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
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9 .\" * software; use at your own risk, responsibility for damages (if any) to
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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
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.
120 may also be used to direct mail to multiple recipients
121 by separating recipient users with a comma.
124 is defined but empty (MAILTO=""), no
126 Otherwise mail is sent to the owner of the crontab.
128 option is useful if you decide on
131 .Pa /usr/lib/sendmail
133 your mailer when you install cron --
135 does not do aliasing, and UUCP
136 usually does not read its mail.
138 The format of a cron command is very much the V7 standard, with a number of
139 upward-compatible extensions.
140 Each line has five time and date fields,
141 followed by a user name
142 (with optional ``:<group>'' and ``/<login-class>'' suffixes)
143 if this is the system crontab file,
144 followed by a command.
145 Commands are executed by
147 when the minute, hour, and month of year fields match the current time,
149 when at least one of the two day fields (day of month, or day of week)
150 matches the current time (see ``Note'' below).
152 examines cron entries once every minute.
153 The time and date fields are:
154 .Bd -literal -offset indent
160 month 1-12 (or names, see below)
161 day of week 0-7 (0 or 7 is Sun, or use names)
164 A field may be an asterisk (*), which always stands for ``first\-last''.
166 Ranges of numbers are allowed.
167 Ranges are two numbers separated
169 The specified range is inclusive.
171 8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
175 A list is a set of numbers (or ranges)
177 Examples: ``1,2,5,9'', ``0-4,8-12''.
179 Step values can be used in conjunction with ranges.
181 a range with ``/<number>'' specifies skips of the number's value
183 For example, ``0-23/2'' can be used in the hours
184 field to specify command execution every other hour (the alternative
185 in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22'').
187 also permitted after an asterisk, so if you want to say ``every two
188 hours'', just use ``*/2''.
190 Names can also be used for the ``month'' and ``day of week''
192 Use the first three letters of the particular
193 day or month (case does not matter).
195 lists of names are not allowed.
197 The ``sixth'' field (the rest of the line) specifies the command to be
199 The entire command portion of the line, up to a newline or %
200 character, will be executed by
205 variable of the cronfile.
206 Percent-signs (%) in the command, unless escaped with backslash
207 (\\), will be changed into newline characters, and all data
208 after the first % will be sent to the command as standard
211 Note: The day of a command's execution can be specified by two
212 fields \(em day of month, and day of week.
214 restricted (ie, are not *), the command will be run when
216 field matches the current time.
219 would cause a command to be run at 4:30 am on the 1st and 15th of each
220 month, plus every Friday.
222 Instead of the first five fields,
223 one of eight special strings may appear:
224 .Bd -literal -offset indent
227 @reboot Run once, at startup of cron.
228 @yearly Run once a year, "0 0 1 1 *".
229 @annually (same as @yearly)
230 @monthly Run once a month, "0 0 1 * *".
231 @weekly Run once a week, "0 0 * * 0".
232 @daily Run once a day, "0 0 * * *".
233 @midnight (same as @daily)
234 @hourly Run once an hour, "0 * * * *".
235 @every_minute Run once a minute, "*/1 * * * *".
236 @every_second Run once a second.
238 .Sh EXAMPLE CRON FILE
241 # use /bin/sh to run commands, overriding the default set by cron
243 # mail any output to `paul', no matter whose crontab this is
246 # run five minutes after midnight, every day
247 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
248 # run at 2:15pm on the first of every month -- output mailed to paul
249 15 14 1 * * $HOME/bin/monthly
250 # run at 10 pm on weekdays, annoy Joe
251 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
252 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
253 5 4 * * sun echo "run at 5 after 4 every sunday"
259 When specifying day of week, both day 0 and day 7 will be considered Sunday.
263 seem to disagree about this.
265 Lists and ranges are allowed to co-exist in the same field.
271 cron -- they want to see "1-3" or "7,8,9" ONLY.
273 Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
275 Names of months or days of the week can be specified by name.
277 Environment variables can be set in the crontab.
283 environment handed to child processes is basically the one from
286 Command output is mailed to the crontab owner
288 cannot do this), can be
289 mailed to a person other than the crontab owner (SysV cannot do this), or the
290 feature can be turned off and no mail will be sent at all (SysV cannot do this
295 commands that can appear in place of the first five fields
298 .An Paul Vixie Aq paul@vix.com
300 If you are in one of the 70-odd countries that observe Daylight
301 Savings Time, jobs scheduled during the rollback or advance may be
304 is not started with the
307 In general, it is not a good idea to schedule jobs during
310 is not started with the
312 flag, which is enabled by default.
317 For US timezones (except parts of AZ and HI) the time shift occurs at
319 For others, the output of the
323 option can be used to determine the moment of time shift.