Yes, and the z/OS USS is what I call
aggressively POSIX-compliant. Its mission in life is to hurt you with strict adherence to the spec, not ever help you!
If there's any optional part of POSIX, it's not in there. You only get the 'MUST' parts of the base spec. No optional extensions, etc. When you're porting over C code to z/OS USS, you are often surprised when things you assumed were just part of every POSIX implementation aren't there. Fun times for all!
