Example script to set a dynamic record in DNSimple based on the current cable modem address. This can be run in /etc/cron.hourly.

update_ip_address.sh

#!/bin/bash
#
# Since paig is on a dynamic IP address cable modem, we use this script to
# periodically update DNS with the current record. In this case, we're using
# the hostname paig.2surfers.com.
#
# Keep the contents of this file secret, since it contains the domain's API
# key. The ID of the record to be updated by hovering over it in DNSimple's
# web interface.

IP_ADDRESS="`curl -s http://icanhazip.com/`"

curl -H 'X-DNSimple-Domain-Token: xxxxxxxxxxxxxxxxxxxxxxxx' \
     -H 'Accept: application/json' \
     -H 'Content-Type: application/json' \
     -k -i -s -X PUT \
     -d "{\"record\":{\"content\":\"$IP_ADDRESS\"}}" \
     https://dnsimple.com/domains/2surfers.com/records/1612769 > /tmp/update_ip_address.out