cron(1M) — DG/UX 5.4.2A



cron(1M)                         DG/UX 5.4.2                        cron(1M)


NAME
       cron - clock agent

SYNOPSIS
       /etc/cron

DESCRIPTION
       Cron executes commands at specified dates and times.  You can
       schedule commands on a regular basis according to instructions found
       in crontab files; crontab files are submitted via the crontab
       command.  You may also schedule commands which are to be executed
       only once via the at command.

       NOTE:  You must have permission to create crontab files.

       Commands that are to be executed only once may be submitted via the
       at command.  Because cron never exits, it should be executed only
       once.  This is best done by running cron from the initialization
       process through the rc script mechanism.  (see rc.init(1M)).

       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 can potentially create huge log files.

       You can change the way cron schedules jobs by changing entries in the
       queuedefs file.  The file has two lines, one for the at queue (a.)
       and one for the batch queue (b.):

            a.XjYnZw
            b.XjYnZw

       where:

       X    is the maximum number of jobs allowed to execute simultaneously.
            This cannot be set higher than 25.

       Y    is the nice factor--the job priority number will be raised by
            this amount.  The higher the number, the less attention the job
            gets from the CPU.  The maximum nice factor is 20.

       Z    is how long to wait, in seconds, before trying to reschedule a
            queue request when the job queue is full.

       The default limits are set to work as follows:

            a.4j1n
            b.2j2n90w

       If you increase the job limits, be on guard for a potential impact on
       system performance, especially on smaller machines or machines having
       lots of active users.





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cron(1M)                         DG/UX 5.4.2                        cron(1M)


FILES
       /etc/cron.d            main cron directory
       /etc/cron.d/queuedefs  scheduling information
       /var/cron/log          accounting information (log file)
       /var/spool/cron        spool area
       /etc/default/cron      defaults file

DIAGNOSTICS
       A history of all actions taken by cron is recorded in
       /var/spool/cron/log.

SEE ALSO
       at(1), crontab(1), init(1M), sh(1).

NOTES
       Cron(1M) examines crontab files (located in /var/spool/cron/crontabs)
       and at command files (located in /var/spool/cron/atjobs) only during
       process initialization and when a file changes.  This reduces the
       overhead of checking for new or changed files.

       If the timezone is changed after cron has started, it will be
       necessary to stop and restart cron.  See the admdate man page on how
       to do this.

BUGS
       When it runs out of jobs to do, cron(1M) tries to redo jobs it has
       already done.  This behavior is potentially dangerous, so you should
       always keep it busy, preferably with something like uucleanup or a
       dummy job.  If you are a non-privileged user, an entry similar to the
       following will suffice:

           59 23 * * * echo > /dev/null 2>&1

       This bug originated in AT&T System V.























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