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1 .\"/* Copyright 1988,1990,1993 by Paul Vixie
2 .\" * All rights reserved
3 .\" *
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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13 .\" * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
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17 .\"
18 .\" $Id: crontab.5,v 1.1 1994/01/05 20:40:13 jtc Exp $
19 .\"
20 .TH CRONTAB 5 "20 December 1993"
21 .UC 4
22 .SH NAME
23 crontab \- tables for driving cron
24 .SH DESCRIPTION
25 A
26 .I crontab
27 file contains instructions to the
28 .IR cron (8)
29 daemon of the general form: ``run this command at this time on this date''.
30 Each user has their own crontab, and commands in any given crontab will be
31 executed as the user who owns the crontab. Uucp and News will usually have
32 their own crontabs, eliminating the need for explicitly running
33 .IR su (1)
34 as part of a cron command.
35 .PP
36 Blank lines and leading spaces and tabs are ignored. Lines whose first
37 non-space character is a pound-sign (#) are comments, and are ignored.
38 Note that comments are not allowed on the same line as cron commands, since
39 they will be taken to be part of the command. Similarly, comments are not
40 allowed on the same line as environment variable settings.
41 .PP
42 An active line in a crontab will be either an environment setting or a cron
43 command. An environment setting is of the form,
44 .PP
45 name = value
46 .PP
47 where the spaces around the equal-sign (=) are optional, and any subsequent
48 non-leading spaces in
49 .I value
50 will be part of the value assigned to
51 .IR name .
52 The
53 .I value
54 string may be placed in quotes (single or double, but matching) to preserve
55 leading or trailing blanks.
56 .PP
57 Several environment variables are set up
58 automatically by the
59 .IR cron (8)
60 daemon from the /etc/passwd line of the crontab's owner: USER, HOME, and SHELL.
61 HOME and SHELL may be overridden by settings in the crontab; USER may not.
62 .PP
63 (Note: for UUCP, always set SHELL=/bin/sh, or
64 .IR cron (8)
65 will cheerfully try to execute your commands using /usr/lib/uucp/uucico.)
66 .PP
67 (Another note: the USER variable is sometimes called LOGNAME or worse on
68 System V... on these systems, LOGNAME will be set rather than USER.)
69 .PP
70 In addition to USER, HOME, and SHELL,
71 .IR cron (8)
72 will look at MAILTO if it has any reason to send mail as a result of running
73 commands in ``this'' crontab. If MAILTO is defined (and non-empty), mail is
74 sent to the user so named. If MAILTO is defined but empty (MAILTO=""), no
75 mail will be sent. Otherwise mail is sent to the owner of the crontab. This
76 option is useful if you decide on /bin/mail instead of /usr/lib/sendmail as
77 your mailer when you install cron -- /bin/mail doesn't do aliasing, and UUCP
78 usually doesn't read its mail.
79 .PP
80 The format of a cron command is very much the V7 standard, with a number of
81 upward-compatible extensions. Each line has five time and date fields,
82 followed by a command. Commands are executed by
83 .IR cron (8)
84 when the minute, hour, and month of year fields match the current time,
85 .I and
86 when at least one of the two day fields (day of month, or day of week)
87 match the current time (see ``Note'' below).
88 .IR cron (8)
89 examines cron entries once every minute.
90 The time and date fields are:
91 .IP
92 .ta 1.5i
93 field allowed values
94 .br
95 ----- --------------
96 .br
97 minute 0-59
98 .br
99 hour 0-23
100 .br
101 day of month 0-31
102 .br
103 month 0-12 (or names, see below)
104 .br
105 day of week 0-7 (0 or 7 is Sun, or use names)
106 .br
107 .PP
108 A field may be an asterisk (*), which always stands for ``first\-last''.
109 .PP
110 Ranges of numbers are allowed. Ranges are two numbers separated
111 with a hyphen. The specified range is inclusive. For example,
112 8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
113 and 11.
114 .PP
115 Lists are allowed. A list is a set of numbers (or ranges)
116 separated by commas. Examples: ``1,2,5,9'', ``0-4,8-12''.
117 .PP
118 Step values can be used in conjunction with ranges. Following
119 a range with ``/<number>'' specifies skips of the number's value
120 through the range. For example, ``0-23/2'' can be used in the hours
121 field to specify command execution every other hour (the alternative
122 in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). Steps are
123 also permitted after an asterisk, so if you want to say ``every two
124 hours'', just use ``*/2''.
125 .PP
126 Names can also be used for the ``month'' and ``day of week''
127 fields. Use the first three letters of the particular
128 day or month (case doesn't matter). Ranges or
129 lists of names are not allowed.
130 .PP
131 The ``sixth'' field (the rest of the line) specifies the command to be
132 run.
133 The entire command portion of the line, up to a newline or %
134 character, will be executed by the user's login shell or by the shell
135 specified in the SHELL variable of the cronfile.
136 Percent-signs (%) in the command, unless escaped with backslash
137 (\\), will be changed into newline characters, and all data
138 after the first % will be sent to the command as standard
139 input.
140 .PP
141 Note: The day of a command's execution can be specified by two
142 fields \(em day of month, and day of week. If both fields are
143 restricted (ie, aren't *), the command will be run when
144 .I either
145 field matches the current time. For example,
146 .br
147 ``30 4 1,15 * 5''
148 would cause a command to be run at 4:30 am on the 1st and 15th of each
149 month, plus every Friday.
150 .SH EXAMPLE CRON FILE
151 .nf
153 # use /bin/sh to run commands, no matter what /etc/passwd says
154 SHELL=/bin/sh
155 # mail any output to `paul', no matter whose crontab this is
156 MAILTO=paul
157 #
158 # run five minutes after midnight, every day
159 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
160 # run at 2:15pm on the first of every month -- output mailed to paul
161 15 14 1 * * $HOME/bin/monthly
162 # run at 10 pm on weekdays, annoy Joe
163 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
164 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
165 5 4 * * sun echo "run at 5 after 4 every sunday"
166 .fi
167 .SH SEE ALSO
168 cron(8), crontab(1)
169 .SH EXTENSIONS
170 When specifying day of week, both day 0 and day 7 will be considered Sunday.
171 BSD and ATT seem to disagree about this.
172 .PP
173 Lists and ranges are allowed to co-exist in the same field. "1-3,7-9" would
174 be rejected by ATT or BSD cron -- they want to see "1-3" or "7,8,9" ONLY.
175 .PP
176 Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
177 .PP
178 Names of months or days of the week can be specified by name.
179 .PP
180 Environment variables can be set in the crontab. In BSD or ATT, the
181 environment handed to child processes is basically the one from /etc/rc.
182 .PP
183 Command output is mailed to the crontab owner (BSD can't do this), can be
184 mailed to a person other than the crontab owner (SysV can't do this), or the
185 feature can be turned off and no mail will be sent at all (SysV can't do this
186 either).
187 .SH AUTHOR
188 .nf
189 Paul Vixie <paul@vix.com>