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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. 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. Cygwin consists of two parts: a dynamic-link library (DLL) as an API compatibility layer providing a substantial part of the POSIX API functionality, and an extensive collection of software tools and applications that provide a Unix-like look and feel. Cygwin was originally developed by Cygnus Solutions, which was later acquired by Red Hat. It is free and open source software, released under the GNU General Public License version 3. Today it is maintained by employees of Red Hat, NetApp and many other volunteers. ==Description== Cygwin consists of a library that implements the POSIX system call API in terms of Win32 system calls, a GNU development toolchain (including GCC and GDB) to allow software development, and a large number of application programs equivalent to those on Unix systems. Programmers have ported many Unix, GNU, BSD and Linux programs and packages to Cygwin, including the X Window System, K Desktop Environment 3, GNOME,〔(【引用サイトリンク】title=Cygwin Ports )〕 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" program, which downloads the necessary program and feature package files from repositories on the Internet. Setup can install, update, and remove programs and their source code packages. A complete installation will take in excess of 36 GB 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: * A Cygwin-specific version of the Unix mount command allows mounting Windows paths as "filesystems" in the Unix file space. Initial mount-points can be configured in /etc/fstab, which has a very similar format as on Unix systems, except that Windows paths appear in place of devices. Filesystems can be mounted in binary mode (by default), or in text mode, which enables automatic conversion between LF and CRLF endings (which only affects programs that open files without explicitly specifying text or binary mode).* Cygwin 1.7 introduced comprehensive support for POSIX locales and many character encodings, whereby the UTF-8 Unicode encoding became the default. Windows file-names and other identifiers, which are encoded as UTF-16, are automatically converted to and from the selected character-encoding. * Windows drive letters map to a special directory, so for example C: appears as /cygdrive/c. The /cygdrive prefix can be changed. Windows network paths of the form \\HOST\SHARE\FILE are mapped to //HOST/SHARE/FILE. Windows paths can also be used directly from Cygwin programs, but many programs do not support them correctly, hence this is discouraged.* Full-featured /dev and /proc file-systems are provided. /proc/registry provides direct filesystem access to the registry.* Cygwin supports POSIX symbolic links, representing them as plain-text files with the system attribute set. Cygwin 1.5 represented them as Windows Explorer shortcuts, but this has been changed for reasons of performance and POSIX correctness. Cygwin also recognises NTFS junction points and symbolic links and treats them as POSIX symbolic links, but it does not create them as their semantics are not fully POSIX-compliant. * 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 SIDs (in the GECOS field), allowing for mapping between Unix and Windows users and groups.* The fork system call for duplicating a process is fully implemented, but it does not map well to the Windows API. For example, the copy-on-write optimization strategy could not be used.〔 (【引用サイトリンク】 url = https://www.cygwin.com/faq.html#faq.api.fork ) 〕〔 (【引用サイトリンク】 url = http://cygwin.com/cygwin-ug-net/highlights.html#ov-hi-process ) 〕〔 〕 As a result, Cygwin's fork is rather slow compared with Linux and others. (That overhead can often be avoided by replacing uses of the fork/exec technique with calls to the spawn functions declared in the Windows-specific process.h header). * The Cygwin DLL contains a console driver that emulates a Unix-style terminal within the Windows console. Cygwin's default user interface is the bash shell running in the Cygwin console. * The DLL also implements pseudo terminal (pty) devices. Cygwin ships with a number of terminal emulators that are based on them, including mintty, rxvt(-unicode), and xterm. These are more compliant with Unix terminal standards and user interface conventions than the Cygwin console, but are less suited for running Windows console programs. * Various utilities are provided for converting between Windows and Unix paths and file formats, for handling line ending (CRLF/LF) issues, for displaying the DLLs that an executable is linked with, etc. * Apart from always being linked against the Cygwin DLL, Cygwin executables are normal Windows executables. This means that Cygwin programs have full access to the Windows API and other Windows libraries, which allows gradual porting of programs from one platform to the other. However, programmers need to be careful about mixing conflicting POSIX and Windows functions. 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 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. It is used to compile Sun Java, OpenOffice.org, LibreOffice, and even web server software like Lighttpd and Hiawatha.〔 (Windows package of Hiawatha Webserver compiled via Cygwin )〕 Red Hat normally licenses the Cygwin library under the GNU General Public License version 3 with an exception to allow linking to any free and open source 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.〔〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cygwin」の詳細全文を読む スポンサード リンク
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