Provided by: bcron_0.09-12_amd64 bug

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 <bruceg@em.ca>

                                              bcron                                    CRONTAB(5)