do_dyndnsclient/updatedns.sh

#!/bin/sh

echo "Current time: $(date "+%Y-%m-%d %H:%M:%S")"
ip_file="ip"

new_ip=$(curl -s http://ipecho.net/plain)

# Fallbacks
if [ -z "$new_ip" ]; then
    new_ip=$(curl -s http://whatismyip.akamai.com)
fi
if [ -z "$new_ip" ]; then
    new_ip=$(curl -s http://icanhazip.com/)
fi
if [ -z "$new_ip" ]; then
    new_ip=$(curl -s https://tnx.nl/ip)
fi

if [ -z "$new_ip" ]; then
    echo "Empty IP !"
    exit 0
fi

if [ -f $ip_file ]; then
  ip=$(cat $ip_file)
  if [ "$ip" = "$new_ip" ]; then
    echo "Same ip: $ip"
    exit 0
  fi
fi

update=$(curl -s -X GET "https://ip4.ddnss.de/upd.php?key=c1eed0f30eaa1a599570f18def222738&host=metzner.myhome-server.de")

if echo "$update" | grep -q "Updated 1 hostname"; then
    echo "DDNSS-IP changed to: $new_ip"
  echo "$new_ip" > $ip_file
else
  printf "Update failed:\\n%s" "$update"
  exit 1
fi