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

NAME
     crontab -- tables for driving cron

DESCRIPTION
     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, elimi-nating eliminating
     nating the need for explicitly running su(1) as part of a cron command.

     (Darwin note: Although cron(8) and crontab(5) are officially supported under Darwin, their functional-ity functionality
     ity has been absorbed into launchd(8), which provides a more flexible way of automatically executing
     commands.  See launchd.plist(5) for more information.)

     Blank lines and leading spaces and tabs are ignored.  Lines whose first non-space character is a pound-sign poundsign
     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 subsequent non-leading spaces in value
     will be part of the value assigned to name.  The value string may be placed in quotes (single or dou-ble, double,
     ble, 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,
     and LOGNAME and HOME are set from the /etc/passwd line of the crontab's owner.  HOME and SHELL may be
     overridden by settings in the crontab; LOGNAME may not.

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

     In addition to LOGNAME, HOME, 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.  If MAILTO is defined but empty (MAILTO=""), no mail will be sent.  Other-wise Otherwise
     wise 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 exten-sions. extensions.
     sions.  Each line has five time and date fields, followed by a user name (with optional ``:<group>''
     and ``/<login-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 -------------minute
           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 % character, will be executed by /bin/sh or by the shell specified in
     the SHELL variable of the cronfile.  Percent-signs (%) in the command, unless escaped with backslash
     (\), will be changed into newline characters, and all data after the first % will be sent to the com-mand command
     mand as standard input.  The command can optionally be prefixed by ``@AppleNotOnBattery '' to tell cron
     not to run the command when functioning on battery power.  For example, the ``sixth'' field when using
     this option would appear something like ``@AppleNotOnBattery /usr/bin/touch /tmp/foo''

     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 appear:

           string          meaning
           ------          -------@reboot ------@reboot
           @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 * * * *".

EXAMPLE CRON FILE
     # use /bin/sh to run commands, overriding the default set by cron
     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 -- 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"

SEE ALSO
     crontab(1), cron(8), launchd.plist(5), launchctl(1), launchd(8)

EXTENSIONS
     When specifying day of week, both day 0 and day 7 will be considered Sunday.  BSD and ATT seem to dis-agree disagree
     agree 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" ONLY.

     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 environment handed to child pro-cesses processes
     cesses 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.

AUTHORS
     Paul Vixie <paul@vix.com>

BUGS
     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 verbose (-v) option can be used to determine the moment of time
     shift.

BSD                              July 31, 2005                             BSD

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