Bash script (to be run periodically by cron) to check for external IP address changes. If any, emails the specified email of the change, and what the machine's new external IP is.

Check for IP change

#!/bin/bash

##Required/recommended packages:
#    mailutils
#    msmtp
#    msmtp-mta

currentIp=$(cat ~/ip.log)
grabbedIp=$(wget -O - -q -nv --delete-after www.icanhazip.com)
email="mail@yourdomain.com"
if [ "$currentIp" != "$grabbedIp" -n -a "$grabbedIp" ] ;
then
	echo -e As of $(date): '\n'IP address has changed from $currentIp to $grabbedIp | mail -s "IP ADDRESS CHANGE" $email
	echo $grabbedIp > ~/ip.log
fi