I saw this come up in
this thread, but I thought I should start a separate thread for this question. Please let me know if I should have kept this in the original thread.

I was wondering what the difference is in using at or sleep. The case I'm thinking of comes from the thread linked above:

case 1:
somewhere in /etc/rc.d/rc.local
at -f /path/to/script now + 5 min

case 2:
somewhere in /etc/rc.d/rc.local
/path/to/your/script &
at the top of /path/to/your/script
sleep 300


Specifically, I was wondering in terms of process context switch - which I know little about. I assume there is an efficient context switch in case 1 such that /path/to/script won't be eating up cpu cycles the first 5 mintues of its calling. Is the behavior the same for case 2? I assume the sleep command does not eat up cpu cycles according to this thread, but I wasn't sure.

I would also appreciate any other difference that you see between the two cases. Thanks.

will wait 300 sec before it executes, rc.local script will also wait for 300 sec, untill the script is executed; before it can continue

The script will be executed in 5 minutes, rc.local will continue to execute

Note also that at will run in a separate thread (from the script), and it will have its own environment. See the at(1) manpages for more info.

Hi All,

Sorry to interrupt in between, but what would be the better idea of scheduling a job...'at' or 'sleep' , especially when the cpu resources are the major concern for the execution of the job?

Regards,
Kapil

Depends what you want to do
How about cron ?

Hi Repo,

Thank you for the reply....
I have a script that needs to be run in 1 hr of interval for three times in the night time. Script adds 100 records to Oracle table after every 1 hr. I was thinking to set 'at' like that it executes after every 1 hr on its own, but I lost it to stop and it keeps on executing after every 1 hr throughout the night untill unless we manually stops that.

can 'wait' solve out problem ??

Cheers,
Kapil.

You can setup a cronjob for this
Take a look at
http://unixgeeks.org/security/newbie/unix/cron-1.html

Use cron for that: http://www.adminschoice.com/docs/cro...Crontab%20file

Hi All,

I think CRON will be a better idea for my work...I will go through the links again in detail and will edit the script accordingly.

Thank You All,
Kapil.

I'm not clear on what repo posted:

Wouldn't the & allow the rest of rc.local to get executed without waiting for /path/to/your/script to finish executing?

Also, how does the sleep command work exactly. This thread seems to explain that the sleep command doesn't eat up cpu cycles, but that a context switch occurs with the process, and the operating system will awaken the process after 300 seconds. So during the 300 seconds, no cpu cycle is used for /path/to/your/script. Is my understanding of this correct?


case 2: note: you have TWO files here

somewhere in /etc/rc.d/rc.local
/path/to/your/script &

at the top of /path/to/your/script
sleep 300