Cron Jobs

Edit the cron jobs file by running the command: crontab -e

Setting up a Cron job

  * * * * *   <command to execute>
  │ │ │ │ │
  │ │ │ │ │
  │ │ │ │ └───── day of week (0 - 6) (0 to 6 are Sunday to Saturday, or use names; 7 is Sunday, the same as 0)
  │ │ │ └────────── month (1 - 12)
  │ │ └─────────────── day of month (1 - 31)
  │ └──────────────────── hour (0 - 23)
  └───────────────────────── min (0 - 59)

The asterisk indicates that the corn expression matches for all values of the field. E.g. using an asterisk in the 4th field (month) indicates every month.

Other special characters

Slash ( / )

Slashes describe increments of ranges. For example 3-59/15 in the 1st field (minutes) indicate the third minute of the hour and every 15 minutes thereafter. The form "*/..." is equivalent to the form "first-last/...", that is, an increment over the largest possible range of the field.

Comma ( , )

Commas are used to separate items of a list. For example, using "MON,WED,FRI" in the 5th field (day of the week) means Mondays, Wednesdays, and Fridays.

Hyphen ( - )

Hyphens define ranges. For example, 2000-2010 indicates every year between 2000 and 2010 AD, inclusive.

Percent ( % )

Percent-signs (%) in the command, unless escaped with a backslash (), are changed into newline characters, and all data after the first % are sent to the command as standard input.

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