Linode dynamic DNS updating script

update-dns.sh

#!/bin/sh
# modified by jfro from http://www.cnysupport.com/index.php/linode-dynamic-dns-ddns-update-script
# Uses curl to be compatible with machines that don't have wget by default

LINODE_API_KEY=licensekey
DOMAIN_ID=domainid
RESOURCE_ID=resourceid

WAN_IP=`curl -s http://example.com/whatsmyip.php`
if [ -f $HOME/.wan_ip.txt ]; then
        OLD_WAN_IP=`cat $HOME/.wan_ip.txt`
else
        echo "No file, need IP"
        OLD_WAN_IP=""
fi

if [ "$WAN_IP" = "$OLD_WAN_IP" ]; then
        echo "IP Unchanged"
else
        echo $WAN_IP > $HOME/.wan_ip.txt
        echo "Updating DNS to $WAN_IP"
        curl -s https://api.linode.com/?api_key="$LINODE_API_KEY"\&api_action=domain.resource.update\&DomainID="$DOMAIN_ID"\&ResourceID="$RESOURCE_ID"\&Target="$WAN_IP" > /dev/null
fi