#!/bin/sh

DomainName=
Username=
Password=
WANInterface=

CurrWANIP=$(ip -o -4 addr show $WANInterface | awk -F '[ /]+' '{print $4}')
GDNSIP=$(dig $MyGDomain +short)

if [ "$CurrWANIP" == "$GDNSIP" ]; then
        logger "Google Domains DDNS: WAN IP ($CurrWANIP) unchanged, no update necessary"
else
        ipupdate=$(curl -s https://$Username:$Password@domains.google.com/nic/update?hostname=$MyGDomain&myip=$CurrWANIP)
        if [ "$ipupdate" == "good $CurrWANIP" ]; then
         logger "Google Domains DDNS: DNS updated to $CurrWANIP from $GDNSIP"
        else
         logger -s "Google Domains DDNS: Error: $ipupdate"
        fi
fi