View source for Single UNIX Specification

{{short description|Standards for computer operating systems that qualify for using the "UNIX" trademark}}
{{Redirect2|Unix V7|UNIX V7|the 1979 Research Unix release often called V7|Version 7 Unix}}
{{Use mdy dates|date=July 2022}}
The '''Single UNIX Specification''' ('''SUS''') is a standard for [[computer]] [[operating system]]s,<ref>{{cite web|url=https://unix.org/questions_answers.html|title=Questions & Answers|website=unix.org}}</ref><ref>{{cite web|url=https://www.opengroup.org/membership/forums/platform/unix|title=The UNIX Standard|website=[[The Open Group]]|date=August 27, 2018 }}</ref> compliance with which is required to qualify for using the "[[Unix|UNIX]]" trademark. The standard specifies programming interfaces for the C language, a command-line shell, and user commands. The core specifications of the SUS known as ''Base Specifications'' are developed and maintained by the [[Austin Group]], which is a joint working group of [[IEEE]], [[ISO/IEC JTC 1/SC 22]]/WG 15 and [[The Open Group]]. If an operating system is submitted to The Open Group for certification, and passes conformance tests, then it is deemed to be compliant with a UNIX standard such as UNIX&nbsp;98 or UNIX&nbsp;03.

Very few [[BSD]] and [[Linux]]-based operating systems are submitted for compliance with the Single UNIX Specification, although system developers generally aim for compliance with [[POSIX]] standards, which form the core of the Single UNIX Specification.

The latest SUS consists of two parts: the ''base specifications'' technically identical to POSIX, and X/Open Curses specification.<ref>{{cite web|url=https://publications.opengroup.org/standards/unix/t101|title=Single UNIX Specification, Version 4, 2018 Edition|website=[[The Open Group]]}}</ref>

Some parts of the SUS are optional.

==History==

===1980s: Motivation===
The SUS emerged from multiple 1980s efforts to standardize [[operating system]] [[interface (computer science)|interface]]s 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.

In 1984, the UNIX user group called /usr/group published the results of their standardization effort for programming interfaces in their 1984 /usr/group standard, which became basis for what would become the POSIX.1-1988 standard.<ref>{{cite web|url=https://kelty.org/or/papers/Kelty_WULP_Conceiving_2009.pdf|title=Conceiving Open Systems|first=Christopher M.|last=Kelty|website=kelty.org}}</ref><ref>{{cite book|url=https://docs.oracle.com/cd/E19641-01/802-1953/802-1953.pdf|title=Standards Conformance Guide|publisher=SunSoft|date=November 1995}}</ref>

In 1985, AT&T published [[System V Interface Definition]] (SVID), a specification of UNIX System V programming interfaces.<ref>{{cite book|url=https://books.google.com/books?id=QcG4wAEACAAJ|title=System V Interface Definition|date=1985|asin= B000KF6SCE}}</ref>

===1988: POSIX===
In 1988, standardization efforts resulted in '''IEEE 1003''' (also registered as '''[[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] 9945'''), or '''[[POSIX]].1-1988''', which loosely stands for '''Portable Operating System Interface'''.

===1980s and 1990s: X/Open Portability Guide===
The [[X/Open Portability Guide]] (XPG) was a precursor to the SUS, published by the [[X/Open Company]], a consortium of companies established in 1984. The guides were published in the following years. 
* XPG1: X/Open Portability Guide Issue 1: 1985<ref name=raymond2003>{{cite book|url=http://www.catb.org/~esr/writings/taoup/html/|title=The Art of UNIX Programming|first=Eric S.|last=Raymond|author-link=Eric S. Raymond|date=September 19, 2003|chapter=Standards and the Unix Wars|chapter-url=http://www.catb.org/~esr/writings/taoup/html/ch17s02.html#id2994594}}</ref>
* XPG2: X/Open Portability Guide Issue 2: 1987<ref name=raymond2003/>
* XPG3: X/Open Portability Guide Issue 3: 1989<ref>{{cite book | title=Unix Network Programming, Volume 1: The Sockets Networking API | publisher=Addison-Wesley Professional |first1=W. Richard |last1=Stevens |author-link1=W. Richard Stevens |first2=Bill |last2=Fenner |first3=Andrew M. |last3=Rudoff |date=2003 | isbn=978-0131411555 | oclc=53867239 | edition=3rd}}</ref>
* XPG4: X/Open Portability Guide Issue 4: 1992<ref name=raymond2003/>

XPG4 Base included the following documents:
* System Interface Definitions, Issue 4, {{ISBN|1-872630-46-4}}
* System Interfaces and Headers, Issue 4, {{ISBN|1-872630-47-2}}
* Commands and Utilities, Issue 4, {{ISBN|1-872630-48-0}}

===1990s: Spec 1170===
In the early 1990s, a separate effort known as the Common API Specification or Spec 1170 was initiated by several major vendors,<ref name=unixorgsus>{{cite web|url=https://unix.org/what_is_unix/single_unix_specification.html|title=The Single UNIX Specification|website=unix.org}}</ref> who formed the [[Common Open Software Environment|COSE]] alliance in the wake of the [[Unix wars]]. In 1993, Spec 1170 was assigned by COSE to [[X/Open]] for fasttrack.<ref name=unixorghist>{{cite web|url=https://unix.org/what_is_unix/history_timeline.html|title=The UNIX System -- History and Timeline -- UNIX History|website=unix.org}}</ref> In October 1993, a planned transfer of UNIX trademark from Novell to X/Open was announced;<ref>{{cite newsgroup|url=https://groups.google.com/g/comp.std.unix/c/Jblvq9RejzI/m/ypx8LcZjBmEJ|title=The name "UNIX" is now the property of X/Open|first=Quentin|last=Fennessy|date=October 12, 1993|newsgroup=comp.std.unix}}</ref> it was finalized in 2nd quarter of 1994.<ref>{{cite web|url=https://unix.org/questions_answers/faq.html|title=Frequently Asked Questions|website=unix.org}}</ref> Spec 1170 would eventually become the Single Unix Specification.<ref name=unixorgsus/>

===1994: Single UNIX Specification===
In 1994, the X/Open Company released the '''Single UNIX Specification'''.<ref name=unixorgsus/> The SUS was made up of documents that were part of the X/Open Common Applications Environment (CAE):<ref name=unixorgsus/>
* System Interface Definitions, Issue 4, Version 2<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/009656599/toc.pdf|title=X/Open CAE Specification System Interface Definitions, Issue 4, Version 2|date=1994|publisher=X/Open Company}}</ref>
* System Interfaces and Headers, Issue 4, Version 2<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/9695969499/toc.pdf|title=X/Open CAE Specification System Interfaces and Headers, Issue 4, Version 2|date=1994|publisher=X/Open Company}}</ref>
* Commands and Utilities, Issue 4, Version 2<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/009656399/toc.pdf|title=X/Open CAE Specification Commands and Utilities, Issue 4, Version 2|date=1994|publisher=X/Open Company}}</ref>
* Networking Services, Issue 4<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/009656199/toc.pdf|title=X/Open CAE Specification Networking Services, Issue 4|date= 1994 |publisher=X/Open Company}}</ref>

This was a repackaging of the [[X/Open Portability Guide]] (XPG), Issue 4, Version 2.

Sources differ on whether X/Open Curses, Issue 4, Version 2 was part of this SUS;<ref name=unixorgsus/><ref>{{Cite web|title=Single UNIX® Specification, Version 1 Document Set (UNIX 95)|url=https://publications.opengroup.org/c43x|access-date=May 25, 2021|website=opengroup.org}}</ref> its copyright date is given as 1996.<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/009638999/toc.pdf|title=X/Open Curses, Issue 4, Version 2|date=1996|publisher=X/Open Company |isbn=1-85912-171-3}}</ref> X/Open Curses, Issue 4 was published in 1995.<ref>{{cite book|url=https://books.google.com/books?id=PYFCAAAACAAJ|title=X/Open Curses, Issue 4|date=1995|publisher=X/Open Company |isbn=9781859120774 }}</ref>

In October 1994, X/Open indicated they were going to refer to Spec 1170 as '"Single-Unix" specification'.<ref>{{cite magazine|url=https://books.google.com/books?id=Ilp0BEVTY3gC&pg=PA49|title=X/Open test suites advance|first=Jean S.|last=Bozman|magazine=[[Computerworld]]|volume=28|issue=43|page=49|date=October 24, 1994}}</ref>

The SUS was at the core of the UNIX 95 brand.<ref>{{cite web|url=https://www.opengroup.org/openbrand/register/xum4.htm|title=Open Brand - UNIX 95|website=[[The Open Group]]}}</ref>

This version had 1168 programming interfaces.<ref name=v3howmanyapis/>

This version of SUS was drawn from the following sources:<ref name=unixorgsus/>
* XPG4 Base by X/Open
* [[System V Interface Definition]], (SVID) Edition 3, Level 1 calls by AT&T
* Application Environment Specification (AES) by the [[Open Software Foundation]] (OSF)
* Interfaces found in common use and not yet covered by a formal specification, drawn from a survey of major applications.

===1997: Single UNIX Specification, version 2===
In 1996, X/Open merged with [[Open Software Foundation]] (OSF) to form [[The Open Group]].<ref>{{cite journal|url=https://books.google.com/books?id=t_HcO8cY91IC&pg=PA17|title=Formation of 'The Open Group'|first=Phil|last=McCrea|pages=17–18|journal=AUGGN: The Journal of AUUG Inc.|volume=17|issue=2|date=April 1996}}</ref><ref>{{cite magazine|url=https://books.google.com/books?id=GTHir58nwGgC&pg=PT71|title=WebCrusader may blaze wider trail for DCE users|first=Sharon|last=Gaudin|magazine=[[Computerworld]]|volume=30|issue=22|page=64|date=May 27, 1996}}</ref>

In 1997, the Open Group released the '''Single UNIX Specification, Version 2'''.<ref>{{cite web|url=https://www.opengroup.org/onlinepubs/7990989775/|title=The Single UNIX Specification, Version 2|website=www.opengroup.org}}</ref><ref>{{cite press release
  |url = https://unix.org/version2/pr.html
  |title = The Open Group Announces Enhanced Single UNIX Specification
  |access-date = July 26, 2009
  |date = March 12, 1997
|publisher = The Open Group
}}</ref>

This specification consisted of:<ref>{{cite web|url=https://unix.org/version2/whatsnew/login_whatsnew.html|title=What's New in the Single UNIX Specification, Version 2|website=unix.org}}</ref>
* System Interface Definitions, Issue 5,<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/9693999499/toc.pdf|title=System Interface Definitions Issue 5|publisher=[[The Open Group]]}}</ref>
* System Interfaces and Headers, Issue 5,<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/009639399/toc.pdf|title= System Interfaces and Headers Issue 5|publisher=[[The Open Group]]}}</ref>
* Commands and Utilities, Issue 5,<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/009639599/toc.pdf|title=Commands and Utilities Issue 5|publisher=[[The Open Group]]}}</ref>
* Networking Services, Issue 5,<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/9647699/toc.pdf|title=Networking Services (XNS) Issue 5|publisher=[[The Open Group]]|date=May 14, 1997 |isbn=1-85912-165-9}}</ref>
* X/Open Curses, Issue 4, Version 2,<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/009638999/toc.pdf|title=X/Open Curses, Issue 4, Version 2|date=1996|publisher=[[The Open Group]]|isbn=1-85912-171-3}}</ref>
and was at the core of the UNIX 98 brand.<ref>{{cite web|url=https://www.opengroup.org/openbrand/register/xxm0.htm|title=Open Brand - UNIX 98|publisher=X/Open Company}}</ref>

This version had 1434 programming interfaces.<ref name=v3howmanyapis/>

===2001: Single UNIX Specification, version 3, POSIX.1-2001===
Beginning in 1998, a joint [[working group]] of IEEE, ISO JTC 1 SC22 and The Open Group known as the [[Austin Group]] began to develop the combined standard that would be known as the core of '''Single UNIX Specification, Version 3''' and as POSIX.1-2001. It was released on January 30, 2002.<ref>{{cite press release
  |url = https://unix.org/version3/pr.html
  |title = The Open Group announces completion of the joint revision to POSIX and the Single UNIX Specification
  |access-date = July 26, 2009
  |date = January 30, 2002
|publisher = The Open Group
}}</ref>

This SUS consisted of:<ref name=unixorgv3>{{cite web|url=https://unix.org/version3/overview.html|title=The Single UNIX Specification Version 3 - Overview|website=unix.org}}</ref>
* Base Specifications, Issue 6
** Base Definitions, Issue 6
** System Interfaces, Issue 6
** Shell and Utilities, Issue 6
** Rationale (Informative)
* X/Open Curses, Issue 4, Version 2
and is at the core of the UNIX 03 brand.<ref>{{cite web|url=https://www.opengroup.org/openbrand/register/xym0.htm|title=Open Brand - UNIX 03|website=[[The Open Group]]}}</ref>

The Base Specifications are technically identical to '''POSIX.1-2001''', which is IEEE Std 1003.1-2001.<ref name=unixorgv3/>

This version had 1742 programming interfaces.<ref name=v3howmanyapis>{{cite web|url=https://unix.org/version3/howmany.html|title=How many APIS are there?|website=unix.org}}</ref>

An authorized guide is available for the version.<ref>{{cite book|url=https://pubs.opengroup.org/onlinepubs/9299959899/toc.pdf|title=The Single UNIX Specification: The Authorized Guide to Version 3, 2nd Edition|publisher=[[The Open Group]]}}</ref>

====2004 Edition====
In 2004, a new edition of the POSIX.1-2001 standard was released, incorporating two technical corrigenda.<ref>{{cite web|url=https://www.opengroup.org/onlinepubs/009695399/|title=The Open Group Base Specifications Issue 6|publisher=[[The Open Group]]}}</ref><ref name=posix2004>{{cite web
  |url = https://unix.org/version3/ieee_std.html
  |title = IEEE Std 1003.1, 2004 Edition
  |access-date = July 26, 2009
}}</ref> It is called IEEE Std 1003.1, 2004 Edition.<ref name=posix2004/> Some informally call it POSIX.1-2004,<ref>{{cite web|url=https://docs.oracle.com/cd/E36784_01/html/E36883/posix.1-5.html|title=POSIX.1(5)|work=Oracle Solaris 11.2 Information Library}}</ref><ref>{{cite book|chapter-url=https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html|chapter=1.3.4 Feature Test Macros|title=The GNU C Library manual|url=https://www.gnu.org/software/libc/manual/html_node/index.html|publisher=[[The GNU Project]]}}</ref><ref>{{cite conference|title=POSIX Abstractions in Modern Operating Systems: The Old, the New, and the Missing|conference=Eleventh European Conference on Computer Systems|doi=10.1145/2901318.2901350|doi-access=free}}</ref> but this is not an official identification.

===2008: Single UNIX Specification, version 4, POSIX.1-2008===
In December 2008, the [[Austin Group]] published a new major revision of SUS and POSIX.<ref>{{cite web|url=https://www.opengroup.org/onlinepubs/9699919799/|title=The Open Group Base Specifications Issue 7, 2018 edition|website=www.opengroup.org}}</ref><ref>{{cite web
  |url = https://www.opengroup.org/bookstore/catalog/c082.htm
  |title = Base Specifications, Issue 7
  |access-date = July 26, 2009
  |publisher = The Open Group
}}</ref><ref>{{cite web
  |url = https://www.opengroup.org/austin/
  |title = The Austin Common Standards Revision Group
  |access-date = July 26, 2009
  |publisher = The Open Group
}}</ref> This is the Single UNIX Specification, Version 4 (SUSv4).<ref>{{cite web|url=https://unix.net/version4|title=Single UNIX Specification Version 4|publisher=The Open Group}}</ref>

This SUS consists of:<ref name=unixorgv4>{{cite web|url=https://unix.org/version4/overview.html|title=The Single UNIX Specification Version 4 - Introduction|website=unix.org}}</ref>
* Base Specifications, Issue 7
** Base Definitions, Issue 7
** System Interfaces, Issue 7
** Shell and Utilities, Issue 7
** Rationale, Issue 7, (Informative) 
* X/Open Curses, Issue 7 

The Base Specifications are technically identical to '''POSIX.1-2008''', which is IEEE Std 1003.1-2008.<ref name=unixorgv4/>

This version had 1833 interfaces, of which 1191 were in the System Interfaces section.<ref>{{cite web|url=https://unix.org/version4/interfaces.html|title=Version 4 Interface Counts|website=unix.org}}</ref>

====2013 Edition====
Technical Corrigendum 1 mostly targeted internationalization, and also introduced a role-based access model. A trademark ''UNIX V7'' (not to be confused with [[Version 7 Unix|V7 UNIX]], the version of [[Research Unix]] from 1979) was created to mark compliance with SUS Version 4.<ref>{{cite web|url=https://unix.org/unixv7.html|title=UNIX V7 Certification|website=unix.org}}</ref>

====2016 Edition====
Technical Corrigendum 2 was published in September 2016, leading into ''IEEE Std 1003.1-2008, 2016 Edition'' and ''Single UNIX Specification, Version 4, 2016 Edition''.

====2018 Edition, POSIX.1-2017====
In January 2018, an "administrative rollup" edition was released. It incorporates Single UNIX Specification version 4 TC1 and TC2, and is technically identical to the 2016 edition.<ref>{{cite web |title=Base Specifications, Issue 7, 2018 Edition |url=https://publications.opengroup.org/c181 |publisher=The Open Group |access-date=July 6, 2018}}</ref>

The Base Specifications are technically identical to '''POSIX.1-2017''', which is IEEE Std 1003.1-2017.<ref>{{cite web|url=https://standards.ieee.org/ieee/1003.1/7101/|title=IEEE SA - IEEE/Open Group 1003.1-2017|website=[[IEEE]]}}</ref>

==Specification==
SUSv3 totals some 3700 pages, which are divided into four main parts:

* '''Base Definitions (XBD)''' - a list of definitions and conventions used in the specifications and a list of [[C header file]]s which must be provided by compliant systems. 84 header files in total are provided.
* '''Shell and Utilities (XCU)''' - a list of utilities and a description of the shell, [[Bourne shell|sh]]. 160 utilities in total are specified.
* '''System Interfaces (XSH)''' - contains the specification of various functions which are implemented as [[system call]]s or [[Library (computing)|library]] functions. 1123 system interfaces in total are specified.
* '''Rationale (XRAT)''' - the explanation behind the standard.

The standard user command line and scripting interface is the [[POSIX]] shell, an extension of the [[Bourne Shell]] based on an early version of the [[Korn Shell]]. Other user-level programs, services and utilities include [[AWK|awk]], [[Echo (command)|echo]], [[ed (text editor)|ed]], [[Vi (text editor)|vi]], and hundreds of others. Required program-level services include basic [[input/output|I/O]] ([[Computer file|file]], [[Computer terminal|terminal]], and [[computer network|network]]) services. A test suite accompanies the standard. It is called '''PCTS''' or the '''POSIX Certification Test Suite'''.

Additionally, SUS includes [[curses (programming library)|CURSES]] (XCURSES) specification, which specifies 372 functions and 3 header files. All in all, SUSv3 specifies 1742 interfaces.

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 UNIX despite having no code in common.<ref>{{cite web|url=https://www.linux.com/news/can-gnu-ever-be-unix/|title=Can GNU ever be Unix?|first=Jem|last=Matzan|date=July 30, 2004|website=linux.com}}</ref>

==Marks for compliant systems==
<!-- This section is linked from [[UNIX98]] -->
There are five official marks for conforming systems:<ref>{{cite web|url=https://www.opengroup.org/openbrand/register/|title=UNIX(R) Certified Products - The Open Group official register of UNIX Certified Products|website=[[The Open Group]]}}</ref><ref>{{cite web|url=https://www.opengroup.org/openbrand/register/index2.html|title=The Open Brand - The full register of certified products|website=[[The Open Group]]}}</ref>
* UNIX 93<ref name="UNIX_93">{{cite web| title=The Open Brand Register, UNIX 93|url=https://www.opengroup.org/openbrand/register/xt.htm|website=[[The Open Group]]}}</ref>
* UNIX 95 - the mark for systems conforming to version 1 of the SUS<ref name="UNIX_95">{{cite web| title=The Open Brand Register, UNIX 95|url=https://www.opengroup.org/openbrand/register/xu.htm|website=[[The Open Group]]}}</ref>
* UNIX 98 - the mark for systems conforming to version 2 of the SUS<ref name="UNIX_98">{{cite web| title=The Open Brand Register, UNIX 98|url=https://www.opengroup.org/openbrand/register/xx.htm|website=[[The Open Group]]}}</ref>
* UNIX 03 - the mark for systems conforming to version 3 of the SUS<ref name="UNIX_03">{{cite web| title=The Open Brand Register, UNIX 03|url=https://www.opengroup.org/openbrand/register/xy.htm|website=[[The Open Group]]}}</ref>
* UNIX V7 - the mark for systems conforming to version 4 of the SUS (including Corrigenda)<ref name="UNIX_V7">{{cite web| title=The Open Brand Register, UNIX V7|url=https://www.opengroup.org/openbrand/register/xv7.htm|website=[[The Open Group]]}}</ref><ref>{{cite web|url=https://unix.org/unixv7.html|title=The UNIX System -- UNIX V7 Certification|website=unix.org}}</ref>

==Compliance==

{| class="wikitable sortable"
! Product
! Vendor
! Architecture
! UNIX V7<ref name="UNIX_V7"/>
! UNIX 03<ref name="UNIX_03"/>
! UNIX 98<ref name="UNIX_98"/>
! UNIX 95<ref name="UNIX_95"/>
! UNIX 93<ref name="UNIX_93"/>
|-
| [[IBM AIX|AIX]]
| [[IBM Corporation]]
| [[Power_ISA|POWER processors]]
| {{yes}}
| {{yes}}
| {{no}}
| {{no}}
| {{no}}
|-
| [[HP-UX]]
| [[Hewlett Packard Enterprise]]
| [[IA-64]], [[PA-RISC]]
| {{no}}
| {{yes}}
| {{no}}
| {{no}}
| {{no}}
|-
| [[macOS]]
| [[Apple Inc.|Apple]]
| [[x86-64]], [[ARM64]]
| {{no}}
| {{yes}}
| {{no}}
| {{no}}
| {{no}}
|-
| [[SCO OpenServer|OpenServer]]
| [[Xinuos]]
| [[IA-32]]
| {{no}}
| {{no}}
| {{no}}
| {{no}}
| {{yes}}
|-
| [[UnixWare]]
| [[Xinuos]]
| [[IA-32]]
| {{no}}
| {{no}}
| {{no}}
| {{yes}}
| {{no}}
|-
| [[z/OS]]
| [[IBM Corporation]]
| [[z/Architecture]]
| {{no}}
| {{no}}
| {{no}}
| {{yes}}
| {{no}}
|}

===Currently registered UNIX systems===

====AIX====
[[IBM AIX|AIX]] version 7, at either 7.1 TL5 (or later) or 7.2 TL2 (or later) are registered as UNIX 03 compliant.<ref>{{cite web|author=The Open Group|title=UNIX 03, AIX|url=https://www.opengroup.org/openbrand/register/brand3637.htm}}</ref> AIX version 7, at 7.2 TL5 (or later) are registered as UNIX V7 compliant.<ref>{{cite web|author=The Open Group|title=UNIX V7, AIX|url=https://www.opengroup.org/openbrand/register/brand3658.htm}}</ref> Older versions were previously certified to the UNIX 95 and UNIX 98 marks.<ref name="2003-register">{{cite web|archive-url=https://web.archive.org/web/20030802103246/http://www.opengroup.org/openbrand/register/|url=http://www.opengroup.org/openbrand/register/|title=The Open Brand - Register of Certified Products|date=July 23, 2003|archive-date=August 2, 2003|access-date=January 23, 2022|website=Open Group}}</ref>

====HP-UX====
[[HP-UX]] 11i V3 Release B.11.31 is registered as UNIX 03 compliant. Previous releases were registered as UNIX 95.<ref>{{cite web|url=http://h21007.www2.hp.com/portal/download/files/unprot/STK/HPUX_STK/impacts/i1071.html|title=UNIX 2003 Standard Profile conformance|access-date=July 22, 2014|publisher=[[Hewlett-Packard]]|archive-url=https://web.archive.org/web/20140727044600/http://h21007.www2.hp.com/portal/download/files/unprot/STK/HPUX_STK/impacts/i1071.html|archive-date=July 27, 2014}}</ref>

====macOS====
[[Apple Inc.|Apple]] [[macOS]] (formerly known as Mac OS X and OS X) is registered as UNIX 03 compliant.<ref>{{cite web|url=https://images.apple.com/macosx/docs/OSX_for_UNIX_Users_TB_July2011.pdf|title=OS X for UNIX Users|date=July 2011}}</ref> The first version registered was [[Mac OS X Leopard|Mac OS X 10.5 Leopard]], certified on October 26, 2007 (on x86 systems).<ref>{{cite web|publisher=Apple Inc.|title=Mac OS X Leopard - Technology - UNIX|url=https://www.apple.com/macosx/leopard/technology/unix.html |work=Leopard Technology Overview|access-date=June 11, 2007|quote=Leopard is now an Open Brand UNIX 03 Registered Product, conforming to the SUSv3 and POSIX 1003.1 specifications for the C API, Shell Utilities, and Threads. |archive-url = https://web.archive.org/web/20070823040630/http://www.apple.com/macosx/leopard/technology/unix.html <!-- Bot retrieved archive --> |archive-date = August 23, 2007}}</ref><ref>{{cite web|author=The Open Group|title=Mac OS X Version 10.5 Leopard on Intel-based Macintosh computers certification|url=https://www.opengroup.org/openbrand/register/brand3555.htm|access-date=June 12, 2007}}</ref> All versions of [[macOS]] from Mac OS X Leopard to [[macOS Catalina|macOS 10.15 Catalina]], except for [[Mac OS X Lion|OS X Lion]],<ref>{{Cite web |title=Re: was OS X version 10.7 Lion UNIX 03 certified? |url=https://www.mail-archive.com/austin-group-l@opengroup.org/msg02006.html |access-date=2021-07-22 |website=www.mail-archive.com |archive-date=April 29, 2020 |archive-url=https://web.archive.org/web/20200429213555/https://www.mail-archive.com/austin-group-l@opengroup.org/msg02006.html |url-status=live }}</ref> have been registered on Intel-based systems, and all versions from [[macOS Big Sur|macOS 11 Big Sur]], the successor to macOS Catalina, to [[MacOS Sonoma|macOS 14 Sonoma]] have been registered on both x86-64 and ARM64 systems.<ref>{{cite web |title=Open Brand |url=https://www.opengroup.org/openbrand/register/apple.htm |access-date=2022-11-15 |website=www.opengroup.org}}</ref>

====Xinuos====
[[UnixWare]] 7.1.3 and later is registered as UNIX 95 compliant.
[[OpenServer]] 5 and 6 are registered as UNIX 93 compliant.

====z/OS====
IBM [[z/OS]] 1.2 and higher is registered as UNIX 95 compliant.
z/OS 1.9, released on September 28, 2007, and subsequent releases "better align" with UNIX 03.<ref>{{cite book
  | url = https://www.redbooks.ibm.com/redbooks/pdfs/sg247427.pdf
  | title = z/OS Version 1 Release 9 Implementation
  | access-date = June 9, 2024
  | date = December 2007
  | pages = 4-5,156-162
  | publisher = IBM
  | id = SG24-7427-00
  | edition = First
}}</ref>

===Previously registered UNIX systems===

====EulerOS====
[[EulerOS]] 2.0 for the [[x86-64]] architecture was registered as UNIX&nbsp;03 compliant.<ref>{{cite press release|url=https://www.huawei.com/en/news/2016/9/huawei-kunlun-euleros-unix-certification|title=Huawei KunLun EulerOS 2.0 Operating System Passes UNIX Certification|date=September 9, 2016|access-date=October 29, 2016|publisher=[[Huawei]]}}</ref><ref name="euler-cert">{{cite web|author=The Open Group|title=UNIX 03, EulerOS|url=https://www.opengroup.org/openbrand/register/brand3622.htm}}</ref> The UNIX&nbsp;03 conformance statement shows that the standard C compiler is from the [[GNU Compiler Collection]] ({{mono|gcc}}), and that the system is a [[Linux distribution]] of the [[Red Hat Enterprise Linux]] family.<ref name="EulerOS_conformance_commands">{{cite web| url=https://www.opengroup.org/csq/repository/norationale=1&noreferences=1&RID=huawei%252FCX1%252F1.html| title=Huawei Conformance Statement: Commands and Utilities V4| author=Peng Shen| publisher=The Open Group| access-date=October 29, 2016}}</ref> The UNIX 03 certification expired in September 2022 and has not been renewed.<ref name="euler-cert" />

====FTX====
[[Stratus Technologies]] DNCP Series servers running FTX Release 3 were registered as UNIX 93 compliant.<ref>{{cite web|author=The Open Group|title=The Open Brand - Register of Certified Products - UNIX 93|url=https://www.opengroup.org/openbrand/register/xt.htm|archive-url=https://web.archive.org/web/20161005132055/https://www.opengroup.org/openbrand/register/xt.htm|archive-date=October 5, 2016}}</ref>

====Inspur K-UX====
[[Inspur K-UX]] 2.0 and 3.0 for the [[x86-64]] architecture were certified as UNIX&nbsp;03 compliant.<ref>{{cite web|url=https://www.opengroup.org/openbrand/register/brand3596.htm |title=The Open Brand Register of Certified Products|access-date=May 29, 2014|publisher=The Open Group|date=May 29, 2014}}</ref><ref name="inspur_conformance_statement">{{cite web| url=https://www.opengroup.org/csq/repository/RID=inspur%252FXY1%252F1.html| title=Inspur Conformance Statement| author=Xie Ruohong| publisher=The Open Group| access-date=December 8, 2015}}</ref> The UNIX&nbsp;03 conformance statement for Inspur K-UX 2.0 and 3.0 shows that the standard C compiler is from the [[GNU Compiler Collection]] ({{mono|gcc}}), and that the system is a [[Linux distribution]] of the [[Red Hat]] family.<ref name="inspur_conformance_commands">{{cite web| url=https://www.opengroup.org/csq/repository/RID=inspur%252FCX1%252F1.html| title=Inspur Conformance Statement: Commands and Utilities V4| author=Xie Ruohong| publisher=The Open Group| access-date=December 8, 2015}}</ref>

====IRIX====

[[Silicon Graphics|SGI]] [[IRIX]] 6.5 was registered as UNIX 95 compliant.<ref>{{cite web|url=http://www.opengroup.org/openbrand/register/xu013.htm|title=Silicon Graphics Inc - UNIX 95|website=Open Group|archive-date=2003-08-02|archive-url=https://web.archive.org/web/20030802154406/http://www.opengroup.org/openbrand/register/xu013.htm|url-status=dead}}</ref>

====OS/390====
IBM [[OS/390]] was registered as UNIX 95 compliant beginning with the V2R4 release.<ref>{{cite web|title=Register of Open Branded Products (OS/390)|archive-url=https://web.archive.org/web/20030629093915/http://www.opengroup.org/openbrand/register/xu009.htm|url=http://www.opengroup.org/openbrand/register/xu009.htm|archive-date=2003-06-29|date=2003-06-19|website=Open Group|url-status=dead}}</ref>

====Reliant UNIX====
The last [[Reliant UNIX]] versions were registered as UNIX 95 compliant (XPG4 hard branding).

====Solaris====
[[Solaris (operating system)|Solaris]] 11.4 was previously registered as UNIX v7 compliant in 2018.<ref>{{cite web|url=https://www.opengroup.org/openbrand/register/brand3642.htm|title=UNIX V7 - The Open Brand Register, Oracle Corporation|website=[[The Open Group]]|archive-url= https://web.archive.org/web/20200114100431/https://www.opengroup.org/openbrand/register/brand3642.htm|archive-date=January 14, 2020|access-date=January 16, 2021}}</ref> Solaris 11 and Solaris 10 were registered as UNIX 03 compliant on [[32-bit]] and [[64-bit]] [[x86]] ([[X86-64]]) and [[SPARC]] systems. Solaris 8 and 9 were registered as UNIX 98 compliant on [[32-bit]] [[x86]] and [[SPARC]] systems; 64-bit x86 systems were not supported. Solaris 2.4 and 2.6, on both x86 and SPARC, were certified to the UNIX 93 and UNIX 95 marks respectively.<ref name="2003-register" />

Solaris 2.5.1 was also registered as UNIX 95 compliant on the [[PReP]] [[PowerPC]] platform in 1996, but the product was withdrawn before more than a few dozen copies had been sold.<ref>{{cite web|url=http://www.ocf.berkeley.edu/solaris/versions/solaris/2.5.1.html|title=Solaris 2.5.1|archive-url=https://web.archive.org/web/20050912194850/http://www.ocf.berkeley.edu/solaris/versions/solaris/2.5.1.html|archive-date=September 12, 2005|url-status=dead}}</ref>

====Tru64 UNIX====
[[Tru64 UNIX]] V5.1A and later were registered as UNIX 98 compliant.<ref>{{cite web|url=http://www.opengroup.org/openbrand/register/xx001.htm|title=Compaq Computer Corporation - UNIX 95|website=Open Group|archive-date=2003-06-29|archive-url=https://web.archive.org/web/20030629103042/http://www.opengroup.org/openbrand/register/xx001.htm}}</ref>

====Other====
Other operating systems previously registered as UNIX 95 or UNIX 93 compliant:
*[[NCR Corporation|NCR]] UNIX SVR4
*[[NEC]] UX/4800

===Non-registered Unix-like systems===
Developers and vendors of [[Unix-like]] operating systems such as [[Linux]], [[FreeBSD]], and [[MINIX]] typically do not certify their distributions and do not install full POSIX utilities by default.

For Linux, [[pax (command)|pax]] command is usually not installed; furthermore, pax command packages available for Linux often lack pax file format support required by POSIX.<ref>{{cite web| url = https://bugs.launchpad.net/rpm/+bug/1329914| website = Ubuntu bug tracker| title = Bug #1329914 "No UNIX compatible pax implementation" : Bugs : RPM| date = June 13, 2014}}</ref> Sometimes, SUS compliance can be improved by installing additional packages, but very few Linux systems can be configured to be completely conformant. The [[Linux Standard Base]] was formed in 2001 as an attempt to standardize the internal structures of Linux-based systems for increased compatibility. It is based on the POSIX specifications, the Single UNIX Specification, and other open standards, and also extends them in several areas; but there are some conflicts between the LSB and the POSIX standards.<ref>{{cite ISO standard | csnumber=38825 | title=ISO/IEC TR 24715:2006 - Information technology -- Programming languages, their environments and system software interfaces -- Technical Report on the Conflicts between the ISO/IEC 9945 (POSIX) and the Linux Standard Base (ISO/IEC 23360) | access-date=October 15, 2011}}</ref><ref>{{cite web|url=https://personal.opengroup.org/~ajosey/tr20-08-2005.txt|title=Conflicts between ISO/IEC 9945 (POSIX) and the Linux Standard Base.|first=Andrew|last=Josey|type=Unapproved Draft|website=personal.opengroup.org|date=August 29, 2005}}</ref> Few [[Linux distribution]]s actually go through certification as LSB compliant.<ref>{{cite web| url=https://www.linuxbase.org/lsb-cert/productdir.php?by_lsb| title=Certified Products Product Directory| access-date=December 9, 2015| publisher=The Linux Foundation|archive-url=https://archive.today/20121220223126/https://www.linuxbase.org/lsb-cert/productdir.php?by_lsb|archive-date=December 20, 2012}}</ref>

[[Darwin (operating system)|Darwin]], the open source subset of macOS, has behavior that can be set to comply with UNIX&nbsp;03.<ref>{{Cite web|url=https://developer.apple.com/documentation/Darwin/Reference/Manpages/man5/compat.5.html|title=Mac OS X Manual Page for compat(5) - Mac OS X 10.3|date=October 23, 2005|website=developer.apple.com|archive-url=https://web.archive.org/web/20090310143649/http://developer.apple.com/documentation/Darwin/Reference/Manpages/man5/compat.5.html|archive-date=March 10, 2009|access-date=May 24, 2018}}</ref><ref>{{Cite web|url=https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/compat.5.html|title=compat(5) Manual Page - macOS 10.9|date=June 30, 2010|website=developer.apple.com|access-date=May 24, 2018}}</ref> Darwin uses a 4.4BSD-derived pax command,<ref>{{Cite web|url=https://developer.apple.com/documentation/Darwin/Reference/Manpages/man1/pax.1/html|title=Mac OS X Manual Page for pax(1) - Mac OS X 10.3|date=October 23, 2005|website=developer.apple.com|archive-url=https://web.archive.org/web/20090310143649/http://developer.apple.com/documentation/Darwin/Reference/Manpages/man1/pax.1.html|archive-date=March 10, 2009|access-date=November 25, 2023}}</ref> which lacks multibyte support for filenames.{{cn|date=November 2023}}

FreeBSD previously had a "C99 and POSIX Conformance Project" which aimed for compliance with a subset of the Single UNIX Specification, and documentation where there were differences.<ref>{{cite web|url=http://www.freebsd.org/projects/c99/|title=FreeBSD C99 and POSIX conformance project|publisher=FreeBSD Project|archive-url=https://web.archive.org/web/20131223025351/http://www.freebsd.org/projects/c99/|archive-date=December 23, 2013|url-status=dead}}</ref> FreeBSD pax command, derived from 4.4BSD, does not fully support pax file format.<ref>{{man|1|pax|FreeBSD}}</ref> pax and ustar in-archive format use the same with slightly different defaults (5120 block size vs 10240 block size);<ref>{{cite web|url=https://pubs.opengroup.org/onlinepubs/9699919799/|title=pax - portable archive interchange
|publisher=The Open Group}}</ref> however, FreeBSD's pax lacks the extended PAX headers used for extended character set support. FreeBSD man pages sometimes indicate deviations from POSIX and thus SUS in their STANDARDS sections.<ref>{{man|1|awk|FreeBSD}}</ref>

OpenBSD man pages sometimes indicate deviations from POSIX and thus SUS in their STANDARDS sections.<ref>{{man|1|sh|OpenBSD}}</ref><ref>{{man|1|awk|OpenBSD}}</ref>

MINIX pax command does not support pax file format<ref>{{cite web|url=https://man.minix3.org/cgi-bin/man.cgi?query=pax&apropos=0&sektion=0&manpath=Minix+3.3.0&arch=default&format=html|title=pax(1)|website=man.minix3.org}}</ref> and thereby fails POSIX.1-2001.

==See also==
* [[List of Unix commands]]
* [[Unix wars]]
* [[Functional specification]]
* [[Manual page (Unix)|UNIX manual]]
* [[Open system (computing)]]
* [[Open standard]]
* [[POSIX]]

==References==
{{Reflist}}

==External links==
* {{cite journal|title=Single UNIX Specification Frequently Asked Questions|version=1.12|date=June 8, 2020|author=Andrew Josey|url=https://www.opengroup.org/austin/papers/single_unix_faq.html|website=opengroup.org}}
* [https://unix.org/what_is_unix/single_unix_specification.html The Single UNIX Specification], unix.org
* Single UNIX Specification, Version 1
** [https://pubs.opengroup.org/onlinepubs/009656599/toc.pdf X/Open CAE Specification System Interface Definitions, Issue 4, Version 2], 1994, opengroup.org
** [https://pubs.opengroup.org/onlinepubs/9695969499/toc.pdf X/Open CAE Specification System Interfaces and Headers, Issue 4, Version 2], 1994, opengroup.org
** [https://pubs.opengroup.org/onlinepubs/009656399/toc.pdf X/Open CAE Specification Commands and Utilities, Issue 4, Version 2], 1994, opengroup.org
** [https://pubs.opengroup.org/onlinepubs/009656199/toc.pdf X/Open CAE Specification Networking Services, Issue 4], 1994, opengroup.org
* [https://publications.opengroup.org/c43x Single UNIX® Specification, Version 1 Document Set (UNIX 95)], opengroup.org – requires login to download
* [https://pubs.opengroup.org/onlinepubs/7908799/index.html The Single UNIX Specification, Version 2], 1997, opengroup.org
* [https://pubs.opengroup.org/onlinepubs/009695399/ The Open Group Base Specifications Issue 6], 2004, opengroup.org
* [https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/ The Open Group Base Specifications Issue 7, 2008 edition], opengroup.org
* [https://pubs.opengroup.org/onlinepubs/9699919799.2013edition/ The Open Group Base Specifications Issue 7, 2013 edition], opengroup.org
* [https://pubs.opengroup.org/onlinepubs/9699919799.2016edition/ The Open Group Base Specifications Issue 7, 2016 edition], opengroup.org
* [https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/ The Open Group Base Specifications Issue 7, 2018 edition], opengroup.org
* [https://pubs.opengroup.org/onlinepubs/9699919799/ The Open Group Base Specifications Issue 7], opengroup.org – latest edition
* [https://publications.opengroup.org/standards/unix/t101 Single UNIX Specification, Version 4, 2018 Edition], opengroup.org
* [https://pubs.opengroup.org/onlinepubs/009638999/toc.pdf X/Open Curses, Issue 4, Version 2], 1996, opengroup.org
* [https://pubs.opengroup.org/onlinepubs/9699909599/toc.pdf X/Open Curses, Issue 7], 2009, opengroup.org
* [https://pubs.opengroup.org/onlinepubs/7899949299/toc.pdf POSIX Technical Corrigendum 1], 1003.1-2001/Cor 1-2001, opengroup.org
* [https://publications.opengroup.org/u130 Single UNIX Specification, Version 4 Technical Corrigendum No. 1], IEEE Std 1003.1-2008/Cor 1-2013, opengroup.org
* [https://publications.opengroup.org/u160 Single UNIX Specification, Version 4 Technical Corrigendum No. 2], IEEE Std 1003.1-2008/Cor 2-2016, opengroup.org

{{Open Group standards|state=uncollapsed}}
{{IEEE standards}}

{{DEFAULTSORT:Single Unix Specification}}
[[Category:IEEE standards]]
[[Category:Open Group standards]]
[[Category:POSIX]]
[[Category:Unix standards]]