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1bf05b9838
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
183 lines
6.3 KiB
Plaintext
183 lines
6.3 KiB
Plaintext
<!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>Custom error responses</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">Custom error responses</h1>
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<dl>
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<dt>Purpose</dt>
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<dd>
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Additional functionality. Allows webmasters to configure
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the response of Apache to some error or problem.
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<p>Customizable responses can be defined to be activated in
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the event of a server detected error or problem.</p>
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<p>e.g. if a script crashes and produces a "500 Server
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Error" response, then this response can be replaced with
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either some friendlier text or by a redirection to another
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URL (local or external).</p>
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</dd>
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<dt>Old behavior</dt>
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<dd>NCSA httpd 1.3 would return some boring old error/problem
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message which would often be meaningless to the user, and
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would provide no means of logging the symptoms which caused
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it.<br />
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</dd>
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<dt>New behavior</dt>
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<dd>
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The server can be asked to;
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<ol>
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<li>Display some other text, instead of the NCSA hard
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coded messages, or</li>
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<li>redirect to a local URL, or</li>
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<li>redirect to an external URL.</li>
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</ol>
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<p>Redirecting to another URL can be useful, but only if
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some information can be passed which can then be used to
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explain and/or log the error/problem more clearly.</p>
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<p>To achieve this, Apache will define new CGI-like
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environment variables, <em>e.g.</em></p>
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<blockquote>
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<code>REDIRECT_HTTP_ACCEPT=*/*, image/gif,
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image/x-xbitmap, image/jpeg<br />
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REDIRECT_HTTP_USER_AGENT=Mozilla/1.1b2 (X11; I; HP-UX
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A.09.05 9000/712)<br />
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REDIRECT_PATH=.:/bin:/usr/local/bin:/etc<br />
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REDIRECT_QUERY_STRING=<br />
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REDIRECT_REMOTE_ADDR=121.345.78.123<br />
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REDIRECT_REMOTE_HOST=ooh.ahhh.com<br />
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REDIRECT_SERVER_NAME=crash.bang.edu<br />
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REDIRECT_SERVER_PORT=80<br />
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REDIRECT_SERVER_SOFTWARE=Apache/0.8.15<br />
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REDIRECT_URL=/cgi-bin/buggy.pl<br />
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</code>
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</blockquote>
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<p>note the <code>REDIRECT_</code> prefix.</p>
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<p>At least <code>REDIRECT_URL</code> and
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<code>REDIRECT_QUERY_STRING</code> will be passed to the
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new URL (assuming it's a cgi-script or a cgi-include). The
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other variables will exist only if they existed prior to
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the error/problem. <strong>None</strong> of these will be
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set if your ErrorDocument is an <em>external</em> redirect
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(<em>i.e.</em>, anything starting with a scheme name like
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<code>http:</code>, even if it refers to the same host as
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the server).</p>
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</dd>
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<dt>Configuration</dt>
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<dd>
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Use of "ErrorDocument" is enabled for .htaccess files when
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the <a href="mod/core.html#allowoverride">"FileInfo"
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override</a> is allowed.
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<p>Here are some examples...</p>
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<blockquote>
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<code>ErrorDocument 500 /cgi-bin/crash-recover<br />
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ErrorDocument 500 "Sorry, our script crashed. Oh
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dear<br />
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ErrorDocument 500 http://xxx/<br />
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ErrorDocument 404 /Lame_excuses/not_found.html<br />
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ErrorDocument 401
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/Subscription/how_to_subscribe.html</code>
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</blockquote>
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<p>The syntax is,</p>
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<p><code><a
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href="mod/core.html#errordocument">ErrorDocument</a></code>
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<3-digit-code> action</p>
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<p>where the action can be,</p>
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<ol>
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<li>Text to be displayed. Prefix the text with a quote
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("). Whatever follows the quote is displayed. <em>Note:
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the (") prefix isn't displayed.</em></li>
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<li>An external URL to redirect to.</li>
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<li>A local URL to redirect to.</li>
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</ol>
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</dd>
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</dl>
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<hr />
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<h2>Custom error responses and redirects</h2>
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<dl>
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<dt>Purpose</dt>
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<dd>Apache's behavior to redirected URLs has been modified so
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that additional environment variables are available to a
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script/server-include.</dd>
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<dt>Old behavior</dt>
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<dd>Standard CGI vars were made available to a script which
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has been redirected to. No indication of where the
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redirection came from was provided.</dd>
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<dt>New behavior</dt>
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<dd>A new batch of environment variables will be initialized
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for use by a script which has been redirected to. Each new
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variable will have the prefix <code>REDIRECT_</code>.
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<code>REDIRECT_</code> environment variables are created from
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the CGI environment variables which existed prior to the
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redirect, they are renamed with a <code>REDIRECT_</code>
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prefix, <em>i.e.</em>, <code>HTTP_USER_AGENT</code> becomes
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<code>REDIRECT_HTTP_USER_AGENT</code>. In addition to these
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new variables, Apache will define <code>REDIRECT_URL</code>
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and <code>REDIRECT_STATUS</code> to help the script trace its
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origin. Both the original URL and the URL being redirected to
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can be logged in the access log.</dd>
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</dl>
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<p>If the ErrorDocument specifies a local redirect to a CGI
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script, the script should include a "<samp>Status:</samp>"
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header field in its output in order to ensure the propagation
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all the way back to the client of the error condition that
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caused it to be invoked. For instance, a Perl ErrorDocument
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script might include the following:</p>
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<pre>
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:
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print "Content-type: text/html\n";
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printf "Status: %s Condition Intercepted\n", $ENV{"REDIRECT_STATUS"};
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:
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</pre>
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<p>If the script is dedicated to handling a particular error
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condition, such as <samp>404 Not Found</samp>, it can
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use the specific code and error text instead.</p>
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<!--#include virtual="footer.html" -->
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</body>
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</html>
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