CRONTAB(B)                                             CRONTAB(B)



NAME
       crontab - maintain crontab files for individual users (V3)

SYNOPSIS
       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(n) 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 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. For standard Debian sys-
       tems, all users may 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(u)  can  confuse  crontab  and  that if you are running
       inside of su(u) 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.   The  specified  editor  must edit the file in
       place; any editor that unlinks the file and  recreates  it
       cannot be used.  After you exit from the editor, the modi-
       fied crontab will be installed automatically.

DEBIAN SPECIFIC
       The "out-of-the-box" behaviour for crontab -l is  to  dis-
       play 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(b), cron(n)

FILES
       /etc/cron.allow
       /etc/cron.deny

STANDARDS
       The   crontab  command  conforms  to  IEEE  Std1003.2-1992
       (``POSIX'').  This new command syntax differs from  previ-
       ous  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.


BUGS
       Although cron requires that each entry in a crontab end in
       a newline character, the neither the crontab  command  nor
       the  cron  daemon  will  detect  this  error. Instead, the
       crontab will appear load normally.  However,  the  command
       will  never  run.  The  best choice is to ensure that your
       crontab has a blank line at the end.


AUTHOR
       Paul Vixie <paul@vix.com>



                         29 December 1993              CRONTAB(B)