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cron(8) [bsd man page]

CRON(8) 						      System Manager's Manual							   CRON(8)

NAME
cron - clock daemon SYNOPSIS
/usr/sbin/cron DESCRIPTION
Cron executes commands at specified dates and times according to the instructions in the files /etc/crontab and /etc/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: 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, 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 translated to a new-line character. Both crontab files are checked by cron every minute, on the minute. FILES
/etc/crontab /etc/crontab.local 7th Edition October 23, 1996 CRON(8)

Check Out this Related Man Page

crontab(5)							File Formats Manual							crontab(5)

Name
       crontab - clock daemon table file

Syntax
       /usr/lib/crontab

Description
       The  command  executes  at  specified dates and times according to the instructions in the file. The file consists of lines with six fields
       each.  The format for a line is as follows:

	      minute hour day month weekday command

       The following list defines each field in the line:

       minute (0-59)  The exact minute that the command sequence executes.

       hour (0-23)    The hour of the day that the command sequence executes.

       day (1-31)     The day of the month that the command sequence executes.

       month (1-12)   The month of the year that the command sequence executes.

       weekday (1-7)  The day of the week that the command sequence executes. Monday = 1, Tuesday = 2, and so forth.

       command	      The complete command sequence variable that is to be executed.  Note that the command string must conform  to  Bourne  shell
		      syntax.

       The first five integer fields may be specified as follows:

       o   A single number in the specified range

       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 string that is executed by the shell at the specified times.  A percent sign (%) in this field is translated to a new-
       line character.	Only the first line of the command field, up to a percent sign (%) or end of line, is executed by the  shell.	The  other
       lines are made available to the command as standard input.

Examples
       The following example is part of a file:
       # periodic things
       0,15,30,45 * * * * (echo '^M' `date`; echo '') >/dev/console
       0,15,30,45 * * * * /usr/lib/atrun

       # daily stuff
       5 4 * * * sh /usr/adm/newsyslog
       15 4 * * * ( cd /usr/preserve; find . -mtime +7 -a -exec rm -f {} ; )
       20 4 * * * find /usr/msgs -mtime +21 -a ! -perm 444 -a ! -name bounds
	    -a -exec rm -f {} ;

       # NOTE: The above line is wrapped.

       # local cleanups
       30 4 * * * find /usr/spool/mqueue -type f -mtime +5 -name df-exec rm {} ;
       35 4 * * * find /usr/spool/mqueue -type f -mtime +5 -name tf-exec rm {} ;
       40 4 * * * find /usr/spool/rwho -type f -mtime +21 -exec rm {} ;
       #

       # redirecting error output
       0 17 * * 1,3,5 /bin/tar -cv /usr/sysads/smith > /dev/console 2>&1
       #

Files
See Also
       sh(1), cron(8)
       Guide to System Environment Setup

																	crontab(5)

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