#!/usr/bin/perl -w

# ip_check.pl - by dual
#
# Checks for and notifies user about WAN IP changes
###################################################


use strict;


# Read /tmp/in_ip
open my $tmp_in_ip, '<', "/tmp/in_ip" or die "Can't read in_ip: $!";
chomp(my $in_ip = <$tmp_in_ip>);


# Get WAN IP from whatip.gzo.com
my @source = `lynx -source http://whatip.gzo.com/`;

foreach my $line (@source) {
	my $out_ip;
	if ($line =~ /Your IP address is: (\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/) {
		$out_ip = $1;
	}
	compare($in_ip, $out_ip);
}


# Compare IPs, mail results and write /tmp/in_ip
sub compare {
	my ($old_ip, $new_ip) = @_;
	if ($old_ip ne $new_ip) {
		my $addy = "user\@localhost";
		open my $mail, "|/usr/bin/mail -s \"IP has changed!\" $addy"
			or die "Can't pipe: $!";
		print $mail "New IP: $new_ip\n";
		print $mail "\n";
		system("echo $new_ip >| /tmp/in_ip");
	}
	return 0;
}