ref: b76a78c1a1973d62ff32c030e29b3ffcc560e50d
dir: /sys/man/8/cron/
.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 . If .I host is set to .BR local , .I cron will run the command as .I user on the local machine without using .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 FILES .TF /cron/lock .TP .B /cron/lock lock file to prevent multiple .IR cron s running .SH SOURCE .B /sys/src/cmd/auth/cron.c .SH "SEE ALSO" .IR con (1), .IR rc (1)