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89c7bb5613
As a followup to the use of login.conf environment vars (other than PATH) in cron, this patch adds PATH (and HOME) to the list of login.conf settings respected. The new logic is as follows: 1. SHELL is always _PATH_BSHELL unless explicitly overridden in the crontab file itself; no other settings are respected. This is unchanged. 2. PATH is taken from the first of: crontab file, login.conf, _PATH_DEFPATH 3. HOME is taken from the first of: crontab file, login.conf, passwd entry, unset 4. The current directory for invoking the command is taken from the crontab file's value of HOME (existing behavior), or the passwd entry, but not anywhere else (so it might not equal HOME if that was set in login.conf). Submitted by: Andrew Gierth <andrew_tao173.riddles.org.uk> Reviewed by: sigsys_gmail.com Differential Revision: https://reviews.freebsd.org/D23597
382 lines
11 KiB
Groff
382 lines
11 KiB
Groff
.\"/* Copyright 1988,1990,1993,1994 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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.\" $FreeBSD$
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.\"
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.Dd March 29, 2020
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.Dt CRONTAB 5
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.Os
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.Sh NAME
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.Nm crontab
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.Nd tables for driving cron
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.Sh DESCRIPTION
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A
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.Nm
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file contains instructions to the
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.Xr cron 8
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daemon of the general form: ``run this command at this time on this date''.
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Each user has their own crontab, and commands in any given crontab will be
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executed as the user who owns the crontab.
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Uucp and News will usually have
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their own crontabs, eliminating the need for explicitly running
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.Xr su 1
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as part of a cron command.
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.Pp
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Blank lines and leading spaces and tabs are ignored.
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Lines whose first
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non-space character is a pound-sign (#) are comments, and are ignored.
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Note that comments are not allowed on the same line as cron commands, since
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they will be taken to be part of the command.
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Similarly, comments are not
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allowed on the same line as environment variable settings.
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.Pp
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An active line in a crontab will be either an environment setting or a cron
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command.
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An environment setting is of the form,
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.Bd -literal
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name = value
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.Ed
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.Pp
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where the spaces around the equal-sign (=) are optional, and any subsequent
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non-leading spaces in
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.Em value
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will be part of the value assigned to
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.Em name .
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The
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.Em value
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string may be placed in quotes (single or double, but matching) to preserve
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leading or trailing blanks.
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The
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.Em name
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string may also be placed in quote (single or double, but matching)
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to preserve leading, trailing or inner blanks.
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.Pp
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Several environment variables are set up
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automatically by the
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.Xr cron 8
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daemon.
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.Ev SHELL
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is set to
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.Pa /bin/sh ,
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and
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.Ev LOGNAME
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and
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.Ev HOME
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are set from the
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.Pa /etc/passwd
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line of the crontab's owner.
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In addition, the environment variables of the
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user's login class will be set from
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.Pa /etc/login.conf.db
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and
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.Pa ~/.login_conf .
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(A setting of
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.Ev HOME
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in the login class will override the value from
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.Pa /etc/passwd ,
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but will not change the current directory when the command is
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invoked, which can only be overridden with an explicit setting of
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.Ev HOME
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within the crontab file itself.)
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If
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.Ev PATH
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is not set by any other means, it is defaulted to
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.Pa /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin .
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.Ev HOME ,
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.Ev PATH
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and
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.Ev SHELL ,
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and any variables set from the login class,
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may be overridden by settings in the crontab;
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.Ev LOGNAME
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may not.
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.Pp
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(Another note: the
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.Ev LOGNAME
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variable is sometimes called
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.Ev USER
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on
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.Bx
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systems...
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On these systems,
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.Ev USER
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will be set also).
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.Pp
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If
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.Xr cron 8
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has any reason to send mail as a result of running commands in
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``this'' crontab, it will respect the following settings which may be
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defined in the crontab (but which are not taken from the login class).
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If
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.Ev MAILTO
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is defined (and non-empty), mail is
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sent to the user so named.
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If
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.Ev MAILFROM
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is defined (and non-empty), its value will be used as the from address.
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.Ev MAILTO
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may also be used to direct mail to multiple recipients
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by separating recipient users with a comma.
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If
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.Ev MAILTO
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is defined but empty (MAILTO=""), no
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mail will be sent.
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Otherwise mail is sent to the owner of the crontab.
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This
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option is useful if you decide on
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.Pa /bin/mail
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instead of
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.Pa /usr/lib/sendmail
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as
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your mailer when you install cron --
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.Pa /bin/mail
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does not do aliasing, and UUCP
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usually does not read its mail.
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.Pp
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The format of a cron command is very much the V7 standard, with a number of
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upward-compatible extensions.
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Each line has five time and date fields,
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followed by a user name
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(with optional ``:<group>'' and ``/<login-class>'' suffixes)
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if this is the system crontab file,
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followed by a command.
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Commands are executed by
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.Xr cron 8
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when the minute, hour, and month of year fields match the current time,
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.Em and
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when at least one of the two day fields (day of month, or day of week)
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matches the current time (see ``Note'' below).
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.Xr cron 8
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examines cron entries once every minute.
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The time and date fields are:
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.Bd -literal -offset indent
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field allowed values
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----- --------------
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minute 0-59
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hour 0-23
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day of month 1-31
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month 1-12 (or names, see below)
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day of week 0-7 (0 or 7 is Sun, or use names)
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.Ed
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.Pp
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A field may be an asterisk (*), which always stands for ``first\-last''.
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.Pp
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Ranges of numbers are allowed.
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Ranges are two numbers separated
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with a hyphen.
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The specified range is inclusive.
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For example,
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8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
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and 11.
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.Pp
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Lists are allowed.
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A list is a set of numbers (or ranges)
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separated by commas.
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Examples: ``1,2,5,9'', ``0-4,8-12''.
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.Pp
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Step values can be used in conjunction with ranges.
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Following
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a range with ``/<number>'' specifies skips of the number's value
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through the range.
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For example, ``0-23/2'' can be used in the hours
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field to specify command execution every other hour (the alternative
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in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22'').
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Steps are
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also permitted after an asterisk, so if you want to say ``every two
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hours'', just use ``*/2''.
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.Pp
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Names can also be used for the ``month'' and ``day of week''
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fields.
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Use the first three letters of the particular
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day or month (case does not matter).
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Ranges or
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lists of names are not allowed.
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.Pp
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The ``sixth'' field (the rest of the line) specifies the command to be
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run.
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One or more command options may precede the command to modify processing
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behavior.
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The entire command portion of the line, up to a newline or %
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character, will be executed by
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.Pa /bin/sh
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or by the shell
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specified in the
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.Ev SHELL
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variable of the cronfile.
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Percent-signs (%) in the command, unless escaped with backslash
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(\\), will be changed into newline characters, and all data
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after the first % will be sent to the command as standard
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input.
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.Pp
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The following command options can be supplied:
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.Bl -tag -width Ds
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.It Fl n
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No mail is sent after a successful run.
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The execution output will only be mailed if the command exits with a non-zero
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exit code.
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The
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.Fl n
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option is an attempt to cure potentially copious volumes of mail coming from
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.Xr cron 8 .
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.It Fl q
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Execution will not be logged.
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.El
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.sp
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Duplicate options are not allowed.
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.Pp
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Note: The day of a command's execution can be specified by two
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fields \(em day of month, and day of week.
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If both fields are
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restricted (ie, are not *), the command will be run when
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.Em either
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field matches the current time.
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For example,
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``30 4 1,15 * 5''
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would cause a command to be run at 4:30 am on the 1st and 15th of each
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month, plus every Friday.
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.Pp
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Instead of the first five fields,
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a line may start with
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.Sq @
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symbol followed either by one of eight special strings or by a numeric value.
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The recognized special strings are:
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.Bd -literal -offset indent
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string meaning
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------ -------
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@reboot Run once, at startup of cron.
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@yearly Run once a year, "0 0 1 1 *".
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@annually (same as @yearly)
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@monthly Run once a month, "0 0 1 * *".
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@weekly Run once a week, "0 0 * * 0".
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@daily Run once a day, "0 0 * * *".
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@midnight (same as @daily)
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@hourly Run once an hour, "0 * * * *".
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@every_minute Run once a minute, "*/1 * * * *".
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@every_second Run once a second.
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.Ed
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.Pp
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The
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.Sq @
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symbol followed by a numeric value has a special notion of running
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a job that many seconds after completion of the previous invocation of
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the job.
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Unlike regular syntax, it guarantees not to overlap two or more
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invocations of the same job during normal cron execution.
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Note, however, that overlap may occur if the job is running when the file
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containing the job is modified and subsequently reloaded.
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The first run is scheduled for the specified number of seconds after cron
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is started or the crontab entry is reloaded.
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.Sh EXAMPLE CRON FILE
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.Bd -literal
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# use /bin/sh to run commands, overriding the default set by cron
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SHELL=/bin/sh
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# mail any output to `paul', no matter whose crontab this is
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MAILTO=paul
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#
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# run five minutes after midnight, every day
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5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
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# run at 2:15pm on the first of every month -- output mailed to paul
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15 14 1 * * $HOME/bin/monthly
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# run at 10 pm on weekdays, annoy Joe
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0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
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23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
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5 4 * * sun echo "run at 5 after 4 every sunday"
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# run at 5 minutes intervals, no matter how long it takes
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@300 svnlite up /usr/src
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# run every minute, suppress logging
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* * * * * -q date
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# run every minute, only send mail if ping fails
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* * * * * -n ping -c 1 freebsd.org
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.Ed
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.Sh SEE ALSO
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.Xr crontab 1 ,
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.Xr cron 8
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.Sh EXTENSIONS
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When specifying day of week, both day 0 and day 7 will be considered Sunday.
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.Bx
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and
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.Tn ATT
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seem to disagree about this.
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.Pp
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Lists and ranges are allowed to co-exist in the same field.
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"1-3,7-9" would
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be rejected by
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.Tn ATT
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or
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.Bx
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cron -- they want to see "1-3" or "7,8,9" ONLY.
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.Pp
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Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
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.Pp
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Names of months or days of the week can be specified by name.
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.Pp
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Environment variables can be set in the crontab.
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In
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.Bx
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or
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.Tn ATT ,
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the
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environment handed to child processes is basically the one from
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.Pa /etc/rc .
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.Pp
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Command output is mailed to the crontab owner
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.No ( Bx
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cannot do this), can be
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mailed to a person other than the crontab owner (SysV cannot do this), or the
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feature can be turned off and no mail will be sent at all (SysV cannot do this
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either).
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.Pp
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All of the
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.Sq @
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directives that can appear in place of the first five fields
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are extensions.
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.Pp
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Command processing can be modified using command options.
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The
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.Sq -q
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option suppresses logging.
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The
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.Sq -n
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option does not mail on successful run.
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.Sh AUTHORS
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.An Paul Vixie Aq Mt paul@vix.com
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.Sh BUGS
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If you are in one of the 70-odd countries that observe Daylight
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Savings Time, jobs scheduled during the rollback or advance may be
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affected if
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.Xr cron 8
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is not started with the
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.Fl s
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flag.
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In general, it is not a good idea to schedule jobs during
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this period if
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.Xr cron 8
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is not started with the
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.Fl s
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flag, which is enabled by default.
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See
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.Xr cron 8
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for more details.
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.Pp
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For US timezones (except parts of AZ and HI) the time shift occurs at
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2AM local time.
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For others, the output of the
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.Xr zdump 8
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program's verbose
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.Fl ( v )
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option can be used to determine the moment of time shift.
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