Some additions: Systems with /bin a symlink to /usr/bin Digital UNIX 4.0 Tru64 UNIX 5.0 to 5.1B HP-UX 11i 11.23 and 11.31 Systems with separate /bin and /usr/bin SCO UNIX 3.2 V4.0 to V4.2 -- The more I learn the better I understand I know nothing.