Cloudflare dynamic DNS

cfdns.sh

#!/bin/sh

set -eu

token='<your API token>'
zone='<your DNS zone ID>'
record='<your DNS record ID>'
ip_url='ifconfig.co'

call() {
	url="$1"
	shift
	json="$(curl --silent \
		-H "Authorization: Bearer $token" \
		-H "Content-Type: application/json" \
		"$@" "https://api.cloudflare.com/client/v4/$url")"
	if [ "$(echo "$json" | jq .success)" != "true" ]; then
		echo "API request ($* $url) failed:" >&2
		echo "$json" | jq .errors >&2
		exit 1
	fi
	echo "$json"
}

dns_ip="$(call "zones/$zone/dns_records/$record" | jq -r .result.content)"
current_ip="$(curl --silent "$ip_url")"
if [ "$dns_ip" = "$current_ip" ]; then
	echo "DNS IP address up to date ($dns_ip). Nothing to do."
	exit 0
fi

echo "IP address changed: '$dns_ip' -> '$current_ip'. Updating..."
template='{"type": "A", "name": "serve.mort.coffee", "content": $ip, "ttl": 1}'
call "zones/$zone/dns_records/$record" -X PUT \
	--data "$(jq --null-input --arg ip "$current_ip" "$template")" >/dev/null