My router is not updating DynDNS correctly, so I wanted to use a simple cron job to do the same. Here is a simple BASH/Shell script to update DynDNS:

IP=$(curl -s icanhazip.com)
curl -v -k -u username:password “https://members.dyndns.org/nic/update?hostname=DNSHOSTNAME.dyndns.org&myip=$IP”