Editing Single UNIX Specification (section)

==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>