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
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.
34 Uucp and News will usually have
35 their own crontabs, eliminating the need for explicitly running
37 as part of a cron command.
39 Blank lines and leading spaces and tabs are ignored.
41 non-space character is a pound-sign (#) are comments, and are ignored.
42 Note that comments are not allowed on the same line as cron commands, since
43 they will be taken to be part of the command.
44 Similarly, comments are not
45 allowed on the same line as environment variable settings.
47 An active line in a crontab will be either an environment setting or a cron
49 An environment setting is of the form,
54 where the spaces around the equal-sign (=) are optional, and any subsequent
57 will be part of the value assigned to
61 string may be placed in quotes (single or double, but matching) to preserve
62 leading or trailing blanks.
65 string may also be placed in quote (single or double, but matching)
66 to preserve leading, trailing or inner blanks.
68 Several environment variables are set up
77 .Pa /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin ,
84 line of the crontab's owner.
89 may be overridden by settings in the crontab;
95 variable is sometimes called
113 if it has any reason to send mail as a result of running
114 commands in ``this'' crontab.
117 is defined (and non-empty), mail is
118 sent to the user so named.
121 is defined (and non-empty), its value will be used as the from address.
123 may also be used to direct mail to multiple recipients
124 by separating recipient users with a comma.
127 is defined but empty (MAILTO=""), no
129 Otherwise mail is sent to the owner of the crontab.
131 option is useful if you decide on
134 .Pa /usr/lib/sendmail
136 your mailer when you install cron --
138 does not do aliasing, and UUCP
139 usually does not read its mail.
141 The format of a cron command is very much the V7 standard, with a number of
142 upward-compatible extensions.
143 Each line has five time and date fields,
144 followed by a user name
145 (with optional ``:<group>'' and ``/<login-class>'' suffixes)
146 if this is the system crontab file,
147 followed by a command.
148 Commands are executed by
150 when the minute, hour, and month of year fields match the current time,
152 when at least one of the two day fields (day of month, or day of week)
153 matches the current time (see ``Note'' below).
155 examines cron entries once every minute.
156 The time and date fields are:
157 .Bd -literal -offset indent
163 month 1-12 (or names, see below)
164 day of week 0-7 (0 or 7 is Sun, or use names)
167 A field may be an asterisk (*), which always stands for ``first\-last''.
169 Ranges of numbers are allowed.
170 Ranges are two numbers separated
172 The specified range is inclusive.
174 8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
178 A list is a set of numbers (or ranges)
180 Examples: ``1,2,5,9'', ``0-4,8-12''.
182 Step values can be used in conjunction with ranges.
184 a range with ``/<number>'' specifies skips of the number's value
186 For example, ``0-23/2'' can be used in the hours
187 field to specify command execution every other hour (the alternative
188 in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22'').
190 also permitted after an asterisk, so if you want to say ``every two
191 hours'', just use ``*/2''.
193 Names can also be used for the ``month'' and ``day of week''
195 Use the first three letters of the particular
196 day or month (case does not matter).
198 lists of names are not allowed.
200 The ``sixth'' field (the rest of the line) specifies the command to be
202 The entire command portion of the line, up to a newline or %
203 character, will be executed by
208 variable of the cronfile.
209 Percent-signs (%) in the command, unless escaped with backslash
210 (\\), will be changed into newline characters, and all data
211 after the first % will be sent to the command as standard
214 Note: The day of a command's execution can be specified by two
215 fields \(em day of month, and day of week.
217 restricted (ie, are not *), the command will be run when
219 field matches the current time.
222 would cause a command to be run at 4:30 am on the 1st and 15th of each
223 month, plus every Friday.
225 Instead of the first five fields,
226 a line may start with
228 symbol followed either by one of eight special strings or by a numeric value.
229 The recognized special strings are:
230 .Bd -literal -offset indent
233 @reboot Run once, at startup of cron.
234 @yearly Run once a year, "0 0 1 1 *".
235 @annually (same as @yearly)
236 @monthly Run once a month, "0 0 1 * *".
237 @weekly Run once a week, "0 0 * * 0".
238 @daily Run once a day, "0 0 * * *".
239 @midnight (same as @daily)
240 @hourly Run once an hour, "0 * * * *".
241 @every_minute Run once a minute, "*/1 * * * *".
242 @every_second Run once a second.
247 symbol followed by a numeric value has a special notion of running
248 a job that many seconds after completion of the previous invocation of
250 Unlike regular syntax, it guarantees not to overlap two or more
251 invocations of the same job during normal cron execution.
252 Note, however, that overlap may occur if the job is running when the file
253 containing the job is modified and subsequently reloaded.
254 The first run is scheduled for the specified number of seconds after cron
255 is started or the crontab entry is reloaded.
256 .Sh EXAMPLE CRON FILE
259 # use /bin/sh to run commands, overriding the default set by cron
261 # mail any output to `paul', no matter whose crontab this is
264 # run five minutes after midnight, every day
265 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
266 # run at 2:15pm on the first of every month -- output mailed to paul
267 15 14 1 * * $HOME/bin/monthly
268 # run at 10 pm on weekdays, annoy Joe
269 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
270 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
271 5 4 * * sun echo "run at 5 after 4 every sunday"
272 # run at 5 minutes intervals, no matter how long it takes
273 @300 svnlite up /usr/src
279 When specifying day of week, both day 0 and day 7 will be considered Sunday.
283 seem to disagree about this.
285 Lists and ranges are allowed to co-exist in the same field.
291 cron -- they want to see "1-3" or "7,8,9" ONLY.
293 Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
295 Names of months or days of the week can be specified by name.
297 Environment variables can be set in the crontab.
303 environment handed to child processes is basically the one from
306 Command output is mailed to the crontab owner
308 cannot do this), can be
309 mailed to a person other than the crontab owner (SysV cannot do this), or the
310 feature can be turned off and no mail will be sent at all (SysV cannot do this
315 directives that can appear in place of the first five fields
318 .An Paul Vixie Aq Mt paul@vix.com
320 If you are in one of the 70-odd countries that observe Daylight
321 Savings Time, jobs scheduled during the rollback or advance may be
324 is not started with the
327 In general, it is not a good idea to schedule jobs during
330 is not started with the
332 flag, which is enabled by default.
337 For US timezones (except parts of AZ and HI) the time shift occurs at
339 For others, the output of the
343 option can be used to determine the moment of time shift.
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