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Cygwin is a Unix-like environment and command-line interface for Microsoft Windows. Cygwin provides native integration of Windows-based applications, data, and other system resources with applications, software tools, and data of the Unix-like environment.

MSYS2 is an independent rewrite of MSYS, based on modern Cygwin (POSIX compatibility layer) and MinGW-w64 with the aim of better interoperability with native Windows software.

Gow (Gnu On Windows) is the lightweight alternative to Cygwin. It uses a convenient Windows installer that installs about 130 extremely useful open source UNIX applications compiled as native win32 binaries. It is designed to be as small as possible, about 10 MB, as opposed to Cygwin which can run well over 100 MB depending upon options.

The GNU Core Utilities or coreutils is a package of GNU software containing many of the basic tools, such as cat, ls, and rm, needed for Unix-like operating systems. It is a combination of a number of earlier packages, including textutils, shellutils, and fileutils, along with some other miscellaneous utilities.