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8 <title>Custom Error Responses - Apache HTTP Server</title>
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15 <p class="apache">Apache HTTP Server Version 2.3</p>
16 <img alt="" src="../images/feather.gif" /></div>
17 <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
19 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a></div><div id="page-content"><div id="preamble"><h1>Custom Error Responses</h1>
21 <p><span>Available Languages: </span><a href="../en/./custom-error.html" title="English"> en </a> |
22 <a href="../es/./custom-error.html" hreflang="es" rel="alternate" title="Español"> es </a> |
23 <a href="../ja/./custom-error.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
24 <a href="../ko/./custom-error.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
27 <p>Additional functionality allows webmasters to configure the response
28 of Apache to some error or problem.</p>
30 <p>Customizable responses can be defined to be activated in the event of
31 a server detected error or problem.</p>
33 <p>If a script crashes and produces a "500 Server Error" response,
34 then this response can be replaced with either some friendlier text or by
35 a redirection to another URL (local or external).</p>
37 <div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#behavior">Behavior</a></li>
38 <li><img alt="" src="../images/down.gif" /> <a href="#configuration">Configuration</a></li>
39 <li><img alt="" src="../images/down.gif" /> <a href="#custom">Custom Error Responses and Redirects</a></li>
41 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
43 <h2><a name="behavior" id="behavior">Behavior</a></h2>
49 <p>NCSA httpd 1.3 would return some boring old error/problem message
50 which would often be meaningless to the user, and would provide no
51 means of logging the symptoms which caused it.</p>
57 <p>The server can be asked to:</p>
60 <li>Display some other text, instead of the NCSA hard coded
63 <li>redirect to a local URL, or</li>
65 <li>redirect to an external URL.</li>
68 <p>Redirecting to another URL can be useful, but only if some
69 information can be passed which can then be used to explain and/or log
70 the error/problem more clearly.</p>
72 <p>To achieve this, Apache will define new CGI-like environment
75 <div class="example"><p><code>
76 REDIRECT_HTTP_ACCEPT=*/*, image/gif, image/x-xbitmap,
78 REDIRECT_HTTP_USER_AGENT=Mozilla/1.1b2 (X11; I; HP-UX A.09.05
80 REDIRECT_PATH=.:/bin:/usr/local/bin:/etc<br />
81 REDIRECT_QUERY_STRING=<br />
82 REDIRECT_REMOTE_ADDR=121.345.78.123<br />
83 REDIRECT_REMOTE_HOST=ooh.ahhh.com<br />
84 REDIRECT_SERVER_NAME=crash.bang.edu<br />
85 REDIRECT_SERVER_PORT=80<br />
86 REDIRECT_SERVER_SOFTWARE=Apache/0.8.15<br />
87 REDIRECT_URL=/cgi-bin/buggy.pl
90 <p>Note the <code>REDIRECT_</code> prefix.</p>
92 <p>At least <code>REDIRECT_URL</code> and
93 <code>REDIRECT_QUERY_STRING</code> will be passed to the
94 new URL (assuming it's a cgi-script or a cgi-include). The
95 other variables will exist only if they existed prior to
96 the error/problem. <strong>None</strong> of these will be
97 set if your <code class="directive"><a href="../mod/core.html#errordocument">ErrorDocument</a></code> is an
98 <em>external</em> redirect (anything starting with a
99 scheme name like <code>http:</code>, even if it refers to the same host
102 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
103 <div class="section">
104 <h2><a name="configuration" id="configuration">Configuration</a></h2>
107 <p>Use of <code class="directive"><a href="../mod/core.html#errordocument">ErrorDocument</a></code> is enabled
108 for .htaccess files when the
109 <code class="directive"><a href="../mod/core.html#allowoverride">AllowOverride</a></code> is set accordingly.</p>
111 <p>Here are some examples...</p>
113 <div class="example"><p><code>
114 ErrorDocument 500 /cgi-bin/crash-recover <br />
115 ErrorDocument 500 "Sorry, our script crashed. Oh dear" <br />
116 ErrorDocument 500 http://xxx/ <br />
117 ErrorDocument 404 /Lame_excuses/not_found.html <br />
118 ErrorDocument 401 /Subscription/how_to_subscribe.html
121 <p>The syntax is,</p>
123 <div class="example"><p><code>
124 ErrorDocument <3-digit-code> <action>
127 <p>where the action can be,</p>
130 <li>Text to be displayed. Prefix the text with a quote
131 ("). Whatever follows the quote is displayed. <em>Note:
132 the (") prefix isn't displayed.</em></li>
134 <li>An external URL to redirect to.</li>
136 <li>A local URL to redirect to.</li>
138 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
139 <div class="section">
140 <h2><a name="custom" id="custom">Custom Error Responses and Redirects</a></h2>
143 <p>Apache's behavior to redirected URLs has been modified so
144 that additional environment variables are available to a
145 script/server-include.</p>
147 <h3>Old behavior</h3>
150 <p>Standard CGI vars were made available to a script which
151 has been redirected to. No indication of where the
152 redirection came from was provided.</p>
155 <h3>New behavior</h3>
158 <p>A new batch of environment variables will be initialized
159 for use by a script which has been redirected to. Each new
160 variable will have the prefix <code>REDIRECT_</code>.
161 <code>REDIRECT_</code> environment variables are created from
162 the CGI environment variables which existed prior to the
163 redirect, they are renamed with a <code>REDIRECT_</code>
164 prefix, <em>i.e.</em>, <code>HTTP_USER_AGENT</code> becomes
165 <code>REDIRECT_HTTP_USER_AGENT</code>. In addition to these
166 new variables, Apache will define <code>REDIRECT_URL</code>
167 and <code>REDIRECT_STATUS</code> to help the script trace its
168 origin. Both the original URL and the URL being redirected to
169 can be logged in the access log.</p>
171 <p>If the ErrorDocument specifies a local redirect to a CGI
172 script, the script should include a "<code>Status:</code>"
173 header field in its output in order to ensure the propagation
174 all the way back to the client of the error condition that
175 caused it to be invoked. For instance, a Perl ErrorDocument
176 script might include the following:</p>
178 <div class="example"><p><code>
180 print "Content-type: text/html\n"; <br />
181 printf "Status: %s Condition Intercepted\n", $ENV{"REDIRECT_STATUS"}; <br />
185 <p>If the script is dedicated to handling a particular error
186 condition, such as <code>404 Not Found</code>, it can
187 use the specific code and error text instead.</p>
189 <p>Note that the script <em>must</em> emit an appropriate
190 <code>Status:</code> header (such as <code>302 Found</code>), if the
191 response contains a <code>Location:</code> header (in order to issue a
192 client side redirect). Otherwise the <code>Location:</code> header may
196 <div class="bottomlang">
197 <p><span>Available Languages: </span><a href="../en/./custom-error.html" title="English"> en </a> |
198 <a href="../es/./custom-error.html" hreflang="es" rel="alternate" title="Español"> es </a> |
199 <a href="../ja/./custom-error.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
200 <a href="../ko/./custom-error.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
201 </div><div id="footer">
202 <p class="apache">Copyright 2006 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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