Surely "unix" spelt in cpp simply means the 7th edition feature set ?
That certainly covers the list you write below, and seems to me
to be as portable a definition as anything gets :-)

In article <199806221855.OAA28569@Twig.Rodents.Montreal.QC.CA> you write:
> > [L]ook at the set of systems which have been declared to have -Dunix!
> > How many common programming features do they actually share?
> 
> Lots, as compared to, say, VMS, MS-DOS, VM/CMS, an embedded controller,
> etc.
> 
> A few right off the top of my head:
> 
> - pipe()
> - fork()
> - a shell in /bin/sh
> - a filesystem that's about as close to syntax-free as it gets
> - a nonexistent text/binary distinction in stdio
> 
> We're so thoroughly indoctrinated in the UNIX way nowadays that it's
> often hard to see other ways.  There's a sense in which I consider
> myself fortunate that much of my larval stage was spent using VMS...and
> unfortunate that it wasn't something even farther from the UNIX way.
> 
> 					der Mouse
> 
> 			       mouse@rodents.montreal.qc.ca
> 		     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B
> 


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