ufw rule for dynamic host. Usage

ufw dynamic host

#!/bin/bash
HOSTNAME=dynamichost.domain.com
LOGFILE=$HOME/ufw$HOSTNAME.log
Current_IP=$(host $HOSTNAME | head -n1 | cut -f4 -d ' ')

if [ ! -f $LOGFILE ]; then
        /usr/sbin/ufw allow from $Current_IP to any port 22 proto tcp
        /usr/sbin/ufw allow from any to $Current_IP port 22 proto tcp
        echo $Current_IP > $LOGFILE
else

    Old_IP=$(cat $LOGFILE)
    if [ "$Current_IP" = "$Old_IP" ] ; then
        echo IP address has not changed
    else
        /usr/sbin/ufw delete allow from $Old_IP to any port 22 proto tcp
        /usr/sbin/ufw delete allow from any to $Old_IP port 22 proto tcp
        /usr/sbin/ufw allow from $Current_IP to any port 22 proto tcp
        /usr/sbin/ufw allow from any to $Current_IP port 22 proto tcp
        echo $Current_IP > $LOGFILE
        echo iptables have been updated
    fi
fi

#Usage: 
#sudo contrab -e
#*/30 * * * * /bin/sh /home/lz/script.sh
#If you run the first time not as root it'll produce the logfile, so in the nxt time as root it'll say that ip didn't change and do nothing. Run first time as user. Delete log file if you did this mistake.