CRON(1M-SysV)       RISC/os Reference Manual        CRON(1M-SysV)



NAME
     cron - clock daemon

SYNOPSIS
     /etc/cron [nofork] [maxrun=#]

DESCRIPTION
     cron executes commands at specified dates and times.  The
     option nofork causes cron not to fork upon initial startup.
     The option maxrun=# causes cron change the number of simul-
     taneous running jobs that it will allow from 25 (the
     default) to the number specified (less than 10000).  Regu-
     larly scheduled commands can be specified according to
     instructions found in crontab files in the directory
     /usr/spool/cron/crontabs.  A special file, called periodic,
     owned by root (but not the root crontab file), is also
     located in the /usr/spool/cron/crontabs directory.  This
     file is intended to run periodic commands on behalf of the
     kernel rather than the root user. It must not be modified or
     deleted, nor can it be submitted via the crontab(1) command;
     it is started when cron is initialized.  Users can submit
     their own crontab file via the crontab(1) command.  Commands
     which are to be executed only once may be submitted via the
     at(1) command.

     cron only examines crontab files and at command files during
     process initialization and when a file changes via crontab
     or at.  This reduces the overhead of checking for new or
     changed files at regularly scheduled intervals.

     Since cron never exits, it should be executed only once.
     This is done routinely through /etc/rc2.d/S75cron at system
     boot time.  /usr/lib/cron/FIFO is used as a lock file to
     prevent the execution of more than one cron.

FILES
     /usr/lib/cron                 main cron directory
     /usr/lib/cron/FIFO            used as a lock file
     /usr/lib/cron/log             accounting information
     /usr/spool/cron               spool area
     /usr/spool/cron/crontabs/periodic
                                   special root file

SEE ALSO
     at(1), crontab(1), sh(1) in the User's Reference Manual.

DIAGNOSTICS
     A history of all actions taken by cron are recorded in
     /usr/lib/cron/log.






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