Commit b74e5993 authored by Joshua Slive's avatar Joshua Slive
Browse files

Bring these docs into line with "The Standard" and clean them up a 

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
parent b6ef3427

docs/manual/mod/mod_headers.html

+110 −123
Original line number Diff line number Diff line
@@ -15,7 +15,7 @@ 
<!--#include virtual="header.html" -->

<H1 ALIGN="CENTER">Module mod_headers</H1>



<p>This module provides for the customization of HTTP

<p>This module provides for the customization of HTTP request and

response headers.</p>



<P><A
@@ -52,6 +52,76 @@ replaced or removed. 
<LI><A HREF="#header">Header</A>

</UL>



<H2>Order of Processing</H2>



<p>The directives provided by mod_header can occur almost anywhere within 

the server configuration. They are valid in the main server config and virtual 

host sections, inside &lt;Directory&gt;, &lt;Location&gt; and &lt;Files&gt;

sections, and within .htaccess files.</p>



<P>The directives are processed in the following order:

<OL>

<LI>main server

<LI>virtual host

<LI>&lt;Directory&gt; sections and .htaccess

<LI>&lt;Location&gt;

<LI>&lt;Files&gt;

</OL>



<p>Order is important. These two headers have a different effect if

reversed:</p>



<blockquote><code>

RequestHeader append MirrorID "mirror 12"<br>

RequestHeader unset MirrorID

</code></blockquote>



<p>This way round, the MirrorID header is not set. If reversed, the

MirrorID header is set to "mirror 12".</P>



<H2>Examples</H2>

<OL>

<LI>Copy all request headers that begin with "TS" to the response headers:</LI>

<PRE>

   Header echo ^TS*

</PRE>



<LI>Add a header, MyHeader, to the response including a timestamp for when

the request was received and how long it took to begin serving the

request. This header can be used by the client to intuit load on

the server or in isolating bottlenecks between the client and the

server.</LI>

<PRE>

   Header add MyHeader "%D %t"

</PRE>

results in this header being added to the response:

<PRE>

   MyHeader: D=3775428 t=991424704447256

</PRE>

<LI>Say hello to Joe</LI>

<PRE>

   Header add MyHeader "Hello Joe. It took %D microseconds for Apache to serve this request."

</PRE>

results in this header being added to the response:

<PRE>

   MyHeader: Hello Joe. It took D=3775428 microseconds for Apache to serve this request.

</PRE>



<LI>Conditionally send MyHeader on the response if and only if header

"MyRequestHeader" is present on the request. This is useful for

constructing headers in response to some client stimulus. Note that

this example requires the services of the mod_setenvif module.</LI>

<PRE>

   SetEnvIf MyRequestHeader value HAVE_MyRequestHeader<BR>

   Header add MyHeader "%D %t mytext" env=HAVE_MyRequestHeader

</PRE> 

If the header "MyRequestHeader: value" is present on the HTTP request, the response

will contain the following header:

<PRE>

   MyHeader: D=3775428 t=991424704447256 mytext

</PRE>

</OL>



<HR>



<H2><A NAME="requestheader">RequestHeader</A> directive</H2>
@@ -82,10 +152,11 @@ replaced or removed. 
 REL="Help"

><STRONG>Module:</STRONG></A> mod_header<P>



This directive can replace, merge 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>This directive can replace, merge 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>



<UL>

<LI><STRONG>set</STRONG><BR>
@@ -108,42 +179,17 @@ argument. This can be one of the following values: 
  multiple headers of the same name, all will be removed.

</UL>



This argument is followed by a header name, which can include the

<p>This argument is followed by a header name, which can include the

final colon, but it is not required. Case is ignored. For

add, append and set a value is given as the third argument. If this

value contains spaces, it should be surrounded by double quotes.

For unset, no value should be given.



<H3>Order of Processing</H3>



The RequestHeader (and Header) directives can occur almost anywhere within 

the server configuration. It is valid in the main server config and virtual 

host sections, inside &lt;Directory&gt;, &lt;Location&gt; and &lt;Files&gt;

sections, and within .htaccess files.

<P>

The RequestHeader directives are processed in the following order:

<OL>

<LI>main server

<LI>virtual host

<LI>&lt;Directory&gt; sections and .htaccess

<LI>&lt;Location&gt;

<LI>&lt;Files&gt;

</OL>

<code>add</code>, <code>append</code> and <code>set</code> a value is

given as the third argument. If this value contains spaces, it should

be surrounded by double quotes.  For unset, no value should be

given.</p>



Order is important. These two headers have a different effect if reversed:

<PRE>

RequestHeader append MirrorID "mirror 12"

RequestHeader unset MirrorID

</PRE>



This way round, the MirrorID header is not set. If reversed, the MirrorID

header is set to "mirror 12".

<P>



The RequestHeader 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>

<p>The <code>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>



<HR>
@@ -179,10 +225,11 @@ the browser, or by Apache input filters to be overridden or modified. 
 REL="Help"

><STRONG>Module:</STRONG></A> mod_header<P>



This directive can replace, merge or remove HTTP response headers. The header

is modified just after the content handler and output filters are run, 

allowing outgoing headers to be modified. The action it performs is determined 

by the first argument. This can be one of the following values:

<p>This directive can replace, merge or remove HTTP response

headers. The header is modified just after the content handler and

output filters are run, allowing outgoing headers to be modified. The

action it performs is determined by the first argument. This can be

one of the following values:</p>



<UL>

<LI><STRONG>set</STRONG><BR>
@@ -210,13 +257,14 @@ by the first argument. This can be one of the following values: 
  <EM>header</EM> may be a regular expression. 

</UL>



This argument is followed by a <EM>header</EM> name, which can include the

<p>This argument is followed by a <EM>header</EM> name, which can include the

final colon, but it is not required. Case is ignored for set, append, add

and unset. The <EM>header</EM> name for echo is case sensitive and may be a

regular expression. 

<P>

add, append and set take a <EM>value</EM> as the third argument. If 

<EM>value</EM> contains spaces, it should be surrounded by doublequotes. 

regular expression.</p>



<P>For <code>add</code>, <code>append</code> and <code>set</code> a

<EM>value</EM> is specified as the third argument. If <EM>value</EM>

contains spaces, it should be surrounded by doublequotes.

<EM>value</EM> may be a character string, a string containing format

specifiers or a combination of both. The following format specifiers

are supported in <EM>value</EM>:
@@ -228,83 +276,22 @@ are supported in <EM>value</EM>: 
        headers are sent on the wire. This is a measure of the

	duration of the request. The value is preceeded by "D=".

</PRE>

add, append and set may take an optional <EM>conditional clause</EM>

as the fourth argument. The header action (add, append, set) is 

done only if the <EM>conditional clause</EM> evaluates as TRUE.



<H3>Order of Processing</H3>

<p>When the <code>Header</code> directive is used with the

<code>add</code>, <code>append</code>, or <code>set</code> argument, a

fourth argument may be used to specify conditions under which the

action will be taken.  If the <a href="../env.html">environment

variable</a> specified in the <code>env=...</code> argument exists (or

if the environment variable does not exist and <code>env=!...</code>

is specified) then the action specified by the <code>Header</code>

directive will take effect.  Otherwise, the directive will have no

effect on the request.</p>



<p>The Header directives are processed just before the response is

sent to the network. These means that it is possible to set and/or

override most headers, except for those headers added by the header

filter.</p>



The Header (like the RequestHeader) directives can occur almost anywhere within 

the server configuration. It is valid in the main server config and virtual 

host sections, inside &lt;Directory&gt;, &lt;Location&gt; and &lt;Files&gt;

sections, and within .htaccess files.

<P>

The Header directives are processed in the following order:

<OL>

<LI>main server

<LI>virtual host

<LI>&lt;Directory&gt; sections and .htaccess

<LI>&lt;Location&gt;

<LI>&lt;Files&gt;

</OL>



Order is important. These two headers have a different effect if reversed:

<PRE>

Header append Author "John P. Doe"

Header unset Author

</PRE>



This way round, the Author header is not set. If reversed, the Author

header is set to "John P. Doe".

<P>



The Header directives are processed just before the response is sent

to the network. These means that it is possible to set and/or override

most headers, except for those headers added by the header filter.

<P>

<HR>

<H2>Examples</H2>

<OL>

<LI>Copy all request headers that begin with "TS" to the response headers:</LI>

<PRE>

   Header echo ^TS*

</PRE>



<LI>Add a header, MyHeader, to the response including a timestamp for when

the request was received and how long it took to begin serving the

request. This header can be used by the client to intuit load on

the server or in isolating bottlenecks between the client and the

server.</LI>

<PRE>

   Header add MyHeader "%D %t"

</PRE>

results in this header being added to the response:

<PRE>

   MyHeader: D=3775428 t=991424704447256

</PRE>

<LI>Say hello to Joe</LI>

<PRE>

   Header add MyHeader "Hello Joe. It took %D microseconds for Apache to serve this request."

</PRE>

results in this header being added to the response:

<PRE>

   MyHeader: Hello Joe. It took D=3775428 microseconds for Apache to serve this request.

</PRE>



<LI>Conditionally send MyHeader on the response if and only if header

"MyRequestHeader" is present on the request. This is useful for

constructing headers in response to some client stimulus. Note that

this example requires the services of the mod_setenvif module.</LI>

<PRE>

   SetEnvIf MyRequestHeader value HAVE_MyRequestHeader<BR>

   Header add MyHeader "%D %t mytext" env=HAVE_MyRequestHeader

</PRE> 

If the header "MyRequestHeader: value" is present on the HTTP request, the response

will contain the following header:

<PRE>

   MyHeader: D=3775428 t=991424704447256 mytext

</PRE>

</OL>

<!--#include virtual="footer.html" -->

</BODY>

</HTML>