What is CGI?
CGI stands for Common Gateway Interface. It is a standard protocol that enables web servers to execute programs or scripts, generating dynamic content to be displayed on a website. CGI acts as a bridge between the web server and executable programs, allowing web pages to interact with external functionality such as databases or file systems.
Mechanism of Running Programs on a Web Server
When a web server receives a request for a web page that requires dynamic content, it passes the request to the CGI program. The CGI program can be written in various programming languages such as Perl, Python, or PHP. The process of running programs on a web server involves the following steps:
1. Web Server Receives the Request:
When a user requests a web page that requires dynamic content, the web server receives the request and determines that it needs to execute a CGI program.
2. Web Server Identifies the CGI Program:
The web server identifies the CGI program associated with the requested web page based on the file extension or other configuration settings.
3. Passing Request Data to CGI Program:
The web server passes the request data, such as form inputs or URL parameters, to the CGI program. This data is usually provided as environment variables or command-line arguments.
4. CGI Program Processing:
The CGI program receives the request data and processes it accordingly. It can perform various operations, such as retrieving data from databases, generating dynamic content, or interacting with other external services.
5. CGI Program Generates Response:
After processing the request data, the CGI program generates a response, typically in the form of HTML content. This response is sent back to the web server.
6. Web Server Sends Response to the User:
The web server receives the response from the CGI program and sends it back to the user’s web browser as the dynamically generated web page.
Overall, CGI offers a flexible mechanism for running programs on a web server, making it possible to create dynamic and interactive web applications. However, due to its resource-intensive nature, other technologies like FastCGI or server-side scripting languages are often preferred for larger-scale applications.
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