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



NAME
     cron - clock daemon

SYNOPSIS
     /usr/sbin/cron

DESCRIPTION
     The cron command starts a process that executes commands at
     specified dates and times.  Regularly scheduled commands can
     be specified according to instructions found in crontab
     files in the directory /var/spool/cron/crontabs.  Users can
     submit their own crontab file via the crontab command.  Com-
     mands which are to be executed only once may be submitted
     via the at command.

     cron only examines crontab files and at command files during
     process initialization and when a file changes via the cron-
     tab or at commands.  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 /sbin/rc2.d/S75cron at system
     boot time.  /etc/cron.d/FIFO is used as a lock file to
     prevent the execution of more than one cron.

     To keep a log of all actions taken by cron, CRONLOG=YES (by
     default) must be specified in the /etc/default/cron file.
     If CRONLOG=NO is specified, no logging is done.  Keeping the
     log is a user configurable option since cron usually creates
     huge log files.

     If the line

          INITGROUPS=YES

     is specified in the file /etc/default/cron, cron will call
     initgroups(3C) to enable access to files belonging to all
     groups of which the user is a member (as specified in
     /etc/group).

     If the line

          INITGROUPS=NO

     is specified in the file /etc/default/cron, cron will not
     call initgroups(3C) and will be restricted to the base group
     access permission.  If INITGROUPS is not set in
     /etc/default/cron, disabling the initgroups(3C) call is the
     default.

     The option nofork causes cron not to fork upon initial
     startup.



                        Printed 11/19/92                   Page 1

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



     The option maxrun=# causes cron to change the number of
     simultaneous running jobs that it will allow from 25 (the
     default) to the number specified (less than 10000).

     A special file, 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.

     cron uses syslog(3) to log messages to the system daemon log
     file.

FILES
     /etc/cron.d                         main cron directory
     /etc/default/cron                   used to maintain a log
     /etc/cron.d/FIFO                    used as a lock file
     /var/cron/log                       accounting information
     /var/spool/cron                     spool area
     /var/spool/cron/crontabs/periodic   special root file

SEE ALSO
     syslogd(8).
     at(1), crontab(1), sh(1) in the User's Reference Manual.
     syslog(3) in the Programmer's Reference Manual.

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
























 Page 2                 Printed 11/19/92