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little. PR: Obtained from: Submitted by: Reviewed by: git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@89387 13f79535-47bb-0310-9956-ffa450edef68
298 lines
9.7 KiB
HTML
298 lines
9.7 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<TITLE>Apache module mod_headers</TITLE>
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</HEAD>
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<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
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<BODY
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<!--#include virtual="header.html" -->
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<H1 ALIGN="CENTER">Module mod_headers</H1>
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<p>This module provides for the customization of HTTP request and
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response headers.</p>
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<P><A
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HREF="module-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> Extension
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<BR>
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<A
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HREF="module-dict.html#SourceFile"
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REL="Help"
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><STRONG>Source File:</STRONG></A> mod_headers.c
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<BR>
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<A
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HREF="module-dict.html#ModuleIdentifier"
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REL="Help"
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><STRONG>Module Identifier:</STRONG></A> headers_module
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<BR>
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<A
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HREF="module-dict.html#Compatibility"
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REL="Help"
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><STRONG>Compatibility:</STRONG></A> Available in Apache 1.2 and later.
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RequestHeader appeared in Apache 2.0.
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</P>
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<h2>Summary</h2>
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This module provides directives to control and modify HTTP
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request and response headers. Headers can be merged,
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replaced or removed.
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<H2>Directives</H2>
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<UL>
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<LI><A HREF="#requestheader">RequestHeader</A>
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<LI><A HREF="#header">Header</A>
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</UL>
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<H2>Order of Processing</H2>
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<p>The directives provided by mod_header can occur almost anywhere within
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the server configuration. They are valid in the main server config and virtual
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host sections, inside <Directory>, <Location> and <Files>
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sections, and within .htaccess files.</p>
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<P>The directives are processed in the following order:
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<OL>
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<LI>main server
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<LI>virtual host
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<LI><Directory> sections and .htaccess
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<LI><Location>
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<LI><Files>
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</OL>
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<p>Order is important. These two headers have a different effect if
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reversed:</p>
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<blockquote><code>
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RequestHeader append MirrorID "mirror 12"<br>
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RequestHeader unset MirrorID
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</code></blockquote>
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<p>This way round, the MirrorID header is not set. If reversed, the
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MirrorID header is set to "mirror 12".</P>
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<H2>Examples</H2>
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<OL>
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<LI>Copy all request headers that begin with "TS" to the response headers:</LI>
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<PRE>
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Header echo ^TS*
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</PRE>
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<LI>Add a header, MyHeader, to the response including a timestamp for when
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the request was received and how long it took to begin serving the
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request. This header can be used by the client to intuit load on
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the server or in isolating bottlenecks between the client and the
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server.</LI>
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<PRE>
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Header add MyHeader "%D %t"
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</PRE>
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results in this header being added to the response:
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<PRE>
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MyHeader: D=3775428 t=991424704447256
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</PRE>
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<LI>Say hello to Joe</LI>
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<PRE>
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Header add MyHeader "Hello Joe. It took %D microseconds for Apache to serve this request."
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</PRE>
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results in this header being added to the response:
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<PRE>
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MyHeader: Hello Joe. It took D=3775428 microseconds for Apache to serve this request.
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</PRE>
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<LI>Conditionally send MyHeader on the response if and only if header
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"MyRequestHeader" is present on the request. This is useful for
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constructing headers in response to some client stimulus. Note that
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this example requires the services of the mod_setenvif module.</LI>
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<PRE>
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SetEnvIf MyRequestHeader value HAVE_MyRequestHeader<BR>
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Header add MyHeader "%D %t mytext" env=HAVE_MyRequestHeader
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</PRE>
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If the header "MyRequestHeader: value" is present on the HTTP request, the response
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will contain the following header:
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<PRE>
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MyHeader: D=3775428 t=991424704447256 mytext
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</PRE>
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</OL>
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<HR>
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<H2><A NAME="requestheader">RequestHeader</A> directive</H2>
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> RequestHeader set|append|add
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<EM>header</EM> <EM>value</EM><BR>
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> RequestHeader unset <EM>header</EM><BR>
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<A
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HREF="directive-dict.html#Context"
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REL="Help"
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><STRONG>Context:</STRONG></A> server config, virtual host, access.conf,
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.htaccess<BR>
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<A
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HREF="directive-dict.html#Override"
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REL="Help"
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><STRONG>Override:</STRONG></A> FileInfo<BR>
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<A
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HREF="directive-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> Extension<BR>
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<A
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HREF="directive-dict.html#Module"
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REL="Help"
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><STRONG>Module:</STRONG></A> mod_header<P>
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<p>This directive can replace, merge or remove HTTP request
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headers. The header is modified just before the content handler is
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run, allowing incoming headers to be modified. The action it performs
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is determined by the first argument. This can be one of the following
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values:</p>
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<UL>
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<LI><STRONG>set</STRONG><BR>
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The request header is set, replacing any previous header with this name
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<LI><STRONG>append</STRONG><BR>
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The request header is appended to any existing header of the same
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name. When a new value is merged onto an existing header it is
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separated from the existing header with a comma. This is the HTTP standard
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way of giving a header multiple values.
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<LI><STRONG>add</STRONG><BR>
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The request header is added to the existing set of headers, even if
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this header already exists. This can result in two (or more) headers
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having the same name. This can lead to unforeseen consequences, and in
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general "append" should be used instead.
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<LI><STRONG>unset</STRONG><BR>
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The request header of this name is removed, if it exists. If there are
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multiple headers of the same name, all will be removed.
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</UL>
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<p>This argument is followed by a header name, which can include the
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final colon, but it is not required. Case is ignored. For
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<code>add</code>, <code>append</code> and <code>set</code> a value is
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given as the third argument. If this value contains spaces, it should
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be surrounded by double quotes. For unset, no value should be
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given.</p>
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<p>The <code>RequestHeader</code> directive is processed just before
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the request is run by its handler in the fixup phase. This should
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allow headers generated by the browser, or by Apache input filters to
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be overridden or modified.</p>
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<HR>
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<H2><A NAME="header">Header</A> directive</H2>
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> Header set|append|add
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<EM>header</EM> <EM>value</EM> <EM>[env=[!]environment-variable]</EM><BR>
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> Header unset <EM>header</EM><BR>
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> Header echo <EM>header</EM><BR>
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<A
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HREF="directive-dict.html#Context"
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REL="Help"
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><STRONG>Context:</STRONG></A> server config, virtual host, access.conf,
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.htaccess<BR>
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<A
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HREF="directive-dict.html#Override"
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REL="Help"
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><STRONG>Override:</STRONG></A> FileInfo<BR>
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<A
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HREF="directive-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> Extension<BR>
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<A
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HREF="directive-dict.html#Module"
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REL="Help"
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><STRONG>Module:</STRONG></A> mod_header<P>
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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 and
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output filters are run, allowing outgoing headers to be modified. The
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action it performs is determined by the first argument. This can be
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one of the following values:</p>
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<UL>
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<LI><STRONG>set</STRONG><BR>
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The response header is set, replacing any previous header with this name.
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The <EM>value</EM> may be a format string.
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<LI><STRONG>append</STRONG><BR>
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The response header is appended to any existing header of the same
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name. When a new value is merged onto an existing header it is
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separated from the existing header with a comma. This is the HTTP standard
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way of giving a header multiple values.
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<LI><STRONG>add</STRONG><BR>
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The response header is added to the existing set of headers, even if
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this header already exists. This can result in two (or more) headers
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having the same name. This can lead to unforeseen consequences, and in
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general "append" should be used instead.
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<LI><STRONG>unset</STRONG><BR>
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The response header of this name is removed, if it exists. If there are
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multiple headers of the same name, all will be removed.
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<LI><STRONG>echo</STRONG><BR>
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Request headers with this name are echoed back in the response headers.
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<EM>header</EM> may be a regular expression.
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</UL>
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<p>This argument is followed by a <EM>header</EM> name, which can include the
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final colon, but it is not required. Case is ignored for set, append, add
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and unset. The <EM>header</EM> name for echo is case sensitive and may be a
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regular expression.</p>
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<P>For <code>add</code>, <code>append</code> and <code>set</code> a
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<EM>value</EM> is specified as the third argument. If <EM>value</EM>
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contains spaces, it should be surrounded by doublequotes.
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<EM>value</EM> may be a character string, a string containing format
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specifiers or a combination of both. The following format specifiers
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are supported in <EM>value</EM>:
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<PRE>
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%t: The time the request was received in Universal Coordinated Time
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since the epoch (Jan. 1, 1970) measured in microseconds. The
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value is preceeded by "t=".
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%D: The time from when the request was received to the time the
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headers are sent on the wire. This is a measure of the
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duration of the request. The value is preceeded by "D=".
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</PRE>
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<p>When the <code>Header</code> directive is used with the
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<code>add</code>, <code>append</code>, or <code>set</code> argument, a
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fourth argument may be used to specify conditions under which the
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action will be taken. If the <a href="../env.html">environment
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variable</a> specified in the <code>env=...</code> argument exists (or
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if the environment variable does not exist and <code>env=!...</code>
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is specified) then the action specified by the <code>Header</code>
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directive will take effect. Otherwise, the directive will have no
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effect on the request.</p>
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<p>The Header directives are processed just before the response is
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sent to the network. These means that it is possible to set and/or
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override most headers, except for those headers added by the header
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filter.</p>
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<!--#include virtual="footer.html" -->
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</BODY>
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</HTML>
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