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612 lines
34 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head>
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<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" />
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<!--
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<title>mod_headers - Apache HTTP Server Version 2.5</title>
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<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
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<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
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<script src="../style/scripts/prettify.min.js" type="text/javascript">
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</script>
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<link href="../images/favicon.ico" rel="shortcut icon" /></head>
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<body>
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<div id="page-header">
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.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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<p class="apache">Apache HTTP Server Version 2.5</p>
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<img alt="" src="../images/feather.png" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<div id="path">
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.5</a> > <a href="./">Modules</a></div>
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<div id="page-content">
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<div id="preamble"><h1>Apache Module mod_headers</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_headers.html" title="English"> en </a> |
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<a href="../fr/mod/mod_headers.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
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<a href="../ja/mod/mod_headers.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
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<a href="../ko/mod/mod_headers.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
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</div>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Customization of HTTP request and response
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headers</td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>headers_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_headers.c</td></tr></table>
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<h3>Summary</h3>
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<p>This module provides directives to control and modify HTTP
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request and response headers. Headers can be merged, replaced
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or removed.</p>
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</div>
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<div id="quickview"><h3>Topics</h3>
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<ul id="topics">
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<li><img alt="" src="../images/down.gif" /> <a href="#order">Order of Processing</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#early">Early and Late Processing</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#examples">Examples</a></li>
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</ul><h3 class="directives">Directives</h3>
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<ul id="toc">
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<li><img alt="" src="../images/down.gif" /> <a href="#header">Header</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#requestheader">RequestHeader</a></li>
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</ul>
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<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_headers">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_headers">Report a bug</a></li></ul><h3>See also</h3>
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<ul class="seealso">
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<li><a href="#comments_section">Comments</a></li></ul></div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="order" id="order">Order of Processing</a> <a title="Permanent link" href="#order" class="permalink">¶</a></h2>
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||
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<p>The directives provided by <code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code> can
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||
occur almost anywhere within the server configuration, and can be
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||
limited in scope by enclosing them in <a href="../sections.html">configuration sections</a>.</p>
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||
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<p>Order of processing is important and is affected both by the
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order in the configuration file and by placement in <a href="../sections.html#mergin">configuration sections</a>. These
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two directives have a different effect if reversed:</p>
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||
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<pre class="prettyprint lang-config">RequestHeader append MirrorID "mirror 12"
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RequestHeader unset MirrorID</pre>
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||
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||
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<p>This way round, the <code>MirrorID</code> header is not set. If
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||
reversed, the MirrorID header is set to "mirror 12".</p>
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||
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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||
<div class="section">
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||
<h2><a name="early" id="early">Early and Late Processing</a> <a title="Permanent link" href="#early" class="permalink">¶</a></h2>
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<p><code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code> can be applied either early or late
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in the request. The normal mode is late, when <em>Request</em> Headers are
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set immediately before running the content generator and <em>Response</em>
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Headers just as the response is sent down the wire. Always use
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Late mode in an operational server.</p>
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<p>Early mode is designed as a test/debugging aid for developers.
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Directives defined using the <code>early</code> keyword are set
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right at the beginning of processing the request. This means
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they can be used to simulate different requests and set up test
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cases, but it also means that headers may be changed at any time
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by other modules before generating a Response.</p>
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<p>Because early directives are processed before the request path's
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configuration is traversed, early headers can only be set in a
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main server or virtual host context. Early directives cannot depend
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on a request path, so they will fail in contexts such as
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<code class="directive"><a href="../mod/core.html#directory"><Directory></a></code> or
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<code class="directive"><a href="../mod/core.html#location"><Location></a></code>.</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="examples" id="examples">Examples</a> <a title="Permanent link" href="#examples" class="permalink">¶</a></h2>
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<ol>
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<li>
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Copy all request headers that begin with "TS" to the
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response headers:
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<pre class="prettyprint lang-config">Header echo ^TS</pre>
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</li>
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<li>
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Add a header, <code>MyHeader</code>, to the response including a
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timestamp for when the request was received and how long it
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took to begin serving the request. This header can be used by
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the client to intuit load on the server or in isolating
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bottlenecks between the client and the server.
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<pre class="prettyprint lang-config">Header set MyHeader "%D %t"</pre>
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<p>results in this header being added to the response:</p>
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<div class="example"><p><code>
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MyHeader: D=3775428 t=991424704447256
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</code></p></div>
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</li>
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<li>
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Say hello to Joe
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<pre class="prettyprint lang-config">Header set MyHeader "Hello Joe. It took %D microseconds for Apache to serve this request."</pre>
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<p>results in this header being added to the response:</p>
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<div class="example"><p><code>
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MyHeader: Hello Joe. It took D=3775428 microseconds for Apache
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to serve this request.
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</code></p></div>
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</li>
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<li>
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Conditionally send <code>MyHeader</code> on the response if and
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only if header <code>MyRequestHeader</code> is present on the request.
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This is useful for constructing headers in response to some client
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stimulus. Note that this example requires the services of the
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<code class="module"><a href="../mod/mod_setenvif.html">mod_setenvif</a></code> module.
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<pre class="prettyprint lang-config">SetEnvIf MyRequestHeader myvalue HAVE_MyRequestHeader
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Header set MyHeader "%D %t mytext" env=HAVE_MyRequestHeader</pre>
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<p>If the header <code>MyRequestHeader: myvalue</code> is present on
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the HTTP request, the response will contain the following header:</p>
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<div class="example"><p><code>
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MyHeader: D=3775428 t=991424704447256 mytext
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</code></p></div>
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</li>
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<li>
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Enable DAV to work with Apache running HTTP through SSL hardware
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(<a href="http://svn.haxx.se/users/archive-2006-03/0549.shtml">problem
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description</a>) by replacing <var>https:</var> with
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<var>http:</var> in the <var>Destination</var> header:
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<pre class="prettyprint lang-config">RequestHeader edit Destination ^https: http: early</pre>
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</li>
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<li>
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Set the same header value under multiple nonexclusive conditions,
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but do not duplicate the value in the final header.
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If all of the following conditions applied to a request (i.e.,
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if the <code>CGI</code>, <code>NO_CACHE</code> and
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<code>NO_STORE</code> environment variables all existed for the
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request):
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<pre class="prettyprint lang-config">Header merge Cache-Control no-cache env=CGI
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Header merge Cache-Control no-cache env=NO_CACHE
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Header merge Cache-Control no-store env=NO_STORE</pre>
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<p>then the response would contain the following header:</p>
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<div class="example"><p><code>
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Cache-Control: no-cache, no-store
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</code></p></div>
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<p>If <code>append</code> was used instead of <code>merge</code>,
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then the response would contain the following header:</p>
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<div class="example"><p><code>
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Cache-Control: no-cache, no-cache, no-store
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</code></p></div>
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</li>
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<li>
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Set a test cookie if and only if the client didn't send us a cookie
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<pre class="prettyprint lang-config">Header set Set-Cookie testcookie "expr=-z %{req:Cookie}"</pre>
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</li>
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<li>
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Append a Caching header for responses with a HTTP status code of 200
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<pre class="prettyprint lang-config">Header append Cache-Control s-maxage=600 "expr=%{REQUEST_STATUS} == 200"</pre>
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||
</li>
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||
</ol>
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||
</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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||
<div class="directive-section"><h2><a name="Header" id="Header">Header</a> <a name="header" id="header">Directive</a> <a title="Permanent link" href="#header" class="permalink">¶</a></h2>
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<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure HTTP response headers</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Header [<var>condition</var>] add|append|echo|edit|edit*|merge|set|setifempty|unset|note
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<var>header</var> [[expr=]<var>value</var> [<var>replacement</var>]
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[early|env=[!]<var>varname</var>|expr=<var>expression</var>]]
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</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_headers</td></tr>
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<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>SetIfEmpty available in 2.4.7 and later, expr=value
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available in 2.4.10 and later</td></tr>
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||
</table>
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<p>This directive can replace, merge or remove HTTP response
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headers. The header is modified just after the content handler
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and output filters are run, allowing outgoing headers to be
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modified.</p>
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<p> The optional <var>condition</var> argument determines which internal
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table of responses headers this directive will operate against:
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<code>onsuccess</code> (default, can be omitted) or <code>always</code>.
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Guidance on when to specify <code>always</code> is provided relative to each
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action below. </p>
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<div class="warning"><h3>Warning</h3>
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<p>Carefully read the difference between <code>always</code>
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and <code>onsuccess</code> for each action listed below as the
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behavior can be unintuitive and is a frequent source of confusion.
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Where the guidance suggest repeating the conditions, it is safe to try
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each experimentally and use the one you find effective to match the
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pre-existing header.</p>
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</div>
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<dl>
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<dt><code>add</code></dt>
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<dd>The response header is added to the existing set of headers,
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even if this header already exists. This can result in two
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(or more) headers having the same name. This can lead to
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unforeseen consequences, and in general <code>set</code>,
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<code>append</code> or <code>merge</code> should be used instead.
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<br /><br /><p>Choosing a <var>condition</var>: Specify a condition of <code>always</code> if you want the header to
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be included in non-2xx response (such as redirects or errors)</p>
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</dd>
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<dt><code>append</code></dt>
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<dd>The response header is appended to any existing header of
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the same name. When a new value is merged onto an existing
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header it is separated from the existing header with a comma.
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This is the HTTP standard way of giving a header multiple values.
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<br /><br /><p>Choosing a <var>condition</var>: If the existing header to be appended to was added by this module, you must match the condition
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parameter that was originally used. Otherwise, you must determine by trial
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and error whether <code>always</code> should be specified because you can't
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reliably know which internal table the existing value is present in.</p>
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||
</dd>
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<dt><code>echo</code></dt>
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<dd>Request headers with this name are echoed back in the
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response headers. <var>header</var> may be a
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<a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>.
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<var>value</var> must be omitted.
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<br /><br /><p>Choosing a <var>condition</var>: Specify a condition of <code>always</code> if you want the header to
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be included in non-2xx response (such as redirects or errors).</p>
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||
</dd>
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<dt><code>edit</code></dt>
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<dt><code>edit*</code></dt>
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<dd>If this response header exists, its value is transformed according
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||
to a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>
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search-and-replace. The <var>value</var> argument is a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>, and the <var>replacement</var>
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||
is a replacement string, which may contain backreferences or format specifiers.
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||
The <code>edit</code> form will match and replace exactly once
|
||
in a header value, whereas the <code>edit*</code> form will replace
|
||
<em>every</em> instance of the search pattern if it appears more
|
||
than once.
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||
<br /><br /><p>Choosing a <var>condition</var>: Depending on the origins of the header to be edited,
|
||
you may have to repeat your edit/edit* directive with both <code>always</code> and
|
||
<code>onsuccess</code>. Alternatively, determine by experimentation
|
||
whether a condition of <code>always</code> is necessary.</p>
|
||
</dd>
|
||
|
||
<dt><code>merge</code></dt>
|
||
<dd>The response header is appended to any existing header of
|
||
the same name, unless the value to be appended already appears in the
|
||
header's comma-delimited list of values. When a new value is merged onto
|
||
an existing header it is separated from the existing header with a comma.
|
||
This is the HTTP standard way of giving a header multiple values.
|
||
Values are compared in a case sensitive manner, and after
|
||
all format specifiers have been processed. Values in double quotes
|
||
are considered different from otherwise identical unquoted values.
|
||
<br /><br /><p>Choosing a <var>condition</var>: If the target header to be merged was added by this module, you must match the condition
|
||
parameter that was originally used. Otherwise, you must determine by experimentation
|
||
whether a condition of <code>always</code> is necessary.</p>
|
||
</dd>
|
||
|
||
|
||
<dt><code>set</code></dt>
|
||
<dd>The response header is set, replacing any previous header
|
||
with this name. The <var>value</var> may be a format string.
|
||
<br /><br /><p>Choosing a <var>condition</var>: If the target header to be replaced was added by this module, you must match the condition
|
||
parameter that was originally used. Otherwise, you must determine by experimentation
|
||
whether a condition <code>always</code> is necessary.</p>
|
||
</dd>
|
||
|
||
|
||
<dt><code>setifempty</code></dt>
|
||
<dd>The request header is set, but only if there is no previous header
|
||
with this name.
|
||
<br /><br /><p>Choosing a <var>condition</var>: If the target header to conditionally set was added by this module, you must match the condition
|
||
parameter that was originally used. Otherwise, you must determine by experimentation
|
||
whether a condition of <code>always</code> is necessary.</p>
|
||
|
||
<div class="note">
|
||
The Content-Type header is a special use case since there might be
|
||
the chance that its value have been determined but the header is not part
|
||
of the response when <code>setifempty</code> is evaluated.
|
||
It is safer to use <code>set</code> for this use case like in the
|
||
following example:
|
||
<pre class="prettyprint lang-config">Header set Content-Type "text/plain" "expr=-z %{CONTENT_TYPE}"</pre>
|
||
|
||
</div></dd>
|
||
|
||
|
||
<dt><code>unset</code></dt>
|
||
<dd>The response header of this name is removed, if it exists.
|
||
If there are multiple headers of the same name, all will be
|
||
removed. <var>value</var> must be omitted.
|
||
<br /><br /><p>Choosing a <var>condition</var>: Repeat this directive with both <code>always</code> and
|
||
<code>onsuccess</code> to be certain the header is unset, or determine by experimentation
|
||
whether a condition of <code>always</code> is necessary..</p>
|
||
</dd>
|
||
|
||
<dt><code>note</code></dt>
|
||
<dd>The value of the named response <var>header</var> is copied into an
|
||
internal note whose name is given by <var>value</var>. This is useful
|
||
if a header sent by a CGI or proxied resource is configured to be unset
|
||
but should also be logged.<br />
|
||
Available in 2.4.7 and later.
|
||
<br /><br /><p>Choosing a <var>condition</var>: If the target header was added by this module, you must match the condition
|
||
parameter that was originally used. Otherwise, you must determine by experimentation
|
||
whether a condition of <code>always</code> is necessary..</p>
|
||
</dd>
|
||
|
||
</dl>
|
||
|
||
<p>This argument is followed by a <var>header</var> name, which
|
||
can include the final colon, but it is not required. Case is
|
||
ignored for <code>set</code>, <code>append</code>, <code>merge</code>,
|
||
<code>add</code>, <code>unset</code> and <code>edit</code>.
|
||
The <var>header</var> name for <code>echo</code>
|
||
is case sensitive and may be a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
|
||
expression</a>.</p>
|
||
|
||
<p>For <code>set</code>, <code>append</code>, <code>merge</code> and
|
||
<code>add</code> a <var>value</var> is specified as the next argument.
|
||
If <var>value</var>
|
||
contains spaces, it should be surrounded by double quotes.
|
||
<var>value</var> may be a character string, a string containing
|
||
<code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code> specific format specifiers (and character
|
||
literals), or an <a href="../expr.html">ap_expr</a> expression prefixed
|
||
with <em>expr=</em></p>
|
||
|
||
<p> The following format specifiers are supported in <var>value</var>:</p>
|
||
|
||
<table class="bordered"><tr class="header"><th>Format</th><th>Description</th></tr>
|
||
<tr><td><code>%%</code></td>
|
||
<td>The percent sign</td></tr>
|
||
<tr class="odd"><td><code>%t</code></td>
|
||
<td>The time the request was received in Universal Coordinated Time
|
||
since the epoch (Jan. 1, 1970) measured in microseconds. The value
|
||
is preceded by <code>t=</code>.</td></tr>
|
||
<tr><td><code>%D</code></td>
|
||
<td>The time from when the request was received to the time the
|
||
headers are sent on the wire. This is a measure of the duration
|
||
of the request. The value is preceded by <code>D=</code>.
|
||
The value is measured in microseconds.</td></tr>
|
||
<tr class="odd"><td><code>%l</code></td>
|
||
<td>The current load averages of the actual server itself. It is
|
||
designed to expose the values obtained by <code>getloadavg()</code>
|
||
and this represents the current load average, the 5 minute average, and
|
||
the 15 minute average. The value is preceded by <code>l=</code> with each
|
||
average separated by <code>/</code>.<br />
|
||
Available in 2.4.4 and later.
|
||
</td></tr>
|
||
<tr><td><code>%i</code></td>
|
||
<td>The current idle percentage of httpd (0 to 100) based on available
|
||
processes and threads. The value is preceded by <code>i=</code>.<br />
|
||
Available in 2.4.4 and later.
|
||
</td></tr>
|
||
<tr class="odd"><td><code>%b</code></td>
|
||
<td>The current busy percentage of httpd (0 to 100) based on available
|
||
processes and threads. The value is preceded by <code>b=</code>.<br />
|
||
Available in 2.4.4 and later.
|
||
</td></tr>
|
||
<tr><td><code>%{VARNAME}e</code></td>
|
||
<td>The contents of the <a href="../env.html">environment
|
||
variable</a> <code>VARNAME</code>.</td></tr>
|
||
<tr class="odd"><td><code>%{VARNAME}s</code></td>
|
||
<td>The contents of the <a href="mod_ssl.html#envvars">SSL environment
|
||
variable</a> <code>VARNAME</code>, if <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> is enabled.</td></tr>
|
||
</table>
|
||
|
||
<div class="note"><h3>Note</h3>
|
||
<p>The <code>%s</code> format specifier is only available in
|
||
Apache 2.1 and later; it can be used instead of <code>%e</code>
|
||
to avoid the overhead of enabling <code>SSLOptions
|
||
+StdEnvVars</code>. If <code>SSLOptions +StdEnvVars</code> must
|
||
be enabled anyway for some other reason, <code>%e</code> will be
|
||
more efficient than <code>%s</code>.</p>
|
||
</div>
|
||
|
||
<div class="note"><h3>Note on expression values</h3>
|
||
<p> When the value parameter uses the <a href="../expr.html">ap_expr</a>
|
||
parser, some expression syntax will differ from examples that evaluate
|
||
<em>boolean</em> expressions such as <If>:</p>
|
||
<ul>
|
||
<li>The starting point of the grammar is 'string' rather than 'expr'.</li>
|
||
<li>Function calls use the %{funcname:arg} syntax rather than
|
||
funcname(arg).</li>
|
||
<li>Multi-argument functions are not currently accessible from this
|
||
starting point</li>
|
||
<li>Quote the entire parameter, such as
|
||
<pre class="prettyprint lang-config">Header set foo-checksum "expr=%{md5:foo}"</pre>
|
||
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
<p>For <code>edit</code> there is both a <var>value</var> argument
|
||
which is a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>,
|
||
and an additional <var>replacement</var> string. As of version 2.4.7
|
||
the replacement string may also contain format specifiers.</p>
|
||
|
||
<p>The <code class="directive">Header</code> directive may be followed by
|
||
an additional argument, which may be any of:</p>
|
||
<dl>
|
||
<dt><code>early</code></dt>
|
||
<dd>Specifies <a href="#early">early processing</a>.</dd>
|
||
<dt><code>env=[!]<var>varname</var></code></dt>
|
||
<dd>The directive is applied if and only if the <a href="../env.html">environment variable</a> <code>varname</code> exists.
|
||
A <code>!</code> in front of <code>varname</code> reverses the test,
|
||
so the directive applies only if <code>varname</code> is unset.</dd>
|
||
<dt><code>expr=<var>expression</var></code></dt>
|
||
<dd>The directive is applied if and only if <var>expression</var>
|
||
evaluates to true. Details of expression syntax and evaluation are
|
||
documented in the <a href="../expr.html">ap_expr</a> documentation.
|
||
<pre class="prettyprint lang-config"># This delays the evaluation of the condition clause compared to <If>
|
||
Header always set CustomHeader my-value "expr=%{REQUEST_URI} =~ m#^/special_path.php$#"</pre>
|
||
|
||
</dd>
|
||
</dl>
|
||
|
||
<p>Except in <a href="#early">early</a> mode, the
|
||
<code class="directive">Header</code> directives are processed just
|
||
before the response is sent to the network. This means that it is
|
||
possible to set and/or override most headers, except for some headers
|
||
added by the HTTP header filter. Prior to 2.2.12, it was not possible
|
||
to change the Content-Type header with this directive.</p>
|
||
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="RequestHeader" id="RequestHeader">RequestHeader</a> <a name="requestheader" id="requestheader">Directive</a> <a title="Permanent link" href="#requestheader" class="permalink">¶</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure HTTP request headers</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RequestHeader add|append|edit|edit*|merge|set|setifempty|unset
|
||
<var>header</var> [[expr=]<var>value</var> [<var>replacement</var>]
|
||
[early|env=[!]<var>varname</var>|expr=<var>expression</var>]]
|
||
</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
|
||
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_headers</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>SetIfEmpty available in 2.4.7 and later, expr=value
|
||
available in 2.4.10 and later</td></tr>
|
||
</table>
|
||
<p>This directive can replace, merge, change or remove HTTP request
|
||
headers. The header is modified just before the content handler
|
||
is run, allowing incoming headers to be modified. The action it
|
||
performs is determined by the first argument. This can be one
|
||
of the following values:</p>
|
||
|
||
<dl>
|
||
|
||
<dt><code>add</code></dt>
|
||
<dd>The request header is added to the existing set of headers,
|
||
even if this header already exists. This can result in two
|
||
(or more) headers having the same name. This can lead to
|
||
unforeseen consequences, and in general <code>set</code>,
|
||
<code>append</code> or <code>merge</code> should be used instead.</dd>
|
||
|
||
<dt><code>append</code></dt>
|
||
<dd>The request header is appended to any existing header of the
|
||
same name. When a new value is merged onto an existing header
|
||
it is separated from the existing header with a comma. This
|
||
is the HTTP standard way of giving a header multiple
|
||
values.</dd>
|
||
|
||
<dt><code>edit</code></dt>
|
||
<dt><code>edit*</code></dt>
|
||
<dd>If this request header exists, its value is transformed according
|
||
to a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>
|
||
search-and-replace. The <var>value</var> argument is a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>, and the <var>replacement</var>
|
||
is a replacement string, which may contain backreferences or format specifiers.
|
||
The <code>edit</code> form will match and replace exactly once
|
||
in a header value, whereas the <code>edit*</code> form will replace
|
||
<em>every</em> instance of the search pattern if it appears more
|
||
than once.</dd>
|
||
|
||
<dt><code>merge</code></dt>
|
||
<dd>The request header is appended to any existing header of
|
||
the same name, unless the value to be appended already appears in the
|
||
existing header's comma-delimited list of values. When a new value is
|
||
merged onto an existing header it is separated from the existing header
|
||
with a comma. This is the HTTP standard way of giving a header multiple
|
||
values. Values are compared in a case sensitive manner, and after
|
||
all format specifiers have been processed. Values in double quotes
|
||
are considered different from otherwise identical unquoted values.</dd>
|
||
|
||
<dt><code>set</code></dt>
|
||
<dd>The request header is set, replacing any previous header
|
||
with this name</dd>
|
||
|
||
<dt><code>setifempty</code></dt>
|
||
<dd>The request header is set, but only if there is no previous header
|
||
with this name.<br />
|
||
Available in 2.4.7 and later.</dd>
|
||
|
||
<dt><code>unset</code></dt>
|
||
<dd>The request header of this name is removed, if it exists. If
|
||
there are multiple headers of the same name, all will be removed.
|
||
<var>value</var> must be omitted.</dd>
|
||
</dl>
|
||
|
||
<p>This argument is followed by a header name, which can
|
||
include the final colon, but it is not required. Case is
|
||
ignored. For <code>set</code>, <code>append</code>, <code>merge</code> and
|
||
<code>add</code> a <var>value</var> is given as the third argument. If a
|
||
<var>value</var> contains spaces, it should be surrounded by double
|
||
quotes. For <code>unset</code>, no <var>value</var> should be given.
|
||
<var>value</var> may be a character string, a string containing format
|
||
specifiers or a combination of both. The supported format specifiers
|
||
are the same as for the <code class="directive"><a href="#header">Header</a></code>,
|
||
please have a look there for details. For <code>edit</code> both
|
||
a <var>value</var> and a <var>replacement</var> are required, and are
|
||
a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a> and a
|
||
replacement string respectively.</p>
|
||
|
||
<p>The <code class="directive">RequestHeader</code> directive may be followed by
|
||
an additional argument, which may be any of:</p>
|
||
<dl>
|
||
<dt><code>early</code></dt>
|
||
<dd>Specifies <a href="#early">early processing</a>.</dd>
|
||
<dt><code>env=[!]<var>varname</var></code></dt>
|
||
<dd>The directive is applied if and only if the <a href="../env.html">environment variable</a> <code>varname</code> exists.
|
||
A <code>!</code> in front of <code>varname</code> reverses the test,
|
||
so the directive applies only if <code>varname</code> is unset.</dd>
|
||
<dt><code>expr=<var>expression</var></code></dt>
|
||
<dd>The directive is applied if and only if <var>expression</var>
|
||
evaluates to true. Details of expression syntax and evaluation are
|
||
documented in the <a href="../expr.html">ap_expr</a> documentation.</dd>
|
||
</dl>
|
||
|
||
<p>Except in <a href="#early">early</a> mode, the
|
||
<code class="directive">RequestHeader</code> directive is processed
|
||
just before the request is run by its handler in the fixup phase.
|
||
This should allow headers generated by the browser, or by Apache
|
||
input filters to be overridden or modified.</p>
|
||
|
||
</div>
|
||
</div>
|
||
<div class="bottomlang">
|
||
<p><span>Available Languages: </span><a href="../en/mod/mod_headers.html" title="English"> en </a> |
|
||
<a href="../fr/mod/mod_headers.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
|
||
<a href="../ja/mod/mod_headers.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
|
||
<a href="../ko/mod/mod_headers.html" hreflang="ko" rel="alternate" title="Korean"> ko </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&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed 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 Libera.chat, or sent to our <a href="https://httpd.apache.org/lists.html">mailing lists</a>.</div>
|
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d.write('<div id="comments_thread"><\/div>');
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<p class="apache">Copyright 2023 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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