How would I get a cron job to run every 30 minutes?

Question

I'm looking to add a crontab entry to execute a script every 30 minutes, on the hour and 30 minutes past the hour or something close. I have the following, but it doesn't seem to run on 0.

*/30 * * * *

What string do I need to use?

The cron is running on OSX.

Answer 1

Do:

0,30 * * * * your_command

Cheers, V.

Answer 2

Try this:

0,30 * * * * your command goes here

According to the official Mac OS X crontab(5) manpage, the / syntax is supported. Thus, to figure out why it wasn't working for you, you'll need to look at the logs for cron. In those logs, you should find a clear failure message.

Note: Mac OS X appears to use Vixie Cron, the same as Linux and the BSDs.

Answer 3

You mention you are using OS X- I have used cronnix in the past. It's not as geeky as editing it yourself, but it helped me learn what the columns are in a jiffy. Just a thought.

Answer 4

If your cron job is running on Mac OS X only, you may want to consider using launchd instead. Apple will be using launchd instead of cron going forward.

launchd Wikipedia entry

Getting Started with launchd (official Apple docs)