crontab

Schedule a command to run at a later time

SYNTAX
      crontab [ -u user ] file
      crontab [ -u user ] { -l | -r | -e }

DESCRIPTION
       Crontab is the program used to install, deinstall or  list
       the tables used to drive the cron daemon in Vixie Cron.
       Each user can have their own crontab, and though these are
       files  in  /var,  they  are  not  intended  to  be  edited
       directly.

       If the allow file exists, then you must be listed  therein
       in  order to be allowed to use this command.  If the allow
       file does not exist but the deny file does exist, then you
       must  not  be listed in the deny file in order to use this
       command.  If neither of these files exists, then depending
       on site-dependent configuration parameters, only the super
       user will be allowed to use this  command,  or  all  users
       will be able to use this command.

       If  the  -u  option is given, it specifies the name of the
       user whose crontab is to be tweaked.  If  this  option  is
       not  given,  crontab  examines  "your"  crontab, i.e., the
       crontab of the person executing the  command.   Note  that
       su  can  confuse  crontab  and  that if you are running
       inside of su you should always use the  -u  option  for
       safety's sake.

       The  first  form  of this command is used to install a new
       crontab from some named file  or  standard  input  if  the
       pseudo-filename `-' is given.

       The  -l  option causes the current crontab to be displayed
       on standard output.

       The -r option causes the current crontab to be removed.

       The -e option is used to edit the  current  crontab  using
       the  editor  specified by the VISUAL or EDITOR environment
       variables.  After you exit from the editor,  the  modified
       crontab will be installed automatically.

"Wisdom is the power to put our time and our knowledge to the proper use" - Thomas J. Watson

Related commands:

cron - daemon to execute scheduled commands
nice - Change job scheduling priority
builtin - Run a shell builtin
chroot - Run a command with a different root directory
exec - Execute a command
nohup - Run a command immune to hangups
.source - Run commands from a file
su - Run a command with substitute user and group id
watch - Execute/display a program periodically