update-digital-ocean-dns-record

#!/bin/sh

usage(){
	fmt <<EOF
DESCRIPTION
	Check if the IP address of this host matches the DNS records of a remote host.  If it doesn't match, update the DNS records using the Digital Ocean API.

USAGE
	update-digital-ocean-dns-record -d,--domain=DOMAIN -s,--subdomain=SUBDOMAIN -k,--api-key=DIGITALOCEANAPIKEY
EOF
	exit
}
die(){ printf "Error: %s\n" "${1}" 1>&2; exit 1; }
require(){ command -v "${1}" > /dev/null 2>&1 || { suggestion=""; if [ ! -z "$2" ]; then suggestion=" $2"; fi; die "$1 is not installed.${suggestion}"; } }
if [ $# -eq 1 ]; then if [ "$1" = "--help" ] || [ "$1" = "-h" ]; then usage; fi fi
# End boilerplate

require "curl" "Try: apt-get install curl"
require "jq" "Try: apt-get install jq"

apiKey=""
domain=""
subdomain=""

for i in "$@"
do
case "${i}" in
	-d=*|--domain=*)
		domain="$(echo ${i} | sed 's/[-a-zA-Z0-9]*=//')"
	;;
	-k=*|--api-key=*)
		apiKey="$(echo ${i} | sed 's/[-a-zA-Z0-9]*=//')"
	;;
	-s=*|--subdomain=*)
		subdomain="$(echo ${i} | sed 's/[-a-zA-Z0-9]*=//')"
	;;
esac
done

if [ "${apiKey}" = "" ] || [ "${domain}" = "" ] || [ "${subdomain}" = "" ]; then
	usage
fi

# look up the existing dns entry
dnsIp=$(dig +short "${domain}")

if [ "${dnsIp}" = "" ]; then
	die "Couldn't resolve ${domain} while looking up DNS records."
fi

# look up our external ip
localIp=$(curl ifconfig.me 2> /dev/null)

if [ $? -ne 0 ]; then
	die "Couldn't resolve ifconfig.me while looking up local IP."
fi

if [ "${dnsIp}" != "${localIp}" ]; then
	# Get the record ID from Digital Ocean
	subdomainId=$(curl --silent --request GET --header "Content-Type: application/json" --header "Authorization: Bearer ${apiKey}" "https://api.digitalocean.com/v2/domains/${domain}/records" | jq ".[] | . [] | select(.name==\"${subdomain}\")" 2>/dev/null | grep "id" | sed --regexp-extended "s/[^0-9]//g")

	if [ $? -ne 0 ]; then
		die "Couldn't get subdomain ID from Digital Ocean."
	fi

	curl --silent --request PUT --header "Content-Type: application/json" --header "Authorization: Bearer ${apiKey}" -d "{\"data\":\"${localIp}\"}" "https://api.digitalocean.com/v2/domains/${domain}/records/${subdomainId}" > /dev/null

	if [ $? -ne 0 ]; then
		die "Couldn't connect to Digital Ocean API."
	fi
fi