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CRONTAB(5)		    BSD	File Formats Manual		    CRONTAB(5)

     crontab --	tables for driving cron

     A crontab file contains instructions to the cron(8) daemon	of the general
     form: ``run this command at this time on this date''.  Each user has
     their own crontab,	and commands in	any given crontab will be executed as
     the user who owns the crontab.  Uucp and News will	usually	have their own
     crontabs, eliminating the need for	explicitly running su(1) as part of a
     cron command.

     Blank lines and leading spaces and	tabs are ignored.  Lines whose first
     non-space character is a pound-sign (#) are comments, and are ignored.
     Note that comments	are not	allowed	on the same line as cron 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.

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

	 name =	value

     where the spaces around the equal-sign (=)	are optional, and any subse-
     quent non-leading spaces in value will be part of the value assigned to
     name.  The	value string may be placed in quotes (single or	double,	but
     matching) to preserve leading or trailing blanks.	The name string	may
     also be placed in quote (single or	double,	but matching) to preserve
     leading, trailing or inner	blanks.

     Several environment variables are set up automatically by the cron(8)
     daemon.  SHELL is set to /bin/sh, PATH is set to /usr/bin:/bin, and
     LOGNAME and HOME are set from the /etc/passwd line	of the crontab's
     owner.  HOME, PATH	and SHELL may be overridden by settings	in the
     crontab; LOGNAME may not.

     (Another note: the	LOGNAME	variable is sometimes called USER on BSD sys-
     tems...  On these systems,	USER will be set also).

     In	addition to LOGNAME, HOME, PATH, and SHELL, cron(8) will look at
     MAILTO if it has any reason to send mail as a result of running commands
     in	``this'' crontab.  If MAILTO is	defined	(and non-empty), mail is sent
     to	the user so named.  MAILTO may also be used to direct mail to multiple
     recipients	by seperating recipient	users with a comma.  If	MAILTO is de-
     fined but empty (MAILTO=""), no mail will be sent.	 Otherwise mail	is
     sent to 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 install
     cron -- /bin/mail does not	do aliasing, and UUCP usually does not read
     its mail.

     The format	of a cron command is very much the V7 standard,	with a number
     of	upward-compatible extensions.  Each line has five time and date
     fields, followed by a user	name (with optional ``:<group>'' and ``/<lo-
     gin-class>'' suffixes) if this is the system crontab file,	followed by a
     command.  Commands	are executed by	cron(8)	when the minute, hour, and
     month of year fields match	the current time, and when at least one	of the
     two day fields (day of month, or day of week) matches the current time
     (see ``Note'' below).  cron(8) examines cron entries once every minute.
     The time and date fields are:

	   field	 allowed values
	   -----	 --------------
	   minute	 0-59
	   hour		 0-23
	   day of month	 1-31
	   month	 1-12 (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 a
     hyphen.  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 by
     commas.  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.  For example, ``0-23/2'' can be used in the	hours field to specify
     command execution 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 an
     asterisk, 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.  Use
     the first three letters of	the particular day or month (case does not
     matter).  Ranges or lists 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 %	char-
     acter, will be executed by	/bin/sh	or by the shell	specified in the SHELL
     variable of the cronfile.	Percent-signs (%) in the command, unless es-
     caped with	backslash (\), will be changed into newline characters,	and
     all data after the	first %	will be	sent to	the command as standard	input.

     Note: The day of a	command's execution can	be specified by	two fields --
     day of month, and day of week.  If	both fields are	restricted (ie,	are
     not *), the command will be run when either field matches the 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 each month,	plus every Friday.

     Instead of	the first five fields, one of eight special strings may	ap-

	   string	   meaning
	   ------	   -------
	   @reboot	   Run once, at	startup.
	   @yearly	   Run once a year, "0 0 1 1 *".
	   @annually	   (same as @yearly)
	   @monthly	   Run once a month, "0	0 1 * *".
	   @weekly	   Run once a week, "0 0 * * 0".
	   @daily	   Run once a day, "0 0	* * *".
	   @midnight	   (same as @daily)
	   @hourly	   Run once an hour, "0	* * * *".

     # use /bin/sh to run commands, overriding the default set by cron
     # mail any	output to `paul', no matter whose crontab this is
     # 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 -- output mailed to paul
     15	14 1 * *     $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"

     crontab(1), cron(8)

     When specifying day of week, both day 0 and day 7 will be considered Sun-
     day.  BSD and ATT seem to disagree	about this.

     Lists and ranges are allowed to co-exist in the same field.  "1-3,7-9"
     would be rejected by ATT or BSD cron -- they want to see "1-3" or "7,8,9"

     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.  In BSD or ATT, the en-
     vironment handed to child processes is basically the one from /etc/rc.

     Command output is mailed to the crontab owner (BSD	cannot do this), can
     be	mailed to a person other than the crontab owner	(SysV cannot do	this),
     or	the feature can	be turned off and no mail will be sent at all (SysV
     cannot do this either).

     All of the	`@' commands that can appear in	place of the first five	fields
     are extensions.

     Paul Vixie	<>

     If	you are	in one of the 70-odd countries that observe Daylight Savings
     Time, jobs	scheduled during the rollback or advance will be affected.  In
     general, it is not	a good idea to schedule	jobs during this period.

     For US timezones (except parts of IN, AZ, and HI) the time	shift occurs
     at	2AM local time.	 For others, the output	of the zdump(8)	program's ver-
     bose (-v) option can be used to determine the moment of time shift.

BSD				 July 31, 2005				   BSD


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