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 and lists are also allowed. 207.Pp 208The ``sixth'' field (the rest of the line) specifies the command to be 209run. 210One or more command options may precede the command to modify processing 211behavior. 212The entire command portion of the line, up to a newline or % 213character, will be executed by 214.Pa /bin/sh 215or by the shell 216specified in the 217.Ev SHELL 218variable of the cronfile. 219Percent-signs (%) in the command, unless escaped with backslash 220(\\), will be changed into newline characters, and all data 221after the first % will be sent to the command as standard 222input. 223.Pp 224The following command options can be supplied: 225.Bl -tag -width Ds 226.It Fl n 227No mail is sent after a successful run. 228The execution output will only be mailed if the command exits with a non-zero 229exit code. 230The 231.Fl n 232option is an attempt to cure potentially copious volumes of mail coming from 233.Xr cron 8 . 234.It Fl q 235Execution will not be logged. 236.El 237.sp 238Duplicate options are not allowed. 239.Pp 240Note: The day of a command's execution can be specified by two 241fields \(em day of month, and day of week. 242If both fields are 243restricted (ie, are not *), the command will be run when 244.Em either 245field matches the current time. 246For example, 247``30 4 1,15 * 5'' 248would cause a command to be run at 4:30 am on the 1st and 15th of each 249month, plus every Friday. 250.Pp 251Instead of the first five fields, 252a line may start with 253.Sq @ 254symbol followed either by one of eight special strings or by a numeric value. 255The recognized special strings are: 256.Bd -literal -offset indent 257string meaning 258------ ------- 259@reboot Run once, at startup of cron. 260@yearly Run once a year, "0 0 1 1 *". 261@annually (same as @yearly) 262@monthly Run once a month, "0 0 1 * *". 263@weekly Run once a week, "0 0 * * 0". 264@daily Run once a day, "0 0 * * *". 265@midnight (same as @daily) 266@hourly Run once an hour, "0 * * * *". 267@every_minute Run once a minute, "*/1 * * * *". 268@every_second Run once a second. 269.Ed 270.Pp 271The 272.Sq @ 273symbol followed by a numeric value has a special notion of running 274a job that many seconds after completion of the previous invocation of 275the job. 276Unlike regular syntax, it guarantees not to overlap two or more 277invocations of the same job during normal cron execution. 278Note, however, that overlap may occur if the job is running when the file 279containing the job is modified and subsequently reloaded. 280The first run is scheduled for the specified number of seconds after cron 281is started or the crontab entry is reloaded. 282.Sh EXAMPLE CRON FILE 283.Bd -literal 284 285# use /bin/sh to run commands, overriding the default set by cron 286SHELL=/bin/sh 287# mail any output to `paul', no matter whose crontab this is 288MAILTO=paul 289# 290# run five minutes after midnight, every day 2915 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 292# run at 2:15pm on the first of every month -- output mailed to paul 29315 14 1 * * $HOME/bin/monthly 294# run at 10 pm on weekdays, annoy Joe 2950 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 29623 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 2975 4 * * sun echo "run at 5 after 4 every sunday" 298# run at 5 minutes intervals, no matter how long it takes 299@300 svnlite up /usr/src 300# run every minute, suppress logging 301* * * * * -q date 302# run every minute, only send mail if ping fails 303* * * * * -n ping -c 1 freebsd.org 304.Ed 305.Sh SEE ALSO 306.Xr crontab 1 , 307.Xr cron 8 308.Sh EXTENSIONS 309When specifying day of week, both day 0 and day 7 will be considered Sunday. 310.Bx 311and 312.Tn ATT 313seem to disagree about this. 314.Pp 315Lists and ranges are allowed to co-exist in the same field. 316"1-3,7-9" would 317be rejected by 318.Tn ATT 319or 320.Bx 321cron -- they want to see "1-3" or "7,8,9" ONLY. 322.Pp 323Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". 324.Pp 325Names of months or days of the week can be specified by name. 326.Pp 327Environment variables can be set in the crontab. 328In 329.Bx 330or 331.Tn ATT , 332the 333environment handed to child processes is basically the one from 334.Pa /etc/rc . 335.Pp 336Command output is mailed to the crontab owner 337.No ( Bx 338cannot do this), can be 339mailed to a person other than the crontab owner (SysV cannot do this), or the 340feature can be turned off and no mail will be sent at all (SysV cannot do this 341either). 342.Pp 343All of the 344.Sq @ 345directives that can appear in place of the first five fields 346are extensions. 347.Pp 348Command processing can be modified using command options. 349The 350.Sq -q 351option suppresses logging. 352The 353.Sq -n 354option does not mail on successful run. 355.Sh AUTHORS 356.An Paul Vixie Aq Mt paul@vix.com 357.Sh BUGS 358If you are in one of the 70-odd countries that observe Daylight 359Savings Time, jobs scheduled during the rollback or advance may be 360affected if 361.Xr cron 8 362is not started with the 363.Fl s 364flag. 365In general, it is not a good idea to schedule jobs during 366this period if 367.Xr cron 8 368is not started with the 369.Fl s 370flag, which is enabled by default. 371See 372.Xr cron 8 373for more details. 374.Pp 375For US timezones (except parts of AZ and HI) the time shift occurs at 3762AM local time. 377For others, the output of the 378.Xr zdump 8 379program's verbose 380.Fl ( v ) 381option can be used to determine the moment of time shift. 382