4.3BSD - /usr/man/cat8/cron.0

CRON(8)                                                                CRON(8)


NAME
       cron - clock daemon

SYNOPSIS
       /etc/cron

DESCRIPTION
       Cron  executes  commands  at specified dates and times according to the
       instructions in the files /usr/lib/crontab and  /usr/lib/crontab.local.
       None,  either  one,  or both of these files may be present.  Since cron
       never exits, it should only be executed once.  This  is  best  done  by
       running  cron from the initialization process through the file /etc/rc;
       see init(8).

       The crontab files consist of lines of seven fields  each.   The  fields
       are  separated  by spaces or tabs.  The first five are integer patterns
       to specify:

       · minute (0-59)

       · hour (0-23)

       · day of the month (1-31)

       · month of the year (1-12)

       · day of the week (1-7 with 1 = Monday)

       Each of these patterns may contain:

       · a number in the range above

       · two numbers separated by a minus meaning a range inclusive

       · a list of numbers separated by commas meaning any of the numbers

       · an asterisk meaning all legal values

       The sixth field is a user name: the  command  will  be  run  with  that
       user’s uid and permissions.  The seventh field consists of all the text
       on a line following the sixth field, including spaces  and  tabs;  this
       text  is  treated  as  a  command which is executed by the Shell at the
       specified times.  A percent character (‘‘%’’) in this field  is  trans‐
       lated to a new-line character.

       Both crontab files are checked by cron every minute, on the minute.

FILES
       /usr/lib/crontab
       /usr/lib/crontab.local


7th Edition                      May 16, 1986                          CRON(8)