Common Gateway Interface

World-Wide Web (CGI) A standard for running external

programs from a World-Wide Web HTTP server. CGI

specifies how to pass arguments to the executing program as

part of the HTTP request. It also defines a set of

environment variables. Commonly, the program will generate

some HTML which will be passed back to the browser but it

can also request URL redirection.

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. A CGI program can be any program

which can accept command line arguments. Perl is a common

choice for writing CGI scripts. 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.

Whenever the server receives a CGI execution request it

creates a new process to run the external program. If the

process fails to terminate for some reason, or if requests are

received faster than the server can respond to them, the

server may become swamped with processes.

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 main server process, thus

avoiding the overhead of creating a new process to handle each

CGI invocation.

Current version: 1.1.

NCSA .

(2002-06-03)