4.3BSD-UWisc/man/cat8/cron.8

CRON(8)             UNIX Programmer's Manual              CRON(8)



NAME
     cron - clock daemon

SYNOPSIS
     /etc/cron

DESCRIPTION
     _C_r_o_n executes commands at specified dates and times accord-
     ing 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 _c_r_o_n never exits, it should
     only be executed once.  This is best done by running _c_r_o_n
     from the initialization process through the file /etc/rc;
     see _i_n_i_t(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:

     o+ minute (0-59)
     o+ hour (0-23)
     o+ day of the month (1-31)
     o+ month of the year (1-12)
     o+ day of the week (1-7 with 1 = Monday)

     Each of these patterns may contain:

     o+ a number in the range above
     o+ two numbers separated by a minus meaning a range inclusive
     o+ a list of numbers separated by commas meaning any of the
       numbers
     o+ 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, includ-
     ing 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 translated to a new-line
     character.

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

UW MODIFICATIONS
     A backslash before a ``%'' character causes it to be passed
     through as a percent rather than a newline.  A backslash
     before a newline allows line continuations.  Comments may
     appear in the crontab files and are denoted by a pound sign
     (``#'') at the beginning of the line.





Printed 12/27/86          May 16, 1986                          1






CRON(8)             UNIX Programmer's Manual              CRON(8)



     _C_r_o_n will log all errors during execution via the syslog(3)
     facility.  These errors include nonpriveleged execution
     (only root may start cron), nonexistant users listed in the
     crontab files, and programs that exit abnormally.

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















































Printed 12/27/86          May 16, 1986                          2