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6 Copyright 2002-2004 The Apache Software Foundation
8 Licensed under the Apache License, Version 2.0 (the "License");
9 you may not use this file except in compliance with the License.
10 You may obtain a copy of the License at
12 http://www.apache.org/licenses/LICENSE-2.0
14 Unless required by applicable law or agreed to in writing, software
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16 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 See the License for the specific language governing permissions and
18 limitations under the License.
21 <modulesynopsis metafile="mod_log_config.xml.meta">
23 <name>mod_log_config</name>
24 <description>Logging of the requests made to the server</description>
26 <sourcefile>mod_log_config.c</sourcefile>
27 <identifier>log_config_module</identifier>
30 <p>This module provides for flexible logging of client
31 requests. Logs are written in a customizable format, and may be
32 written directly to a file, or to an external program.
33 Conditional logging is provided so that individual requests may
34 be included or excluded from the logs based on characteristics
37 <p>Three directives are provided by this module:
38 <directive module="mod_log_config">TransferLog</directive> to create
39 a log file, <directive module="mod_log_config">LogFormat</directive>
40 to set a custom format, and <directive module="mod_log_config"
41 >CustomLog</directive> to define a log file and format in one
42 step. The <directive>TransferLog</directive> and <directive
43 >CustomLog</directive> directives can be used multiple times in each
44 server to cause each request to be logged to multiple files.</p>
46 <seealso><a href="../logs.html">Apache Log Files</a></seealso>
48 <section id="formats"><title>Custom Log Formats</title>
50 <p>The format argument to the <directive module="mod_log_config"
51 >LogFormat</directive> and <directive module="mod_log_config"
52 >CustomLog</directive> directives is a string. This string is
53 used to log each request to the log file. It can contain literal
54 characters copied into the log files and the C-style control
55 characters "\n" and "\t" to represent new-lines and tabs.
56 Literal quotes and back-slashes should be escaped with
59 <p>The characteristics of the request itself are logged by
60 placing "<code>%</code>" directives in the format string, which are
61 replaced in the log file by the values as follows:</p>
63 <table border="1" style="zebra">
64 <columnspec><column width=".2"/><column width=".8"/></columnspec>
65 <tr><th>Format String</th>
66 <th>Description</th></tr>
68 <tr><td><code>%%</code></td>
69 <td>The percent sign</td></tr>
71 <tr><td><code>%...a</code></td>
72 <td>Remote IP-address</td></tr>
74 <tr><td><code>%...A</code></td>
75 <td>Local IP-address</td></tr>
77 <tr><td><code>%...B</code></td>
78 <td>Bytes sent, excluding HTTP headers.</td></tr>
80 <tr><td><code>%...b</code></td>
81 <td>Bytes sent, excluding HTTP headers. In CLF format, <em>i.e.</em>
82 a '<code>-</code>' rather than a 0 when no bytes are sent.</td></tr>
84 <tr><td><code>%...{<var>Foobar</var>}C</code></td>
85 <td>The contents of cookie <var>Foobar</var> in the request sent
86 to the server.</td></tr>
88 <tr><td><code>%...D</code></td>
89 <td>The time taken to serve the request, in microseconds.</td></tr>
91 <tr><td><code>%...{<var>FOOBAR</var>}e</code></td>
92 <td>The contents of the environment variable
93 <var>FOOBAR</var></td></tr>
95 <tr><td><code>%...f</code></td>
96 <td>Filename</td></tr>
98 <tr><td><code>%...h</code></td>
99 <td>Remote host</td></tr>
101 <tr><td><code>%...H</code></td>
102 <td>The request protocol</td></tr>
104 <tr><td><code>%...{<var>Foobar</var>}i</code></td>
105 <td>The contents of <code><var>Foobar</var>:</code> header line(s)
106 in the request sent to the server.</td></tr>
108 <tr><td><code>%...l</code></td>
109 <td>Remote logname (from identd, if supplied). This will return a
110 dash unless <module>mod_ident</module> is present and <directive
111 module="mod_ident">IdentityCheck</directive> is set
112 <code>On</code>.</td></tr>
114 <tr><td><code>%...m</code></td>
115 <td>The request method</td></tr>
117 <tr><td><code>%...{<var>Foobar</var>}n</code></td>
118 <td>The contents of note <var>Foobar</var> from another
121 <tr><td><code>%...{<var>Foobar</var>}o</code></td>
122 <td>The contents of <code><var>Foobar</var>:</code> header line(s)
123 in the reply.</td></tr>
125 <tr><td><code>%...p</code></td>
126 <td>The canonical port of the server serving the request</td></tr>
128 <tr><td><code>%...P</code></td>
129 <td>The process ID of the child that serviced the request.</td></tr>
131 <tr><td><code>%...{<var>format</var>}P</code></td>
132 <td>The process ID or thread id of the child that serviced the
133 request. Valid formats are <code>pid</code> and <code>tid</code>.
136 <tr><td><code>%...q</code></td>
137 <td>The query string (prepended with a <code>?</code> if a query
138 string exists, otherwise an empty string)</td></tr>
140 <tr><td><code>%...r</code></td>
141 <td>First line of request</td></tr>
143 <tr><td><code>%...s</code></td>
144 <td>Status. For requests that got internally redirected, this is
145 the status of the *original* request --- <code>%...>s</code>
146 for the last.</td></tr>
148 <tr><td><code>%...t</code></td>
149 <td>Time, in common log format time format (standard english
152 <tr><td><code>%...{<var>format</var>}t</code></td>
153 <td>The time, in the form given by format, which should be in
154 <code>strftime(3)</code> format. (potentially localized)</td></tr>
156 <tr><td><code>%...T</code></td>
157 <td>The time taken to serve the request, in seconds.</td></tr>
159 <tr><td><code>%...u</code></td>
160 <td>Remote user (from auth; may be bogus if return status
161 (<code>%s</code>) is 401)</td></tr>
163 <tr><td><code>%...U</code></td>
164 <td>The URL path requested, not including any query string.</td></tr>
166 <tr><td><code>%...v</code></td>
167 <td>The canonical <directive module="core">ServerName</directive>
168 of the server serving the request.</td></tr>
170 <tr><td><code>%...V</code></td>
171 <td>The server name according to the <directive module="core"
172 >UseCanonicalName</directive> setting.</td></tr>
174 <tr><td><code>%...X</code></td>
175 <td>Connection status when response is completed:
178 <columnspec><column width=".2"/><column width=".6"/></columnspec>
179 <tr><td><code>X</code> =</td>
180 <td>connection aborted before the response completed.</td></tr>
181 <tr><td><code>+</code> =</td>
182 <td>connection may be kept alive after the response is
184 <tr><td><code>-</code> = </td>
185 <td>connection will be closed after the response is
189 <p>(This directive was <code>%...c</code> in late versions of Apache
190 1.3, but this conflicted with the historical ssl
191 <code>%...{<var>var</var>}c</code> syntax.)</p></td></tr>
193 <tr><td><code>%...I</code></td>
194 <td>Bytes received, including request and headers, cannot be zero.
195 You need to enable <module>mod_logio</module> to use this.</td></tr>
197 <tr><td><code>%...O</code></td>
198 <td>Bytes sent, including headers, cannot be zero. You need to
199 enable <module>mod_logio</module> to use this.</td></tr>
202 <p>The "<var>...</var>" can be nothing at all (<em>e.g.</em>,
203 <code>"%h %u %r %s %b"</code>), or it can indicate conditions for
204 inclusion of the item (which will cause it to be replaced with "-" if
205 the condition is not met). The forms of condition are a list of
206 HTTP status codes, which may or may not be preceded by "!".
207 Thus, "%400,501{User-agent}i" logs <code>User-agent:</code> on 400
208 errors and 501 errors (Bad Request, Not Implemented) only;
209 "%!200,304,302{Referer}i" logs <code>Referer:</code> on all requests
210 which did <em>not</em> return some sort of normal status.</p>
212 <p>Note that in httpd 2.0 versions prior to 2.0.46, no escaping was performed
213 on the strings from <code>%...r</code>, <code>%...i</code> and
214 <code>%...o</code>. This was mainly to comply with the requirements of
215 the Common Log Format. This implied that clients could insert control
216 characters into the log, so you had to be quite careful when dealing
217 with raw log files.</p>
219 <p>For security reasons, starting with 2.0.46, non-printable and
220 other special characters are escaped mostly by using
221 <code>\x<var>hh</var></code> sequences, where <var>hh</var> stands for
222 the hexadecimal representation of the raw byte. Exceptions from this
223 rule are <code>"</code> and <code>\</code> which are escaped by prepending
224 a backslash, and all whitespace characters which are written in their
225 C-style notation (<code>\n</code>, <code>\t</code> etc).</p>
227 <p>Some commonly used log format strings are:</p>
230 <dt>Common Log Format (CLF)</dt>
231 <dd><code>"%h %l %u %t \"%r\" %>s %b"</code></dd>
233 <dt>Common Log Format with Virtual Host</dt>
234 <dd><code>"%v %h %l %u %t \"%r\" %>s %b"</code></dd>
236 <dt>NCSA extended/combined log format</dt>
237 <dd><code>"%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
238 \"%{User-agent}i\""</code></dd>
240 <dt>Referer log format</dt>
241 <dd><code>"%{Referer}i -> %U"</code></dd>
243 <dt>Agent (Browser) log format</dt>
244 <dd><code>"%{User-agent}i"</code></dd>
247 <p>Note that the canonical <directive module="core"
248 >ServerName</directive> and <directive module="mpm_common"
249 >Listen</directive> of the server serving the
250 request are used for <code>%v</code> and <code>%p</code>
251 respectively. This happens regardless of the <directive
252 module="core">UseCanonicalName</directive> setting
253 because otherwise log analysis programs would have to duplicate
254 the entire vhost matching algorithm in order to decide what
255 host really served the request.</p>
258 <section id="security"><title>Security Considerations</title>
260 href="../misc/security_tips.html#serverroot">security tips</a>
261 document for details on why your security could be compromised
262 if the directory where logfiles are stored is writable by
263 anyone other than the user that starts the server.</p>
267 <name>CookieLog</name>
268 <description>Sets filename for the logging of cookies</description>
269 <syntax>CookieLog <var>filename</var></syntax>
270 <contextlist><context>server config</context><context>virtual host</context>
272 <compatibility>This directive is deprecated.</compatibility>
275 <p>The <directive>CookieLog</directive> directive sets the
276 filename for logging of cookies. The filename is relative to the
277 <directive module="core">ServerRoot</directive>. This directive is
278 included only for compatibility with <code>mod_cookies</code>,
279 and is deprecated.</p>
284 <name>CustomLog</name>
285 <description>Sets filename and format of log file</description>
286 <syntax>CustomLog <var>file</var>|<var>pipe</var>
287 <var>format</var>|<var>nickname</var>
288 [env=[!]<var>environment-variable</var>]</syntax>
289 <contextlist><context>server config</context><context>virtual host</context>
293 <p>The <directive>CustomLog</directive> directive is used to
294 log requests to the server. A log format is specified, and the
295 logging can optionally be made conditional on request
296 characteristics using environment variables.</p>
298 <p>The first argument, which specifies the location to which
299 the logs will be written, can take one of the following two
303 <dt><var>file</var></dt>
304 <dd>A filename, relative to the <directive module="core"
305 >ServerRoot</directive>.</dd>
307 <dt><var>pipe</var></dt>
308 <dd>The pipe character "<code>|</code>", followed by the path
309 to a program to receive the log information on its standard
312 <note type="warning"><title>Security:</title>
313 <p>If a program is used, then it will be run as the user who
314 started httpd. This will be root if the server was started by root;
315 be sure that the program is secure.</p>
317 <note type="warning"><title>Note</title>
318 <p>When entering a file path on non-Unix platforms, care should be taken
319 to make sure that only forward slashed are used even though the platform
320 may allow the use of back slashes. In general it is a good idea to always
321 use forward slashes throughout the configuration files.</p>
325 <p>The second argument specifies what will be written to the
326 log file. It can specify either a <var>nickname</var> defined by
327 a previous <directive module="mod_log_config">LogFormat</directive>
328 directive, or it can be an explicit <var>format</var> string as
329 described in the <a href="#formats">log formats</a> section.</p>
331 <p>For example, the following two sets of directives have
332 exactly the same effect:</p>
335 # CustomLog with format nickname<br />
336 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
337 CustomLog logs/access_log common<br />
339 # CustomLog with explicit format string<br />
340 CustomLog logs/access_log "%h %l %u %t \"%r\" %>s %b"
343 <p>The third argument is optional and controls whether or
344 not to log a particular request based on the
345 presence or absence of a particular variable in the server
346 environment. If the specified <a href="../env.html">environment
347 variable</a> is set for the request (or is not set, in the case
348 of a '<code>env=!<var>name</var></code>' clause), then the
349 request will be logged.</p>
351 <p>Environment variables can be set on a per-request
352 basis using the <module>mod_setenvif</module>
353 and/or <module>mod_rewrite</module> modules. For
354 example, if you want to record requests for all GIF
355 images on your server in a separate logfile but not in your main
356 log, you can use:</p>
359 SetEnvIf Request_URI \.gif$ gif-image<br />
360 CustomLog gif-requests.log common env=gif-image<br />
361 CustomLog nongif-requests.log common env=!gif-image
367 <name>LogFormat</name>
368 <description>Describes a format for use in a log file</description>
369 <syntax>LogFormat <var>format</var>|<var>nickname</var>
370 [<var>nickname</var>]</syntax>
371 <default>LogFormat "%h %l %u %t \"%r\" %>s %b"</default>
372 <contextlist><context>server config</context><context>virtual host</context>
376 <p>This directive specifies the format of the access log
379 <p>The <directive>LogFormat</directive> directive can take one of two
380 forms. In the first form, where only one argument is specified,
381 this directive sets the log format which will be used by logs
382 specified in subsequent <directive>TransferLog</directive>
383 directives. The single argument can specify an explicit
384 <var>format</var> as discussed in the <a href="#formats">custom log
385 formats</a> section above. Alternatively, it can use a
386 <var>nickname</var> to refer to a log format defined in a
387 previous <directive>LogFormat</directive> directive as described
390 <p>The second form of the <directive>LogFormat</directive>
391 directive associates an explicit <var>format</var> with a
392 <var>nickname</var>. This <var>nickname</var> can then be used in
393 subsequent <directive>LogFormat</directive> or
394 <directive module="mod_log_config">CustomLog</directive> directives
395 rather than repeating the entire format string. A
396 <directive>LogFormat</directive> directive that defines a nickname
397 <strong>does nothing else</strong> -- that is, it <em>only</em>
398 defines the nickname, it doesn't actually apply the format and make
399 it the default. Therefore, it will not affect subsequent
400 <directive module="mod_log_config">TransferLog</directive> directives.
401 In addition, <directive>LogFormat</directive> cannot use one nickname
402 to define another nickname. Note that the nickname should not contain
403 percent signs (<code>%</code>).</p>
405 <example><title>Example</title>
406 LogFormat "%v %h %l %u %t \"%r\" %>s %b" vhost_common
412 <name>TransferLog</name>
413 <description>Specify location of a log file</description>
414 <syntax>TransferLog <var>file</var>|<var>pipe</var></syntax>
415 <contextlist><context>server config</context><context>virtual host</context>
419 <p>This directive has exactly the same arguments and effect as
420 the <directive module="mod_log_config">CustomLog</directive>
421 directive, with the exception that it does not allow the log format
422 to be specified explicitly or for conditional logging of requests.
423 Instead, the log format is determined by the most recently specified
424 <directive module="mod_log_config">LogFormat</directive> directive
425 which does not define a nickname. Common Log Format is used if no
426 other format has been specified.</p>
428 <example><title>Example</title>
429 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\""<br />
430 TransferLog logs/access_log