Some of the things he mention have nothing to do with Unix or Posix. __sync_*, for example, are gcc-specific. Similarly, F_GETLEASE, F_SETLEASE, and F_NOTIFY are Linux-specific fcntl() operations. And as far as I can tell, the -T option isn't included in the Posix spec for mv, either (http://www.opengroup.org/onlinepubs/000095399/toc.htm).

Because all the world is not Linux.

And even less of the world is POSIX.

This was post here about 4 months ago, http://news.ycombinator.com/item?id=1035100 , lots of good comments.

"UNIX-like/POSIX-compliant operating systems"

So what would that not be?

Windows. (And don't even mention Windows POSIX.)