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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c,comp.unix.questions
Subject: Re: System V manuals (was Re: What real non-UNIX 'C' compilers...)
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Date: Thu, 8-Oct-87 22:29:04 EDT
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Posted: Thu Oct  8 22:29:04 1987
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> Haven't seen the book you cite anywhere. All the bookstores around here
> have the SVID-based one only.

Well, that's too bad, but the book *you* cite appears to be the only book that
claims to be a System V manual (as opposed to a System V interface definition)
and that has this layout.  In other words, the book you cite is an exception to
the rule, and complaints about its contents cannot validly be extended to
complaints about System V documentation in general.

> I wish it was. Unfortunately the book I cite is the only one I've seen,
> and it's also the one Microport is distributing as their UNIX manual.

It's not the one AT&T is distributing as *its* UNIX manual, nor is it, I
suspect, what most vendors distribute.

> I didn't say it was in section 2 or section 3. I said it was in BA_SYS...

I quote here from your original article:

> Except that the O/S *manuals* follow the SVID. And except that it confuses
> people. "Hey, peter, how come they have read and fread?" "Well, fread is
> a library routine." "Oh. How do you tell which ones are library routines?"
> "read the manual. Library routines are section 3" "section 3? I don't
> have a section 3" "What? Let me look at that... they must be kidding".

I see nothing about BA_SYS here.  I see only a claim that "the O/S manuals
follow the SVID", which is NOT true in general; it is only true for that one
anomalous manual you saw.  All the System V manuals we've gotten from AT&T have
the traditional division between sections 2 and 3.

> > Remember, we're NOT just talking about "traditional UNIX systems" here.
> > This "read" could be implemented atop a non-UNIX system, or a UNIX system
> > with more general facilities for sharing than "traditional" systems.
> 
> Since the title of the message is "System V manuals", don't you think we
> should be talking about System V?

Well, first of all, if we're talking about System V, we should talk about it in
comp.unix.questions, so this discussion is moving there.

Second of all, in the claim you made said nothing about implementing "read"
under a vanilla System V system.  You just said

> I don't believe you could implement "read" as a library routine and retain
> the attribute of leaving the file descriptor at the point last read, unless
> you were to "implement" it by making a direct call to the existing read
> routine. Certainly buffering would be out.

with no such qualification.  You could definitely do this under some
non-vanilla implementations, e.g. Apollo's DOMAIN/IX.

For that matter, you could probably do it under vanilla System V, if the IPC
code, including shared memory, is configured into the kernel.  You may not
*want* to do it that way, but it's not impossible.

The fact that it *doesn't* happen to be implemented that way in most UNIX
systems is irrelevant; you didn't say it *wasn't* done that way, you said that
you didn't believe it *could* be done that way.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com