<title>Environment Variables in Apache - Apache HTTP Server</title>
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-<p class="apache">Apache HTTP Server Version 2.3</p>
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+<p class="apache">Apache HTTP Server Version 2.5</p>
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-<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>Environment Variables in Apache</h1>
+<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.
5</a></div><div id="page-content"><div id="preamble"><h1>Environment Variables in Apache</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="./en/env.html" title="English"> en </a> |
<a href="./fr/env.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
<li><img alt="" src="./images/down.gif" /> <a href="#using">Using Environment Variables</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#special">Special Purpose Environment Variables</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#examples">Examples</a></li>
-</ul></div>
+</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="setting" id="setting">Setting Environment Variables</a></h2>
late during request processing meaning that directives such as
<code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code> and <code class="directive"><a href="./mod/mod_rewrite.html#rewritecond">RewriteCond</a></code> will not see the
variables set with it.</li>
+
+ <li>When the server looks up a path via an internal
+ <a class="glossarylink" href="./glossary.html#subrequest" title="see glossary">subrequest</a> such as looking
+ for a <code class="directive"><a href="./mod/mod_dir.html#directoryindex">DirectoryIndex</a></code>
+ or generating a directory listing with <code class="module"><a href="./mod/mod_autoindex.html">mod_autoindex</a></code>,
+ per-request environment variables are <em>not</em> inherited in the
+ subrequest. Additionally,
+ <code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code> directives
+ are not separately evaluated in the subrequest due to the API phases
+ <code class="module"><a href="./mod/mod_setenvif.html">mod_setenvif</a></code> takes action in.</li>
</ul>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<h2><a name="using" id="using">Using Environment Variables</a></h2>
- <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_authz_host.html">mod_authz_host</a></code></li><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li><li><code class="module"><a href="./mod/mod_ext_filter.html">mod_ext_filter</a></code></li><li><code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code></li><li><code class="module"><a href="./mod/mod_include.html">mod_include</a></code></li><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_authz_
host.html#allow">Allow</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code></li><li><code class="directive"><a href="./mod/mod_authz_host.html#deny">Deny</a></code></li><li><code class="directive"><a href="./mod/mod_ext_filter.html#extfilterdefine">ExtFilterDefine</a></code></li><li><code class="directive"><a href="./mod/mod_headers.html#header">Header</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewritecond">RewriteCond</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewriterule">RewriteRule</a></code></li></ul></td></tr></table>
+ <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_authz_host.html">mod_authz_host</a></code></li><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li><li><code class="module"><a href="./mod/mod_ext_filter.html">mod_ext_filter</a></code></li><li><code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code></li><li><code class="module"><a href="./mod/mod_include.html">mod_include</a></code></li><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_authz_
core.html#require">Require</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code></li><li><code class="directive"><a href="./mod/mod_access_compat.html#deny">Deny</a></code></li><li><code class="directive"><a href="./mod/mod_ext_filter.html#extfilterdefine">ExtFilterDefine</a></code></li><li><code class="directive"><a href="./mod/mod_headers.html#header">Header</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewritecond">RewriteCond</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewriterule">RewriteRule</a></code></li></ul></td></tr></table>
<h3><a name="cgi-scripts" id="cgi-scripts">CGI Scripts</a></h3>
</a></code> and <code class="module"><a href="./mod/mod_header.html">mod_header</a></code> allows you to still accept
these headers:</p>
-<div class="example"><p><code>
-# <br />
-# The following works around a client sending a broken Accept_Encoding<br />
-# header.<br />
-#<br />
-SetEnvIfNoCase ^Accept.Encoding$ ^(.*)$ fix_accept_encoding=$1<br />
+<pre class="prettyprint lang-config">
+#
+# The following works around a client sending a broken Accept_Encoding
+# header.
+#
+SetEnvIfNoCase ^Accept.Encoding$ ^(.*)$ fix_accept_encoding=$1
RequestHeader set Accept-Encoding %{fix_accept_encoding}e env=fix_accept_encoding
-</code></p></div>
+</pre>
+
httpd.conf to deal with known client problems. Since the affected clients
are no longer seen in the wild, this configuration is likely no-longer
necessary.</p>
-<div class="example"><p><code>
-#<br />
-# The following directives modify normal HTTP response behavior.<br />
-# The first directive disables keepalive for Netscape 2.x and browsers that<br />
-# spoof it. There are known problems with these browser implementations.<br />
-# The second directive is for Microsoft Internet Explorer 4.0b2<br />
-# which has a broken HTTP/1.1 implementation and does not properly<br />
-# support keepalive when it is used on 301 or 302 (redirect) responses.<br />
-#<br />
-BrowserMatch "Mozilla/2" nokeepalive<br />
-BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0<br />
-<br />
-#<br />
-# The following directive disables HTTP/1.1 responses to browsers which<br />
-# are in violation of the HTTP/1.0 spec by not being able to understand a<br />
-# basic 1.1 response.<br />
-#<br />
-BrowserMatch "RealPlayer 4\.0" force-response-1.0<br />
-BrowserMatch "Java/1\.0" force-response-1.0<br />
+<pre class="prettyprint lang-config">
+#
+# The following directives modify normal HTTP response behavior.
+# The first directive disables keepalive for Netscape 2.x and browsers that
+# spoof it. There are known problems with these browser implementations.
+# The second directive is for Microsoft Internet Explorer 4.0b2
+# which has a broken HTTP/1.1 implementation and does not properly
+# support keepalive when it is used on 301 or 302 (redirect) responses.
+#
+BrowserMatch "Mozilla/2" nokeepalive
+BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0
+
+#
+# The following directive disables HTTP/1.1 responses to browsers which
+# are in violation of the HTTP/1.0 spec by not being able to understand a
+# basic 1.1 response.
+#
+BrowserMatch "RealPlayer 4\.0" force-response-1.0
+BrowserMatch "Java/1\.0" force-response-1.0
BrowserMatch "JDK/1\.0" force-response-1.0
-</code></p></div>
+</pre>
+
<h3><a name="no-img-log" id="no-img-log">Do not log requests for images in the access log</a></h3>
particular directories, or to prevent logging of requests
coming from particular hosts.</p>
- <div class="example"><p><code>
- SetEnvIf Request_URI \.gif image-request<br />
- SetEnvIf Request_URI \.jpg image-request<br />
- SetEnvIf Request_URI \.png image-request<br />
- CustomLog logs/access_log common env=!image-request
- </code></p></div>
+ <pre class="prettyprint lang-config">
+SetEnvIf Request_URI \.gif image-request
+SetEnvIf Request_URI \.jpg image-request
+SetEnvIf Request_URI \.png image-request
+CustomLog logs/access_log common env=!image-request
+ </pre>
+
<h3><a name="image-theft" id="image-theft">Prevent "Image Theft"</a></h3>
in limited circumstances. We assume that all your images are in
a directory called <code>/web/images</code>.</p>
- <div class="example"><p><code>
- SetEnvIf Referer "^http://www\.example\.com/" local_referal<br />
- # Allow browsers that do not send Referer info<br />
- SetEnvIf Referer "^$" local_referal<br />
- <Directory /web/images><br />
- <span class="indent">
- Order Deny,Allow<br />
- Deny from all<br />
- Allow from env=local_referal
- </span>
- </Directory>
- </code></p></div>
+ <pre class="prettyprint lang-config">
+SetEnvIf Referer "^http://www\.example\.com/" local_referal
+# Allow browsers that do not send Referer info
+SetEnvIf Referer "^$" local_referal
+<Directory /web/images>
+ Require env local_referal
+</Directory>
+ </pre>
+
<p>For more information about this technique, see the
"<a href="http://www.serverwatch.com/tutorials/article.php/1132731">Keeping Your Images from Adorning Other Sites</a>"
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