Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!umd5!trantor.umd.edu!chris
From: chris@trantor.umd.edu (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: Re: Shared Memory in BSD4.3 is lacking?
Message-ID: <2329@umd5.umd.edu>
Date: 20 Feb 88 14:36:50 GMT
References: <9100@ism780c.UUCP>
Sender: ris@umd5.umd.edu
Reply-To: chris@trantor.umd.edu (Chris Torek)
Organization: University of Maryland, College Park
Lines: 29

(Answer: Yes.)

In article <9100@ism780c.UUCP> mikep@ism780c.UUCP (Michael A. Petonic) writes:
>Now, don't get me wrong.  I like Berzerkeley and all, but JEEZ!  No
>shared memory?
[stuff about mmap deleted]
>What gives?

Nobody was quite sure how mmap `ought' to work, and it never got
implemented.  It is likely to be in `4.4', which is not what the
next release is going to be.  (Thoroughly confused yet?)

Anyway, BSD does not have System V style shared memory (which might
more accurately be called `USG 3.0 style shared memory') because
System V shared memory is wrong.  (Now there is a good flammable
statement for you :-) )

>What I'd really like to do is to share a file pointer (that's
>right, a file pointer, not a file descriptor) accross processes
>along with several variables.

What kind of `file pointer'?  Kernel file pointers (indexed by user
file descriptors) are in fact shared.  stdio `FILE *'s are not.
Basically, under 4.3BSD, you are stuck with a system call per remote
variable access (read: slow).  You could write a special device
driver that cheats, and acts like System V shared memory....
-- 
In-Real-Life: Chris Torek, Univ of MD Computer Science, +1 301 454 7163
(hiding out on trantor.umd.edu until mimsy is reassembled in its new home)
Domain: chris@mimsy.umd.edu		Path: not easily reachable