Plan 9 - man page for cron (plan9 section 8)
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cron - clock daemon
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 cre-
ate /cron/user and /cron/user/cron for the current user; it can be run from any Plan 9
Blank lines and lines beginning with # in these files are ignored. Entries are lines with
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
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 : 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 min-
utes, or if the cron daemon is not running at the appropriate time.
Here is the job that mails system news.
% cat /cron/upas/cron
# send system news
15 8-17, 21 *** helix /mail/lib/mailnews
All times are GMT -4. The time now is 07:09 PM.