Common Gateway Interface
The Common Gateway Interface (CGI) is a set of rules for running scripts and programs on a Web server. It specifies what information is communicated between the Web server and clients' Web browsers and how the information is transmitted.
Most Web servers include a cgi-bin directory in the root folder of each website on the server. Any scripts placed in this directory must follow the rules of the Common Gateway Interface. For example, scripts located in the cgi-bin directory may be given executable permissions, while files outside the directory may not be allowed to be executed. A CGI script may also request CGI environment variables, such as
SERVER_PROTOCOL and REMOTE_HOST, which may be used as input variables for the script.