Unix-like

Some computers work in a special way.

They act like a system called Unix. These systems are called Unix-like. They follow a certain way of working.

Linux is one famous example. Many people use Linux on computers. Some systems also run on big servers. These tools help computers do many tasks. It is a very helpful way to work. You can find these systems in many places.

Some computers work in a special way. They act like a system called Unix. These systems are called Unix-like.

Unix-like systems follow a set of rules. They act like the original Unix system. There is no single rule for this name. People have different ideas about what it means. Some systems are made from the original Unix code. These are called genetic Unix.

Other systems are branded Unix. These systems meet a special standard. A group called The Open Group owns the Unix name. They give permission to use it. It costs a lot of money to get this mark. This is why many systems are just called Unix-like.

Linux is a famous example. It is a free system. It follows the Unix way of working. Many people use Linux on personal computers. It is also used on big servers. Other examples include FreeBSD and OpenBSD. Some systems like macOS also act like Unix. These tools help computers do many tasks. They are used in many places around the world.

A Unix-like operating system is a type of computer software that works in a way similar to the original Unix system.

These systems are very important because they power many different things. You can find them on big servers and on personal computers. Some systems even run on special devices. They follow general ideas for how a system should be designed. However, there is no single technical rule that defines the name. People often have different opinions about what makes a system Unix-like.

How a system becomes Unix-like depends on its history and its rules. Some systems are "genetic UNIX" because they come from the original code made at Bell Labs. Other systems are "trademark UNIX" because they passed a special test. This test is called the Single UNIX Specification. The Open Group owns the UNIX name and manages this test. If a system meets the rules, it can use the official name. Many other systems are simply patterned after the original design. These systems might not have any connection to the original code at all.

The history of these systems started many years ago. Unix itself was created in 1969. In the late 1970s and early 1980s, new Unix-like systems began to appear. Some were made for businesses, like Idris in 1978 or UNOS in 1982. In 1979, AT&T allowed companies to buy licenses for Unix. This led to many famous systems like AIX, HP-UX, and IRIX. Later, free and low-cost versions like Linux and Minix emerged. These new tools changed how people used computers everywhere.

There are many specific names you might see in the world of computing. Linux is one of the most well-known examples. Other examples include FreeBSD and OpenBSD. Some systems, like macOS, are even certified to meet the official standards. There are also special tools like the Apache web server and the Bash shell. These tools are designed to work well on Unix-like systems. Even Microsoft Windows has ways to act like Unix. For example, the Windows Subsystem for Linux lets certain programs run on Windows computers.

You can think of Unix-like systems as a family of cousins. They might not all be related by blood, but they act very much alike. Just as siblings might share a way of speaking, these systems share a way of working. They use similar commands to talk to the computer. This makes it easier for people to use different machines. If you learn how to use one, you will often know how to use others. This shared way of working connects many different parts of our digital world.

A Unix-like operating system is a type of software that behaves in a manner similar to the original Unix system.

These systems are vital because they power many different technologies. You can find them running on large servers and personal computers. They are also used on many other types of devices. While they follow general design philosophies, there is no single technical standard that defines the term. Because of this, people often disagree on which systems are truly Unix-like.

The term is complicated by legal rules and trademarks. The Open Group owns the UNIX trademark and manages the Single UNIX Specification. This specification is a set of rules that a system must follow to be officially certified. The Open Group does not actually approve of the term "Unix-like." They consider it a misuse of their trademark. They prefer that "UNIX" be written in uppercase. They also suggest using it as an adjective, such as for a "UNIX system." Some people use wildcards like "*nix" to refer to these systems. This includes names like Linux, Minix, or even macOS.

History shows how these systems evolved over many decades. The original Unix was created in 1969. In the late 1970s and early 1980s, Unix-like systems began to appear. Some were proprietary systems made for businesses. For example, Idris appeared in 1978 and UNOS arrived in 1982. In 1979, AT&T began allowing commercial sublicensing of Unix. This allowed many different proprietary systems to be developed. These included AIX, HP-UX, IRIX, and SunOS. These systems eventually replaced many of the earlier proprietary clones.

As these systems grew, they became difficult to use together. This incompatibility led to the creation of interoperability standards. These include POSIX and the Single UNIX Specification. During the 1980s and 1990s, free and low-cost substitutes emerged. These included 4.4BSD, Linux, and Minix. Some of these became the foundation for modern systems. For instance, macOS is based on BSD variants. The BSD code was originally developed at the University of California, Berkeley. While it started with Bell Labs code, it has since replaced all AT&T code.

Researchers have suggested three specific categories for these systems. The first is "genetic UNIX," which is derived from the original Bell Labs code. Most commercial systems fall into this group. The second category is "trademark UNIX." These are commercial systems that meet the Single UNIX Specification. They are allowed to use the official UNIX name. Examples include certain versions of macOS and Linux distributions like EulerOS. The third category includes systems patterned after Unix but with no direct connection. This includes most free and open-source implementations like Linux.

Many systems use compatibility layers to act like Unix. This allows software meant for one system to run on another. For example, IBM z/OS uses UNIX System Services to achieve certification. Microsoft Windows also offers ways to interact with Unix. The Windows Subsystem for Linux provides a Linux-compatible kernel interface. It can run Ubuntu user-mode binaries on top of it. Another version, WSL2, uses a virtual machine to provide a full Linux environment. Other tools like Cygwin and MSYS allow common open-source software to run on Windows.

Unix-like systems are deeply connected to the modern digital world. Many popular applications are designed specifically for these environments. The Apache web server and the Bash shell are two major examples. Because these systems share similar commands, skills can transfer between them. If you learn to use one Unix-like system, you can often use others. This shared way of working helps different parts of our technology work together smoothly.