MAN page from openSUSE Tumbleweed svcron-1.0-23.2.x86_64.rpm

CRONTAB

Section: File Formats (5)
Updated: 24 January 1994
Index

NAME

crontab - tables for driving svcron (based on Vixie Cron)

DESCRIPTION

A crontab file contains instructions for the svcron (8) daemonof the general form: ``run this command at this time on this date''. Eachuser has their own crontab, and commands in any given crontab will beexecuted as the user who owns the crontab.

Blank lines and leading spaces and tabs are ignored. Lines whose firstnon-space character is a pound-sign (#) are comments, and are ignored.Note that comments are not allowed on the same line as svcron commands, sincethey will be taken to be part of the command. Similarly, comments are notallowed on the same line as environment variable settings.

An active line in a crontab will be either an environment setting or a svcroncommand. An environment setting is of the form,

name = value

where the spaces around the equal-sign (=) are optional, and any subsequentnon-leading spaces in value will be part of the value assigned toname. The value string may be placed in quotes (single ordouble, but matching) to preserve leading or trailing blanks.

Several environment variables are set up automatically by thesvcron (8) daemon. SHELL is set to /bin/sh, andLOGNAME and HOME are set from the /etc/passwd line of thecrontab's owner. HOME and SHELL may be overridden by settingsin the crontab; LOGNAME may not.

(Another note: the LOGNAME variable is sometimes called USER onBSD systems. On these systems, USER will be set also.)

In addition to LOGNAME, HOME, and SHELL, svcron (8)will look at MAILTO if it has any reason to send mail as a result ofrunning commands in ``this'' crontab. If MAILTO is defined (andnon-empty), mail is sent to the user so named. If MAILTO is definedbut empty (MAILTO=""), no mail will be sent. Otherwise mail is sentto the owner of the crontab. This option is useful if you decide on/bin/mail instead of /usr/lib/sendmail as your mailer when you installsvcron -- /bin/mail doesn't do aliasing, and UUCP usually doesn't read itsmail.

The format of a svcron command is very much the V7 standard, with a numberof upward-compatible extensions. Each line has five time and date fields,followed by a user name if this is the system crontab file, followed by acommand. Commands are executed by svcron (8) when the minute, hour,and month of year fields match the current time, and when at leastone of the two day fields (day of month, or day of week) match the currenttime (see ``Note'' below). svcron (8) examines svcron entries onceevery minute. The time and date fields are:

field          allowed values

-----         --------------

minute        0-59

hour          0-23

day of month  1-31 (or $, see below)

month         0-12 (or names, see below)

day of week   0-7 (0 or 7 is Sun, or use names)

A field may be an asterisk (*), which always stands for ``first-last''.

Ranges of numbers are allowed. Ranges are two numbers separated with ahyphen. The specified range is inclusive. For example, 8-11 for an``hours'' entry specifies execution at hours 8, 9, 10 and 11.

Lists are allowed. A list is a set of numbers (or ranges) separated bycommas. Examples: ``1,2,5,9'', ``0-4,8-12''.

Step values can be used in conjunction with ranges. Following a range with``/<number>'' specifies skips of the number's value through the range. Forexample, ``0-23/2'' can be used in the hours field to specify commandexecution every other hour (the alternative in the V7 standard is``0,2,4,6,8,10,12,14,16,18,20,22''). Steps are also permitted after anasterisk, so if you want to say ``every two hours'', just use ``*/2''.

Names can also be used for the ``month'' and ``day of week'' fields. Usethe first three letters of the particular day or month (case doesn'tmatter). Ranges of names are not allowed.

The ``sixth'' field (the rest of the line) specifies the command to be run.The entire command portion of the line, up to a newline or % character,will be executed by /bin/sh or by the shell specified in the SHELL variableof the crontab file. Percent-signs (%) in the command, unless escaped withbackslash (\), will be changed into newline characters, and all data afterthe first % will be sent to the command as standard input.

Note: The day of a command's execution can be specified by twofields --- day of month, and day of week. If both fields are restricted(i.e., are not *), the command will be run when either field matchesthe current time. For example,

``30 4 1,15 * 5''

would cause a command to be run at 4:30 am on the 1st and 15th of eachmonth, plus every Friday.

Note: The day-of-month can be given as $, in which case it matches the lastday of the current month.

EXTENSIONS

These special time specification "nicknames" which replace the 5 initialtime and date fields, and are prefixed with the '@' character, aresupported:

@reboot    :    Run once after svcron(8) startup.@yearly    :    Run once a year, ie.  "0 0 1 1 *".@annually  :    Run once a year, ie.  "0 0 1 1 *".@monthly   :    Run once a month, ie. "0 0 1 * *".@weekly    :    Run once a week, ie.  "0 0 * * 0".@daily     :    Run once a day, ie.   "0 0 * * *".@midnight  :    Run once a day, ie.   "0 0 * * *".@hourly    :    Run once an hour, ie. "0 * * * *".

When specifying day of week, both day 0 and day 7 will be consideredSunday.

Lists and ranges are allowed to co-exist in the same field.

Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".

Names of months or days of the week can be specified by name.

Environment variables can be set in the crontab.

Command output is mailed to the crontab owner, can be mailed to a personother than the crontab owner, or the feature can be turned off and no mailwill be sent at all.

EXAMPLE CRONTAB FILE

# use /bin/sh to run commands, no matter what /etc/passwd saysSHELL=/bin/sh# mail any output to `paul', no matter whose crontab this isMAILTO=paul## run five minutes after midnight, every day5 0 * * *       $HOME/bin/daily.job >> $HOME/tmp/out 2>&1# run at 2:15pm on the first of every month -- output mailed to paul15 14 1 * *     $HOME/bin/monthly# run at 10 pm on weekdays, annoy Joe0 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"

AUTHOR

Original code by Paul Vixie <vixieAATTisc.org>,modified by Manvendra Bhangui <manvendraAATTindimail.org>

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