cfddns.sh

#!/usr/bin/env bash

# Required API token permissions are "Zone:Read" and "DNS:Edit".

# Cronjob example:
# */15 * * * * { date --iso-8601=seconds; API_TOKEN=<token> /usr/local/bin/cfddns -z <id> -r <id>; printf "\n"; } >> cfddns.log 2>&1

usage="Usage: API_TOKEN=<token> cfddns -z <id> -r <id>"

set -o errexit
set -o pipefail

while getopts z:r:t: opt; do
    case $opt in
        z) zone_id="${OPTARG}" ;;
        r) record_id="${OPTARG}" ;;
        *)
            echo >&2 "${usage}"
            exit 1
            ;;
    esac
done
shift $((OPTIND - 1))

if test -z "${API_TOKEN}" || test -z "${zone_id}" || test -z "${record_id}"; then
    echo >&2 "${usage}"
    exit 1
fi

set -o nounset

ip="$(curl -4fsSL 'https://cloudflare.com/cdn-cgi/trace' | grep -Phoi '^ip=.+$' | awk -F= '{print $2}')"
echo "${ip}"

if ! echo "${ip}" | grep -P '^((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}$' > /dev/null; then
    echo >&2 "invalid ipv4 😠"
    exit 1
fi

response="$(
    curl -sSL \
        -X PUT \
        -H 'Content-Type: application/json' \
        -H "Authorization: Bearer ${API_TOKEN}" \
        -d "$(printf '{"type":"A","name":"@","content":"%s"}' "${ip}")" \
        "https://api.cloudflare.com/client/v4/zones/${zone_id}/dns_records/${record_id}"
)"

if test "$(echo "${response}" | jq -r '.success')" = "true"; then
    echo >&2 "record updated 🎉"
else
    echo >&2 "update failed 😠"
    errors="$(echo "${response}" | jq -r '.errors[]')"
    if test -n "${errors}"; then
        echo >&2 "${errors}"
    fi
    exit 1
fi