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 September 24, 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. 202One or more command options may precede the command to modify processing 203behavior. 204The entire command portion of the line, up to a newline or % 205character, will be executed by 206.Pa /bin/sh 207or by the shell 208specified in the 209.Ev SHELL 210variable of the cronfile. 211Percent-signs (%) in the command, unless escaped with backslash 212(\\), will be changed into newline characters, and all data 213after the first % will be sent to the command as standard 214input. 215.Pp 216The following command options can be supplied: 217.Bl -tag -width Ds 218.It Fl n 219No mail is sent after a successful run. 220The execution output will only be mailed if the command exits with a non-zero 221exit code. 222The 223.Fl n 224option is an attempt to cure potentially copious volumes of mail coming from 225.Xr cron 8 . 226.It Fl q 227Execution will not be logged. 228.El 229.sp 230Duplicate options are not allowed. 231.Pp 232Note: The day of a command's execution can be specified by two 233fields \(em day of month, and day of week. 234If both fields are 235restricted (ie, are not *), the command will be run when 236.Em either 237field matches the current time. 238For example, 239``30 4 1,15 * 5'' 240would cause a command to be run at 4:30 am on the 1st and 15th of each 241month, plus every Friday. 242.Pp 243Instead of the first five fields, 244a line may start with 245.Sq @ 246symbol followed either by one of eight special strings or by a numeric value. 247The recognized special strings are: 248.Bd -literal -offset indent 249string meaning 250------ ------- 251@reboot Run once, at startup of cron. 252@yearly Run once a year, "0 0 1 1 *". 253@annually (same as @yearly) 254@monthly Run once a month, "0 0 1 * *". 255@weekly Run once a week, "0 0 * * 0". 256@daily Run once a day, "0 0 * * *". 257@midnight (same as @daily) 258@hourly Run once an hour, "0 * * * *". 259@every_minute Run once a minute, "*/1 * * * *". 260@every_second Run once a second. 261.Ed 262.Pp 263The 264.Sq @ 265symbol followed by a numeric value has a special notion of running 266a job that many seconds after completion of the previous invocation of 267the job. 268Unlike regular syntax, it guarantees not to overlap two or more 269invocations of the same job during normal cron execution. 270Note, however, that overlap may occur if the job is running when the file 271containing the job is modified and subsequently reloaded. 272The first run is scheduled for the specified number of seconds after cron 273is started or the crontab entry is reloaded. 274.Sh EXAMPLE CRON FILE 275.Bd -literal 276 277# use /bin/sh to run commands, overriding the default set by cron 278SHELL=/bin/sh 279# mail any output to `paul', no matter whose crontab this is 280MAILTO=paul 281# 282# run five minutes after midnight, every day 2835 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 284# run at 2:15pm on the first of every month -- output mailed to paul 28515 14 1 * * $HOME/bin/monthly 286# run at 10 pm on weekdays, annoy Joe 2870 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 28823 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 2895 4 * * sun echo "run at 5 after 4 every sunday" 290# run at 5 minutes intervals, no matter how long it takes 291@300 svnlite up /usr/src 292# run every minute, suppress logging 293* * * * * -q date 294# run every minute, only send mail if ping fails 295* * * * * -n ping -c 1 freebsd.org 296.Ed 297.Sh SEE ALSO 298.Xr crontab 1 , 299.Xr cron 8 300.Sh EXTENSIONS 301When specifying day of week, both day 0 and day 7 will be considered Sunday. 302.Bx 303and 304.Tn ATT 305seem to disagree about this. 306.Pp 307Lists and ranges are allowed to co-exist in the same field. 308"1-3,7-9" would 309be rejected by 310.Tn ATT 311or 312.Bx 313cron -- they want to see "1-3" or "7,8,9" ONLY. 314.Pp 315Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". 316.Pp 317Names of months or days of the week can be specified by name. 318.Pp 319Environment variables can be set in the crontab. 320In 321.Bx 322or 323.Tn ATT , 324the 325environment handed to child processes is basically the one from 326.Pa /etc/rc . 327.Pp 328Command output is mailed to the crontab owner 329.No ( Bx 330cannot do this), can be 331mailed to a person other than the crontab owner (SysV cannot do this), or the 332feature can be turned off and no mail will be sent at all (SysV cannot do this 333either). 334.Pp 335All of the 336.Sq @ 337directives that can appear in place of the first five fields 338are extensions. 339.Pp 340Command processing can be modified using command options. 341The 342.Sq -q 343option suppresses logging. 344The 345.Sq -n 346option does not mail on successful run. 347.Sh AUTHORS 348.An Paul Vixie Aq Mt paul@vix.com 349.Sh BUGS 350If you are in one of the 70-odd countries that observe Daylight 351Savings Time, jobs scheduled during the rollback or advance may be 352affected if 353.Xr cron 8 354is not started with the 355.Fl s 356flag. 357In general, it is not a good idea to schedule jobs during 358this period if 359.Xr cron 8 360is not started with the 361.Fl s 362flag, which is enabled by default. 363See 364.Xr cron 8 365for more details. 366.Pp 367For US timezones (except parts of AZ and HI) the time shift occurs at 3682AM local time. 369For others, the output of the 370.Xr zdump 8 371program's verbose 372.Fl ( v ) 373option can be used to determine the moment of time shift. 374