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
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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
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,
49 where the spaces around the equal-sign (=) are optional, and any subsequent
52 will be part of the value assigned to
56 string may be placed in quotes (single or double, but matching) to preserve
57 leading or trailing blanks.
59 Several environment variables are set up
72 line of the crontab's owner.
76 may be overridden by settings in the crontab;
82 variable is sometimes called
97 if it has any reason to send mail as a result of running
98 commands in ``this'' crontab. If
100 is defined (and non-empty), mail is
101 sent to the user so named. If
103 is defined but empty (MAILTO=""), no
104 mail will be sent. Otherwise mail is sent to the owner of the crontab. This
105 option is useful if you decide on
108 .Pa /usr/lib/sendmail
110 your mailer when you install cron --
112 doesn't do aliasing, and UUCP
113 usually doesn't read its mail.
115 The format of a cron command is very much the V7 standard, with a number of
116 upward-compatible extensions. Each line has five time and date fields,
117 followed by a user name
118 (with optional ``:<group>'' and ``/<login-class>'' suffixes)
119 if this is the system crontab file,
120 followed by a command. Commands are executed by
122 when the minute, hour, and month of year fields match the current time,
124 when at least one of the two day fields (day of month, or day of week)
125 match the current time (see ``Note'' below).
127 examines cron entries once every minute.
128 The time and date fields are:
129 .Bd -literal -offset indent
135 month 1-12 (or names, see below)
136 day of week 0-7 (0 or 7 is Sun, or use names)
139 A field may be an asterisk (*), which always stands for ``first\-last''.
141 Ranges of numbers are allowed. Ranges are two numbers separated
142 with a hyphen. The specified range is inclusive. For example,
143 8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
146 Lists are allowed. A list is a set of numbers (or ranges)
147 separated by commas. Examples: ``1,2,5,9'', ``0-4,8-12''.
149 Step values can be used in conjunction with ranges. Following
150 a range with ``/<number>'' specifies skips of the number's value
151 through the range. For example, ``0-23/2'' can be used in the hours
152 field to specify command execution every other hour (the alternative
153 in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). Steps are
154 also permitted after an asterisk, so if you want to say ``every two
155 hours'', just use ``*/2''.
157 Names can also be used for the ``month'' and ``day of week''
158 fields. Use the first three letters of the particular
159 day or month (case doesn't matter). Ranges or
160 lists of names are not allowed.
162 The ``sixth'' field (the rest of the line) specifies the command to be
164 The entire command portion of the line, up to a newline or %
165 character, will be executed by
170 variable of the cronfile.
171 Percent-signs (%) in the command, unless escaped with backslash
172 (\\), will be changed into newline characters, and all data
173 after the first % will be sent to the command as standard
176 Note: The day of a command's execution can be specified by two
177 fields \(em day of month, and day of week. If both fields are
178 restricted (ie, aren't *), the command will be run when
180 field matches the current time. For example,
183 would cause a command to be run at 4:30 am on the 1st and 15th of each
184 month, plus every Friday.
185 .Sh EXAMPLE CRON FILE
188 # use /bin/sh to run commands, overriding the default set by cron
190 # mail any output to `paul', no matter whose crontab this is
193 # run five minutes after midnight, every day
194 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
195 # run at 2:15pm on the first of every month -- output mailed to paul
196 15 14 1 * * $HOME/bin/monthly
197 # run at 10 pm on weekdays, annoy Joe
198 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
199 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
200 5 4 * * sun echo "run at 5 after 4 every sunday"
206 When specifying day of week, both day 0 and day 7 will be considered Sunday.
207 BSD and ATT seem to disagree about this.
209 Lists and ranges are allowed to co-exist in the same field. "1-3,7-9" would
210 be rejected by ATT or BSD cron -- they want to see "1-3" or "7,8,9" ONLY.
212 Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
214 Names of months or days of the week can be specified by name.
216 Environment variables can be set in the crontab. In BSD or ATT, the
217 environment handed to child processes is basically the one from
220 Command output is mailed to the crontab owner (BSD can't do this), can be
221 mailed to a person other than the crontab owner (SysV can't do this), or the
222 feature can be turned off and no mail will be sent at all (SysV can't do this
225 .An Paul Vixie Aq paul@vix.com
227 If you're in one of the 70-odd countries that observe Daylight
228 Savings Time, jobs scheduled during the rollback or advance will be
229 affected. In general, it's not a good idea to schedule jobs during
232 For US timezones (except parts of IN, AZ, and HI) the time shift occurs at
233 2AM local time. For others, the output of the
237 option can be used to determine the moment of time shift.
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