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        <author email="glenn@apache.org">Glenn L. Nielsen</author>
        <title>CGI How To</title>
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<section name="Introduction">

<p>The CGI (Common Gateway Interface) defines a way for a web server to
interact with external content-generating programs, which are often
referred to as CGI programs or CGI scripts.
</p>

<p>Within Tomcat, CGI support can be added when you are using Tomcat as your
HTTP server and require CGI support.  Typically this is done
during development when you don't want to run a web server like 
Apache httpd.
Tomcat's CGI support is largely compatible with Apache httpd's, 
but there are some limitations (e.g., only one cgi-bin directory).
</p>

<p>CGI support is implemented using the servlet class
<code>org.apache.catalina.servlets.CGIServlet</code>.  Traditionally,
this servlet is mapped to the URL pattern "/cgi-bin/*".</p>

<p>By default CGI support is disabled in Tomcat.</p>
</section>

<section name="Installation">

<p><strong>CAUTION</strong> - CGI scripts are used to execute programs
external to the Tomcat JVM. If you are using the Java SecurityManager this
will bypass your security policy configuration in <code>catalina.policy.</code></p>

<p>Remove the XML comments from around the CGI servlet and servlet-mapping
configuration in <code>$CATALINA_BASE/conf/web.xml</code>.</p>
</section>

<p>Only Contexts which are marked as privileged may use the CGI servlet (see the
privileged property of the Context element).</p>

<section name="Configuration">

<p>There are several servlet init parameters which can be used to
configure the behaviour of the CGI servlet.
<ul>
<li><strong>cgiPathPrefix</strong> - The CGI search path will start at
the web application root directory + File.separator + this prefix.
The default cgiPathPrefix is <code>WEB-INF/cgi</code></li>
<li><strong>debug</strong> - Debugging detail level for messages logged
by this servlet. Default 0.</li>
<li><strong>executable</strong> - The of the executable to be used to
run the script. Default is <code>perl</code>.</li>
<li><strong>parameterEncoding</strong> - Name of the parameter encoding
to be used with the GCI servlet. Default is
<code>System.getProperty("file.encoding","UTF-8")</code>.</li>
<li><strong>passShellEnvironment</strong> - Should the shell environment
variables (if any) be passed to the CGI script? Default is
<code>false</code>.</li>
</ul>
</p>

</section>

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