Bash script to use from cron to dynamically update IP on Amazon route 53

update-ip

#!/bin/bash

source ~/.rvm/environments/default

DNS_ZONE=yourdomain.com
DNS_RECORD=yourhost.yourdomain.com.

IP_CACHE_FILE="$(dirname $0)/update-ip.cache"

if [[ -r "$IP_CACHE_FILE" ]]; then
    LAST_KNOWN_IP=$(< "$IP_CACHE_FILE")
fi

CURRENT_IP=$(curl -s http://checkip4.zerigo.com/ | perl -pe 's{<ipv4>(.*?)</ipv4>}{$1}')

if [[ "$CURRENT_IP" != "$LAST_KNOWN_IP" ]]; then
    echo "Updating IP Address -- ${LAST_KNOWN_IP} -> ${CURRENT_IP}"
    route53 -g --zone "${DNS_ZONE}" --name "${DNS_RECORD}" --type A --values "${CURRENT_IP}"
    echo "$CURRENT_IP" > "$IP_CACHE_FILE"
fi