<p>CUPS provides a dynamic web interface through dedicated CGI programs that are executed when users open special directories on the CUPS server. Each CGI performs administration, class, help, job, and printer functions as directed by the user, but the actual programs that are run and functions that are available are limited to those that were originally designed into the scheduler.</p>
<p>CUPS also supports CGI scripts/programs for pages you want to provide, although this functionality is disabled by default. The "application/x-httpd-cgi" MIME media type is used to identify CGI content and can be associated with any filename extension. The scheduler requires CGI content to have the execute bit set, not have world or group write permissions, and any CGI scripts need to include a <tt>#!</tt> line as the first line of a script to identify the script interpreter. For example, a PHP script would look like:</p>
<p>In order to enable the corresponding type, you must create a new <var>/etc/cups/cgi.types</var> file which maps the filename extensions you use to the appropriate MIME types. For example, the following will support CGI programs/scripts with the "cgi" extension:</p>
<li>Limited HTTP field support; only the Content-Length (<tt>CONTENT_LENGTH</tt>), Content-Type (<tt>CONTENT_TYPE</tt>), Cookie (<tt>HTTP_COOKIE</tt>), Referrer (<tt>HTTP_REFERRER</tt>), and User-Agent (<tt>HTTP_USER_AGENT</tt>) fields are placed in environment variables at this time</li>
