# crontab(5)

    NAME
         crontab - table of jobs to be performed by cron

    SYNOPSIS
         /usr/lib/crontab
         /usr/local/lib/crontab
         /var/lib/crontab
         /var/opt/name/lib/crontab  (Minix-vmd only)
         /usr/spool/crontabs/user

    DESCRIPTION
         The cron(8) daemon runs jobs at regular intervals.  These jobs are listed
         in  crontab  files.   The  format  of  entries in a crontab file are five
         fields of numbers specifying the minute (0-59), hour (0-23), day  of  the
         month  (1-31),  month  (1-12),  and day of the week (0-6 with 0 = Sunday)
         that a task must be executed.  The task to be executed follows as a shell
         command.

         The time numbers can be  given  as  a  comma  separated  list  of  simple
         numbers,  ranges  ("2-5"  is  the  same as "2,3,4,5"), and repeats ("2:5"
         means "2,7,12,17,22" in the hour field).  A repeat is cyclic affair, i.e.
         2:5  and 12:5 are the same thing.  A single "*" can be used in a field to
         indicate all valid numbers in that field, so it translates  to  "always".
         In  the  minute  field  you  can  use "?" for the current minute that the
         crontab file is loaded.  It can be used in  a  repeat,  i.e.  "?:10"  for
         every  10  minutes.   This  keeps  machines  with identical crontabs from
         executing tasks at exactly the same time, causing a burst of  traffic  if
         anything is done over a network.

         If a given time is valid in all five fields then a command  is  executed.
         Here are a few examples that illustrate the possibilities:

         # min hour mday mon wday command
            ?   3    *    *   *   /usr/etc/daily  # Daily system cleanup
            0   *    *    *   *   date            # Print date on the hour
           30   4    *    *  2-6  /var/etc/backup # After workdays on 4:30
            0   9   25   12   *   -u ast sing     # Andy sings on Xmas morning
            0   0   13    *   5   echo Beware!    # For the superstitious

         The command may optionally be prefixed by -u user to specify under  which
         user  the  command  should  be  run.  Commands from crontabs in the spool
         directory are always run under the id of the crontab's owner, the -u flag
         is ignored.

         A command can be placed on the same line as the time fields,  or  on  the
         next  line  indented  by  one  TAB character.  (A TAB, not eight spaces.)
         More TAB indented lines can be added for a multiline command.   The  tabs
         are  removed  from the command when passed to the shell.  If a command is
         put on the same line as the  time  fields  then  percent  characters  are
         changed  into newlines, this is not done for a TAB indented command.  The
         following three entries give the same output:

              0 12  *  *  *   echo 'Hello'; echo '  World!'
              #1
              0 12  *  *  *   echo 'Hello%  World!'  #2
              0 12  *  *  *        #3
                      cat <<EOF    #4
                      Hello
                        World!
                      EOF

         Comments start with a "#" character  and  continue  until  end  of  line.
         They, excess whitespace, and empty lines are ignored.  Of the comments in
         the example above #1 and #3 are ignored by cron, but #2 and  #4  are  not
         recognized  as comments, but are seen as part of a command and are passed
         to the shell who then happens to ignore them.  There is no interpretation
         of  command  characters  other  than the percent in a oneliner.  The time
         fields must all be on the same line.

    FILES

         /usr/lib/crontab         Main Minix crontab file.

         /usr/local/lib/crontab   Local jobs for all systems in an organization.

         /var/lib/crontab         System specific jobs.

         /var/opt/name/lib/crontab
                                  Per package jobs for Minix-vmd.

         /usr/lib/packages        List of installed packages.

         /usr/spool/crontabs/user Per user jobs.

    SEE ALSO
         crontab(1), cron(8).

    NOTES
         The "?" in the minute field, the repeat field (e.g. "2:5"), TAB  indented
         multiline   commands   and   the  -u  option  are  unique  to  this  cron
         implementation.  This doesn't mean you shouldn't use these features,  but
         just that you should be aware of the differences with other systems.  You
         are even advised to use these features and avoid  the  percent  hack  for
         multiline commands.

         Other crons allow one to specify input to a job in  some  way,  something
         this  cron  can't.   Simply  use  the << shell feature to do that.  Other
         crons often choke on empty lines.

         It is a common bug to use 0 for Sunday instead of  7.   This  cron,  like
         most other crons out there accepts this without comment.

         A job is not reissued until a previous instance of it  has  exited.   The
         next  time  to execute is computed from the previous time it ran.  If job
         issuing lags behind on the system time then the next time to  run  it  is
         computed from the current system time.

    AUTHOR
         Kees J. Bot (kjb@cs.vu.nl)