.\"/* Copyright 1988,1990,1993 by Paul Vixie .\" * All rights reserved .\" * .\" * Distribute freely, except: don't remove my name from the source or .\" * documentation (don't take credit for my work), mark your changes (don't .\" * get me blamed for your possible bugs), don't alter or remove this .\" * notice. May be sold if buildable source is provided to buyer. No .\" * warrantee of any kind, express or implied, is included with this .\" * software; use at your own risk, responsibility for damages (if any) to .\" * anyone resulting from the use of this software rests entirely with the .\" * user. .\" * .\" * Send bug reports, bug fixes, enhancements, requests, flames, etc., and .\" * I'll try to keep a version up to date. I can be reached as follows: .\" * Paul Vixie uunet!decwrl!vixie!paul .\" */ .\" .\" $Id: crontab.1,v 2.4 1993/12/31 10:47:33 vixie Exp $ .\" .TH CRONTAB 1 "19 April 2010" .UC 4 .SH NAME crontab \- maintain crontab files for individual users (Vixie Cron) .SH SYNOPSIS crontab [ \-u user ] file .br crontab [ \-u user ] [ \-i ] { \-e | \-l | \-r } .SH DESCRIPTION .I crontab is the program used to install, deinstall or list the tables used to drive the .IR 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. .PP If the .I /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 .I /etc/cron.allow file does not exist but the .I /etc/cron.deny file does exist, then you must \fBnot\fR be listed in the .I /etc/cron.deny file in order to use this command. .PP 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. .PP If both files exist then .I /etc/cron.allow takes precedence. Which means that .I /etc/cron.deny is not considered and your user must be listed in .I /etc/cron.allow in order to be able to use the crontab. .PP 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. .PP If the .I -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, .I crontab examines "your" crontab, i.e., the crontab of the person executing the command. Note that .IR su (8) can confuse .I crontab and that if you are running inside of .IR su (8) you should always use the .I -u option for safety's sake. .PP 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. .PP The .I -l option causes the current crontab to be displayed on standard output. See the note under .B DEBIAN SPECIFIC below. .PP The .I -r option causes the current crontab to be removed. .PP The .I -e option is used to edit the current crontab using the editor specified by the \s-1VISUAL\s+1 or \s-1EDITOR\s+1 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. .PP The .I -i option modifies the \-r option to prompt the user for a 'y/Y' response before actually removing the crontab. .SH DEBIAN SPECIFIC The "out-of-the-box" behaviour for .I 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 .PP crontab \-l | crontab \- .PP 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 .B -l option has been changed to not output such header. You may obtain the original behaviour by setting the environment variable .B CRONTAB_NOHEADER to 'N', which will cause the .I crontab -l command to emit the extraneous header. .SH "SEE ALSO" crontab(5), cron(8) .SH FILES .nf /etc/cron.allow /etc/cron.deny /var/spool/cron/crontabs .fi .PP 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 .I crontab group and configuring .I crontab command with the setgid bid set for that specific group. .SH STANDARDS The .I 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. .SH 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. .SH AUTHOR Paul Vixie is the author of .I 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.