Common gateway interface (CGI)

A common gateway interface (CGI) is a standard for external gateway programs to interface with information servers such as HTTP servers. A CGI program is any program that can be executed by a web server as a result of a client request. Typically, CGI programs are written in a scripting language such as Perl, Python, or Tcl.

CGI programs can be written in any language that can be executed by the server. When a client request arrives for a resource that is mapped to a CGI program, the server executes the program and returns the program's output to the client.

The common gateway interface provides a way for web servers to interact with executable files on the server machine. This enables the web server to run programs that generate dynamic content, which can be used to create web pages that are customized for each user.

CGI programs can be used to create web pages that contain information that is retrieved from a database, or to provide a form-based interface to a database. CGI programs can also be used to implement simple web-based applications.

How does CGI Common Gateway Interface work?

The Common Gateway Interface (CGI) is a standard for interfacing external applications with web servers. CGI scripts are typically used to generate dynamic web content, such as dynamic HTML pages or images based on database information.

When a web server receives a request for a CGI script, it invokes the script with the following environment variables set:

SERVER_NAME: The name of the server.

SERVER_PORT: The port number on which the server is listening.

SERVER_SOFTWARE: The name and version of the server software.

REQUEST_METHOD: The HTTP request method used to access the CGI script.

PATH_INFO: The path to the CGI script, relative to the server's document root.

QUERY_STRING: The query string, if any, included in the HTTP request.

REMOTE_ADDR: The IP address of the client making the request.

REMOTE_HOST: The hostname of the client making the request, if available.

A CGI script typically reads these environment variables and uses them to generate the appropriate output. For example, a script might use the REMOTE_ADDR variable to personalize the output for the user making the request.

CGI scripts can be written in any programming language, but Perl is the most popular choice. Can PHP be used as a CGI? Yes, PHP can be used as a CGI, but it is not recommended. PHP is designed to be run as an Apache module or as a command-line interface (CLI), and as a result, it is not as efficient when run as a CGI. Is CGI bin still used? The answer is yes, CGI bin is still used. It is a directory on a web server that is used to store executable files that can be run by the server. These files are usually scripts written in a scripting language like Perl or PHP. Why is CGI required? CGI is required in order to run web-based applications written in programming languages such as Perl, Ruby, and Python. CGI stands for "Common Gateway Interface", and is a standard way for a web server to interface with web-based applications.

Why do we need CGI?

CGI stands for Common Gateway Interface. It is a standard way for a web server to interact with external programs, usually for the purpose of generating dynamic web pages.

CGI is used for a wide range of tasks, such as creating online forms, generating reports, and powering e-commerce applications. CGI programs can be written in any programming language, although Perl is the most popular choice.