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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.

Contents

History

Specification

Marks for compliant systems

Compliance

AIX

HP/UX

Mac OS X

SCO

Solaris

Tru64 UNIX

z/OS

Other compliant systems

Non-registered Unix-like systems

BSD

Linux

Further reading

See also

References

External links

History

The SUS emerged from a mid-1980s project to standardize operating system interfaces for software designed for variants of the Unix operating system. The need for standardization arose because enterprises using computers wanted to be able to develop programs that could be used on the computer systems of different manufacturers without reimplementing the programs. Unix was selected as the basis for a standard system interface partly because it was manufacturer-neutral. These standards became 'IEEE 1003' (also registered as 'ISO/IEC 9945'), or 'POSIX', which loosely stands for 'Portable Operating System Interface for Unix'.
In the early 1990s a separate effort, known as the Common API Specification or Spec 1170, had been initiated by several major vendors, who formed the COSE alliance in the wake of the Unix wars. This 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 known as 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 Bourne Shell. Other user-level programs, services and utilities include awk, echo, ed, and hundreds of others. Required program-level services include basic I/O (file, 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.

Marks for compliant systems

There are two official marks for conforming systems:

★ UNIX 98 - the mark for systems conforming to version 2 of the SUS

★ UNIX 03 - the mark for systems conforming to version 3 of the SUS
Older UNIX standards:

★ UNIX93

★ UNIX95

Compliance

AIX

AIX 5L V5.2 with some updates, and AIX 5L V5.3, are registered as UNIX 03 compliant. AIX 5L V5.2 is registered as UNIX 98 compliant.

HP/UX

HP-UX 11i V3 Release B.11.31 is registered as UNIX 03 compliant. Previous releases are registered as UNIX 95.

Mac OS X

Mac OS X v10.5 "Leopard", due to be released in October 2007, is an Open Brand UNIX 03 registered product.^[1][2]

SCO

UnixWare 7.1.3 is registered as UNIX 95 compliant.
SCO OpenServer 5 is registered as UNIX 93 compliant.

Solaris

Solaris 10 is registered as UNIX 03 compliant on 32-bit and 64-bit x86 and SPARC systems. Solaris 8 and 9 are registered as UNIX 98 compliant on the same platforms, except that they do not include support for 64-bit x86 systems.

Tru64 UNIX

Tru64 UNIX V5.1A and later are registered as UNIX 98 compliant.

z/OS

IBM z/OS prior to 1.9 is registered as UNIX 95 compliant.
IBM has announced that z/OS 1.9, scheduled for release in September 2007, will "better align" with UNIX 03 (partial or full compliance is unclear thus far).^[3]

Other compliant systems

Other operating systems registered as UNIX 95 or UNIX 93 compliant:

★ NCR UNIX SVR4

★ NEC UX/4800

Non-registered Unix-like systems

Vendors of Unix-like systems such as Linux and BSD do not typically certify their distributions, as the cost of certification and the rapidly changing nature of such distributions make the process too expensive to sustain.^[4]

BSD

No freely available BSD system has been registered as SUS compliant.
FreeBSD has a "C99 and POSIX Conformance Project" [1]
which aims for full compliance with a large subset of the SUS.
Darwin is an open source operating system based on FreeBSD:
it is essentially the open source subset of Mac OS X.
Darwin is compliant with the SUS 03 [2].

Linux

Linus Torvalds has stated that the Linux kernel is designed to be as POSIX-conforming as possible, although he coded Linux before he obtained a copy of the standards, basing its system call behaviors on man pages from existing Unix systems.
The Linux Standard Base was formed in 2001 as an attempt to standardize the internal structures of Linux-based system for increased compatibility. It is based on, and also extends in several areas, the POSIX specifications, Single UNIX Specification, and other open standards. It is de facto accepted and followed by many Linux distributions.

Further reading

★

See also

★ Unix wars

★ Native POSIX Thread Library for a Linux-specific implementation of the popular POSIX threads library

★ UNIX manual

★ Open system (computing)

★ open standard

References

1. Mac OS X Leopard - Technology - UNIX
2. Mac OS X Version 10.5 Leopard on Intel-based Macintosh computers certification The Open Group
3. Preview: IBM z/OS V1.9 advanced infrastructure solutions for your business needs
4. The Open Brand Fee Schedule Lists fees required to use UNIX brand

External links

★ The Single UNIX Specification

★ Text of the Single UNIX Specification, Version 3

★ The Portable Application Standards Committee

★ Register of products certified for the UNIX and other Open Group brands

★ Unix-Wars (Living Internet)

★ Unix Standards (Eric S. Raymond, ''The Art of Unix Programming'')