Crontab: Difference between revisions

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A crontab file has five fields for specifying day , date and time  followed by the command to be run at that interval.
A crontab file has five fields for specifying day , date and time  followed by the command to be run at that interval.
<pre>
<pre>
*     *  *  *   *  command to be executed
  *   *  *  *   *  command to be executed
-     -   -   -   -
  -   -   -   -   -
|     |     |     |     |
  |   |   |   |   |
|     |     |     |     +----- day of week (0 - 6) (Sunday=0)
  |   |   |   |   +----- day of week (0 - 6) (Sunday=0)
|     |     |     +------- month (1 - 12)
  |   |   |   +------- month (1 - 12)
|     |     +--------- day of month (1 - 31)
  |   |   +--------- day of month (1 - 31)
|     +----------- hour (0 - 23)
  |   +----------- hour (0 - 23)
+------------- min (0 - 59)
  +------------- min (0 - 59)
</pre>
</pre>



Revision as of 12:34, 10 August 2008

Crontab is the equivelant of the scheduler in Windows.

Crontab Commands

  crontab -e   Edit your crontab file, or create one if it doesn't already exist.
  crontab -l   Display your crontab file.
  crontab -r   Remove your crontab file.
  crontab -v   Display the last time you edited your crontab file.


Crontab File

A crontab file has five fields for specifying day , date and time followed by the command to be run at that interval.

   *   *   *   *   *  command to be executed
   -   -   -   -   -
   |   |   |   |   |
   |   |   |   |   +----- day of week (0 - 6) (Sunday=0)
   |   |   |   +------- month (1 - 12)
   |   |   +--------- day of month (1 - 31)
   |   +----------- hour (0 - 23)
   +------------- min (0 - 59)

Disable Email

By default cron jobs sends a email to the user account executing the cronjob. If this is not needed put the following command At the end of the cron job line .

>/dev/null 2>&1