1.\"/* Copyright 1988,1990,1993,1994 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 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 11.\" * user. 12.\" * 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 16.\" */ 17.\" 18.\" $FreeBSD$ 19.\" 20.Dd April 28, 2012 21.Dt CRONTAB 5 22.Os 23.Sh NAME 24.Nm crontab 25.Nd tables for driving cron 26.Sh DESCRIPTION 27A 28.Nm 29file contains instructions to the 30.Xr cron 8 31daemon of the general form: ``run this command at this time on this date''. 32Each user has their own crontab, and commands in any given crontab will be 33executed as the user who owns the crontab. 34Uucp and News will usually have 35their own crontabs, eliminating the need for explicitly running 36.Xr su 1 37as part of a cron command. 38.Pp 39Blank lines and leading spaces and tabs are ignored. 40Lines whose first 41non-space character is a pound-sign (#) are comments, and are ignored. 42Note that comments are not allowed on the same line as cron commands, since 43they will be taken to be part of the command. 44Similarly, comments are not 45allowed on the same line as environment variable settings. 46.Pp 47An active line in a crontab will be either an environment setting or a cron 48command. 49An environment setting is of the form, 50.Bd -literal 51 name = value 52.Ed 53.Pp 54where the spaces around the equal-sign (=) are optional, and any subsequent 55non-leading spaces in 56.Em value 57will be part of the value assigned to 58.Em name . 59The 60.Em value 61string may be placed in quotes (single or double, but matching) to preserve 62leading or trailing blanks. 63The 64.Em name 65string may also be placed in quote (single or double, but matching) 66to preserve leading, trailing or inner blanks. 67.Pp 68Several environment variables are set up 69automatically by the 70.Xr cron 8 71daemon. 72.Ev SHELL 73is set to 74.Pa /bin/sh , 75.Ev PATH 76is set to 77.Pa /usr/bin:/bin , 78and 79.Ev LOGNAME 80and 81.Ev HOME 82are set from the 83.Pa /etc/passwd 84line of the crontab's owner. 85.Ev HOME , 86.Ev PATH 87and 88.Ev SHELL 89may be overridden by settings in the crontab; 90.Ev LOGNAME 91may not. 92.Pp 93(Another note: the 94.Ev LOGNAME 95variable is sometimes called 96.Ev USER 97on 98.Bx 99systems... 100On these systems, 101.Ev USER 102will be set also). 103.Pp 104In addition to 105.Ev LOGNAME , 106.Ev HOME , 107.Ev PATH , 108and 109.Ev SHELL , 110.Xr cron 8 111will look at 112.Ev MAILTO 113if it has any reason to send mail as a result of running 114commands in ``this'' crontab. 115If 116.Ev MAILTO 117is defined (and non-empty), mail is 118sent to the user so named. 119.Ev MAILTO 120may also be used to direct mail to multiple recipients 121by separating recipient users with a comma. 122If 123.Ev MAILTO 124is defined but empty (MAILTO=""), no 125mail will be sent. 126Otherwise mail is sent to the owner of the crontab. 127This 128option is useful if you decide on 129.Pa /bin/mail 130instead of 131.Pa /usr/lib/sendmail 132as 133your mailer when you install cron -- 134.Pa /bin/mail 135does not do aliasing, and UUCP 136usually does not read its mail. 137.Pp 138The format of a cron command is very much the V7 standard, with a number of 139upward-compatible extensions. 140Each line has five time and date fields, 141followed by a user name 142(with optional ``:<group>'' and ``/<login-class>'' suffixes) 143if this is the system crontab file, 144followed by a command. 145Commands are executed by 146.Xr cron 8 147when the minute, hour, and month of year fields match the current time, 148.Em and 149when at least one of the two day fields (day of month, or day of week) 150matches the current time (see ``Note'' below). 151.Xr cron 8 152examines cron entries once every minute. 153The time and date fields are: 154.Bd -literal -offset indent 155field allowed values 156----- -------------- 157minute 0-59 158hour 0-23 159day of month 1-31 160month 1-12 (or names, see below) 161day of week 0-7 (0 or 7 is Sun, or use names) 162.Ed 163.Pp 164A field may be an asterisk (*), which always stands for ``first\-last''. 165.Pp 166Ranges of numbers are allowed. 167Ranges are two numbers separated 168with a hyphen. 169The specified range is inclusive. 170For example, 1718-11 for an ``hours'' entry specifies execution at hours 8, 9, 10 172and 11. 173.Pp 174Lists are allowed. 175A list is a set of numbers (or ranges) 176separated by commas. 177Examples: ``1,2,5,9'', ``0-4,8-12''. 178.Pp 179Step values can be used in conjunction with ranges. 180Following 181a range with ``/<number>'' specifies skips of the number's value 182through the range. 183For example, ``0-23/2'' can be used in the hours 184field to specify command execution every other hour (the alternative 185in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). 186Steps are 187also permitted after an asterisk, so if you want to say ``every two 188hours'', just use ``*/2''. 189.Pp 190Names can also be used for the ``month'' and ``day of week'' 191fields. 192Use the first three letters of the particular 193day or month (case does not matter). 194Ranges or 195lists of names are not allowed. 196.Pp 197The ``sixth'' field (the rest of the line) specifies the command to be 198run. 199The entire command portion of the line, up to a newline or % 200character, will be executed by 201.Pa /bin/sh 202or by the shell 203specified in the 204.Ev SHELL 205variable of the cronfile. 206Percent-signs (%) in the command, unless escaped with backslash 207(\\), will be changed into newline characters, and all data 208after the first % will be sent to the command as standard 209input. 210.Pp 211Note: The day of a command's execution can be specified by two 212fields \(em day of month, and day of week. 213If both fields are 214restricted (ie, are not *), the command will be run when 215.Em either 216field matches the current time. 217For example, 218``30 4 1,15 * 5'' 219would cause a command to be run at 4:30 am on the 1st and 15th of each 220month, plus every Friday. 221.Pp 222Instead of the first five fields, 223one of eight special strings may appear: 224.Bd -literal -offset indent 225string meaning 226------ ------- 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. 237.Ed 238.Sh EXAMPLE CRON FILE 239.Bd -literal 240 241# use /bin/sh to run commands, overriding the default set by cron 242SHELL=/bin/sh 243# mail any output to `paul', no matter whose crontab this is 244MAILTO=paul 245# 246# run five minutes after midnight, every day 2475 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 24915 14 1 * * $HOME/bin/monthly 250# run at 10 pm on weekdays, annoy Joe 2510 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 25223 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 2535 4 * * sun echo "run at 5 after 4 every sunday" 254.Ed 255.Sh SEE ALSO 256.Xr crontab 1 , 257.Xr cron 8 258.Sh EXTENSIONS 259When specifying day of week, both day 0 and day 7 will be considered Sunday. 260.Bx 261and 262.Tn ATT 263seem to disagree about this. 264.Pp 265Lists and ranges are allowed to co-exist in the same field. 266"1-3,7-9" would 267be rejected by 268.Tn ATT 269or 270.Bx 271cron -- they want to see "1-3" or "7,8,9" ONLY. 272.Pp 273Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". 274.Pp 275Names of months or days of the week can be specified by name. 276.Pp 277Environment variables can be set in the crontab. 278In 279.Bx 280or 281.Tn ATT , 282the 283environment handed to child processes is basically the one from 284.Pa /etc/rc . 285.Pp 286Command output is mailed to the crontab owner 287.No ( Bx 288cannot do this), can be 289mailed to a person other than the crontab owner (SysV cannot do this), or the 290feature can be turned off and no mail will be sent at all (SysV cannot do this 291either). 292.Pp 293All of the 294.Sq @ 295commands that can appear in place of the first five fields 296are extensions. 297.Sh AUTHORS 298.An Paul Vixie Aq paul@vix.com 299.Sh BUGS 300If you are in one of the 70-odd countries that observe Daylight 301Savings Time, jobs scheduled during the rollback or advance may be 302affected if 303.Xr cron 8 304is not started with the 305.Fl s 306flag. 307In general, it is not a good idea to schedule jobs during 308this period if 309.Xr cron 8 310is not started with the 311.Fl s 312flag, which is enabled by default. 313See 314.Xr cron 8 315for more details. 316.Pp 317For US timezones (except parts of AZ and HI) the time shift occurs at 3182AM local time. 319For others, the output of the 320.Xr zdump 8 321program's verbose 322.Fl ( v ) 323option can be used to determine the moment of time shift. 324