afraid-dns-update.py

""" 
 Quick Linux DNS IP Updater Python script for FreeDNS (freedns.afraid.org)
 
 Author: Daniel Gibbs
 Version: 0.2
 URL: http://www.danielgibbs.net/
 
 ** Must set update_key and make sure that ip_file is read and writable

 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
 Foundation; either version 2 of the License, or (at your option) any later
 version.

 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. 
 """
import sys
import os
import time
import stat
from urllib import urlopen

# FreeDNS Update Key
update_key = "UPDATE_KEY_HASH"

# FreeDNS Update URL
update_url = "http://freedns.afraid.org/dynamic/update.php?" + update_key

# External IP URL (must return an IP in plain text)
ip_url = "http://www.danielgibbs.net/ip.php"

# Open URL to return the external IP
external_ip = urlopen(ip_url).read()

# The file where the last known external IP is written
ip_file = ".freedns_ip"

# Create the file if it doesnt exist otherwise update old IP
if not os.path.exists(ip_file):
	fh = open(ip_file, "w")
	fh.write(external_ip)
	fh.close()
	last_external_ip = "Unknown"
	print "Created FreeDNS IP log file: " + ip_file
else:
	fh = open(ip_file, "r")
	last_external_ip = fh.read()
	last_external_ip = last_external_ip.rstrip('\n')
	
# Check old IP against current IP and update if necessary
if last_external_ip != external_ip:
	urlopen(update_url)
	print "External IP updated FROM (" + last_external_ip + ") TO (" + external_ip + ")"
	fh = open(ip_file, "w")
	fh.write(external_ip)
	fh.close()
else:
	last_ip_update = time.ctime(os.stat(ip_file).st_mtime)
	print "External IP (" + external_ip + ") has not changed. Last update was " + last_ip_update