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 March 29, 2020 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 , 75and 76.Ev LOGNAME 77and 78.Ev HOME 79are set from the 80.Pa /etc/passwd 81line of the crontab's owner. 82In addition, the environment variables of the 83user's login class will be set from 84.Pa /etc/login.conf.db 85and 86.Pa ~/.login_conf . 87(A setting of 88.Ev HOME 89in the login class will override the value from 90.Pa /etc/passwd , 91but will not change the current directory when the command is 92invoked, which can only be overridden with an explicit setting of 93.Ev HOME 94within the crontab file itself.) 95If 96.Ev PATH 97is not set by any other means, it is defaulted to 98.Pa /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin . 99.Ev HOME , 100.Ev PATH 101and 102.Ev SHELL , 103and any variables set from the login class, 104may be overridden by settings in the crontab; 105.Ev LOGNAME 106may not. 107.Pp 108(Another note: the 109.Ev LOGNAME 110variable is sometimes called 111.Ev USER 112on 113.Bx 114systems... 115On these systems, 116.Ev USER 117will be set also). 118.Pp 119If 120.Xr cron 8 121has any reason to send mail as a result of running commands in 122``this'' crontab, it will respect the following settings which may be 123defined in the crontab (but which are not taken from the login class). 124If 125.Ev MAILTO 126is defined (and non-empty), mail is 127sent to the user so named. 128If 129.Ev MAILFROM 130is defined (and non-empty), its value will be used as the from address. 131.Ev MAILTO 132may also be used to direct mail to multiple recipients 133by separating recipient users with a comma. 134If 135.Ev MAILTO 136is defined but empty (MAILTO=""), no 137mail will be sent. 138Otherwise mail is sent to the owner of the crontab. 139This 140option is useful if you decide on 141.Pa /bin/mail 142instead of 143.Pa /usr/lib/sendmail 144as 145your mailer when you install cron -- 146.Pa /bin/mail 147does not do aliasing, and UUCP 148usually does not read its mail. 149.Pp 150The format of a cron command is very much the V7 standard, with a number of 151upward-compatible extensions. 152Each line has five time and date fields, 153followed by a user name 154(with optional ``:<group>'' and ``/<login-class>'' suffixes) 155if this is the system crontab file, 156followed by a command. 157Commands are executed by 158.Xr cron 8 159when the minute, hour, and month of year fields match the current time, 160.Em and 161when at least one of the two day fields (day of month, or day of week) 162matches the current time (see ``Note'' below). 163.Xr cron 8 164examines cron entries once every minute. 165The time and date fields are: 166.Bd -literal -offset indent 167field allowed values 168----- -------------- 169minute 0-59 170hour 0-23 171day of month 1-31 172month 1-12 (or names, see below) 173day of week 0-7 (0 or 7 is Sun, or use names) 174.Ed 175.Pp 176A field may be an asterisk (*), which always stands for ``first\-last''. 177.Pp 178Ranges of numbers are allowed. 179Ranges are two numbers separated 180with a hyphen. 181The specified range is inclusive. 182For example, 1838-11 for an ``hours'' entry specifies execution at hours 8, 9, 10 184and 11. 185.Pp 186Lists are allowed. 187A list is a set of numbers (or ranges) 188separated by commas. 189Examples: ``1,2,5,9'', ``0-4,8-12''. 190.Pp 191Step values can be used in conjunction with ranges. 192Following 193a range with ``/<number>'' specifies skips of the number's value 194through the range. 195For example, ``0-23/2'' can be used in the hours 196field to specify command execution every other hour (the alternative 197in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). 198Steps are 199also permitted after an asterisk, so if you want to say ``every two 200hours'', just use ``*/2''. 201.Pp 202Names can also be used for the ``month'' and ``day of week'' 203fields. 204Use the first three letters of the particular 205day or month (case does not matter). 206Ranges or 207lists of names are not allowed. 208.Pp 209The ``sixth'' field (the rest of the line) specifies the command to be 210run. 211One or more command options may precede the command to modify processing 212behavior. 213The entire command portion of the line, up to a newline or % 214character, will be executed by 215.Pa /bin/sh 216or by the shell 217specified in the 218.Ev SHELL 219variable of the cronfile. 220Percent-signs (%) in the command, unless escaped with backslash 221(\\), will be changed into newline characters, and all data 222after the first % will be sent to the command as standard 223input. 224.Pp 225The following command options can be supplied: 226.Bl -tag -width Ds 227.It Fl n 228No mail is sent after a successful run. 229The execution output will only be mailed if the command exits with a non-zero 230exit code. 231The 232.Fl n 233option is an attempt to cure potentially copious volumes of mail coming from 234.Xr cron 8 . 235.It Fl q 236Execution will not be logged. 237.El 238.sp 239Duplicate options are not allowed. 240.Pp 241Note: The day of a command's execution can be specified by two 242fields \(em day of month, and day of week. 243If both fields are 244restricted (ie, are not *), the command will be run when 245.Em either 246field matches the current time. 247For example, 248``30 4 1,15 * 5'' 249would cause a command to be run at 4:30 am on the 1st and 15th of each 250month, plus every Friday. 251.Pp 252Instead of the first five fields, 253a line may start with 254.Sq @ 255symbol followed either by one of eight special strings or by a numeric value. 256The recognized special strings are: 257.Bd -literal -offset indent 258string meaning 259------ ------- 260@reboot Run once, at startup of cron. 261@yearly Run once a year, "0 0 1 1 *". 262@annually (same as @yearly) 263@monthly Run once a month, "0 0 1 * *". 264@weekly Run once a week, "0 0 * * 0". 265@daily Run once a day, "0 0 * * *". 266@midnight (same as @daily) 267@hourly Run once an hour, "0 * * * *". 268@every_minute Run once a minute, "*/1 * * * *". 269@every_second Run once a second. 270.Ed 271.Pp 272The 273.Sq @ 274symbol followed by a numeric value has a special notion of running 275a job that many seconds after completion of the previous invocation of 276the job. 277Unlike regular syntax, it guarantees not to overlap two or more 278invocations of the same job during normal cron execution. 279Note, however, that overlap may occur if the job is running when the file 280containing the job is modified and subsequently reloaded. 281The first run is scheduled for the specified number of seconds after cron 282is started or the crontab entry is reloaded. 283.Sh EXAMPLE CRON FILE 284.Bd -literal 285 286# use /bin/sh to run commands, overriding the default set by cron 287SHELL=/bin/sh 288# mail any output to `paul', no matter whose crontab this is 289MAILTO=paul 290# 291# run five minutes after midnight, every day 2925 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 293# run at 2:15pm on the first of every month -- output mailed to paul 29415 14 1 * * $HOME/bin/monthly 295# run at 10 pm on weekdays, annoy Joe 2960 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 29723 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 2985 4 * * sun echo "run at 5 after 4 every sunday" 299# run at 5 minutes intervals, no matter how long it takes 300@300 svnlite up /usr/src 301# run every minute, suppress logging 302* * * * * -q date 303# run every minute, only send mail if ping fails 304* * * * * -n ping -c 1 freebsd.org 305.Ed 306.Sh SEE ALSO 307.Xr crontab 1 , 308.Xr cron 8 309.Sh EXTENSIONS 310When specifying day of week, both day 0 and day 7 will be considered Sunday. 311.Bx 312and 313.Tn ATT 314seem to disagree about this. 315.Pp 316Lists and ranges are allowed to co-exist in the same field. 317"1-3,7-9" would 318be rejected by 319.Tn ATT 320or 321.Bx 322cron -- they want to see "1-3" or "7,8,9" ONLY. 323.Pp 324Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". 325.Pp 326Names of months or days of the week can be specified by name. 327.Pp 328Environment variables can be set in the crontab. 329In 330.Bx 331or 332.Tn ATT , 333the 334environment handed to child processes is basically the one from 335.Pa /etc/rc . 336.Pp 337Command output is mailed to the crontab owner 338.No ( Bx 339cannot do this), can be 340mailed to a person other than the crontab owner (SysV cannot do this), or the 341feature can be turned off and no mail will be sent at all (SysV cannot do this 342either). 343.Pp 344All of the 345.Sq @ 346directives that can appear in place of the first five fields 347are extensions. 348.Pp 349Command processing can be modified using command options. 350The 351.Sq -q 352option suppresses logging. 353The 354.Sq -n 355option does not mail on successful run. 356.Sh AUTHORS 357.An Paul Vixie Aq Mt paul@vix.com 358.Sh BUGS 359If you are in one of the 70-odd countries that observe Daylight 360Savings Time, jobs scheduled during the rollback or advance may be 361affected if 362.Xr cron 8 363is not started with the 364.Fl s 365flag. 366In general, it is not a good idea to schedule jobs during 367this period if 368.Xr cron 8 369is not started with the 370.Fl s 371flag, which is enabled by default. 372See 373.Xr cron 8 374for more details. 375.Pp 376For US timezones (except parts of AZ and HI) the time shift occurs at 3772AM local time. 378For others, the output of the 379.Xr zdump 8 380program's verbose 381.Fl ( v ) 382option can be used to determine the moment of time shift. 383