Update SpDyn DynDNS (IPv6)

dyndns_update.sh

#!/bin/bash

HOSTNAME=[url]
DYNDNSUSER=[email]
DYNDNSPW=[SpDyn token]
DYNDNSURL=https://update.spdyn.de/nic/update

CURRENT_IP6=$(ip address show dev wlan0 | grep ff:fe | grep -v fe80: | awk '{print $2}' | sed 's/^\([0-9a-f:]*\).*/\1/g')
DNS_IP6=$(host -t AAAA ${HOSTNAME} | tr " " "\n" | grep ff:fe)

if [[ "${CURRENT_IP6}" == "" ]]; then
  date
  echo ERROR - COULD NOT GET OWN IP
  exit
fi

if [[ "${CURRENT_IP6}" == "${DNS_IP6}" ]]; then
  # Printing if everything is ok just spams the log.
  # echo OK.
  :
else
  date
  echo The DNS knows ip: ${DNS_IP6}
  echo The real ipv6 address is: ${CURRENT_IP6}
  echo Renew DNS ...
  echo Sending request to ${DYNDNSURL}\?myip\=${CURRENT_IP6}\&hostname\=${HOSTNAME}\&username\=${HOSTNAME}\&password\=${DYNDNSPW}
  curl --user ${HOSTNAME}:${DYNDNSPW} ${DYNDNSURL}\?myip\=${CURRENT_IP6}\&hostname\=${HOSTNAME}\&username\=${HOSTNAME}\&password\=${DYNDNSPW}
  echo
  echo Done. Sleep 60 seconds.
  sleep 60
  echo Lookup again ...
  DNS_IP6=$(host -t AAAA ${HOSTNAME} | tr " " "\n" | grep ff:fe)
  if [[ "${CURRENT_IP6}" == "${DNS_IP6}" ]]; then
    echo DNS ok
  else
    echo ERROR - COULD NOT UPDATE DNS \(or dns TTL is longer than expected\)
  fi
fi