CGI

C ommon G ateway I nterface is one of the most popular UNIX-based programs/devices that supply interfaces between browsers and servers on the Internet. A standard for running external programs from a World-Wide Web HTTP server. CGI specifies how to pass dynamic components to the executing program as part of the HTTP request. For example, it will allow answers typed into an HTML form on the client computer to be tabulated and stored in a database on the server-side computer. Commonly, the server-side CGI program will generate some HTML which will be passed back to the client's browser. For example, it might report to the client user that the form is not filled out properly or report the invoice total of an order. CGI allows the returned HTML (or other document type) to depend in any arbitrary way on the request. The CGI program can, for example, access information in a database and format the results as HTML. CGI is not a programming language. There are various "CGI" scripting programs. Perl is a common choice for writing CGI scripts. in UNIX code. Some HTTP servers require CGI programs to reside in a special directory, often "/cgi-bin" but better servers provide ways to distinguish CGI programs so they can be kept in the same directories as the HTML files to which they are related. In order to improve performance, Netscape devised NSAPI and Microsoft developed the ISAPI standard which allow CGI-like tasks to run as part of the host server process, thus avoiding the overhead of creating a new process to handle each CGI invocation.