CRON(8)                                                   CRON(8)

     NAME
          cron - clock daemon

     SYNOPSIS
          auth/cron [ -c ]

     DESCRIPTION
          Cron executes commands at specified dates and times accord-
          ing to instructions in the files /cron/user/cron.  It runs
          only on an authentication server.  Option -c causes cron to
          create /cron/user and /cron/user/cron for the current user;
          it can be run from any Plan 9 machine.

          Blank lines and lines beginning with # in these files are
          ignored.  Entries are lines with fields

               minute hour day month weekday host command

          Command is a string, which may contain spaces, that is
          passed to an rc(1) running on host for execution.  The first
          five fields are integer patterns for
               minute         0-59
               hour           0-23
               day of month   1-31
               month of year  1-12
               day of week    0-6; 0=Sunday

          The syntax for these patterns is

               time  : '*'
                     | range
               range : number
                     | number '-' number
                     | range ',' range

          Each number must be in the appropriate range.  Hyphens spec-
          ify inclusive ranges of valid times; commas specify lists of
          valid time ranges.

          To run the job, cron calls host and authenticates remote
          execution, equivalent to running rx host command (see
          con(1)). The user's profile is run with $service set to rx.
          If host is set to local, cron will run the command as user
          on the local machine without using rx.

          Cron is not a reliable service.  It skips commands if it
          cannot reach host within two minutes, or if the cron daemon
          is not running at the appropriate time.

     EXAMPLES

     CRON(8)                                                   CRON(8)

          Here is the job that mails system news.

               % cat /cron/upas/cron
               # send system news
               15 8-17,21 * * *    helix     /mail/lib/mailnews
               %

     FILES
          /cron/lock  lock file to prevent multiple crons running

     SOURCE
          /sys/src/cmd/auth/cron.c

     SEE ALSO
          con(1), rc(1)