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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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
81 line of the crontab's owner.
85 may be overridden by settings in the crontab;
91 variable is sometimes called
108 if it has any reason to send mail as a result of running
109 commands in ``this'' crontab.
112 is defined (and non-empty), mail is
113 sent to the user so named.
115 may also be used to direct mail to multiple recipients
116 by seperating recipient users with a comma.
119 is defined but empty (MAILTO=""), no
121 Otherwise mail is sent to the owner of the crontab.
123 option is useful if you decide on
126 .Pa /usr/lib/sendmail
128 your mailer when you install cron --
130 does not do aliasing, and UUCP
131 usually does not read its mail.
133 The format of a cron command is very much the V7 standard, with a number of
134 upward-compatible extensions.
135 Each line has five time and date fields,
136 followed by a user name
137 (with optional ``:<group>'' and ``/<login-class>'' suffixes)
138 if this is the system crontab file,
139 followed by a command.
140 Commands are executed by
142 when the minute, hour, and month of year fields match the current time,
144 when at least one of the two day fields (day of month, or day of week)
145 matches the current time (see ``Note'' below).
147 examines cron entries once every minute.
148 The time and date fields are:
149 .Bd -literal -offset indent
155 month 1-12 (or names, see below)
156 day of week 0-7 (0 or 7 is Sun, or use names)
159 A field may be an asterisk (*), which always stands for ``first\-last''.
161 Ranges of numbers are allowed.
162 Ranges are two numbers separated
164 The specified range is inclusive.
166 8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
170 A list is a set of numbers (or ranges)
172 Examples: ``1,2,5,9'', ``0-4,8-12''.
174 Step values can be used in conjunction with ranges.
176 a range with ``/<number>'' specifies skips of the number's value
178 For example, ``0-23/2'' can be used in the hours
179 field to specify command execution every other hour (the alternative
180 in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22'').
182 also permitted after an asterisk, so if you want to say ``every two
183 hours'', just use ``*/2''.
185 Names can also be used for the ``month'' and ``day of week''
187 Use the first three letters of the particular
188 day or month (case does not matter).
190 lists of names are not allowed.
192 The ``sixth'' field (the rest of the line) specifies the command to be
194 The entire command portion of the line, up to a newline or %
195 character, will be executed by
200 variable of the cronfile.
201 Percent-signs (%) in the command, unless escaped with backslash
202 (\\), will be changed into newline characters, and all data
203 after the first % will be sent to the command as standard
206 Note: The day of a command's execution can be specified by two
207 fields \(em day of month, and day of week.
209 restricted (ie, are not *), the command will be run when
211 field matches the current time.
214 would cause a command to be run at 4:30 am on the 1st and 15th of each
215 month, plus every Friday.
217 Instead of the first five fields,
218 one of eight special strings may appear:
219 .Bd -literal -offset indent
222 @reboot Run once, at startup.
223 @yearly Run once a year, "0 0 1 1 *".
224 @annually (same as @yearly)
225 @monthly Run once a month, "0 0 1 * *".
226 @weekly Run once a week, "0 0 * * 0".
227 @daily Run once a day, "0 0 * * *".
228 @midnight (same as @daily)
229 @hourly Run once an hour, "0 * * * *".
231 .Sh EXAMPLE CRON FILE
234 # use /bin/sh to run commands, overriding the default set by cron
236 # mail any output to `paul', no matter whose crontab this is
239 # run five minutes after midnight, every day
240 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
241 # run at 2:15pm on the first of every month -- output mailed to paul
242 15 14 1 * * $HOME/bin/monthly
243 # run at 10 pm on weekdays, annoy Joe
244 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
245 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
246 5 4 * * sun echo "run at 5 after 4 every sunday"
252 When specifying day of week, both day 0 and day 7 will be considered Sunday.
256 seem to disagree about this.
258 Lists and ranges are allowed to co-exist in the same field.
264 cron -- they want to see "1-3" or "7,8,9" ONLY.
266 Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
268 Names of months or days of the week can be specified by name.
270 Environment variables can be set in the crontab.
276 environment handed to child processes is basically the one from
279 Command output is mailed to the crontab owner
281 cannot do this), can be
282 mailed to a person other than the crontab owner (SysV cannot do this), or the
283 feature can be turned off and no mail will be sent at all (SysV cannot do this
288 commands that can appear in place of the first five fields
291 .An Paul Vixie Aq paul@vix.com
293 If you are in one of the 70-odd countries that observe Daylight
294 Savings Time, jobs scheduled during the rollback or advance will be
296 In general, it is not a good idea to schedule jobs during
299 For US timezones (except parts of IN, AZ, and HI) the time shift occurs at
301 For others, the output of the
305 option can be used to determine the moment of time shift.