CRONTAB(1)                      General Commands Manual                      CRONTAB(1)

NAME
       crontab - maintain crontab files for individual users (Vixie Cron)

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

DESCRIPTION
       crontab  is  the  program  used to install, deinstall or list the tables used to
       drive the cron(8) daemon in Vixie Cron.  Each user can have their  own  crontab,
       and though these are files in /var/spool/cron/crontabs, they are not intended to
       be edited directly.

       If the /etc/cron.allow file exists, then you must be listed (one user per  line)
       therein in order to be allowed to use this command.  If the /etc/cron.allow file
       does not exist but the /etc/cron.deny file does exist,  then  you  must  not  be
       listed in the /etc/cron.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  both  files  exist  then  /etc/cron.allow takes precedence. Which means that
       /etc/cron.deny is not considered and your user must be listed in /etc/cron.allow
       in order to be able to use the crontab.

       Regardless  of the existance of any of these files, the root administrative user
       is always allowed to setup a crontab.  For standard Debian  systems,  all  users
       may use this command.

       If the -u option is given, it specifies the name of the user whose crontab is to
       be used (when listing) or modified (when editing). If this option is not  given,
       crontab  examines  "your" crontab, i.e., the crontab of the person executing the
       command.  Note that su(8) can confuse crontab and that if you are running inside
       of su(8) 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. See
       the note under DEBIAN SPECIFIC below.

       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. If neither of the environment
       variables is defined, then the default editor /usr/bin/editor is used.

       The -i option modifies the -r option to prompt the user  for  a  'y/Y'  response
       before actually removing the crontab.

DEBIAN SPECIFIC
       The  "out-of-the-box"  behaviour for crontab -l is to display the three line "DO
       NOT EDIT THIS FILE" header that is placed at the beginning of the  crontab  when
       it is installed. The problem is that it makes the sequence

       crontab -l | crontab -

       non-idempotent  --  you  keep  adding  copies of the header. This causes pain to
       scripts that use sed to edit a crontab. Therefore, the default behaviour of  the
       -l  option has been changed to not output such header. You may obtain the origi‐
       nal behaviour by setting the environment variable CRONTAB_NOHEADER to 'N', which
       will cause the crontab -l command to emit the extraneous header.

SEE ALSO
       crontab(5), cron(8)

FILES
       /etc/cron.allow
       /etc/cron.deny
       /var/spool/cron/crontabs

       There  is  one  file  for each user's crontab under the /var/spool/cron/crontabs
       directory. Users are not allowed to edit the files under that directory directly
       to  ensure  that  only users allowed by the system to run periodic tasks can add
       them, and only syntactically correct crontabs will be written  there.   This  is
       enforced  by having the directory writable only by the crontab group and config‐
       uring crontab command with the setgid bid set for that specific group.

STANDARDS
       The crontab command conforms to IEEE Std1003.2-1992 (``POSIX'').  This new  com‐
       mand  syntax  differs  from previous versions of Vixie Cron, as well as from the
       classic SVR3 syntax.

DIAGNOSTICS
       A fairly informative usage message appears if you run  it  with  a  bad  command
       line.

       cron  requires  that  each entry in a crontab end in a newline character. If the
       last entry in a crontab is missing the newline, cron will consider  the  crontab
       (at least partially) broken and refuse to install it.

AUTHOR
       Paul  Vixie  <paul@vix.com>  is  the author of cron and original creator of this
       manual page. This page has also been modified for  Debian  by  Steve  Greenland,
       Javier Fernandez-Sanguino and Christian Kastner.

4th Berkeley Distribution            19 April 2010                           CRONTAB(1)

usage:  crontab [-u user] file
        crontab [ -u user ] [ -i ] { -e | -l | -r }
                (default operation is replace, per 1003.2)
        -e      (edit user's crontab)
        -l      (list user's crontab)
        -r      (delete user's crontab)
        -i      (prompt before deleting user's crontab)