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-<title>Expressions in Apache HTTP Server - Apache HTTP Server</title>
+<title>Expressions in Apache HTTP Server - Apache HTTP Server Version 2.5</title>
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<p><a href="http://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form">Backus-Naur
Form</a> (BNF) is a notation technique for context-free grammars,
often used to describe the syntax of languages used in computing.
- In most cases, expressions are used to express boolean values. For
- these, the starting point in the BNF is <code>expr</code>.
+ In most cases, expressions are used to express boolean values.
+ For these, the starting point in the BNF is <code>expr</code>.
However, a few directives like <code class="directive"><a href="./mod/mod_log_debug.html#logmessage">LogMessage</a></code> accept expressions
that evaluate to a string value. For those, the starting point in
the BNF is <code>string</code>.
</p>
+<blockquote>
<pre>expr ::= "<strong>true</strong>" | "<strong>false</strong>"
| "<strong>!</strong>" expr
| expr "<strong>&&</strong>" expr
rebackref ::= "<strong>$</strong>" [0-9]
-function ::= funcname "<strong>(</strong>" word "<strong>)</strong>"
+function ::= funcname "<strong>(</strong>" wordlist "<strong>)</strong>"
listfunction ::= listfuncname "<strong>(</strong>" word "<strong>)</strong>"</pre>
+</blockquote>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<table class="bordered"><tr class="header"><th>Name</th></tr>
<tr><td><code>HTTP_ACCEPT</code></td></tr>
-<tr class="odd"><td><code>HTTP_FORWARDED</code></td></tr>
-<tr><td><code>HTTP_HOST</code></td></tr>
-<tr class="odd"><td><code>HTTP_PROXY_CONNECTION</code></td></tr>
-<tr><td><code>HTTP_REFERER</code></td></tr>
-<tr class="odd"><td><code>HTTP_USER_AGENT</code></td></tr>
+<tr class="odd"><td><code>HTTP_COOKIE</code></td></tr>
+<tr><td><code>HTTP_FORWARDED</code></td></tr>
+<tr class="odd"><td><code>HTTP_HOST</code></td></tr>
+<tr><td><code>HTTP_PROXY_CONNECTION</code></td></tr>
+<tr class="odd"><td><code>HTTP_REFERER</code></td></tr>
+<tr><td><code>HTTP_USER_AGENT</code></td></tr>
</table>
<p>Other request related variables</p>
<tr><td><code>REQUEST_URI</code></td>
<td>The path part of the request's URI</td></tr>
<tr class="odd"><td><code>DOCUMENT_URI</code></td>
- <td>Same as REQUEST_URI</td></tr>
+ <td>Same as <code>REQUEST_URI</code></td></tr>
<tr><td><code>REQUEST_FILENAME</code></td>
<td>The full local filesystem path to the file or script matching the
request, if this has already been determined by the server at the
<tr><td><code>REMOTE_HOST</code></td>
<td>The host name of the remote host</td></tr>
<tr class="odd"><td><code>REMOTE_USER</code></td>
- <td>The name of the authenticated user (if any)</td></tr>
+ <td>The name of the authenticated user, if any (not available during <code class="directive"><If></code>)</td></tr>
<tr><td><code>REMOTE_IDENT</code></td>
<td>The user name set by <code class="module"><a href="./mod/mod_ident.html">mod_ident</a></code></td></tr>
<tr class="odd"><td><code>SERVER_NAME</code></td>
<td>The configured <code class="directive"><a href="./mod/mod_authn_core.html#authtype">AuthType</a></code> (e.g.
"<code>basic</code>")</td></tr>
<tr><td><code>CONTENT_TYPE</code></td>
- <td>The content type of the response</td></tr>
+ <td>The content type of the response (not available during <code class="directive"><If></code>)</td></tr>
<tr class="odd"><td><code>HANDLER</code></td>
<td>The name of the <a href="handler.html">handler</a> creating
the response</td></tr>
<td>"<code>on</code>" if the connection uses IPv6,
"<code>off</code>" otherwise</td></tr>
<tr><td><code>REQUEST_STATUS</code></td>
- <td>The HTTP error status of the request</td></tr>
+ <td>The HTTP error status of the request (not available during <code class="directive"><If></code>)</td></tr>
<tr class="odd"><td><code>REQUEST_LOG_ID</code></td>
<td>The error log id of the request (see
<code class="directive"><a href="./mod/core.html#errorlogformat">ErrorLogFormat</a></code>)</td></tr>
<tr class="odd"><td><code>CONN_REMOTE_ADDR</code></td>
<td>The peer IP address of the connection (see the
<code class="module"><a href="./mod/mod_remoteip.html">mod_remoteip</a></code> module)</td></tr>
+<tr><td><code>CONTEXT_PREFIX</code></td>
+ <td /></tr>
+<tr class="odd"><td><code>CONTEXT_DOCUMENT_ROOT</code></td>
+ <td /></tr>
</table>
<p>Misc variables</p>
<td>Same as <code>req</code>, but header names will not be added to the
Vary header</td><td /></tr>
<tr><td><code>resp</code></td>
- <td>Get HTTP response header</td><td /></tr>
+ <td>Get HTTP response header (most response headers will not yet be set during <code class="directive"><If></code>)</td><td /></tr>
<tr class="odd"><td><code>reqenv</code></td>
<td>Lookup request environment variable (as a shortcut,
<code>v</code> can be used too to access
<td>Hash the string using SHA1, then encode the hash with hexadecimal
encoding</td><td /></tr>
<tr class="odd"><td><code>file</code></td>
- <td>Read contents from a file</td><td>yes</td></tr>
+ <td>Read contents from a file (including line endings, when present)
+ </td><td>yes</td></tr>
<tr><td><code>filesize</code></td>
<td>Return size of a file (or 0 if file does not exist or is not
regular file)</td><td>yes</td></tr>
<tr class="odd"><td><code>ldap</code></td>
<td>Escape characters as required by LDAP distinguished name escaping
(RFC4514) and LDAP filter escaping (RFC4515).</td><td /></tr>
+<tr><td><code>replace</code></td>
+ <td>replace(string, "from", "to") replaces all occurences of "from"
+ in the string with "to".</td><td /></tr>
</table>
<p>The functions marked as "restricted" are not available in some modules
# Only allow access to this content during business hours
<Directory "/foo/bar/business">
Require expr %{TIME_HOUR} -gt 9 && %{TIME_HOUR} -lt 17
-</Directory></pre>
+</Directory>
+
+# Check a HTTP header for a list of values
+<If "%{HTTP:X-example-header} in { 'foo', 'bar', 'baz' }">
+ Header set matched true
+</If>
+
+# Check an environment variable for a regular expression, negated.
+<If "! reqenv('REDIRECT_FOO') =~ /bar/">
+ Header set matched true
+</If>
+
+# Check result of URI mapping by running in Directory context with -f
+<Directory /var/www>
+ AddEncoding x-gzip gz
+<If "-f '%{REQUEST_FILENAME}.unzipme' && ! %{HTTP:Accept-Encoding} =~ /gzip/">
+ SetOutputFilter INFLATE
+</If>
+</Directory>
+
+# Function examples in boolean context
+<If "md5('foo') == 'acbd18db4cc2f85cedef654fccc4a4d8'">
+ Header set checksum-matched true
+</If>
+<If "md5('foo') == replace('md5:XXXd18db4cc2f85cedef654fccc4a4d8', 'md5:XXX', 'acb')>
+ Header set checksum-matched-2 true
+</If>
+
+# Function example in string context
+Header set foo-checksum "expr=%{md5:foo}"</pre>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<table class="bordered"><tr class="header"><th>Name</th><th>Alternative</th> <th>Description</th></tr>
<tr><td><code>-in</code></td>
<td><code>in</code></td>
- <td>string contained in string list</td></tr>
+ <td>string contained in wordlist</td></tr>
<tr class="odd"><td><code>/regexp/</code></td>
<td><code>m#regexp#</code></td>
<td>Regular expression (the second form allows different
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