Major update of mod_log_config docs.

HREF="module-dict.html#ModuleIdentifier"

REL="Help"

><STRONG>Module Identifier:</STRONG></A> config_log_module

<BR>

<A

HREF="module-dict.html#Compatibility"

REL="Help"

><STRONG>Compatibility:</STRONG></A> Was an extension module prior to Apache 1.2.

</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 go.

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.

<H2>Directives</H2>

<UL>

<LI><A HREF="#cookielog">CookieLog</A>

<LI><A HREF="#customlog">CustomLog</A>

<LI><A HREF="#customlog-conditional">CustomLog (conditional)</A>

<LI><A HREF="#logformat">LogFormat</A>

<LI><A HREF="#transferlog">TransferLog</A>

</UL>

<H3>Compatibility notes</H3>

<UL>

<LI>This module is based on mod_log_config distributed with

previous Apache releases, now updated to handle multiple logs.

There is now no need to re-configure Apache to use configuration log

formats.

<LI>The module also implements the <CODE>CookieLog</CODE> directive,

used to log user-tracking information created by <A

HREF="mod_usertrack.html">mod_usertrack</A>. The use of

<CODE>CookieLog</CODE> is deprecated, and a <CODE>CustomLog</CODE>

should be defined to log user-tracking information instead.

<LI>As of Apache 1.3.5, this module allows conditional logging

based upon the setting of environment variables.  That is,

you can control whether a request should be logged or not

based upon whether an arbitrary environment variable is

defined or not.  This is settable on a <EM>per</EM>-logfile

basis.

<LI>Beginning with Apache 1.3.5, the mod_log_config module has

also subsumed the <CODE>RefererIgnore</CODE> functionality from

<A HREF="mod_log_referer.html">mod_log_referer</A>.  The effect

of <CODE>RefererIgnore</CODE> can be achieved by combinations of

<A HREF="mod_setenvif.html"><CODE>SetEnvIf</CODE></A> directives

and conditional <CODE>CustomLog</CODE> definitions.

<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>

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

<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>.

are set with <CODE>LogFormat</CODE> and <CODE>CustomLog</CODE>.</p>

<H3>Common Log Format</H3>

The Common Log Format (CLF) file contains a separate line for each

request. A line is composed of several tokens separated by spaces:

<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

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

The format argument to the <CODE>LogFormat</CODE> and

<CODE>CustomLog</CODE> 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 `%' directives which are replaced in the log file

by the values as follows:

<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

                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 localised)

                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 server name according to the UseCanonicalName setting.

</PRE>

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).  Note that

there is no escaping performed on the strings from %r, %...i and

%...o; some with long memories may remember that I thought this was

a bad idea, once upon a time, and I'm still not comfortable with

it, but it is difficult to see how to `do the right thing' with all

of `%..i', unless we URL-escape everything and break with CLF.

<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>

<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>

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

<P>

<dl>

<dt>Common Log Format (CLF)</dt>

<dd><CODE>"%h %l %u %t \"%r\" %&gt;s %b"</CODE></dd>

Note that the common log format is defined by the string <CODE>"%h %l

%u %t \"%r\" %>s %b"</CODE>, which can be used as the basis for

extending for format if desired (<EM>e.g.</EM>, to add extra fields at the end).

NCSA's extended/combined log format would be <CODE>"%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\""</CODE>.

<dt>Common Log Format with Virtual Host</dt>

<dd><code>"%v %h %l %u %t \"%r\" %&gt;s %b"</CODE></dd>

<P>

<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>

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

<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.

the request.</p>

<H2>Using Multiple Log Files</H2>

The <CODE>TransferLog</CODE> and <CODE>CustomLog</CODE> directives can

be given more than once to log requests to multiple log files. Each

<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.

directives.</p>

<H3>Use with Virtual Hosts</H3>

If a <VirtualHost> section does not contain any

<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>

See the examples below.</p>

<H2>Security Considerations</H2>

See the <A HREF="../misc/security_tips.html#serverroot">security tips</A>

<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>

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.</p>

<HR>

<A

 HREF="directive-dict.html#Compatibility"

 REL="Help"

><STRONG>Compatibility:</STRONG></A> Only available in Apache 1.2 and above<P>

><STRONG>Compatibility:</STRONG></A> Only available in Apache 1.2 and above</p>

The CookieLog directive sets the filename for logging of cookies.

<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 HREF="mod_cookies.html">mod_cookies</A>, and is deprecated.

<P>

only for compatibility with <A

HREF="mod_cookies.html">mod_cookies</A>, and is deprecated.</p>

<HR>

<H2><A NAME="customlog">CustomLog</A> directive</H2>

<A

<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-pipe</EM>

    <EM>format-or-nickname</EM><BR>

><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"

 HREF="directive-dict.html#Compatibility"

 REL="Help"

><STRONG>Compatibility:</STRONG></A> Nickname only available in Apache 1.3

    or later

    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>

The first argument is the filename to which log records should be

written. This is used

exactly like the argument to

<A

 HREF="#transferlog"

><SAMP>TransferLog</SAMP></A>;

that is, it is either a full path or relative to the current

server root.

</P>

<P>

The format argument specifies a format for each line of the log file.

The options available for the format are exactly the same as for

the argument of the <TT>LogFormat</TT> directive. If the format

includes any spaces (which it will do in almost all cases) it

should be enclosed in double quotes.

</P>

<P>

Instead of an actual format string, you can use a format nickname defined with

the

<A

 HREF="#logformat"

><SAMP>LogFormat</SAMP></A>

directive.

</P>

<HR>

<H2><A NAME="customlog-conditional">CustomLog (conditional)</A> directive</H2>

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> CustomLog <EM>file-pipe</EM>

    <EM>format-or-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> Only available in Apache 1.3.5

    or later

<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mod_log_config

<P>

The behaviour of this form of the <SAMP>CustomLog</SAMP> directive is almost

identical to the <A HREF="#customlog">standard <CODE>CustomLog</CODE></A>

directive.  The difference is that the '<CODE>env=</CODE>' clause controls

whether a particular request will be logged in the specified file or

not.  If the specified environment variable 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:

><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

<HR>

<H2><A NAME="logformat">LogFormat</A> directive</H2>

<!--%plaintext &lt;?INDEX {\tt LogFormat} directive&gt; -->

<A

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> LogFormat <EM>format</EM> [<EM>nickname</EM>]

><STRONG>Syntax:</STRONG></A> LogFormat <EM>format</em>|<em>nickname</EM>

     [<EM>nickname</EM>]

<BR>

<A

 HREF="directive-dict.html#Default"

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mod_log_config

<P>

This sets the format of the default logfile named by the

<A

 HREF="#transferlog"

><SAMP>TransferLog</SAMP></A>

directive .  See the section on

<A HREF="#formats">Custom Log Formats</A> for details on the format

arguments.

</P>

<P>

If you include a nickname for the format on the directive line, you can

use it in other <SAMP>LogFormat</SAMP> and

<A HREF="#customlog"><SAMP>CustomLog</SAMP></A>

directives rather than repeating the entire format string.

</P>

<P>

A

><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.

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; -->

<A

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> TransferLog <EM>file-pipe</EM><BR>

><STRONG>Syntax:</STRONG></A> TransferLog <EM>file</em>|<em>pipe</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

<A

 HREF="directive-dict.html#Module"

 REL="Help"

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

The TransferLog directive adds a log file in the format defined by the

most recent

<A

 HREF="#logformat"

><SAMP>LogFormat</SAMP></A>

directive, or Common Log Format if no other default format has been

specified.

<EM>File-pipe</EM> is one

of

<DL><DT>A filename

<DD>A filename relative to the <A HREF="core.html#serverroot">ServerRoot</A>.

<DT> `|' followed by a command

<DD>A program to receive the agent log information on its standard input.

Note the a new program will not be started for a VirtualHost if it inherits

the TransferLog from the main server.

</DL>

<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.<P>

><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.  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\""

   TranferLog logs/access_log

</pre>

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