http://esm2.imt-mrs.fr/~staffelb/guide_linux/part1/cron.html

minute hour day-of-month month-of-year day-of-week command
Each of the above columns can be in one of the following formats (these examples are for the minute column):

30 Run command at 30 minutes past the hour.

0-59/10 Run command once every 10 minutes, for the entire hour.

15-30 Run command once every minute, from 15 to 30 minutes past the hour.

0,10,50 Run command at 0 minutes past the hour, 10 minutes past the hour, and 50 minutes past the hour.

* Run command once every minute.

Linux/Links/SytemTools/cron (last modified 2008-11-04 07:00:06)