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[OM] Re: OT: a few Mac questions

Subject: [OM] Re: OT: a few Mac questions
From: Jan Steinman <Jan@xxxxxxxxxxxxxx>
Date: Tue, 3 Apr 2007 19:12:03 -0700

> From: Dan Mitchell <danmitchell@xxxxxxxx>
>
>> You don't have to do "kill -9". Do "force quit" from the Finder, and
>> if that doesn't work the first time, do it again. The first one does
>> a "kill -HUP" and the second one does a "kill -KILL" and will then
>> update itself.
>
>  That's why I'm asking -- if "force quit" worked, I wouldn't have to  
> be
> using command prompts to get rid of processes.

I don't think you understood me.

"Force quite" works just fine. You NEVER want to use -9 as your first  
attempt to kill something! That may well be causing all sorts of other  
problems! "kill -9" is an unconditional process termination, without  
closing open files and network connections. If you "-9" a video  
player, most likely the video file still has an open file descriptor  
in the buffer pool, and may have problems when you try to re-open it,  
or as a minimum will hold system resources that should be freed. Do it  
enough times, and things will slow to a crawl until you re-start.

Since you seem determined to use Terminal without knowing these basic  
things about UNIX, I'd suggest you check out "man kill" to see what  
the various parameters do.

The GUI-based "force quit" first attempts a "kill -1" also known as  
SIGHUP. (Or maybe it's SIGTERM -- I forget.) This interrupts a running  
process and causes it to jump to its SIGHUP signal handler, which all  
processes are suppose to have. There, it is supposed to release  
allocated memory, close file descriptors and perform an orderly  
shutdown.

If that doesn't work, the second invocation of "force quit" does a  
SIGKILL, which DOES NOT signal the running process in any way -- it  
merely deletes it from the running process table. The process may then  
show up in ps as a "zombie" process -- one that is still holding  
system resources, but is effectively out of system control.

If you have a misbehaving program that consistently requires a SIGKILL  
to get rid of it, you should re-boot often. This is all just basic  
UNIX 101. Linux behaves the same way. It is not a Mac issue, really.


:::: Jan (running Leopard Beta, and don't have my signatures moved  
over yet) ::::




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