# About Cygwin

What is it?

The Cygwin tools are ports of the popular GNU development tools for Microsoft Windows. They run thanks to the Cygwin library which provides the POSIX system calls and environment these programs expect.

With these tools installed, it is possible to write Windows console or GUI applications that make use of significant parts of the POSIX API. As a result, it is possible to easily port many Unix programs without the need for extensive changes to the source code. This includes configuring and building most of the available GNU software (including the packages included with the Cygwin development tools themselves) as well as lots of BSD tools and packages (including OpenSSH). Even if the development tools are of little to no use to you, you may have interest in the many standard POSIX utilities provided with the package. They can be used from one of the provided Unix shells like bash, tcsh or zsh, as well as from the standard Windows command shell if you have to for some sad reason.

What versions of Windows are supported?

Cygwin can be expected to run on all modern versions of Windows. This includes, as of the time of writing this, Windows XP SP3, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, Windows Server 2012, Windows 8. The 32 bit version also runs in the WOW64 32 bit environment on released 64 bit versions of Windows (XP/2003/Vista/2008/7/2008 R2/8/2012). Since Cygwin is a community-supported free software project, patches to provide support for other versions would be thoughtfully considered. Paid support contracts or enhancements are available through Red Hat. For information about getting a Red Hat support contract, see .

Keep in mind that Cygwin can only do as much as the underlying OS supports. Because of this, Cygwin will behave differently, and exhibit different limitations, on the various versions of Windows.

Where can I get it?

The home page for the Cygwin project is http://cygwin.com/. There you should find everything you need for Cygwin, including links for download and setup, a current list of mirror sites, a User's Guide, an API Reference, mailing lists and archives, and additional ported software.

You can find documentation for the individual GNU tools typically as man pages or info pages as part of the Cygwin net distribution. Additionally you can get the latest docs at . (You should read GNU manuals from a local mirror. Check for a list of them.)

Is it free software?

Yes. Parts are GNU software (gcc, gas, ld, etc...), parts are covered by the standard X11 license, some of it is public domain, some of it was written by Red Hat (or the former Cygnus Solutions) and placed under the GPL. None of it is shareware. You don't have to pay anyone to use it but you should be sure to read the copyright section of the FAQ for more information on how the GNU General Public License may affect your use of these tools.

In particular, if you intend to port a proprietary (non-GPL'd) application using Cygwin, you will need the proprietary-use license for the Cygwin library. This is available for purchase from Red Hat; please visit for more information. All other questions should be sent to the public project mailing list cygwin@cygwin.com.

Note that when we say "free" we mean freedom, not price. The goal of such freedom is that the people who use a given piece of software should be able to change it to fit their needs, learn from it, share it with their friends, etc. The Cygwin license allows you those freedoms, so it is free software.

What version of Cygwin is this, anyway?

To find the version of the Cygwin DLL installed, you can use `uname` as on Linux or `cygcheck`. Refer to each command's `--help` output and the Cygwin User's Guide for more information.

If you are looking for the version number for the whole Cygwin release, there is none. Each package in the Cygwin release has its own version. The packages in Cygwin are continually improving, thanks to the efforts of net volunteers who maintain the Cygwin binary ports. Each package has its own version numbers and its own release process.

So, how do you get the most up-to-date version of Cygwin? Easy. Just download the Cygwin Setup program by following the instructions here. The setup program will handle the task of updating the packages on your system to the latest version. For more information about using Cygwin's `setup.exe`, see Setting Up Cygwin in the Cygwin User's Guide.

Who's behind the project?

(Please note that if you have cygwin-specific questions, all of these people will appreciate it if you use the cygwin mailing lists rather than sending personal email.)

Christopher Faylor (cgf) is one of the project leads. Chris works for Netapp but all of his Cygwin activities occur on his own time. He is most notably responsible for the support of signal handling and fork/exec in Cygwin. He also administers the site which hosts the Cygwin project.

Corinna Vinschen (corinna) is the other project lead. Corinna is a senior Red Hat engineer. Corinna is responsible for such important subsystems as security and networking and has recently added support to Cygwin for wide characters, increased path length, IPv6, advisory file locking and more.

Yaakov Selkowitz is the Cygwin/X coordinator. Jon Turney serves on the Cygwin/X team as a developer.

The Cygwin setup project is currently maintained by a group of people, most notably, Brian Dessent (brian) and Dave Korn (dave.korn).

Please note that all of us working on Cygwin try to be as responsive as possible and deal with patches and questions as we get them, but realistically we don't have time to answer all of the email that is sent to the main mailing list. Making Net releases of the Win32 tools and helping people on the Net out is not our primary job function, so some email will have to go unanswered.

Many thanks to everyone using the tools for their many contributions in the form of advice, bug reports, and code fixes. Keep them coming!