To solve this issue, I created two simple shell scripts. These scripts will run in almost all *nix systems without any hiccups. The first script ip_check.sh does exactly what the name suggests. Every time it is ran, it checks the IP address, if there are any changes, it will send out an email; otherwise, it will log the results and continue. The second script reset_weekly.sh goes and clears out the log files and email messages and creates a new one for the next week.
- You need to pre-configure ssmtp in order to have the email functionality work.
-You can also use a different email client. In which case make the appropriate adjustments to ip_check.sh script.
- You also need to create a directory /monitor/IP/ or change the script to run operate on a different directory.
I am using the built in cron functionality of *nix. Cron is a task scheduling system (see link below). I took the ip_check.sh and placed it in the hourly folder for cron. In my system that happens to be /etc/cron.hourly/. You system might differ. You can always check the crontab file at /etc/crontab for more information. Cron will execute all scripts in this folder every hour.
Second thing I did was place the reset_weekly.sh in the weekly folder located at /etc/cron.weekly/. The reason being, I want everything to be reset every week.
At this point, the system is all set up to run the scripts automatically and notify if there are any changes to your public IP address.