UNIX for Dummies Questions & Answers

Actually you guys both answered my question to an extent.

What originally confused me was this statement:

The Register of Open Branded Products seems to confirm that indeed Solaris, HP-UX, and AIX are among the Unix® branded products. That was what confused me. I had always thought that they were paying members...in fact I believe they're (IBM, Sun, HP) executive members of the Open Group (among others).

The other thing is that don't products such as Solaris, AIX, and HP-UX belong to a second main branch of Unix that is based on the commercial ATT released code, while BSD is based on the BSD's release(s)? While the ATT code was found to be mainly based on BSD in a court of law, it still is a major branch, no? As such no BSD could ever even become Unix® under the current standards... even if they were going to pay. Or am I wrong?

> The other thing is that don't products such
> as Solaris, AIX, and HP-UX belong to a
> second main branch of Unix that is based on
> the commercial ATT released code, while
> BSD is based on the BSD's release(s)?

Well, Solaris, AIX and HP-UX, as well as IRIX and a bunch of less relevant systems (such as Reliant) are based on AT&T Unix System V. Most of them licensed the code before SVR4 (Release 4), but when SVR4 was out, they all incorporated code from it into their systems as well. SVR4 is also what they're all licensing from SCO.

The free BSD systems today are based on 4.4BSD-Lite, which was the last release by Berkeley (in 1994). This release does not contain any AT&T files anymore.

> As such no BSD could ever even become
> Unix® under the current standards... even if
> they were going to pay.

No. While it is true that most UNIX-branded systems are System V derivatives, the code heritage has absolutely no relevance to the certification. The ONLY thing that matters is that you pass the tests which verify that your system supports ALL the interfaces and utilities defined by one of the SUS standards (the one you want to conform to) correctly. One of the systems I can think of that is not derived from System V is Tru64 UNIX (or before that, Digital UNIX), which is built on Mach (an early monolithic version of it I think) and BSD. Another is MVS or OS/390.

The current standard is UNIX03 or SUSv3, which was originally released in 2001 and amended in 2003. There's not a single system already conforming to it, however, so SUSv2 (or UNIX98) has more relevance for now: http://www.opengroup.org/onlinepubs/007908799/

I think much of the confusion over this issue only surfaced when SCO initiated litigation against everyone in the western hemisphere last year. I do agree wholly with Driver's excellent technical definitions of what, to all intents and purposes comprise a (noun) unix.

Whether a (noun) unix has registered status doesn't matter to many people, but as elsewhere stated that does have bearing when you're interested in meeting a minimum level of standards compliance. In terms of headache tablets, is it still (noun) aspirin if it has only 5% of the active chemical that Aspirin® does? There is, to my mind an issue of quality control that such things as trademarks represent. But this remains a technical definition, and one that I think most people could agree on. To most people it's just a bottle of aspirin tablets.

In practical terms, if it looks like a unix and acts like a unix, it's a unix. By which, I count Solaris, Tru64, Linux and FreeBSD as unix flavours whether commercial or free. Cygwin on Windows or BeOS (which has an extensive unix-like shell environment) are not. Neither is VMS, which implements a POSIX interface. Apple.. this is a grey area, but perhaps they are close enough.

I've read somewhere that I've forgotten utterly now, that "to an administrator all the unix systems are completely different, to a programmer they're all a bit different but to a user they're all pretty much the same." In discussion of what consitutes a unix-like system I'd conclude that they're all pretty much the same - even an administrator will expect certain commonalities between any of them.

I think that we've tackled this question as best we can. I think its best to close the thread now.