updatedns

#!/usr/bin/env ruby

require 'fog'
require 'open-uri'

class BrandsmithDNS
  def initialize
    @dns = Fog::DNS.new(:provider => 'rackspace', :rackspace_api_key => 'xxxxxxxxxxxxxxxxxx', :rackspace_username => 'yyyyyyyyyyyyyyyyyy')
    @record = @dns.zones.get('11111111').records.get('A-222222222')
  end

  def dns_record_ip
    @dns_record_ip ||= @record.value
  end

  def actual_ip
    @actual_ip ||= open('http://whatismyip.akamai.com').read
  end

  def needs_update
    dns_record_ip != actual_ip
  end

  def update_record
    @record.value = actual_ip
    @record.save
  end
end

dns = BrandsmithDNS.new

puts "Current IP address: #{dns.actual_ip}"
puts "        DNS Record: #{dns.dns_record_ip}"
if dns.needs_update
  print "Updating..."
  dns.update_record
  puts "done."
else
  puts "Nothing to update."
end

updatedns.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key>
	<string>updatedns</string>
	<key>Disabled</key>
	<false/>
	<key>UserName</key>
	<string>nobody</string>
	<key>StartInterval</key>
	<integer>1800</integer>
	<key>ProgramArguments</key>
	<array>
		<string>/usr/local/bin/updatedns</string>
	</array>
</dict>
</plist>