CRONTAB(1)                                                          CRONTAB(1)


NAME
     crontab - user crontab file

SYNOPSIS
     crontab [file]
     crontab -r [file]
     crontab -l [file]
     crontab -e [file]

DESCRIPTION
     crontab copies the specified file, or standard input if no file is
     specified, into a directory that holds all users' crontabs.  The -r
     option removes a user's crontab from the crontab directory.  crontab -l
     will list the crontab file for the invoking user. The -e option spawns an
     editor which contains the user's current crontab (as output by crontab
     -l), and automatically updates the crontab when the user saves the file
     and exits the editor. The name of the editor to invoke can be specified
     by the environment variable VISUAL or EDITOR; else, vi is used by
     default.

     Normal users may only remove, list, or edit their own crontab files which
     is the default.  The superuser (root) may supply any username following
     -r, -l, or -e to remove, list, or edit that user's crontab.

     If the file /etc/cron.d/cron.allow exists, only users whose names appear
     in the file are permitted to use crontab. This restriction applies to all
     users, including root.  If that file does not exist, the file
     /etc/cron.d/cron.deny is checked to determine if the user should be
     denied access to crontab. If neither file exists, only root is allowed to
     submit a job.  If cron.allow does not exist and cron.deny exists but is
     empty, global usage is permitted.  The allow/deny files consist of one
     user name per line.

     A crontab file consists of lines of six fields each.  The fields are
     separated by spaces or tabs.  The first five are integer patterns that
     specify the following:

          minute (0-59),
          hour (0-23),
          day of the month (1-31),
          month of the year (1-12),
          day of the week (0-6 with 0=Sunday).

     Each of these patterns may be either an asterisk  (meaning all legal
     values) or a list of elements separated by commas.  An element is either
     a number or two numbers separated by a minus sign (meaning an inclusive
     range).  Note that the specification of days may be made by two fields
     (day of the month and day of the week).  If both are specified as a list
     of elements, both are adhered to.  For example, 0 0 1,15 * 1 would run a
     command on the first and fifteenth of each month, as well as on every
     Monday.  To specify days by only one field, the other field should be set
     to * (for example, 0 0 * * 1 would run a command only on Mondays).


     The sixth field of a line in a crontab file is a string that is executed
     by the shell at the specified times.  A percent character in this field
     (unless escaped by \) is translated to a new-line character.  Only the
     first line (up to a % or end of line) of the command field is executed by
     the shell.  The other lines are made available to the command as standard
     input.

     The shell is invoked from your $HOME directory with an arg0 of sh.  Users
     who desire to have their .profile executed must explicitly do so in the
     crontab file.  Cron supplies a default environment for every shell,
     defining HOME, LOGNAME, USER, SHELL(=/bin/sh),
     PATH(=/usr/sbin:/usr/bsd:/sbin:/usr/bin:/etc:/usr/etc:/usr/bin/X11), and
     TZ.

     If you do not redirect the standard output and standard error of your
     commands, any generated output or errors will be mailed to you.

     Any errors encountered while parsing the crontab file (or stdin) will
     cause crontab to abort with no changes being made to any existing
     crontab.

FILES
     /etc/cron.d                main cron directory
     /var/spool/cron/crontabs   spool area
     /var/cron/log              accounting information
     /etc/cron.d/cron.allow     optional list of allowed users
     /etc/cron.d/cron.deny      list of denied users
     /etc/cron.d/FIFO           to communicate crontab changes to cron

SEE ALSO
     sh(1), cron(1M)

NOTES
     If you inadvertently enter the crontab command with no argument(s), you
     may exit without overwriting the existing crontab entry either by
     generating an interrupt (typically by typing ^C or DEL), or by providing
     empty input (typically by typing ^D on the first empty line).

     If a job is scheduled during the 'witching hour' - the time during a
     change from the main to alternate time zone, the job will either be run
     once (if the actual time exists twice) or not at all (if the actual time
     never exists).


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