Perl script for getting the broadcast address from an IP address and netmask

getbroadcastaddr.pl

#!/usr/bin/perl -s

our $v;

use Socket qw/inet_ntoa inet_aton/;

if (@ARGV[0] =~ s#(/\d+)$##) { $ARGV[1] = $1; }

@ARGV >= 2 or die "Usage: perl $0 <address> <netmask>\n
netmask may be of the form '255.255.255.0' or '/24'
";

my $addr = inet_aton($ARGV[0]) // die "Unable to parse as IP address: $ARGV[0]";
my $netmask;

if ($ARGV[1] =~ m#/(\d+)$#) {
		my $nbits = $1;
		if ($nbits < 1 || $nbits > 32) { die "Invalid CIDR size $nbits (must be 1-32)"; }
		$netmask = pack 'N', 0xFFFFFFFF ^ ((1 << (32-$nbits))-1);
		print STDERR "netmask: ", inet_ntoa($netmask), "\n" if $v;
} else {
		$netmask = inet_aton($ARGV[1]) // die "Unable to parse as IP address; $ARGV[1]";
}

my $all_ones = "\xFF" x 4;

$zero_addr = $addr & $netmask;
$bc_addr = $zero_addr | ($netmask ^ $all_ones);

print "broadcast address = " if $v;

print inet_ntoa($bc_addr), "\n";