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From: Rainer Weikusat <rweikusat@mssgmbh.com>
Newsgroups: comp.os.linux.development.apps
Subject: Re: mmap for IPC
Date: Thu, 02 May 2013 14:42:44 +0100
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Lusotec <nomail@nomail.not> writes:
> Jay Braun wrote:
>> Just want to make sure:  If I use mmap for inter-process communication,
>> the processes that share the memory need not be forked from some parent
>> process.  They can be invoked independently, correct?
>
> Yes, if the mapping is not anonymous. If the mapping is anonymous only the 
> process and its children can access the anonymous mapping (see MAP_ANONYMOUS 
> in man mmap).
>
> On a side note, you may want to use shm_open instead of mmap directly if you 
> want to use shared memory for IPC between unrelated processes.

Quoting shm_open(3):

	A POSIX shared memory object is in effect a handle which can
	be used by unrelated processes to mmap(2) the same region of
	shared memory.