UNIX System Administration Handbook, Third Edition

9 Periodic Processes

The key to staying in control of your system is to automate as many tasks as possible. For example, an adduser program can add new users faster than you can, with a smaller chance of making mistakes. Almost any task can be encoded in a shell, Perl, or expect script.

It’s often useful to have a script or command executed without any human intervention. For example, you might want to have a script verify (say, every half-hour) that your network routers and bridges are working correctly and have it send you email when problems are discovered.¹

¹Many sites go further than this and dial a pager with a modem, so that an administrator ...