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CRONTAB(1)                                                                                                                                                 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 run‐
       ning 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
 
       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.
 
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