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
Page 1 Plan 9 (printed 12/22/24)
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)
Page 2 Plan 9 (printed 12/22/24)