freedns dynamic dns update script

update-freedns.sh

#!/bin/bash
#Handy update script for auto-updating your IP4 and IP6 dynamic DNS name if you use freedns.afriad.org.  
#Probably other providers could be used as well if you modify the update URLs slightly
#uses opendns.com's magic resolver to try and figure out actual public-facing IP addresses
set -e

#To set up:
#go create an A record (for IP4) and a AAAA record (for IP6) for the same dynamic domain name
#replace the <angle bracketed sections> with the appropriate dynamic dns name and update URLs
MY_DOMAIN=<your freedns dynamic domain name>
IP4_UPDATE_URL=<your freedns ip4 update URL>
IP6_UPDATE_URL=<your freedns ip6 update URL>

ACTUAL_IP4=$(dig +short myip.opendns.com @resolver1.opendns.com)
ACTUAL_IP6=$(dig +short -6 myip.opendns.com aaaa @resolver1.ipv6-sandbox.opendns.com)

REGISTERED_IP4=$(dig +short ${MY_DOMAIN} @ns1.afraid.org)
REGISTERED_IP6=$(dig +short -6 ${MY_DOMAIN} aaaa @ns1.afraid.org)

if [ "$ACTUAL_IP4" != "$REGISTERED_IP4" ]
then
    echo "Updating IP4 registration"
    curl "${IP4_UPDATE_URL}&address=${ACTUAL_IP4}"
else
    echo "IP4 Address has not changed (old: ${REGISTERED_IP4}, new: ${ACTUAL_IP4})"
fi

if [ "$ACTUAL_IP6" != "$REGISTERED_IP6" ]
then
    echo "Updating IP6 registration"
    curl "${IP6_UPDATE_URL}&address=$ACTUAL_IP6"
else
    echo "IP6 address has not changed (old: ${REGISTERED_IP6}, new: ${ACTUAL_IP6})"
fi