Re: Re: Re: Infinte perl script

It can. Remember you're checking if that 1 is still 1 on every loop. How long does a file usually stick around before being deleted?

Update: And of course the file test itself. Depending on how your disk caching is happening your results may vary.

My first big project had files being written across Samba mounts and then -e tests as well. CPU time wasn't much of factor, but the network could get clogged.
Getting the various perl programs talking directly to each other was much faster. So my experience might have nothing to do with your stuff

Comment on Re: Re: Re: Infinte perl script

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Re: Re: Re: Re: Infinte perl script by r.joseph (Hermit) on Jan 05, 2001 at 09:25 UTC
The file is there all the time - when it is deleted, it is a trigger for action. It is deleted by a user to trigger that action. Is there a better way to idle than while(1)? It only uses about .05% cpu right now, so its not that bad...	[reply]
sleep instead of burning cycles by Albannach (Monsignor) on Jan 05, 2001 at 10:15 UTC
The point is that `while(1){}` isn't idle, it's spinning madly behind the scenes, testing 1 as often as possible. In your case you probably have lots of other processes that push your script down to .05%, but I'm just guessing on that. On this old workstation the `while(1){}` goes up above 90% when not much is happening. Now I'm certainly no expert on process scheduling, but then neither is Win32 ;-). I've been taught (though it may be deprecated like lots of other things I've learned) that it's just bad manners for a program to basically waste time spinning madly, as you don't know what other apps might want to do with those cycles. If you `sleep()` you're letting the system decide what to do with those cycles you'd otherwise be wasting. Of course as others have already said, it depends on just how urgent your task is - do you need to act the same millisecond the file is deleted, or is 1/10 of a second fast enough (and don't forget your network latency is probably killing way more response time than the `sleep()` will). Maybe if you explain your application a bit more fully the answer will become clearer. -- I'd like to be able to assign to an luser	[reply] [d/l] [select]
(Guildenstern) Rex4: Infinte perl script by Guildenstern (Deacon) on Jan 06, 2001 at 02:21 UTC
If you're using Win32, there's always Win32::ChangeNotify. This will let you wait until your specified file is changed, then take action. I use it in a script on my NT box, and it doesn't take much CPU (especially compared to while(1)!). Guildenstern Negaterd character class uber alles!	[reply]