[ic] IC Jobs question
Grant
listbox at email.com
Thu Oct 23 11:37:19 EDT 2003
> found via 15 seconds on Google: Credit to the Authors, Not Me,
> Probably credit
> to RedHat..
>
> Cron
> Cron is a handy little utility that helps the system
> administrator automate
> repetative tasks.
>
> Cron is controlled by a set of files called "crontabs". There is
> the master
> file in /etc/crontab (which in Red Hat Linux is set up a little different
> than other *nixes), along with crontab files for the users in
> /var/spool/cron/. In the latter directory, the files are given
> the same name
> as a user's login ID.
>
> Crontab location:
> /var/spool/cron
> /etc/crontab
>
> In Red Hat Linux, it is a little easier for the sysadmin to set
> up cron jobs
> than in other distributions. The /etc/crontab file automatically executes
> items in several subdirectories at regular periods.
>
> /etc/cron.hourly
> /etc/cron.daily
> /etc/cron.weekly
> /etc/cron.monthly
>
> All the sysadmin needs to do is drop a shell script or a link to
> an executable
> in one of the directories and it will automatically be run at the
> appropriate
> time.
>
> Setting up a user-level crontab is somewhat different. The files in
> /var/spool/cron are not edited directly. Instead, a program
> called "crontab"
> is used to manipulate them. Depending on system security, all users, only
> some, or just the root user will be able to use crontab (see man crontab
> /etc/cron.allow and /etc/cron.deny for more information).
> SYNOPSIS crontab [
> -u user ] file
> crontab [ -u user ] { -l | -r | -e }
>
>
> file store the specified file as the current crontab
> -u user the crontab file being manipulated is for
> -l display the current crontab
> -r remove current crontab
> -e edit the current crontab (editor depends on system
> variables and will probably be vi unless your sysadmin
> has changed it).
>
> If you are not familiar with the systemwide default editor, it is
> probably
> best to create/edit the file with one you are familiar with and
> use the file
> option with the first command.
>
> Crontab configuration: Blank lines, leading spaces, and tabs are ignored.
> Lines that start with a # are comments and are ignored. Comments are not
> allowed to be on the same line as cron commands; they will be
> assumed to be
> part of the command. Comments are not allowed on the same line as
> environment
> settings for similar reasons.
>
> Syntax
> Environment settings take the format of
>
> name = value
>
> (The spaces around the = are optional.)
>
> Each cron command has 5 time and date fields, followed by a user
> name, and if
> this is the system crontab file, it will be followed by a
> command. Commands
> are
> executed when the time specified by the time/date fields matches the
> current time.
>
> field allowed values
> ----- --------------
> minute 0-59
> hour 0-23
> day of month 0-31
> month 0-12 (or names, see below)
> day of week 0-7 (0 or 7 is Sun, or use names)
>
> A field may be an asterisk (*), which always stands for ``first to
> last''. So used in the hour field, it means 'every hour from 00:00 to
> 23:00"
>
> Example Crontab:
>
> # r----minute
> # | r-----hour
> # | | r------day of the month
> # | | | r------month
> # | | | | r------day of the week
> # | | | | | |------ command to run ------------->
> # | | | | | |
> 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
> # run five minutes after midnight, every day
> 15 14 1 * * $HOME/bin/monthly
>
> # run at 2:15pm on the first of every month -- output mailed to paul
> 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are
> your kids?%
>
> # print out the message at 4:05 every sunday.
> 5 4 * * sun echo "run at 5 after 4 every sunday"
>
> If this file were saved as "paul.ct" then
> crontab -u paul paul.ct
> would be used to store the crontab for the user paul.
Ok, I didn't pick up on the fact that it uses the regular Linux cron. I
thought it was a totally separate IC feature. Thank you for the info.
- Grant
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