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 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 specify inclusive ranges of valid times; commas specify lists of valid time ranges. 

­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
%

SEE ALSO

con(1), rc(1)

Plan 9  —  January 03, 1993