webstack/mod_sed/mod_sed_filter.html

0  jyri <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
0  jyri <html><head>
0  jyri   <meta content="text/html; charset=ISO-8859-1" http-equiv="content-type"><title>mod_sed apache filter</title></head><body>
0  jyri <h1>Filtering the content with sed</h1>
0  jyri <a href="#Introduction">1.1 Introduction</a><br>
0  jyri <a href="#Configuration">1.2 Configuration</a><br>
0  jyri &nbsp;&nbsp;&nbsp;<a href="#LoadingModule">1.2.1
0  jyri Loading a module</a><br>
0  jyri &nbsp;&nbsp;&nbsp;<a href="#AddingAFilter">1.2.2
0  jyri Adding a filter</a><br>
0  jyri &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#AddingOutputFilter">1.2.2.1 Adding a output filter</a><br>
0  jyri &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#AddingInputFilter">1.2.2.2 Adding a input filter</a><br>
0  jyri &nbsp;&nbsp;&nbsp;<a href="#SedScripts">1.2.3
0  jyri Sed scripts</a><br>
0  jyri &nbsp;&nbsp;&nbsp;<a href="#RemovingFilter">1.2.4
0  jyri Removing a filter</a><br>
0  jyri &nbsp;&nbsp;&nbsp;<a href="#Examples">1.2.5
0  jyri Examples</a><br>
0  jyri <a href="#Interfaces">1.3 Interfaces</a><br>
0  jyri &nbsp;&nbsp;&nbsp;<a href="#ExportedInterfaces">1.3.1
0  jyri Exported Interfaces</a><br>
0  jyri &nbsp;&nbsp;&nbsp;<a href="#ApacheVersion">1.3.2
0  jyri Apache version requirement</a><br>
0  jyri <hr size="2" width="100%">
0  jyri <h2><a name="Introduction"></a>1.1 Introduction</h2>
0  jyri Sed is a line oriented editor. It is commonly used for&nbsp;search
0  jyri and
0  jyri replace functionality. In Apache, traditionally sed is used as an <a href="http://httpd.apache.org/docs/2.0/mod/mod_ext_filter.html">external
0  jyri content filter</a>.<br>
0  jyri <code><br>
0  jyri # mod_ext_filter directive to define a filter which<br>
0  jyri # replaces text in the response<br>
0  jyri ExtFilterDefine external_sed mode=output intype=text/html&nbsp;<span class="indent">cmd="/bin/sed s/california/CA/g"<br>
0  jyri </span> <br>
0  jyri &lt;Location /&gt;<br>
0  jyri <span class="indent">SetOutputFilter external_sed<br>
0  jyri </span> &lt;/Location&gt;<br>
0  jyri <br>
0  jyri </code>In the above example external process /bin/sed is used to
0  jyri replace the string "california" to "CA". For every filter invocation, a
0  jyri new process "/bin/sed" is created which takes input on standard input
0  jyri and produces the filtered content on standard output. The above
0  jyri technique works fine but it doesn't perform well. Process creation is
0  jyri very costly for every request. Process creation on multithreaded
0  jyri process might be even more costlier. Also sed may not be available on
0  jyri all platforms. <br>
0  jyri <br>
0  jyri mod_sed is a in-process content filter. The filters implement the sed
0  jyri edit commands implemented by Solaris 10 sed
0  jyri program as described in <a href="http://docs.sun.com/app/docs/doc/816-5165/sed-1b?a=view">man
0  jyri page</a>. However unlike sed, mod_sed doesn't take data from
0  jyri standard
0  jyri input. Instead filter act on the entity data sent between client and
0  jyri server. mod_sed can be used as a input or output filter. mod_sed is a
0  jyri content filter which means that it can not be used to modify client or
0  jyri server http headers.<br>
0  jyri <br>
0  jyri <span style="font-weight: bold;"></span>mod_sed
0  jyri output filter accept a chunk of data and execute
0  jyri the sed scripts on data and generates the output which is passed to
0  jyri next filter in the filter chain.<br>
0  jyri <br>
0  jyri mod_sed input filter reads the data from next filter in filter chain
0  jyri and
0  jyri executes the sed scripts and returns&nbsp;the generated data to
0  jyri caller filter in the filter chain.<br>
0  jyri <br>
0  jyri Both input and output filter only process the data if new line
0  jyri character is seen in the content. At the end of the data, rest of the
0  jyri data is treated as last line.<br>
0  jyri <h2><a name="Configuration"></a>1.2
0  jyri Configuration</h2>
0  jyri <h3><a name="LoadingModule"></a>1.2.1 Loading
0  jyri a module</h3>
0  jyri &nbsp; &nbsp; &nbsp; &nbsp; Apache modules can be
0  jyri compiled statically
0  jyri into the httpd process or separate dynamic shared object (dso). If
0  jyri mod_sed is compiled as a dso then it needs to be loaded using Apache's <a href="http://httpd.apache.org/docs/2.2/mod/mod_so.html#loadmodule">LoadModule</a>
0  jyri directive before it can be used e.g<br>
0  jyri <span style="font-family: monospace;">LoadModule&nbsp;sed_module
0  jyri modules/mod_sed.so</span>
0  jyri <h3><a name="AddingAFilter"></a>1.2.2 Adding a
0  jyri filter</h3>
0  jyri &nbsp; &nbsp; &nbsp; &nbsp; Sed
0  jyri filter&nbsp;could be inserted by Apache
0  jyri directives <a href="http://httpd.apache.org/docs/2.2/mod/mod_mime.html#addinputfilter">AddInputFilter</a>
0  jyri or <a href="http://httpd.apache.org/docs/2.2/mod/mod_mime.html#addoutputfilter">AddOutputFilter</a>
0  jyri (or by
0  jyri <a href="http://httpd.apache.org/docs/2.2/mod/core.html#setinputfilter">SetInputFilter</a>/<a href="http://httpd.apache.org/docs/2.2/mod/core.html#setoutputfilter">SetOutputFilter</a>)
0  jyri or similar directives. <br>
0  jyri <h4><a name="AddingOutputFilter"></a>1.2.2.1
0  jyri Adding a output filter</h4>
0  jyri Following directive can be used to&nbsp;add a Sed output filter to
0  jyri html files.<br>
0  jyri <span style="font-family: monospace;">AddOutputFilter Sed
0  jyri &lt;extension&gt;</span><br>
0  jyri e.g<br>
0  jyri <span style="font-family: monospace;">AddOutputFilter Sed
0  jyri html</span><br>
0  jyri <h4><a name="AddingInputFilter"></a>1.2.2.2
0  jyri Adding a input filter</h4>
0  jyri Following directive can be used to&nbsp;add a Sed input filter to
0  jyri php scripts.<br>
0  jyri <span style="font-family: monospace;">AddInputFilter Sed
0  jyri &lt;extension&gt;<br>
0  jyri e.g<br style="font-family: monospace;">
0  jyri </span><span style="font-family: monospace;">AddInputFilter
0  jyri Sed php</span>
0  jyri <h3><a name="SedScripts"></a>1.2.3 Sed scripts</h3>
0  jyri Sed scripts can be provided for input and output filter by <a href="#SedRequestFilter">InputSed</a>
0  jyri and <a href="#SedResponseFilter">OutputSed</a>
0  jyri mod_sed directives respectively.&nbsp; &nbsp;For example :<br>
0  jyri <span style="font-family: monospace;">OutputSed "script"<br>
0  jyri OutputSed "script"</span><br>
0  jyri InputSed and OutputSed takes single argument. These directives can be
0  jyri used multiple times to specify multiple scripts. These sed scripts will
0  jyri get executed in the order of their appearance in
0  jyri configuration file.<br>
0  jyri <h3><a name="RemovingFilter"></a>1.2.4
0  jyri Removing a filter</h3>
0  jyri Sed filter could be removed by <a href="http://httpd.apache.org/docs/2.2/mod/mod_mime.html#removeoutputfilter">RemoveOutputFilter</a>
0  jyri or <a href="http://httpd.apache.org/docs/2.2/mod/mod_mime.html#removeinputfilter">RemoveInputFilter</a>
0  jyri Apache directives.
0  jyri <h3><a name="Examples"></a>1.2.5 Examples</h3>
0  jyri Adding a output filter :<br>
0  jyri <span style="font-family: monospace;">&lt;Directory
0  jyri "/var/www/docs/sed"&gt;</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;">&nbsp;&nbsp;
0  jyri AddOutputFilter Sed html</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;">&nbsp;&nbsp; OutputSed "s/california/CA/g"<br>
0  jyri &nbsp; &nbsp;OutputSed "s/washington/WA/g"</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;">&lt;/Directory&gt;</span><br style="font-family: monospace;">
0  jyri <br>
0  jyri The above example will replace the string "california" to "CA" and the
0  jyri string "washington" to WA in html document before sending to client.<br>
0  jyri <br>
0  jyri Adding an input filter :<br>
0  jyri <span style="font-family: monospace;">&lt;Directory
0  jyri "/var/www/docs/sed"&gt;</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;">&nbsp;
0  jyri &nbsp;
0  jyri AddInputFilter Sed php</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;">&nbsp;
0  jyri &nbsp; InputSed "s/california/CA/gi"</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;">&lt;/Directory&gt;</span><br style="font-family: monospace;">
0  jyri <br>
0  jyri In the above example, the string "california" will be replaced to "CA"
0  jyri in any request data provided to php scripts.<br>
0  jyri <br>
0  jyri Removing a output filter :<br>
0  jyri <span style="font-family: monospace;">&lt;Directory
0  jyri "/var/www/docs/sed/subdir1"&gt;</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;"></span><span style="font-family: monospace;">&nbsp; &nbsp;
0  jyri RemoveOutputFilter Sed html</span><br style="font-family: monospace;">
0  jyri <span style="font-family: monospace;">&lt;/Directory&gt;</span><br>
0  jyri <h2><a name="Interfaces"></a>1.3 Interfaces</h2>
0  jyri <h3><a name="ExportedInterfaces"></a>1.3.1
0  jyri Exported Interfaces </h3>
0  jyri <table style="text-align: left; width: 100%;" border="1" cellpadding="2" cellspacing="2">
0  jyri   <tbody>
0  jyri     <tr>
0  jyri       <td style="font-weight: bold;">Interface</td>
0  jyri       <td style="font-weight: bold;">Classification</td>
0  jyri       <td><span style="font-weight: bold;">Context</span></td>
0  jyri       <td style="font-weight: bold;">Description</td>
0  jyri     </tr>
0  jyri     <tr>
0  jyri       <td>Sed</td>
0  jyri       <td>Filter name.</td>
0  jyri       <td>Filter handling directives</td>
0  jyri       <td>Filter can be added using several possible Apache
0  jyri directives.
0  jyri Name of the filter tells Apache which filter to add. It can be used for
0  jyri both input and output filter.</td>
0  jyri     </tr>
0  jyri     <tr>
0  jyri       <td>sed_module</td>
0  jyri       <td>Module name</td>
0  jyri       <td>-</td>
0  jyri       <td>If mod_sed is compiled as a dso, module name must be
0  jyri provided as an argument to <a href="http://httpd.apache.org/docs/2.2/mod/mod_so.html#loadmodule">LoadModule</a></td>
0  jyri     </tr>
0  jyri     <tr>
0  jyri       <td><a name="SedResponseFilter"></a>OutputSed</td>
0  jyri       <td>Directive</td>
0  jyri       <td>directory</td>
0  jyri       <td>Directive to specify the multiple sed scripts to output
0  jyri filter.</td>
0  jyri     </tr>
0  jyri     <tr>
0  jyri       <td><a name="SedRequestFilter"></a>InputSed</td>
0  jyri       <td>Directive</td>
0  jyri       <td>directory</td>
0  jyri       <td>Directive to specify the multiple sed scripts to input
0  jyri filter.</td>
0  jyri     </tr>
0  jyri
0  jyri
0  jyri
0  jyri   </tbody>
0  jyri </table>
0  jyri <h4><a name="ApacheVersion"></a>1.3.2 Apache
0  jyri version requirement :</h4>
0  jyri &nbsp; &nbsp; &nbsp; &nbsp; Module will work from
0  jyri Apache 2.2.x and above.<br>
0  jyri <br>
0  jyri </body></html>