TH CRON 8
SH NAME
cron \- clock daemon
SH SYNOPSIS
B auth/cron
[
B -c
]
SH DESCRIPTION
I Cron
executes commands at specified dates and times according
to instructions in the files
BI /cron/ user /cron\f1.
It runs only on an authentication server.
Option
B -c
causes
I cron
to create
BI /cron/ user
and
BI /cron/ user /cron
for the current user;
it can be run from any Plan 9 machine.
PP
Blank lines and lines beginning with
B #
in these files are ignored.
Entries are lines with fields
IP
I
minute hour day month weekday host command
PP
I Command
is a string, which may contain spaces, that is passed to an
IR rc (1)
running on
I host
for execution.
The first five fields are integer patterns for
PD0
RS
TP \w'month\ of\ year\ \ 'u
minute
0\-59
TP
hour
0\-23
TP
day of month
1\-31
TP
month of year
1\-12
TP
day of week
0\-6; 0=Sunday
PD
RE
PP
The syntax for these patterns is
IP
EX
time : '*'
| range
range : number
| number '-' number
| range ',' range
EE
PP
Each number must be in the appropriate range.
Hyphens specify inclusive ranges of valid times;
commas specify lists of valid time ranges.
PP
To run the job,
I cron
calls
I host
and authenticates remote execution, equivalent to running
B rx
I host
I command
(see
IR con (1)).
The user's profile is run with
B $service
set to
BR rx .
PP
I Cron
is not a reliable service.
It skips commands if it cannot reach
I host
within two minutes, or if the
I cron
daemon is
not running at the appropriate time.
SH EXAMPLES
Here is the job that mails system news.
IP
EX
% cat /cron/upas/cron
# send system news
15 8-17, 21 *** helix /mail/lib/mailnews
%
EE
SH SOURCE
B /sys/src/cmd/auth/cron.c
SH "SEE ALSO"
IR con (1),
IR rc (1)
