Today, I had a client’s T1 line go down. Unfortunately, FairPoint Communications has had a mixed track record when it comes to telling us that they have (or more often, have not) fixed the issues.
So I wrote a simple bash script to ping the IP address of the router on the down T1 line, and email me when it came back up. Think of this as the ultra-poor man’s Nagios.
#!/bin/sh
ping -c 1 example.com
while [ $? != 0 ]; do
ping -c 1 example.com
done
echo "Example.com is up if you are reading this." | \
mail [email protected] -s "example.com is back up!";
exit
- The first line specifies what shell to run this script with (in this case, /bin/sh).
- The second line pings the currently down host (example.com) with 1 packet.
- The third line starts the while loop, and continues it as long as ping returns something other than a 0 (which indicates success).
- The fourth line pings the host again.
- The fifth line ends the loop, but only if ping succeeded (i.e. the host is up again).
- The sixth
- & seventh line emails [email protected] to let me know the host is back up.
- Finally, the eighth line exits.
Note that you have to have a working “mail” program in your path for this to work. If not, there are other options (touching a file, curling a URL, etc., but that’s beyond the scope of this example.