POSIX and Unix questions
 

Hi,

As ye all know, GNU is recursive acronym for "GNU's not Unix!", meaning, apart from being free, that it doesn't contain Unix code. So,

1) what is Unix code then, considering Unix is not an operating system itself, but more a family of operating systems. And then, do current POSIX-certified systems, such as QNX, OSX, AIX, HP-UX, Solaris etc., use the same code base? As far as I know, GNU/Linux and BSD are not certified only because distributors have to pay a lot of money for it;

2) and also, how far Linux and BSDs from being 100% POSIX compliants?

3) and why then the standards exist, if there is no interoperability, say, between OSX and Solaris, meaning, they have different ABIs and binary format in particular?

Thanks :study:

You might find this interesting http://bhami.com/rosetta.html, but this is pretty comprehensive for the history of Unix https://en.wikipedia.org/wiki/Unix#History

In short 'Unix' was developed at AT&T / Bell Research labs and therefore owned by them.
Eventually there was a version built by UCB known as BSD (sic). This is because AT&T weren't supposed to commercially sell SW, so they gave it away to Uni's, inc source.
To be officially called 'Unix', it has to be certified against certain stds (see the Wiki article).

Effectively Unix (Solaris, AIX, Ultrix, HP-UX etc)/Linux/*BSD/OSX etc (aka *nix) tend to be work-a-likes at the basic level.
They tend to differ significantly at the SysAdmin level.

BTW that wiki article also goes into 'free' *nix histories eg Linux.

HTH

Thanks, Chris.

I remember that table, I saw it maybe a couple of years ago last time. Pretty comprehensive.

There is one question about code base. Let's take, for example, what we call in GNU/Linux, coreutils. Are, say, cd or ls programmes the same, meaning the source code, across all of these Unixes? To be more precise: assuming their kernels are different (or not? As far as know, QNX is a RTOS and OSX kernel is open source), are their userlands the same? I mean, it was once written and then went across all of them.

I doubt if the code was the same in the early days, although the algorithms would be sometimes. The essential thing for POSIXes like BSD and Irix was to avoid being sued for copyright violation by AT&T. Later on, however, things changed with the concept of open source. If you wanted to create a new OS today, you could help yourself to all of the GNU tools, so long as you obeyed their license.

Indeed the src code for Linux must NOT be the same as a commercial Unix for legal reasons.
For a great example, see the IBM vs Sco debacle ...
In short IBM has essentially 'won' against Sco, which is good for Linux. :)

Seems like, 'tis a long story, just by looking at the length of the Wikipedia article.
I like the quote from Linus:
I even have this pic, that even sometimes appeared as a wallpaper, but I didn't really know, why SCO appeared there, apart from hearing about "some legal cases".

Anyway, now everything is clear, except for: how far is GNU/Linux from reaching POSIX standards? I heard, NetBSD is almost 100% POSIX 1 compliant.

[... 5 minutes of searching the internet ...]

Some say, 'tis about money and Linux is an almost 100% compliant.

Thanks everyone.

The real question there is who would care. If you look at the annual survey of web hosts, Linux dominates and other POSIX systems have less usage than Windows. Similarly, how many supercomputers, mainframes, smart phones, communications satellites, big company servers use BSD or Solaris? Linux is the new Unix, as was recognised when Solaris was given extra libraries to make it Linux-compatible!