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apache/docs/manual/mod/mod_log_config.html.en
Joshua Slive fff70685e9 Document the ability to look at original of final subrequest. 
I'd appreciate a review from someone more familiar with
mod_log_config!

PR: 27319


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@103086 13f79535-47bb-0310-9956-ffa450edef68
2004-03-22 22:06:55 +00:00

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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
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<div id="page-content">
<div id="preamble"><h1>Apache Module mod_log_config</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_log_config.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../ja/mod/mod_log_config.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Logging of the requests made to the server</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module<EFBFBD>Identifier:</a></th><td>log_config_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source<EFBFBD>File:</a></th><td>mod_log_config.c</td></tr></table>
<h3>Summary</h3>
<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 class="directive"><a href="#transferlog">TransferLog</a></code> to create
a log file, <code class="directive"><a href="#logformat">LogFormat</a></code>
to set a custom format, and <code class="directive"><a href="#customlog">CustomLog</a></code> to define a log file and format in one
step. The <code class="directive">TransferLog</code> and <code class="directive">CustomLog</code> directives can be used multiple times in each
server to cause each request to be logged to multiple files.</p>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#cookielog">CookieLog</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#customlog">CustomLog</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#logformat">LogFormat</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#transferlog">TransferLog</a></li>
</ul>
<h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#formats">Custom Log Formats</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#security">Security Considerations</a></li>
</ul><h3>See also</h3>
<ul class="seealso">
<li><a href="../logs.html">Apache Log Files</a></li>
</ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="formats" id="formats">Custom Log Formats</a></h2>
<p>The format argument to the <code class="directive"><a href="#logformat">LogFormat</a></code> and <code class="directive"><a href="#customlog">CustomLog</a></code> 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 class="bordered"><tr class="header"><th>Format&nbsp;String</th>
<th>Description</th></tr>
<tr><td><code>%%</code></td>
<td>The percent sign</td></tr>
<tr class="odd"><td><code>%...a</code></td>
<td>Remote IP-address</td></tr>
<tr><td><code>%...A</code></td>
<td>Local IP-address</td></tr>
<tr class="odd"><td><code>%...B</code></td>
<td>Bytes sent, excluding HTTP headers.</td></tr>
<tr><td><code>%...b</code></td>
<td>Bytes sent, excluding HTTP headers. In CLF format, <em>i.e.</em>
a '<code>-</code>' rather than a 0 when no bytes are sent.</td></tr>
<tr class="odd"><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 class="odd"><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 class="odd"><td><code>%...h</code></td>
<td>Remote host</td></tr>
<tr><td><code>%...H</code></td>
<td>The request protocol</td></tr>
<tr class="odd"><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 <code class="module"><a href="../mod/mod_ident.html">mod_ident</a></code> is present and <code class="directive"><a href="../mod/mod_ident.html#identitycheck">IdentityCheck</a></code> is set
<code>On</code>.</td></tr>
<tr class="odd"><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 class="odd"><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 class="odd"><td><code>%...P</code></td>
<td>The process ID of the child that serviced the request.</td></tr>
<tr><td><code>%...{<var>format</var>}P</code></td>
<td>The process ID or thread id of the child that serviced the
request. Valid formats are <code>pid</code> and <code>tid</code>.
</td></tr>
<tr class="odd"><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 class="odd"><td><code>%...s</code></td>
<td>Status. For requests that got internally redirected, this is
the status of the *original* request --- <code>%...&gt;s</code>
for the last.</td></tr>
<tr><td><code>%...t</code></td>
<td>Time, in common log format time format (standard english
format)</td></tr>
<tr class="odd"><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 class="odd"><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 class="odd"><td><code>%...v</code></td>
<td>The canonical <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code>
of the server serving the request.</td></tr>
<tr><td><code>%...V</code></td>
<td>The server name according to the <code class="directive"><a href="../mod/core.html#usecanonicalname">UseCanonicalName</a></code> setting.</td></tr>
<tr class="odd"><td><code>%...X</code></td>
<td>Connection status when response is completed:
<table>
<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 <code class="module"><a href="../mod/mod_logio.html">mod_logio</a></code> to use this.</td></tr>
<tr class="odd"><td><code>%...O</code></td>
<td>Bytes sent, including headers, cannot be zero. You need to
enable <code class="module"><a href="../mod/mod_logio.html">mod_logio</a></code> to use this.</td></tr>
</table>
<p>The "<var>...</var>" can be nothing at all (<em>e.g.</em>,
<code>"%h %u %r %s %b"</code>), or it can indicate conditions for
inclusion of the item (which will cause it to be replaced with "-" if
the condition is not met). The forms of condition are a list of
HTTP status codes, which may or may not be preceded by "!".
Thus, "%400,501{User-agent}i" logs <code>User-agent:</code> on 400
errors and 501 errors (Bad Request, Not Implemented) only;
"%!200,304,302{Referer}i" logs <code>Referer:</code> on all requests
which did <em>not</em> return some sort of normal status.</p>
<p>The modifiers "&lt;" and "&gt;" can be used for requests that
have been internally redirected to choose whether the original or
final (respectively) request should be consulted. By default, the
<code>%</code> directives <code>%s, %U, %T, %D,</code> and
<code>%r</code> look at the original request while all others look
at the final request. So for example, <code>%&gt;s</code> can be
used to record the final status of the request and
<code>%&lt;u</code> can be used to record the original
authenticated user on a request that is internally redirect to an
unauthenticated resource.</p>
<p>Note that in httpd 2.0 versions prior to 2.0.46, no escaping was performed
on the strings from <code>%...r</code>, <code>%...i</code> and
<code>%...o</code>. This was mainly to comply with the requirements of
the Common Log Format. This implied that clients could insert control
characters into the log, so you had to be quite careful when dealing
with raw log files.</p>
<p>For security reasons, starting with 2.0.46, non-printable and
other special characters are escaped mostly by using
<code>\x<var>hh</var></code> sequences, where <var>hh</var> stands for
the hexadecimal representation of the raw byte. Exceptions from this
rule are <code>"</code> and <code>\</code> which are escaped by prepending
a backslash, and all whitespace characters which are written in their
C-style notation (<code>\n</code>, <code>\t</code> etc).</p>
<p>Some commonly used log format strings are:</p>
<dl>
<dt>Common Log Format (CLF)</dt>
<dd><code>"%h %l %u %t \"%r\" %&gt;s %b"</code></dd>
<dt>Common Log Format with Virtual Host</dt>
<dd><code>"%v %h %l %u %t \"%r\" %&gt;s %b"</code></dd>
<dt>NCSA extended/combined log format</dt>
<dd><code>"%h %l %u %t \"%r\" %&gt;s %b \"%{Referer}i\"
\"%{User-agent}i\""</code></dd>
<dt>Referer log format</dt>
<dd><code>"%{Referer}i -&gt; %U"</code></dd>
<dt>Agent (Browser) log format</dt>
<dd><code>"%{User-agent}i"</code></dd>
</dl>
<p>Note that the canonical <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code> and <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code> of the server serving the
request are used for <code>%v</code> and <code>%p</code>
respectively. This happens regardless of the <code class="directive"><a href="../mod/core.html#usecanonicalname">UseCanonicalName</a></code> 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>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="security" id="security">Security Considerations</a></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>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="CookieLog" id="CookieLog">CookieLog</a> <a name="cookielog" id="cookielog">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets filename for the logging of cookies</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CookieLog <var>filename</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>This directive is deprecated.</td></tr>
</table>
<p>The <code class="directive">CookieLog</code> directive sets the
filename for logging of cookies. The filename is relative to the
<code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>. This directive is
included only for compatibility with <code>mod_cookies</code>,
and is deprecated.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="CustomLog" id="CustomLog">CustomLog</a> <a name="customlog" id="customlog">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets filename and format of log file</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CustomLog <var>file</var>|<var>pipe</var>
<var>format</var>|<var>nickname</var>
[env=[!]<var>environment-variable</var>]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
</table>
<p>The <code class="directive">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 one of the following two
types of values:</p>
<dl>
<dt><var>file</var></dt>
<dd>A filename, relative to the <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</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.
<div class="warning"><h3>Security:</h3>
<p>If a program is used, then it will be run as the user who
started httpd. This will be root if the server was started by root;
be sure that the program is secure.</p>
</div>
<div class="warning"><h3>Note</h3>
<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>
</div></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 <code class="directive"><a href="#logformat">LogFormat</a></code>
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>
<div class="example"><p><code>
# 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"
</code></p></div>
<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 <code class="module"><a href="../mod/mod_setenvif.html">mod_setenvif</a></code>
and/or <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> 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>
<div class="example"><p><code>
SetEnvIf Request_URI \.gif$ gif-image<br />
CustomLog gif-requests.log common env=gif-image<br />
CustomLog nongif-requests.log common env=!gif-image
</code></p></div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="LogFormat" id="LogFormat">LogFormat</a> <a name="logformat" id="logformat">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Describes a format for use in a log file</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LogFormat <var>format</var>|<var>nickname</var>
[<var>nickname</var>]</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LogFormat "%h %l %u %t \"%r\" %&gt;s %b"</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
</table>
<p>This directive specifies the format of the access log
file.</p>
<p>The <code class="directive">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 <code class="directive">TransferLog</code>
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 <code class="directive">LogFormat</code> directive as described
below.</p>
<p>The second form of the <code class="directive">LogFormat</code>
directive associates an explicit <var>format</var> with a
<var>nickname</var>. This <var>nickname</var> can then be used in
subsequent <code class="directive">LogFormat</code> or
<code class="directive"><a href="#customlog">CustomLog</a></code> directives
rather than repeating the entire format string. A
<code class="directive">LogFormat</code> 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
<code class="directive"><a href="#transferlog">TransferLog</a></code> directives.
In addition, <code class="directive">LogFormat</code> cannot use one nickname
to define another nickname. Note that the nickname should not contain
percent signs (<code>%</code>).</p>
<div class="example"><h3>Example</h3><p><code>
LogFormat "%v %h %l %u %t \"%r\" %&gt;s %b" vhost_common
</code></p></div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="TransferLog" id="TransferLog">TransferLog</a> <a name="transferlog" id="transferlog">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify location of a log file</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>TransferLog <var>file</var>|<var>pipe</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
</table>
<p>This directive has exactly the same arguments and effect as
the <code class="directive"><a href="#customlog">CustomLog</a></code>
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
<code class="directive"><a href="#logformat">LogFormat</a></code> directive
which does not define a nickname. Common Log Format is used if no
other format has been specified.</p>
<div class="example"><h3>Example</h3><p><code>
LogFormat "%h %l %u %t \"%r\" %&gt;s %b \"%{Referer}i\" \"%{User-agent}i\""<br />
TransferLog logs/access_log
</code></p></div>
</div>
</div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/mod/mod_log_config.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../ja/mod/mod_log_config.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
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