A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-like application is one that behaves like the corresponding Unix command or shell. Although there are general philosophies for Unix design, there is no technical standard defining the term, and opinions can differ about the degree to which a particular operating system or application is Unix-like. Some well-known examples of Unix-like operating systems include Linux, FreeBSD and OpenBSD. These systems are often used on servers as well as on personal computers and other devices. Many popular applications, such as the Apache web server and the Bash shell, are also designed to be used on Unix-like systems.
Definition
The Open Group owns the UNIX trademark and administers the Single UNIX Specification, with the "UNIX" name being used as a certification mark. They do not approve of the construction "Unix-like", and consider it a misuse of their trademark. Their guidelines require "UNIX" to be presented in uppercase or otherwise distinguished from the surrounding text, strongly encourage using it as a branding adjective for a generic word such as "system", and discourage its use in hyphenated phrases.
Other parties frequently treat "Unix" as a genericized trademark. Some add a wildcard character to the name to make an abbreviation like "Un*x" or "*nix", since Unix-like systems often have Unix-like names such as AIX, A/UX, HP-UX, IRIX, Linux, Minix, Ultrix, Xenix, and XNU. These patterns do not literally match many system names, but are still generally recognized to refer to any UNIX system, descendant, or work-alike, even those with completely dissimilar names such as Darwin/macOS, illumos/Solaris or FreeBSD.
In 2007, Wayne R. Gray sued to dispute the status of UNIX as a trademark, but lost his case, and lost again on appeal, with the court upholding the trademark and its ownership.
History
This section needs additional citations for verification. (April 2010) |
"Unix-like" systems started to appear in the late 1970s and early 1980s. Many proprietary versions, such as Idris (1978), UNOS (1982), Coherent (1983), and UniFlex (1985), aimed to provide businesses with the functionality available to academic users of UNIX.
When AT&T allowed relatively inexpensive commercial binary sublicensing of UNIX in 1979, a variety of proprietary systems were developed based on it, including AIX, HP-UX, IRIX, SunOS, Tru64, Ultrix, and Xenix. These largely displaced the proprietary clones. Growing incompatibility among these systems led to the creation of interoperability standards, including POSIX and the Single UNIX Specification.
Various free, low-cost, and unrestricted substitutes for UNIX emerged in the 1980s and 1990s, including 4.4BSD, Linux, and Minix. Some of these have in turn been the basis for commercial "Unix-like" systems, such as BSD/OS and macOS. Several versions of (Mac) OS X/macOS running on Intel-based Mac computers have been certified under the Single UNIX Specification. The BSD variants are descendants of UNIX developed by the University of California at Berkeley, with UNIX source code from Bell Labs. However, the BSD code base has evolved since then, replacing all the AT&T code. Since the BSD variants are not certified as compliant with the Single UNIX Specification, they are referred to as "UNIX-like" rather than "UNIX".
Categories
Dennis Ritchie, one of the original creators of Unix, expressed his opinion that Unix-like systems such as Linux are de facto Unix systems.Eric S. Raymond and Rob Landley have suggested that there are three kinds of Unix-like systems: "genetic UNIX" derived from the original Bell Labs UNIX, "trademark UNIX" (or "branded UNIX") for which the Open Group have licensed the UNIX trademark, and a third category of operating systems that are not in either of those categories but that are patterned after the original Bell Labs UNIX.
Genetic UNIX
Those systems with a historical connection to the AT&T codebase. Most commercial UNIX systems fall into this category. So do the BSD systems, which are descendants of work done at the University of California, Berkeley in the late 1970s and early 1980s. Some of these systems have no original AT&T code but can still trace their ancestry to AT&T designs.
Trademark or branded UNIX
These systems—largely commercial in nature—have been determined by the Open Group to meet the Single UNIX Specification and are allowed to carry the UNIX name. Most such systems are commercial derivatives of the System V code base in one form or another, although Apple macOS 10.5 and later is a BSD variant that has been certified, and EulerOS and Inspur K-UX are Linux distributions that have been certified. A few other systems (such as IBM z/OS) earned the trademark through a POSIX compatibility layer and are not otherwise inherently Unix systems. Many ancient UNIX systems no longer meet this definition.
Other UNIXes
Broadly, any Unix-like system that behaves in a manner roughly consistent with the UNIX specification, including having a "program which manages your login and command line sessions"; more specifically, this can refer to systems such as Linux or Minix that behave similarly to a UNIX system but have no genetic or trademark connection to the AT&T code base. Most free/open-source implementations of the UNIX design, whether genetic UNIX or not, fall into the restricted definition of this third category due to the expense of obtaining Open Group certification, which costs thousands of dollars.
Around 2001 Linux was given the opportunity to get a certification including free help from the POSIX chair Andrew Josey for the symbolic price of one dollar.[citation needed] There have been some activities to make Linux POSIX-compliant, with Josey having prepared a list of differences between the POSIX standard and the Linux Standard Base specification, but in August 2005, this project was shut down because of missing interest at the LSB work group.[citation needed] As per § Trademark or branded UNIX, some Linux distributions have been certified.
Compatibility layers
Some non-Unix-like operating systems provide a Unix-like compatibility layer, with varying degrees of Unix-like functionality.
- IBM z/OS's UNIX System Services is sufficiently complete as to be certified as trademark UNIX.
- Cygwin, MSYS, and MSYS2 each provide a GNU environment on top of the Microsoft Windows user API, sufficient for most common open source software to be compiled and run.
- The MKS Toolkit and UWIN are comprehensive interoperability tools which allow the porting of Unix programs to Windows.
- Windows NT-type systems have a POSIX environmental subsystem.
- Subsystem for Unix-based Applications (previously Interix) provides Unix-like functionality as a Windows NT subsystem (discontinued).
- Windows Subsystem for Linux provides a Linux-compatible kernel interface developed by Microsoft and containing no Linux code, with Ubuntu user-mode binaries running on top of it.
- Windows Subsystem for Linux version 2 (WSL2) provides a fully functional Linux environment running in a virtual machine.
- OpenHarmony employs the third-party musl libc library and native APIs ports, providing support on POSIX for Linux syscalls within the Linux kernel and LiteOS default kernels side of the system multi-kernel Kernel Abstract Layer subsystem for vendor and developers interoperability.
- HarmonyOS with HarmonyOS NEXT system has OpenHarmony user mode that contains musl libc library and native APIs ports, providing support with POSIX for Linux syscalls within the default kernels of the Linux kernel standard system and LiteOS small and lightweight system side of the system multi-kernel Kernel Abstract Layer subsystem for interoperability on legacy Unix-like functionalities.
Other means of Windows-Unix interoperability include:
- The above Windows packages can be used with various X servers for Windows
- Hummingbird Connectivity provides several ways for Windows machines to connect to Unix and Linux machines, from terminal emulators to X clients and servers, and others
- The Windows Resource Kits for versions of Windows NT include a Bourne Shell, some command-line tools, and a version of Perl
- Hamilton C shell is a version of csh written specifically for Windows.
See also
- List of Unix-like systems
- Berkeley Software Distribution
- Linux kernel and Linux distribution
- List of Linux distributions
- List of Unix commands
- List of operating systems
- Free Software Foundation and GNU Project
References
- "Legal: Trademark Guidelines". The Open Group. Archived from the original on October 2, 2013. Retrieved November 4, 2013.
- Eric S. Raymond; Guy L. Steele Jr. "UN*X". The Jargon File. Retrieved January 22, 2009.
- Gray v. Novell, X/Open Company, The SCO Group (11th Cir. January 7, 2011), Text.
- "More Wayne Gray. No! Again? Still?! Yes. He Wants to Reopen Discovery in the USPTO Dispute". Groklaw. April 22, 2011. Archived from the original on June 18, 2022. Retrieved September 26, 2022.
- "Mac OS X Version 10.5 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
- "Mac OS X Version 10.6 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
- "Mac OS X Version 10.8 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
- "OS X Version 10.9 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
- "OS X version 10.10 Yosemite on Intel-based Mac computers". The Open Group. Retrieved October 23, 2015.
- "OS X version 10.11 El Capitan on Intel-based Mac computers". The Open Group. Retrieved October 23, 2015.
- "macOS version 10.12 Sierra on Intel-based Mac computers". The Open Group. Retrieved October 13, 2016.
- Interview with Dennis M. Ritchie Manuel Benet, LinuxFocus, July 1999
- Raymond, Eric; Landley, Rob. "OSI Position Paper on the SCO-vs.-IBM Complaint". The meaning of 'Unix'.
- "Huawei KunLun EulerOS 2.0 Operating System Passes UNIX Certification" (Press release). Huawei. September 9, 2016. Retrieved October 29, 2016.
- The Open Group. "UNIX 03, EulerOS".
- "The Open Brand Register of Certified Products". The Open Group. May 29, 2014. Retrieved May 29, 2014.
- "Introduction to UNIX – Part 1: Basic Concepts". Archived from the original on April 5, 2018. Retrieved April 4, 2014.
- "The Open Brand Fee Schedule". The Open Group. November 6, 2003. Retrieved July 22, 2022.
- Andrew Josey (August 20, 2005). "Conflicts between ISO/IEC 9945 (POSIX) and the Linux Standard Base". The Open Group. Retrieved July 23, 2012.
- "What is the Windows Subsystem for Linux?". Microsoft Docs. July 18, 2023.
External links
- Unix-like Definition, by The Linux Information Project (LINFO)
- UNIX history – a history time line graph of most UNIX and Unix-like systems by Éric Lévénez
- Grokline's UNIX Ownership History Project – a project to map out the technical history of UNIX and Unix-like systems at the Wayback Machine (archived June 22, 2004)
A Unix like sometimes referred to as UN X nix or NIX operating system is one that behaves in a manner similar to a Unix system although not necessarily conforming to or being certified to any version of the Single UNIX Specification A Unix like application is one that behaves like the corresponding Unix command or shell Although there are general philosophies for Unix design there is no technical standard defining the term and opinions can differ about the degree to which a particular operating system or application is Unix like Some well known examples of Unix like operating systems include Linux FreeBSD and OpenBSD These systems are often used on servers as well as on personal computers and other devices Many popular applications such as the Apache web server and the Bash shell are also designed to be used on Unix like systems Evolution of Unix and Unix like systems starting in 1969DefinitionThe Open Group owns the UNIX trademark and administers the Single UNIX Specification with the UNIX name being used as a certification mark They do not approve of the construction Unix like and consider it a misuse of their trademark Their guidelines require UNIX to be presented in uppercase or otherwise distinguished from the surrounding text strongly encourage using it as a branding adjective for a generic word such as system and discourage its use in hyphenated phrases Other parties frequently treat Unix as a genericized trademark Some add a wildcard character to the name to make an abbreviation like Un x or nix since Unix like systems often have Unix like names such as AIX A UX HP UX IRIX Linux Minix Ultrix Xenix and XNU These patterns do not literally match many system names but are still generally recognized to refer to any UNIX system descendant or work alike even those with completely dissimilar names such as Darwin macOS illumos Solaris or FreeBSD In 2007 Wayne R Gray sued to dispute the status of UNIX as a trademark but lost his case and lost again on appeal with the court upholding the trademark and its ownership HistoryThis section needs additional citations for verification Please help improve this article by adding citations to reliable sources in this section Unsourced material may be challenged and removed April 2010 Learn how and when to remove this message Simplified history of Unix like operating systems Unix like systems started to appear in the late 1970s and early 1980s Many proprietary versions such as Idris 1978 UNOS 1982 Coherent 1983 and UniFlex 1985 aimed to provide businesses with the functionality available to academic users of UNIX When AT amp T allowed relatively inexpensive commercial binary sublicensing of UNIX in 1979 a variety of proprietary systems were developed based on it including AIX HP UX IRIX SunOS Tru64 Ultrix and Xenix These largely displaced the proprietary clones Growing incompatibility among these systems led to the creation of interoperability standards including POSIX and the Single UNIX Specification Various free low cost and unrestricted substitutes for UNIX emerged in the 1980s and 1990s including 4 4BSD Linux and Minix Some of these have in turn been the basis for commercial Unix like systems such as BSD OS and macOS Several versions of Mac OS X macOS running on Intel based Mac computers have been certified under the Single UNIX Specification The BSD variants are descendants of UNIX developed by the University of California at Berkeley with UNIX source code from Bell Labs However the BSD code base has evolved since then replacing all the AT amp T code Since the BSD variants are not certified as compliant with the Single UNIX Specification they are referred to as UNIX like rather than UNIX CategoriesDennis Ritchie one of the original creators of Unix expressed his opinion that Unix like systems such as Linux are de facto Unix systems Eric S Raymond and Rob Landley have suggested that there are three kinds of Unix like systems genetic UNIX derived from the original Bell Labs UNIX trademark UNIX or branded UNIX for which the Open Group have licensed the UNIX trademark and a third category of operating systems that are not in either of those categories but that are patterned after the original Bell Labs UNIX Genetic UNIX Those systems with a historical connection to the AT amp T codebase Most commercial UNIX systems fall into this category So do the BSD systems which are descendants of work done at the University of California Berkeley in the late 1970s and early 1980s Some of these systems have no original AT amp T code but can still trace their ancestry to AT amp T designs Trademark or branded UNIX These systems largely commercial in nature have been determined by the Open Group to meet the Single UNIX Specification and are allowed to carry the UNIX name Most such systems are commercial derivatives of the System V code base in one form or another although Apple macOS 10 5 and later is a BSD variant that has been certified and EulerOS and Inspur K UX are Linux distributions that have been certified A few other systems such as IBM z OS earned the trademark through a POSIX compatibility layer and are not otherwise inherently Unix systems Many ancient UNIX systems no longer meet this definition Other UNIXes Broadly any Unix like system that behaves in a manner roughly consistent with the UNIX specification including having a program which manages your login and command line sessions more specifically this can refer to systems such as Linux or Minix that behave similarly to a UNIX system but have no genetic or trademark connection to the AT amp T code base Most free open source implementations of the UNIX design whether genetic UNIX or not fall into the restricted definition of this third category due to the expense of obtaining Open Group certification which costs thousands of dollars Around 2001 Linux was given the opportunity to get a certification including free help from the POSIX chair Andrew Josey for the symbolic price of one dollar citation needed There have been some activities to make Linux POSIX compliant with Josey having prepared a list of differences between the POSIX standard and the Linux Standard Base specification but in August 2005 this project was shut down because of missing interest at the LSB work group citation needed As per Trademark or branded UNIX some Linux distributions have been certified Compatibility layersSome non Unix like operating systems provide a Unix like compatibility layer with varying degrees of Unix like functionality IBM z OS s UNIX System Services is sufficiently complete as to be certified as trademark UNIX Cygwin MSYS and MSYS2 each provide a GNU environment on top of the Microsoft Windows user API sufficient for most common open source software to be compiled and run The MKS Toolkit and UWIN are comprehensive interoperability tools which allow the porting of Unix programs to Windows Windows NT type systems have a POSIX environmental subsystem Subsystem for Unix based Applications previously Interix provides Unix like functionality as a Windows NT subsystem discontinued Windows Subsystem for Linux provides a Linux compatible kernel interface developed by Microsoft and containing no Linux code with Ubuntu user mode binaries running on top of it Windows Subsystem for Linux version 2 WSL2 provides a fully functional Linux environment running in a virtual machine OpenHarmony employs the third party musl libc library and native APIs ports providing support on POSIX for Linux syscalls within the Linux kernel and LiteOS default kernels side of the system multi kernel Kernel Abstract Layer subsystem for vendor and developers interoperability HarmonyOS with HarmonyOS NEXT system has OpenHarmony user mode that contains musl libc library and native APIs ports providing support with POSIX for Linux syscalls within the default kernels of the Linux kernel standard system and LiteOS small and lightweight system side of the system multi kernel Kernel Abstract Layer subsystem for interoperability on legacy Unix like functionalities Other means of Windows Unix interoperability include The above Windows packages can be used with various X servers for Windows Hummingbird Connectivity provides several ways for Windows machines to connect to Unix and Linux machines from terminal emulators to X clients and servers and others The Windows Resource Kits for versions of Windows NT include a Bourne Shell some command line tools and a version of Perl Hamilton C shell is a version of csh written specifically for Windows See alsoList of Unix like systems Berkeley Software Distribution Linux kernel and Linux distribution List of Linux distributions List of Unix commands List of operating systems Free Software Foundation and GNU ProjectReferences Legal Trademark Guidelines The Open Group Archived from the original on October 2 2013 Retrieved November 4 2013 Eric S Raymond Guy L Steele Jr UN X The Jargon File Retrieved January 22 2009 Gray v Novell X Open Company The SCO Group 11th Cir January 7 2011 Text More Wayne Gray No Again Still Yes He Wants to Reopen Discovery in the USPTO Dispute Groklaw April 22 2011 Archived from the original on June 18 2022 Retrieved September 26 2022 Mac OS X Version 10 5 on Intel based Macintosh computers The Open Group Retrieved December 4 2014 Mac OS X Version 10 6 on Intel based Macintosh computers The Open Group Retrieved December 4 2014 Mac OS X Version 10 8 on Intel based Macintosh computers The Open Group Retrieved December 4 2014 OS X Version 10 9 on Intel based Macintosh computers The Open Group Retrieved December 4 2014 OS X version 10 10 Yosemite on Intel based Mac computers The Open Group Retrieved October 23 2015 OS X version 10 11 El Capitan on Intel based Mac computers The Open Group Retrieved October 23 2015 macOS version 10 12 Sierra on Intel based Mac computers The Open Group Retrieved October 13 2016 Interview with Dennis M Ritchie Manuel Benet LinuxFocus July 1999 Raymond Eric Landley Rob OSI Position Paper on the SCO vs IBM Complaint The meaning of Unix Huawei KunLun EulerOS 2 0 Operating System Passes UNIX Certification Press release Huawei September 9 2016 Retrieved October 29 2016 The Open Group UNIX 03 EulerOS The Open Brand Register of Certified Products The Open Group May 29 2014 Retrieved May 29 2014 Introduction to UNIX Part 1 Basic Concepts Archived from the original on April 5 2018 Retrieved April 4 2014 The Open Brand Fee Schedule The Open Group November 6 2003 Retrieved July 22 2022 Andrew Josey August 20 2005 Conflicts between ISO IEC 9945 POSIX and the Linux Standard Base The Open Group Retrieved July 23 2012 What is the Windows Subsystem for Linux Microsoft Docs July 18 2023 External linksUnix like Definition by The Linux Information Project LINFO UNIX history a history time line graph of most UNIX and Unix like systems by Eric Levenez Grokline s UNIX Ownership History Project a project to map out the technical history of UNIX and Unix like systems at the Wayback Machine archived June 22 2004
