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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/core.html#errorlog" class="directive"><code class="directive">ErrorLog</code></a><br><a href="./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#customlog" class="directive"><code class="directive">CustomLog</code></a>
101 directive. The <a href="./mod/mod_log_config.html#logformat" class="directive"><code class="directive">LogFormat</code></a>
102 directive can be used to simplify the selection of
103 the contents of the logs. This section describes how to configure the server
104 to record information in the access log.</p>
106 <p>Of course, storing the information in the access log is only
107 the start of log management. The next step is to analyze this
108 information to produce useful statistics. Log analysis in
109 general is beyond the scope of this document, and not really
110 part of the job of the web server itself. For more information
111 about this topic, and for applications which perform log
112 analysis, check the <a href="http://dmoz.org/Computers/Software/Internet/Site_Management/Log_analysis/">
113 Open Directory</a> or <a href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Log_Analysis_Tools/">
116 <p>Various versions of Apache httpd have used other modules and
117 directives to control access logging, including
118 mod_log_referer, mod_log_agent, and the
119 <code>TransferLog</code> directive. The <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a> directive now subsumes
120 the functionality of all the older directives.</p>
122 <p>The format of the access log is highly configurable. The
123 format is specified using a <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a> that
124 looks much like a C-style printf(1) format string. Some
125 examples are presented in the next sections. For a complete
126 list of the possible contents of the format string, see the <a href="mod/mod_log_config.html#formats">mod_log_config
127 documentation</a>.</p>
129 <h3><a name="common">Common Log Format</a></h3>
132 <p>A typical configuration for the access log might look as
135 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
136 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br>
137 CustomLog logs/access_log common
138 </code></td></tr></table></blockquote>
140 <p>This defines the <em>nickname</em> <code>common</code> and
141 associates it with a particular log format string. The format
142 string consists of percent directives, each of which tell the
143 server to log a particular piece of information. Literal
144 characters may also be placed in the format string and will be
145 copied directly into the log output. The quote character
146 (<code>"</code>) must be escaped by placing a back-slash before
147 it to prevent it from being interpreted as the end of the
148 format string. The format string may also contain the special
149 control characters "<code>\n</code>" for new-line and
150 "<code>\t</code>" for tab.</p>
152 <p>The <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a>
153 directive sets up a new log file using the defined
154 <em>nickname</em>. The filename for the access log is relative to
155 the <a href="./mod/core.html#serverroot" class="directive"><code class="directive">ServerRoot</code></a> unless it
156 begins with a slash.</p>
158 <p>The above configuration will write log entries in a format
159 known as the Common Log Format (CLF). This standard format can
160 be produced by many different web servers and read by many log
161 analysis programs. The log file entries produced in CLF will
162 look something like this:</p>
164 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
165 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
166 /apache_pb.gif HTTP/1.0" 200 2326
167 </code></td></tr></table></blockquote>
169 <p>Each part of this log entry is described below.</p>
172 <dt><code>127.0.0.1</code> (<code>%h</code>)</dt>
174 <dd>This is the IP address of the client (remote host) which
175 made the request to the server. If <a href="./mod/core.html#hostnamelookups" class="directive"><code class="directive">HostnameLookups</code></a> is
176 set to <code>On</code>, then the server will try to determine
177 the hostname and log it in place of the IP address. However,
178 this configuration is not recommended since it can
179 significantly slow the server. Instead, it is best to use a
180 log post-processor such as <a href="programs/logresolve.html">logresolve</a> to determine
181 the hostnames. The IP address reported here is not
182 necessarily the address of the machine at which the user is
183 sitting. If a proxy server exists between the user and the
184 server, this address will be the address of the proxy, rather
185 than the originating machine.</dd>
187 <dt><code>-</code> (<code>%l</code>)</dt>
189 <dd>The "hyphen" in the output indicates that the requested
190 piece of information is not available. In this case, the
191 information that is not available is the RFC 1413 identity of
192 the client determined by <code>identd</code> on the clients
193 machine. This information is highly unreliable and should
194 almost never be used except on tightly controlled internal
195 networks. Apache httpd will not even attempt to determine
196 this information unless <a href="./mod/core.html#identitycheck" class="directive"><code class="directive">IdentityCheck</code></a> is set
197 to <code>On</code>.</dd>
199 <dt><code>frank</code> (<code>%u</code>)</dt>
201 <dd>This is the userid of the person requesting the document
202 as determined by HTTP authentication. The same value is
203 typically provided to CGI scripts in the
204 <code>REMOTE_USER</code> environment variable. If the status
205 code for the request (see below) is 401, then this value
206 should not be trusted because the user is not yet
207 authenticated. If the document is not password protected,
208 this entry will be "<code>-</code>" just like the previous
211 <dt><code>[10/Oct/2000:13:55:36 -0700]</code>
212 (<code>%t</code>)</dt>
215 The time that the server finished processing the request.
219 <code>[day/month/year:hour:minute:second zone]<br>
226 zone = (`+' | `-') 4*digit</code>
228 It is possible to have the time displayed in another format
229 by specifying <code>%{format}t</code> in the log format
230 string, where <code>format</code> is as in
231 <code>strftime(3)</code> from the C standard library.
234 <dt><code>"GET /apache_pb.gif HTTP/1.0"</code>
235 (<code>\"%r\"</code>)</dt>
237 <dd>The request line from the client is given in double
238 quotes. The request line contains a great deal of useful
239 information. First, the method used by the client is
240 <code>GET</code>. Second, the client requested the resource
241 <code>/apache_pb.gif</code>, and third, the client used the
242 protocol <code>HTTP/1.0</code>. It is also possible to log
243 one or more parts of the request line independently. For
244 example, the format string "<code>%m %U%q %H</code>" will log
245 the method, path, query-string, and protocol, resulting in
246 exactly the same output as "<code>%r</code>".</dd>
248 <dt><code>200</code> (<code>%>s</code>)</dt>
250 <dd>This is the status code that the server sends back to the
251 client. This information is very valuable, because it reveals
252 whether the request resulted in a successful response (codes
253 beginning in 2), a redirection (codes beginning in 3), an
254 error caused by the client (codes beginning in 4), or an
255 error in the server (codes beginning in 5). The full list of
256 possible status codes can be found in the <a href="http://www.w3.org/Protocols/rfc2616/rfc2616.txt">HTTP
257 specification</a> (RFC2616 section 10).</dd>
259 <dt><code>2326</code> (<code>%b</code>)</dt>
261 <dd>The last entry indicates the size of the object returned
262 to the client, not including the response headers. If no
263 content was returned to the client, this value will be
264 "<code>-</code>". To log "<code>0</code>" for no content, use
265 <code>%B</code> instead.</dd>
269 <h3><a name="combined">Combined Log Format</a></h3>
272 <p>Another commonly used format string is called the Combined
273 Log Format. It can be used as follows.</p>
275 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
276 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
277 \"%{User-agent}i\"" combined<br>
278 CustomLog log/acces_log combined
279 </code></td></tr></table></blockquote>
281 <p>This format is exactly the same as the Common Log Format,
282 with the addition of two more fields. Each of the additional
283 fields uses the percent-directive
284 <code>%{<em>header</em>}i</code>, where <em>header</em> can be
285 any HTTP request header. The access log under this format will
288 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
289 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
290 /apache_pb.gif HTTP/1.0" 200 2326
291 "http://www.example.com/start.html" "Mozilla/4.08 [en]
293 </code></td></tr></table></blockquote>
295 <p>The additional fields are:</p>
298 <dt><code>"http://www.example.com/start.html"</code>
299 (<code>\"%{Referer}i\"</code>)</dt>
301 <dd>The "Referer" (sic) HTTP request header. This gives the
302 site that the client reports having been referred from. (This
303 should be the page that links to or includes
304 <code>/apache_pb.gif</code>).</dd>
306 <dt><code>"Mozilla/4.08 [en] (Win98; I ;Nav)"</code>
307 (<code>\"%{User-agent}i\"</code>)</dt>
309 <dd>The User-Agent HTTP request header. This is the
310 identifying information that the client browser reports about
315 <h3><a name="multiple">Multiple Access Logs</a></h3>
318 <p>Multiple access logs can be created simply by specifying
319 multiple <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a>
320 directives in the configuration
321 file. For example, the following directives will create three
322 access logs. The first contains the basic CLF information,
323 while the second and third contain referer and browser
324 information. The last two <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a> lines show how
325 to mimic the effects of the <code>ReferLog</code> and <code>AgentLog</code> directives.</p>
327 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
328 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br>
329 CustomLog logs/access_log common<br>
330 CustomLog logs/referer_log "%{Referer}i -> %U"<br>
331 CustomLog logs/agent_log "%{User-agent}i"
332 </code></td></tr></table></blockquote>
334 <p>This example also shows that it is not necessary to define a
335 nickname with the <a href="./mod/mod_log_config.html#logformat" class="directive"><code class="directive">LogFormat</code></a> directive. Instead,
336 the log format can be specified directly in the <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a> directive.</p>
339 <h3><a name="conditional">Conditional Logs</a></h3>
342 <p>There are times when it is convenient to exclude certain
343 entries from the access logs based on characteristics of the
344 client request. This is easily accomplished with the help of <a href="env.html">environment variables</a>. First, an
345 environment variable must be set to indicate that the request
346 meets certain conditions. This is usually accomplished with
347 <a href="./mod/mod_setenvif.html#setenvif" class="directive"><code class="directive">SetEnvIf</code></a>. Then the
348 <code>env=</code> clause of the <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a> directive is used to
349 include or exclude requests where the environment variable is
350 set. Some examples:</p>
352 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
353 # Mark requests from the loop-back interface<br>
354 SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog<br>
355 # Mark requests for the robots.txt file<br>
356 SetEnvIf Request_URI "^/robots\.txt$" dontlog<br>
357 # Log what remains<br>
358 CustomLog logs/access_log common env=!dontlog
359 </code></td></tr></table></blockquote>
361 <p>As another example, consider logging requests from
362 english-speakers to one log file, and non-english speakers to a
363 different log file.</p>
365 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
366 SetEnvIf Accept-Language "en" english<br>
367 CustomLog logs/english_log common env=english<br>
368 CustomLog logs/non_english_log common env=!english
369 </code></td></tr></table></blockquote>
371 <p>Although we have just shown that conditional logging is very
372 powerful and flexibly, it is not the only way to control the
373 contents of the logs. Log files are more useful when they
374 contain a complete record of server activity. It is often
375 easier to simply post-process the log files to remove requests
376 that you do not want to consider.</p>
378 <h2><a name="rotation">Rotation Logs</a></h2>
381 <p>On even a moderately busy server, the quantity of
382 information stored in the log files is very large. The access
383 log file typically grows 1 MB or more per 10,000 requests. It
384 will consequently be necessary to periodically rotate the log
385 files by moving or deleting the existing logs. This cannot be
386 done while the server is running, because Apache will continue
387 writing to the old log file as long as it holds the file open.
388 Instead, the server must be <a href="stopping.html">restarted</a> after the log files are
389 moved or deleted so that it will open new log files.</p>
391 <p>By using a <em>graceful</em> restart, the server can be
392 instructed to open new log files without losing any existing or
393 pending connections from clients. However, in order to
394 accomplish this, the server must continue to write to the old
395 log files while it finishes serving old requests. It is
396 therefore necessary to wait for some time after the restart
397 before doing any processing on the log files. A typical
398 scenario that simply rotates the logs and compresses the old
399 logs to save space is:</p>
401 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
402 mv access_log access_log.old<br>
403 mv error_log error_log.old<br>
404 apachectl graceful<br>
406 gzip access_log.old error_log.old
407 </code></td></tr></table></blockquote>
409 <p>Another way to perform log rotation is using <a href="#piped">piped logs</a> as discussed in the next
411 <h2><a name="piped">Piped Logs</a></h2>
414 <p>Apache httpd is capable of writing error and access log
415 files through a pipe to another process, rather than directly
416 to a file. This capability dramatically increases the
417 flexibility of logging, without adding code to the main server.
418 In order to write logs to a pipe, simply replace the filename
419 with the pipe character "<code>|</code>", followed by the name
420 of the executable which should accept log entries on its
421 standard input. Apache will start the piped-log process when
422 the server starts, and will restart it if it crashes while the
423 server is running. (This last feature is why we can refer to
424 this technique as "reliable piped logging".)</p>
426 <p>Piped log processes are spawned by the parent Apache httpd
427 process, and inherit the userid of that process. This means
428 that piped log programs usually run as root. It is therefore
429 very important to keep the programs simple and secure.</p>
431 <p>Some simple examples using piped logs:</p>
433 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
434 # compressed logs<br>
435 CustomLog "|/usr/bin/gzip -c >>
436 /var/log/access_log.gz" common<br>
437 # almost-real-time name resolution<br>
438 CustomLog "|/usr/local/apache/bin/logresolve >>
439 /var/log/access_log" common
440 </code></td></tr></table></blockquote>
442 <p>Notice that quotes are used to enclose the entire command
443 that will be called for the pipe. Although these examples are
444 for the access log, the same technique can be used for the
447 <p>One important use of piped logs is to allow log rotation
448 without having to restart the server. The Apache HTTP Server
449 includes a simple program called <a href="programs/rotatelogs.html">rotatelogs</a> for this
450 purpose. For example, to rotate the logs every 24 hours, you
453 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
454 CustomLog "|/usr/local/apache/bin/rotatelogs
455 /var/log/access_log 86400" common
456 </code></td></tr></table></blockquote>
458 <p>A similar, but much more flexible log rotation program
459 called <a href="http://www.cronolog.org/">cronolog</a>
460 is available at an external site.</p>
462 <p>As with conditional logging, piped logs are a very powerful
463 tool, but they should not be used where a simpler solution like
464 off-line post-processing is available.</p>
465 <h2><a name="virtualhost">Virtual Hosts</a></h2>
468 <p>When running a server with many <a href="vhosts/">virtual
469 hosts</a>, there are several options for dealing with log
470 files. First, it is possible to use logs exactly as in a
471 single-host server. Simply by placing the logging directives
472 outside the <a href="./mod/core.html#virtualhost" class="directive"><code class="directive"><VirtualHost></code></a> sections in the
473 main server context, it is possible to log all requests in the
474 same access log and error log. This technique does not allow
475 for easy collection of statistics on individual virtual
478 <p>If <a href="./mod/mod_log_config.html#customlog" class="directive"><code class="directive">CustomLog</code></a>
479 or <a href="./mod/core.html#errorlog" class="directive"><code class="directive">ErrorLog</code></a>
480 directives are placed inside a
481 <a href="./mod/core.html#virtualhost" class="directive"><code class="directive"><VirtualHost></code></a>
482 section, all requests or errors for that virtual host will be
483 logged only to the specified file. Any virtual host which does
484 not have logging directives will still have its requests sent
485 to the main server logs. This technique is very useful for a
486 small number of virtual hosts, but if the number of hosts is
487 very large, it can be complicated to manage. In addition, it
488 can often create problems with <a href="vhosts/fd-limits.html">insufficient file
491 <p>For the access log, there is a very good compromise. By
492 adding information on the virtual host to the log format
493 string, it is possible to log all hosts to the same log, and
494 later split the log into individual files. For example,
495 consider the following directives.</p>
497 <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>
498 LogFormat "%v %l %u %t \"%r\" %>s %b"
500 CustomLog logs/access_log comonvhost
501 </code></td></tr></table></blockquote>
503 <p>The <code>%v</code> is used to log the name of the virtual
504 host that is serving the request. Then a program like <a href="programs/other.html">split-logfile</a> can be used to
505 post-process the access log in order to split it into one file
506 per virtual host.</p>
507 <h2><a name="other">Other Log Files</a></h2>
510 <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/mpm_common.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#scriptlogbuffer" class="directive"><code class="directive">ScriptLogBuffer</code></a><br><a href="./mod/mod_cgi.html#scriptloglength" class="directive"><code class="directive">ScriptLogLength</code></a><br></td></tr></table>
512 <h3><a name="pidfile">PID File</a></h3>
515 <p>On startup, Apache httpd saves the process id of the parent
516 httpd process to the file <code>logs/httpd.pid</code>. This
517 filename can be changed with the <a href="./mod/mpm_common.html#pidfile" class="directive"><code class="directive">PidFile</code></a> directive. The
518 process-id is for use by the administrator in restarting and
519 terminating the daemon by sending signals to the parent
520 process; on Windows, use the -k command line option instead.
521 For more information see the <a href="stopping.html">Stopping
522 and Restarting</a> page.</p>
525 <h3><a name="scriptlog">Script Log</a></h3>
528 <p>In order to aid in debugging, the
529 <a href="./mod/mod_cgi.html#scriptlog" class="directive"><code class="directive">ScriptLog</code></a> directive
530 allows you to record the input to and output from CGI scripts.
531 This should only be used in testing - not for live servers.
532 More information is available in the <a href="mod/mod_cgi.html">mod_cgi</a> documentation.</p>
535 <h3><a name="rewritelog">Rewrite Log</a></h3>
538 <p>When using the powerful and complex features of <a href="mod/mod_rewrite.html">mod_rewrite</a>, it is almost
539 always necessary to use the <a href="./mod/mod_rewrite.html#rewritelog" class="directive"><code class="directive">RewriteLog</code></a> to help
540 in debugging. This log file produces a detailed analysis of how
541 the rewriting engine transforms requests. The level of detail
542 is controlled by the <a href="./mod/mod_rewrite.html#rewriteloglevel" class="directive"><code class="directive">RewriteLogLevel</code></a> directive.</p>
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