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22 <div id="preamble"><h1>Apache Module mod_log_config</h1>
23 <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>
24 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
25 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>log_config_module</td></tr>
26 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_log_config.c</td></tr></table>
29 <p>This module provides for flexible logging of client
30 requests. Logs are written in a customizable format, and may be
31 written directly to a file, or to an external program.
32 Conditional logging is provided so that individual requests may
33 be included or excluded from the logs based on characteristics
36 <p>Three directives are provided by this module:
37 <code class="directive"><a href="#transferlog">TransferLog</a></code> to create
38 a log file, <code class="directive"><a href="#logformat">LogFormat</a></code>
39 to set a custom format, and <code class="directive"><a href="#customlog">CustomLog</a></code> to define a log file and format in one
40 step. The <code class="directive">TransferLog</code> and <code class="directive">CustomLog</code> directives can be used multiple times in each
41 server to cause each request to be logged to multiple files.</p>
43 <div id="quickview"><h3 class="directives">Directives</h3>
45 <li><img alt="" src="../images/down.gif" /> <a href="#cookielog">CookieLog</a></li>
46 <li><img alt="" src="../images/down.gif" /> <a href="#customlog">CustomLog</a></li>
47 <li><img alt="" src="../images/down.gif" /> <a href="#logformat">LogFormat</a></li>
48 <li><img alt="" src="../images/down.gif" /> <a href="#transferlog">TransferLog</a></li>
52 <li><img alt="" src="../images/down.gif" /> <a href="#formats">Custom Log Formats</a></li>
53 <li><img alt="" src="../images/down.gif" /> <a href="#security">Security Considerations</a></li>
54 </ul><h3>See also</h3>
56 <li><a href="../logs.html">Apache Log Files</a></li>
58 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
60 <h2><a name="formats" id="formats">Custom Log Formats</a></h2>
62 <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
63 logged to the log file for each request. It can contain literal
64 characters copied into the log files and the c-type control
65 characters "\n" and "\t" to represent new-lines and tabs.
66 Literal quotes and back-slashes should be escaped with
69 <p>The characteristics of the request itself are logged by
70 placing "<code>%</code>" directives in the format string, which are
71 replaced in the log file by the values as follows:</p>
73 <table class="bordered"><tr class="header"><th>Format String</th>
74 <th>Description</th></tr>
75 <tr><td><code>%%</code></td>
76 <td>The percent sign</td></tr>
77 <tr class="odd"><td><code>%...a</code></td>
78 <td>Remote IP-address</td></tr>
79 <tr><td><code>%...A</code></td>
80 <td>Local IP-address</td></tr>
81 <tr class="odd"><td><code>%...B</code></td>
82 <td>Bytes sent, excluding HTTP headers.</td></tr>
83 <tr><td><code>%...b</code></td>
84 <td>Bytes sent, excluding HTTP headers. In CLF format, <em>i.e.</em>
85 a '<code>-</code>' rather than a 0 when no bytes are sent.</td></tr>
86 <tr class="odd"><td><code>%...{<var>Foobar</var>}C</code></td>
87 <td>The contents of cookie <var>Foobar</var> in the request sent
88 to the server.</td></tr>
89 <tr><td><code>%...D</code></td>
90 <td>The time taken to serve the request, in microseconds.</td></tr>
91 <tr class="odd"><td><code>%...{<var>FOOBAR</var>}e</code></td>
92 <td>The contents of the environment variable
93 <var>FOOBAR</var></td></tr>
94 <tr><td><code>%...f</code></td>
95 <td>Filename</td></tr>
96 <tr class="odd"><td><code>%...h</code></td>
97 <td>Remote host</td></tr>
98 <tr><td><code>%...H</code></td>
99 <td>The request protocol</td></tr>
100 <tr class="odd"><td><code>%...{<var>Foobar</var>}i</code></td>
101 <td>The contents of <code><var>Foobar</var>:</code> header line(s)
102 in the request sent to the server.</td></tr>
103 <tr><td><code>%...l</code></td>
104 <td>Remote logname (from identd, if supplied)</td></tr>
105 <tr class="odd"><td><code>%...m</code></td>
106 <td>The request method</td></tr>
107 <tr><td><code>%...{<var>Foobar</var>}n</code></td>
108 <td>The contents of note <var>Foobar</var> from another
110 <tr class="odd"><td><code>%...{<var>Foobar</var>}o</code></td>
111 <td>The contents of <code><var>Foobar</var>:</code> header line(s)
112 in the reply.</td></tr>
113 <tr><td><code>%...p</code></td>
114 <td>The canonical port of the server serving the request</td></tr>
115 <tr class="odd"><td><code>%...P</code></td>
116 <td>The process ID of the child that serviced the request.</td></tr>
117 <tr><td><code>%...q</code></td>
118 <td>The query string (prepended with a <code>?</code> if a query
119 string exists, otherwise an empty string)</td></tr>
120 <tr class="odd"><td><code>%...r</code></td>
121 <td>First line of request</td></tr>
122 <tr><td><code>%...s</code></td>
123 <td>Status. For requests that got internally redirected, this is
124 the status of the *original* request --- <code>%...>s</code>
125 for the last.</td></tr>
126 <tr class="odd"><td><code>%...t</code></td>
127 <td>Time, in common log format time format (standard english
129 <tr><td><code>%...{<var>format</var>}t</code></td>
130 <td>The time, in the form given by format, which should be in
131 <code>strftime(3)</code> format. (potentially localized)</td></tr>
132 <tr class="odd"><td><code>%...T</code></td>
133 <td>The time taken to serve the request, in seconds.</td></tr>
134 <tr><td><code>%...u</code></td>
135 <td>Remote user (from auth; may be bogus if return status
136 (<code>%s</code>) is 401)</td></tr>
137 <tr class="odd"><td><code>%...U</code></td>
138 <td>The URL path requested, not including any query string.</td></tr>
139 <tr><td><code>%...v</code></td>
140 <td>The canonical <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code>
141 of the server serving the request.</td></tr>
142 <tr class="odd"><td><code>%...V</code></td>
143 <td>The server name according to the <code class="directive"><a href="../mod/core.html#usecanonicalname">UseCanonicalName</a></code> setting.</td></tr>
144 <tr><td><code>%...X</code></td>
145 <td>Connection status when response is completed:
148 <tr><td><code>X</code> =</td>
149 <td>connection aborted before the response completed.</td></tr>
150 <tr><td><code>+</code> =</td>
151 <td>connection may be kept alive after the response is
153 <tr><td><code>-</code> = </td>
154 <td>connection will be closed after the response is
158 <p>(This directive was <code>%...c</code> in late versions of Apache
159 1.3, but this conflicted with the historical ssl
160 <code>%...{<var>var</var>}c</code> syntax.)</p></td></tr>
161 <tr class="odd"><td><code>%...I</code></td>
162 <td>Bytes received, including request and headers, cannot be zero.
163 You need to enable <code class="module"><a href="../mod/mod_logio.html">mod_logio</a></code> to use this.</td></tr>
164 <tr><td><code>%...O</code></td>
165 <td>Bytes sent, including headers, cannot be zero. You need to
166 enable <code class="module"><a href="../mod/mod_logio.html">mod_logio</a></code> to use this.</td></tr>
169 <p>The "<var>...</var>" can be nothing at all (<em>e.g.</em>,
170 <code>"%h %u %r %s %b"</code>), or it can indicate conditions for
171 inclusion of the item (which will cause it to be replaced with "-" if
172 the condition is not met). The forms of condition are a list of
173 HTTP status codes, which may or may not be preceded by "!".
174 Thus, "%400,501{User-agent}i" logs <code>User-agent:</code> on 400
175 errors and 501 errors (Bad Request, Not Implemented) only;
176 "%!200,304,302{Referer}i" logs <code>Referer:</code> on all requests
177 which did <em>not</em> return some sort of normal status.</p>
179 <p>Note that there is no escaping performed on the strings from
180 <code>%...r</code>, <code>%...i</code> and <code>%...o</code>. This
181 is mainly to comply with the requirements of the Common Log Format.
182 This implies that clients can insert control characters into the log,
183 so care should be taken when dealing with raw log files.</p>
185 <p>Some commonly used log format strings are:</p>
188 <dt>Common Log Format (CLF)</dt>
189 <dd><code>"%h %l %u %t \"%r\" %>s %b"</code></dd>
191 <dt>Common Log Format with Virtual Host</dt>
192 <dd><code>"%v %h %l %u %t \"%r\" %>s %b"</code></dd>
194 <dt>NCSA extended/combined log format</dt>
195 <dd><code>"%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
196 \"%{User-agent}i\""</code></dd>
198 <dt>Referer log format</dt>
199 <dd><code>"%{Referer}i -> %U"</code></dd>
201 <dt>Agent (Browser) log format</dt>
202 <dd><code>"%{User-agent}i"</code></dd>
205 <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
206 request are used for <code>%v</code> and <code>%p</code>
207 respectively. This happens regardless of the <code class="directive"><a href="../mod/core.html#usecanonicalname">UseCanonicalName</a></code> setting
208 because otherwise log analysis programs would have to duplicate
209 the entire vhost matching algorithm in order to decide what
210 host really served the request.</p>
211 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
212 <div class="section">
213 <h2><a name="security" id="security">Security Considerations</a></h2>
214 <p>See the <a href="../misc/security_tips.html#serverroot">security tips</a>
215 document for details on why your security could be compromised
216 if the directory where logfiles are stored is writable by
217 anyone other than the user that starts the server.</p>
219 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
220 <div class="directive-section"><h2><a name="CookieLog" id="CookieLog">CookieLog</a> <a name="cookielog" id="cookielog">Directive</a></h2>
221 <table class="directive">
222 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets filename for the logging of cookies</td></tr>
223 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CookieLog <var>filename</var></code></td></tr>
224 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
225 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
226 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
227 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>This directive is deprecated.</td></tr>
229 <p>The <code class="directive">CookieLog</code> directive sets the
230 filename for logging of cookies. The filename is relative to the
231 <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>. This directive is
232 included only for compatibility with <code>mod_cookies</code>,
233 and is deprecated.</p>
236 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
237 <div class="directive-section"><h2><a name="CustomLog" id="CustomLog">CustomLog</a> <a name="customlog" id="customlog">Directive</a></h2>
238 <table class="directive">
239 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets filename and format of log file</td></tr>
240 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CustomLog <var>file</var>|<var>pipe</var>
241 <var>format</var>|<var>nickname</var>
242 [env=[!]<var>environment-variable</var>]</code></td></tr>
243 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
244 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
245 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
247 <p>The <code class="directive">CustomLog</code> directive is used to
248 log requests to the server. A log format is specified, and the
249 logging can optionally be made conditional on request
250 characteristics using environment variables.</p>
252 <p>The first argument, which specifies the location to which
253 the logs will be written, can take on one of the following two
257 <dt><var>file</var></dt>
258 <dd>A filename, relative to the <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</dd>
260 <dt><var>pipe</var></dt>
261 <dd>The pipe character "<code>|</code>", followed by the path
262 to a program to receive the log information on its standard
265 <div class="warning"><h3>Security:</h3>
266 <p>If a program is used, then it will be run under the user who
267 started httpd. This will be root if the server was started by root;
268 be sure that the program is secure.</p>
272 <p>The second argument specifies what will be written to the
273 log file. It can specify either a <var>nickname</var> defined by
274 a previous <code class="directive"><a href="#logformat">LogFormat</a></code>
275 directive, or it can be an explicit <var>format</var> string as
276 described in the <a href="#formats">log formats</a> section.</p>
278 <p>For example, the following two sets of directives have
279 exactly the same effect:</p>
281 <div class="example"><p><code>
282 # CustomLog with format nickname<br />
283 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
284 CustomLog logs/access_log common<br />
286 # CustomLog with explicit format string<br />
287 CustomLog logs/access_log "%h %l %u %t \"%r\" %>s %b"
290 <p>The third argument is optional and allows the decision on
291 whether or not to log a particular request to be based on the
292 presence or absence of a particular variable in the server
293 environment. If the specified <a href="../env.html">environment
294 variable</a> is set for the request (or is not set, in the case
295 of a '<code>env=!<var>name</var></code>' clause), then the
296 request will be logged.</p>
298 <p>Environment variables can be set on a per-request
299 basis using the <code class="module"><a href="../mod/mod_setenvif.html">mod_setenvif</a></code>
300 and/or <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> modules. For
301 example, if you want to record requests for all GIF
302 images on your server in a separate logfile but not in your main
303 log, you can use:</p>
305 <div class="example"><p><code>
306 SetEnvIf Request_URI \.gif$ gif-image<br />
307 CustomLog gif-requests.log common env=gif-image<br />
308 CustomLog nongif-requests.log common env=!gif-image
312 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
313 <div class="directive-section"><h2><a name="LogFormat" id="LogFormat">LogFormat</a> <a name="logformat" id="logformat">Directive</a></h2>
314 <table class="directive">
315 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Describes a format for use in a log file</td></tr>
316 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LogFormat <var>format</var>|<var>nickname</var>
317 [<var>nickname</var>]</code></td></tr>
318 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LogFormat "%h %l %u %t \"%r\" %>s %b"</code></td></tr>
319 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
320 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
321 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
323 <p>This directive specifies the format of the access log
326 <p>The <code class="directive">LogFormat</code> directive can take one of two
327 forms. In the first form, where only one argument is specified,
328 this directive sets the log format which will be used by logs
329 specified in subsequent <code class="directive">TransferLog</code>
330 directives. The single argument can specify an explicit
331 <var>format</var> as discussed in <a href="#formats">custom log
332 formats</a> section above. Alternatively, it can use a
333 <var>nickname</var> to refer to a log format defined in a
334 previous <code class="directive">LogFormat</code> directive as described
337 <p>The second form of the <code class="directive">LogFormat</code>
338 directive associates an explicit <var>format</var> with a
339 <var>nickname</var>. This <var>nickname</var> can then be used in
340 subsequent <code class="directive">LogFormat</code> or
341 <code class="directive"><a href="#customlog">CustomLog</a></code> directives
342 rather than repeating the entire format string. A
343 <code class="directive">LogFormat</code> directive that defines a nickname
344 <strong>does nothing else</strong> -- that is, it <em>only</em>
345 defines the nickname, it doesn't actually apply the format and make
346 it the default. Therefore, it will not affect subsequent
347 <code class="directive"><a href="#transferlog">TransferLog</a></code> directives.
348 In addition, <code class="directive">LogFormat</code> cannot use one nickname
349 to define another nickname. Note, that the nickname should not contain
350 percent signs (<code>%</code>).</p>
352 <div class="example"><h3>Example</h3><p><code>
353 LogFormat "%v %h %l %u %t \"%r\" %>s %b" vhost_common
357 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
358 <div class="directive-section"><h2><a name="TransferLog" id="TransferLog">TransferLog</a> <a name="transferlog" id="transferlog">Directive</a></h2>
359 <table class="directive">
360 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specifly location of a log file</td></tr>
361 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>TransferLog <var>file</var>|<var>pipe</var></code></td></tr>
362 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
363 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
364 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_config</td></tr>
366 <p>This directive has exactly the same arguments and effect as
367 the <code class="directive"><a href="#customlog">CustomLog</a></code>
368 directive, with the exception that it does not allow the log format
369 to be specified explicitly or for conditional logging of requests.
370 Instead, the log format is determined by the most recently specified
371 <code class="directive"><a href="#logformat">LogFormat</a></code> directive
372 (which does not define a nickname). Common Log Format is used if no
373 other format has been specified.</p>
375 <div class="example"><h3>Example</h3><p><code>
376 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\""<br />
377 TransferLog logs/access_log
383 <p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p>
384 <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></div>