Linux is not UNIX period. UNIX is proprietary OS(most of them) which derive from either from Berkeley strain or AT&T or System V. Linux is otherwise is freshly written OS kernel by Torvalds and communities and licenses as Open Source. However Linux and UNIX do has similar look and feel due to POSIX compliant.

Most of C program written in UNIX can't be easily ported directly into Linux without re-compilation and vise versa. Today, it is UNIX that tries to mimic Linux, for example OpenSolaris project... only my 2 cents

This post has been edited by teknokrasi: Aug 17 2010, 11:15 AM