mod_ext_filter.html.en 18.2 KB
Newer Older
powelld's avatar
powelld committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head>
<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type" />
<!--
        XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
              This file is generated from xml source: DO NOT EDIT
        XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
      -->
<title>mod_ext_filter - Apache HTTP Server Version 2.4</title>
<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
<script src="../style/scripts/prettify.min.js" type="text/javascript">
</script>

<link href="../images/favicon.ico" rel="shortcut icon" /></head>
<body>
<div id="page-header">
<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
<p class="apache">Apache HTTP Server Version 2.4</p>
<img alt="" src="../images/feather.png" /></div>
<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
<div id="path">
<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.4</a> &gt; <a href="./">Modules</a></div>
<div id="page-content">
<div id="preamble"><h1>Apache Module mod_ext_filter</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_ext_filter.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../fr/mod/mod_ext_filter.html" hreflang="fr" rel="alternate" title="Franais">&nbsp;fr&nbsp;</a> |
<a href="../ja/mod/mod_ext_filter.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
<a href="../ko/mod/mod_ext_filter.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Pass the response body through an external program before
delivery to the client</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">ModuleIdentifier:</a></th><td>ext_filter_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">SourceFile:</a></th><td>mod_ext_filter.c</td></tr></table>
<h3>Summary</h3>

    <p><code class="module"><a href="../mod/mod_ext_filter.html">mod_ext_filter</a></code> presents a simple and familiar
    programming model for <a href="../filter.html">filters</a>. With
    this module, a program which reads from stdin and writes to stdout
    (i.e., a Unix-style filter command) can be a filter for
    Apache. This filtering mechanism is much slower than using a
    filter which is specially written for the Apache API and runs
    inside of the Apache server process, but it does have the
    following benefits:</p>

    <ul>
      <li>the programming model is much simpler</li>

      <li>any programming/scripting language can be used, provided
      that it allows the program to read from standard input and
      write to standard output</li>

      <li>existing programs can be used unmodified as Apache
      filters</li>
    </ul>

    <p>Even when the performance characteristics are not suitable
    for production use, <code class="module"><a href="../mod/mod_ext_filter.html">mod_ext_filter</a></code> can be used as
    a prototype environment for filters.</p>

</div>
<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#examples">Examples</a></li>
</ul><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#extfilterdefine">ExtFilterDefine</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#extfilteroptions">ExtFilterOptions</a></li>
</ul>
<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mod_ext_filter">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mod_ext_filter">Report a bug</a></li></ul><h3>See also</h3>
<ul class="seealso">
<li><a href="../filter.html">Filters</a></li>
<li><a href="#comments_section">Comments</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="examples" id="examples">Examples</a></h2>

    <h3>Generating HTML from some other type of response</h3>
      <pre class="prettyprint lang-config"># 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 - -"

&lt;Directory "/export/home/trawick/apacheinst/htdocs/c"&gt;
    # 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
&lt;/Directory&gt;</pre>

    

    <h3>Implementing a content encoding filter</h3>
      <p>Note: this gzip example is just for the purposes of illustration.
      Please refer to <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> for a practical
      implementation.</p>

      <pre class="prettyprint lang-config"># mod_ext_filter directive to define the external filter
ExtFilterDefine gzip mode=output cmd=/bin/gzip

&lt;Location "/gzipped"&gt;
    
    # core directive to cause the gzip filter to be
    # run on output
    SetOutputFilter gzip
    
    # mod_headers directive to add
    # "Content-Encoding: gzip" header field
    Header set Content-Encoding gzip
&lt;/Location&gt;</pre>

    

    <h3>Slowing down the server</h3>
      <pre class="prettyprint lang-config"># 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

&lt;Location "/"&gt;
    # core directive to cause the slowdown filter to
    # be run several times on output
    #
    SetOutputFilter slowdown;slowdown;slowdown
&lt;/Location&gt;</pre>

    

    <h3>Using sed to replace text in the response</h3>
      <pre class="prettyprint lang-config"># mod_ext_filter directive to define a filter which
# replaces text in the response
#
ExtFilterDefine fixtext mode=output intype=text/html \
    cmd="/bin/sed s/verdana/arial/g"

&lt;Location "/"&gt;
    # core directive to cause the fixtext filter to
    # be run on output
    SetOutputFilter fixtext
&lt;/Location&gt;</pre>


<div class="note">
<p>You can do the same thing using <code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code>
without invoking an external process.</p>
</div>
    

    <h3>Tracing another filter</h3>
      <pre class="prettyprint lang-config"># 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

&lt;Directory "/usr/local/docs"&gt;
    SetEnvIf Remote_Addr 192.168.1.31 trace_this_client
    SetOutputFilter tracebefore;deflate;traceafter
&lt;/Directory&gt;</pre>


      <div class="example"><h3>Here is the filter which traces the data:</h3><pre class="prettyprint lang-perl">#!/usr/local/bin/perl -w
use strict;

open(SAVE, "&gt;$ARGV[0]")
    or die "can't open $ARGV[0]: $?";

while (&lt;STDIN&gt;) {
    print SAVE $_;
    print $_;
}

close(SAVE);</pre>
</div>
    
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ExtFilterDefine" id="ExtFilterDefine">ExtFilterDefine</a> <a name="extfilterdefine" id="extfilterdefine">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define an external filter</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExtFilterDefine <var>filtername</var> <var>parameters</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ext_filter</td></tr>
</table>
    <p>The <code class="directive">ExtFilterDefine</code> directive defines the
    characteristics of an external filter, including the program to
    run and its arguments.</p>

    <p><var>filtername</var> specifies the name of the filter being
    defined. This name can then be used in <code class="directive"><a href="../mod/core.html#setoutputfilter">SetOutputFilter</a></code>
    directives. It must be unique among all registered filters.
    <em>At the present time, no error is reported by the
    register-filter API, so a problem with duplicate names isn't
    reported to the user.</em></p>

    <p>Subsequent parameters can appear in any order and define the
    external command to run and certain other characteristics. The
    only required parameter is <code>cmd=</code>. These parameters
    are:</p>

    <dl>
      <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 (<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><code>mode=<var>mode</var></code></dt>

      <dd>Use <code>mode=output</code> (the default) for filters which
      process the response.  Use <code>mode=input</code> for filters
      which process the request.  <code>mode=input</code> is available
      in Apache 2.1 and later.</dd>

      <dt><code>intype=<var>imt</var></code></dt>

      <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><code>outtype=<var>imt</var></code></dt>

      <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><code>PreservesContentLength</code></dt>

      <dd>The <code>PreservesContentLength</code> keyword specifies
      that the filter preserves the content length. This is not the
      default, as most filters change the content length. In the
      event that the filter doesn't modify the length, this keyword
      should be specified.</dd>

      <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,
      AP_FTYPE_RESOURCE, is sufficient in most cases.  If the filter
      needs to operate at a different point in the filter chain than
      resource filters, then this parameter will be necessary.  See
      the AP_FTYPE_foo definitions in util_filter.h for appropriate
      values.</dd>

      <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><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>

</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="ExtFilterOptions" id="ExtFilterOptions">ExtFilterOptions</a> <a name="extfilteroptions" id="extfilteroptions">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure <code class="module"><a href="../mod/mod_ext_filter.html">mod_ext_filter</a></code> options</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExtFilterOptions <var>option</var> [<var>option</var>] ...</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ExtFilterOptions NoLogStderr</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_ext_filter</td></tr>
</table>
    <p>The <code class="directive">ExtFilterOptions</code> directive specifies
    special processing options for <code class="module"><a href="../mod/mod_ext_filter.html">mod_ext_filter</a></code>.
    <var>Option</var> can be one of</p>

    <dl>
      <dt><code>LogStderr | NoLogStderr</code></dt>

      <dd>The <code>LogStderr</code> keyword specifies that
      messages written to standard error by the external filter
      program will be saved in the Apache error log.
      <code>NoLogStderr</code> disables this feature.</dd>

      <dt><code>Onfail=[abort|remove]</code></dt>
      <dd>Determines how to proceed if the external filter program
      cannot be started.  With <code>abort</code> (the default value)
      the request will be aborted.  With <code>remove</code>, the
      filter is removed and the request continues without it.</dd>
    </dl>

    <pre class="prettyprint lang-config">ExtFilterOptions LogStderr</pre>


    <p>Messages written to the filter's standard error will be stored
    in the Apache error log.</p>

</div>
</div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/mod/mod_ext_filter.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../fr/mod/mod_ext_filter.html" hreflang="fr" rel="alternate" title="Franais">&nbsp;fr&nbsp;</a> |
<a href="../ja/mod/mod_ext_filter.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
<a href="../ko/mod/mod_ext_filter.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
<script type="text/javascript"><!--//--><![CDATA[//><!--
var comments_shortname = 'httpd';
var comments_identifier = 'http://httpd.apache.org/docs/2.4/mod/mod_ext_filter.html';
(function(w, d) {
    if (w.location.hostname.toLowerCase() == "httpd.apache.org") {
        d.write('<div id="comments_thread"><\/div>');
        var s = d.createElement('script');
        s.type = 'text/javascript';
        s.async = true;
        s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier;
        (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s);
    }
    else { 
        d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>');
    }
})(window, document);
//--><!]]></script></div><div id="footer">
<p class="apache">Copyright 2017 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>
<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!--
if (typeof(prettyPrint) !== 'undefined') {
    prettyPrint();
}
//--><!]]></script>
</body></html>