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 <H1 ALIGN="CENTER">Module mod_log_config</H1>
 <P>
 This module provides for logging of the requests made to
 the server, using the Common Log Format or a user-specified format.
 </P>

 <P><A
 HREF="module-dict.html#Status"
 REL="Help"
 ><STRONG>Status:</STRONG></A> Base
 <BR>
 <A
 HREF="module-dict.html#SourceFile"
 REL="Help"
 ><STRONG>Source File:</STRONG></A> mod_log_config.c
 <BR>
 <A
 HREF="module-dict.html#ModuleIdentifier"
 REL="Help"
 ><STRONG>Module Identifier:</STRONG></A> config_log_module
 </P>


 <H2>Summary</H2>

 <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: <CODE>TransferLog</CODE>
 to create a log file, <CODE>LogFormat</CODE> to set a custom format,
 and <CODE>CustomLog</CODE> to define a log file and format in one step.
 The <CODE>TransferLog</CODE> and <CODE>CustomLog</CODE> directives can
 be used multiple times in each server to cause each request to be
 logged to multiple files.
 </P>

 <H2>Directives</H2>

 <UL>
 <LI><A HREF="#cookielog">CookieLog</A></LI>
 <LI><A HREF="#customlog">CustomLog</A></LI>
 <LI><A HREF="#logformat">LogFormat</A></LI>
 <LI><A HREF="#transferlog">TransferLog</A></LI>
 </UL>

 <H2>Log File Formats</H2>

 <p>Unless told otherwise with <TT>LogFormat</TT>, the log files
 created by <TT>TransferLog</TT> will be in standard "Common Log
 Format" (CLF). The contents of each line in a CLF file are explained
 below. Alternatively, the log file can be customized (and if multiple
 log files are used, each can have a different format). Custom formats
 are set with <CODE>LogFormat</CODE> and <CODE>CustomLog</CODE>.</p>

 <H3>Common Log Format</H3>

 <p>The Common Log Format (CLF) file contains a separate line for each
 request. A line is composed of several tokens separated by spaces:</p>

 <BLOCKQUOTE>
 host ident authuser date request status bytes
 </BLOCKQUOTE>
 If a token does not have a value then it is represented by a hyphen (-).
 The meanings and values of these tokens are as follows:
 <DL>
 <DT>host
 <DD>The fully-qualified domain name of the client, or its IP number if the
 name is not available.
 <DT>ident
 <DD>If <A HREF="core.html#identitycheck">IdentityCheck</A> is enabled and the
 client machine runs identd, then this is the identity information reported
 by the client.
 <DT>authuser
 <DD>If the request was for an password protected document, then this is
 the userid used in the request.
 <DT>date
 <DD>The date and time of the request, in the following format:
 <DL><DD><BLOCKQUOTE><CODE> date = [day/month/year:hour:minute:second zone] <BR>
 day = 2*digit<BR>
 month = 3*letter<BR>
 year = 4*digit<BR>
 hour = 2*digit<BR>
 minute = 2*digit<BR>
 second = 2*digit<BR>
 zone = (`+' | `-') 4*digit</CODE></BLOCKQUOTE></DL>
 <DT>request
 <DD>The request line from the client, enclosed in double quotes
 (<CODE>&quot;</CODE>).
 <DT>status
 <DD>The three digit status code returned to the client.
 <DT>bytes
 <DD>The number of bytes in the object returned to the client, not including
 any headers.
 </DL>

 <H3><A NAME="formats">Custom Log Formats</A></H3>

 <p>The format argument to the <CODE>LogFormat</CODE> and
 <CODE>CustomLog</CODE> directives is a string. This string is logged
 to the log file for each request. It can contain literal characters
 copied into the log files and the c-type 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
 "%" directives in the format string, which are replaced in the log file
 by the values as follows:</p>

 <PRE>
 %...a:          Remote IP-address
 %...A:          Local IP-address
 %...B:          Bytes sent, excluding HTTP headers.
 %...b:          Bytes sent, excluding HTTP headers. In CLF format
 		i.e. a '-' rather than a 0 when no bytes are sent.
 %...c:          Connection status when response is completed.
                 'X' = connection aborted before the response completed.
                 '+' = connection may be kept alive after the response is sent.
                 '-' = connection will be closed after the response is sent.
 %...{Foobar}C:	The contents of cookie "Foobar" in the request sent to the
                 server.
 %...D:          The time taken to serve the request, in microseconds.
 %...{FOOBAR}e:  The contents of the environment variable FOOBAR
 %...f:          Filename
 %...h:          Remote host
 %...H		The request protocol
 %...{Foobar}i:  The contents of Foobar: header line(s) in the request
                 sent to the server.
 %...l:          Remote logname (from identd, if supplied)
 %...m		The request method
 %...{Foobar}n:  The contents of note "Foobar" from another module.
 %...{Foobar}o:  The contents of Foobar: header line(s) in the reply.
 %...p:          The canonical Port of the server serving the request
 %...P:          The process ID of the child that serviced the request.
 %...q		The query string (prepended with a ? if a query string exists,
 		otherwise an empty string)
 %...r:          First line of request
 %...s:          Status.  For requests that got internally redirected, this is
                 the status of the *original* request --- %...&gt;s for the last.
 %...t:          Time, in common log format time format (standard english format)
 %...{format}t:  The time, in the form given by format, which should
                 be in strftime(3) format. (potentially localized)
 %...T:          The time taken to serve the request, in seconds.
 %...u:          Remote user (from auth; may be bogus if return status (%s) is 401)
 %...U:          The URL path requested.
 %...v:          The canonical ServerName of the server serving the request.
 %...V:          The server name according to the UseCanonicalName setting.
 </PRE>

 <p>The "..." 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
 User-agent: on 400 errors and 501 errors (Bad Request, Not
 Implemented) only; "%!200,304,302{Referer}i" logs Referer: on all
 requests which did <STRONG>not</STRONG> return some sort of normal
 status.</p>

 <p>Note that there is no escaping performed on the strings from
 %...r, %...i and %...o.  This is mainly to comply with the requirements
 of the Common Log Format.  This implies that clients can insert
 control characters into the log, so care should be taken when dealing
 with raw log files.</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 <A
 HREF="core.html#servername">ServerName</A> and <A
 HREF="core.html#port">Port</A> of the server serving the request are
 used for <CODE>%v</CODE> and <CODE>%p</CODE> respectively.  This
 happens regardless of the <A
 HREF="core.html#usecanonicalname">UseCanonicalName</A> 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>

 <H2>Using Multiple Log Files</H2>

 <p>The <CODE>TransferLog</CODE> and <CODE>CustomLog</CODE> directives can
 be given more than once to log requests to multiple log files. Unless
 the conditional form of <code>CustomLog</code> is used, each
 request will be logged to all the log files defined by either of these
 directives.</p>

 <H3>Use with Virtual Hosts</H3>

 <p>If a &lt;VirtualHost&gt; section does not contain any
 <TT>TransferLog</TT> or <TT>CustomLog</TT> directives, the
 logs defined for the main server will be used. If it does
 contain one or more of these directives, requests serviced by
 this virtual host will only be logged in the log files defined
 within its definition, not in any of the main server's log files.
 See the examples below.</p>

 <H2>Security Considerations</H2>

 <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>

 <h2>Resetting the Log Files</h2>

 <p>The access log file typically grows 1MB or more for each 10,000
 requests.  It will probably be necessary to move or delete the log
 file on a regular basis.  This cannot be done while the server is
 still running, because Apache will continue writing to the old log
 file.  Instead, the server must be <a
 href="../stopping.html">restarted</a> after the log file is moved or
 deleted so that it will open a new log.</p>

 <p>A typical scenario is:</p>

 <pre>
    mv access_log access_log.old
    apachectl graceful
    # wait for all requests to the old server to complete
    # before doing anything with access_log.old
 </pre>

 <p>Alternatively, log files can be <a
 href="../misc/FAQ.html#rotate">rotated automatically</a> be writing
 them through a pipe to a program designed for that purpose such
 as <a href="../programs/rotatelogs.html">rotatelogs</a>.</p>

 <HR>


 <H2><A NAME="cookielog">CookieLog</A> directive</H2>
 <!--%plaintext &lt;?INDEX {\tt CookieLog} directive&gt; -->
 <p><A
  HREF="directive-dict.html#Syntax"
  REL="Help"
 ><STRONG>Syntax:</STRONG></A> CookieLog <EM>filename</EM><BR>
 <A
  HREF="directive-dict.html#Context"
  REL="Help"
 ><STRONG>Context:</STRONG></A> server config, virtual host<BR>
 <A
  HREF="directive-dict.html#Module"
  REL="Help"
 ><STRONG>Module:</STRONG></A> mod_cookies<BR>
 <A
  HREF="directive-dict.html#Compatibility"
  REL="Help"
 ><STRONG>Compatibility:</STRONG></A> Only available in Apache 1.2 and above</p>

 <p>The CookieLog directive sets the filename for logging of cookies.
 The filename is relative to the <A
 HREF="core.html#serverroot">ServerRoot</A>. This directive is included
 only for compatibility with mod_cookies, and is deprecated.</p>

 <HR>
 <H2><A NAME="customlog">CustomLog</A>
 <a NAME="customlogconditional">directive</a></H2>
 <p><A
  HREF="directive-dict.html#Syntax"
  REL="Help"
 ><STRONG>Syntax:</STRONG></A> CustomLog <EM>file</em>|<em>pipe</EM>
     <EM>format</em>|<em>nickname</EM>  [env=[!]<EM>environment-variable</EM>]<BR>
 <A
  HREF="directive-dict.html#Context"
  REL="Help"
 ><STRONG>Context:</STRONG></A> server config, virtual host<BR>
 <A
  HREF="directive-dict.html#Status"
  REL="Help"
 ><STRONG>Status:</STRONG></A> Base<BR>
 <A
  HREF="directive-dict.html#Compatibility"
  REL="Help"
 ><STRONG>Compatibility:</STRONG></A> Nickname only available in Apache 1.3
     or later.  Conditional logging available in 1.3.5 or later.
 <BR>
 <A
  HREF="directive-dict.html#Module"
  REL="Help"
 ><STRONG>Module:</STRONG></A> mod_log_config</p>

 <p>The <code>CustomLog</code> 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 on one of the following two
 types of values:</p>

 <dl>
 <dt><em>file</em>
 <dd>A filename, relative to the
 <a href="core.html#serverroot">ServerRoot</a>.</dd>

 <dt><em>pipe</em>
 <dd>The pipe character "<code>|</code>", followed by the path to a
 program to receive the log information on its standard input.
 <STRONG>Security:</STRONG> if a program is used, then it will be run
 under the user who started httpd. This will be root if the server was
 started by root; be sure that the program is secure.</dd>
 </dl>

 <P>The second argument specifies what will be written to the
 log file.  It can specify either a <em>nickname</em>
 defined by a previous <a href="#logformat">LogFormat</a>
 directive, or it can be an explicit <em>format</em> 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>

 <pre>
      # CustomLog with format nickname
      LogFormat &quot;%h %l %u %t \&quot;%r\&quot; %&gt;s %b&quot; common
      CustomLog logs/access_log common

      # CustomLog with explicit format string
      CustomLog logs/access_log &quot;%h %l %u %t \&quot;%r\&quot; %&gt;s %b&quot;
 </pre>

 <p>The third argument is optional and allows the decision on whether
 or not to log a particular request to be 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=!<EM>name</EM></CODE>' clause), then the request will be
 logged.</P>

 <P>Environment variables can be set on a <EM>per</EM>-request basis
 using the <A HREF="mod_setenvif.html">mod_setenvif</A> and/or <A
 HREF="mod_rewrite.html">mod_rewrite</A> modules.  For example, if you
 don't want to record requests for all GIF images on your server in a
 separate logfile but not your main log, you can use:
 </P>
 <PRE>
     SetEnvIf Request_URI \.gif$ gif-image
     CustomLog gif-requests.log common env=gif-image
     CustomLog nongif-requests.log common env=!gif-image
 </PRE>

 <HR>
 <H2><A NAME="logformat">LogFormat</A> directive</H2>
 <!--%plaintext &lt;?INDEX {\tt LogFormat} directive&gt; -->
 <p><A
  HREF="directive-dict.html#Syntax"
  REL="Help"
 ><STRONG>Syntax:</STRONG></A> LogFormat <EM>format</em>|<em>nickname</EM>
      [<EM>nickname</EM>]
 <BR>
 <A
  HREF="directive-dict.html#Default"
  REL="Help"
 ><STRONG>Default:</STRONG></A> <CODE>LogFormat &quot;%h %l %u %t \&quot;%r\&quot;
 %&gt;s %b&quot;</CODE><BR>
 <A
  HREF="directive-dict.html#Context"
  REL="Help"
 ><STRONG>Context:</STRONG></A> server config, virtual host<BR>
 <A
  HREF="directive-dict.html#Status"
  REL="Help"
 ><STRONG>Status:</STRONG></A> Base<BR>
 <A
  HREF="directive-dict.html#Compatibility"
  REL="Help"
 ><STRONG>Compatibility:</STRONG></A> Nickname only available in Apache 1.3
     or later
 <BR>
 <A
  HREF="directive-dict.html#Module"
  REL="Help"
 ><STRONG>Module:</STRONG></A> mod_log_config</p>

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

 <p>The <code>LogFormat</code> 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
 <a href="#transferlog">TransferLog</a> directives.  The single
 argument can specify an explicit <em>format</em> as discussed in <a
 href="#formats">custom log formats</a> section above.  Alternatively,
 it can use a <em>nickname</em> to refer to a log format defined
 in a previous <code>LogFormat</code> directive as described below.</p>

 <p>The second form of the <code>LogFormat</code> directive associates
 an explicit <em>format</em> with a <em>nickname</em>.  This
 <em>nickname</em> can then be used in subsequent
 <code>LogFormat</code> or <a href="#customlog">CustomLog</a>
 directives rather than repeating the entire format string.  A
 <SAMP>LogFormat</SAMP> directive which 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 <a
 href="#transferlog">TransferLog</a> directives.
 </P>

 <HR>

 <H2><A NAME="transferlog">TransferLog</A> directive</H2>
 <!--%plaintext &lt;?INDEX {\tt TransferLog} directive&gt; -->
 <p><A
  HREF="directive-dict.html#Syntax"
  REL="Help"
 ><STRONG>Syntax:</STRONG></A> TransferLog <EM>file</em>|<em>pipe</EM><BR>
 <A
  HREF="directive-dict.html#Default"
  REL="Help"
 ><STRONG>Default:</STRONG></A> none<BR>
 <A
  HREF="directive-dict.html#Context"
  REL="Help"
 ><STRONG>Context:</STRONG></A> server config, virtual host<BR>
 <A
  HREF="directive-dict.html#Status"
  REL="Help"
 ><STRONG>Status:</STRONG></A> Base<BR>
 <A
  HREF="directive-dict.html#Module"
  REL="Help"
 ><STRONG>Module:</STRONG></A> mod_log_config</p>

 <p>This directive has exactly the same arguments and effect as the <a
 href="#customlog">CustomLog</a> 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 specified <a
 href="#logformat">LogFormat</a> directive (which does not define a
 nickname).  Common Log Format is used if no other format has been
 specified.</p>

 <p>Example:</p>

 <pre>
    LogFormat "%h %l %u %t \"%r\" %&gt;s %b \"%{Referer}i\" \"%{User-agent}i\""
    TransferLog logs/access_log
 </pre>


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	<H1 ALIGN="CENTER">Module mod_log_config</H1>
	<P>
	This module provides for logging of the requests made to
	the server, using the Common Log Format or a user-specified format.
	</P>

	<P><A
	HREF="module-dict.html#Status"
	REL="Help"
	><STRONG>Status:</STRONG></A> Base
	<BR>
	<A
	HREF="module-dict.html#SourceFile"
	REL="Help"
	><STRONG>Source File:</STRONG></A> mod_log_config.c
	<BR>
	<A
	HREF="module-dict.html#ModuleIdentifier"
	REL="Help"
	><STRONG>Module Identifier:</STRONG></A> config_log_module
	</P>


	<H2>Summary</H2>

	<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: <CODE>TransferLog</CODE>
	to create a log file, <CODE>LogFormat</CODE> to set a custom format,
	and <CODE>CustomLog</CODE> to define a log file and format in one step.
	The <CODE>TransferLog</CODE> and <CODE>CustomLog</CODE> directives can
	be used multiple times in each server to cause each request to be
	logged to multiple files.
	</P>

	<H2>Directives</H2>

	<UL>
	<LI><A HREF="#cookielog">CookieLog</A></LI>
	<LI><A HREF="#customlog">CustomLog</A></LI>
	<LI><A HREF="#logformat">LogFormat</A></LI>
	<LI><A HREF="#transferlog">TransferLog</A></LI>
	</UL>

	<H2>Log File Formats</H2>

	<p>Unless told otherwise with <TT>LogFormat</TT>, the log files
	created by <TT>TransferLog</TT> will be in standard "Common Log
	Format" (CLF). The contents of each line in a CLF file are explained
	below. Alternatively, the log file can be customized (and if multiple
	log files are used, each can have a different format). Custom formats
	are set with <CODE>LogFormat</CODE> and <CODE>CustomLog</CODE>.</p>

	<H3>Common Log Format</H3>

	<p>The Common Log Format (CLF) file contains a separate line for each
	request. A line is composed of several tokens separated by spaces:</p>

	<BLOCKQUOTE>
	host ident authuser date request status bytes
	</BLOCKQUOTE>
	If a token does not have a value then it is represented by a hyphen (-).
	The meanings and values of these tokens are as follows:
	<DL>
	<DT>host
	<DD>The fully-qualified domain name of the client, or its IP number if the
	name is not available.
	<DT>ident
	<DD>If <A HREF="core.html#identitycheck">IdentityCheck</A> is enabled and the
	client machine runs identd, then this is the identity information reported
	by the client.
	<DT>authuser
	<DD>If the request was for an password protected document, then this is
	the userid used in the request.
	<DT>date
	<DD>The date and time of the request, in the following format:
	<DL><DD><BLOCKQUOTE><CODE> date = [day/month/year:hour:minute:second zone] <BR>
	day = 2*digit<BR>
	month = 3*letter<BR>
	year = 4*digit<BR>
	hour = 2*digit<BR>
	minute = 2*digit<BR>
	second = 2*digit<BR>
	zone = (`+' \| `-') 4*digit</CODE></BLOCKQUOTE></DL>
	<DT>request
	<DD>The request line from the client, enclosed in double quotes
	(<CODE>"</CODE>).
	<DT>status
	<DD>The three digit status code returned to the client.
	<DT>bytes
	<DD>The number of bytes in the object returned to the client, not including
	any headers.
	</DL>

	<H3><A NAME="formats">Custom Log Formats</A></H3>

	<p>The format argument to the <CODE>LogFormat</CODE> and
	<CODE>CustomLog</CODE> directives is a string. This string is logged
	to the log file for each request. It can contain literal characters
	copied into the log files and the c-type 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
	"%" directives in the format string, which are replaced in the log file
	by the values as follows:</p>

	<PRE>
	%...a: Remote IP-address
	%...A: Local IP-address
	%...B: Bytes sent, excluding HTTP headers.
	%...b: Bytes sent, excluding HTTP headers. In CLF format
	i.e. a '-' rather than a 0 when no bytes are sent.
	%...c: Connection status when response is completed.
	'X' = connection aborted before the response completed.
	'+' = connection may be kept alive after the response is sent.
	'-' = connection will be closed after the response is sent.
	%...{Foobar}C: The contents of cookie "Foobar" in the request sent to the
	server.
	%...D: The time taken to serve the request, in microseconds.
	%...{FOOBAR}e: The contents of the environment variable FOOBAR
	%...f: Filename
	%...h: Remote host
	%...H The request protocol
	%...{Foobar}i: The contents of Foobar: header line(s) in the request
	sent to the server.
	%...l: Remote logname (from identd, if supplied)
	%...m The request method
	%...{Foobar}n: The contents of note "Foobar" from another module.
	%...{Foobar}o: The contents of Foobar: header line(s) in the reply.
	%...p: The canonical Port of the server serving the request
	%...P: The process ID of the child that serviced the request.
	%...q The query string (prepended with a ? if a query string exists,
	otherwise an empty string)
	%...r: First line of request
	%...s: Status. For requests that got internally redirected, this is
	the status of the original request --- %...>s for the last.
	%...t: Time, in common log format time format (standard english format)
	%...{format}t: The time, in the form given by format, which should
	be in strftime(3) format. (potentially localized)
	%...T: The time taken to serve the request, in seconds.
	%...u: Remote user (from auth; may be bogus if return status (%s) is 401)
	%...U: The URL path requested.
	%...v: The canonical ServerName of the server serving the request.
	%...V: The server name according to the UseCanonicalName setting.
	</PRE>

	<p>The "..." 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
	User-agent: on 400 errors and 501 errors (Bad Request, Not
	Implemented) only; "%!200,304,302{Referer}i" logs Referer: on all
	requests which did <STRONG>not</STRONG> return some sort of normal
	status.</p>

	<p>Note that there is no escaping performed on the strings from
	%...r, %...i and %...o. This is mainly to comply with the requirements
	of the Common Log Format. This implies that clients can insert
	control characters into the log, so care should be taken when dealing
	with raw log files.</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 <A
	HREF="core.html#servername">ServerName</A> and <A
	HREF="core.html#port">Port</A> of the server serving the request are
	used for <CODE>%v</CODE> and <CODE>%p</CODE> respectively. This
	happens regardless of the <A
	HREF="core.html#usecanonicalname">UseCanonicalName</A> 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>

	<H2>Using Multiple Log Files</H2>

	<p>The <CODE>TransferLog</CODE> and <CODE>CustomLog</CODE> directives can
	be given more than once to log requests to multiple log files. Unless
	the conditional form of <code>CustomLog</code> is used, each
	request will be logged to all the log files defined by either of these
	directives.</p>

	<H3>Use with Virtual Hosts</H3>

	<p>If a <VirtualHost> section does not contain any
	<TT>TransferLog</TT> or <TT>CustomLog</TT> directives, the
	logs defined for the main server will be used. If it does
	contain one or more of these directives, requests serviced by
	this virtual host will only be logged in the log files defined
	within its definition, not in any of the main server's log files.
	See the examples below.</p>

	<H2>Security Considerations</H2>

	<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>

	<h2>Resetting the Log Files</h2>

	<p>The access log file typically grows 1MB or more for each 10,000
	requests. It will probably be necessary to move or delete the log
	file on a regular basis. This cannot be done while the server is
	still running, because Apache will continue writing to the old log
	file. Instead, the server must be <a
	href="../stopping.html">restarted</a> after the log file is moved or
	deleted so that it will open a new log.</p>

	<p>A typical scenario is:</p>

	<pre>
	mv access_log access_log.old
	apachectl graceful
	# wait for all requests to the old server to complete
	# before doing anything with access_log.old
	</pre>

	<p>Alternatively, log files can be <a
	href="../misc/FAQ.html#rotate">rotated automatically</a> be writing
	them through a pipe to a program designed for that purpose such
	as <a href="../programs/rotatelogs.html">rotatelogs</a>.</p>

	<HR>


	<H2><A NAME="cookielog">CookieLog</A> directive</H2>
	<!--%plaintext <?INDEX {\tt CookieLog} directive> -->
	<p><A
	HREF="directive-dict.html#Syntax"
	REL="Help"
	><STRONG>Syntax:</STRONG></A> CookieLog <EM>filename</EM><BR>
	<A
	HREF="directive-dict.html#Context"
	REL="Help"
	><STRONG>Context:</STRONG></A> server config, virtual host<BR>
	<A
	HREF="directive-dict.html#Module"
	REL="Help"
	><STRONG>Module:</STRONG></A> mod_cookies<BR>
	<A
	HREF="directive-dict.html#Compatibility"
	REL="Help"
	><STRONG>Compatibility:</STRONG></A> Only available in Apache 1.2 and above</p>

	<p>The CookieLog directive sets the filename for logging of cookies.
	The filename is relative to the <A
	HREF="core.html#serverroot">ServerRoot</A>. This directive is included
	only for compatibility with mod_cookies, and is deprecated.</p>

	<HR>
	<H2><A NAME="customlog">CustomLog</A>
	<a NAME="customlogconditional">directive</a></H2>
	<p><A
	HREF="directive-dict.html#Syntax"
	REL="Help"
	><STRONG>Syntax:</STRONG></A> CustomLog <EM>file</em>\|<em>pipe</EM>
	<EM>format</em>\|<em>nickname</EM> [env=[!]<EM>environment-variable</EM>]<BR>
	<A
	HREF="directive-dict.html#Context"
	REL="Help"
	><STRONG>Context:</STRONG></A> server config, virtual host<BR>
	<A
	HREF="directive-dict.html#Status"
	REL="Help"
	><STRONG>Status:</STRONG></A> Base<BR>
	<A
	HREF="directive-dict.html#Compatibility"
	REL="Help"
	><STRONG>Compatibility:</STRONG></A> Nickname only available in Apache 1.3
	or later. Conditional logging available in 1.3.5 or later.
	<BR>
	<A
	HREF="directive-dict.html#Module"
	REL="Help"
	><STRONG>Module:</STRONG></A> mod_log_config</p>

	<p>The <code>CustomLog</code> 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 on one of the following two
	types of values:</p>

	<dl>
	<dt><em>file</em>
	<dd>A filename, relative to the
	<a href="core.html#serverroot">ServerRoot</a>.</dd>

	<dt><em>pipe</em>
	<dd>The pipe character "<code>\|</code>", followed by the path to a
	program to receive the log information on its standard input.
	<STRONG>Security:</STRONG> if a program is used, then it will be run
	under the user who started httpd. This will be root if the server was
	started by root; be sure that the program is secure.</dd>
	</dl>

	<P>The second argument specifies what will be written to the
	log file. It can specify either a <em>nickname</em>
	defined by a previous <a href="#logformat">LogFormat</a>
	directive, or it can be an explicit <em>format</em> 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>

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

	# CustomLog with explicit format string
	CustomLog logs/access_log "%h %l %u %t \"%r\" %>s %b"
	</pre>

	<p>The third argument is optional and allows the decision on whether
	or not to log a particular request to be 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=!<EM>name</EM></CODE>' clause), then the request will be
	logged.</P>

	<P>Environment variables can be set on a <EM>per</EM>-request basis
	using the <A HREF="mod_setenvif.html">mod_setenvif</A> and/or <A
	HREF="mod_rewrite.html">mod_rewrite</A> modules. For example, if you
	don't want to record requests for all GIF images on your server in a
	separate logfile but not your main log, you can use:
	</P>
	<PRE>
	SetEnvIf Request_URI \.gif$ gif-image
	CustomLog gif-requests.log common env=gif-image
	CustomLog nongif-requests.log common env=!gif-image
	</PRE>

	<HR>
	<H2><A NAME="logformat">LogFormat</A> directive</H2>
	<!--%plaintext <?INDEX {\tt LogFormat} directive> -->
	<p><A
	HREF="directive-dict.html#Syntax"
	REL="Help"
	><STRONG>Syntax:</STRONG></A> LogFormat <EM>format</em>\|<em>nickname</EM>
	[<EM>nickname</EM>]
	<BR>
	<A
	HREF="directive-dict.html#Default"
	REL="Help"
	><STRONG>Default:</STRONG></A> <CODE>LogFormat "%h %l %u %t \"%r\"
	%>s %b"</CODE><BR>
	<A
	HREF="directive-dict.html#Context"
	REL="Help"
	><STRONG>Context:</STRONG></A> server config, virtual host<BR>
	<A
	HREF="directive-dict.html#Status"
	REL="Help"
	><STRONG>Status:</STRONG></A> Base<BR>
	<A
	HREF="directive-dict.html#Compatibility"
	REL="Help"
	><STRONG>Compatibility:</STRONG></A> Nickname only available in Apache 1.3
	or later
	<BR>
	<A
	HREF="directive-dict.html#Module"
	REL="Help"
	><STRONG>Module:</STRONG></A> mod_log_config</p>

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

	<p>The <code>LogFormat</code> 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
	<a href="#transferlog">TransferLog</a> directives. The single
	argument can specify an explicit <em>format</em> as discussed in <a
	href="#formats">custom log formats</a> section above. Alternatively,
	it can use a <em>nickname</em> to refer to a log format defined
	in a previous <code>LogFormat</code> directive as described below.</p>

	<p>The second form of the <code>LogFormat</code> directive associates
	an explicit <em>format</em> with a <em>nickname</em>. This
	<em>nickname</em> can then be used in subsequent
	<code>LogFormat</code> or <a href="#customlog">CustomLog</a>
	directives rather than repeating the entire format string. A
	<SAMP>LogFormat</SAMP> directive which 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 <a
	href="#transferlog">TransferLog</a> directives.
	</P>

	<HR>

	<H2><A NAME="transferlog">TransferLog</A> directive</H2>
	<!--%plaintext <?INDEX {\tt TransferLog} directive> -->
	<p><A
	HREF="directive-dict.html#Syntax"
	REL="Help"
	><STRONG>Syntax:</STRONG></A> TransferLog <EM>file</em>\|<em>pipe</EM><BR>
	<A
	HREF="directive-dict.html#Default"
	REL="Help"
	><STRONG>Default:</STRONG></A> none<BR>
	<A
	HREF="directive-dict.html#Context"
	REL="Help"
	><STRONG>Context:</STRONG></A> server config, virtual host<BR>
	<A
	HREF="directive-dict.html#Status"
	REL="Help"
	><STRONG>Status:</STRONG></A> Base<BR>
	<A
	HREF="directive-dict.html#Module"
	REL="Help"
	><STRONG>Module:</STRONG></A> mod_log_config</p>

	<p>This directive has exactly the same arguments and effect as the <a
	href="#customlog">CustomLog</a> 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 specified <a
	href="#logformat">LogFormat</a> directive (which does not define a
	nickname). Common Log Format is used if no other format has been
	specified.</p>

	<p>Example:</p>

	<pre>
	LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\""
	TransferLog logs/access_log
	</pre>


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