There are two good ways to make your computer execute a command at a specific time of the day: cron and the “at” command. We’re going to take a look at the quick way to do this via the terminal with “at”.
This example will execute the ls command at 3:09pm according to your system’s clock.
When you enter this command you will see a confirmation:
warning: commands will be executed using /bin/sh
job 2 at Fri Aug 31 15:09:00 2012