Difference in Single Unix Specification, POSIX and X/Open

Correct me if I'm wrong, but I think you have to pay big $ for POSIX specification (~1K per lisence, so I've read [Will check again and update you])
On other hand single Unix specification is free.

Don't know about X/Open
 
After 1997, the Austin Group developed the POSIX revisions. The specifications are known under the name Single UNIX Specification, before they become a POSIX standard when formally approved by the ISO.
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Wikipedia: POSIX

The last version of the XPG, the X/Open Portability Guide Issue 4 (also known as the Common Applications Environment Specification Issue 4 (CAE4)), was published in July 1992 by The Open Group. The Single UNIX Specification was based on the XPG4 standard.
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Wikipedia: X/Open
 
I'll try to translate (very loosely) from Russian to English, so bear with me. My native language is Latvian :D

POSIX is for portability, it's based on UNIX, but is not limited to it.... (Windows claims to be POSIX compatible), The problem is that it defines various services, but doesn't specify how to implement them, which results in hard to write portable code, because of various implementations

Single UNIX Specification is based on POSIX.1, and fills it's holes. The full equipment of system interfaces is called X/Open System Interface (XSI)

only XSI compatible realisations can be called UNIX systems


Can't find info about pricing ... :(
 
killasmurf86 said:
(Windows claims to be POSIX compatible)
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Errr.. It's actually POSIX certified, certain versions of Windows are at least. Something FreeBSD isn't, FreeBSD is (partly) POSIX compliant.
 
Why isn't it POSIX compliant?

I know that FreeBSD passes my standards of POPTART compliance and Single Coffee Specification.
 
sossego said:
Why isn't it POSIX compliant?
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As far as I know, the cost of certifying POSIX compliance is the biggest obstacle.

I no longer care. Instead of asking whether something is POSIX compliant, I ask if it's BSD compatible. :e
 
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