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From sl...@apache.org
Subject cvs commit: httpd-docs-1.3/htdocs/manual urlmapping.html index.html.en
Date Sat, 17 Feb 2001 05:22:46 GMT
slive       01/02/16 21:22:45

  Modified:    htdocs/manual index.html.en
  Added:       htdocs/manual urlmapping.html
  Log:
  Add a "unifying" document about mapping URLs to filesystem locations.
  
  Suggestions for improvements welcome.
  
  Revision  Changes    Path
  1.49      +2 -0      httpd-docs-1.3/htdocs/manual/index.html.en
  
  Index: index.html.en
  ===================================================================
  RCS file: /home/cvs/httpd-docs-1.3/htdocs/manual/index.html.en,v
  retrieving revision 1.48
  retrieving revision 1.49
  diff -u -d -b -u -r1.48 -r1.49
  --- index.html.en	2001/01/23 23:18:25	1.48
  +++ index.html.en	2001/02/17 05:22:44	1.49
  @@ -135,6 +135,8 @@
   </td></tr><tr><td>
   <a href="server-wide.html">Server-Wide Configuration</A>
   </td></tr><tr><td>
  +<A HREF="urlmapping.html">Mapping URLs to the Filesystem</A>
  +</td></tr><tr><td>
   <A HREF="vhosts/index.html">Virtual Hosts</A>
   </td></tr><tr><td>
   <a href="howto/ssi.html">Server Side Includes</a>
  
  
  
  1.1                  httpd-docs-1.3/htdocs/manual/urlmapping.html
  
  Index: urlmapping.html
  ===================================================================
  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
  <HTML>
  <HEAD>
  <TITLE>Mapping URLs to Filesystem Locations - Apache HTTP Server</TITLE>
  </HEAD>
  
  <!-- Background white, links blue (unvisited), navy (visited), red (active) -->
  <BODY
   BGCOLOR="#FFFFFF"
   TEXT="#000000"
   LINK="#0000FF"
   VLINK="#000080"
   ALINK="#FF0000"
  >
  <!--#include virtual="header.html" -->
  <h1 align="center">Mapping URLs to Filesystem Locations</h1>
  
  <p>This document explains the method in which Apache determines
  what filesystem location to serve a file from based on the
  URL of a request.</p>
  
  <ul>
  <li><a href="#documentroot">DocumentRoot</a></li>
  <li><a href="#outside">Files Outside the DocumentRoot</a></li>
  <li><a href="#user">User Directories</a></li>
  <li><a href="#redirect">URL Redirection</a></li>
  <li><a href="#rewrite">Rewrite Engine</a></li>
  <li><a href="#notfound">File Not Found</a></li>
  </ul>
  
  <hr>
  
  <table border="1">
  <tr><td valign="top">
  <strong>Related Modules</strong><br><br>
  
  <a href="mod/mod_alias.html">mod_alias</a><br>
  <a href="mod/mod_rewrite.html">mod_rewrite</a><br>
  <a href="mod/mod_userdir.html">mod_userdir</a><br>
  <a href="mod/mod_speling.html">mod_speling</a><br>
  <a href="mod/mod_vhost_alias.html">mod_vhost_alias</a><br>
  
  </td><td valign="top">
  <strong>Related Directives</strong><br><br>
  
  <A HREF="mod/mod_alias.html#alias">Alias</A><br>
  <A HREF="mod/mod_alias.html#aliasmatch">AliasMatch</A><br>
  <A HREF="mod/mod_speling.html#checkspelling">CheckSpelling</A><br>
  <A HREF="mod/core.html#documentroot">DocumentRoot</A><br>
  <A HREF="mod/core.html#errordocument">ErrorDocument</A><br>
  <a href="mod/core.html#options">Options</a><br>
  <A HREF="mod/mod_alias.html#redirect">Redirect</A><br>
  <A HREF="mod/mod_alias.html#redirectmatch">RedirectMatch</A><br>
  <A HREF="mod/mod_rewrite.html#RewriteCond">RewriteCond</A><br>
  <A HREF="mod/mod_rewrite.html#RewriteRule">RewriteRule</A><br>
  <A HREF="mod/mod_alias.html#scriptalias">ScriptAlias</A><br>
  <A HREF="mod/mod_alias.html#scriptaliasmatch">ScriptAliasMatch</A><br>
  <A HREF="mod/mod_userdir.html#userdir">UserDir</A><br>
  
  </td></tr></table>
  
  <h2><a name="documentroot">DocumentRoot</a></h2>
  
  <p>In deciding what file to serve for a given request, Apache's
  default behavior is to take the URL-Path for the request (the part of
  the URL following the first single slash) and add it to the end of the
  <a href="mod/core.html#documentroot">DocumentRoot</a> specified in
  your configuration files.  Therefore, the files and directories
  underneath the <code>DocumentRoot</code> make up the basic document
  tree which will be visible from the web.</p>
  
  <p>Apache is also capable of <a href="vhosts/">Virtual Hosting</a>,
  where the server receives requests for more than one host.  In this
  case, a different <code>DocumentRoot</code> can be specified for each
  virtual host, or alternatively, the directives provided by the module
  <a href="mod/mod_vhost_alias.html">mod_vhost_alias</a> can be used to
  dynamically determine the appropriate place from which to serve
  content based on the requested IP address or hostname.</p>
  
  <h2><a name="outside">Files Outside the DocumentRoot</a></h2>
  
  <p>There are frequently circumstances where it is necessary to allow
  web access to parts of the filesystem which are not strictly
  underneath the <a href="mod/core.html#documentroot">DocumentRoot</a>.
  Apache offers several different ways to accomplish this.  On Unix
  systems, symbolic links can be used to bring other parts of the
  filesystem under the <code>DocumentRoot</code>.  For security reasons,
  symbolic links will only be followed if the <a
  href="mod/core.html#options">Options</a> setting for the relevant
  directory includes <code>FollowSymLinks</code> or
  <code>SymLinksIfOwnerMatch</code>.</p>
  
  <p>Alternatively, the <a href="mod/mod_alias.html#alias">Alias</a>
  directive can be used to map any part of the filesystem into the web
  space.  For example, with</p>
  
  <blockquote><code>Alias /docs /var/web/
  </blockquote></code> 
  
  <p>the URL <code>http://www.example.com/docs/dir/file.html</code> will
  be served from <code>/var/web/dir/file.html</code>.  The <a
  href="mod/mod_alias.html#scriptalias">ScriptAlias</a> directive works
  the same way, with the additional effect that all content located at
  the target path is treated as CGI scripts.</p>
  
  <p>For situations where additional flexibility is required, the <a
  href="mod/mod_alias.html#aliasmatch">AliasMatch</a> and <a
  href="mod/mod_alias.html#scriptaliasmatch">ScriptAliasMatch</a>
  directives can do powerful <a
  href="misc/FAQ.html#regex">regular-expression</a> based matching and
  substitution.  For example,</p>
  
  <blockquote><code> ScriptAliasMatch ^/~([^/]*)/cgi-bin/(.*)
  /home/$1/cgi-bin/$2 </code></blockquote>
  
  <p>will map a request to
  <code>http://example.com/~user/cgi-bin/script.cgi</code> to the path
  <code>/home/user/cgi-bin/script.cgi</code> and will treat the
  resulting file as a CGI script.</p>
  
  <h2><a name="user">User Directories</a></h2>
  
  <p>Traditionally on Unix systems, the home directory of a particular
  <em>user</em> can be referred to as <code>~user/</code>.  The module
  <a href="mod/mod_userdir.html">mod_userdir</a> extends this idea to
  the web by allowing files under each user's home directory to be
  accessed using URLs such as the following.</p>
  
  <blockquote><code>http://www.example.com/~user/file.html</code></blockquote>
  
  <p>For security reasons, it would be inappropriate to give direct
  access to a user's home directory from the web.  Therefore, the <a
  href="mod/mod_userdir.html#userdir">UserDir</a> directive is used to
  specify a directory underneath the user's home directory where web
  files will be located.  Using the default setting of <code>Userdir
  public_html</code>, the above URL would look for a file at a directory
  like <code>/home/user/public_html/file.html</code> where the
  </code>/home/user/</code> is the user's home directory as specified in
  <code>/etc/passwd</code>.</p>
  
  <p>There are also several other forms of the <code>Userdir</code>
  directive which can be used on systems where <code>/etc/passwd</code>
  cannot be used to find the location of the home directory.</p>
  
  <p>Some people find the "~" symbol (which is often encoded on the web
  as <code>%7e</code>) to be awkward and prefer to use an alternate
  string to represent user directories.  This functionality is not
  supported by mod_userdir.  However, if users' home directories are
  structured in a regular way, then it is possible to use the <a
  href="mod/mod_alias.html#aliasmatch">AliasMatch</a> directive to
  achieve the desired effect.  For example, to make
  <code>http://www.example.com/upages/user/file.html</code> map to
  <code>/home/user/public_html/file.html</code>, the following
  <code>AliasMatch</code> directive can be used.</p>
  
  <blockquote><code>
  AliasMatch  ^/upages/([^/]*)/?(.*) /home/$1/public_html/$2 
  </code></blockquote>
  
  <h2><a name="redirect">URL Redirection</a></h2>
  
  <p>The configuration directives discussed in the above sections are
  used to tell Apache to get content from a specific place in the
  filesystem and return it to the client.  Sometimes, it is desirable
  instead to inform the client that the content being requested is
  located at an different URL, and instruct the client to make a new
  request with the new URL.  This is referred to as <em>redirection</em>
  and is implemented by the <a
  href="mod/mod_alias.html#redirect">Redirect</a> directive.  For example,
  if the contents of the directory <code>/foo/</code> under the
  <code>DocumentRoot</code> have been moved to the new directory
  <code>/bar/</code>, clients can instructed to request the content at
  the new location as follows.</p>
  
  <blockquote><code>Redirect permanent
  /foo/ http://www.example.com/bar/</code></blockquote>
  
  <p>This will redirect any URL-Path starting in <code>/foo/</code> to
  the same URL path on the <code>www.example.com</code> server with
  <code>/bar/</code> substituted for <code>/foo/</code>.  Note that
  clients can be redirected to any server, not only the origin
  server.</p>
  
  <p>Apache also provides a <a
  href="mod/mod_alias.html#redirectmatch">RedirectMatch</a> directive
  which can be used for more complicated rewriting problems.  For
  example, to redirect requests for the site home page to a different
  site, but leave all other requests alone, the following configuration
  can be used.</p>
  
  <blockquote><code>
  RedirectMatch permanent ^/$ http://www.example.com/startpage.html
  </code></blockquote>
  
  <p>Alternatively, to temporarily redirect all pages on a site to one
  particular page, the following configuration is useful.</p>
  
  <blockquote><code>
  RedirectMatch temp .* http://www.example.com/startpage.html
  </code></blockquote>
  
  <h2><a name="rewrite">Rewriting Engine</a></h2>
  
  <p>When even more powerful substitution is required, the rewriting
  engine provided by <a href="mod/mod_rewrite.html">mod_rewrite</a> can
  be useful.  The directives provided by this module can use
  characteristics of the request such as browser type or source IP
  address in deciding from where to serve content.  In addition,
  mod_rewrite can use external database files or programs to determine
  how to handle a request.  Many practical examples employing
  mod_rewrite are discussed in the <a href="misc/rewriteguide.html">URL
  Rewriting Guide</a>.</p>
  
  <h2><a name="notfound">File Not Found</a></h2>
  
  <p>Inevitably, URLs will be requested for which no matching file can
  be found in the filesystem.  This can happen for several reasons.  In
  some cases, it can be a result of moving documents from one location
  to another.  In this case, it is best to use <a href="#redirect">URL
  redirection</a> to inform clients of the new location of the resource.
  In this way, you can assure that old bookmarks and links will continue
  to work, even though the resource is at a new location.</p>
  
  <p>Another common cause of "File Not Found" errors is accidental
  mistyping of URLs, either directly in the browser, or in HTML links.
  Apache provides the module <a href="mod/mod_speling">mod_speling</a>
  (sic) to help with this problem.  When this module is activated, it
  will intercept "File Not Found" errors and look for a resource with a
  similar filename.  If one such file is found, mod_speling will send an
  HTTP redirect to the client informing it of the correct location.  If
  several "close" files are found, a list of available alternatives will
  be presented to the client.</p>
  
  <p>An especially useful feature of mod_speling, is that it will
  compare filenames without respect to case.  This can be useful for
  systems where users are unaware of the case-sensitive nature of URLs
  and the unix filesystem.  However, using mod_speling for anything more
  than the occasional URL correction can lead to additional load on the
  server, since each "incorrect" request is followed by a URL
  redirection and a new request from the client.</p>
  
  <p>If all attempts to locate the content fail, Apache returns an error
  page with HTTP status code 404 (file not found).  The appearance of
  this page is controlled with the <a
  href="mod/core.html#errordocument">ErrorDocument</a> directive and can
  be customized in a flexible manner as discussed in the <a
  href="custom-error.html">Custom error responses</a> and <a
  href="misc/custom_errordocs.html">International Server Error
  Responses</a> documents.</p>
  
  <!--#include virtual="footer.html" -->
  </BODY>
  </HTML>
  
  
  

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