Original author(s)Steve Chamberlain, Cygnus Solutions
Developer(s)Cygnus Solutions, Red Hat, Cygwin project volunteers
Initial releaseOctober 18, 1995; 27 years ago (1995-10-18)
Stable release
3.4.6-1[1] Edit this on Wikidata / 14 February 2023; 6 months ago (14 February 2023)
Written inC/C++
Operating systemMicrosoft Windows
TypePOSIX standard utilities, POSIX standard library, C standard library, compatibility layer
LicenseGPLv3, LGPLv3[2] Edit this on Wikidata

Cygwin (/ˈsɪɡwɪn/ SIG-win)[3] is a Unix-like environment and command-line interface for Microsoft Windows. Cygwin's purpose is expressed in its motto: "Get that Linux feeling – on Windows".

The terminal emulator Mintty is the default command-line interface provided to interact with the environment.[4] The Cygwin installation's directory layout mimics the root file system of Unix-like systems, with directories such as /bin, /home, /etc, /usr, and /var.

In addition to providing many Unix utilities and a Unix look and feel, Cygwin allows source code designed for Unix-like operating systems to be compiled and run on Windows with minimal modification.

Cygwin provides native integration of Windows-based applications. Thus it is possible to launch Windows applications from the Cygwin environment, as well as to use Cygwin tools and applications within the Windows operating context.[5]

Cygwin consists of two parts:

  1. a dynamic-link library (DLL) in the form of a C standard library that acts as a compatibility layer for the POSIX API.
  2. an extensive collection of software tools and applications that provide a Unix-like look and feel.[5]

Cygwin is free and open-source software, released under the GNU Lesser General Public License version 3.[6] It was originally developed by Cygnus Solutions,[7][8] which was later acquired by Red Hat (now part of IBM), to port the Linux toolchain to Win32, including the GNU Compiler Suite. Rather than rewrite the tools to use the Win32 runtime environment, Cygwin implemented a POSIX-compatible environment in the form of a dynamic-link library (DLL).[9]


The Cygwin environment is provided in two versions; the full 64-bit version and a stripped down 32-bit version that is slowly being phased out. Cygwin consists of a library that implements the POSIX system call API in terms of Windows system calls to enable running of a large number of application programs equivalent to those on Unix systems, and a GNU development toolchain (including GCC and GDB) to allow software development. Programmers have ported many Unix, GNU, BSD and Linux programs and packages to Cygwin, including the X Window System, K Desktop Environment 3, GNOME,[10] Apache, and TeX. Cygwin permits installing inetd, syslogd, sshd, Apache, and other daemons as standard Windows services, allowing Microsoft Windows systems to emulate Unix and Linux servers.

Cygwin programs are installed by running Cygwin's "setup"[11] program, which downloads the necessary program and feature package files from repositories on the Internet. As mentioned, there are two versions of this setup program, one for 32-bit versions of the Cygwin DLL, and corresponding applications, and one for 64-bit versions. Setup can install, update, and remove programs and their source code packages. A complete installation will take in excess of 90 GB[12] of hard disk space, but usable configurations may require as little as 1 or 2 GB.

Efforts to reconcile concepts that differ between Unix and Windows systems include:

The version of gcc that comes with Cygwin has various extensions for creating Windows DLLs, specifying whether a program is a windowing or console-mode program, adding resources, etc. Support for compiling programs that do not require the POSIX compatibility layer provided by the Cygwin DLL used to be included in the default gcc, but as of 2014 is provided by cross-compilers contributed by the MinGW-w64 project.

Cygwin is used heavily for porting many popular pieces of software to the Windows platform.[citation needed] It is used to compile Sun Java, LibreOffice, and even web server software like Lighttpd and Hiawatha.[17]

The Cygwin API library is licensed under the GNU Lesser General Public License version 3 (or later) with an exception to allow linking to any free and open-source software whose license conforms to the Open Source Definition[18] (less strict than the Free Software Definition).


Cygwin began in 1995 as a project of Steve Chamberlain, a Cygnus engineer who observed that Windows NT and 95 used COFF as their object file format, and that GNU already included support for x86 and COFF, and the C library newlib. He thought it would be possible to retarget GCC and produce a cross compiler generating executables that could run on Windows. This proved practical and a prototype was quickly developed.

The next step was to attempt to bootstrap the compiler on a Windows system, requiring sufficient emulation of Unix to let the GNU configure shell script run. A Bourne shell-compatible command interpreter, such as bash, was needed and in turn a fork system call emulation and standard input/output. Windows includes similar functionality, so the Cygwin library just needed to provide a POSIX-compatible application programming interface (API) and properly translate calls and manage private versions of data, such as file descriptors.

Initially, Cygwin was called gnuwin32 (not to be confused with the current GnuWin32 project). The name was changed to Cygwin32 to emphasize Cygnus' role in creating it. When Microsoft registered the trademark Win32, the 32 was dropped to simply become Cygwin.

By 1996, other engineers had joined in, because it was clear that Cygwin would be a useful way to provide Cygnus' embedded tools hosted on Windows systems (the previous strategy had been to use DJGPP). It was especially attractive because it was possible to do a three-way cross-compile, for instance to use a hefty Sun Microsystems workstation to build, say, a Windows-x-MIPS cross-compiler, which was faster than using the PC at the time. In 1999, Cygnus offered Cygwin 1.0 as a commercial product[19] of interest in its own right although subsequent versions have not been released, instead relying on continued open source releases.

Geoffrey Noer was the project lead from 1996 to 1999.[20][21] Christopher Faylor was lead from 1999 to 2004 when he left Red Hat and became co-lead with Corinna Vinschen[22] until Faylor withdrew from active participation in the project mid-2014.[23] Corinna Vinschen has been the project lead from mid-2014 to date (as of March 30, 2023).[24]

From June 23, 2016 the Cygwin library version 2.5.2 was licensed under the GNU Lesser General Public License (LGPL) version 3,[25] so is now possible to link against closed source applications. Before this was available there were two possibilities: to release the source code of the application or buy a Cygwin license to release a closed source application.


Cygwin's base package selection is fairly small (about 100 MB[26]), containing little more than the bash (interactive user) and dash (installation) shells and the core file and text manipulation utilities expected of a Unix command line. Additional packages are available as optional installs from within the Cygwin Setup program and package manager ("setup-x86_64.exe" – 64bit). These include (from over 12000 others[27]):

The Cygwin/X project contributes an implementation of the X Window System that allows graphical Unix programs to display their user interfaces on the Windows desktop. This can be used with both local and remote programs. Cygwin/X supports over 500 packages including major X window managers, desktop environments, and applications, for example:

In addition to the low-level Xlib/XCB libraries for developing X applications, Cygwin ships with various higher-level and cross-platform GUI frameworks, including GTK+ and Qt.

The Cygwin Ports project provided[when?] many additional packages that were not available in the Cygwin distribution itself. Examples included GNOME and K Desktop Environment 3 as well as the MySQL database and the PHP scripting language. Most ports have been adopted by volunteer maintainers as Cygwin packages, and Cygwin Ports are no longer maintained.

See also


  1. ^ Corinna Vinschen (14 February 2023). "cygwin 3.4.6-1". Retrieved 19 February 2023.
  2. ^ "Cygwin Licensing Terms". Archived from the original on 2012-07-28. Retrieved 2022-12-15.
  3. ^ Hall, Larry (2004-09-14). "Re: How do you pronounce it?". Cygwin (Mailing list). Archived from the original on 2011-08-30. Retrieved 2007-10-10.
  4. ^ "Cygwin". Archived from the original on 2015-11-21. Retrieved 2015-11-21.
  5. ^ a b "Cygwin FAQ". Archived from the original on 2021-05-07. Retrieved 2021-01-07.
  6. ^ "Cygwin library now available under GNU Lesser General Public License". Red Hat. Archived from the original on 2016-06-24. Retrieved 2016-06-23.
  7. ^ "A brief history of the Cygwin project". Cygwin. 2018-02-02. Archived from the original on 2020-01-08. Retrieved 2020-01-10.
  8. ^ "Cygwin32: A Free Win32 Porting Layer for UNIX® Applications". USENIX. 1998-08-03. Archived from the original on 2020-01-11. Retrieved 2020-01-10.
  9. ^ "(Solved) Linux Subsystem vs Cygwin vs MobaXterm". Tech Help Forum by How-To Geek. 2017-01-24. Archived from the original on 2023-02-20. Retrieved 2019-03-15.
  10. ^ "Cygwin Ports". Archived from the original on 11 May 2015. Retrieved 2 May 2015.
  11. ^ Delorie, DJ (2000-04-17). "New Cygwin Net Release". Cygwin (Mailing list). Archived from the original on 2014-12-20. Retrieved 2020-01-10.
  12. ^ "What is the current full install size of Cygwin?". StackOverflow. 2018-05-28. Archived from the original on 2021-01-24. Retrieved 2020-01-11.
  13. ^ Vinschen, Corinna (2016-01-16). "Updated: Cygwin 2.4.0-1". Cygwin Announcements (Mailing list). Archived from the original on 2020-01-11. Retrieved 2020-01-11.
  14. ^ "Cygwin FAQ: How is fork() implemented?". Archived from the original on October 20, 2010. Retrieved Oct 10, 2010.
  15. ^ "Highlights of Cygwin Functionality: Process Creation". Archived from the original on December 30, 2014. Retrieved Dec 24, 2014.
  16. ^ Blake, Eric (Jan 15, 2009). "Bash doesn't launch the applications directly". Cygwin (Mailing list). Archived from the original on June 13, 2011. Retrieved Oct 10, 2010.
  17. ^ Leisink, Hugo. "Hiawatha webserver". Archived from the original on 2021-01-24. Retrieved 2021-01-07.
  18. ^ "What are the licensing terms?". Cygwin. Archived from the original on 2012-07-28.
  19. ^ "Cygwin Unites Unix and Windows Apps". Google Books. 1999-11-15. Archived from the original on 2023-02-20. Retrieved 2020-01-13.
  20. ^ Delorie, DJ (1999-02-17). "fyi: who does what". Cygwin (Mailing list). Archived from the original on 2004-02-14. Retrieved 2020-01-13.
  21. ^ Noer, Geoffrey (1999-02-19). "A partial goodbye..." Cygwin (Mailing list). Archived from the original on 2004-02-02. Retrieved 2020-01-13.
  22. ^ Faylor, Christopher (2004-03-31). "Changing jobs". Cygwin (Mailing list). Archived from the original on 2015-09-06. Retrieved 2020-01-13.
  23. ^ Faylor, Christopher (2014-07-31). "Christopher Faylor – Withdrawing from the project". Cygwin (Mailing list). Archived from the original on 2014-12-17. Retrieved 2 May 2015.
  24. ^ "Cygwin Notables". Retrieved 2023-03-30.
  25. ^ "Cygwin library now available under GNU Lesser General Public License". Archived from the original on 2021-06-16. Retrieved 2021-05-27.
  26. ^ "Installing and Updating Cygwin Packages". Cygwin. Archived from the original on 2020-01-10. Retrieved 2020-01-11.
  27. ^ "Cygwin Package List". Cygwin. Archived from the original on 2016-02-05. Retrieved 2020-01-11.