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5 --><title>Log Files - Apache HTTP Server</title><link href="./style/manual.css" type="text/css" rel="stylesheet"/></head><body><blockquote><div align="center"><img src="./images/sub.gif" alt="[APACHE DOCUMENTATION]"/><h3>Apache HTTP Server Version 2.0</h3></div><h1 align="center">Log Files</h1>
6 <p>In order to effectively manage a web server, it is necessary
7 to get feedback about the activity and performance of the
8 server as well as any problems that may be occuring. The Apache
9 HTTP Server provides very comprehensive and flexible logging
10 capabilities. This document describes how to configure its
11 logging capabilities, and how to understand what the logs
13 <ul><li><a href="#security">Security Warning</a></li><li><a href="#errorlog">Error Log</a></li><li><a href="#accesslog">Access Log</a><ul><li><a href="#common">Common Log Format</a></li><li><a href="#combined">Combined Log Format</a></li><li><a href="#multiple">Multiple Access Logs</a></li><li><a href="#conditional">Conditional Logs</a></li></ul></li><li><a href="#rotation">Rotation Logs</a></li><li><a href="#piped">Piped Logs</a></li><li><a href="#virtualhost">Virtual Hosts</a></li><li><a href="#other">Other Log Files</a><ul><li><a href="#pidfile">PID File</a></li><li><a href="#scriptlog">Script Log</a></li><li><a href="#rewritelog">Rewrite Log</a></li></ul></li></ul><hr/><h2><a name="security">Security Warning</a></h2>
16 <p>Anyone who can write to the directory where Apache is
17 writing a log file can almost certainly gain access to the uid
18 that the server is started as, which is normally root. Do
19 <em>NOT</em> give people write access to the directory the logs
20 are stored in without being aware of the consequences; see the
21 <a href="misc/security_tips.html">security tips</a> document
24 <p>In addition, log files may contain information supplied
25 directly by the client, without escaping. Therefore, it is
26 possible for malicious clients to insert control-characters in
27 the log files, so care must be taken in dealing with raw
29 <h2><a name="errorlog">Error Log</a></h2>
32 <table border="1"><tr><td valign="top"><strong>Related Modules</strong><br/><br/></td><td valign="top"><strong>Related Directives</strong><br/><br/><a href="./mod/mod_core.html#errorlog" class="directive"><code class="directive">ErrorLog</code></a><br/><a href="./mod/mod_core.html#loglevel" class="directive"><code class="directive">LogLevel</code></a><br/></td></tr></table>
34 <p>The server error log, whose name and location is set by the
35 <a href="./mod/core.html#errorlog" class="directive"><code class="directive">ErrorLog</code></a> directive, is the
36 most important log file. This is the place where Apache httpd
37 will send diagnostic information and record any errors that it
38 encounters in processing requests. It is the first place to
39 look when a problem occurs with starting the server or with the
40 operation of the server, since it will often contain details of
41 what went wrong and how to fix it.</p>
43 <p>The error log is usually written to a file (typically
44 <code>error_log</code> on unix systems and
45 <code>error.log</code> on Windows and OS/2). On unix systems it
46 is also possible to have the server send errors to
47 <code>syslog</code> or <a href="#piped">pipe them to a
50 <p>The format of the error log is relatively free-form and
51 descriptive. But there is certain information that is contained
52 in most error log entries. For example, here is a typical
55 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
56 [Wed Oct 11 14:32:52 2000] [error] [client 127.0.0.1]
57 client denied by server configuration:
58 /export/home/live/ap/htdocs/test
59 </code></td></tr></table></blockquote>
61 <p>The first item in the log entry is the date and time of the
62 message. The second entry lists the severity of the error being
63 reported. The <a href="./mod/core.html#loglevel" class="directive"><code class="directive">LogLevel</code></a>
64 directive is used to control the types of errors that are sent
65 to the error log by restricting the severity level. The third
66 entry gives the IP address of the client that generated the
67 error. Beyond that is the message itself, which in this case
68 indicates that the server has been configured to deny the
69 client access. The server reports the file-system path (as
70 opposed to the web path) of the requested document.</p>
72 <p>A very wide variety of different messages can appear in the
73 error log. Most look similar to the example above. The error
74 log will also contain debugging output from CGI scripts. Any
75 information written to <code>stderr</code> by a CGI script will
76 be copied directly to the error log.</p>
78 <p>It is not possible to customize the error log by adding or
79 removing information. However, error log entries dealing with
80 particular requests have corresponding entries in the <a href="#accesslog">access log</a>. For example, the above example
81 entry corresponds to an access log entry with status code 403.
82 Since it is possible to customize the access log, you can
83 obtain more information about error conditions using that log
86 <p>During testing, it is often useful to continuously monitor
87 the error log for any problems. On unix systems, you can
88 accomplish this using:</p>
90 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
92 </code></td></tr></table></blockquote>
93 <h2><a name="accesslog">Access Log</a></h2>
96 <table border="1"><tr><td valign="top"><strong>Related Modules</strong><br/><br/><code><a href="./mod/mod_log_config.html">mod_log_config</a></code><br/><code><a href="./mod/mod_setenvif.html">mod_setenvif</a></code><br/></td><td valign="top"><strong>Related Directives</strong><br/><br/><a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a><br/><a href="./mod/mod_log_config.html#logformat" class="directive"><code class="directive">LogFormat</code></a><br/><a href="./mod/mod_setenvif.html#setenvif" class="directive"><code class="directive">SetEnvIf</code></a><br/></td></tr></table>
98 <p>The server access log records all requests processed by the
99 server. The location and content of the access log are
100 controlled by the <a href="./mod/mod_log_config.html#
101 customlog" class="directive"><code class="directive">
102 CustomLog</code></a> directive. The <a href="./mod/mod_log_config.html#
103 logformat" class="directive"><code class="directive">
104 LogFormat</code></a> directive can be used to simplify the selection of
105 the contents of the logs. This section describes how to configure the server
106 to record information in the access log.</p>
108 <p>Of course, storing the information in the access log is only
109 the start of log management. The next step is to analyze this
110 information to produce useful statistics. Log analysis in
111 general is beyond the scope of this document, and not really
112 part of the job of the web server itself. For more information
113 about this topic, and for applications which perform log
114 analysis, check the <a href="http://dmoz.org/Computers/Software/Internet/Site_Management/Log_analysis/">
115 Open Directory</a> or <a href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Log_Analysis_Tools/">
118 <p>Various versions of Apache httpd have used other modules and
119 directives to control access logging, including
120 mod_log_referer, mod_log_agent, and the
121 <code>TransferLog</code> directive. The <code>CustomLog</code>
122 directive now subsumes the functionality of all the older
125 <p>The format of the access log is highly configurable. The
126 format is specified using a <a href="./mod/mod_log_config.html#
127 customlog" class="directive"><code class="directive">
128 CustomLog</code></a> that
129 looks much like a C-style printf(1) format string. Some
130 examples are presented in the next sections. For a complete
131 list of the possible contents of the format string, see the <a href="mod/mod_log_config.html">mod_log_config
132 documentation</a>.</p>
134 <h3><a name="common">Common Log Format</a></h3>
137 <p>A typical configuration for the access log might look as
140 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
141 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br>
142 CustomLog logs/access_log common
143 </code></td></tr></table></blockquote>
145 <p>This defines the <em>nickname</em> <code>common</code> and
146 associates it with a particular log format string. The format
147 string consists of percent directives, each of which tell the
148 server to log a particular piece of information. Literal
149 characters may also be placed in the format string and will be
150 copied directly into the log output. The quote character
151 (<code>"</code>) must be escaped by placing a back-slash before
152 it to prevent it from being interpreted as the end of the
153 format string. The format string may also contain the special
154 control characters "<code>\n</code>" for new-line and
155 "<code>\t</code>" for tab.</p>
157 <p>The <code>CustomLog</code> directive sets up a new log file
158 using the defined <em>nickname</em>. The filename for the
159 access log is relative to the <a href="./mod/core.html#
160 serverroot" class="directive"><code class="directive">
161 ServerRoot</code></a> unless it begins
164 <p>The above configuration will write log entries in a format
165 known as the Common Log Format (CLF). This standard format can
166 be produced by many different web servers and read by many log
167 analysis programs. The log file entries produced in CLF will
168 look something like this:</p>
170 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
171 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
172 /apache_pb.gif HTTP/1.0" 200 2326
173 </code></td></tr></table></blockquote>
175 <p>Each part of this log entry is described below.</p>
178 <dt><code>127.0.0.1</code> (<code>%h</code>)</dt>
180 <dd>This is the IP address of the client (remote host) which
181 made the request to the server. If <a href="./mod/core.html#
182 hostnamelookups" class="directive"><code class="directive">
183 HostnameLookups</code></a> is
184 set to <code>On</code>, then the server will try to determine
185 the hostname and log it in place of the IP address. However,
186 this configuration is not recommended since it can
187 significantly slow the server. Instead, it is best to use a
188 log post-processor such as <a href="programs/logresolve.html">logresolve</a> to determine
189 the hostnames. The IP address reported here is not
190 necessarily the address of the machine at which the user is
191 sitting. If a proxy server exists between the user and the
192 server, this address will be the address of the proxy, rather
193 than the originating machine.</dd>
195 <dt><code>-</code> (<code>%l</code>)</dt>
197 <dd>The "hyphen" in the output indicates that the requested
198 piece of information is not available. In this case, the
199 information that is not available is the RFC 1413 identity of
200 the client determined by <code>identd</code> on the clients
201 machine. This information is highly unreliable and should
202 almost never be used except on tightly controlled internal
203 networks. Apache httpd will not even attempt to determine
204 this information unless <a href="./mod/core.html#
205 identitycheck" class="directive"><code class="directive">
206 IdentityCheck</code></a> is set
207 to <code>On</code>.</dd>
209 <dt><code>frank</code> (<code>%u</code>)</dt>
211 <dd>This is the userid of the person requesting the document
212 as determined by HTTP authentication. The same value is
213 typically provided to CGI scripts in the
214 <code>REMOTE_USER</code> environment variable. If the status
215 code for the request (see below) is 401, then this value
216 should not be trusted because the user is not yet
217 authenticated. If the document is not password protected,
218 this entry will be "<code>-</code>" just like the previous
221 <dt><code>[10/Oct/2000:13:55:36 -0700]</code>
222 (<code>%t</code>)</dt>
225 The time that the server finished processing the request.
229 <code>[day/month/year:hour:minute:second zone]<br>
236 zone = (`+' | `-') 4*digit</code>
238 It is possible to have the time displayed in another format
239 by specifying <code>%{format}t</code> in the log format
240 string, where <code>format</code> is as in
241 <code>strftime(3)</code> from the C standard library.
244 <dt><code>"GET /apache_pb.gif HTTP/1.0"</code>
245 (<code>\"%r\"</code>)</dt>
247 <dd>The request line from the client is given in double
248 quotes. The request line contains a great deal of useful
249 information. First, the method used by the client is
250 <code>GET</code>. Second, the client requested the resource
251 <code>/apache_pb.gif</code>, and third, the client used the
252 protocol <code>HTTP/1.0</code>. It is also possible to log
253 one or more parts of the request line independently. For
254 example, the format string "<code>%m %U%q %H</code>" will log
255 the method, path, query-string, and protocol, resulting in
256 exactly the same output as "<code>%r</code>".</dd>
258 <dt><code>200</code> (<code>%>s</code>)</dt>
260 <dd>This is the status code that the server sends back to the
261 client. This information is very valuable, because it reveals
262 whether the request resulted in a successful response (codes
263 beginning in 2), a redirection (codes beginning in 3), an
264 error caused by the client (codes beginning in 4), or an
265 error in the server (codes beginning in 5). The full list of
266 possible status codes can be found in the <a href="http://www.w3.org/Protocols/rfc2616/rfc2616.txt">HTTP
267 specification</a> (RFC2616 section 10).</dd>
269 <dt><code>2326</code> (<code>%b</code>)</dt>
271 <dd>The last entry indicates the size of the object returned
272 to the client, not including the response headers. If no
273 content was returned to the client, this value will be
274 "<code>-</code>". To log "<code>0</code>" for no content, use
275 <code>%B</code> instead.</dd>
279 <h3><a name="combined">Combined Log Format</a></h3>
282 <p>Another commonly used format string is called the Combined
283 Log Format. It can be used as follows.</p>
285 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
286 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
287 \"%{User-agent}i\"" combined<br>
288 CustomLog log/acces_log combined
289 </code></td></tr></table></blockquote>
291 <p>This format is exactly the same as the Common Log Format,
292 with the addition of two more fields. Each of the additional
293 fields uses the percent-directive
294 <code>%{<em>header</em>}i</code>, where <em>header</em> can be
295 any HTTP request header. The access log under this format will
298 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
299 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
300 /apache_pb.gif HTTP/1.0" 200 2326
301 "http://www.example.com/start.html" "Mozilla/4.08 [en]
303 </code></td></tr></table></blockquote>
305 <p>The additional fields are:</p>
308 <dt><code>"http://www.example.com/start.html"</code>
309 (<code>\"%{Referer}i\"</code>)</dt>
311 <dd>The "Referer" (sic) HTTP request header. This gives the
312 site that the client reports having been referred from. (This
313 should be the page that links to or includes
314 <code>/apache_pb.gif</code>).</dd>
316 <dt><code>"Mozilla/4.08 [en] (Win98; I ;Nav)"</code>
317 (<code>\"%{User-agent}i\"</code>)</dt>
319 <dd>The User-Agent HTTP request header. This is the
320 identifying information that the client browser reports about
325 <h3><a name="multiple">Multiple Access Logs</a></h3>
328 <p>Multiple access logs can be created simply by specifying
329 multiple <a href="./mod/core.html#customlog" class="directive"><code class="directive">CustomLog</code></a>
330 directives in the configuration
331 file. For example, the following directives will create three
332 access logs. The first contains the basic CLF information,
333 while the second and third contain referer and browser
334 information. The last two <a href="./mod/core.html#
335 customlog" class="directive"><code class="directive">
336 CustomLog</code></a> lines show how
337 to mimic the effects of the <a href="./mod/core.html#referlog" class="directive"><code class="directive">ReferLog</code></a>
338 and <a href="./mod/core.html#agentlog" class="directive"><code class="directive">AgentLog</code></a> directives.</p>
340 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
341 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br>
342 CustomLog logs/access_log common<br>
343 CustomLog logs/referer_log "%{Referer}i -> %U"<br>
344 CustomLog logs/agent_log "%{User-agent}i"
345 </code></td></tr></table></blockquote>
347 <p>This example also shows that it is not necessary to define a
348 nickname with the <code>LogFormat</code> directive. Instead,
349 the log format can be specified directly in the
350 <a href="./mod/core.html#customlog" class="directive"><code class="directive">CustomLog</code></a> directive.</p>
353 <h3><a name="conditional">Conditional Logs</a></h3>
356 <p>There are times when it is convenient to exclude certain
357 entries from the access logs based on characteristics of the
358 client request. This is easily accomplished with the help of <a href="env.html">environment variables</a>. First, an
359 environment variable must be set to indicate that the request
360 meets certain conditions. This is usually accomplished with
361 <a href="./mod/mod_setenvif.html#setenvif" class="directive"><code class="directive">SetEnvIf</code></a>. Then the
362 <code>env=</code> clause of the <code>CustomLog</code>
363 directive is used to include or exclude requests where the
364 environment variable is set. Some examples:</p>
366 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
367 # Mark requests from the loop-back interface<br>
368 SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog<br>
369 # Mark requests for the robots.txt file<br>
370 SetEnvIf Request_URI "^/robots\.txt$" dontlog<br>
371 # Log what remains<br>
372 CustomLog logs/access_log common env=!dontlog
373 </code></td></tr></table></blockquote>
375 <p>As another example, consider logging requests from
376 english-speakers to one log file, and non-english speakers to a
377 different log file.</p>
379 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
380 SetEnvIf Accept-Language "en" english<br>
381 CustomLog logs/english_log common env=english<br>
382 CustomLog logs/non_english_log common env=!english
383 </code></td></tr></table></blockquote>
385 <p>Although we have just shown that conditional logging is very
386 powerful and flexibly, it is not the only way to control the
387 contents of the logs. Log files are more useful when they
388 contain a complete record of server activity. It is often
389 easier to simply post-process the log files to remove requests
390 that you do not want to consider.</p>
392 <h2><a name="rotation">Rotation Logs</a></h2>
395 <p>On even a moderately busy server, the quantity of
396 information stored in the log files is very large. The access
397 log file typically grows 1 MB or more per 10,000 requests. It
398 will consequently be necessary to periodically rotate the log
399 files by moving or deleting the existing logs. This cannot be
400 done while the server is running, because Apache will continue
401 writing to the old log file as long as it holds the file open.
402 Instead, the server must be <a href="stopping.html">restarted</a> after the log files are
403 moved or deleted so that it will open new log files.</p>
405 <p>By using a <em>graceful</em> restart, the server can be
406 instructed to open new log files without losing any existing or
407 pending connections from clients. However, in order to
408 accomplish this, the server must continue to write to the old
409 log files while it finishes serving old requests. It is
410 therefore necessary to wait for some time after the restart
411 before doing any processing on the log files. A typical
412 scenario that simply rotates the logs and compresses the old
413 logs to save space is:</p>
415 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
416 mv access_log access_log.old<br>
417 mv error_log error_log.old<br>
418 apachectl graceful<br>
420 gzip access_log.old error_log.old
421 </code></td></tr></table></blockquote>
423 <p>Another way to perform log rotation is using <a href="#piped">piped logs</a> as discussed in the next
425 <h2><a name="piped">Piped Logs</a></h2>
428 <p>Apache httpd is capable of writing error and access log
429 files through a pipe to another process, rather than directly
430 to a file. This capability dramatically increases the
431 flexibility of logging, without adding code to the main server.
432 In order to write logs to a pipe, simply replace the filename
433 with the pipe character "<code>|</code>", followed by the name
434 of the executable which should accept log entries on its
435 standard input. Apache will start the piped-log process when
436 the server starts, and will restart it if it crashes while the
437 server is running. (This last feature is why we can refer to
438 this technique as "reliable piped logging".)</p>
440 <p>Piped log processes are spawned by the parent Apache httpd
441 process, and inherit the userid of that process. This means
442 that piped log programs usually run as root. It is therefore
443 very important to keep the programs simple and secure.</p>
445 <p>Some simple examples using piped logs:</p>
447 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
448 # compressed logs<br>
449 CustomLog "|/usr/bin/gzip -c >>
450 /var/log/access_log.gz" common<br>
451 # almost-real-time name resolution<br>
452 CustomLog "|/usr/local/apache/bin/logresolve >>
453 /var/log/access_log" common
454 </code></td></tr></table></blockquote>
456 <p>Notice that quotes are used to enclose the entire command
457 that will be called for the pipe. Although these examples are
458 for the access log, the same technique can be used for the
461 <p>One important use of piped logs is to allow log rotation
462 without having to restart the server. The Apache HTTP Server
463 includes a simple program called <a href="programs/rotatelogs.html">rotatelogs</a> for this
464 purpose. For example, to rotate the logs every 24 hours, you
467 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
468 CustomLog "|/usr/local/apache/bin/rotatelogs
469 /var/log/access_log 86400" common
470 </code></td></tr></table></blockquote>
472 <p>A similar, but much more flexible log rotation program
473 called <a href="http://www.cronolog.org/">cronolog</a>
474 is available at an external site.</p>
476 <p>As with conditional logging, piped logs are a very powerful
477 tool, but they should not be used where a simpler solution like
478 off-line post-processing is available.</p>
479 <h2><a name="virtualhost">Virtual Hosts</a></h2>
482 <p>When running a server with many <a href="vhosts/">virtual
483 hosts</a>, there are several options for dealing with log
484 files. First, it is possible to use logs exactly as in a
485 single-host server. Simply by placing the logging directives
486 outside the <code><VirtualHost></code> sections in the
487 main server context, it is possible to log all requests in the
488 same access log and error log. This technique does not allow
489 for easy collection of statistics on individual virtual
492 <p>If <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a>
493 or <a href="./mod/mod_log_config.html#errorlog" class="directive"><code class="directive">ErrorLog</code></a>
494 directives are placed inside a <a href="./mod/core.html#
495 <virtualhost>" class="directive"><code class="directive">
496 <VirtualHost></code></a>
497 section, all requests or errors for that virtual host will be
498 logged only to the specified file. Any virtual host which does
499 not have logging directives will still have its requests sent
500 to the main server logs. This technique is very useful for a
501 small number of virtual hosts, but if the number of hosts is
502 very large, it can be complicated to manage. In addition, it
503 can often create problems with <a href="vhosts/fd-limits.html">insufficient file
506 <p>For the access log, there is a very good compromise. By
507 adding information on the virtual host to the log format
508 string, it is possible to log all hosts to the same log, and
509 later split the log into individual files. For example,
510 consider the following directives.</p>
512 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
513 LogFormat "%v %l %u %t \"%r\" %>s %b"
515 CustomLog logs/access_log comonvhost
516 </code></td></tr></table></blockquote>
518 <p>The <code>%v</code> is used to log the name of the virtual
519 host that is serving the request. Then a program like <a href="programs/other.html">split-logfile</a> can be used to
520 post-process the access log in order to split it into one file
521 per virtual host.</p>
522 <h2><a name="other">Other Log Files</a></h2>
525 <table border="1"><tr><td valign="top"><strong>Related Modules</strong><br/><br/><code><a href="./mod/mod_cgi.html">mod_cgi</a></code><br/><code><a href="./mod/mod_rewrite.html">mod_rewrite</a></code><br/></td><td valign="top"><strong>Related Directives</strong><br/><br/><a href="./mod/core.html#pidfile" class="directive"><code class="directive">PidFile</code></a><br/><a href="./mod/mod_rewrite.html#rewritelog" class="directive"><code class="directive">RewriteLog</code></a><br/><a href="./mod/mod_rewrite.html#rewriteloglevel" class="directive"><code class="directive">RewriteLogLevel</code></a><br/><a href="./mod/mod_cgi.html#scriptlog" class="directive"><code class="directive">ScriptLog</code></a><br/><a href="./mod/mod_cgi.html#scriptloglength" class="directive"><code class="directive">ScriptLogLength</code></a><br/><a href="./mod/mod_cgi.html#scriptbuffer" class="directive"><code class="directive">ScriptBuffer</code></a><br/></td></tr></table>
527 <h3><a name="pidfile">PID File</a></h3>
530 <p>On startup, Apache httpd saves the process id of the parent
531 httpd process to the file <code>logs/httpd.pid</code>. This
532 filename can be changed with the <a href="./mod/core.html#pidfile
533 " class="directive"><code class="directive">PidFile
534 </code></a> directive. The
535 process-id is for use by the administrator in restarting and
536 terminating the daemon by sending signals to the parent
537 process; on Windows, use the -k command line option instead.
538 For more information see the <a href="stopping.html">Stopping
539 and Restarting</a> page.</p>
542 <h3><a name="scriptlog">Script Log</a></h3>
545 <p>In order to aid in debugging, the <a href="./mod/mod_cgi.html#
546 scriptlog" class="directive"><code class="directive">
547 ScriptLog</code></a> directive
548 allows you to record the input to and output from CGI scripts.
549 This should only be used in testing - not for live servers.
550 More information is available in the <a href="mod/mod_cgi.html">mod_cgi documentation</a>.</p>
553 <h3><a name="rewritelog">Rewrite Log</a></h3>
556 <p>When using the powerful and complex features of <a href="mod/mod_rewrite.html">mod_rewrite</a>, it is almost
557 always necessary to use the <a href="./mod/mod_rewrite.html#
558 rewritelog" class="directive"><code class="directive">
559 RewriteLog</code></a> to help
560 in debugging. This log file produces a detailed analysis of how
561 the rewriting engine transforms requests. The level of detail
562 is controlled by the <a href="./mod/mod_rewrite.html#
563 rewriteloglevel" class="directive"><code class="directive">
564 RewriteLogLevel</code></a> directive.</p>
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