bcrontab

CRONTAB(5)                     File Formats Manual                    CRONTAB(5)



NAME
       crontab - tables for driving bcron

DESCRIPTION
       A crontab file contains instructions to the bcron-sched(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.

       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
       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 double, but
       matching) to preserve leading or trailing blanks.

       Several environment variables are set up automatically by the
       bcron-exec(8) program.  SHELL is set to /bin/sh, and LOGNAME, USER, and
       HOME are set from the /etc/passwd line of the crontab's owner.

       In addition to LOGNAME, USER, HOME, and SHELL, bcron-exec(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.  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
       doesn't do aliasing, and UUCP usually doesn't 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 if this is the system crontab file,
       followed by a command.  Commands are executed by bcron-sched(8) when the
       minute, hour, and month of year fields match the current time, and at
       least one of the two day fields (day of month, or day of week) match the
       current time (see ``Note'' below).  Jobs scheduled during non-existent
       times, such as "missing hours" during daylight savings conversion, will
       be scheduled at some point shortly after the non-existent time.  Jobs
       scheduled during repeating times, such as "duplicate hours" during
       daylight savings conversion, will be scheduled only once (unless they
       would repeat anyways, such as jobs that run every minute or hour).

       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 doesn't
       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 will be executed by /bin/sh
       or by the shell specified in the SHELL variable of the cronfile.

       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, aren't
       *), 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.

EXAMPLE CRON FILE
       # use /bin/sh to run commands, no matter what /etc/passwd says
       SHELL=/bin/sh
       # mail any output to `bruce@example.com', no matter whose crontab this is
       MAILTO=bruce@example.com
       #
       # 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 bruce (above)
       15 14 1 * *     $HOME/bin/monthly
       23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
       5 4 * * sun     echo "run at 5 after 4 every sunday"

FILES
       /etc/crontab        System crontab file

       /etc/cron.d/        System crontab directory

SEE ALSO
       bcron-sched(8), bcron-spool(8), bcrontab(1)

EXTENSIONS
       When specifying day of week, both day 0 and day 7 will be considered
       Sunday.  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"
       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 processes is basically the one from /etc/rc.

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

AUTHOR
       Paul Vixie <vixie@isc.org>
       Charles Cazabon <charlesc-cronman @ discworld.dyndns.org>
       Bruce Guenter <bruce@untroubled.org>



                                      bcron                           CRONTAB(5)