#!/bin/bash
#Original Script by Tomcat from the Gentoo Forums - https://forums.gentoo.org/viewtopic-t-282630-start-0.html

if [ `/usr/bin/whoami` = 'root' ] 
then 
        OLDIP=`cat /etc/vsftpd.conf | grep pasv_address |  sed -e 's/pasv_address=\([0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\)/\1/'` 
        CURRENTIP=$(dig meineadresse.dyndns.org +"short")

        if [ "$OLDIP" != "$CURRENTIP" ]; 
        then  
                echo "$(date +'%a %b %d %T %Y') *** Public IP changed from $OLDIP to $CURRENTIP" >> /var/log/vsftpd.log 
                sed 's/\(pasv_address=\)\([0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\)/\1'$CURRENTIP'/' /etc/vsftpd.conf > /etc/vsftpd.conf.new &&
		mv /etc/vsftpd.conf.new /etc/vsftpd.conf && 
                echo "$(date +'%a %b %d %T %Y') *** Pasv_address setting updated successfully - restarting daemon" >> /var/log/vsftpd.log &&
                service vsftpd restart 

# this will spam much output in your log terminal 
#       else 
#               echo "$(date +'%a %b %d %T %Y') *** IP check OK - IP unchanged" >> /dev/tty12 
        fi 
else 
        echo "Permission denied" 
fi