Unices

Introduction to UNIX and its siblings

UNIX

Originally developed at AT&T Bell Labs circa 1970. Has experienced a long, multi-branched evolutionary path

POSIX (Portable Operating System Interface)

a set of specifications of what an OS needs to qualify as “a Unix”, to enhance interoperability among all the “Unix” variants

Various Unices

The unix family tree

• OS X

  is a Unix!

• Linux

  is not fully POSIX-compliant, but certainly can be regarded as functionally Unix

Some Unix hallmarks

• Supports multi-users, multi-processes
• Highly modular: many small tools that do one thing well, and can be combined
• Culture of text files and streams
• Primary OS on HPC (High Performance Computing Systems)
• Main OS on which Internet was built

Files/directories organization in *NIX

Permissions

All files have permissions and ownership.

File permissions