The first line of code uses grep to pull the line containing the filename, from an ls -la listing and then uses cut to remove every character from that line except the file size. Naturally you've gotta play around with the character removal part on the command line until it's working and ready to incorporate into the script. Watch out if an increase in file size also creates another character, like 99 to 100 as this would mess the system up somewhat.

The second line uses the mailx command to email me with the specified subject heading and also copies the contents of the file into the email body. Nifty. With IMAP running on the server, the email client (Outlook) checks for mail from my workstation every 5 minutes.

The hardest thing for me was getting the syntax right so it would run smoothly from within the if statement. That's where the good old internet comes into its own, a glance at examples of code usage can save a lot of swearing.

So now I can modify things to reflect the required file details. The script itself will live in the /var/db/ directory alongside the file it's monitoring, so I don't have to worry about absolute paths. Behold dhalert.sh..

The second part is to get the script to run all the time, continuously monitoring the file. The standard method is to use Cron. Here's my entry using the crontab -e command..

00,15,30,45 * * * * /var/db/dhalert.sh

See Part II for problem fixes and refinements..