env.html.en

最新apache的源代码

    <h3><a name="url-rewriting" id="url-rewriting">URL Rewriting</a></h3>
        

        <p>The <code>%{ENV:...}</code> form of <em>TestString</em> in
        the <code class="directive"><a href="./mod/mod_rewrite.html#rewritecond">RewriteCond</a></code>
        allows mod_rewrite's rewrite
        engine to make decisions conditional on environment variables.
        Note that the variables accessible in mod_rewrite without the
        <code>ENV:</code> prefix are not actually environment
        variables. Rather, they are variables special to mod_rewrite
        which cannot be accessed from other modules.</p>
    
  </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="special" id="special">Special Purpose Environment Variables</a></h2>
    

        <p>Interoperability problems have led to the introduction of
        mechanisms to modify the way Apache behaves when talking to
        particular clients. To make these mechanisms as flexible as
        possible, they are invoked by defining environment variables,
        typically with <code class="directive"><a href="./mod/mod_setenvif.html#browsermatch">BrowserMatch</a></code>,
        though <code class="directive"><a href="./mod/mod_env.html#setenv">SetEnv</a></code> and 
        <code class="directive"><a href="./mod/mod_env.html#passenv">PassEnv</a></code> could also be used,
        for example.</p>

    <h3><a name="downgrade" id="downgrade">downgrade-1.0</a></h3>
        

        <p>This forces the request to be treated as a HTTP/1.0 request
        even if it was in a later dialect.</p>

    
    <h3><a name="force-no-vary" id="force-no-vary">force-no-vary</a></h3>
        

        <p>This causes any <code>Vary</code> fields to be removed from
        the response header before it is sent back to the client. Some
        clients don't interpret this field correctly (see the <a href="misc/known_client_problems.html">known client
        problems</a> page); setting this variable can work around this
        problem. Setting this variable also implies
        <strong>force-response-1.0</strong>.</p>

    
    <h3><a name="force-response" id="force-response">force-response-1.0</a></h3>
        

      <p>This forces an HTTP/1.0 response to clients making an HTTP/1.0
      request. It was originally
      implemented as a result of a problem with AOL's proxies. Some
      HTTP/1.0 clients may not behave correctly when given an HTTP/1.1
      response, and this can be used to interoperate with them.</p>

    

    <h3><a name="gzip-only-text-html" id="gzip-only-text-html">gzip-only-text/html</a></h3>
        

        <p>When set to a value of "1", this variable disables the DEFLATE
        output filter provided by <code class="module"><a href="./mod/mod_deflate.html">mod_deflate</a></code> for
        content-types other than <code>text/html</code>.</p>
    

    <h3><a name="no-gzip" id="no-gzip">no-gzip</a></h3>

        <p>When set, the <code>DEFLATE</code> filter of
        <code class="module"><a href="./mod/mod_deflate.html">mod_deflate</a></code> will be turned off.</p>

    

    <h3><a name="nokeepalive" id="nokeepalive">nokeepalive</a></h3>
        

        <p>This disables <code class="directive"><a href="./mod/core.html#keepalive">KeepAlive</a></code> when set.</p>

    

    <h3><a name="prefer-language" id="prefer-language">prefer-language</a></h3>

        <p>This influences <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code>'s behaviour. If
        it contains a language tag (such as <code>en</code>, <code>ja</code>
        or <code>x-klingon</code>), <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code> tries
        to deliver a variant with that language. If there's no such variant,
        the normal <a href="content-negotiation.html">negotiation</a> process
        applies.</p>

    

    <h3><a name="redirect-carefully" id="redirect-carefully">redirect-carefully</a></h3>
        

        <p>This forces the server to be more careful when sending a redirect
        to the client.  This is typically used when a client has a known
        problem handling redirects.  This was originally implemented as a
        result of a problem with Microsoft's WebFolders software which has
        a problem handling redirects on directory resources via DAV 
        methods.</p>

    

   <h3><a name="suppress-error-charset" id="suppress-error-charset">suppress-error-charset</a></h3>
       

    <p><em>Available in versions after 2.0.54</em></p>

    <p>When Apache issues a redirect in response to a client request,
    the response includes some actual text to be displayed in case
    the client can't (or doesn't) automatically follow the redirection.
    Apache ordinarily labels this text according to the character set
    which it uses, which is ISO-8859-1.</p>
    <p> However, if the redirection is to a page that uses a different
    character set, some broken browser versions will try to use the
    character set from the redirection text rather than the actual page.
    This can result in Greek, for instance, being incorrectly rendered.</p>
    <p>Setting this environment variable causes Apache to omit the character
    set for the redirection text, and these broken browsers will then correctly
    use that of the destination page.</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">Examples</a></h2>
    

    <h3><a name="misbehaving" id="misbehaving">Changing protocol behavior with misbehaving clients</a></h3>
        

        <p>We recommend that the following lines be included in
        httpd.conf to deal with known client problems.</p>
<div class="example"><pre>
#
# 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 grok 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</pre></div>

    
    <h3><a name="no-img-log" id="no-img-log">Do not log requests for images in the access log</a></h3>
        

        <p>This example keeps requests for images from appearing in the
        access log. It can be easily modified to prevent logging of
        particular directories, or to prevent logging of requests
        coming from particular hosts.</p>
    <div class="example"><pre>
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></div>

    
    <h3><a name="image-theft" id="image-theft">Prevent "Image Theft"</a></h3>
        

        <p>This example shows how to keep people not on your server
        from using images on your server as inline-images on their
        pages. This is not a recommended configuration, but it can work
        in limited circumstances. We assume that all your images are in
        a directory called /web/images.</p>
    <div class="example"><pre>
SetEnvIf Referer "^http://www.example.com/" local_referal
# Allow browsers that do not send Referer info
SetEnvIf Referer "^$" local_referal
&lt;Directory /web/images&gt;
   Order Deny,Allow
   Deny from all
   Allow from env=local_referal
&lt;/Directory&gt;</pre></div>

        <p>For more information about this technique, see the
        ApacheToday tutorial " <a href="http://apachetoday.com/news_story.php3?ltsn=2000-06-14-002-01-PS">
    Keeping Your Images from Adorning Other Sites</a>".</p>
    
  </div></div>
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