cron

 

---

 
 
 
 Maintenance Commands                                     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 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.
 


ATTRIBUTES
      See attributes(5) for descriptions of the  following  attri-
      butes:
 
      ____________________________________________________________
     |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
     |_____________________________|_____________________________|
     | Availability                | SUNWcsu                     |
     |_____________________________|_____________________________|
 
 


SEE ALSO
      at(1), crontab(1), sh(1), queuedefs(4), attributes(5)
 


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

---