# Apache Tomcat 4

# CGI How To

Introduction

> 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.

> Within Tomcat CGI support can be added when using Tomcat as your HTTP server and you require CGI support. Typically this is done during development when you don't want to run a web server like Apache.

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

> By default CGI support is disabled in Tomcat.

> Note that the CGI Servlet requires a 1.3 or later JDK.

Installation

> CAUTION - 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 `catalina.policy.`

> Rename `$CATALINA_BASE/server/lib/servlets-cgi.renametojar` to `$CATALINA_BASE/server/lib/servlets-cgi.jar`.

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

Configuration

> There are several servlet init parameters which can be used to configure the behaviour of the CGI servlet.

> - cgiPathPrefix - The CGI search path will start at the web application root directory + File.separator + this prefix. The default cgiPathPrefix is `/WEB-INF/cgi`
> - debug - Debugging detail level for messages logged by this servlet. Default 0.
> - executable - The of the executable to be used to run the script. Default is `perl`.
> - passShellEnvironment - Should the shell environment variables (if any) be passed to the CGI script? Default is `false`.

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