1.\"/* Copyright 1988,1990,1993,1994 by Paul Vixie 2.\" * All rights reserved 3.\" */ 4.\" 5.\"Copyright (c) 1997 by Internet Software Consortium 6.\" 7.\"Permission to use, copy, modify, and distribute this software for any 8.\"purpose with or without fee is hereby granted, provided that the above 9.\"copyright notice and this permission notice appear in all copies. 10.\" 11.\"THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS 12.\"ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES 13.\"OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE 14.\"CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 15.\"DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 16.\"PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 17.\"ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 18.\"SOFTWARE. 19.\" 20.\" $Id: crontab.5,v 1.2 1998/08/14 00:32:38 vixie Exp $ 21.\" 22.Dd March 29, 2020 23.Dt CRONTAB 5 24.Os 25.Sh NAME 26.Nm crontab 27.Nd tables for driving cron 28.Sh DESCRIPTION 29A 30.Nm 31file contains instructions to the 32.Xr cron 8 33daemon of the general form: ``run this command at this time on this date''. 34Each user has their own crontab, and commands in any given crontab will be 35executed as the user who owns the crontab. 36Uucp and News will usually have 37their own crontabs, eliminating the need for explicitly running 38.Xr su 1 39as part of a cron command. 40.Pp 41Blank lines and leading spaces and tabs are ignored. 42Lines whose first 43non-space character is a pound-sign (#) are comments, and are ignored. 44Note that comments are not allowed on the same line as cron commands, since 45they will be taken to be part of the command. 46Similarly, comments are not 47allowed on the same line as environment variable settings. 48.Pp 49An active line in a crontab will be either an environment setting or a cron 50command. 51An environment setting is of the form, 52.Bd -literal 53 name = value 54.Ed 55.Pp 56where the spaces around the equal-sign (=) are optional, and any subsequent 57non-leading spaces in 58.Em value 59will be part of the value assigned to 60.Em name . 61The 62.Em value 63string may be placed in quotes (single or double, but matching) to preserve 64leading or trailing blanks. 65The 66.Em name 67string may also be placed in quote (single or double, but matching) 68to preserve leading, trailing or inner blanks. 69.Pp 70Several environment variables are set up 71automatically by the 72.Xr cron 8 73daemon. 74.Ev SHELL 75is set to 76.Pa /bin/sh , 77and 78.Ev LOGNAME 79and 80.Ev HOME 81are set from the 82.Pa /etc/passwd 83line of the crontab's owner. 84In addition, the environment variables of the 85user's login class will be set from 86.Pa /etc/login.conf.db 87and 88.Pa ~/.login_conf . 89(A setting of 90.Ev HOME 91in the login class will override the value from 92.Pa /etc/passwd , 93but will not change the current directory when the command is 94invoked, which can only be overridden with an explicit setting of 95.Ev HOME 96within the crontab file itself.) 97If 98.Ev PATH 99is not set by any other means, it is defaulted to 100.Pa /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin . 101.Ev HOME , 102.Ev PATH 103and 104.Ev SHELL , 105and any variables set from the login class, 106may be overridden by settings in the crontab; 107.Ev LOGNAME 108may not. 109.Pp 110(Another note: the 111.Ev LOGNAME 112variable is sometimes called 113.Ev USER 114on 115.Bx 116systems... 117On these systems, 118.Ev USER 119will be set also). 120.Pp 121If 122.Xr cron 8 123has any reason to send mail as a result of running commands in 124``this'' crontab, it will respect the following settings which may be 125defined in the crontab (but which are not taken from the login class). 126If 127.Ev MAILTO 128is defined (and non-empty), mail is 129sent to the user so named. 130If 131.Ev MAILFROM 132is defined (and non-empty), its value will be used as the from address. 133.Ev MAILTO 134may also be used to direct mail to multiple recipients 135by separating recipient users with a comma. 136If 137.Ev MAILTO 138is defined but empty (MAILTO=""), no 139mail will be sent. 140Otherwise mail is sent to the owner of the crontab. 141This 142option is useful if you decide on 143.Pa /bin/mail 144instead of 145.Pa /usr/lib/sendmail 146as 147your mailer when you install cron -- 148.Pa /bin/mail 149does not do aliasing, and UUCP 150usually does not read its mail. 151.Pp 152The format of a cron command is very much the V7 standard, with a number of 153upward-compatible extensions. 154Each line has five time and date fields, 155followed by a user name 156(with optional ``:<group>'' and ``/<login-class>'' suffixes) 157if this is the system crontab file, 158followed by a command. 159Commands are executed by 160.Xr cron 8 161when the minute, hour, and month of year fields match the current time, 162.Em and 163when at least one of the two day fields (day of month, or day of week) 164matches the current time (see ``Note'' below). 165.Xr cron 8 166examines cron entries once every minute. 167The time and date fields are: 168.Bd -literal -offset indent 169field allowed values 170----- -------------- 171minute 0-59 172hour 0-23 173day of month 1-31 174month 1-12 (or names, see below) 175day of week 0-7 (0 or 7 is Sun, or use names) 176.Ed 177.Pp 178A field may be an asterisk (*), which always stands for ``first\-last''. 179.Pp 180Ranges of numbers are allowed. 181Ranges are two numbers separated 182with a hyphen. 183The specified range is inclusive. 184For example, 1858-11 for an ``hours'' entry specifies execution at hours 8, 9, 10 186and 11. 187.Pp 188Lists are allowed. 189A list is a set of numbers (or ranges) 190separated by commas. 191Examples: ``1,2,5,9'', ``0-4,8-12''. 192.Pp 193Step values can be used in conjunction with ranges. 194Following 195a range with ``/<number>'' specifies skips of the number's value 196through the range. 197For example, ``0-23/2'' can be used in the hours 198field to specify command execution every other hour (the alternative 199in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). 200Steps are 201also permitted after an asterisk, so if you want to say ``every two 202hours'', just use ``*/2''. 203.Pp 204Names can also be used for the ``month'' and ``day of week'' 205fields. 206Use the first three letters of the particular 207day or month (case does not matter). 208Ranges and lists are also allowed. 209.Pp 210The ``sixth'' field (the rest of the line) specifies the command to be 211run. 212One or more command options may precede the command to modify processing 213behavior. 214The entire command portion of the line, up to a newline or % 215character, will be executed by 216.Pa /bin/sh 217or by the shell 218specified in the 219.Ev SHELL 220variable of the cronfile. 221Percent-signs (%) in the command, unless escaped with backslash 222(\\), will be changed into newline characters, and all data 223after the first % will be sent to the command as standard 224input. 225.Pp 226The following command options can be supplied: 227.Bl -tag -width Ds 228.It Fl n 229No mail is sent after a successful run. 230The execution output will only be mailed if the command exits with a non-zero 231exit code. 232The 233.Fl n 234option is an attempt to cure potentially copious volumes of mail coming from 235.Xr cron 8 . 236.It Fl q 237Execution will not be logged. 238.El 239.sp 240Duplicate options are not allowed. 241.Pp 242Note: The day of a command's execution can be specified by two 243fields \(em day of month, and day of week. 244If both fields are 245restricted (ie, are not *), the command will be run when 246.Em either 247field matches the current time. 248For example, 249``30 4 1,15 * 5'' 250would cause a command to be run at 4:30 am on the 1st and 15th of each 251month, plus every Friday. 252.Pp 253Instead of the first five fields, 254a line may start with 255.Sq @ 256symbol followed either by one of eight special strings or by a numeric value. 257The recognized special strings are: 258.Bd -literal -offset indent 259string meaning 260------ ------- 261@reboot Run once, at startup of cron. 262@yearly Run once a year, "0 0 1 1 *". 263@annually (same as @yearly) 264@monthly Run once a month, "0 0 1 * *". 265@weekly Run once a week, "0 0 * * 0". 266@daily Run once a day, "0 0 * * *". 267@midnight (same as @daily) 268@hourly Run once an hour, "0 * * * *". 269@every_minute Run once a minute, "*/1 * * * *". 270@every_second Run once a second. 271.Ed 272.Pp 273The 274.Sq @ 275symbol followed by a numeric value has a special notion of running 276a job that many seconds after completion of the previous invocation of 277the job. 278Unlike regular syntax, it guarantees not to overlap two or more 279invocations of the same job during normal cron execution. 280Note, however, that overlap may occur if the job is running when the file 281containing the job is modified and subsequently reloaded. 282The first run is scheduled for the specified number of seconds after cron 283is started or the crontab entry is reloaded. 284.Sh EXAMPLE CRON FILE 285.Bd -literal 286 287# use /bin/sh to run commands, overriding the default set by cron 288SHELL=/bin/sh 289# mail any output to `paul', no matter whose crontab this is 290MAILTO=paul 291# 292# run five minutes after midnight, every day 2935 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 294# run at 2:15pm on the first of every month -- output mailed to paul 29515 14 1 * * $HOME/bin/monthly 296# run at 10 pm on weekdays, annoy Joe 2970 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 29823 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 2995 4 * * sun echo "run at 5 after 4 every sunday" 300# run at 5 minutes intervals, no matter how long it takes 301@300 svnlite up /usr/src 302# run every minute, suppress logging 303* * * * * -q date 304# run every minute, only send mail if ping fails 305* * * * * -n ping -c 1 freebsd.org 306.Ed 307.Sh SEE ALSO 308.Xr crontab 1 , 309.Xr cron 8 310.Sh EXTENSIONS 311When specifying day of week, both day 0 and day 7 will be considered Sunday. 312.Bx 313and 314.Tn ATT 315seem to disagree about this. 316.Pp 317Lists and ranges are allowed to co-exist in the same field. 318"1-3,7-9" would 319be rejected by 320.Tn ATT 321or 322.Bx 323cron -- they want to see "1-3" or "7,8,9" ONLY. 324.Pp 325Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". 326.Pp 327Names of months or days of the week can be specified by name. 328.Pp 329Environment variables can be set in the crontab. 330In 331.Bx 332or 333.Tn ATT , 334the 335environment handed to child processes is basically the one from 336.Pa /etc/rc . 337.Pp 338Command output is mailed to the crontab owner 339.No ( Bx 340cannot do this), can be 341mailed to a person other than the crontab owner (SysV cannot do this), or the 342feature can be turned off and no mail will be sent at all (SysV cannot do this 343either). 344.Pp 345All of the 346.Sq @ 347directives that can appear in place of the first five fields 348are extensions. 349.Pp 350Command processing can be modified using command options. 351The 352.Sq -q 353option suppresses logging. 354The 355.Sq -n 356option does not mail on successful run. 357.Sh AUTHORS 358.An Paul Vixie Aq Mt paul@vix.com 359.Sh BUGS 360If you are in one of the 70-odd countries that observe Daylight 361Savings Time, jobs scheduled during the rollback or advance may be 362affected if 363.Xr cron 8 364is not started with the 365.Fl s 366flag. 367In general, it is not a good idea to schedule jobs during 368this period if 369.Xr cron 8 370is not started with the 371.Fl s 372flag, which is enabled by default. 373See 374.Xr cron 8 375for more details. 376.Pp 377For US timezones (except parts of AZ and HI) the time shift occurs at 3782AM local time. 379For others, the output of the 380.Xr zdump 8 381program's verbose 382.Fl ( v ) 383option can be used to determine the moment of time shift. 384