1 .\"/* Copyright 1988,1990,1993,1994 by Paul Vixie
2 .\" * All rights reserved
4 .\" * Distribute freely, except: don't remove my name from the source or
5 .\" * documentation (don't take credit for my work), mark your changes (don't
6 .\" * get me blamed for your possible bugs), don't alter or remove this
7 .\" * notice. May be sold if buildable source is provided to buyer. No
8 .\" * warrantee of any kind, express or implied, is included with this
9 .\" * software; use at your own risk, responsibility for damages (if any) to
10 .\" * anyone resulting from the use of this software rests entirely with the
13 .\" * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
14 .\" * I'll try to keep a version up to date. I can be reached as follows:
15 .\" * Paul Vixie <paul@vix.com> uunet!decwrl!vixie!paul
18 .\" $FreeBSD: src/usr.sbin/cron/crontab/crontab.5,v 1.12.2.8 2002/12/29 16:35:41 schweikh Exp $
25 .Nd tables for driving cron
29 file contains instructions to the
31 daemon of the general form: ``run this command at this time on this date''.
32 Each user has their own crontab, and commands in any given crontab will be
33 executed as the user who owns the crontab. Uucp and News will usually have
34 their own crontabs, eliminating the need for explicitly running
36 as part of a cron command.
38 Blank lines and leading spaces and tabs are ignored. Lines whose first
39 non-space character is a pound-sign (#) are comments, and are ignored.
40 Note that comments are not allowed on the same line as cron commands, since
41 they will be taken to be part of the command. Similarly, comments are not
42 allowed on the same line as environment variable settings.
44 An active line in a crontab will be either an environment setting or a cron
45 command. An environment setting is of the form,
50 where the spaces around the equal-sign (=) are optional, and any subsequent
53 will be part of the value assigned to
57 string may be placed in quotes (single or double, but matching) to preserve
58 leading or trailing blanks.
61 string may also be placed in quote (single or double, but matching)
62 to preserve leading, trailing or inner blanks.
64 Several environment variables are set up
77 line of the crontab's owner.
81 may be overridden by settings in the crontab;
87 variable is sometimes called
104 if it has any reason to send mail as a result of running
105 commands in ``this'' crontab. If
107 is defined (and non-empty), mail is
108 sent to the user so named. If
110 is defined but empty (MAILTO=""), no
111 mail will be sent. Otherwise mail is sent to the owner of the crontab. This
112 option is useful if you decide on
115 .Pa /usr/lib/sendmail
117 your mailer when you install cron --
119 doesn't do aliasing, and UUCP
120 usually doesn't read its mail.
122 The format of a cron command is very much the V7 standard, with a number of
123 upward-compatible extensions. Each line has five time and date fields,
124 followed by a user name
125 (with optional ``:<group>'' and ``/<login-class>'' suffixes)
126 if this is the system crontab file,
127 followed by a command. Commands are executed by
129 when the minute, hour, and month of year fields match the current time,
131 when at least one of the two day fields (day of month, or day of week)
132 matches the current time (see ``Note'' below).
134 examines cron entries once every minute.
135 The time and date fields are:
136 .Bd -literal -offset indent
142 month 1-12 (or names, see below)
143 day of week 0-7 (0 or 7 is Sun, or use names)
146 A field may be an asterisk (*), which always stands for ``first\-last''.
148 Ranges of numbers are allowed. Ranges are two numbers separated
149 with a hyphen. The specified range is inclusive. For example,
150 8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
153 Lists are allowed. A list is a set of numbers (or ranges)
154 separated by commas. Examples: ``1,2,5,9'', ``0-4,8-12''.
156 Step values can be used in conjunction with ranges. Following
157 a range with ``/<number>'' specifies skips of the number's value
158 through the range. For example, ``0-23/2'' can be used in the hours
159 field to specify command execution every other hour (the alternative
160 in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). Steps are
161 also permitted after an asterisk, so if you want to say ``every two
162 hours'', just use ``*/2''.
164 Names can also be used for the ``month'' and ``day of week''
165 fields. Use the first three letters of the particular
166 day or month (case doesn't matter). Ranges or
167 lists of names are not allowed.
169 The ``sixth'' field (the rest of the line) specifies the command to be
171 The entire command portion of the line, up to a newline or %
172 character, will be executed by
177 variable of the cronfile.
178 Percent-signs (%) in the command, unless escaped with backslash
179 (\\), will be changed into newline characters, and all data
180 after the first % will be sent to the command as standard
183 Note: The day of a command's execution can be specified by two
184 fields \(em day of month, and day of week. If both fields are
185 restricted (ie, aren't *), the command will be run when
187 field matches the current time. For example,
189 would cause a command to be run at 4:30 am on the 1st and 15th of each
190 month, plus every Friday.
192 Instead of the first five fields,
193 one of eight special strings may appear:
194 .Bd -literal -offset indent
197 @reboot Run once, at startup.
198 @yearly Run once a year, "0 0 1 1 *".
199 @annually (same as @yearly)
200 @monthly Run once a month, "0 0 1 * *".
201 @weekly Run once a week, "0 0 * * 0".
202 @daily Run once a day, "0 0 * * *".
203 @midnight (same as @daily)
204 @hourly Run once an hour, "0 * * * *".
206 .Sh EXAMPLE CRON FILE
209 # use /bin/sh to run commands, overriding the default set by cron
211 # mail any output to `paul', no matter whose crontab this is
214 # run five minutes after midnight, every day
215 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
216 # run at 2:15pm on the first of every month -- output mailed to paul
217 15 14 1 * * $HOME/bin/monthly
218 # run at 10 pm on weekdays, annoy Joe
219 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
220 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
221 5 4 * * sun echo "run at 5 after 4 every sunday"
227 When specifying day of week, both day 0 and day 7 will be considered Sunday.
231 seem to disagree about this.
233 Lists and ranges are allowed to co-exist in the same field. "1-3,7-9" would
238 cron -- they want to see "1-3" or "7,8,9" ONLY.
240 Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
242 Names of months or days of the week can be specified by name.
244 Environment variables can be set in the crontab. In
249 environment handed to child processes is basically the one from
252 Command output is mailed to the crontab owner
254 can't do this), can be
255 mailed to a person other than the crontab owner (SysV can't do this), or the
256 feature can be turned off and no mail will be sent at all (SysV can't do this
261 commands that can appear in place of the first five fields
264 .An Paul Vixie Aq Mt paul@vix.com
266 If you're in one of the 70-odd countries that observe Daylight
267 Savings Time, jobs scheduled during the rollback or advance will be
268 affected. In general, it's not a good idea to schedule jobs during
271 For US timezones (except parts of IN, AZ, and HI) the time shift occurs at
272 2AM local time. For others, the output of the
276 option can be used to determine the moment of time shift.