<?xml version="1.0"?>
<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<!DOCTYPE document [
  <!ENTITY project SYSTEM "project.xml">
]>
<document url="cgi-howto.html">

    &project;

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

<body>

<section name="Table of Contents">
<toc/>
</section>

<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>

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

</section>

<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. You may explicitly set this parameter to be an empty string
if your script is itself executable (e.g. an exe file). Default is
<code>perl</code>.</li>
<li><strong>executable-arg-1</strong>, <strong>executable-arg-2</strong>,
and so on - additional arguments for the executable. These precede the
CGI script name. By default there are no additional arguments.</li>
<li><strong>parameterEncoding</strong> - Name of the parameter encoding
to be used with the CGI 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>
<li><strong>stderrTimeout</strong> - The time (in milliseconds) to wait for
the reading of stderr to complete before terminating the CGI process. Default
is 2000.</li>
</ul>
</p>

</section>

</body>

</document>
