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.\"/* Copyright 1988,1990,1993 by Paul Vixie
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.\" * All rights reserved
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.\" *
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.\" * Distribute freely, except: don't remove my name from the source or
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.\" * documentation (don't take credit for my work), mark your changes (don't
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.\" * get me blamed for your possible bugs), don't alter or remove this
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.\" * notice. May be sold if buildable source is provided to buyer. No
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.\" * warrantee of any kind, express or implied, is included with this
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.\" * software; use at your own risk, responsibility for damages (if any) to
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.\" * anyone resulting from the use of this software rests entirely with the
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.\" * user.
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.\" *
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.\" * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
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.\" * I'll try to keep a version up to date. I can be reached as follows:
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.\" * Paul Vixie <paul@vix.com> uunet!decwrl!vixie!paul
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.\" */
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.\"
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.\" $Id: crontab.1,v 2.4 1993/12/31 10:47:33 vixie Exp $
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.\"
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.TH CRONTAB 1 "29 December 1993"
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.UC 4
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.SH NAME
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crontab \- maintain crontab files for individual users (V3)
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.SH SYNOPSIS
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crontab [ -u user ] file
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.br
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crontab [ -u user ] { -l | -r | -e }
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.SH DESCRIPTION
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.I crontab
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is the program used to install, deinstall or list the tables
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used to drive the
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.IR cron (8)
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daemon in Vixie Cron. Each user can have their own crontab, and though
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these are files in /var/spool/cron/crontabs,
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they are not intended to be edited directly.
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.PP
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If the
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.I /etc/cron.allow
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file exists, then you must be listed therein in order to be allowed to use
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this command. If the
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.I /etc/cron.allow
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file does not exist but the
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.I /etc/cron.deny
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file does exist, then you must \fBnot\fR be listed in the
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.I /etc/cron.deny
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file in order to use this command. If neither of these files exists, then
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depending on site-dependent configuration parameters, only the super user
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will be allowed to use this command, or all users will be able to use this
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command. For standard Debian systems, all users may use this command.
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.PP
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If the
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.I -u
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option is given, it specifies the name of the user whose crontab is to be
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tweaked. If this option is not given,
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.I crontab
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examines "your" crontab, i.e., the crontab of the person executing the
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command. Note that
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.IR su (8)
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can confuse
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.I crontab
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and that if you are running inside of
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.IR su (8)
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you should always use the
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.I -u
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option for safety's sake.
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.PP
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The first form of this command is used to install a new crontab from some
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named file or standard input if the pseudo-filename ``-'' is given.
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.PP
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The
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.I -l
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option causes the current crontab to be displayed on standard output. See
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the note under
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.B DEBIAN SPECIFIC
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below.
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.PP
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The
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.I -r
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option causes the current crontab to be removed.
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.PP
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The
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.I -e
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option is used to edit the current crontab using the editor specified by
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the \s-1VISUAL\s+1 or \s-1EDITOR\s+1 environment variables. After you exit
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from the editor, the modified crontab will be installed automatically.
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.SH DEBIAN SPECIFIC
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The "out-of-the-box" behaviour for
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.I crontab -l
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is to display the three line "DO NOT EDIT THIS FILE" header
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that is placed at the
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beginning of the crontab when it is installed. The problem is that
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it makes the sequence
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.PP
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crontab -l | crontab -
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.PP
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non-idempotent -- you keep adding copies of the header. This causes
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pain to scripts that use sed to edit a crontab. Therefore, setting
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the environment variable
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.B CRONTAB_NOHEADER
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to 'Y' will cause the
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.I crontab -l
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command to prune the extraneous header. The reason it was not made the
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default is that at present, some other Debian packages have scripts that
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feed the output of
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.I crontab -l
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to a sed command that just chops the first three lines, assuming it will
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be the unwanted header. This special behaviour
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.B will
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be made the default on a future release (probably for Debian 2.1).
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.SH "SEE ALSO"
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crontab(5), cron(8)
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.SH FILES
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.nf
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/etc/cron.allow
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/etc/cron.deny
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.fi
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.SH STANDARDS
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The
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.I crontab
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command conforms to IEEE Std1003.2-1992 (``POSIX''). This new command syntax
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differs from previous versions of Vixie Cron, as well as from the classic
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SVR3 syntax.
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.SH DIAGNOSTICS
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A fairly informative usage message appears if you run it with a bad command
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line.
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.SH BUGS
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Although cron requires that each entry in a crontab end in a newline
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character, the neither the crontab command nor the cron daemon will
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detect this error. Instead, the crontab will appear load
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normally. However, the command will never run. The best choice is to
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ensure that your crontab has a blank line and the end.
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.SH AUTHOR
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.nf
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Paul Vixie <paul@vix.com>
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