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 15, 2019 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 /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/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. 119If 120.Ev MAILFROM 121is defined (and non-empty), its value will be used as the from address. 122.Ev MAILTO 123may also be used to direct mail to multiple recipients 124by separating recipient users with a comma. 125If 126.Ev MAILTO 127is defined but empty (MAILTO=""), no 128mail will be sent. 129Otherwise mail is sent to the owner of the crontab. 130This 131option is useful if you decide on 132.Pa /bin/mail 133instead of 134.Pa /usr/lib/sendmail 135as 136your mailer when you install cron -- 137.Pa /bin/mail 138does not do aliasing, and UUCP 139usually does not read its mail. 140.Pp 141The format of a cron command is very much the V7 standard, with a number of 142upward-compatible extensions. 143Each line has five time and date fields, 144followed by a user name 145(with optional ``:<group>'' and ``/<login-class>'' suffixes) 146if this is the system crontab file, 147followed by a command. 148Commands are executed by 149.Xr cron 8 150when the minute, hour, and month of year fields match the current time, 151.Em and 152when at least one of the two day fields (day of month, or day of week) 153matches the current time (see ``Note'' below). 154.Xr cron 8 155examines cron entries once every minute. 156The time and date fields are: 157.Bd -literal -offset indent 158field allowed values 159----- -------------- 160minute 0-59 161hour 0-23 162day of month 1-31 163month 1-12 (or names, see below) 164day of week 0-7 (0 or 7 is Sun, or use names) 165.Ed 166.Pp 167A field may be an asterisk (*), which always stands for ``first\-last''. 168.Pp 169Ranges of numbers are allowed. 170Ranges are two numbers separated 171with a hyphen. 172The specified range is inclusive. 173For example, 1748-11 for an ``hours'' entry specifies execution at hours 8, 9, 10 175and 11. 176.Pp 177Lists are allowed. 178A list is a set of numbers (or ranges) 179separated by commas. 180Examples: ``1,2,5,9'', ``0-4,8-12''. 181.Pp 182Step values can be used in conjunction with ranges. 183Following 184a range with ``/<number>'' specifies skips of the number's value 185through the range. 186For example, ``0-23/2'' can be used in the hours 187field to specify command execution every other hour (the alternative 188in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). 189Steps are 190also permitted after an asterisk, so if you want to say ``every two 191hours'', just use ``*/2''. 192.Pp 193Names can also be used for the ``month'' and ``day of week'' 194fields. 195Use the first three letters of the particular 196day or month (case does not matter). 197Ranges or 198lists of names are not allowed. 199.Pp 200The ``sixth'' field (the rest of the line) specifies the command to be 201run. 202The entire command portion of the line, up to a newline or % 203character, will be executed by 204.Pa /bin/sh 205or by the shell 206specified in the 207.Ev SHELL 208variable of the cronfile. 209Percent-signs (%) in the command, unless escaped with backslash 210(\\), will be changed into newline characters, and all data 211after the first % will be sent to the command as standard 212input. 213.Pp 214Note: The day of a command's execution can be specified by two 215fields \(em day of month, and day of week. 216If both fields are 217restricted (ie, are not *), the command will be run when 218.Em either 219field matches the current time. 220For example, 221``30 4 1,15 * 5'' 222would cause a command to be run at 4:30 am on the 1st and 15th of each 223month, plus every Friday. 224.Pp 225Instead of the first five fields, 226a line may start with 227.Sq @ 228symbol followed either by one of eight special strings or by a numeric value. 229The recognized special strings are: 230.Bd -literal -offset indent 231string meaning 232------ ------- 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. 243.Ed 244.Pp 245The 246.Sq @ 247symbol followed by a numeric value has a special notion of running 248a job that much seconds after completion of previous invocation of 249the job. 250Unlike regular syntax, it guarantees not to overlap two or more 251invocations of the same job. 252The first run is scheduled specified amount of seconds after cron 253has started. 254.Sh EXAMPLE CRON FILE 255.Bd -literal 256 257# use /bin/sh to run commands, overriding the default set by cron 258SHELL=/bin/sh 259# mail any output to `paul', no matter whose crontab this is 260MAILTO=paul 261# 262# run five minutes after midnight, every day 2635 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 264# run at 2:15pm on the first of every month -- output mailed to paul 26515 14 1 * * $HOME/bin/monthly 266# run at 10 pm on weekdays, annoy Joe 2670 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 26823 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 2695 4 * * sun echo "run at 5 after 4 every sunday" 270# run at 5 minutes intervals, no matter how long it takes 271@300 svnlite up /usr/src 272.Ed 273.Sh SEE ALSO 274.Xr crontab 1 , 275.Xr cron 8 276.Sh EXTENSIONS 277When specifying day of week, both day 0 and day 7 will be considered Sunday. 278.Bx 279and 280.Tn ATT 281seem to disagree about this. 282.Pp 283Lists and ranges are allowed to co-exist in the same field. 284"1-3,7-9" would 285be rejected by 286.Tn ATT 287or 288.Bx 289cron -- they want to see "1-3" or "7,8,9" ONLY. 290.Pp 291Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". 292.Pp 293Names of months or days of the week can be specified by name. 294.Pp 295Environment variables can be set in the crontab. 296In 297.Bx 298or 299.Tn ATT , 300the 301environment handed to child processes is basically the one from 302.Pa /etc/rc . 303.Pp 304Command output is mailed to the crontab owner 305.No ( Bx 306cannot do this), can be 307mailed to a person other than the crontab owner (SysV cannot do this), or the 308feature can be turned off and no mail will be sent at all (SysV cannot do this 309either). 310.Pp 311All of the 312.Sq @ 313directives that can appear in place of the first five fields 314are extensions. 315.Sh AUTHORS 316.An Paul Vixie Aq Mt paul@vix.com 317.Sh BUGS 318If you are in one of the 70-odd countries that observe Daylight 319Savings Time, jobs scheduled during the rollback or advance may be 320affected if 321.Xr cron 8 322is not started with the 323.Fl s 324flag. 325In general, it is not a good idea to schedule jobs during 326this period if 327.Xr cron 8 328is not started with the 329.Fl s 330flag, which is enabled by default. 331See 332.Xr cron 8 333for more details. 334.Pp 335For US timezones (except parts of AZ and HI) the time shift occurs at 3362AM local time. 337For others, the output of the 338.Xr zdump 8 339program's verbose 340.Fl ( v ) 341option can be used to determine the moment of time shift. 342