The Single UNIX Specification reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Single UNIX Specification

The Single UNIX Specification (SUS) is the collective name of a family of standards for computer operating systems to qualify for the name "Unix". The SUS is developed and maintained by the Austin Group, based on earlier work by the IEEE and The Open Group.

Table of contents

1 History 2 Specification 3 Linux and the SUS 4 See also 5 External links

History

The SUS emerged from a project, begun circa 1985, to standardise the application program interface for software designed to run on variants of the UNIX operating system. This became IEEE 1003, or POSIX — a name given to it by Richard Stallman, in request for a memorable name for the standard — which loosely stood for Portable Operating System Interface.

Previously, The Open Group's Single UNIX Specification was separate from the official IEEE POSIX. The near-equivalent SUS became more popular with the involvement of several major vendors in the wake of the UNIX wars because it was available for free, whereas the IEEE charged a substantial fee for access to the POSIX specification. Beginning in 1998 a joint working group, the Austin Group, began to develop the combined standard that would be known as the Single UNIX Specification Version 3.

Specification

The user and software interfaces to the OS are specified in four main sections:

• Base Definitions — A list of definitions and conventions used in the specifications and a list of C header files which must be provided by compliant systems.
• Shell and Utilities — A list of utilities and a description of the shell, sh.
• System Interfaces — A list of available C system calls which must be provided.
• Rationale — The explanation behind the standard.

The standard user command line and scripting interface is the Korn shell. Other user-level programs, services and utilities include awk, echo, ed, and numerous (hundreds) others. Required program-level services include basic I/O (file, computer terminal, and network) services.

A test suite accompanies the standard. It is called PCTS or the Posix Certification Test Suite.

Note that a system need not include source code derived in any way from AT&T Unix to meet the specification. For instance, IBM OS/390, now Z/OS, qualifies as a "Unix" despite no code in common.

Linux and the SUS

Most Linux vendors do not go to the expense of certifying a given version of their distribution as meeting the SUS. Furthermore, the content of a typical Linux distribution changes so fast that recertification would be required far more often than would be financially viable.

For Linux systems, several common extensions and complementary de facto standards are provided by the Linux Standard Base.

See also

• UNIX wars
• Native POSIX Thread Library

External links

• Text of the Single UNIX Specification, Version 3
• The Portable Application Standards Committee
• Unix-Wars (Living Internet)
• Unix Standards (Eric S. Raymond, The Art of Unix Programming)

This is the "Single UNIX Specification" reference article from the English Wikipedia. All text is available under the terms of the GNU Free Documentation License. See also our Disclaimer.