env.html.en

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

        <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-gzip" id="force-gzip">force-gzip</a></h3>
        
          <p>If you have the <code>DEFLATE</code> filter activated, this
          environment variable will ignore the accept-encoding setting of
          your browser and will send compressed output unconditionally.</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; 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
        <code>DEFLATE</code> 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>. If you'd rather
        use statically compressed files, <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code>
        evaluates the variable as well (not only for gzip, but for all
        encodings that differ from "identity").</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 and
        <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code> will refuse to deliver encoded
        resources.</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 class="warning">
      <h3>Security note</h3>

      <p>Sending error pages without a specified character set may
      allow a cross-site-scripting attack for existing browsers (MSIE)
      which do not follow the HTTP/1.1 specification and attempt to
      "guess" the character set from the content.  Such browsers can
      be easily fooled into using the UTF-7 character set, and UTF-7
      content from input data (such as the request-URI) will not be
      escaped by the usual escaping mechanisms designed to prevent
      cross-site-scripting attacks.</p>
    </div>

   

   <h3><a name="proxy" id="proxy">force-proxy-request-1.0, proxy-nokeepalive, proxy-sendchunked,
   proxy-sendcl, proxy-chain-auth, proxy-interim-response, proxy-initial-not-pooled</a></h3>

   <p>These directives alter the protocol behavior of
   <code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code>.  See the <code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code> and <code class="module"><a href="./mod/mod_proxy_http.html">mod_proxy_http</a></code>
   documentation for more details.</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>Earlier versions recommended that the following lines be included in
        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"><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"><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>

    
    <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"><p><code>
          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;
          <span class="indent">
            Order Deny,Allow<br />
            Deny from all<br />
            Allow from env=local_referal
          </span>
          &lt;/Directory&gt;
        </code></p></div>

        <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>" tutorial on
  ServerWatch.</p>
    
  </div></div>
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