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cron(8) [v7 man page]

CRON(8) 						      System Manager's Manual							   CRON(8)

NAME
cron - clock daemon SYNOPSIS
/etc/cron DESCRIPTION
Cron executes commands at specified dates and times according to the instructions in the file /usr/lib/crontab. Since cron never exits, it should only be executed once. This is best done by running cron from the initialization process through the file /etc/rc; see init(8). Crontab consists of lines of six fields each. The fields are separated by spaces or tabs. The first five are integer patterns to specify the minute (0-59), hour (0-23), day of the month (1-31), month of the year (1-12), and day of the week (1-7 with 1=monday). Each of these patterns may contain a number in the range above; two numbers separated by a minus meaning a range inclusive; a list of numbers separated by commas meaning any of the numbers; or an asterisk meaning all legal values. The sixth field is a string that is executed by the Shell at the specified times. A percent character in this field is translated to a new-line character. Only the first line (up to a % or end of line) of the command field is executed by the Shell. The other lines are made available to the command as standard input. Crontab is examined by cron every minute. FILES
/usr/lib/crontab CRON(8)

Check Out this Related Man Page

CRON(8) 						      System Manager's Manual							   CRON(8)

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 authentica- tion 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. 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 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 % SOURCE
/sys/src/cmd/auth/cron.c SEE ALSO
con(1), rc(1) CRON(8)

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