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

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 <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>Size of response in bytes, excluding HTTP headers.</td></tr>

     <tr><td><code>%b</code></td>
         <td>Size of response in bytes, 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>, <code>tid</code>,
         and <code>hextid</code>.  <code>hextid</code> requires APR 1.2.0 or
         higher.
         </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 the request was received (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>

     <section id="modifiers"><title>Modifiers</title>

       <p>Particular items can be restricted to print only for
       responses with specific HTTP status codes by placing a
       comma-separated list of status codes immediately following the
       "%".  For example, <code>"%400,501{User-agent}i"</code> logs
       <code>User-agent</code> on 400 errors and 501 errors only.  For
       other status codes, the literal string <code>"-"</code> will be
       logged.  The status code list may be preceded by a
       "<code>!</code>" to indicate negation:
       <code>"%!200,304,302{Referer}i"</code> logs <code>Referer</code>
       on all requests that do <em>not</em> return one of the three
       specified codes.</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>

     </section>

     <section id="format-notes"><title>Some Notes</title>

       <p>For security reasons, starting with version 2.0.46,
       non-printable and other special characters in <code>%r</code>,
       <code>%i</code> and <code>%o</code> are escaped 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).  In versions
       prior to 2.0.46, no escaping was performed on these strings so
       you had to be quite careful when dealing with raw log files.</p>

       <p>In httpd 2.0, unlike 1.3, the <code>%b</code> and
       <code>%B</code> format strings do not represent the number of
       bytes sent to the client, but simply the size in bytes of the
       HTTP response (which will differ, for instance, if the
       connection is aborted, or if SSL is used).  The <code>%O</code>
       format provided by <module>mod_logio</module> will log the
       actual number of bytes sent over the network.</p>

     </section>

     <section id="examples"><title>Examples</title>

       <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>
     </section>
 </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>BufferedLogs</name>
 <description>Buffer log entries in memory before writing to disk</description>
 <syntax>BufferedLogs On|Off</syntax>
 <default>BufferedLogs Off</default>
 <contextlist><context>server config</context></contextlist>
 <status>Experimental</status>
 <compatibility>Available in versions 2.0.41 and later.</compatibility>

 <usage>
     <p>The <directive>BufferedLogs</directive> directive causes
     <module>mod_log_config</module> to store several log entries in
     memory and write them together to disk, rather than writing them
     after each request.  On some systems, this may result in more
     efficient disk access and hence higher performance.  It may be
     set only once for the entire server; it cannot be configured
     per virtual-host.</p>

     <note>This directive is experimental and should be used with
     caution.</note>
 </usage>
 </directivesynopsis>

 <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>

     <p>Or, to reproduce the behavior of the old RefererIgnore
     directive, you might use the following:</p>

     <example>
     SetEnvIf Referer example\.com localreferer<br />
     CustomLog referer.log referer env=!localreferer
     </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"?>
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	<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
	<!-- $LastChangedRevision$ -->

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	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

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	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
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	<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>Size of response in bytes, excluding HTTP headers.</td></tr>

	<tr><td><code>%b</code></td>
	<td>Size of response in bytes, 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>, <code>tid</code>,
	and <code>hextid</code>. <code>hextid</code> requires APR 1.2.0 or
	higher.
	</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 the request was received (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>

	<section id="modifiers"><title>Modifiers</title>

	<p>Particular items can be restricted to print only for
	responses with specific HTTP status codes by placing a
	comma-separated list of status codes immediately following the
	"%". For example, <code>"%400,501{User-agent}i"</code> logs
	<code>User-agent</code> on 400 errors and 501 errors only. For
	other status codes, the literal string <code>"-"</code> will be
	logged. The status code list may be preceded by a
	"<code>!</code>" to indicate negation:
	<code>"%!200,304,302{Referer}i"</code> logs <code>Referer</code>
	on all requests that do <em>not</em> return one of the three
	specified codes.</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>

	</section>

	<section id="format-notes"><title>Some Notes</title>

	<p>For security reasons, starting with version 2.0.46,
	non-printable and other special characters in <code>%r</code>,
	<code>%i</code> and <code>%o</code> are escaped 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). In versions
	prior to 2.0.46, no escaping was performed on these strings so
	you had to be quite careful when dealing with raw log files.</p>

	<p>In httpd 2.0, unlike 1.3, the <code>%b</code> and
	<code>%B</code> format strings do not represent the number of
	bytes sent to the client, but simply the size in bytes of the
	HTTP response (which will differ, for instance, if the
	connection is aborted, or if SSL is used). The <code>%O</code>
	format provided by <module>mod_logio</module> will log the
	actual number of bytes sent over the network.</p>

	</section>

	<section id="examples"><title>Examples</title>

	<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>
	</section>
	</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>BufferedLogs</name>
	<description>Buffer log entries in memory before writing to disk</description>
	<syntax>BufferedLogs On\|Off</syntax>
	<default>BufferedLogs Off</default>
	<contextlist><context>server config</context></contextlist>
	<status>Experimental</status>
	<compatibility>Available in versions 2.0.41 and later.</compatibility>

	<usage>
	<p>The <directive>BufferedLogs</directive> directive causes
	<module>mod_log_config</module> to store several log entries in
	memory and write them together to disk, rather than writing them
	after each request. On some systems, this may result in more
	efficient disk access and hence higher performance. It may be
	set only once for the entire server; it cannot be configured
	per virtual-host.</p>

	<note>This directive is experimental and should be used with
	caution.</note>
	</usage>
	</directivesynopsis>

	<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>

	<p>Or, to reproduce the behavior of the old RefererIgnore
	directive, you might use the following:</p>

	<example>
	SetEnvIf Referer example\.com localreferer<br />
	CustomLog referer.log referer env=!localreferer
	</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>