From: downing.nick+tuhs@gmail.com (Nick Downing)
Subject: [TUHS] Ideas for a Unix paper I'm writing
Date: Tue, 28 Jun 2011 10:32:58 +1000 [thread overview]
Message-ID: <BANLkTinJQfffbvMiq8JakmsLv1GqMUrLJQ@mail.gmail.com> (raw)
In-Reply-To: <20110628001140.GA23711@minnie.tuhs.org>
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I think you definitely need to say that the idea of file descriptors
in the unix API anticipated the current style (fad?) of
object-oriented programming by about 20 years, languages like
Smalltalk/C++, more recently java/ruby, use opaque objects with
polymorphism to provide services, which is exactly what unix does, an
object hierarchy would look something like:
- read/write capable (file descriptor) objects
- seek capable (storage) objects
- truncate capable (file) objects
- non truncate capable (block) objects
- non seek capable (stream) objects
- pipes
- sockets
- stream oriented sockets
- datagram oriented sockets
- terminals
For terminals, the extension to the API over the basic read/write
capable object is via an ioctl, whereas for sockets it is via its own
API (connect/accept/listen/etc), but conceptually there is no reason
why read/write/lseek/etc couldn't be ioctls as well, since the mapping
from userspace calls (such as lseek or stty/gtty) to syscalls is up to
the standard library. pipe() is a java-style constructor, whereas
socket() or open() is conceptually a static factory as it can return
different types of objects depending on the request, the constructors
for the corresponding objects are conceptually private constructors.
An errno is basically a checked exception that can be thrown, each
syscall effectively has a java style "throws ..." clause and well
designed userland code catches or rethrows these.
cheers, Nick
On Tue, Jun 28, 2011 at 10:11 AM, Warren Toomey <wkt at tuhs.org> wrote:
> All, IEEE Spectrum have asked me to write a paper on Unix to celebrate the
> 40th anniversary of the release of 1st Edition in November 1971. I'm after
> ideas & suggestions!
>
> I think my general thrust is that Unix is an elegant design, and the
> design elements are still relevant today. The implementation is mostly
> irrelevant (consider how much the code has changed from assembly -> C,
> from the simple data structures in V7 through to current BSD), but the
> original API is classic. Note that about 28 of the 1st Ed syscalls are
> retained in current BSDs and Linux, and with the same syscall numbers.
>
> I'm having some trouble thinking of the right way to explain what is
> an elegant design at the OS/syscall level, so any inspirations/ideas
> would be most welcome. I might highlight a couple of syscall groups:
> open/close/read/write, and fork/exec/exit/wait.
>
> If you have any references/URLs you think I should look at, please
> pass them on to me.
>
> I'm also trying to chase down some quotes; my memory seems to be failing me
> but I'm sure I've seen these somewhere:
>
> - in a paper, I think by Thompson & Ritchie, where they assert that the
> kernel should provide no more than the most minimal services to the
> userland programs. I thought this was the CACM paper, but I can't spot
> this bit. Maybe it's in Thompson's preface to the Lions Commentary,
> of which my copy is elsewere at present.
>
> - I'm sure I remember someome (Kernighan?) say that Ritchie encouraged
> them to espouse the use of processes as context switching was cheap,
> but later measurements showed that in fact it wasn't that cheap in
> the early versions of Unix.
>
> Anyway, if you can think of good ideas/references about the elegance of
> Unix, especially from the design perspective, I would much appreciate them.
>
> Cheers,
> Warren
> _______________________________________________
> TUHS mailing list
> TUHS at minnie.tuhs.org
> https://minnie.tuhs.org/mailman/listinfo/tuhs
>
next prev parent reply other threads:[~2011-06-28 0:32 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-28 0:11 Warren Toomey
2011-06-28 0:26 ` Larry McVoy
2011-06-28 0:32 ` Nick Downing [this message]
2011-06-28 1:00 ` Tim Newsham
2011-06-28 3:36 ` Jim Capp
2011-07-02 4:03 ` Warner Losh
2011-08-07 20:26 ` Alan D. Salewski
2011-09-02 18:33 ` Jose R. Valverde
2011-06-28 3:53 ` Jim Capp
2011-06-28 4:13 ` Greg 'groggy' Lehey
2011-06-28 5:48 ` Nick Downing
2011-06-28 7:22 ` Tim Newsham
2011-06-28 14:18 ` Wesley Parish
2011-06-28 7:32 ` Wilko Bulte
2011-06-28 15:22 ` Al Kossow
2011-06-29 1:30 A. P. Garcia
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