.\"/* Copyright 1988,1990,1993,1994 by Paul Vixie .\" * All rights reserved .\" */ .\" .\" Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") .\" Copyright (c) 1997,2000 by Internet Software Consortium, Inc. .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT .\" OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .\" $OpenBSD: crontab.5,v 1.41 2020/04/18 17:11:40 jmc Exp $ .\" .Dd $Mdocdate: April 18 2020 $ .Dt CRONTAB 5 .Os .Sh NAME .Nm crontab .Nd tables for driving cron .Sh DESCRIPTION A .Nm file contains instructions to the .Xr cron 8 daemon of the general form: .Dq at these times on these dates run this command . There may be a system .Nm and each user may have their own .Nm . Commands in any given .Nm will be executed either as the user who owns the .Nm or, in the case of the system .Nm crontab , as the user specified on the command line. .Pp While a .Nm is a text file, it is not intended to be directly edited. Creation, modification, and removal of a .Nm should be done using .Xr crontab 1 . .Pp Blank lines, leading spaces, and tabs are ignored. Lines whose first non-space character is a pound sign .Pq Ql # are comments, and are ignored. Note that comments are not allowed on the same line as .Xr cron 8 commands, since they will be taken to be part of the command. Similarly, comments are not allowed on the same line as environment variable settings. .Pp An active line in a .Nm is either an environment variable setting or a .Xr cron 8 command. .Pp Environment variable settings create the environment any command in the .Nm is run in. An environment variable setting is of the form: .Pp .Dl name = value .Pp The spaces around the equal sign .Pq Ql = are optional, and any subsequent non-leading spaces in .Ar value will be part of the value assigned to .Ar name . The .Ar value string may be placed in quotes .Pq single or double , but matching to preserve leading or trailing blanks. .Pp Lines in the system .Nm have six fixed fields, an optional flags field, and a command, in the form: .Bd -ragged -offset indent .Ar minute .Ar hour .Ar day-of-month .Ar month .Ar day-of-week .Ar user .Op Ar flags .Ar command .Ed .Pp While lines in a user .Nm have five fixed fields, an optional flags field, and a command, in the form: .Bd -ragged -offset indent .Ar minute .Ar hour .Ar day-of-month .Ar month .Ar day-of-week .Op Ar flags .Ar command .Ed .Pp Fields are separated by blanks or tabs. The command may be one or more fields long. The allowed values for the fields are: .Bl -column "day-of-month" "allowed values" -offset indent .It Sy field Ta Sy allowed values .It Ar minute Ta * or 0\(en59 .It Ar hour Ta * or 0\(en23 .It Ar day-of-month Ta * or 1\(en31 .It Ar month Ta * or 1\(en12 or a name (see below) .It Ar day-of-week Ta * or 0\(en7 or a name (0 or 7 is Sunday) .It Ar user Ta a valid username .It Op Ar flags Ta runtime flags, denoted with '-' .It Ar command Ta text .El .Pp Lists are allowed. A list is a set of numbers (or ranges) separated by commas. For example, .Dq 1,2,5,9 or .Dq 0\(en4,8\(en12 . .Pp Ranges of numbers are allowed. Ranges are two numbers separated with a hyphen. The specified range is inclusive. For example, 8\(en11 for an .Ar hour entry specifies execution at hours 8, 9, 10 and 11. .Pp A random value (within the legal range) may be obtained by using the .Ql ~ character in a field. The interval of the random value may be specified explicitly, for example .Dq 0~30 will result in a random value between 0 and 30 inclusive. If either (or both) of the numbers on either side of the .Ql ~ are omitted, the appropriate limit (low or high) for the field will be used. .Pp Step values can be used in conjunction with ranges (but not random ranges which represent a single number). Following a range with .No / Ns Ar number specifies skips of .Ar number through the range. For example, .Dq 0\(en23/2 can be used in the .Ar hour field to specify command execution every other hour. Steps are also permitted after an asterisk, so to say .Dq every two hours , just use .Dq */2 . .Pp An asterisk .Pq Ql * is short form for a range of all allowed values. .Pp Names can be used in the .Ar month and .Ar day-of-week fields. Use the first three letters of the particular day or month (case doesn't matter). Ranges or lists of names are not allowed. .Pp Some .Ar flags relating to process operation can be provided before the .Ar command field. Flags are denoted with '-' and may be combined. .Bl -tag -width Ds .It Fl n Ar command No mail is sent after a successful run. The execution output will only be mailed if the command exits with a non-zero exit code. The .Fl n option is an attempt to cure potentially copious volumes of mail coming from .Xr cron 8 . .It Fl q Ar command Execution will not be logged. .It Fl s Ar command Only a single instance of .Ar command will be run concurrently. Additional instances of .Ar command will not be scheduled until the earlier one completes. .El .Pp The .Ar command field (the rest of the line) is the command to be run. The entire command portion of the line, up to a newline or % character, will be executed by .Pa /bin/sh or by the shell specified in the .Ev SHELL variable of the .Nm crontab . Percent signs .Pq Ql % in the command, unless escaped with a backslash .Pq Ql \e , will be changed into newline characters, and all data after the first .Ql % will be sent to the command as standard input. .Pp Commands are executed by .Xr cron 8 when the .Ar minute , .Ar hour , and .Ar month fields match the current time, .Em and when at least one of the two day fields .Po Ar day-of-month or .Ar day-of-week Pc , match the current time. .Pp Note: The day of a command's execution can be specified by two fields \(em .Ar day-of-month and .Ar day-of-week . If both fields are restricted (i.e. aren't *), the command will be run when .Em either field matches the current time. For example, .Pp .Dl 30 4 1,15 * 5 .Pp would cause a command to be run at 4:30 am on the 1st and 15th of each month, plus every Friday. .Pp Instead of the first five fields, one of eight special strings may appear: .Bl -column "@midnight" "meaning" -offset indent .It Sy string Ta Sy meaning .It @reboot Ta Run once, at startup. .It @yearly Ta Run every January 1 (0 0 1 1 *). .It @annually Ta The same as @yearly. .It @monthly Ta Run the first day of every month (0 0 1 * *). .It @weekly Ta Run every Sunday (0 0 * * 0). .It @daily Ta Run every midnight (0 0 * * *). .It @midnight Ta The same as @daily. .It @hourly Ta Run every hour, on the hour (0 * * * *). .El .Sh ENVIRONMENT .Bl -tag -width "LOGNAMEXXX" .It Ev HOME Set from the user's .Pa /etc/passwd entry. May be overridden by settings in the .Nm . .It Ev LOGNAME Set from the user's .Pa /etc/passwd entry. May not be overridden by settings in the .Nm . .It Ev MAILTO If .Ev MAILTO is defined and non-empty, mail is sent to the user so named. If .Ev MAILTO is defined but empty .Pq Ev MAILTO = Qq , no mail will be sent. Otherwise mail is sent to the owner of the .Nm . This is useful for pseudo-users that lack an alias that would otherwise redirect the mail to a real person. .It Ev SHELL Set to .Pa /bin/sh . May be overridden by settings in the .Nm . .It Ev USER Set from the user's .Pa /etc/passwd entry. May not be overridden by settings in the .Nm . .El .Sh FILES .Bl -tag -width "/var/cron/tabs/XXX" -compact .It Pa /etc/crontab System crontab. .It Pa /var/cron/tabs/ Ns Aq Ar user User crontab. .El .Sh EXAMPLES .Bd -literal # use /bin/sh to run commands, no matter what /etc/passwd says SHELL=/bin/sh # mail any output to `paul', no matter whose crontab this is MAILTO=paul # # run five minutes after midnight, every day 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 # run at 2:15pm on the first of every month -- job output will be sent # to paul, but only if $HOME/bin/monthly exits with a non-zero exit code 15 14 1 * * -n $HOME/bin/monthly # run at 10 pm on weekdays, annoy Joe 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 5 4 * * sun echo "run at 5 after 4 every sunday" # run hourly at a random time within the first 30 minutes of the hour 0~30 * * * * /usr/libexec/spamd-setup .Ed .Sh SEE ALSO .Xr crontab 1 , .Xr cron 8 .Sh STANDARDS The .Nm file format is compliant with the .St -p1003.1-2008 specification. The behaviours described below are all extensions to that standard: .Bl -dash .It The .Ar day-of-week field may use 7 to represent Sunday. .It Ranges may include .Dq steps . .It Random intervals are supported using the .Ql ~ character. .It Months or days of the week can be specified by name. .It Environment variables can be set in a crontab. .It Command output can be mailed to a person other than the crontab owner, or the feature can be turned off and no mail will be sent at all. .It All of the .Ql @ commands that can appear in place of the first five fields. .It All of the .Op Fl nqs flags. .El .Sh AUTHORS .Nm was written by .An Paul Vixie Aq Mt vixie@isc.org .