Path: utzoo!attcan!uunet!virtech!cpcahil
From: cpcahil@virtech.UUCP (Conor P. Cahill)
Newsgroups: comp.unix.wizards
Subject: Re: How do I know my Q-KEY is unique ?
Keywords: msg queue, queue, message queue, ID
Message-ID: <1196@virtech.UUCP>
Date: 23 Sep 89 20:57:11 GMT
References: <1747@draken.nada.kth.se>
Organization: Virtual Technologies Inc
Lines: 26

In article <1747@draken.nada.kth.se>, d88-jwa@nada.kth.se (Jon W{tte) writes:
> I am currently considering using message queues for a game I'm writing.
> The problem is: when I create a message queue, I pass a (hopefully)
> unique 32-bit key. How do I make SURE this key is unique ? (I need to
> compile the key into a server as well as a client...)

There is no way to "register" or reserve an IPC key value.  Most software
that I have seen using ipc's has used one of the following:

	1. have the initial process obtain a "private" IPC and write the 
	   IPC id into a file that is read by all other programs using the
	   IPC.  Note that this is better than selecting an unused key
	   because you don't  have to hunt around.

	2. Use a control file that has the specified key.

	3. #2 but allow for an override by an environment variable.

	4. hard code in a specific key and hope you don't collide.  This is
	   the worst solution.

-- 
+-----------------------------------------------------------------------+
| Conor P. Cahill     uunet!virtech!cpcahil      	703-430-9247	!
| Virtual Technologies Inc.,    P. O. Box 876,   Sterling, VA 22170     |
+-----------------------------------------------------------------------+