12-19-2008
cron will use a crontab. You will need to run the crontab -e command to edit the crontab. The cron file has a format of 5 date fields followed by the command you want to execute.
The date fields are laid out as
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 can be an asterisk (*), which always stands for first-last.
So to run you command every 24 hrs at 11:00pm you would edit the crontab and enter
00 11 * * * chmod 666 /www/test/htdocs
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CRONTAB(1) General Commands Manual CRONTAB(1)
NAME
crontab - maintain crontab files for individual users (ISC Cron V4.1)
SYNOPSIS
crontab [-u user] file
crontab [-u user] [-l | -r | -e]
DESCRIPTION
Crontab is the program used to install, deinstall or list the tables used to drive the cron(8) daemon in ISC Cron. Each user can have
their own crontab, and though these are files in /var, they are not intended to be edited directly.
If the cron.allow file exists, then you must be listed therein in order to be allowed to use this command. If the cron.allow file does not
exist but the cron.deny file does exist, then you must not be listed in the cron.deny file in order to use this command. If neither of
these files exists, only the super user will be allowed to use this command.
If the -u option is given, it specifies the name of the user whose crontab is to be tweaked. If this option is not given, crontab examines
"your" crontab, i.e., the crontab of the person executing the command. Note that su(8) can confuse crontab and that if you are running
inside of su(8) you should always use the -u option for safety's sake.
The first form of this command is used to install a new crontab from some named file or standard input if the pseudo-filename ``-'' is
given.
The -l option causes the current crontab to be displayed on standard output.
The -r option causes the current crontab to be removed.
The -e option is used to edit the current crontab using the editor specified by the VISUAL or EDITOR environment variables. After you exit
from the editor, the modified crontab will be installed automatically.
SEE ALSO
crontab(5), cron(8)
FILES
/etc/cron.allow
/etc/cron.deny
STANDARDS
The crontab command conforms to IEEE Std1003.2-1992 (``POSIX''). This new command syntax differs from previous versions of Vixie Cron, as
well as from the classic SVR3 syntax.
DIAGNOSTICS
A fairly informative usage message appears if you run it with a bad command line.
AUTHOR
Paul Vixie <vixie@isc.org>
4th Berkeley Distribution 29 December 1993 CRONTAB(1)