If you use Windows today and type ls, cat, grep, or awk in a terminal, there is a good chance something useful will happen. That was not always true. For most of the history of personal computing, Unix/Linux and Windows lived on opposite sides of a cultural border. Unix people had pipes, small composable tools, shell scripts, make, sed, awk, grep, tar, and the idea that everything was a file. Windows people had drive letters, backslashes, COMMAND.COM or cmd.exe, and an API that did not care much about what POSIX thought.
Yet there has always been a demand for Unix tools on Windows. Some of it came from programmers who wanted the same build scripts everywhere. Some came from administrators who missed grep and awk. Some came from companies trying to port big Unix applications to NT without rewriting them all. The result is a long, strange history of Unix-on-Windows layers, toolkits, compromises, and almost-but-not-quite compatibility.
Easy?
The simplest version of the problem sounds trivial. How hard can cat be? Open a file, copy bytes to standard output, done. Writing ls is a little more work, but Windows has directory APIs. Common commands like cp, mv, rm, mkdir are not very mysterious. Even pipes are not foreign to Windows. A lot of the everyday Unix command set can be ported as ordinary Win32 console programs with some path handling and enough patience.
But not all of Unix or Linux translates cleanly to Windows. The big issue is fork(). On Unix, a process can clone itself. The child gets a copy of the parent’s address space, open file descriptors, environment, signal state, and so on. Modern kernels make this efficient with copy-on-write memory, but the programming model is old and deeply baked into Unix. Shells use it constantly. Servers use it. Build systems use it. Scripting languages assume it exists, or at least that the surrounding environment behaves as though it does.
Windows process creation is different. Windows has CreateProcess(), which starts a new program. That is a perfectly reasonable model, but it is not fork() (more like fork()+exec()). If you are just launching notepad.exe, no problem. If you are trying to implement a POSIX shell that forks, redirects file descriptors, adjusts the environment, and then starts another program, the mismatch is extreme and you’ll have to do some strange things to fake things out.
One of the early commercial answers was the MKS Toolkit, originally from Mortice Kern Systems. MKS gave Windows users a pile of familiar commands, shells, and development tools. It was not just ls and friends; it included things like ksh, vi, grep, find, awk, make, and many of the utilities needed to move scripts and build procedures between Unix and Windows. The current PTC MKS documentation still describes it in exactly that spirit: Unix shells and hundreds of commands for interoperability with Windows.
MKS was attractive because it treated Windows as Windows. You were not necessarily pretending your machine was a Unix workstation. You were getting a Unix-flavored toolbox that could operate in a Windows environment. For many people, that was enough. You could write scripts, process text, drive builds, and avoid learning three different syntaxes for the same job.
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