at, cron, and anacron

Choosing a System

Of the three scheduling systems, cron is probably the best-known. If you want to simplify your life and learn only one system, cron is undoubtedly the most versatile one. However, it can be needlessly complex, especially for non-root users.

If you only schedule occasional, one-time tasks, the at family of commands should suffice for you. However, if the exact timing of tasks is irrelevant to you, then anacron is ideal for regularly repeated tasks. In fact, some writers suggest that anacron is the scheduler best-suited to standalone laptops and workstations.

But whichever scheduler you use, you can be confident that you are using technology that has lasted several decades and that fits well with other classic Bash commands. Any problems you encounter with any of these schedulers is likely to be an obvious one, such as a problem with permissions or environmental variables.

Perhaps the greatest proof of the utility of these three schedulers is that, despite frequent attempts, desktop versions of them have never really caught on. All three are so well-designed that a GUI offers no advantage over the original command line applications.

The Author

Bruce Byfield is a computer journalist and a freelance writer and editor specializing in free and open source software. In addition to his writing projects, he also teaches live and e-learning courses. In his spare time, Bruce writes about Northwest coast art. You can read more of his work at http://brucebyfield.wordpress.com.

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