CGI(Common Gateway Interface)

CGI(Common Gateway Interface)

•       "CGI" stands for "Common Gateway Interface." CGI is one method by which a web server can obtain data from (or send data to) databases, documents, and other programs, and presents that data to viewers via the web. More simply, a CGI is a program intended to be run on the web. A CGI program can be written in any programming language, but Perl is one of the most popular languages

•       CGI is a standard for interfacing external applications with information servers, such as HTTP or Web servers

•       This interface provides a means for browsers and the server where document resides to communicate and pass information back and forth

•       Primarily, this is done through the <FORM> tag, but there can be other ways to use CGI effectively, like through Server Side Includes (SSI)

•       CGI, permits interactivity between a client and a host operating system through the World Wide Web via the Hyper Text Transfer Protocol (HTTP)

•       CGI program can be written in C or C++, Perl, ASP, PHP, Python, TCL, shells, and many others languages and scripts

Examples of uses for CGI:

•       Forms

forms on web sites allow the user to enter information which is processed by CGI and mailed to an administrator or logged

On-the-Fly Pages web pages can be created dynamically (as needed) with up-to-date nformation.

•       Database Interaction

an application of on-the-fly page creation. Web pages can be created using information read from a database, or a web site form can allow a user to update database entries

•       Logging / Counters

a log file can record traffic data updated with information on each visitor. A counter can be included on the web page to advertise traffic.

•       Animation

"server-push" programs can be used to feed the client successive images in an animated sequence.

•       Catalogs, Search engines

CGI programs

•       Obtaining input from a user or from a data file.

•       Storing that input in program variables.

•       Manipulating those variables to achieve some desired purpose, and

•       Sending the results to a file or video display.