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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"
<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
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:
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.
%...{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>
%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
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>
<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#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>
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
them through a pipe to a program designed for that purpose such
<HR>
<H2><A NAME="cookielog">CookieLog</A> directive</H2>
<!--%plaintext <?INDEX {\tt CookieLog} directive> -->
<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 <A
<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
<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
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
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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