Single UNIX Specification: Difference between revisions

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The '''Single UNIX Specification''' is the collective name of a family of standards developed and maintained by the [[Austin Group]]. It is based on earlier work by the [[IEEE]] and [[The Open Group]] and currently published as the Single UNIX Specification Version 3, and also as '''The Open Group Base Specifications''', '''IEEE Standard 1003.1 (POSIX)''' and '''ISO/IEC 9945'''. The standards emerged from a project, begun circa [[1985]], to standardise the [[API|application program interface]] for software designed to run on variants of the [[UNIX]] [[OS|operating system]].

Previously, The Open Group's Single UNIXUnix Specification was separate from the official IEEE POSIX. The near-equivalent Single UNIX Specification became more popular 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.

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|C programming language|C]] header files which must be provided by compliant systems.

* '''Shell and Utilities''' - A list of utilities and a description of the shell, [[sh|Bourne shell|sh]].

* '''System Interfaces''' - A list of available C system calls which must be provided.

* '''Rationale''' - The explanation behind the standard.