Cygwin

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Cygwin

Running Cygwin under Windows XP
Developer:	Red Hat and others
Latest release:	1.5.22-1 / November 2006
OS:	Windows
Use:	Emulator
License:	GPL
Website:	www.cygwin.com

Cygwin ˈ/sɪgwɪn/ - is a collection of free software tools originally developed by Cygnus Solutions to allow various versions of Microsoft Windows to act somewhat like a Unix system. It aims mainly at porting software that runs on POSIX systems (such as Linux systems, BSD systems, and Unix systems) to run on Windows with little more than a recompilation. Programs ported with Cygwin work best on Windows NT, Windows 2000, Windows XP, and Windows Server 2003, but some may run acceptably on Windows 95 and Windows 98. Cygwin is currently maintained by employees of Red Hat, Netapp and others.

1 Description
2 History
3 See also
4 External links

[edit] Description

Cygwin consists of a library that implements the POSIX system call API in terms of Win32 system calls, a GNU development toolchain (such as GCC and GDB) to allow basic software development tasks, and a large number of application programs equivalent to common programs on the Unix system. At this point, almost all open-source programs on Unix have been ported to Cygwin, including the X Window System, KDE, Gnome, Apache, TeX, and various others. A mechanism has been created for installing inetd, syslogd, sshd, Apache and other daemons as standard Windows services, allowing a Microsoft Windows system to function much like a Unix or Linux server. All of these programs are installed through the standard Cygwin setup program, which downloads the necessary packages from the Internet. The setup program can be rerun as necessary to update programs to their latest versions or add or remove programs. (Various other features are provided by setup, such as the ability to install the source code along with the binaries.)

A large amount of effort has gone into providing interfaces to map between concepts that differ between Unix and Windows. Examples include:

A Cygwin-specific version of Unix mount has been created, which allows arbitrary Windows paths to be mounted as "filesystems" into the Unix file space. Mount information is normally stored in the registry. Filesystems can be mounted as binary (the default) or as text, which performs automatic conversion between LF and CRLF endings. (This only affects programs that call open() or fopen() without specifying text or binary mode. All of the ported Unix programs available through Cygwin setup open files in binary mode if appropriate, and hence data corruption will not occur.) All DOS drives (C:, D:, etc.) are also available under /cygdrive/c, /cygdrive/d, etc. Windows network paths of the form \\HOST\SHARE\FILE are mapped to //HOST/SHARE/FILE.

Full-featured /dev and /proc file systems are provided automatically. /proc/registry provides direct filesystem access to the registry.

Symbolic links are provided, and use .LNK files (Windows shortcuts), with some special Cygwin-specific info in them and the "system" attribute set to speed up processing.

The Solaris API for handling access control lists (ACLs) is supported and maps to the Windows NT ACL system.

Special formats of /etc/passwd and /etc/group are provided that include pointers to the Windows equivalent SID's (in the GECOS field), allowing for mapping between Unix and Windows users and groups.

Various utilities are provided for converting between Windows and Unix file formats, for handling line ending (CRLF/LF) issues, for displaying the DLL's that an executable is linked with, etc.

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. It also provides support for compiling MinGW-compatible executables (that is, executables that do not require Cygwin to be installed to run, or more specifically, executables that don't require Cygwin's CYGWIN1.DLL, which provides the POSIX compatibility layer).

Red Hat normally licenses the Cygwin library under the GNU General Public License with an exception to allow linking to any free software whose license conforms to the Open Source Definition. (Red Hat also sells commercial licenses to those who wish to redistribute programs that use the Cygwin library under proprietary terms.)

One can subscribe to one of many Cygwin-related mailing lists at the Cygwin Mailing Lists page.

[edit] History

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; so at least in theory it should not be difficult to retarget GCC and get a cross compiler producing executables that would run on Windows. This proved to be so in practice, and a prototype came up quickly.

The next step was to attempt to bootstrap the compiler on a Windows system, but this required enough emulation of Unix to let the GNU configure shell script run, which requires a shell like bash, which in turn requires fork and standard I/O. Windows includes similar functionality, so the Cygwin library proper just needs to translate calls and manage private versions of data, such as file descriptors.

By 1996, other engineers had joined in, since 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 workstation to build, say, a Windows-x-MIPS cross-compiler, which was faster than using the PC of the time. Starting around 1998, Cygnus also began offering the Cygwin package as a product of interest in its own right.

[edit] See also

Free software Portal

Cygwin/X is a free X11 implementation running on top of Cygwin.
MinGW is a free port of the GNU development tools to Windows.
DJGPP is a similar suite for DOS/Windows.
Services for UNIX is a Microsoft product with similar capabilities to Cygwin; it has the advantage of speed, although it is not available for Windows XP Home, or older non NT-based versions of Windows.
The UWIN package allows UNIX applications to be built and run on Windows XP/2000/NT/ME/98/95.
coLinux uses a different approach to running Linux programs in Windows: it runs Linux itself to host them.
KDE on Cygwin
MKS Toolkit