Provided by: cron_3.0pl1-137ubuntu3_amd64 bug


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


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


       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 existence 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.


       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 original behaviour by setting the
       environment variable CRONTAB_NOHEADER to 'N', which will cause the crontab -l  command  to
       emit the extraneous header.


       crontab(5), cron(8)



       The  files  /etc/cron.allow  and  /etc/cron.deny  if,  they  exist,  must be either world-
       readable, or readable by group ``crontab''. If they are not, then cron will deny access to
       all users until the permissions are fixed.

       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 configuring crontab command with the setgid bid set for that
       specific group.


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


       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.

       The  files  under  /var/spool/cron/crontabs  are  named  based on the user's account name.
       Crontab jobs will not be run for users whose accounts have  been  renamed  either  due  to
       changes  in  the  local system or because they are managed through a central user database
       (external to the system, for example an LDAP directory).


       Paul Vixie <> 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.