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<p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p>
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<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="./">Version 2.4</a></div><div id="page-content"><div id="preamble"><h1>Expressions in Apache HTTP Server</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="./en/expr.html" title="English">&nbsp;en&nbsp;</a> |
<a href="./fr/expr.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
</div>

    <p>Historically, there are several syntax variants for expressions used to express
        a condition in the different modules of the Apache HTTP Server.
        There is some ongoing effort to only use a single variant, called <em>ap_expr</em>,
        for all configuration directives.
        This document describes the <em>ap_expr</em> expression parser.
    </p>
    <p>The <em>ap_expr</em> expression is intended to replace most other
        expression variants in HTTPD. For example, the deprecated
        <code class="directive"><a href="./mod/mod_ssl.html#sslrequire">SSLRequire</a></code> expressions can be
        replaced by <a href="mod/mod_authz_core.html#reqexpr">Require expr</a>.
    </p>
  </div>
<div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#grammar">Grammar in Backus-Naur Form notation</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#vars">Variables</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#binop">Binary operators</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#unnop">Unary operators</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#functions">Functions</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#examples">Example expressions</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#other">Other</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#sslrequire">Comparison with SSLRequire</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#compatibility">Version History</a></li>
</ul><h3>See also</h3><ul class="seealso"><li><code class="directive"><a href="./mod/core.html#if">&lt;If&gt;</a></code></li><li><code class="directive"><a href="./mod/core.html#elseif">&lt;ElseIf&gt;</a></code></li><li><code class="directive"><a href="./mod/core.html#else">&lt;Else&gt;</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_setenvif.html#setenvifexpr">SetEnvIfExpr</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_headers.html#requestheader">RequestHeader</a></code></li><li><code class="directive"><a href="./mod/mod_filter.html#filterprovider">FilterProvider</a></code></li><li><a href="mod/mod_authz_core.html#reqexpr">Require expr</a></li><li><code class="directive"><a href="./mod/mod_ssl.html#sslrequire">SSLRequire</a></code></li><li><code class="directive"><a href="./mod/mod_log_debug.html#logmessage">LogMessage</a></code></li><li><code class="module"><a href="./mod/mod_include.html">mod_include</a></code></li></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="grammar" id="grammar">Grammar in Backus-Naur Form notation</a></h2>
    
      <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>. 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>&amp;&amp;</strong>" expr
              | expr "<strong>||</strong>" expr
              | "<strong>(</strong>" expr "<strong>)</strong>"
              | comp

comp        ::= stringcomp
              | integercomp
              | unaryop word
              | word binaryop word
              | word "<strong>in</strong>" "<strong>{</strong>" wordlist "<strong>}</strong>"
              | word "<strong>in</strong>" listfunction
              | word "<strong>=~</strong>" regex
              | word "<strong>!~</strong>" regex


stringcomp  ::= word "<strong>==</strong>" word
              | word "<strong>!=</strong>" word
              | word "<strong>&lt;</strong>"  word
              | word "<strong>&lt;=</strong>" word
              | word "<strong>&gt;</strong>"  word
              | word "<strong>&gt;=</strong>" word

integercomp ::= word "<strong>-eq</strong>" word | word "<strong>eq</strong>" word
              | word "<strong>-ne</strong>" word | word "<strong>ne</strong>" word
              | word "<strong>-lt</strong>" word | word "<strong>lt</strong>" word
              | word "<strong>-le</strong>" word | word "<strong>le</strong>" word
              | word "<strong>-gt</strong>" word | word "<strong>gt</strong>" word
              | word "<strong>-ge</strong>" word | word "<strong>ge</strong>" word

wordlist    ::= word
              | wordlist "<strong>,</strong>" word

word        ::= word "<strong>.</strong>" word
              | digit
              | "<strong>'</strong>" string "<strong>'</strong>"
              | "<strong>"</strong>" string "<strong>"</strong>"
              | variable
              | rebackref
              | function

string      ::= stringpart
              | string stringpart

stringpart  ::= cstring
              | variable
              | rebackref

cstring     ::= ...
digit       ::= [0-9]+

variable    ::= "<strong>%{</strong>" varname "<strong>}</strong>"
              | "<strong>%{</strong>" funcname "<strong>:</strong>" funcargs "<strong>}</strong>"

rebackref   ::= "<strong>$</strong>" [0-9]

function     ::= funcname "<strong>(</strong>" word "<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">
<h2><a name="vars" id="vars">Variables</a></h2>
    

    <p>The expression parser provides a number of variables of the form
    <code>%{HTTP_HOST}</code>. Note that the value of a variable may depend
    on the phase of the request processing in which it is evaluated.  For
    example, an expression used in an <code class="directive">&lt;If &gt;</code>
    directive is evaluated before authentication is done. Therefore,
    <code>%{REMOTE_USER}</code> will not be set in this case.</p>

    <p>The following variables provide the values of the named HTTP request
    headers. The values of other headers can be obtained with the
    <code>req</code> <a href="#functions">function</a>. Using these
    variables may cause the header name to be added to the Vary
    header of the HTTP response, except where otherwise noted for the
    directive accepting the expression. The <code>req_novary</code>
    <a href="#functions">function</a> may be used to circumvent this
    behavior.</p>

    <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>
</table>

    <p>Other request related variables</p>

    <table class="bordered"><tr class="header"><th>Name</th><th>Description</th></tr>
<tr><td><code>REQUEST_METHOD</code></td>
        <td>The HTTP method of the incoming request (e.g.
            <code>GET</code>)</td></tr>
<tr class="odd"><td><code>REQUEST_SCHEME</code></td>
        <td>The scheme part of the request's URI</td></tr>
<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>
<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
            time <code>REQUEST_FILENAME</code> is referenced. Otherwise, such
            as when used in virtual host context, the same value as
            <code>REQUEST_URI</code> </td></tr>
<tr class="odd"><td><code>SCRIPT_FILENAME</code></td>
        <td>Same as <code>REQUEST_FILENAME</code></td></tr>
<tr><td><code>LAST_MODIFIED</code></td>
        <td>The date and time of last modification of the file in the format
            <code>20101231235959</code>, if this has already been determined by
            the server at the time <code>LAST_MODIFIED</code> is referenced.
            </td></tr>
<tr class="odd"><td><code>SCRIPT_USER</code></td>
        <td>The user name of the owner of the script.</td></tr>
<tr><td><code>SCRIPT_GROUP</code></td>
        <td>The group name of the group of the script.</td></tr>
<tr class="odd"><td><code>PATH_INFO</code></td>
        <td>The trailing path name information, see
            <code class="directive"><a href="./mod/core.html#acceptpathinfo">AcceptPathInfo</a></code></td></tr>
<tr><td><code>QUERY_STRING</code></td>
        <td>The query string of the current request</td></tr>
<tr class="odd"><td><code>IS_SUBREQ</code></td>
        <td>"<code>true</code>" if the current request is a subrequest,
            "<code>false</code>" otherwise</td></tr>
<tr><td><code>THE_REQUEST</code></td>
        <td>The complete request line (e.g.,
            "<code>GET /index.html HTTP/1.1</code>")</td></tr>
<tr class="odd"><td><code>REMOTE_ADDR</code></td>
        <td>The IP address of the remote host</td></tr>
<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>
<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 <code class="directive"><a href="./mod/core.html#servername">ServerName</a></code> of
            the current vhost</td></tr>
<tr><td><code>SERVER_PORT</code></td>
        <td>The server port of the current vhost, see
            <code class="directive"><a href="./mod/core.html#servername">ServerName</a></code></td></tr>
<tr class="odd"><td><code>SERVER_ADMIN</code></td>
        <td>The <code class="directive"><a href="./mod/core.html#serveradmin">ServerAdmin</a></code> of
            the current vhost</td></tr>
<tr><td><code>SERVER_PROTOCOL</code></td>
        <td>The protocol used by the request</td></tr>
<tr class="odd"><td><code>DOCUMENT_ROOT</code></td>
        <td>The <code class="directive"><a href="./mod/core.html#documentroot">DocumentRoot</a></code> of
            the current vhost</td></tr>
<tr><td><code>AUTH_TYPE</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 class="odd"><td><code>CONTENT_TYPE</code></td>
        <td>The content type of the response</td></tr>
<tr><td><code>HANDLER</code></td>
        <td>The name of the <a href="handler.html">handler</a> creating
            the response</td></tr>
<tr class="odd"><td><code>HTTPS</code></td>
        <td>"<code>on</code>" if the request uses https,
            "<code>off</code>" otherwise</td></tr>
<tr><td><code>IPV6</code></td>
        <td>"<code>on</code>" if the connection uses IPv6,
            "<code>off</code>" otherwise</td></tr>
<tr class="odd"><td><code>REQUEST_STATUS</code></td>
        <td>The HTTP error status of the request</td></tr>
<tr><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_LOG_ID</code></td>
        <td>The error log id of the connection (see
            <code class="directive"><a href="./mod/core.html#errorlogformat">ErrorLogFormat</a></code>)</td></tr>
<tr><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>
</table>

    <p>Misc variables</p>

    <table class="bordered"><tr class="header"><th>Name</th><th>Description</th></tr>
<tr><td><code>TIME_YEAR</code></td>
        <td>The current year (e.g. <code>2010</code>)</td></tr>
<tr class="odd"><td><code>TIME_MON</code></td>
        <td>The current month (<code>1</code>, ..., <code>12</code>)</td></tr>
<tr><td><code>TIME_DAY</code></td>
        <td>The current day of the month</td></tr>
<tr class="odd"><td><code>TIME_HOUR</code></td>
        <td>The hour part of the current time
            (<code>0</code>, ..., <code>23</code>)</td></tr>
<tr><td><code>TIME_MIN</code></td>
        <td>The minute part of the current time </td></tr>
<tr class="odd"><td><code>TIME_SEC</code></td>
        <td>The second part of the current time </td></tr>
<tr><td><code>TIME_WDAY</code></td>
        <td>The day of the week (starting with <code>0</code>
            for Sunday)</td></tr>
<tr class="odd"><td><code>TIME</code></td>
        <td>The date and time in the format <code>20101231235959</code></td></tr>
<tr><td><code>SERVER_SOFTWARE</code></td>
        <td>The server version string</td></tr>
<tr class="odd"><td><code>API_VERSION</code></td>
        <td>The date of the API version (module magic number)</td></tr>
</table>

    <p>Some modules register additional variables, see e.g. <code class="module"><a href="./mod/mod_ssl.html">mod_ssl</a></code>.</p>

</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="binop" id="binop">Binary operators</a></h2>
    

    <p>With the exception of some built-in comparison operators, binary
    operators have the form "<code>-[a-zA-Z][a-zA-Z0-9_]+</code>", i.e. a
    minus and at least two characters. The name is not case sensitive.
    Modules may register additional binary operators.</p>

    <h3><a name="comp" id="comp">Comparison operators</a></h3>
    

    <table class="bordered"><tr class="header"><th>Name</th><th>Alternative</th> <th>Description</th></tr>
<tr><td><code>==</code></td>
        <td><code>=</code></td>
        <td>String equality</td></tr>
<tr class="odd"><td><code>!=</code></td>
        <td />
        <td>String inequality</td></tr>
<tr><td><code>&lt;</code></td>
        <td />
        <td>String less than</td></tr>
<tr class="odd"><td><code>&lt;=</code></td>
        <td />
        <td>String less than or equal</td></tr>
<tr><td><code>&gt;</code></td>
        <td />
        <td>String greater than</td></tr>
<tr class="odd"><td><code>&gt;=</code></td>
        <td />
        <td>String greater than or equal</td></tr>
<tr><td><code>-eq</code></td>
        <td><code>eq</code></td>
        <td>Integer equality</td></tr>
<tr class="odd"><td><code>-ne</code></td>
        <td><code>ne</code></td>
        <td>Integer inequality</td></tr>
<tr><td><code>-lt</code></td>
        <td><code>lt</code></td>
        <td>Integer less than</td></tr>
<tr class="odd"><td><code>-le</code></td>
        <td><code>le</code></td>
        <td>Integer less than or equal</td></tr>
<tr><td><code>-gt</code></td>
        <td><code>gt</code></td>
        <td>Integer greater than</td></tr>
<tr class="odd"><td><code>-ge</code></td>
        <td><code>ge</code></td>
        <td>Integer greater than or equal</td></tr>
</table>
    

    <h3><a name="binaryother" id="binaryother">Other binary operators</a></h3>
    

    <table class="bordered"><tr class="header"><th>Name</th><th>Description</th></tr>
<tr><td><code>-ipmatch</code></td>
        <td>IP address matches address/netmask</td></tr>
<tr class="odd"><td><code>-strmatch</code></td>
        <td>left string matches pattern given by right string (containing
            wildcards *, ?, [])</td></tr>
<tr><td><code>-strcmatch</code></td>
        <td>same as <code>-strmatch</code>, but case insensitive</td></tr>
<tr class="odd"><td><code>-fnmatch</code></td>
        <td>same as <code>-strmatch</code>, but slashes are not matched by
            wildcards</td></tr>
</table>
    

</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="unnop" id="unnop">Unary operators</a></h2>
    

    <p>Unary operators take one argument and have the form
    "<code>-[a-zA-Z]</code>", i.e. a minus and one character.
    The name <em>is</em> case sensitive.
    Modules may register additional unary operators.</p>

    <table class="bordered"><tr class="header"><th>Name</th><th>Description</th><th>Restricted</th></tr>
<tr><td><code>-d</code></td>
        <td>The argument is treated as a filename.
            True if the file exists and is a directory</td><td>yes</td></tr>
<tr class="odd"><td><code>-e</code></td>
        <td>The argument is treated as a filename.
            True if the file (or dir or special) exists</td><td>yes</td></tr>
<tr><td><code>-f</code></td>
        <td>The argument is treated as a filename.
            True if the file exists and is regular file</td><td>yes</td></tr>
<tr class="odd"><td><code>-s</code></td>
        <td>The argument is treated as a filename.
            True if the file exists and is not empty</td><td>yes</td></tr>
<tr><td><code>-L</code></td>
        <td>The argument is treated as a filename.
            True if the file exists and is symlink</td><td>yes</td></tr>
<tr class="odd"><td><code>-h</code></td>
        <td>The argument is treated as a filename.
            True if the file exists and is symlink
            (same as <code>-L</code>)</td><td>yes</td></tr>
<tr><td><code>-F</code></td>
        <td>True if string is a valid file, accessible via all the server's
            currently-configured access controls for that path. This uses an
            internal subrequest to do the check, so use it with care - it can
            impact your server's performance!</td><td /></tr>
<tr class="odd"><td><code>-U</code></td>
        <td>True if string is a valid URL, accessible via all the server's
            currently-configured access controls for that path. This uses an
            internal subrequest to do the check, so use it with care - it can
            impact your server's performance!</td><td /></tr>
<tr><td><code>-A</code></td>
        <td>Alias for <code>-U</code></td><td /></tr>
<tr class="odd"><td><code>-n</code></td>
        <td>True if string is not empty</td><td /></tr>
<tr><td><code>-z</code></td>
        <td>True if string is empty</td><td /></tr>
<tr class="odd"><td><code>-T</code></td>
        <td>False if string is empty, "<code>0</code>", "<code>off</code>",
            "<code>false</code>", or "<code>no</code>" (case insensitive).
            True otherwise.</td><td /></tr>
<tr><td><code>-R</code></td>
        <td>Same as "<code>%{REMOTE_ADDR} -ipmatch ...</code>", but more efficient
        </td><td /></tr>
</table>

    <p>The operators marked as "restricted" are not available in some modules
    like <code class="module"><a href="./mod/mod_include.html">mod_include</a></code>.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="functions" id="functions">Functions</a></h2>
    

    <p>Normal string-valued functions take one string as argument and return
    a string. Functions names are not case sensitive.
    Modules may register additional functions.</p>

    <table class="bordered"><tr class="header"><th>Name</th><th>Description</th><th>Restricted</th></tr>
<tr><td><code>req</code>, <code>http</code></td>
        <td>Get HTTP request header; header names may be added to the Vary
            header, see below</td><td /></tr>
<tr class="odd"><td><code>req_novary</code></td>
        <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>
<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 variables).</td><td /></tr>
<tr><td><code>osenv</code></td>
        <td>Lookup operating system environment variable</td><td /></tr>
<tr class="odd"><td><code>note</code></td>
        <td>Lookup request note</td><td /></tr>
<tr><td><code>env</code></td>
        <td>Return first match of <code>note</code>, <code>reqenv</code>,
            <code>osenv</code></td><td /></tr>
<tr class="odd"><td><code>tolower</code></td>
        <td>Convert string to lower case</td><td /></tr>
<tr><td><code>toupper</code></td>
        <td>Convert string to uppser case</td><td /></tr>
<tr class="odd"><td><code>escape</code></td>
        <td>Escape special characters in %hex encoding</td><td /></tr>
<tr><td><code>unescape</code></td>
        <td>Unescape %hex encoded string, leaving encoded slashes alone;
            return empty string if %00 is found</td><td /></tr>
<tr class="odd"><td><code>file</code></td>
        <td>Read contents from a file</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>
</table>

    <p>The functions marked as "restricted" are not available in some modules
    like <code class="module"><a href="./mod/mod_include.html">mod_include</a></code>.</p>

    <p>When the functions <code>req</code> or <code>http</code> are used,
    the header name will automatically be added to the Vary header of the
    HTTP response, except where otherwise noted for the directive accepting
    the expression. The <code>req_novary</code> function can be used to
    prevent names from being added to the Vary header.</p>

    <p>In addition to string-valued functions, there are also list-valued functions which
    take one string as argument and return a wordlist, i.e. a list of strings. The wordlist
    can be used with the special <code>-in</code> operator.
    Functions names are not case sensitive.
    Modules may register additional functions.</p>

    <p>There are no built-in list-valued functions. <code class="module"><a href="./mod/mod_ssl.html">mod_ssl</a></code>
    provides <code>PeerExtList</code>.  See the description of
    <code class="directive"><a href="./mod/mod_ssl.html#sslrequire">SSLRequire</a></code> for details
    (but <code>PeerExtList</code> is also usable outside
    of <code class="directive"><a href="./mod/mod_ssl.html#sslrequire">SSLRequire</a></code>).</p>

</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="examples" id="examples">Example expressions</a></h2>
    
	
	<p>The following examples show how expressions might be used to evaluate requests:</p>
	
	<pre class="prettyprint lang-config">
# Compare the host name to example.com and redirect to www.example.com if it matches
&lt;If "%{HTTP_HOST} == 'example.com'"&gt;
    Redirect permanent / http://www.example.com/
&lt;/If&gt;

# Force text/plain if requesting a file with the query string contains 'forcetext'
&lt;If "%{QUERY_STRING} =~ /forcetext/"&gt;
    ForceType text/plain
&lt;/If&gt;

# Only allow access to this content during business hours
&lt;Directory "/foo/bar/business"&gt;
    Require expr %{TIME_HOUR} -gt 9 &amp;&amp; %{TIME_HOUR} -lt 17 
&lt;/Directory&gt;	
	</pre>

</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="other" id="other">Other</a></h2>
    

    <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>
<tr class="odd"><td><code>/regexp/</code></td>
        <td><code>m#regexp#</code></td>
        <td>Regular expression (the second form allows different delimiters than /)</td></tr>
<tr><td><code>/regexp/i</code></td>
        <td><code>m#regexp#i</code></td>
        <td>Case insensitive regular expression</td></tr>
<tr class="odd"><td><code>$0 ... $9</code></td>
        <td />
        <td>Regular expression backreferences</td></tr>
</table>

    <h3><a name="rebackref" id="rebackref">Regular expression backreferences</a></h3>
        
        <p>The strings <code>$0</code> ... <code>$9</code> allow to reference
        the capture groups from a previously executed, successfully
        matching regular expressions. They can normally only be used in the
        same expression as the matching regex, but some modules allow special
        uses.</p>
    

</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="sslrequire" id="sslrequire">Comparison with SSLRequire</a></h2>
    
    <p>The <em>ap_expr</em> syntax is mostly a superset of the syntax of the
    deprecated <code class="directive"><a href="./mod/mod_ssl.html#sslrequire">SSLRequire</a></code> directive.
    The differences are described in <code class="directive"><a href="./mod/mod_ssl.html#sslrequire">SSLRequire</a></code>'s documentation.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="compatibility" id="compatibility">Version History</a></h2>
    
    <p>The <code>req_novary</code> <a href="#functions">function</a>
    is available for versions 2.4.4 and later.</p>
</div></div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="./en/expr.html" title="English">&nbsp;en&nbsp;</a> |
<a href="./fr/expr.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
</div><div class="top"><a href="#page-header"><img src="./images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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