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Re: [PATCH] System V Shared memory interface

From: Neal H Walfield
Subject: Re: [PATCH] System V Shared memory interface
Date: Sat, 2 Jun 2001 16:19:22 -0500
User-agent: Mutt/1.2.5i

> You seem to think I ever read a spec.  Can you point me to one?

For starters, there is the single unix specification.  As for
interpretations of SVIPC, look in Stevens' ``Advanced Programming in the
UNIX Environment'', Gay's ``Advanced UNIX Programming'' and `info ipc'

> I have not read anything that clearly defines shm identifiers.  Can you
> cite why you think these identifiers are considered global things that you
> can communicate to other processes?

>From chapter 22 of Gay:

Accessing by IPC ID

        When the IPC ID for a resource is known, the resource can be
        accessed directly.  Unlike files, which must be opened, IPC
        resources can be accessed immediately when the IPC ID is known.
        The one exception to this rule is that shared memory must be
        attached to your process memory space before it can be
        referenced (see shmat(2)).

> (I mean, then, what's the "key" for?)

The key is one way of communciating to other processes how to find the

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