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fe590ffe40
Specifically, import the diff from commit e745bd4c10ab to commit 83563783cc2 in https://github.com/vixie/cron.git My sole motivation is changing to the common MIT license. The old license, especially the "buildable source" clause, is unfriendly for commercial users of this code. Simply changing the license without importing [most of] the code accompanying that license seemed legally dubious. The most regrettable change is losing Paul's uucp path. I partially atone for this loss by restoring the upstream $Id$ tags, since $FreeBSD$ is no longer useful. This is [intended to be] a complete list of the functional changes in this commit. Some changes were made so that we could consider vixie cron to be our upstream and reduce our diffs against it, while others were simply a good idea. - main() - use putenv instead of setenv for PATH - open_pidfile no longer needs snprintf to build pidfile - crontab main() - abort() on impossible errors - check for truncation when building strings with snprintf - getdtablesize() -> sysconf(_SC_OPEN_MAX) These changes were not taken from upstream's 4.0 diff because they [could] actually change behavior. Some of them might be beneficial, but should be taken separately. - config.h - sendmail args: remove -oi and add -or0s - call setlocale(LC_ALL, "") at the top of main() - acquire_daemonlock - we already use pidfile - cast getpid(), uid_t, and gid_t to long for printf - remove unnecessary braces - I consider them beneficial - BSDi support - glue_strings() - use snprintf(), as we often already did MFC after: on demand Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D40260
383 lines
11 KiB
Groff
383 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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.\"
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.\"Copyright (c) 1997 by Internet Software Consortium
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.\"
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.\"Permission to use, copy, modify, and distribute this software for any
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.\"purpose with or without fee is hereby granted, provided that the above
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.\"copyright notice and this permission notice appear in all copies.
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.\"
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.\"THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
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.\"ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
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.\"OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
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.\"CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
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.\"DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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.\"PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
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.\"ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
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.\"SOFTWARE.
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.\"
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.\" $Id: crontab.5,v 1.2 1998/08/14 00:32:38 vixie Exp $
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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 and lists are also 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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