CRON(8) 						      System Manager's Manual							   CRON(8)

NAME

       cron - clock daemon

SYNOPSIS

       auth/cron [-c]

DESCRIPTION

       Cron executes commands at specified dates and times according to instructions in the files /cron/user/cron.  It runs only on an authentica-
       tion 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 specify 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.

       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

       Here is the job that mails system news.

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

SOURCE

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

SEE ALSO

       con(1), rc(1)

																	   CRON(8)