116 lines
5.5 KiB
Plaintext
116 lines
5.5 KiB
Plaintext
<chapter id="overview"><title>Cygwin Overview</title>
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<sect1 id="what-is-it"><title>What is it?</title>
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<para>
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Cygwin is a Linux-like environment for Windows. It consists of a DLL
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(<filename>cygwin1.dll</filename>), which acts as an emulation layer
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providing substantial <ulink
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url="http://www.pasc.org/#POSIX">POSIX</ulink> (Portable Operating
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System Interface) system call functionality, and a collection of tools,
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which provide a Linux look and feel. The Cygwin DLL works with all x86
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versions of Windows since Windows 95. The API follows the <ulink
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url="http://www.opengroup.org/onlinepubs/009695399/nfindex.html">Single
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Unix Specification</ulink> as much as possible, and then Linux practice.
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Two other major differences between Cygwin and Linux are the C library
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(<literal>newlib</literal> instead of <literal>glibc</literal>) and
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default <command>/bin/sh</command>, which is <command>ash</command> on
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Cygwin but <command>bash</command> on most Linux distributions.
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</para>
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<para>
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With Cygwin installed, users have access to many standard UNIX
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utilities. They can be used from one of the provided shells such
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as <command>bash</command> or from the Windows Command Prompt.
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Additionally, programmers may write Win32 console or GUI applications
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that make use of the standard Microsoft Win32 API and/or the Cygwin API.
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As a result, it is possible to easily port many significant UNIX
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programs without the need for extensive changes to the source code.
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This includes configuring and building most of the available GNU
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software (including the development tools included with the Cygwin
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distribution).
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</para>
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</sect1>
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DOCTOOL-INSERT-ov-ex-win
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DOCTOOL-INSERT-ov-ex-unix
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<sect1 id="are-free"><title>Are the Cygwin tools free software?</title>
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<para>Yes. Parts are <ulink url="http://www.gnu.org/">GNU</ulink> software
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(<command>gcc</command>, <command>gas</command>, <command>ld</command>, etc.),
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parts are covered by the standard
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<ulink url="http://www.x.org/Downloads_terms.html">X11 license</ulink>,
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some of it is public domain, some of it was written by Red Hat and placed under
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the <ulink url="http://www.gnu.org/licenses/gpl.html">GNU General Public
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License</ulink> (GPL). None of it is shareware. You don't have to pay anyone to
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use it but you should be sure to read the copyright section of the FAQ for more
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information on how the GNU GPL may affect your use of these
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tools. If you intend to port a proprietary application using the Cygwin
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library, you may want the Cygwin proprietary-use license.
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For more information about the proprietary-use license, please go to
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<ulink url="http://www.redhat.com/software/tools/cygwin/">http://www.redhat.com/software/tools/cygwin/
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</ulink>. Customers of the native Win32 GNUPro should feel free to submit bug
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reports and ask questions through the normal channels. All other
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questions should be sent to the project mailing list
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<email>cygwin@cygwin.com</email>.</para>
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</sect1>
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<sect1 id="brief-history"><title>A brief history of the Cygwin project</title>
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<note>
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<para>
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A more complete historical look Cygwin is Geoffrey J. Noer's 1998 paper,
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"Cygwin32: A Free Win32 Porting Layer for UNIX® Applications" which can be
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found at the <ulink
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url="http://www.usenix.org/publications/library/proceedings/usenix-nt98/technical.html">
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2nd USENIX Windows NT Symposium Online Proceedings</ulink>.
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</para>
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</note>
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<para>
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Cygwin began development in 1995 at Cygnus Solutions (now part of Red Hat
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Software). The first thing done was to enhance the development tools
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(<command>gcc</command>, <command>gdb</command>, <command>gas</command>,
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etc.) so that they could generate and interpret Win32 native
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object files.
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The next task was to port the tools to Win NT/9x. We could have
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done this by rewriting large portions of the source to work within the
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context of the Win32 API. But this would have meant spending a huge
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amount of time on each and every tool. Instead, we took a
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substantially different approach by writing a shared library
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(the Cygwin DLL) that adds the necessary UNIX-like functionality
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missing from the Win32 API (<function>fork</function>,
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<function>spawn</function>, <function>signals</function>,
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<function>select</function>, <function>sockets</function>, etc.). We call this
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new interface the Cygwin API. Once written, it was possible to build working
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Win32 tools using UNIX-hosted cross-compilers, linking against this
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library.</para>
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<para>From this point, we pursued the goal of producing native tools
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capable of rebuilding themselves under Windows 9x and NT (this is
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often called self-hosting). Since neither OS ships with standard UNIX
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user tools (fileutils, textutils, bash, etc...), we had to get the GNU
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equivalents working with the Cygwin API. Most of these tools were
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previously only built natively so we had to modify their configure
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scripts to be compatible with cross-compilation. Other than the
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configuration changes, very few source-level changes had to be
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made. Running bash with the development tools and user tools in place,
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Windows 9x and NT look like a flavor of UNIX from the perspective of
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the GNU configure mechanism. Self hosting was achieved as of the beta
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17.1 release in October 1996.</para>
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<para>
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The entire Cygwin toolset was available as a monolithic install. In
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April 2000, the project announced a
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<ulink url="http://www.cygwin.com/ml/cygwin/2000-04/msg00269.html">
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New Cygwin Net Release</ulink> which provided the native Win32 program
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<command>setup.exe</command> to install and upgrade each package
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separately. Since then, the Cygwin DLL and <command>setup.exe</command>
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have seen continuous development.
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</para>
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</sect1>
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DOCTOOL-INSERT-highlights
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</chapter>
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