In the previous post, i mentioned that I would have some uses for the smsme script that I wrote. Here's a script that checks your external IP address against what you have registered in the DNS system, and alerts you when the address changes. Also, I've included instructions for creating a user cron job to check every hour on the hour. ------------------------------------------------------------------------ #!/bin/bash DNS=`nslookup cem.me 8.8.8.8 | grep 'Address: ' | grep -Eo '[0-9\.]+'` EXTIP=`wget -q -O - http://checkip.dyndns.org | grep -Eo '[0-9\.]+'` if [ $DNS != $EXTIP ] ; then `/home/username/bin/smsme IP CHANGED: $EXTIP` fi ------------------------------------------------------------------------ The DNS command goes to Google’s DNS, pipes the output to search for 'Address:' followed by a space, and then pulls out the IP address. The EXTIP goes to http://checkip.dyndns.org and parses out your IP To create the cron job, create a new file (crontab.<username>.file) and enter in the text below: 0 * * * * /home/<username>/bin/checkip.sh This line says (in the 0 * * * *) part to run on the hour (00), every hour (*), every day (*), every month(*), every day of the week(*) and will run our script that we wrote above (/home/<username>/bin/checkip.sh) make sure you replace the <username> part with your username #this allows your user to run cron jobs sudo su echo <username> >>/etc/cron.allow exit #set cron crontab crontab.username.file #view to confirm crontab -l |
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cron Monitoring for IP Address Changes and SMSing via Google Voiceposted Aug 13, 2010 3:26 PM by Carl Mehner |