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  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.

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 original 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

       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.

STANDARDS

       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.

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.

       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).

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.