that old GNU/Linux argument

[Alan Cox]

> Yes, there was some version of the Posix standard in that time frame. 
> It was just incomplete and described some mythical system that matched 
> no existing BSD or SysV flavor, so it was mostly ignored.  Sort of like 

Not really the case.

POSIX described a set of behaviours that were Unixlike and could be
relied upon. What it covered was far less than Unix and it took great
care to indicate what was not to be relied upon and in time SuS and
similar specs expanded on this by introducing new functions where
commonality was needed  and the existing interfaces were deficient -
obvious examples include termios and sigaction.

POSIX was and is very important but the basic core of posix isn't about
'being Unix' it is about fundamental things like
write/lseek/open/mkdir ...