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15 <p class="apache">Apache HTTP Server Version 2.3</p>
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19 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.3</a></div><div id="page-content"><div id="preamble"><h1>Log Files</h1>
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28 <p>In order to effectively manage a web server, it is necessary
29 to get feedback about the activity and performance of the
30 server as well as any problems that may be occurring. The Apache HTTP Server
31 provides very comprehensive and flexible logging
32 capabilities. This document describes how to configure its
33 logging capabilities, and how to understand what the logs
36 <div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#overview">Overview</a></li>
37 <li><img alt="" src="./images/down.gif" /> <a href="#security">Security Warning</a></li>
38 <li><img alt="" src="./images/down.gif" /> <a href="#errorlog">Error Log</a></li>
39 <li><img alt="" src="./images/down.gif" /> <a href="#accesslog">Access Log</a></li>
40 <li><img alt="" src="./images/down.gif" /> <a href="#rotation">Log Rotation</a></li>
41 <li><img alt="" src="./images/down.gif" /> <a href="#piped">Piped Logs</a></li>
42 <li><img alt="" src="./images/down.gif" /> <a href="#virtualhost">Virtual Hosts</a></li>
43 <li><img alt="" src="./images/down.gif" /> <a href="#other">Other Log Files</a></li>
45 <div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
47 <h2><a name="overview" id="overview">Overview</a></h2>
50 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_log_forensic.html">mod_log_forensic</a></code></li><li><code class="module"><a href="./mod/mod_logio.html">mod_logio</a></code></li><li><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></li><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li></ul></td><td /></tr></table>
53 The Apache HTTP Server provides a variety of different mechanisms for
54 logging everything that happens on your server, from the initial
55 request, through the URL mapping process, to the final resolution of
56 the connection, including any errors that may have occurred in the
57 process. In addition to this, third-party modules may provide logging
58 capabilities, or inject entries into the existing log files, and
59 applications such as CGI programs, or PHP scripts, or other handlers,
60 may send messages to the server error log.
64 In this document we discuss the logging modules that are a standard
65 part of the http server.
68 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
70 <h2><a name="security" id="security">Security Warning</a></h2>
73 <p>Anyone who can write to the directory where Apache httpd is
74 writing a log file can almost certainly gain access to the uid
75 that the server is started as, which is normally root. Do
76 <em>NOT</em> give people write access to the directory the logs
77 are stored in without being aware of the consequences; see the
78 <a href="misc/security_tips.html">security tips</a> document
81 <p>In addition, log files may contain information supplied
82 directly by the client, without escaping. Therefore, it is
83 possible for malicious clients to insert control-characters in
84 the log files, so care must be taken in dealing with raw
86 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
88 <h2><a name="errorlog" id="errorlog">Error Log</a></h2>
91 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/core.html">core</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code></li><li><code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code></li></ul></td></tr></table>
93 <p>The server error log, whose name and location is set by the
94 <code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code> directive, is the
95 most important log file. This is the place where Apache httpd
96 will send diagnostic information and record any errors that it
97 encounters in processing requests. It is the first place to
98 look when a problem occurs with starting the server or with the
99 operation of the server, since it will often contain details of
100 what went wrong and how to fix it.</p>
102 <p>The error log is usually written to a file (typically
103 <code>error_log</code> on Unix systems and
104 <code>error.log</code> on Windows and OS/2). On Unix systems it
105 is also possible to have the server send errors to
106 <code>syslog</code> or <a href="#piped">pipe them to a
109 <p>The format of the error log is relatively free-form and
110 descriptive. But there is certain information that is contained
111 in most error log entries. For example, here is a typical
114 <div class="example"><p><code>
115 [Wed Oct 11 14:32:52 2000] [error] [client 127.0.0.1]
116 client denied by server configuration:
117 /export/home/live/ap/htdocs/test
120 <p>The first item in the log entry is the date and time of the
121 message. The second item lists the severity of the error being
122 reported. The <code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code>
123 directive is used to control the types of errors that are sent
124 to the error log by restricting the severity level. The third
125 item gives the IP address of the client that generated the
126 error. Beyond that is the message itself, which in this case
127 indicates that the server has been configured to deny the
128 client access. The server reports the file-system path (as
129 opposed to the web path) of the requested document.</p>
131 <p>A very wide variety of different messages can appear in the
132 error log. Most look similar to the example above. The error
133 log will also contain debugging output from CGI scripts. Any
134 information written to <code>stderr</code> by a CGI script will
135 be copied directly to the error log.</p>
137 <p>It is not possible to customize the error log by adding or
138 removing information. However, error log entries dealing with
139 particular requests have corresponding entries in the <a href="#accesslog">access log</a>. For example, the above example
140 entry corresponds to an access log entry with status code 403.
141 Since it is possible to customize the access log, you can
142 obtain more information about error conditions using that log
145 <p>During testing, it is often useful to continuously monitor
146 the error log for any problems. On Unix systems, you can
147 accomplish this using:</p>
149 <div class="example"><p><code>
152 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
153 <div class="section">
154 <h2><a name="accesslog" id="accesslog">Access Log</a></h2>
157 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_setenvif.html">mod_setenvif</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code></li></ul></td></tr></table>
159 <p>The server access log records all requests processed by the
160 server. The location and content of the access log are
161 controlled by the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
162 directive. The <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code>
163 directive can be used to simplify the selection of
164 the contents of the logs. This section describes how to configure the server
165 to record information in the access log.</p>
167 <p>Of course, storing the information in the access log is only
168 the start of log management. The next step is to analyze this
169 information to produce useful statistics. Log analysis in
170 general is beyond the scope of this document, and not really
171 part of the job of the web server itself. For more information
172 about this topic, and for applications which perform log
173 analysis, check the <a href="http://dmoz.org/Computers/Software/Internet/Site_Management/Log_analysis/">
174 Open Directory</a> or <a href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Log_Analysis_Tools/">
177 <p>Various versions of Apache httpd have used other modules and
178 directives to control access logging, including
179 mod_log_referer, mod_log_agent, and the
180 <code>TransferLog</code> directive. The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive now subsumes
181 the functionality of all the older directives.</p>
183 <p>The format of the access log is highly configurable. The format
184 is specified using a format string that looks much like a C-style
185 printf(1) format string. Some examples are presented in the next
186 sections. For a complete list of the possible contents of the
187 format string, see the <code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code> <a href="mod/mod_log_config.html#formats">format strings</a>.</p>
189 <h3><a name="common" id="common">Common Log Format</a></h3>
192 <p>A typical configuration for the access log might look as
195 <div class="example"><p><code>
196 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
197 CustomLog logs/access_log common
200 <p>This defines the <em>nickname</em> <code>common</code> and
201 associates it with a particular log format string. The format
202 string consists of percent directives, each of which tell the
203 server to log a particular piece of information. Literal
204 characters may also be placed in the format string and will be
205 copied directly into the log output. The quote character
206 (<code>"</code>) must be escaped by placing a back-slash before
207 it to prevent it from being interpreted as the end of the
208 format string. The format string may also contain the special
209 control characters "<code>\n</code>" for new-line and
210 "<code>\t</code>" for tab.</p>
212 <p>The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
213 directive sets up a new log file using the defined
214 <em>nickname</em>. The filename for the access log is relative to
215 the <code class="directive"><a href="./mod/core.html#serverroot">ServerRoot</a></code> unless it
216 begins with a slash.</p>
218 <p>The above configuration will write log entries in a format
219 known as the Common Log Format (CLF). This standard format can
220 be produced by many different web servers and read by many log
221 analysis programs. The log file entries produced in CLF will
222 look something like this:</p>
224 <div class="example"><p><code>
225 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
226 /apache_pb.gif HTTP/1.0" 200 2326
229 <p>Each part of this log entry is described below.</p>
232 <dt><code>127.0.0.1</code> (<code>%h</code>)</dt>
234 <dd>This is the IP address of the client (remote host) which
235 made the request to the server. If <code class="directive"><a href="./mod/core.html#hostnamelookups">HostnameLookups</a></code> is
236 set to <code>On</code>, then the server will try to determine
237 the hostname and log it in place of the IP address. However,
238 this configuration is not recommended since it can
239 significantly slow the server. Instead, it is best to use a
240 log post-processor such as <code class="program"><a href="./programs/logresolve.html">logresolve</a></code> to determine
241 the hostnames. The IP address reported here is not
242 necessarily the address of the machine at which the user is
243 sitting. If a proxy server exists between the user and the
244 server, this address will be the address of the proxy, rather
245 than the originating machine.</dd>
247 <dt><code>-</code> (<code>%l</code>)</dt>
249 <dd>The "hyphen" in the output indicates that the requested
250 piece of information is not available. In this case, the
251 information that is not available is the RFC 1413 identity of
252 the client determined by <code>identd</code> on the clients
253 machine. This information is highly unreliable and should
254 almost never be used except on tightly controlled internal
255 networks. Apache httpd will not even attempt to determine
256 this information unless <code class="directive"><a href="./mod/core.html#identitycheck">IdentityCheck</a></code> is set
257 to <code>On</code>.</dd>
259 <dt><code>frank</code> (<code>%u</code>)</dt>
261 <dd>This is the userid of the person requesting the document
262 as determined by HTTP authentication. The same value is
263 typically provided to CGI scripts in the
264 <code>REMOTE_USER</code> environment variable. If the status
265 code for the request (see below) is 401, then this value
266 should not be trusted because the user is not yet
267 authenticated. If the document is not password protected,
268 this part will be "<code>-</code>" just like the previous
271 <dt><code>[10/Oct/2000:13:55:36 -0700]</code>
272 (<code>%t</code>)</dt>
275 The time that the request was received.
279 <code>[day/month/year:hour:minute:second zone]<br />
281 month = 3*letter<br />
284 minute = 2*digit<br />
285 second = 2*digit<br />
286 zone = (`+' | `-') 4*digit</code>
288 It is possible to have the time displayed in another format
289 by specifying <code>%{format}t</code> in the log format
290 string, where <code>format</code> is as in
291 <code>strftime(3)</code> from the C standard library.
294 <dt><code>"GET /apache_pb.gif HTTP/1.0"</code>
295 (<code>\"%r\"</code>)</dt>
297 <dd>The request line from the client is given in double
298 quotes. The request line contains a great deal of useful
299 information. First, the method used by the client is
300 <code>GET</code>. Second, the client requested the resource
301 <code>/apache_pb.gif</code>, and third, the client used the
302 protocol <code>HTTP/1.0</code>. It is also possible to log
303 one or more parts of the request line independently. For
304 example, the format string "<code>%m %U%q %H</code>" will log
305 the method, path, query-string, and protocol, resulting in
306 exactly the same output as "<code>%r</code>".</dd>
308 <dt><code>200</code> (<code>%>s</code>)</dt>
310 <dd>This is the status code that the server sends back to the
311 client. This information is very valuable, because it reveals
312 whether the request resulted in a successful response (codes
313 beginning in 2), a redirection (codes beginning in 3), an
314 error caused by the client (codes beginning in 4), or an
315 error in the server (codes beginning in 5). The full list of
316 possible status codes can be found in the <a href="http://www.w3.org/Protocols/rfc2616/rfc2616.txt">HTTP
317 specification</a> (RFC2616 section 10).</dd>
319 <dt><code>2326</code> (<code>%b</code>)</dt>
321 <dd>The last part indicates the size of the object returned
322 to the client, not including the response headers. If no
323 content was returned to the client, this value will be
324 "<code>-</code>". To log "<code>0</code>" for no content, use
325 <code>%B</code> instead.</dd>
329 <h3><a name="combined" id="combined">Combined Log Format</a></h3>
332 <p>Another commonly used format string is called the Combined
333 Log Format. It can be used as follows.</p>
335 <div class="example"><p><code>
336 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
337 \"%{User-agent}i\"" combined<br />
338 CustomLog log/access_log combined
341 <p>This format is exactly the same as the Common Log Format,
342 with the addition of two more fields. Each of the additional
343 fields uses the percent-directive
344 <code>%{<em>header</em>}i</code>, where <em>header</em> can be
345 any HTTP request header. The access log under this format will
348 <div class="example"><p><code>
349 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
350 /apache_pb.gif HTTP/1.0" 200 2326
351 "http://www.example.com/start.html" "Mozilla/4.08 [en]
355 <p>The additional fields are:</p>
358 <dt><code>"http://www.example.com/start.html"</code>
359 (<code>\"%{Referer}i\"</code>)</dt>
361 <dd>The "Referer" (sic) HTTP request header. This gives the
362 site that the client reports having been referred from. (This
363 should be the page that links to or includes
364 <code>/apache_pb.gif</code>).</dd>
366 <dt><code>"Mozilla/4.08 [en] (Win98; I ;Nav)"</code>
367 (<code>\"%{User-agent}i\"</code>)</dt>
369 <dd>The User-Agent HTTP request header. This is the
370 identifying information that the client browser reports about
375 <h3><a name="multiple" id="multiple">Multiple Access Logs</a></h3>
378 <p>Multiple access logs can be created simply by specifying
379 multiple <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
380 directives in the configuration
381 file. For example, the following directives will create three
382 access logs. The first contains the basic CLF information,
383 while the second and third contain referer and browser
384 information. The last two <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> lines show how
385 to mimic the effects of the <code>ReferLog</code> and <code>AgentLog</code> directives.</p>
387 <div class="example"><p><code>
388 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
389 CustomLog logs/access_log common<br />
390 CustomLog logs/referer_log "%{Referer}i -> %U"<br />
391 CustomLog logs/agent_log "%{User-agent}i"
394 <p>This example also shows that it is not necessary to define a
395 nickname with the <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> directive. Instead,
396 the log format can be specified directly in the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive.</p>
399 <h3><a name="conditional" id="conditional">Conditional Logs</a></h3>
402 <p>There are times when it is convenient to exclude certain
403 entries from the access logs based on characteristics of the
404 client request. This is easily accomplished with the help of <a href="env.html">environment variables</a>. First, an
405 environment variable must be set to indicate that the request
406 meets certain conditions. This is usually accomplished with
407 <code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>. Then the
408 <code>env=</code> clause of the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive is used to
409 include or exclude requests where the environment variable is
410 set. Some examples:</p>
412 <div class="example"><p><code>
413 # Mark requests from the loop-back interface<br />
414 SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog<br />
415 # Mark requests for the robots.txt file<br />
416 SetEnvIf Request_URI "^/robots\.txt$" dontlog<br />
417 # Log what remains<br />
418 CustomLog logs/access_log common env=!dontlog
421 <p>As another example, consider logging requests from
422 english-speakers to one log file, and non-english speakers to a
423 different log file.</p>
425 <div class="example"><p><code>
426 SetEnvIf Accept-Language "en" english<br />
427 CustomLog logs/english_log common env=english<br />
428 CustomLog logs/non_english_log common env=!english
431 <p>In a caching scenario one would want to know about
432 the efficiency of the cache. A very simple method to
433 find this out would be:</p>
435 <div class="example"><p><code>
436 SetEnv CACHE_MISS 1<br />
437 LogFormat "%h %l %u %t "%r " %>s %b %{CACHE_MISS}e" common-cache
438 CustomLog logs/access_log common-cache
441 <p><code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code> will run before
442 <code class="module"><a href="./mod/mod_env.html">mod_env</a></code> and when successfull will deliver the
443 content without it. In that case a cache hit will log
444 <code>-</code>, while a cache miss will log <code>1</code>.</p>
446 <p>Although we have just shown that conditional logging is very
447 powerful and flexible, it is not the only way to control the
448 contents of the logs. Log files are more useful when they
449 contain a complete record of server activity. It is often
450 easier to simply post-process the log files to remove requests
451 that you do not want to consider.</p>
453 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
454 <div class="section">
455 <h2><a name="rotation" id="rotation">Log Rotation</a></h2>
458 <p>On even a moderately busy server, the quantity of
459 information stored in the log files is very large. The access
460 log file typically grows 1 MB or more per 10,000 requests. It
461 will consequently be necessary to periodically rotate the log
462 files by moving or deleting the existing logs. This cannot be
463 done while the server is running, because Apache httpd will continue
464 writing to the old log file as long as it holds the file open.
465 Instead, the server must be <a href="stopping.html">restarted</a> after the log files are
466 moved or deleted so that it will open new log files.</p>
468 <p>By using a <em>graceful</em> restart, the server can be
469 instructed to open new log files without losing any existing or
470 pending connections from clients. However, in order to
471 accomplish this, the server must continue to write to the old
472 log files while it finishes serving old requests. It is
473 therefore necessary to wait for some time after the restart
474 before doing any processing on the log files. A typical
475 scenario that simply rotates the logs and compresses the old
476 logs to save space is:</p>
478 <div class="example"><p><code>
479 mv access_log access_log.old<br />
480 mv error_log error_log.old<br />
481 apachectl graceful<br />
483 gzip access_log.old error_log.old
486 <p>Another way to perform log rotation is using <a href="#piped">piped logs</a> as discussed in the next
488 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
489 <div class="section">
490 <h2><a name="piped" id="piped">Piped Logs</a></h2>
493 <p>Apache httpd is capable of writing error and access log
494 files through a pipe to another process, rather than directly
495 to a file. This capability dramatically increases the
496 flexibility of logging, without adding code to the main server.
497 In order to write logs to a pipe, simply replace the filename
498 with the pipe character "<code>|</code>", followed by the name
499 of the executable which should accept log entries on its
500 standard input. The server will start the piped-log process when
501 the server starts, and will restart it if it crashes while the
502 server is running. (This last feature is why we can refer to
503 this technique as "reliable piped logging".)</p>
505 <p>Piped log processes are spawned by the parent Apache httpd
506 process, and inherit the userid of that process. This means
507 that piped log programs usually run as root. It is therefore
508 very important to keep the programs simple and secure.</p>
510 <p>One important use of piped logs is to allow log rotation
511 without having to restart the server. The Apache HTTP Server
512 includes a simple program called <code class="program"><a href="./programs/rotatelogs.html">rotatelogs</a></code>
513 for this purpose. For example, to rotate the logs every 24 hours, you
516 <div class="example"><p><code>
517 CustomLog "|/usr/local/apache/bin/rotatelogs
518 /var/log/access_log 86400" common
521 <p>Notice that quotes are used to enclose the entire command
522 that will be called for the pipe. Although these examples are
523 for the access log, the same technique can be used for the
526 <p>A similar but much more flexible log rotation program
527 called <a href="http://www.cronolog.org/">cronolog</a>
528 is available at an external site.</p>
530 <p>As with conditional logging, piped logs are a very powerful
531 tool, but they should not be used where a simpler solution like
532 off-line post-processing is available.</p>
533 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
534 <div class="section">
535 <h2><a name="virtualhost" id="virtualhost">Virtual Hosts</a></h2>
538 <p>When running a server with many <a href="vhosts/">virtual
539 hosts</a>, there are several options for dealing with log
540 files. First, it is possible to use logs exactly as in a
541 single-host server. Simply by placing the logging directives
542 outside the <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code> sections in the
543 main server context, it is possible to log all requests in the
544 same access log and error log. This technique does not allow
545 for easy collection of statistics on individual virtual
548 <p>If <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
549 or <code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code>
550 directives are placed inside a
551 <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code>
552 section, all requests or errors for that virtual host will be
553 logged only to the specified file. Any virtual host which does
554 not have logging directives will still have its requests sent
555 to the main server logs. This technique is very useful for a
556 small number of virtual hosts, but if the number of hosts is
557 very large, it can be complicated to manage. In addition, it
558 can often create problems with <a href="vhosts/fd-limits.html">insufficient file
561 <p>For the access log, there is a very good compromise. By
562 adding information on the virtual host to the log format
563 string, it is possible to log all hosts to the same log, and
564 later split the log into individual files. For example,
565 consider the following directives.</p>
567 <div class="example"><p><code>
568 LogFormat "%v %l %u %t \"%r\" %>s %b"
570 CustomLog logs/access_log comonvhost
573 <p>The <code>%v</code> is used to log the name of the virtual
574 host that is serving the request. Then a program like <a href="programs/other.html">split-logfile</a> can be used to
575 post-process the access log in order to split it into one file
576 per virtual host.</p>
577 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
578 <div class="section">
579 <h2><a name="other" id="other">Other Log Files</a></h2>
582 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_logio.html">mod_logio</a></code></li><li><code class="module"><a href="./mod/mod_log_forensic.html">mod_log_forensic</a></code></li><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li><li><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="./mod/mod_log_forensic.html#forensiclog">ForensicLog</a></code></li><li><code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewritelog">RewriteLog</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewriteloglevel">RewriteLogLevel</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlogbuffer">ScriptLogBuffer</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptloglength">ScriptLogLength</a></code></li></ul></td></tr></table>
584 <h3>Logging actual bytes sent and received</h3>
587 <p><code class="module"><a href="./mod/mod_logio.html">mod_logio</a></code> adds in two additional
588 <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> fields
589 (%I and %O) that log the actual number of bytes received and sent
593 <h3>Forensic Logging</h3>
596 <p><code class="module"><a href="./mod/mod_log_forensic.html">mod_log_forensic</a></code> provides for forensic logging of
597 client requests. Logging is done before and after processing a
598 request, so the forensic log contains two log lines for each
599 request. The forensic logger is very strict with no customizations.
600 It can be an invaluable debugging and security tool.</p>
603 <h3><a name="pidfile" id="pidfile">PID File</a></h3>
606 <p>On startup, Apache httpd saves the process id of the parent
607 httpd process to the file <code>logs/httpd.pid</code>. This
608 filename can be changed with the <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> directive. The
609 process-id is for use by the administrator in restarting and
610 terminating the daemon by sending signals to the parent
611 process; on Windows, use the -k command line option instead.
612 For more information see the <a href="stopping.html">Stopping
613 and Restarting</a> page.</p>
616 <h3><a name="scriptlog" id="scriptlog">Script Log</a></h3>
619 <p>In order to aid in debugging, the
620 <code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code> directive
621 allows you to record the input to and output from CGI scripts.
622 This should only be used in testing - not for live servers.
623 More information is available in the <a href="mod/mod_cgi.html">mod_cgi</a> documentation.</p>
626 <h3><a name="rewritelog" id="rewritelog">Rewrite Log</a></h3>
629 <p>When using the powerful and complex features of <a href="mod/mod_rewrite.html">mod_rewrite</a>, it is almost
630 always necessary to use the <code class="directive"><a href="./mod/mod_rewrite.html#rewritelog">RewriteLog</a></code> to help
631 in debugging. This log file produces a detailed analysis of how
632 the rewriting engine transforms requests. The level of detail
633 is controlled by the <code class="directive"><a href="./mod/mod_rewrite.html#rewriteloglevel">RewriteLogLevel</a></code> directive.</p>
636 <div class="bottomlang">
637 <p><span>Available Languages: </span><a href="./en/logs.html" title="English"> en </a> |
638 <a href="./fr/logs.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
639 <a href="./ja/logs.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
640 <a href="./ko/logs.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> |
641 <a href="./tr/logs.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
642 </div><div id="footer">
643 <p class="apache">Copyright 2010 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
644 <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>
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