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The Unix wars were struggles between vendors to set a standard for the Unix operating system in the late 1980s and early 1990s.

Origins

Both AT&T Corporation and University of California, Berkeley are important in the early history of Unix. Although AT&T's Bell Labs created Unix, by the 1980s, Berkeley's Computer Systems Research Group was the leading non-commercial Unix developer.^[1] In the mid-1980s, the three common versions of Unix were AT&T's System III, the basis of Microsoft's Xenix and the IBM-endorsed PC/IX, among others; AT&T's System V, which it sought to establish as the new Unix standard;^[2] and the Berkeley Software Distribution (BSD). All were derived from AT&T's Research Unix but had diverged considerably. Further, each vendor's version of Unix was different to some degree.

For example, at a mid-1980s Usenix conference, many AT&T staff had buttons that read "System V: Consider it Standard" and a number of major vendors were promoting products based on System V. On the other hand, System V did not yet have TCP/IP networking built-in, while BSD 4.2 did; vendors of engineering workstations were nearly all using BSD, and posters reading "4.2 > V" were available.

Several vendors formed the X/Open standards group in 1984 to promote compatible open systems, and they chose to base their system on Unix. X/Open caught AT&T's attention. To increase the uniformity of Unix, AT&T and leading BSD Unix vendor Sun Microsystems started work in 1987 on a unified system. (The feasibility of this had been demonstrated a few years earlier by the US Army Ballistic Research Laboratory's System V environment for BSD Unix.) This was released in 1988 as System V Release 4 (SVR4) which still lives to this day through its derivative OpenIndiana.^[3]

While this decision was applauded by customers and the trade press, certain other Unix licensees feared Sun would be unduly advantaged. They formed the Open Software Foundation (OSF) in 1988. The same year, AT&T and another group of licensees responded by forming Unix International (UI). Technical issues soon took a back seat to vicious and public commercial competition between the two "open" versions of Unix, with X/Open holding the middle ground.

A 1990 study of various Unix versions' reliability found that in each version, between a quarter and a third of operating system utilities could be made to crash by fuzzing; the researchers attributed this, in part, to the "race for features, power, and performance" resulting from BSD–System V rivalry, which left developers little time to worry about reliability.^[4]

Standardization

The 1988 POSIX standard initially concentrated on system C library functions beyond what was included in the forthcoming C standard; later it expanded to specify other aspects of the system environment. POSIX specified a "lowest common denominator" that could be met by both System V and BSD-based variants, as well as some non-Unix systems, with a reasonable amount of effort.

In March 1993, the major participants in UI and OSF formed the Common Open Software Environment (COSE) alliance, effectively marking the end of the most significant era of the Unix wars. In June, AT&T sold its Unix assets to Novell, and in October Novell transferred the Unix brand to X/Open.

In 1996, X/Open and the new OSF merged to form the Open Group. COSE work such as the Single UNIX Specification, the current standard for branded Unix, is now the responsibility of the Open Group, which also controls the current POSIX standards.

Since then, occasional bursts of Unix factionalism have broken out, such as the HP/SCO "3DA" alliance in 1995, and Project Monterey in 1998, a teaming of IBM, SCO, Sequent, and Intel which was followed by litigation (SCO v. IBM) between IBM and the new SCO, formerly Caldera.

BSD and the rise of Linux

BSD worked to purge copyrighted AT&T code from their version between 1989 and 1994. During this time, various open-source BSD x86 derivatives took shape, starting with 386BSD, which was soon succeeded by FreeBSD and NetBSD. OpenBSD emerged in 1995 as a fork of NetBSD, and DragonFly BSD as a fork from FreeBSD in 2003. Mac OS X v10.5 is the first operating system with open source BSD code to be certified as fully Unix compliant.^[5] BSD systems can claim direct ancestry from Version 7 Unix. According to Open Source advocate Eric Raymond, BSD systems can be considered "genetic Unix", if not "trademark Unix".^[6]

During BSD's period of legal turmoil (1992–94),^[7] the nearly-complete GNU operating system was made operational by the inclusion of the Linux kernel and lumped together under the label "Linux". GNU had been written from scratch to avoid copyright issues. Linux systems broadly aim for compatibility with POSIX.

References

^ Fiedler, Ryan (October 1983). "The Unix Tutorial / Part 3: Unix in the Microcomputer Marketplace". BYTE. p. 132. Retrieved January 30, 2015.
^ Shea, Tom (February 20, 1984). "New developments may decide battle over Unix". InfoWorld. pp. 43–45. Archived from the original on February 16, 2021. Retrieved February 25, 2016.
^ "Home". www.openindiana.org. Retrieved May 9, 2023.
^ Miller, Barton P.; Fredriksen, Louis; So, Bryan (1990). "An empirical study of the reliability of UNIX utilities" (PDF). Communications of the ACM. 33 (12): 32–44. doi:10.1145/96267.96279. S2CID 14313707. Archived (PDF) from the original on October 24, 2018. Retrieved September 10, 2015.
^ "Mac OS X Leopard Achieves UNIX 03 Product Standard Certification". Archived from the original on June 9, 2011. Retrieved July 28, 2009.
^ "Microsoft Buys into SCO Group's Unix". Archived from the original on August 17, 2009. Retrieved March 20, 2009.
^ Unix System Laboratories v. Berkeley Software, 832 F. Supp. 790 (D.N.J. 1993).

Sources

Unix Wars (Living Internet)
The UNIX Wars Archived 2004-02-18 at the Wayback Machine (Bell Labs)
The UNIX System – History and Timeline (The Open Group)
Unix Standards Archived 2007-09-29 at the Wayback Machine (Eric S. Raymond, The Art of Unix Programming)
Chapter 11. OSF and UNIX International (Peter H. Salus, The Daemon, the GNU and the Penguin)

[fiedler198310-1] Fiedler, Ryan (October 1983). "The Unix Tutorial / Part 3: Unix in the Microcomputer Marketplace". BYTE. p. 132. Retrieved January 30, 2015.

[shea19840220-2] Shea, Tom (February 20, 1984). "New developments may decide battle over Unix". InfoWorld. pp. 43–45. Archived from the original on February 16, 2021. Retrieved February 25, 2016.

[3] "Home". www.openindiana.org. Retrieved May 9, 2023.

[4] Miller, Barton P.; Fredriksen, Louis; So, Bryan (1990). "An empirical study of the reliability of UNIX utilities" (PDF). Communications of the ACM. 33 (12): 32–44. doi:10.1145/96267.96279. S2CID 14313707. Archived (PDF) from the original on October 24, 2018. Retrieved September 10, 2015.

[5] "Mac OS X Leopard Achieves UNIX 03 Product Standard Certification". Archived from the original on June 9, 2011. Retrieved July 28, 2009.

[6] "Microsoft Buys into SCO Group's Unix". Archived from the original on August 17, 2009. Retrieved March 20, 2009.

[832_F.Supp._790-7] Unix System Laboratories v. Berkeley Software, 832 F. Supp. 790 (D.N.J. 1993).

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@@ Line 1: / Line 1: @@
 {{short description|Struggles between Unix vendors to set the standard for Unix}}
 {{More citations needed|date=December 2009}}
+{{Use mdy dates|date=April 2023}}
-[[Image:Unix timeline.en.svg|thumb|450px|Unix genealogy tree]]
+[[File:Unix timeline.en.svg|thumb|450px|Unix genealogy tree]]
 The '''Unix wars''' were struggles between vendors to set a standard for the [[Unix]] [[operating system]] in the late 1980s and early 1990s.
 ==Origins==
-Although [[AT&T Corporation]] created [[Unix]], by the 1980s, the [[University of California, Berkeley]] [[Computer Systems Research Group]] was the leading noncommercial Unix developer.<ref name="fiedler198310">{{cite news | url=https://archive.org/stream/byte-magazine-1983-10/1983_10_BYTE_08-10_UNIX#page/n133/mode/2up | title=The Unix Tutorial / Part 3: Unix in the Microcomputer Marketplace | work=BYTE | date=October 1983 | access-date=30 January 2015 | author=Fiedler, Ryan | pages=132}}</ref> In the mid-1980s, the three common versions of Unix were AT&T's [[UNIX System III|System III]], the basis of [[Microsoft]]'s [[Xenix]] and the IBM-endorsed [[PC/IX]], among others; AT&T's [[UNIX System V|System V]], which it sought to establish as the new Unix standard;<ref name="shea19840220">{{cite news | url=https://books.google.com/books?id=hS4EAAAAMBAJ&pg=PA43 | title=New developments may decide battle over Unix | work=InfoWorld | date=1984-02-20 | access-date=25 February 2016 | author=Shea, Tom | pages=43–45 | archive-date=2021-02-16 | archive-url=https://web.archive.org/web/20210216064125/https://books.google.com/books?id=hS4EAAAAMBAJ&pg=PA43 | url-status=live }}</ref> and the [[Berkeley Software Distribution]] (BSD). All were derived from AT&T's [[Research Unix]], but had diverged considerably. Further, each vendor's version of Unix was different to some degree.
+Both [[AT&T Corporation]] and [[University of California, Berkeley]] are important in the early [[history of Unix]]. Although AT&T's [[Bell Labs]] created [[Unix]], by the 1980s, Berkeley's [[Computer Systems Research Group]] was the leading non-commercial Unix developer.<ref name="fiedler198310">{{cite news | url=https://archive.org/stream/byte-magazine-1983-10/1983_10_BYTE_08-10_UNIX#page/n133/mode/2up | title=The Unix Tutorial / Part 3: Unix in the Microcomputer Marketplace | work=BYTE | date=October 1983 | access-date=30 January 2015 | author=Fiedler, Ryan | pages=132}}</ref> In the mid-1980s, the three common versions of Unix were AT&T's [[UNIX System III|System III]], the basis of [[Microsoft]]'s [[Xenix]] and the IBM-endorsed [[PC/IX]], among others; AT&T's [[UNIX System V|System V]], which it sought to establish as the new Unix standard;<ref name="shea19840220">{{cite news | url=https://books.google.com/books?id=hS4EAAAAMBAJ&pg=PA43 | title=New developments may decide battle over Unix | work=InfoWorld | date=1984-02-20 | access-date=25 February 2016 | author=Shea, Tom | pages=43–45 | archive-date=2021-02-16 | archive-url=https://web.archive.org/web/20210216064125/https://books.google.com/books?id=hS4EAAAAMBAJ&pg=PA43 | url-status=live }}</ref> and the [[Berkeley Software Distribution]] (BSD). All were derived from AT&T's [[Research Unix]] but had diverged considerably. Further, each vendor's version of Unix was different to some degree.
-For example, at a mid-1980s [[Usenix]] conference, many AT&T staff had buttons which read "System V: Consider it Standard" and a number of major vendors were promoting products based on System V. On the other hand, System V did not yet have TCP/IP networking built in and BSD 4.2 did; vendors of engineering workstations were nearly all using BSD and posters reading "4.2 > V" were available.
+For example, at a mid-1980s [[Usenix]] conference, many AT&T staff had buttons that read "System V: Consider it Standard" and a number of major vendors were promoting products based on System V. On the other hand, System V did not yet have TCP/IP networking built-in, while BSD 4.2 did; vendors of engineering workstations were nearly all using BSD, and posters reading "4.2 > V" were available.
-A group of vendors formed the [[X/Open]] [[open standard|standard]]s group in 1984, with the aim of forming compatible [[open system (computing)|open system]]s. They chose to base their system on Unix.
+Several vendors formed the [[X/Open]] [[open standard|standard]]s group in 1984 to promote compatible [[open system (computing)|open system]]s, and they chose to base their system on Unix. X/Open caught AT&T's attention. To increase the uniformity of Unix, AT&T and leading BSD Unix vendor [[Sun Microsystems]] started work in 1987 on a unified system. (The feasibility of this had been demonstrated a few years earlier by the [[US Army]] [[Ballistic Research Laboratory]]'s System V environment for BSD Unix.) This was released in 1988 as [[System V Release 4]] (SVR4) which still lives to this day through its derivative [[OpenIndiana]].<ref>{{Cite web |title=Home |url=https://www.openindiana.org/ |access-date=2023-05-09 |website=www.openindiana.org |language=en}}</ref>
+While this decision was applauded by customers and the trade press, certain other Unix licensees feared Sun would be unduly advantaged. They formed the [[Open Software Foundation]] (OSF) in 1988. The same year, AT&T and another group of licensees responded by forming [[Unix International]] (UI). Technical issues soon took a back seat to vicious and public commercial competition between the two "open" versions of Unix, with X/Open holding the middle ground.
-X/Open caught AT&T's attention. To increase the uniformity of Unix, AT&T and leading BSD Unix vendor [[Sun Microsystems]] started work in 1987 on a unified system. (The feasibility of this had been demonstrated a few years earlier by the [[US Army]] [[Ballistic Research Laboratory]]'s System V environment for BSD Unix.) This was eventually released as ''System V Release 4'' (SVR4).
+A 1990 study of various Unix versions' reliability found that in each version, between a quarter and a third of operating system utilities could be made to [[Crash (computing)|crash]] by [[fuzz testing|fuzzing]]; the researchers attributed this, in part, to the "race for features, power, and performance" resulting from BSD–System V rivalry, which left developers little time to worry about reliability.<ref>{{Cite journal |last1=Miller |first1=Barton P. |first2=Louis |last2=Fredriksen |first3=Bryan |last3=So |title=An empirical study of the reliability of UNIX utilities |journal=[[Communications of the ACM]] |volume=33 |issue=12 |year=1990 |pages=32–44 |url=http://ftp.cs.wisc.edu/paradyn/technical_papers/fuzz.pdf |doi=10.1145/96267.96279 |s2cid=14313707 |access-date=2015-09-10 |archive-date=2018-10-24 |archive-url=https://web.archive.org/web/20181024163412/http://ftp.cs.wisc.edu/paradyn/technical_papers/fuzz.pdf |url-status=live }}</ref>
-While this decision was applauded by customers and the trade press, certain other Unix licensees feared Sun would be unduly advantaged. They formed the [[Open Software Foundation]] (OSF) in 1988. The same year, AT&T and another group of licensees responded by forming [[UNIX International]] (UI). Technical issues soon took a back seat to vicious and public commercial competition between the two "open" versions of Unix, with X/Open holding the middle ground.
-A 1990 study of various Unix versions' reliability found that on each version, between a quarter and a third of operating system utilities could be made to [[Crash (computing)|crash]] by [[fuzz testing|fuzzing]]; the researchers attributed this, in part, to the "race for features, power, and performance" resulting from BSD–System V rivalry, which left developers little time to worry about reliability.<ref>{{Cite journal |last1=Miller |first1=Barton P. |first2=Louis |last2=Fredriksen |first3=Bryan |last3=So |title=An empirical study of the reliability of UNIX utilities |journal=[[Communications of the ACM]] |volume=33 |issue=12 |year=1990 |pages=32–44 |url=http://ftp.cs.wisc.edu/paradyn/technical_papers/fuzz.pdf |doi=10.1145/96267.96279 |s2cid=14313707 |access-date=2015-09-10 |archive-date=2018-10-24 |archive-url=https://web.archive.org/web/20181024163412/http://ftp.cs.wisc.edu/paradyn/technical_papers/fuzz.pdf |url-status=live }}</ref>
 ==Standardization==
-The 1988 [[POSIX]] standard initially concentrated on system C library functions beyond what was included in the forthcoming C standard; later it expanded to specify other aspects of the system environment. [[POSIX]] specified a "lowest common denominator" that could be met by both System V and BSD-based variants, as well as some non-UNIX systems, with a reasonable amount of effort.
+The 1988 [[POSIX]] standard initially concentrated on system [[C library]] functions beyond what was included in the forthcoming C standard; later it expanded to specify other aspects of the system environment. POSIX specified a "lowest common denominator" that could be met by both System V and BSD-based variants, as well as some non-Unix systems, with a reasonable amount of effort.
-In March 1993, the major participants in UI and OSF formed the [[Common Open Software Environment]] (COSE) alliance, effectively marking the end of the most significant era of the Unix wars. In June, AT&T sold its UNIX assets to [[Novell]], and in October Novell transferred the Unix brand to X/Open.
+In March 1993, the major participants in UI and OSF formed the [[Common Open Software Environment]] (COSE) alliance, effectively marking the end of the most significant era of the Unix wars. In June, AT&T sold its Unix assets to [[Novell]], and in October Novell transferred the Unix brand to X/Open.
-In 1996, X/Open and the new OSF merged to form the [[Open Group]]. COSE work such as the [[Single UNIX Specification]], the current standard for branded Unix, is now the responsibility of the Open Group, which also controls the current [[POSIX]] standards.
+In 1996, X/Open and the new OSF merged to form the [[Open Group]]. COSE work such as the [[Single UNIX Specification]], the current standard for branded Unix, is now the responsibility of the Open Group, which also controls the current POSIX standards.
-Since then, occasional bursts of Unix factionalism have broken out, such as the [[Hewlett-Packard|HP]]/SCO "[[3DA]]" alliance in 1995, and [[Project Monterey]] in 1998, a teaming of [[IBM]], [[Santa Cruz Operation|SCO]], [[Sequent Computer Systems|Sequent]] and [[Intel Corporation|Intel]] which was followed by litigation ([[SCO v. IBM]]) between IBM and the [[The SCO Group|new SCO, formerly Caldera]].
+Since then, occasional bursts of Unix factionalism have broken out, such as the [[Hewlett-Packard|HP]]/SCO "[[3DA]]" alliance in 1995, and [[Project Monterey]] in 1998, a teaming of [[IBM]], [[Santa Cruz Operation|SCO]], [[Sequent Computer Systems|Sequent]], and [[Intel]] which was followed by litigation ([[SCO v. IBM]]) between IBM and the [[The SCO Group|new SCO, formerly Caldera]].
 ==BSD and the rise of Linux==
-BSD purged copyrighted AT&T code from 1989 to 1994. During this time various open-source BSD x86 derivatives took shape, starting with [[386BSD]], which was soon succeeded by [[FreeBSD]] and [[NetBSD]]. [[OpenBSD]] emerged in 1995 as a fork of NetBSD, [[DragonFly BSD]] as a fork from FreeBSD in 2003. [[Mac OS X v10.5]] is the first operating system with open source BSD code to be certified as fully Unix compliant.<ref>{{Cite web |url=http://www.opengroup.org/comm/press/19-2-nov07.htm |title=Mac OS X Leopard Achieves UNIX 03 Product Standard Certification |access-date=2009-07-28 |archive-date=2011-06-09 |archive-url=https://web.archive.org/web/20110609195918/http://www.opengroup.org/comm/press/19-2-nov07.htm |url-status=live }}</ref> BSD systems can claim direct ancestry from [[Version 7 Unix]]. Or, according to Open Source advocate [[Eric Raymond]], BSD systems can be considered "genetic Unix", if not "trademark Unix."<ref>{{Cite web | url=http://www.internetnews.com/dev-news/print.php/2208691 | title=Microsoft Buys into SCO Group's Unix | access-date=2009-03-20 | archive-date=2009-08-17 | archive-url=https://web.archive.org/web/20090817191424/http://www.internetnews.com/dev-news/print.php/2208691 | url-status=live }}</ref>
+BSD worked to purge copyrighted AT&T code from their version between 1989 and 1994. During this time, various open-source BSD x86 derivatives took shape, starting with [[386BSD]], which was soon succeeded by [[FreeBSD]] and [[NetBSD]]. [[OpenBSD]] emerged in 1995 as a fork of NetBSD, and [[DragonFly BSD]] as a fork from FreeBSD in 2003. [[Mac OS X v10.5]] is the first operating system with open source BSD code to be certified as fully Unix compliant.<ref>{{Cite web |url=http://www.opengroup.org/comm/press/19-2-nov07.htm |title=Mac OS X Leopard Achieves UNIX 03 Product Standard Certification |access-date=2009-07-28 |archive-date=2011-06-09 |archive-url=https://web.archive.org/web/20110609195918/http://www.opengroup.org/comm/press/19-2-nov07.htm |url-status=live }}</ref> BSD systems can claim direct ancestry from [[Version 7 Unix]]. According to Open Source advocate [[Eric Raymond]], BSD systems can be considered "genetic Unix", if not "trademark Unix".<ref>{{Cite web | url=http://www.internetnews.com/dev-news/print.php/2208691 | title=Microsoft Buys into SCO Group's Unix | access-date=2009-03-20 | archive-date=2009-08-17 | archive-url=https://web.archive.org/web/20090817191424/http://www.internetnews.com/dev-news/print.php/2208691 | url-status=live }}</ref>
 During BSD's [[UNIX System Laboratories, Inc. v. Berkeley Software Design, Inc.|period of legal turmoil]] (1992–94),<ref name="832 F.Supp. 790">{{cite court |litigants=Unix System Laboratories v. Berkeley Software |vol=832 |reporter=F. Supp. |opinion=790 |court=[[United States District Court for the District of New Jersey|D.N.J.]] |date=1993 |url=https://www.leagle.com/decision/19931622832fsupp79011506 }}</ref> the nearly-complete [[GNU]] operating system was made operational by the inclusion of the [[Linux kernel]] and lumped together under the label "[[Linux]]". GNU had been written from scratch to avoid copyright issues. Linux systems broadly aim for compatibility with [[POSIX]].