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Old 01-25-2006, 08:56 AM   #1
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How does cron daemon work?

I am working on building a scheduler which runs tasks at specified times. In this regard, I felt it would be good to know how the cron daemon works. I Googled, but didnt really get much insight into what actually happens. Can I get some directions as to where I can get information on the same?
Old 01-25-2006, 10:20 AM   #2
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Ermmm, the cron deamon IS a scheduler which runs tasks at specific times. Why would you want to build a new one?
Old 01-25-2006, 12:06 PM   #3
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could you not check out the source of crond or at
Old 01-26-2006, 05:22 AM   #4
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Originally Posted by xhi
notice... the majority of this post is opinion and hear_say, which is based primarily on bias and prejudice.
Like your tagline
Old 01-26-2006, 05:48 AM   #5
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When cron is started or made to reread it's config, it examines all the config files, parses them and
stores this info in memory.
In a loop that runs every minute (==the finest time granule allowed), it checks if any jobs need to run
and if there are, it runs them (using a special environment setting and running as the user who submitted the job).

But, I agree with baldy that you should stick with cron/at if you can. There is no need to make your own.
If you do have a system without a scheduler/cron, you may consider building it from it source.
Old 01-26-2006, 08:40 AM   #6
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If I understand correctly, cron is one of many "daemons" that run in background to keep the system functioning. All of these have the common feature that they continuously check **something** to see if an action is required. An obvious example is the daemon that watches for keyboard input in a terminal.

cron simply watches the clock and checks against the instructions in crontab to see what needs to be run for any given time.


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