docs/manual/mod/mod_log_config.xml - httpd - Git at Google

 <?xml version="1.0"?>
 <!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
 <?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
 <!-- $LastChangedRevision$ -->

 <!--
  Copyright 2002-2004 The Apache Software Foundation

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
 -->

 <modulesynopsis metafile="mod_log_config.xml.meta">

 <name>mod_log_config</name>
 <description>Logging of the requests made to the server</description>
 <status>Base</status>
 <sourcefile>mod_log_config.c</sourcefile>
 <identifier>log_config_module</identifier>

 <summary>
     <p>This module provides for flexible logging of client
     requests. Logs are written in a customizable format, and may be
     written directly to a file, or to an external program.
     Conditional logging is provided so that individual requests may
     be included or excluded from the logs based on characteristics
     of the request.</p>

     <p>Three directives are provided by this module:
     <directive module="mod_log_config">TransferLog</directive> to create
     a log file, <directive module="mod_log_config">LogFormat</directive>
     to set a custom format, and <directive module="mod_log_config"
     >CustomLog</directive> to define a log file and format in one
     step. The <directive>TransferLog</directive> and <directive
     >CustomLog</directive> directives can be used multiple times in each
     server to cause each request to be logged to multiple files.</p>
 </summary>
 <seealso><a href="../logs.html">Apache Log Files</a></seealso>

 <section id="formats"><title>Custom Log Formats</title>

     <p>The format argument to the <directive module="mod_log_config"
     >LogFormat</directive> and <directive module="mod_log_config"
     >CustomLog</directive> directives is a string. This string is
     used to log each request to the log file. It can contain literal
     characters copied into the log files and the C-style control
     characters "\n" and "\t" to represent new-lines and tabs.
     Literal quotes and back-slashes should be escaped with
     back-slashes.</p>

     <p>The characteristics of the request itself are logged by
     placing "<code>%</code>" directives in the format string, which are
     replaced in the log file by the values as follows:</p>

     <table border="1" style="zebra">
     <columnspec><column width=".2"/><column width=".8"/></columnspec>
     <tr><th>Format&nbsp;String</th>
         <th>Description</th></tr>

     <tr><td><code>%%</code></td>
         <td>The percent sign</td></tr>

     <tr><td><code>%...a</code></td>
         <td>Remote IP-address</td></tr>

     <tr><td><code>%...A</code></td>
         <td>Local IP-address</td></tr>

     <tr><td><code>%...B</code></td>
         <td>Bytes sent, excluding HTTP headers.</td></tr>

     <tr><td><code>%...b</code></td>
         <td>Bytes sent, excluding HTTP headers. In CLF format, <em>i.e.</em>
         a '<code>-</code>' rather than a 0 when no bytes are sent.</td></tr>

     <tr><td><code>%...{<var>Foobar</var>}C</code></td>
         <td>The contents of cookie <var>Foobar</var> in the request sent
         to the server.</td></tr>

     <tr><td><code>%...D</code></td>
         <td>The time taken to serve the request, in microseconds.</td></tr>

     <tr><td><code>%...{<var>FOOBAR</var>}e</code></td>
         <td>The contents of the environment variable
         <var>FOOBAR</var></td></tr>

     <tr><td><code>%...f</code></td>
         <td>Filename</td></tr>

     <tr><td><code>%...h</code></td>
         <td>Remote host</td></tr>

     <tr><td><code>%...H</code></td>
         <td>The request protocol</td></tr>

     <tr><td><code>%...{<var>Foobar</var>}i</code></td>
         <td>The contents of <code><var>Foobar</var>:</code> header line(s)
         in the request sent to the server.</td></tr>

     <tr><td><code>%...l</code></td>
         <td>Remote logname (from identd, if supplied). This will return a
         dash unless <module>mod_ident</module> is present and <directive
         module="mod_ident">IdentityCheck</directive> is set
         <code>On</code>.</td></tr>

     <tr><td><code>%...m</code></td>
         <td>The request method</td></tr>

     <tr><td><code>%...{<var>Foobar</var>}n</code></td>
         <td>The contents of note <var>Foobar</var> from another
         module.</td></tr>

     <tr><td><code>%...{<var>Foobar</var>}o</code></td>
         <td>The contents of <code><var>Foobar</var>:</code> header line(s)
         in the reply.</td></tr>

     <tr><td><code>%...p</code></td>
         <td>The canonical port of the server serving the request</td></tr>

     <tr><td><code>%...P</code></td>
         <td>The process ID of the child that serviced the request.</td></tr>

     <tr><td><code>%...{<var>format</var>}P</code></td>
         <td>The process ID or thread id of the child that serviced the
         request.  Valid formats are <code>pid</code> and <code>tid</code>.
         </td></tr>

     <tr><td><code>%...q</code></td>
         <td>The query string (prepended with a <code>?</code> if a query
         string exists, otherwise an empty string)</td></tr>

     <tr><td><code>%...r</code></td>
         <td>First line of request</td></tr>

     <tr><td><code>%...s</code></td>
         <td>Status. For requests that got internally redirected, this is
         the status of the *original* request --- <code>%...&gt;s</code>
         for the last.</td></tr>

     <tr><td><code>%...t</code></td>
         <td>Time, in common log format time format (standard english
         format)</td></tr>

     <tr><td><code>%...{<var>format</var>}t</code></td>
         <td>The time, in the form given by format, which should be in
         <code>strftime(3)</code> format. (potentially localized)</td></tr>

     <tr><td><code>%...T</code></td>
         <td>The time taken to serve the request, in seconds.</td></tr>

     <tr><td><code>%...u</code></td>
         <td>Remote user (from auth; may be bogus if return status
         (<code>%s</code>) is 401)</td></tr>

     <tr><td><code>%...U</code></td>
         <td>The URL path requested, not including any query string.</td></tr>

     <tr><td><code>%...v</code></td>
         <td>The canonical <directive module="core">ServerName</directive>
         of the server serving the request.</td></tr>

     <tr><td><code>%...V</code></td>
         <td>The server name according to the <directive module="core"
         >UseCanonicalName</directive> setting.</td></tr>

     <tr><td><code>%...X</code></td>
         <td>Connection status when response is completed:

         <table>
         <columnspec><column width=".2"/><column width=".6"/></columnspec>
         <tr><td><code>X</code> =</td>
             <td>connection aborted before the response completed.</td></tr>
         <tr><td><code>+</code> =</td>
             <td>connection may be kept alive after the response is
             sent.</td></tr>
         <tr><td><code>-</code> = </td>
             <td>connection will be closed after the response is
             sent.</td></tr>
         </table>

         <p>(This directive was <code>%...c</code> in late versions of Apache
         1.3, but this conflicted with the historical ssl
         <code>%...{<var>var</var>}c</code> syntax.)</p></td></tr>

     <tr><td><code>%...I</code></td>
         <td>Bytes received, including request and headers, cannot be zero.
         You need to enable <module>mod_logio</module> to use this.</td></tr>

     <tr><td><code>%...O</code></td>
         <td>Bytes sent, including headers, cannot be zero. You need to
         enable <module>mod_logio</module> to use this.</td></tr>
     </table>

     <p>The "<var>...</var>" can be nothing at all (<em>e.g.</em>,
     <code>"%h %u %r %s %b"</code>), or it can indicate conditions for
     inclusion of the item (which will cause it to be replaced with "-" if
     the condition is not met). The forms of condition are a list of
     HTTP status codes, which may or may not be preceded by "!".
     Thus, "%400,501{User-agent}i" logs <code>User-agent:</code> on 400
     errors and 501 errors (Bad Request, Not Implemented) only;
     "%!200,304,302{Referer}i" logs <code>Referer:</code> on all requests
     which did <em>not</em> return some sort of normal status.</p>

     <p>The modifiers "&lt;" and "&gt;" can be used for requests that
     have been internally redirected to choose whether the original or
     final (respectively) request should be consulted.  By default, the
     <code>%</code> directives <code>%s, %U, %T, %D,</code> and
     <code>%r</code> look at the original request while all others look
     at the final request.  So for example, <code>%&gt;s</code> can be
     used to record the final status of the request and
     <code>%&lt;u</code> can be used to record the original
     authenticated user on a request that is internally redirected to an
     unauthenticated resource.</p>

     <p>Note that in httpd 2.0 versions prior to 2.0.46, no escaping was performed
     on the strings from <code>%...r</code>, <code>%...i</code> and
     <code>%...o</code>. This was mainly to comply with the requirements of
     the Common Log Format. This implied that clients could insert control
     characters into the log, so you had to be quite careful when dealing
     with raw log files.</p>

     <p>For security reasons, starting with 2.0.46, non-printable and
     other special characters are escaped mostly by using
     <code>\x<var>hh</var></code> sequences, where <var>hh</var> stands for
     the hexadecimal representation of the raw byte. Exceptions from this
     rule are <code>"</code> and <code>\</code> which are escaped by prepending
     a backslash, and all whitespace characters which are written in their
     C-style notation (<code>\n</code>, <code>\t</code> etc).</p>

     <p>Some commonly used log format strings are:</p>

     <dl>
       <dt>Common Log Format (CLF)</dt>
       <dd><code>"%h %l %u %t \"%r\" %&gt;s %b"</code></dd>

       <dt>Common Log Format with Virtual Host</dt>
       <dd><code>"%v %h %l %u %t \"%r\" %&gt;s %b"</code></dd>

       <dt>NCSA extended/combined log format</dt>
       <dd><code>"%h %l %u %t \"%r\" %&gt;s %b \"%{Referer}i\"
       \"%{User-agent}i\""</code></dd>

       <dt>Referer log format</dt>
       <dd><code>"%{Referer}i -&gt; %U"</code></dd>

       <dt>Agent (Browser) log format</dt>
       <dd><code>"%{User-agent}i"</code></dd>
     </dl>

     <p>Note that the canonical <directive module="core"
     >ServerName</directive> and <directive module="mpm_common"
     >Listen</directive> of the server serving the
     request are used for <code>%v</code> and <code>%p</code>
     respectively. This happens regardless of the <directive
     module="core">UseCanonicalName</directive> setting
     because otherwise log analysis programs would have to duplicate
     the entire vhost matching algorithm in order to decide what
     host really served the request.</p>
 </section>

 <section id="security"><title>Security Considerations</title>
     <p>See the <a
     href="../misc/security_tips.html#serverroot">security tips</a>
     document for details on why your security could be compromised
     if the directory where logfiles are stored is writable by
     anyone other than the user that starts the server.</p>
 </section>

 <directivesynopsis>
 <name>CookieLog</name>
 <description>Sets filename for the logging of cookies</description>
 <syntax>CookieLog <var>filename</var></syntax>
 <contextlist><context>server config</context><context>virtual host</context>
 </contextlist>
 <compatibility>This directive is deprecated.</compatibility>

 <usage>
     <p>The <directive>CookieLog</directive> directive sets the
     filename for logging of cookies. The filename is relative to the
     <directive module="core">ServerRoot</directive>. This directive is
     included only for compatibility with <code>mod_cookies</code>,
     and is deprecated.</p>
 </usage>
 </directivesynopsis>

 <directivesynopsis>
 <name>CustomLog</name>
 <description>Sets filename and format of log file</description>
 <syntax>CustomLog  <var>file</var>|<var>pipe</var>
 <var>format</var>|<var>nickname</var>
 [env=[!]<var>environment-variable</var>]</syntax>
 <contextlist><context>server config</context><context>virtual host</context>
 </contextlist>

 <usage>
     <p>The <directive>CustomLog</directive> directive is used to
     log requests to the server. A log format is specified, and the
     logging can optionally be made conditional on request
     characteristics using environment variables.</p>

     <p>The first argument, which specifies the location to which
     the logs will be written, can take one of the following two
     types of values:</p>

     <dl>
       <dt><var>file</var></dt>
       <dd>A filename, relative to the <directive module="core"
       >ServerRoot</directive>.</dd>

       <dt><var>pipe</var></dt>
       <dd>The pipe character "<code>|</code>", followed by the path
       to a program to receive the log information on its standard
       input.

       <note type="warning"><title>Security:</title>
       <p>If a program is used, then it will be run as the user who
       started <program>httpd</program>. This will be root if the server was
       started by root; be sure that the program is secure.</p>
       </note>
       <note type="warning"><title>Note</title>
         <p>When entering a file path on non-Unix platforms, care should be taken
         to make sure that only forward slashed are used even though the platform
         may allow the use of back slashes. In general it is a good idea to always
         use forward slashes throughout the configuration files.</p>
       </note></dd>
     </dl>

     <p>The second argument specifies what will be written to the
     log file. It can specify either a <var>nickname</var> defined by
     a previous <directive module="mod_log_config">LogFormat</directive>
     directive, or it can be an explicit <var>format</var> string as
     described in the <a href="#formats">log formats</a> section.</p>

     <p>For example, the following two sets of directives have
     exactly the same effect:</p>

     <example>
       # CustomLog with format nickname<br />
       LogFormat "%h %l %u %t \"%r\" %&gt;s %b" common<br />
       CustomLog logs/access_log common<br />
       <br />
       # CustomLog with explicit format string<br />
       CustomLog logs/access_log "%h %l %u %t \"%r\" %&gt;s %b"
     </example>

     <p>The third argument is optional and controls whether or
     not to log a particular request based on the
     presence or absence of a particular variable in the server
     environment. If the specified <a href="../env.html">environment
     variable</a> is set for the request (or is not set, in the case
     of a '<code>env=!<var>name</var></code>' clause), then the
     request will be logged.</p>

     <p>Environment variables can be set on a per-request
     basis using the <module>mod_setenvif</module>
     and/or <module>mod_rewrite</module> modules. For
     example, if you want to record requests for all GIF
     images on your server in a separate logfile but not in your main
     log, you can use:</p>

     <example>
       SetEnvIf Request_URI \.gif$ gif-image<br />
       CustomLog gif-requests.log common env=gif-image<br />
       CustomLog nongif-requests.log common env=!gif-image
     </example>
 </usage>
 </directivesynopsis>

 <directivesynopsis>
 <name>LogFormat</name>
 <description>Describes a format for use in a log file</description>
 <syntax>LogFormat <var>format</var>|<var>nickname</var>
 [<var>nickname</var>]</syntax>
 <default>LogFormat "%h %l %u %t \"%r\" %>s %b"</default>
 <contextlist><context>server config</context><context>virtual host</context>
 </contextlist>

 <usage>
     <p>This directive specifies the format of the access log
     file.</p>

     <p>The <directive>LogFormat</directive> directive can take one of two
     forms. In the first form, where only one argument is specified,
     this directive sets the log format which will be used by logs
     specified in subsequent <directive>TransferLog</directive>
     directives. The single argument can specify an explicit
     <var>format</var> as discussed in the <a href="#formats">custom log
     formats</a> section above. Alternatively, it can use a
     <var>nickname</var> to refer to a log format defined in a
     previous <directive>LogFormat</directive> directive as described
     below.</p>

     <p>The second form of the <directive>LogFormat</directive>
     directive associates an explicit <var>format</var> with a
     <var>nickname</var>. This <var>nickname</var> can then be used in
     subsequent <directive>LogFormat</directive> or
     <directive module="mod_log_config">CustomLog</directive> directives
     rather than repeating the entire format string. A
     <directive>LogFormat</directive> directive that defines a nickname
     <strong>does nothing else</strong> -- that is, it <em>only</em>
     defines the nickname, it doesn't actually apply the format and make
     it the default. Therefore, it will not affect subsequent
     <directive module="mod_log_config">TransferLog</directive> directives.
     In addition, <directive>LogFormat</directive> cannot use one nickname
     to define another nickname. Note that the nickname should not contain
     percent signs (<code>%</code>).</p>

     <example><title>Example</title>
       LogFormat "%v %h %l %u %t \"%r\" %&gt;s %b" vhost_common
     </example>
 </usage>
 </directivesynopsis>

 <directivesynopsis>
 <name>TransferLog</name>
 <description>Specify location of a log file</description>
 <syntax>TransferLog <var>file</var>|<var>pipe</var></syntax>
 <contextlist><context>server config</context><context>virtual host</context>
 </contextlist>

 <usage>
     <p>This directive has exactly the same arguments and effect as
     the <directive module="mod_log_config">CustomLog</directive>
     directive, with the exception that it does not allow the log format
     to be specified explicitly or for conditional logging of requests.
     Instead, the log format is determined by the most recently specified
     <directive module="mod_log_config">LogFormat</directive> directive
     which does not define a nickname. Common Log Format is used if no
     other format has been specified.</p>

     <example><title>Example</title>
       LogFormat "%h %l %u %t \"%r\" %&gt;s %b \"%{Referer}i\" \"%{User-agent}i\""<br />
       TransferLog logs/access_log
     </example>
 </usage>
 </directivesynopsis>

 </modulesynopsis>
	<?xml version="1.0"?>
	<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
	<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
	<!-- $LastChangedRevision$ -->

	<!--
	Copyright 2002-2004 The Apache Software Foundation

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->

	<modulesynopsis metafile="mod_log_config.xml.meta">

	<name>mod_log_config</name>
	<description>Logging of the requests made to the server</description>
	<status>Base</status>
	<sourcefile>mod_log_config.c</sourcefile>
	<identifier>log_config_module</identifier>

	<summary>
	<p>This module provides for flexible logging of client
	requests. Logs are written in a customizable format, and may be
	written directly to a file, or to an external program.
	Conditional logging is provided so that individual requests may
	be included or excluded from the logs based on characteristics
	of the request.</p>

	<p>Three directives are provided by this module:
	<directive module="mod_log_config">TransferLog</directive> to create
	a log file, <directive module="mod_log_config">LogFormat</directive>
	to set a custom format, and <directive module="mod_log_config"
	>CustomLog</directive> to define a log file and format in one
	step. The <directive>TransferLog</directive> and <directive
	>CustomLog</directive> directives can be used multiple times in each
	server to cause each request to be logged to multiple files.</p>
	</summary>
	<seealso><a href="../logs.html">Apache Log Files</a></seealso>

	<section id="formats"><title>Custom Log Formats</title>

	<p>The format argument to the <directive module="mod_log_config"
	>LogFormat</directive> and <directive module="mod_log_config"
	>CustomLog</directive> directives is a string. This string is
	used to log each request to the log file. It can contain literal
	characters copied into the log files and the C-style control
	characters "\n" and "\t" to represent new-lines and tabs.
	Literal quotes and back-slashes should be escaped with
	back-slashes.</p>

	<p>The characteristics of the request itself are logged by
	placing "<code>%</code>" directives in the format string, which are
	replaced in the log file by the values as follows:</p>

	<table border="1" style="zebra">
	<columnspec><column width=".2"/><column width=".8"/></columnspec>
	<tr><th>Format String</th>
	<th>Description</th></tr>

	<tr><td><code>%%</code></td>
	<td>The percent sign</td></tr>

	<tr><td><code>%...a</code></td>
	<td>Remote IP-address</td></tr>

	<tr><td><code>%...A</code></td>
	<td>Local IP-address</td></tr>

	<tr><td><code>%...B</code></td>
	<td>Bytes sent, excluding HTTP headers.</td></tr>

	<tr><td><code>%...b</code></td>
	<td>Bytes sent, excluding HTTP headers. In CLF format, <em>i.e.</em>
	a '<code>-</code>' rather than a 0 when no bytes are sent.</td></tr>

	<tr><td><code>%...{<var>Foobar</var>}C</code></td>
	<td>The contents of cookie <var>Foobar</var> in the request sent
	to the server.</td></tr>

	<tr><td><code>%...D</code></td>
	<td>The time taken to serve the request, in microseconds.</td></tr>

	<tr><td><code>%...{<var>FOOBAR</var>}e</code></td>
	<td>The contents of the environment variable
	<var>FOOBAR</var></td></tr>

	<tr><td><code>%...f</code></td>
	<td>Filename</td></tr>

	<tr><td><code>%...h</code></td>
	<td>Remote host</td></tr>

	<tr><td><code>%...H</code></td>
	<td>The request protocol</td></tr>

	<tr><td><code>%...{<var>Foobar</var>}i</code></td>
	<td>The contents of <code><var>Foobar</var>:</code> header line(s)
	in the request sent to the server.</td></tr>

	<tr><td><code>%...l</code></td>
	<td>Remote logname (from identd, if supplied). This will return a
	dash unless <module>mod_ident</module> is present and <directive
	module="mod_ident">IdentityCheck</directive> is set
	<code>On</code>.</td></tr>

	<tr><td><code>%...m</code></td>
	<td>The request method</td></tr>

	<tr><td><code>%...{<var>Foobar</var>}n</code></td>
	<td>The contents of note <var>Foobar</var> from another
	module.</td></tr>

	<tr><td><code>%...{<var>Foobar</var>}o</code></td>
	<td>The contents of <code><var>Foobar</var>:</code> header line(s)
	in the reply.</td></tr>

	<tr><td><code>%...p</code></td>
	<td>The canonical port of the server serving the request</td></tr>

	<tr><td><code>%...P</code></td>
	<td>The process ID of the child that serviced the request.</td></tr>

	<tr><td><code>%...{<var>format</var>}P</code></td>
	<td>The process ID or thread id of the child that serviced the
	request. Valid formats are <code>pid</code> and <code>tid</code>.
	</td></tr>

	<tr><td><code>%...q</code></td>
	<td>The query string (prepended with a <code>?</code> if a query
	string exists, otherwise an empty string)</td></tr>

	<tr><td><code>%...r</code></td>
	<td>First line of request</td></tr>

	<tr><td><code>%...s</code></td>
	<td>Status. For requests that got internally redirected, this is
	the status of the original request --- <code>%...>s</code>
	for the last.</td></tr>

	<tr><td><code>%...t</code></td>
	<td>Time, in common log format time format (standard english
	format)</td></tr>

	<tr><td><code>%...{<var>format</var>}t</code></td>
	<td>The time, in the form given by format, which should be in
	<code>strftime(3)</code> format. (potentially localized)</td></tr>

	<tr><td><code>%...T</code></td>
	<td>The time taken to serve the request, in seconds.</td></tr>

	<tr><td><code>%...u</code></td>
	<td>Remote user (from auth; may be bogus if return status
	(<code>%s</code>) is 401)</td></tr>

	<tr><td><code>%...U</code></td>
	<td>The URL path requested, not including any query string.</td></tr>

	<tr><td><code>%...v</code></td>
	<td>The canonical <directive module="core">ServerName</directive>
	of the server serving the request.</td></tr>

	<tr><td><code>%...V</code></td>
	<td>The server name according to the <directive module="core"
	>UseCanonicalName</directive> setting.</td></tr>

	<tr><td><code>%...X</code></td>
	<td>Connection status when response is completed:

	<table>
	<columnspec><column width=".2"/><column width=".6"/></columnspec>
	<tr><td><code>X</code> =</td>
	<td>connection aborted before the response completed.</td></tr>
	<tr><td><code>+</code> =</td>
	<td>connection may be kept alive after the response is
	sent.</td></tr>
	<tr><td><code>-</code> = </td>
	<td>connection will be closed after the response is
	sent.</td></tr>
	</table>

	<p>(This directive was <code>%...c</code> in late versions of Apache
	1.3, but this conflicted with the historical ssl
	<code>%...{<var>var</var>}c</code> syntax.)</p></td></tr>

	<tr><td><code>%...I</code></td>
	<td>Bytes received, including request and headers, cannot be zero.
	You need to enable <module>mod_logio</module> to use this.</td></tr>

	<tr><td><code>%...O</code></td>
	<td>Bytes sent, including headers, cannot be zero. You need to
	enable <module>mod_logio</module> to use this.</td></tr>
	</table>

	<p>The "<var>...</var>" can be nothing at all (<em>e.g.</em>,
	<code>"%h %u %r %s %b"</code>), or it can indicate conditions for
	inclusion of the item (which will cause it to be replaced with "-" if
	the condition is not met). The forms of condition are a list of
	HTTP status codes, which may or may not be preceded by "!".
	Thus, "%400,501{User-agent}i" logs <code>User-agent:</code> on 400
	errors and 501 errors (Bad Request, Not Implemented) only;
	"%!200,304,302{Referer}i" logs <code>Referer:</code> on all requests
	which did <em>not</em> return some sort of normal status.</p>

	<p>The modifiers "<" and ">" can be used for requests that
	have been internally redirected to choose whether the original or
	final (respectively) request should be consulted. By default, the
	<code>%</code> directives <code>%s, %U, %T, %D,</code> and
	<code>%r</code> look at the original request while all others look
	at the final request. So for example, <code>%>s</code> can be
	used to record the final status of the request and
	<code>%<u</code> can be used to record the original
	authenticated user on a request that is internally redirected to an
	unauthenticated resource.</p>

	<p>Note that in httpd 2.0 versions prior to 2.0.46, no escaping was performed
	on the strings from <code>%...r</code>, <code>%...i</code> and
	<code>%...o</code>. This was mainly to comply with the requirements of
	the Common Log Format. This implied that clients could insert control
	characters into the log, so you had to be quite careful when dealing
	with raw log files.</p>

	<p>For security reasons, starting with 2.0.46, non-printable and
	other special characters are escaped mostly by using
	<code>\x<var>hh</var></code> sequences, where <var>hh</var> stands for
	the hexadecimal representation of the raw byte. Exceptions from this
	rule are <code>"</code> and <code>\</code> which are escaped by prepending
	a backslash, and all whitespace characters which are written in their
	C-style notation (<code>\n</code>, <code>\t</code> etc).</p>

	<p>Some commonly used log format strings are:</p>

	<dl>
	<dt>Common Log Format (CLF)</dt>
	<dd><code>"%h %l %u %t \"%r\" %>s %b"</code></dd>

	<dt>Common Log Format with Virtual Host</dt>
	<dd><code>"%v %h %l %u %t \"%r\" %>s %b"</code></dd>

	<dt>NCSA extended/combined log format</dt>
	<dd><code>"%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
	\"%{User-agent}i\""</code></dd>

	<dt>Referer log format</dt>
	<dd><code>"%{Referer}i -> %U"</code></dd>

	<dt>Agent (Browser) log format</dt>
	<dd><code>"%{User-agent}i"</code></dd>
	</dl>

	<p>Note that the canonical <directive module="core"
	>ServerName</directive> and <directive module="mpm_common"
	>Listen</directive> of the server serving the
	request are used for <code>%v</code> and <code>%p</code>
	respectively. This happens regardless of the <directive
	module="core">UseCanonicalName</directive> setting
	because otherwise log analysis programs would have to duplicate
	the entire vhost matching algorithm in order to decide what
	host really served the request.</p>
	</section>

	<section id="security"><title>Security Considerations</title>
	<p>See the <a
	href="../misc/security_tips.html#serverroot">security tips</a>
	document for details on why your security could be compromised
	if the directory where logfiles are stored is writable by
	anyone other than the user that starts the server.</p>
	</section>

	<directivesynopsis>
	<name>CookieLog</name>
	<description>Sets filename for the logging of cookies</description>
	<syntax>CookieLog <var>filename</var></syntax>
	<contextlist><context>server config</context><context>virtual host</context>
	</contextlist>
	<compatibility>This directive is deprecated.</compatibility>

	<usage>
	<p>The <directive>CookieLog</directive> directive sets the
	filename for logging of cookies. The filename is relative to the
	<directive module="core">ServerRoot</directive>. This directive is
	included only for compatibility with <code>mod_cookies</code>,
	and is deprecated.</p>
	</usage>
	</directivesynopsis>

	<directivesynopsis>
	<name>CustomLog</name>
	<description>Sets filename and format of log file</description>
	<syntax>CustomLog <var>file</var>\|<var>pipe</var>
	<var>format</var>\|<var>nickname</var>
	[env=[!]<var>environment-variable</var>]</syntax>
	<contextlist><context>server config</context><context>virtual host</context>
	</contextlist>

	<usage>
	<p>The <directive>CustomLog</directive> directive is used to
	log requests to the server. A log format is specified, and the
	logging can optionally be made conditional on request
	characteristics using environment variables.</p>

	<p>The first argument, which specifies the location to which
	the logs will be written, can take one of the following two
	types of values:</p>

	<dl>
	<dt><var>file</var></dt>
	<dd>A filename, relative to the <directive module="core"
	>ServerRoot</directive>.</dd>

	<dt><var>pipe</var></dt>
	<dd>The pipe character "<code>\|</code>", followed by the path
	to a program to receive the log information on its standard
	input.

	<note type="warning"><title>Security:</title>
	<p>If a program is used, then it will be run as the user who
	started <program>httpd</program>. This will be root if the server was
	started by root; be sure that the program is secure.</p>
	</note>
	<note type="warning"><title>Note</title>
	<p>When entering a file path on non-Unix platforms, care should be taken
	to make sure that only forward slashed are used even though the platform
	may allow the use of back slashes. In general it is a good idea to always
	use forward slashes throughout the configuration files.</p>
	</note></dd>
	</dl>

	<p>The second argument specifies what will be written to the
	log file. It can specify either a <var>nickname</var> defined by
	a previous <directive module="mod_log_config">LogFormat</directive>
	directive, or it can be an explicit <var>format</var> string as
	described in the <a href="#formats">log formats</a> section.</p>

	<p>For example, the following two sets of directives have
	exactly the same effect:</p>

	<example>
	# CustomLog with format nickname<br />
	LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
	CustomLog logs/access_log common<br />
	<br />
	# CustomLog with explicit format string<br />
	CustomLog logs/access_log "%h %l %u %t \"%r\" %>s %b"
	</example>

	<p>The third argument is optional and controls whether or
	not to log a particular request based on the
	presence or absence of a particular variable in the server
	environment. If the specified <a href="../env.html">environment
	variable</a> is set for the request (or is not set, in the case
	of a '<code>env=!<var>name</var></code>' clause), then the
	request will be logged.</p>

	<p>Environment variables can be set on a per-request
	basis using the <module>mod_setenvif</module>
	and/or <module>mod_rewrite</module> modules. For
	example, if you want to record requests for all GIF
	images on your server in a separate logfile but not in your main
	log, you can use:</p>

	<example>
	SetEnvIf Request_URI \.gif$ gif-image<br />
	CustomLog gif-requests.log common env=gif-image<br />
	CustomLog nongif-requests.log common env=!gif-image
	</example>
	</usage>
	</directivesynopsis>

	<directivesynopsis>
	<name>LogFormat</name>
	<description>Describes a format for use in a log file</description>
	<syntax>LogFormat <var>format</var>\|<var>nickname</var>
	[<var>nickname</var>]</syntax>
	<default>LogFormat "%h %l %u %t \"%r\" %>s %b"</default>
	<contextlist><context>server config</context><context>virtual host</context>
	</contextlist>

	<usage>
	<p>This directive specifies the format of the access log
	file.</p>

	<p>The <directive>LogFormat</directive> directive can take one of two
	forms. In the first form, where only one argument is specified,
	this directive sets the log format which will be used by logs
	specified in subsequent <directive>TransferLog</directive>
	directives. The single argument can specify an explicit
	<var>format</var> as discussed in the <a href="#formats">custom log
	formats</a> section above. Alternatively, it can use a
	<var>nickname</var> to refer to a log format defined in a
	previous <directive>LogFormat</directive> directive as described
	below.</p>

	<p>The second form of the <directive>LogFormat</directive>
	directive associates an explicit <var>format</var> with a
	<var>nickname</var>. This <var>nickname</var> can then be used in
	subsequent <directive>LogFormat</directive> or
	<directive module="mod_log_config">CustomLog</directive> directives
	rather than repeating the entire format string. A
	<directive>LogFormat</directive> directive that defines a nickname
	<strong>does nothing else</strong> -- that is, it <em>only</em>
	defines the nickname, it doesn't actually apply the format and make
	it the default. Therefore, it will not affect subsequent
	<directive module="mod_log_config">TransferLog</directive> directives.
	In addition, <directive>LogFormat</directive> cannot use one nickname
	to define another nickname. Note that the nickname should not contain
	percent signs (<code>%</code>).</p>

	<example><title>Example</title>
	LogFormat "%v %h %l %u %t \"%r\" %>s %b" vhost_common
	</example>
	</usage>
	</directivesynopsis>

	<directivesynopsis>
	<name>TransferLog</name>
	<description>Specify location of a log file</description>
	<syntax>TransferLog <var>file</var>\|<var>pipe</var></syntax>
	<contextlist><context>server config</context><context>virtual host</context>
	</contextlist>

	<usage>
	<p>This directive has exactly the same arguments and effect as
	the <directive module="mod_log_config">CustomLog</directive>
	directive, with the exception that it does not allow the log format
	to be specified explicitly or for conditional logging of requests.
	Instead, the log format is determined by the most recently specified
	<directive module="mod_log_config">LogFormat</directive> directive
	which does not define a nickname. Common Log Format is used if no
	other format has been specified.</p>

	<example><title>Example</title>
	LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\""<br />
	TransferLog logs/access_log
	</example>
	</usage>
	</directivesynopsis>

	</modulesynopsis>