UFW ssh access from dynamic ip

update_ufw.bash

#!/bin/bash
HOSTNAME=dynamicdns.tld # Your Dynamic DNS Hostname 
PORT=22 # SSH Port

if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root"
   exit 1
fi

new_ip=$(host $HOSTNAME | head -n1 | cut -f4 -d ' ')
old_ip=$(/usr/sbin/ufw status | grep $HOSTNAME | head -n1 | tr -s ' ' | cut -f3 -d ' ')

now=$(date)

if [ "$new_ip" = "$old_ip" ] ; then
    echo  [ $now ]:[ $old_ip ] IP address has not changed.
else
    if [ -n "$old_ip" ] ; then
        /usr/sbin/ufw delete allow from $old_ip to any port $PORT
    fi
    /usr/sbin/ufw allow from $new_ip to any port $PORT comment $HOSTNAME
        echo  [ $now ]: UFW iptables have been updated. [ $old_ip ] => [ $new_ip ]
fi