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in particular, the non-english files, to make sure I did not screw anything up. They look fine to me. git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91112 13f79535-47bb-0310-9956-ffa450edef68
297 lines
12 KiB
HTML
Executable File
297 lines
12 KiB
HTML
Executable File
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta name="generator" content="HTML Tidy, see www.w3.org" />
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<title>Mapping URLs to Filesystem Locations - Apache HTTP
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Server</title>
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</head>
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<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
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<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
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vlink="#000080" alink="#FF0000">
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<!--#include virtual="header.html" -->
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<h1 align="center">Mapping URLs to Filesystem Locations</h1>
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<p>This document explains how Apache uses the URL of a request
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to determine the filesystem location from which to serve a
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file.</p>
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<ul>
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<li><a href="#documentroot">DocumentRoot</a></li>
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<li><a href="#outside">Files Outside the
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DocumentRoot</a></li>
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<li><a href="#user">User Directories</a></li>
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<li><a href="#redirect">URL Redirection</a></li>
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<li><a href="#rewrite">Rewrite Engine</a></li>
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<li><a href="#notfound">File Not Found</a></li>
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</ul>
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<hr />
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<table border="1">
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<tr>
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<td valign="top"><strong>Related Modules</strong><br />
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<br />
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<a href="mod/mod_alias.html">mod_alias</a><br />
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<a href="mod/mod_rewrite.html">mod_rewrite</a><br />
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<a href="mod/mod_userdir.html">mod_userdir</a><br />
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<a href="mod/mod_speling.html">mod_speling</a><br />
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<a
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href="mod/mod_vhost_alias.html">mod_vhost_alias</a><br />
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</td>
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<td valign="top"><strong>Related Directives</strong><br />
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<br />
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<a href="mod/mod_alias.html#alias">Alias</a><br />
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<a
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href="mod/mod_alias.html#aliasmatch">AliasMatch</a><br />
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<a
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href="mod/mod_speling.html#checkspelling">CheckSpelling</a><br />
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<a
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href="mod/core.html#documentroot">DocumentRoot</a><br />
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<a
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href="mod/core.html#errordocument">ErrorDocument</a><br />
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<a href="mod/core.html#options">Options</a><br />
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<a href="mod/mod_alias.html#redirect">Redirect</a><br />
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<a
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href="mod/mod_alias.html#redirectmatch">RedirectMatch</a><br />
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<a
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href="mod/mod_rewrite.html#RewriteCond">RewriteCond</a><br />
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<a
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href="mod/mod_rewrite.html#RewriteRule">RewriteRule</a><br />
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<a
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href="mod/mod_alias.html#scriptalias">ScriptAlias</a><br />
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<a
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href="mod/mod_alias.html#scriptaliasmatch">ScriptAliasMatch</a><br />
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<a href="mod/mod_userdir.html#userdir">UserDir</a><br />
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</td>
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</tr>
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</table>
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<h2><a id="documentroot"
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name="documentroot">DocumentRoot</a></h2>
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<p>In deciding what file to serve for a given request, Apache's
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default behavior is to take the URL-Path for the request (the
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part of the URL following the hostname and port) and add it to
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the end of the <a
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href="mod/core.html#documentroot">DocumentRoot</a> specified in
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your configuration files. Therefore, the files and directories
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underneath the <code>DocumentRoot</code> make up the basic
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document tree which will be visible from the web.</p>
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<p>Apache is also capable of <a href="vhosts/">Virtual
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Hosting</a>, where the server receives requests for more than
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one host. In this case, a different <code>DocumentRoot</code>
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can be specified for each virtual host, or alternatively, the
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directives provided by the module <a
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href="mod/mod_vhost_alias.html">mod_vhost_alias</a> can be used
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to dynamically determine the appropriate place from which to
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serve content based on the requested IP address or
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hostname.</p>
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<h2><a id="outside" name="outside">Files Outside the
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DocumentRoot</a></h2>
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<p>There are frequently circumstances where it is necessary to
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allow web access to parts of the filesystem that are not
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strictly underneath the <a
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href="mod/core.html#documentroot">DocumentRoot</a>. Apache
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offers several different ways to accomplish this. On Unix
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systems, symbolic links can bring other parts of the filesystem
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under the <code>DocumentRoot</code>. For security reasons,
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Apache will follow symbolic links only if the <a
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href="mod/core.html#options">Options</a> setting for the
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relevant directory includes <code>FollowSymLinks</code> or
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<code>SymLinksIfOwnerMatch</code>.</p>
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<p>Alternatively, the <a
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href="mod/mod_alias.html#alias">Alias</a> directive will map
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any part of the filesystem into the web space. For example,
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with</p>
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<blockquote>
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<code>Alias /docs /var/web/</code>
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</blockquote>
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<p>the URL
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<code>http://www.example.com/docs/dir/file.html</code> will be
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served from <code>/var/web/dir/file.html</code>. The <a
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href="mod/mod_alias.html#scriptalias">ScriptAlias</a> directive
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works the same way, with the additional effect that all content
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located at the target path is treated as CGI scripts.</p>
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<p>For situations where you require additional flexibility, you
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can use the <a
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href="mod/mod_alias.html#aliasmatch">AliasMatch</a> and <a
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href="mod/mod_alias.html#scriptaliasmatch">ScriptAliasMatch</a>
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directives to do powerful regular-expression based matching and
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substitution. For example,</p>
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<blockquote>
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<code>ScriptAliasMatch ^/~([^/]*)/cgi-bin/(.*)
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/home/$1/cgi-bin/$2</code>
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</blockquote>
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<p>will map a request to
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<code>http://example.com/~user/cgi-bin/script.cgi</code> to the
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path <code>/home/user/cgi-bin/script.cgi</code> and will treat
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the resulting file as a CGI script.</p>
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<h2><a id="user" name="user">User Directories</a></h2>
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<p>Traditionally on Unix systems, the home directory of a
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particular <em>user</em> can be referred to as
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<code>~user/</code>. The module <a
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href="mod/mod_userdir.html">mod_userdir</a> extends this idea
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to the web by allowing files under each user's home directory
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to be accessed using URLs such as the following.</p>
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<blockquote>
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<code>http://www.example.com/~user/file.html</code>
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</blockquote>
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<p>For security reasons, it is inappropriate to give direct
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access to a user's home directory from the web. Therefore, the
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<a href="mod/mod_userdir.html#userdir">UserDir</a> directive
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specifies a directory underneath the user's home directory
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where web files are located. Using the default setting of
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<code>Userdir public_html</code>, the above URL maps to a file
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at a directory like
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<code>/home/user/public_html/file.html</code> where
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<code>/home/user/</code> is the user's home directory as
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specified in <code>/etc/passwd</code>.</p>
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<p>There are also several other forms of the
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<code>Userdir</code> directive which you can use on systems
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where <code>/etc/passwd</code> does not contain the location of
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the home directory.</p>
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<p>Some people find the "~" symbol (which is often encoded on
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the web as <code>%7e</code>) to be awkward and prefer to use an
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alternate string to represent user directories. This
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functionality is not supported by mod_userdir. However, if
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users' home directories are structured in a regular way, then
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it is possible to use the <a
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href="mod/mod_alias.html#aliasmatch">AliasMatch</a> directive
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to achieve the desired effect. For example, to make
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<code>http://www.example.com/upages/user/file.html</code> map
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to <code>/home/user/public_html/file.html</code>, use the
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following <code>AliasMatch</code> directive:</p>
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<blockquote>
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<code>AliasMatch ^/upages/([^/]*)/?(.*)
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/home/$1/public_html/$2</code>
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</blockquote>
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<h2><a id="redirect" name="redirect">URL Redirection</a></h2>
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<p>The configuration directives discussed in the above sections
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tell Apache to get content from a specific place in the
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filesystem and return it to the client. Sometimes, it is
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desirable instead to inform the client that the requested
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content is located at a different URL, and instruct the client
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to make a new request with the new URL. This is called
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<em>redirection</em> and is implemented by the <a
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href="mod/mod_alias.html#redirect">Redirect</a> directive. For
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example, if the contents of the directory <code>/foo/</code>
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under the <code>DocumentRoot</code> are moved to the new
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directory <code>/bar/</code>, you can instruct clients to
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request the content at the new location as follows:</p>
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<blockquote>
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<code>Redirect permanent /foo/
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http://www.example.com/bar/</code>
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</blockquote>
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<p>This will redirect any URL-Path starting in
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<code>/foo/</code> to the same URL path on the
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<code>www.example.com</code> server with <code>/bar/</code>
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substituted for <code>/foo/</code>. You can redirect clients to
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any server, not only the origin server.</p>
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<p>Apache also provides a <a
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href="mod/mod_alias.html#redirectmatch">RedirectMatch</a>
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directive for more complicated rewriting problems. For example,
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to redirect requests for the site home page to a different
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site, but leave all other requests alone, use the following
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configuration:</p>
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<blockquote>
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<code>RedirectMatch permanent ^/$
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http://www.example.com/startpage.html</code>
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</blockquote>
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<p>Alternatively, to temporarily redirect all pages on a site
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to one particular page, use the following:</p>
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<blockquote>
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<code>RedirectMatch temp .*
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http://www.example.com/startpage.html</code>
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</blockquote>
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<h2><a id="rewrite" name="rewrite">Rewriting Engine</a></h2>
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<p>When even more powerful substitution is required, the
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rewriting engine provided by <a
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href="mod/mod_rewrite.html">mod_rewrite</a> can be useful. The
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directives provided by this module use characteristics of the
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request such as browser type or source IP address in deciding
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from where to serve content. In addition, mod_rewrite can use
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external database files or programs to determine how to handle
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a request. Many practical examples employing mod_rewrite are
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discussed in the <a href="misc/rewriteguide.html">URL Rewriting
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Guide</a>.</p>
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<h2><a id="notfound" name="notfound">File Not Found</a></h2>
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<p>Inevitably, URLs will be requested for which no matching
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file can be found in the filesystem. This can happen for
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several reasons. In some cases, it can be a result of moving
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documents from one location to another. In this case, it is
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best to use <a href="#redirect">URL redirection</a> to inform
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clients of the new location of the resource. In this way, you
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can assure that old bookmarks and links will continue to work,
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even though the resource is at a new location.</p>
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<p>Another common cause of "File Not Found" errors is
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accidental mistyping of URLs, either directly in the browser,
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or in HTML links. Apache provides the module <a
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href="mod/mod_speling.html">mod_speling</a> (sic) to help with
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this problem. When this module is activated, it will intercept
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"File Not Found" errors and look for a resource with a similar
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filename. If one such file is found, mod_speling will send an
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HTTP redirect to the client informing it of the correct
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location. If several "close" files are found, a list of
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available alternatives will be presented to the client.</p>
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<p>An especially useful feature of mod_speling, is that it will
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compare filenames without respect to case. This can help
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systems where users are unaware of the case-sensitive nature of
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URLs and the unix filesystem. But using mod_speling for
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anything more than the occasional URL correction can place
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additional load on the server, since each "incorrect" request
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is followed by a URL redirection and a new request from the
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client.</p>
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<p>If all attempts to locate the content fail, Apache returns
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an error page with HTTP status code 404 (file not found). The
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appearance of this page is controlled with the <a
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href="mod/core.html#errordocument">ErrorDocument</a> directive
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and can be customized in a flexible manner as discussed in the
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<a href="custom-error.html">Custom error responses</a> and <a
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href="misc/custom_errordocs.html">International Server Error
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Responses</a> documents.</p>
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<!--#include virtual="footer.html" -->
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</body>
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</html>
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