx";

my (@up,@down);
my @ips = map {"$opts{'s'}.$_"} 1..254;

my $ping = Net::Ping->new("icmp",$opts{'t'});
$SIG{INT} = \&cleanup;

for (@ips) {
  if ($ping->ping($_)) {
    print "Host $_ is UP\n";
    push @up, $_;
  } else {
    print "Host $_ is DOWN\n";
    push @down, $_;
  }
}
cleanup();

sub cleanup {
  print "Cleaning up and writing output files..";
  open UP_FILE, ">ips_online" or die "Can't create online ip file: $!";
  print UP_FILE map {"$_\n"} @up;
  close UP_FILE or die "Can't close online ip file: $!";

  open DOWN_FILE, ">ips_offline" or die "Can't create offline ip file: $!";
  print DOWN_FILE map {"$_\n"} @down;
  close DOWN_FILE or die "Can't close offline ip file: $!";
  print "Done.\n";
  exit;
}