cron(1M)              Maintenance Commands               cron(1M)



NAME
     cron - clock daemon

SYNOPSIS
     /usr/sbin/cron

AVAILABILITY
     SUNWcsr

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 using the crontab(1)  command.
     Commands which are to be executed only once may be submitted
     using the at(1) command.

     cron only examines crontab or at command  files  during  its
     own  process initialization phase and when the crontab or at
     command is run.  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.  The file /etc/cron.d/FIFO is used  (among  other
     things) as a lock file to prevent the execution of more than
     one instance of cron.

     cron captures the output of  the  job's  stdout  and  stderr
     streams,  and,  if  it is non-empty, mails the output to the
     user.  If the job does not produce output, no mail  is  sent
     to  the  user  (unless  the  job  is an at(1) job and the -m
     option was specified when the job was submitted).

  Setting cron Defaults
     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.

     The PATH for user cron  jobs  can  be  set  using  PATH=  in
     /etc/default/cron.   The  PATH for root cron jobs can be set
     using SUPATH= in /etc/default/cron.  The  security  implica-
     tions  of  setting  PATH and SUPATH should be carefully con-
     sidered.

     Example /etc/default/cron file:

          CRONLOG=YES
          PATH=/usr/bin:/usr/ucb:

     This example enables logging and sets the default PATH  used
     by non-root jobs to /usr/bin:/usr/ucb:.  Root jobs will con-
     tinue to use /usr/sbin:/usr/bin.

     /etc/cron.d/logchecker is a script that checks to see if the
     log  file  has  exceeded  the system ulimit.  If so, the log
     file is moved to /var/cron/olog.

FILES
     /etc/cron.d              main cron directory

     /etc/cron.d/FIFO         used as a lock file

     /etc/default/cron        contains cron default settings

     /var/cron/log            cron history information

     /var/spool/cron          spool area

     /etc/cron.d/logchecker   moves log file to /var/cron/olog if
                              log file exceeds system ulimit.

     /etc/cron.d/queuedefs    queue  description  file  for   at,
                              batch, and cron.

SEE ALSO
     at(1), crontab(1), sh(1), queuedefs(4)

DIAGNOSTICS
     A history  of  all  actions  taken  by  cron  is  stored  in
     /var/cron/log and (possibly) /var/cron/olog.

SunOS 5.4            Last change: 1 Mar 1994