<modulesynopsis>
<name>mod_ext_filter</name>
-<description>Pass the response body
- through an external program before delivery to the
- client</description>
+<description>Pass the response body through an external program before
+delivery to the client</description>
<status>Experimental</status>
<sourcefile>mod_ext_filter.c</sourcefile>
<identifier>ext_filter_module</identifier>
for production use, <module>mod_ext_filter</module> can be used as
a prototype environment for filters.</p>
</summary>
-
-<section><title>Examples</title>
-
-<section><title>Generating HTML from some other type of response</title>
-<example><pre>
-# mod_ext_filter directive to define a filter to HTML-ize text/c files
-# using the external program /usr/bin/enscript, with the type of the
-# result set to text/html
-ExtFilterDefine c-to-html mode=output intype=text/c outtype=text/html \
- cmd="/usr/bin/enscript --color -W html -Ec -o - -"
-
-<Directory "/export/home/trawick/apacheinst/htdocs/c">
-
-# core directive to cause the new filter to be run on output
-SetOutputFilter c-to-html
-
-# mod_mime directive to set the type of .c files to text/c
-AddType text/c .c
-
-# mod_ext_filter directive to set the debug level just high
-# enough to see a log message per request showing the configuration
-# in force
-ExtFilterOptions DebugLevel=1
-
-</Directory>
-</pre></example>
-</section>
-
-<section><title>Implementing a content encoding filter</title>
-<example><pre>
-# mod_ext_filter directive to define the external filter
-ExtFilterDefine gzip mode=output cmd=/bin/gzip
-
-<Location /gzipped>
-
-# core directive to cause the gzip filter to be run on output
-SetOutputFilter gzip
-
-# mod_header directive to add "Content-Encoding: gzip" header field
-Header set Content-Encoding gzip
-
-</Location>
-</pre></example>
-
- <p>Note: this gzip example is just for the purposes of illustration.
- Please refer to <module>mod_deflate</module> for a practical
- implementation.</p>
-</section>
-
-<section><title>Slowing down the server</title>
-<example><pre>
-# mod_ext_filter directive to define a filter which runs everything
-# through cat; cat doesn't modify anything; it just introduces extra
-# pathlength and consumes more resources
-ExtFilterDefine slowdown mode=output cmd=/bin/cat preservescontentlength
-
-<Location />
-
-# core directive to cause the slowdown filter to be run several times on
-# output
-SetOutputFilter slowdown slowdown slowdown
-
-</Location>
-</pre></example>
-</section>
-
-<section><title>Using sed to replace text in the response</title>
-<example><pre>
-# mod_ext_filter directive to define a filter which replaces text in
-# the response
-ExtFilterDefine fixtext mode=output cmd="/bin/sed s/verdana/arial/g" intype=text/html
-
-<Location />
-
-# core directive to cause the fixtext filter to be run on output
-# output
-SetOutputFilter fixtext
-
-</Location>
-</pre></example>
-</section>
-
-<section><title>Tracing another filter</title>
-<example><pre>
-# Trace the data read and written by mod_deflate for a particular
-# client (IP 192.168.1.31) experiencing compression problems.
-# This filter will trace what goes into mod_deflate.
-ExtFilterDefine tracebefore cmd="/bin/tracefilter.pl /tmp/tracebefore" \
- EnableEnv=trace_this_client
-# This filter will trace what goes after mod_deflate. Note that without
-# the ftype parameter, the default filter type of AP_FTYPE_RESOURCE would
-# cause the filter to be placed *before* mod_deflate in the filter
-# chain. Giving it a numeric value slightly higher than
-# AP_FTYPE_CONTENT_SET will ensure that it is placed after mod_deflate.
-ExtFilterDefine traceafter cmd="/bin/tracefilter.pl /tmp/traceafter" \
- EnableEnv=trace_this_client ftype=21
-
-<Directory /usr/local/docs>
- SetEnvIf Remote_Addr 192.168.1.31 trace_this_client
- SetOutputFilter tracebefore;deflate;traceafter
-</Directory>
-</pre></example>
-
-<example><title>Here is the filter which traces the data:</title>
-<pre>
-#!/usr/local/bin/perl -w
-
-use strict;
-
-open(SAVE, ">$ARGV[0]") or die "can't open $ARGV[0]: $?";
-
-while (<STDIN>)
-{
- print SAVE $_;
- print $_;
-}
-
-close(SAVE);
-</pre></example>
-</section>
-
-</section> <!-- Examples -->
+<seealso><a href="../filter.html">The filter documentation</a></seealso>
+
+<section id="examples"><title>Examples</title>
+
+ <section><title>Generating HTML from some other type of response</title>
+ <example>
+ # mod_ext_filter directive to define a filter<br />
+ # to HTML-ize text/c files using the external<br />
+ # program /usr/bin/enscript, with the type of<br />
+ # the result set to text/html<br />
+ ExtFilterDefine c-to-html mode=output \<br />
+ <indent>
+ intype=text/c outtype=text/html \<br />
+ cmd="/usr/bin/enscript --color -W html -Ec -o - -"<br />
+ </indent>
+ <br />
+ <Directory "/export/home/trawick/apacheinst/htdocs/c"><br />
+ <indent>
+ # core directive to cause the new filter to<br />
+ # be run on output<br />
+ SetOutputFilter c-to-html<br />
+ <br />
+ # mod_mime directive to set the type of .c<br />
+ # files to text/c<br />
+ AddType text/c .c<br />
+ <br />
+ # mod_ext_filter directive to set the debug<br />
+ # level just high enough to see a log message<br />
+ # per request showing the configuration in force<br />
+ ExtFilterOptions DebugLevel=1<br />
+ </indent>
+ </Directory>
+ </example>
+ </section>
+
+ <section><title>Implementing a content encoding filter</title>
+ <p>Note: this gzip example is just for the purposes of illustration.
+ Please refer to <module>mod_deflate</module> for a practical
+ implementation.</p>
+
+ <example>
+ # mod_ext_filter directive to define the external filter<br />
+ ExtFilterDefine gzip mode=output cmd=/bin/gzip<br />
+ <br />
+ <Location /gzipped><br />
+ <indent>
+ # core directive to cause the gzip filter to be<br />
+ # run on output<br />
+ SetOutputFilter gzip<br />
+ <br />
+ # mod_header directive to add<br />
+ # "Content-Encoding: gzip" header field<br />
+ Header set Content-Encoding gzip<br />
+ </indent>
+ </Location>
+ </example>
+ </section>
+
+ <section><title>Slowing down the server</title>
+ <example>
+ # mod_ext_filter directive to define a filter<br />
+ # which runs everything through cat; cat doesn't<br />
+ # modify anything; it just introduces extra pathlength<br />
+ # and consumes more resources<br />
+ ExtFilterDefine slowdown mode=output cmd=/bin/cat \<br />
+ <indent>
+ preservescontentlength<br />
+ </indent>
+ <br />
+ <Location /><br />
+ <indent>
+ # core directive to cause the slowdown filter to<br />
+ # be run several times on output<br />
+ #<br />
+ SetOutputFilter slowdown;slowdown;slowdown<br />
+ </indent>
+ </Location>
+ </example>
+ </section>
+
+ <section><title>Using sed to replace text in the response</title>
+ <example>
+ # mod_ext_filter directive to define a filter which<br />
+ # replaces text in the response<br />
+ #<br />
+ ExtFilterDefine fixtext mode=output intype=text/html \<br />
+ <indent>
+ cmd="/bin/sed s/verdana/arial/g"<br />
+ </indent>
+ <br />
+ <Location /><br />
+ <indent>
+ # core directive to cause the fixtext filter to<br />
+ # be run on output<br />
+ SetOutputFilter fixtext<br />
+ </indent>
+ </Location>
+ </example>
+ </section>
+
+ <section><title>Tracing another filter</title>
+ <example>
+ # Trace the data read and written by mod_deflate<br />
+ # for a particular client (IP 192.168.1.31)<br />
+ # experiencing compression problems.<br />
+ # This filter will trace what goes into mod_deflate.<br />
+ ExtFilterDefine tracebefore \<br />
+ <indent>
+ cmd="/bin/tracefilter.pl /tmp/tracebefore" \<br />
+ EnableEnv=trace_this_client<br />
+ </indent>
+ <br />
+ # This filter will trace what goes after mod_deflate.<br />
+ # Note that without the ftype parameter, the default<br />
+ # filter type of AP_FTYPE_RESOURCE would cause the<br />
+ # filter to be placed *before* mod_deflate in the filter<br />
+ # chain. Giving it a numeric value slightly higher than<br />
+ # AP_FTYPE_CONTENT_SET will ensure that it is placed<br />
+ # after mod_deflate.<br />
+ ExtFilterDefine traceafter \<br />
+ <indent>
+ cmd="/bin/tracefilter.pl /tmp/traceafter" \<br />
+ EnableEnv=trace_this_client ftype=21<br />
+ </indent>
+ <br />
+ <Directory /usr/local/docs><br />
+ <indent>
+ SetEnvIf Remote_Addr 192.168.1.31 trace_this_client<br />
+ SetOutputFilter tracebefore;deflate;traceafter<br />
+ </indent>
+ </Directory>
+ </example>
+
+ <example><title>Here is the filter which traces the data:</title>
+ #!/usr/local/bin/perl -w<br />
+ use strict;<br />
+ <br />
+ open(SAVE, ">$ARGV[0]")<br />
+ <indent>
+ or die "can't open $ARGV[0]: $?";<br />
+ </indent>
+ <br />
+ while (<STDIN>) {<br />
+ <indent>
+ print SAVE $_;<br />
+ print $_;<br />
+ </indent>
+ }<br />
+ <br />
+ close(SAVE);
+ </example>
+ </section>
+</section> <!-- /Examples -->
<directivesynopsis>
<name>ExtFilterDefine</name>
-<syntax>ExtFilterDefine <em>filtername</em> <em>parameters</em></syntax>
+<description>Define an external filter</description>
+<syntax>ExtFilterDefine <var>filtername</var> <var>parameters</var></syntax>
<contextlist><context>server config</context></contextlist>
<usage>
characteristics of an external filter, including the program to
run and its arguments.</p>
- <p><em>filtername</em> specifies the name of the filter being
+ <p><var>filtername</var> specifies the name of the filter being
defined. This name can then be used in SetOutputFilter
directives. It must be unique among all registered filters.
<em>At the present time, no error is reported by the
<p>Subsequent parameters can appear in any order and define the
external command to run and certain other characteristics. The
- only required parameter is <em>cmd=</em>. These parameters
+ only required parameter is <code>cmd=</code>. These parameters
are:</p>
<dl>
- <dt>cmd=<em>cmdline</em></dt>
+ <dt><code>cmd=<var>cmdline</var></code></dt>
<dd>The <code>cmd=</code> keyword allows you to specify the
external command to run. If there are arguments after the
program name, the command line should be surrounded in
- quotation marks (e.g., <em>cmd="/bin/mypgm arg1 arg2"</em>.
- Normal shell quoting is not necessary since the program is
- run directly, bypassing the shell. Program arguments are
- blank-delimited. A backslash can be used to escape blanks
- which should be part of a program argument. Any backslashes
- which are part of the argument must be escaped with backslash
- themselves. In addition to the standard CGI environment
+ quotation marks (<em>e.g.</em>, <code>cmd="<var>/bin/mypgm</var>
+ <var>arg1</var> <var>arg2</var>"</code>. Normal shell quoting is
+ not necessary since the program is run directly, bypassing the shell.
+ Program arguments are blank-delimited. A backslash can be used to
+ escape blanks which should be part of a program argument. Any
+ backslashes which are part of the argument must be escaped with
+ backslash themselves. In addition to the standard CGI environment
variables, DOCUMENT_URI, DOCUMENT_PATH_INFO, and
QUERY_STRING_UNESCAPED will also be set for the program.</dd>
- <dt>mode=<em>mode</em></dt>
+ <dt><code>mode=<var>mode</var></code></dt>
- <dd><em>mode</em> should be <em>output</em> for now (the
- default). In the future, <em>mode=input</em> will be used to
+ <dd><code>mode</code> should be <code>output</code> for now (the
+ default). In the future, <code>mode=input</code> will be used to
specify a filter for request bodies.</dd>
- <dt>intype=<em>imt</em></dt>
+ <dt><code>intype=<var>imt</var></code></dt>
- <dd>This parameter specifies the internet media type (i.e.,
+ <dd>This parameter specifies the internet media type (<em>i.e.</em>,
MIME type) of documents which should be filtered. By default,
all documents are filtered. If <code>intype=</code> is
specified, the filter will be disabled for documents of other
types.</dd>
- <dt>outtype=<em>imt</em></dt>
+ <dt><code>outtype=<var>imt</var></code></dt>
- <dd>This parameter specifies the internet media type (i.e.,
+ <dd>This parameter specifies the internet media type (<em>i.e.</em>,
MIME type) of filtered documents. It is useful when the
filter changes the internet media type as part of the
filtering operation. By default, the internet media type is
unchanged.</dd>
- <dt>PreservesContentLength</dt>
+ <dt><code>PreservesContentLength</code></dt>
<dd>The <code>PreservesContentLength</code> keyword specifies
that the filter preserves the content length. This is not the
event that the filter doesn't modify the length, this keyword
should be specified.</dd>
- <dt>ftype=<em>filtertype</em></dt>
+ <dt><code>ftype=<var>filtertype</var></code></dt>
<dd>This parameter specifies the numeric value for filter type
that the filter should be registered as. The default value,
the AP_FTYPE_foo definitions in util_filter.h for appropriate
values.</dd>
- <dt>disableenv=<em>env</em></dt>
+ <dt><code>disableenv=<var>env</var></code></dt>
<dd>This parameter specifies the name of an environment variable
which, if set, will disable the filter.</dd>
- <dt>enableenv=<em>env</em></dt>
+ <dt><code>enableenv=<var>env</var></code></dt>
<dd>This parameter specifies the name of an environment variable
which must be set, or the filter will be disabled.</dd>
-
</dl>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>ExtFilterOptions</name>
-<syntax>ExtFilterOptions
- <em>option</em> [<em>option</em>] ...</syntax>
+<description>Configure <module>mod_ext_filter</module> options</description>
+<syntax>ExtFilterOptions <var>option</var> [<var>option</var>] ...</syntax>
<default>ExtFilterOptions DebugLevel=0 NoLogStderr</default>
<contextlist><context>directory</context></contextlist>
<usage>
<p>The <directive>ExtFilterOptions</directive> directive specifies
- special processing options for <code>mod_ext_filter</code>.
- <em>Option</em> can be one of</p>
+ special processing options for <module>mod_ext_filter</module>.
+ <var>Option</var> can be one of</p>
<dl>
- <dt>DebugLevel=<em>n</em></dt>
+ <dt><code>DebugLevel=<var>n</var></code></dt>
<dd>
The <code>DebugLevel</code> keyword allows you to specify
the level of debug messages generated by
- <code>mod_ext_filter</code>. By default, no debug messages
+ <module>mod_ext_filter</module>. By default, no debug messages
are generated. This is equivalent to
<code>DebugLevel=0</code>. With higher numbers, more debug
messages are generated, and server performance will be
described with the definitions of the DBGLVL_ constants
near the beginning of <code>mod_ext_filter.c</code>.
- <p>Note: The core directive LogLevel should be used to
- cause debug messages to be stored in the Apache error
- log.</p>
+ <p>Note: The core directive <directive module="core"
+ >LogLevel</directive> should be used to cause debug messages to
+ be stored in the Apache error log.</p>
</dd>
- <dt>LogStderr | NoLogStderr</dt>
+ <dt><code>LogStderr | NoLogStderr</code></dt>
<dd>The <code>LogStderr</code> keyword specifies that
messages written to standard error by the external filter
<code>NoLogStderr</code> disables this feature.</dd>
</dl>
-<example><title>Example</title>
- ExtFilterOptions LogStderr DebugLevel=0
-</example>
+ <example><title>Example</title>
+ ExtFilterOptions LogStderr DebugLevel=0
+ </example>
<p>Messages written to the filter's standard error will be stored
in the Apache error log. No debug messages will be generated by
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