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cron(8) [plan9 man page]

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

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

cron - The system clock daemon SYNOPSIS
/usr/sbin/cron DESCRIPTION
The cron daemon runs shell commands at specified dates and times. Commands that are to run according to a regular or periodic schedule are found within the crontab files. Commands that are to run once only are found within the at files. You submit crontab and at file entries by using the crontab and at commands. Because the cron process exits only when killed or when the system stops, only one cron daemon should exist on the system at any given time. Normally, you start the cron daemon from within a run command file. During process initialization and when cron detects a change, it examines the crontab and at files. This strategy reduces the overhead of checking for new or changed files at regularly scheduled intervals. The cron command creates a log of its activities. The cron daemon must be started from the system startup scripts because it must begin execution without a login user ID set. The cron daemon starts each job with the following process attributes stored with the job by the invoking process: Login user ID Effective and real user IDs Effective and real group IDs Supplementary groups It also establishes the following attributes from the authentication profile of the account associated with the login user ID of the invok- ing process: Audit control and disposition masks Kernel authorizations DIAGNOSTICS
The at and batch programs will refuse to accept jobs submitted from processes whose login user ID is different from the real user ID. FILES
Specifies the command path. Main cron directory Directory containing the crontab files. List of allowed users. List of denied users His- tory information for cron Queue description file for at, batch, and cron RELATED INFORMATION
Commands: at(1), crontab(1), rc0(8), rc2(8), rc3(8) Files: queuedefs(4) delim off cron(8)
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