gistfile1.sh

#!/bin/bash

EMAIL="MY_EMAIL"
TOKEN="MY_API_KEY"
DOMAIN_ID="erikreynolds.com"
RECORD_ID="MY_NUMERIC_RECORD_ID"

echo "Getting current external IP"
IP="`curl -s http://icanhazip.com/`"

echo "Updating external record to $IP"
curl -H 'X-DNSimple-Token: $EMAIL:$TOKEN' \
     -H 'Accept: application/json' \
     -H "Content-Type: application/json" \
     -i -X PUT https://DNSimple.com/domains/$DOMAIN_ID/records/$RECORD_ID.json \
     -d {\\"record\\":{\\"content\\":\\"$IP\\"}} -s > /dev/null