CRON

• CRON job is script/program that is scheduled to run at a specific time
• There is central server cronjobs, and per user cronjobs.

  edit cron job with  $crontab -e 

• from $man 5 crontab

     cron(8) examines cron entries once every minute.  The
         time and date fields are:
  
                field          allowed values
                -----          --------------
                minute         0-59
                hour           0-23
                day of month   1-31
                month          1-12 (or names, see below)
                day of week    0-7 (0 or 7 is Sun, or use names)
  
         A field may be an asterisk (*), which always stands for ``first-last''.

• Short hand + special reboot
  • Allows normal users to schedule non root jobs to run after reboot when cron starts.

       Instead of the first five fields, one  of  eight  special  strings  may
         appear:
  
                string         meaning
                ------         -------
                @reboot        Run once, at startup.
                @yearly        Run once a year, "0 0 1 1 *".
                @annually      (same as @yearly)
                @monthly       Run once a month, "0 0 1 * *".
                @weekly        Run once a week, "0 0 * * 0".
                @daily         Run once a day, "0 0 * * *".
                @midnight      (same as @daily)
                @hourly        Run once an hour, "0 * * * *".

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CategoryLinux