What Does 'CGI (Common Gateway Interface)' Mean?

CGI (Common Gateway Interface) is a standard protocol for executing scripts or programs over the Internet. It allows a server to run scripts or programs in response to requests from clients, such as web browsers.

The CGI protocol is commonly used to execute programs that generate dynamic content for websites. For example, a CGI program might be used to search a database and return the results to a user or to generate a custom form or page based on user input.

To understand how CGI works, it’s helpful to know how a typical web server operates. When a user enters a URL into a web browser, the browser sends a request to the web server to retrieve the specified resource.

If the resource is a static file, such as an HTML page or an image, the server simply sends the file back to the browser. But if the resource is a script or program, the server runs the script or program and sends the output back to the browser.

This is where CGI comes in. The CGI protocol specifies how the server and the script or program communicate with each other. When a user requests a resource that is a script or program, the server runs the script or program and passes any necessary information to it via environmental variables and standard input and output streams.

The script or program then processes this information and generates output, which it sends back to the server. The server then sends the output to the user’s web browser.

More information

There are several ways to execute CGI programs or scripts on a server. One common method is to use a CGI wrapper, which is a program that runs other programs or scripts and handles the communication between the server and the script or program.

Another method is to use a server module, which is a piece of software that is integrated into the web server and can execute CGI programs or scripts directly.

CGI has been around for a long time and is still widely used, but it has some limitations. For example, CGI programs or scripts are executed each time a user requests a resource, which can be resource-intensive and slow. There are also security concerns, as CGI programs or scripts can potentially be exploited by malicious users.

As a result, newer technologies such as FastCGI and mod_perl have been developed to address these issues and improve the performance and security of CGI.

In summary, CGI is a protocol for executing scripts or programs on a web server in response to requests from clients. It allows for the creation of dynamic content on websites and has been widely used for many years, but newer technologies have been developed to address its limitations.