cron

daemon to execute scheduled commands

SYNTAX
      cron

DESCRIPTION
    How to run the cron daemon:
       Cron  should be started from /etc/rc or /etc/rc.local.  
       It will return immediately, so you don't  need  to  start 
       it with '&'.

    What cron does
       Cron  searches /var/spool/cron for crontab files which are
       named after accounts in /etc/passwd;  crontabs  found  are
       loaded  into  memory.  Cron also searches for /etc/crontab
       and the files in the /etc/cron.d/ directory, which are  in
       a  different  format (see crontab(5)).  Cron then wakes up
       every minute, examining all stored crontabs, checking each
       command to see if it should be run in the current minute.

    Mailing output
       When executing commands, any output is mailed to the owner
       of the crontab (or to the user named in the MAILTO 
       environment variable in the crontab, if such exists).

    Modifying a cron job
       Additionally, cron checks each minute to see if its  spool
       directory's  modtime  (or the modtime on /etc/crontab) has
       changed, and if it has, cron will then examine the modtime
       on all crontabs and reload those which have changed.  Thus
       cron need not be restarted whenever a crontab file is mod­
       ified.   Note that the crontab(1) command updates the mod­
       time of the spool directory whenever it changes a crontab. 

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Related commands:

builtin - Run a shell builtin
crontab - Schedule a command to run at a later time
chroot - Run a command with a different root directory
exec - Execute a command
if - Conditionally perform a command
nohup - Run a command immune to hangups
su - Run a command with substitute user and group id
watch - Execute/display a program periodically
.period - Run commands from a file

Equivalent Windows NT commands:

NET START Task Scheduler - Start the task Schedule service
AT - Schedule a command to run at a later time