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  • Peter Malmgren thinks this is interesting:

The Open Group released the Single UNIX Specification (SUS). SUS rapidly grew in popularity, in large part due to its cost (free) versus the high cost of the POSIX standard. Today, SUS incorporates the latest POSIX standard.

From

Cover of Linux System Programming, 2nd Edition

Note

Somehow Mac OS X is a “UNIX” even though it has bizarre features such as case-insensitivity in it’s file system