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DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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TITLE>Custom error responses</
TITLE>
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H1 ALIGN="CENTER">Custom error responses</
H1>
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DD>Additional functionality. Allows webmasters to configure the response of
4586N/A Apache to some error or problem.
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P>Customizable responses can be defined to be activated in the
3980N/A event of a server detected error or problem.
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P>
e.g. if a script crashes and produces a "500 Server Error"
4586N/A response, then this response can be replaced with either some
4586N/A friendlier text or by a redirection to another URL (local or
4586N/A which would often be meaningless to the user, and would provide no
4586N/A means of logging the symptoms which caused it.<
BR>
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DD>The server can be asked to;
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LI>Display some other text, instead of the NCSA hard coded messages, or
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LI>redirect to a local URL, or
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LI>redirect to an external URL.
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P>Redirecting to another URL can be useful, but only if some information
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P>To achieve this, Apache will define new CGI-like environment
4586N/AREDIRECT_REMOTE_ADDR=121.345.78.123 <
br>
4586N/AREDIRECT_SERVER_PORT=80 <
br>
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P>note the <
code>REDIRECT_</
code> prefix.
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P>At least <
code>REDIRECT_URL</
code> and <
code>REDIRECT_QUERY_STRING</
code> will
4586N/A be passed to the new URL (assuming it's a cgi-script or a cgi-include). The
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b>None</
b> of these will be set if your ErrorDocument is an
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i>external</
i> redirect (
i.e. anything starting with a protocol name
4586N/A like <
code>http:</
code>, even if it refers to the same host as the
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DD> Use of "ErrorDocument" is enabled for .htaccess files when the
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P>Here are some examples...
4586N/AErrorDocument 500 "Sorry, our script crashed. Oh dear<
br>
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P>where the action can be,
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LI>Text to be displayed. Prefix the text with a quote ("). Whatever
4586N/A follows the quote is displayed. <
em>Note: the (") prefix isn't
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LI>An external URL to redirect to.
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LI>A local URL to redirect to.
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h2>Custom error responses and redirects</
H2>
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DD>Apache's behavior to redirected URLs has been modified so that additional
<
DD>Standard CGI vars were made available to a script which has been
redirected to. No indication of where the redirection came from was provided.
A new batch of environment variables will be initialized for use by a
script which has been redirected to. Each new variable will have the
prefix <
code>REDIRECT_</
code>. <
code>REDIRECT_</
code> environment
variables are created from the CGI environment variables which existed
prior to the redirect, they are renamed with a <
code>REDIRECT_</
code>
prefix,
i.e. <
code>HTTP_USER_AGENT</
code> becomes
<
code>REDIRECT_HTTP_USER_AGENT</
code>. In addition to these new
variables, Apache will define <
code>REDIRECT_URL</
code> and
<
code>REDIRECT_STATUS</
code> to help the script trace its origin.
Both the original URL and the URL being redirected to can be logged in