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    <h1 align="CENTER">Module mod_setenvif</h1>

    <p>This module provides the ability to set environment
    variables based upon attributes of the request.</p>

    <p><a href="module-dict.html#Status"
    rel="Help"><strong>Status:</strong></a> Base<br />
     <a href="module-dict.html#SourceFile"
    rel="Help"><strong>Source File:</strong></a>
    mod_setenvif.c<br />
     <a href="module-dict.html#ModuleIdentifier"
    rel="Help"><strong>Module Identifier:</strong></a>
    setenvif_module<br />
     <a href="module-dict.html#Compatibility"
    rel="Help"><strong>Compatibility:</strong></a> Available in
    Apache 1.3 and later.</p>

    <h2>Summary</h2>

    <p>The <samp>mod_setenvif</samp> module allows you to set
    environment variables according to whether different aspects of
    the request match <a href="../misc/FAQ.html#regex">regular
    expressions</a> you specify. These environment variables can be
    used by other parts of the server to make decisions about
    actions to be taken.</p>

    <p>The directives are considered in the order they appear in
    the configuration files. So more complex sequences can be used,
    such as this example, which sets <code>netscape</code> if the
    browser is mozilla but not MSIE.</p>

    <blockquote>
<pre>
  BrowserMatch ^Mozilla netscape
  BrowserMatch MSIE !netscape
 
</pre>
    </blockquote>

    <p>For additional information, we provide a document on <a
    href="../env.html">Environment Variables in Apache</a>.</p>

    <h2>Directives</h2>

    <ul>
      <li><a href="#browsermatch">BrowserMatch</a></li>

      <li><a href="#browsermatchnocase">BrowserMatchNoCase</a></li>

      <li><a href="#setenvif">SetEnvIf</a></li>

      <li><a href="#setenvifnocase">SetEnvIfNoCase</a></li>
    </ul>
    <hr />
    <!-- the HR is part of the directive description -->

    <h2><a id="browsermatch" name="browsermatch">BrowserMatch
    directive</a></h2>

    <p><a href="directive-dict.html#Syntax"
    rel="Help"><strong>Syntax:</strong></a> BrowserMatch <em>regex
    env-variable</em>[=<em>value</em>]
    [<em>env-variable</em>[=<em>value</em>]] ...<br />
     <a href="directive-dict.html#Default"
    rel="Help"><strong>Default:</strong></a> <i>none</i><br />
     <a href="directive-dict.html#Context"
    rel="Help"><strong>Context:</strong></a> server config, virtual
    host, directory, .htaccess<br />
     <a href="directive-dict.html#Override"
    rel="Help"><strong>Override:</strong></a> FileInfo<br />
     <a href="directive-dict.html#Status"
    rel="Help"><strong>Status:</strong></a> Base<br />
     <a href="directive-dict.html#Module"
    rel="Help"><strong>Module:</strong></a> mod_setenvif<br />
     <a href="directive-dict.html#Compatibility"
    rel="Help"><strong>Compatibility:</strong></a> Apache 1.2 and
    above (in Apache 1.2 this directive was found in the
    now-obsolete mod_browser module); use in .htaccess files only
    supported with 1.3.13 and later</p>

    <p>The BrowserMatch directive defines environment variables
    based on the <samp>User-Agent</samp> HTTP request header field.
    The first argument should be a POSIX.2 extended regular
    expression (similar to an <samp>egrep</samp>-style regex). The
    rest of the arguments give the names of variables to set, and
    optionally values to which they should be set. These take the
    form of</p>

    <ol>
      <li><samp><em>varname</em></samp>, or</li>

      <li><samp>!<em>varname</em></samp>, or</li>

      <li><samp><em>varname</em>=<em>value</em></samp></li>
    </ol>

    <p>In the first form, the value will be set to "1". The second
    will remove the given variable if already defined, and the
    third will set the variable to the value given by
    <samp><em>value</em></samp>. If a <samp>User-Agent</samp>
    string matches more than one entry, they will be merged.
    Entries are processed in the order in which they appear, and
    later entries can override earlier ones.</p>

    <p>For example:</p>
<pre>
    BrowserMatch ^Mozilla forms jpeg=yes browser=netscape
    BrowserMatch "^Mozilla/[2-3]" tables agif frames javascript
    BrowserMatch MSIE !javascript
 
</pre>

    <p>Note that the regular expression string is
    <strong>case-sensitive</strong>. For case-INsensitive matching,
    see the <a
    href="#browsermatchnocase"><samp>BrowserMatchNoCase</samp></a>
    directive.</p>

    <p>The <samp>BrowserMatch</samp> and
    <samp>BrowserMatchNoCase</samp> directives are special cases of
    the <a href="#setenvif"><samp>SetEnvIf</samp></a> and <a
    href="#setenvifnocase"><samp>SetEnvIfNoCase</samp></a>
    directives. The following two lines have the same effect:</p>
<pre>
   BrowserMatchNoCase Robot is_a_robot
   SetEnvIfNoCase User-Agent Robot is_a_robot
 
</pre>
    <hr />
    <!-- the HR is part of the directive description -->

    <h2><a id="browsermatchnocase"
    name="browsermatchnocase">BrowserMatchNoCase directive</a></h2>

    <p><a href="directive-dict.html#Syntax"
    rel="Help"><strong>Syntax:</strong></a> BrowserMatchNoCase
    <em>regex env-variable</em>[=<em>value</em>]
    [<em>env-variable</em>[=<em>value</em>]] ...<br />
     <a href="directive-dict.html#Default"
    rel="Help"><strong>Default:</strong></a> <em>none</em><br />
     <a href="directive-dict.html#Context"
    rel="Help"><strong>Context:</strong></a> server config, virtual
    host, directory, .htaccess<br />
     <a href="directive-dict.html#Override"
    rel="Help"><strong>Override:</strong></a> FileInfo<br />
     <a href="directive-dict.html#Status"
    rel="Help"><strong>Status:</strong></a> Base<br />
     <a href="directive-dict.html#Module"
    rel="Help"><strong>Module:</strong></a> mod_setenvif<br />
     <a href="directive-dict.html#Compatibility"
    rel="Help"><strong>Compatibility:</strong></a> Apache 1.2 and
    above (in Apache 1.2 this directive was found in the
    now-obsolete mod_browser module)</p>

    <p>The <samp>BrowserMatchNoCase</samp> directive is
    semantically identical to the <a
    href="#BrowserMatch"><samp>BrowserMatch</samp></a> directive.
    However, it provides for case-insensitive matching. For
    example:</p>
<pre>
    BrowserMatchNoCase mac platform=macintosh
    BrowserMatchNoCase win platform=windows
 
</pre>

    <p>The <samp>BrowserMatch</samp> and
    <samp>BrowserMatchNoCase</samp> directives are special cases of
    the <a href="#setenvif"><samp>SetEnvIf</samp></a> and <a
    href="#SetEnvIfNoCase"><samp>SetEnvIfNoCase</samp></a>
    directives. The following two lines have the same effect:</p>
<pre>
   BrowserMatchNoCase Robot is_a_robot
   SetEnvIfNoCase User-Agent Robot is_a_robot
 
</pre>
    <hr />
    <!-- the HR is part of the directive description -->

    <h2><a id="setenvif" name="setenvif">SetEnvIf
    directive</a></h2>

    <p><a href="directive-dict.html#Syntax"
    rel="Help"><strong>Syntax:</strong></a> SetEnvIf <em>attribute
    regex env-variable</em>[=<em>value</em>]
    [<em>env-variable</em>[=<em>value</em>]] ...<br />
     <a href="directive-dict.html#Default"
    rel="Help"><strong>Default:</strong></a> <em>none</em><br />
     <a href="directive-dict.html#Context"
    rel="Help"><strong>Context:</strong></a> server config, virtual
    host, directory, .htaccess<br />
     <a href="directive-dict.html#Override"
    rel="Help"><strong>Override:</strong></a> FileInfo<br />
     <a href="directive-dict.html#Status"
    rel="Help"><strong>Status:</strong></a> Base<br />
     <a href="directive-dict.html#Module"
    rel="Help"><strong>Module:</strong></a> mod_setenvif<br />
     <a href="directive-dict.html#Compatibility"
    rel="Help"><strong>Compatibility:</strong></a> Apache 1.3 and
    above; the Request_Protocol keyword and environment-variable
    matching are only available with 1.3.7 and later; use in
    .htaccess files only supported with 1.3.13 and later</p>

    <p>The <samp>SetEnvIf</samp> directive defines environment
    variables based on attributes of the request. These attributes
    can be the values of various HTTP request header fields (see <a
    href="http://www.rfc-editor.org/rfc/rfc2616.txt">RFC2616</a>
    for more information about these), or of other aspects of the
    request, including the following:</p>

    <ul>
      <li><samp>Remote_Host</samp> - the hostname (if available) of
      the client making the request</li>

      <li><samp>Remote_Addr</samp> - the IP address of the client
      making the request</li>

      <li><samp>Request_Method</samp> - the name of the method
      being used (<samp>GET</samp>, <samp>POST</samp>, <em>et
      cetera</em>)</li>

      <li><samp>Request_Protocol</samp> - the name and version of
      the protocol with which the request was made (<em>e.g.</em>,
      "HTTP/0.9", "HTTP/1.1", <em>etc.</em>)</li>

      <li><samp>Request_URI</samp> - the portion of the URL
      following the scheme and host portion</li>
    </ul>

    <p>Some of the more commonly used request header field names
    include <samp>Host</samp>, <samp>User-Agent</samp>, and
    <samp>Referer</samp>.</p>

    <p>If the <em>attribute</em> name doesn't match any of the
    special keywords, nor any of the request's header field names,
    it is tested as the name of an environment variable in the list
    of those associated with the request. This allows
    <code>SetEnvIf</code> directives to test against the result of
    prior matches.</p>

    <blockquote>
      <strong>Only those environment variables defined by earlier
      <code>SetEnvIf[NoCase]</code> directives are available for
      testing in this manner. 'Earlier' means that they were
      defined at a broader scope (such as server-wide) or
      previously in the current directive's scope.</strong>
    </blockquote>

    <p>Example:</p>
<pre>
   SetEnvIf Request_URI "\.gif$" object_is_image=gif
   SetEnvIf Request_URI "\.jpg$" object_is_image=jpg
   SetEnvIf Request_URI "\.xbm$" object_is_image=xbm
        :
   SetEnvIf Referer www\.mydomain\.com intra_site_referral
        :
   SetEnvIf object_is_image xbm XBIT_PROCESSING=1
 
</pre>

    <p>The first three will set the environment variable
    <samp>object_is_image</samp> if the request was for an image
    file, and the fourth sets <samp>intra_site_referral</samp> if
    the referring page was somewhere on the
    <samp>www.mydomain.com</samp> Web site.</p>
    <hr />
    <!-- the HR is part of the directive description -->

    <h2><a id="setenvifnocase" name="setenvifnocase">SetEnvIfNoCase
    directive</a></h2>

    <p><a href="directive-dict.html#Syntax"
    rel="Help"><strong>Syntax:</strong></a> SetEnvIfNoCase
    <em>attribute regex env-variable</em>[=<em>value</em>]
    [<em>env-variable</em>[=<em>value</em>]] ...<br />
     <a href="directive-dict.html#Default"
    rel="Help"><strong>Default:</strong></a> <em>none</em><br />
     <a href="directive-dict.html#Context"
    rel="Help"><strong>Context:</strong></a> server config, virtual
    host, directory, .htaccess<br />
     <a href="directive-dict.html#Override"
    rel="Help"><strong>Override:</strong></a> FileInfo<br />
     <a href="directive-dict.html#Status"
    rel="Help"><strong>Status:</strong></a> Base<br />
     <a href="directive-dict.html#Module"
    rel="Help"><strong>Module:</strong></a> mod_setenvif<br />
     <a href="directive-dict.html#Compatibility"
    rel="Help"><strong>Compatibility:</strong></a> Apache 1.3 and
    above; the Request_Protocol keyword and environment-variable
    matching are only available with 1.3.7 and later; use in
    .htaccess files only supported with 1.3.13 and later</p>

    <p>The <samp>SetEnvIfNoCase</samp> is semantically identical to
    the <a href="#setenvif"><samp>SetEnvIf</samp></a> directive,
    and differs only in that the regular expression matching is
    performed in a case-insensitive manner. For example:</p>
<pre>
   SetEnvIfNoCase Host Apache\.Org site=apache
 
</pre>

    <p>This will cause the <samp>site</samp> environment variable
    to be set to "<samp>apache</samp>" if the HTTP request header
    field <samp>Host:</samp> was included and contained
    <samp>Apache.Org</samp>, <samp>apache.org</samp>, or any other
    combination.</p>
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