A cron script to periodically update a DNS record in DNSimple for a dynamic IP address.

update_ip_address.sh

#!/bin/bash
#
# When a machine is on a dynamic IP address cable modem, we use this script to
# periodically update DNS with the current record.
#
# 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: XXXXXXXXXXXXXXXXXXXXXXXXXXX' \
     -H 'Accept: application/json' \
     -H 'Content-Type: application/json' \
     --include --silent \
     -X PUT -d "{\"record\":{\"content\":\"$IP_ADDRESS\"}}" \
     https://dnsimple.com/domains/example.com/records/1234567 > /tmp/update_ip_address.out