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What is UNIX, Anyway?
Lieutenant writes "Technology professionals have loosely used the term "UNIX" since the first person had to explain the difference between the Berkeley and AT&T flavors, so it's not surprising to find as many UNIX standards as there are versions of the operating system. Peter Seebach wades through the wellspring of UNIX standards and sorts them out for you, concluding that the rumors of the death of UNIX are (as usual) greatly exaggerated."
i don't take any reports of UNIX's death as fact without a Netcraft confirmation.
For the history of Unix (timeline), read this one:
http://www.levenez.com/unix/
Only Women Bleed (Sex, Sharia remix)
"There were only two things to come out of Berkeley in the 60's, LSD and Unix. I doubt that is a coincidence."
"Academicians are more likely to share each other's toothbrush than each other's nomenclature."
Cohen
Probably the oldest standard that people still refer to is AT&T's 1985 System V Interface Definition (SVID).
I routinely use printed Seventh Edition (Bell Labs Research) UNIX manuals, even when writing C for Linux. It also helps one remain blissfully ignorant of the 'cat -v' option and similar excrescences. Also the Tenth Edition UNIX manuals. I have to remember the changes introduced by Standard C and the like, but it's convenient to have the essence of the modern-day manual in printed form. Of course, there are some people out there who delight in using Fifth, Sixth, Seventh etc Editions on PDP-11s etc - see the PDP-11 UNIX Preservation Society, http://minnie.tuhs.org/PUPS/. I wish I had a larger garage! How much would a PDP-11/40 cost me now, anyway?
Peter Salus' book "A Quarter Century of UNIX", Addison-Wesley, 1994 (corrected 1995), ISBN 0-201-547771-5 is a good informal UNIX history.
"Those who do not understand UNIX are condemned to reinvent it -- badly."
-- Henry Spencer
(It's actually a giant space clam that wants you to give all your money to L Ron Hubbard)
Do you even lift?
These aren't the 'roids you're looking for.
I code for this API and the sources end up being source compatible.
Oh boy, you haven't deployed any code in the real world, have you?
The total number of conformant implementations of SuSv3 (or even v2) is zero. None. Zip. Zilch. Nada.
Everything, including the linux/glibc, BSD, and proprietary unix-like platforms, differs from the spec in subtle and complicated ways. SuS and POSIX are paper standards, not things that you will encounter in software. They're fodder for managers and marketing; they have little or no engineering value. And the differences are important to the point where you have to modify the source of your program to support other platforms, once the program becomes sufficiently complicated. As a rule, a complex program with no platform-specific hacks is a complex program that has bugs on some platforms which have not been found/fixed yet.
This isn't likely to change in a useful manner. Most of the platforms approximate SuS/POSIX as closely as they can without breaking existing applications. Successive revisions of SuS/POSIX become more vague in order to encompass more of the things that happen in the real world. So a good way to look at these two is to consider them an inefficient and fairly inaccurate attempt at documenting the common features of a set of platforms. If this process was completed perfectly, the resulting document would be so vague and cover so many platform-specific hacks that it would be of limited value. Since the documents get updated much more slowly than the software, they will probably never be completed to a satisfactory level of accuracy.
Unix is not GNU.
Ah. I see you've been forced to use AIX as well!
Well, that's certainly a negative way to put it, but what if anything could they do any better? It's not like it would be particularly practical or reasonable for unix vendors at this stage of unix history to break backwards compatibility for the sake of future compatibility.
So, the unix vendors do the next best thing: they make whatever changes they can to bring their platforms to uniformity without breaking backwards compatibility, and they maintain a common standards document that documents the cross-platform compatible functionality. When they inevitably make mistakes in the documentation process, they remove specifications that they cannot implement complatibly in all unix systems.
The most important point here is the intent of the unix vendors: They are working towards compatibility wherever they can, and they are striving for accurate documentation of the compatible functionality. There's nothing to disparage in their actions, even if they make the occasional mistake -- at least they are improving all the time.
Even linux developers are known to deviate from the SUS occasionally, but they too do strive to implement the standard wherever possible. Yes, the Single Unix Specification is incomplete and flawed, but it's the best thing we've got.
Clearly you were never forced to program anything to the Win32 API.
There's a common subset of functions available on both 9x and NT flavors of Windows. (With different bugs and sometimes different supported flags, different restrictions on use, etc). Then there's a bunch of functions that only work on NT-based flavors of Windows, not 9x-based. And the opposite is also true. Then XP came along, then Server 2003, each adding a bunch of new stuff to the API that Microsoft (unfortunately) did not go back and also add to the earlier versions of Windows.
There really are at least 3 distinct flavors of the Win32 API, and you have to be careful what functions you use if you want your program to run on all three of them.
For an example, check out the documentation for the CreateWindowEx function.
If you scroll to the bottom, they describe several of the differences in the behaviour of this function on different versions of Windows ranging from 95 to XP.
This situation could have been avoided if Microsoft had had the foresight to separate the Win32 API implementation from the rest of the OS so it could be upgraded independently.