CGI stands for common gateway interface. It is an interface that enables the web server to process a user’s HTTPS request by executing a program. It executes a program that resides on the server to process data to produce the relevant dynamic content. When a client gives a request or input, this data is passed to the CGI script as an environment variable, and then the CGI script processes the request and generates dynamic content for the user’s input. Once the web server receives the output generated by CGI, it sends the response to the client.
CGI programs are called scripts which are written in many popular languages like Python, PHP, Ruby, etc that interact with a web server to process user input. CGI scripts are stored in a directory which varies depending on server configuration but usually, it resides in a special type of directory in a web server called cgi-bin.
History of CGI
- CGI was developed as a standard that can be used to generate dynamic content and to establish communication between server and client.
- It was written and developed in 1993 by the National Center for Supercomputer Applications.
- Ever since it was developed it made it easy for the sever-client connection to communicate directly through CGI.
- It was widely accepted all over the world but after few years many alternatives were developed which are better than CGI.
- CGI scripts and program can be written with most of the language that made it widely acceptable.
Working of CGI in Web Development
- The process starts with creating program or writing CGI scripts which can process the users request and react to it by giving required output. To access CGI script we can write URL like (http://abc.com/cgi-bin/).
- Configure your web server so that it can recognize the directories in which the CGI scripts are present. CGI scripts are stored in different directories depending on server configuration.
- In the case when a user or web browser gives request to a URL or a file in the database within the CGI directory, the HTTP server runs that specific script and passes the output of the script to web browser.
- The CGI script retrieves the source of that entry’s page and transforms it into HTML to give output.
- The web server creates a set of environment variables that contain information about the a particular request. If there exist additional directory names in the URL written after the script’s name like( __/with/additional/path) then this information is stored in an environment variable called PATH_INFO.
- There are two types of method in which the web browser communicate with web server popularly known as GET and POST.
- If in case the request uses the GET method then the data is transferred from web browser to web sever using GET method. The data transferred using this method is not secure as it can be easily visible to anyone.
- If request can also use the POST method to send data and it is a secure method to transfer data.
- This is how CGI help in the process of web communication with the server and plays a major role in web development. Although there are many new technologies have been introduced in past recently which are fast and more secure but CGI has its own importance in the history of web development.
Role of CGI in Web Development
Python CGI (Common Gateway Interface) plays a significant role in web development by enabling the execution of Python scripts on a web server to generate dynamic web content. Here are some key aspects of the role of Python CGI in web development:
- Dynamic Content Generation: CGI allows the creation of dynamic web pages by executing Python scripts on the server in response to user requests. This is in contrast to static web pages, which remain the same each time they are loaded.
- Interactivity: With CGI, Python scripts can interact with the user, process form data, and generate customized content based on user input. This interaction is crucial for creating dynamic and responsive web applications.
- Form Handling: CGI scripts are commonly used to handle HTML forms submitted by users. The data from these forms is sent to the server, processed by the Python script, and the script generates a response based on the form data.
- Server-Side Scripting: Python CGI allows for server-side scripting, where the script is executed on the server before the results are sent to the user’s web browser. This is different from client-side scripting, where scripts run on the user’s browser.
- Integration with Web Servers: CGI is supported by most web servers, making it a versatile choice for running Python scripts. Popular web servers like Apache, Nginx, and others can be configured to execute CGI scripts in response to specific URL requests.
- Data Processing: CGI scripts can be used for processing and managing data on the server side. This includes tasks such as database access, file manipulation, and other server-side operations.
- Scalability: While CGI is a simple and widely supported way to run scripts on a web server, it may not be as efficient or scalable as more modern approaches like FastCGI, WSGI (Web Server Gateway Interface), or application frameworks (e.g., Flask, Django). These alternatives are often preferred for larger and more complex web applications.
Environment Variables Used in CGI
- CONTENT_LENGTH : It specifies the length of URL encoded data in bytes.
- REMOTE_HOST : resolved host name of the client.
- CONTENT_TYPE : It specifies the type of data as a MIME header.
- QUERY_STRING : Gives information at the end of the URL after ?
- REMOTE_ADDR : IP address of the client making the request.
- REQUEST_METHOD: It gives the HTTP request method(GET or POST ).
- SCRIPT_NAME : Name of the CGI script which is being run.
Advantages of CGI
- It is easy to develop a CGI program and deploy to process users request.
- It helps in creating a connection between web server and web browser.
- They can be used to generate dynamic web content.
- CGI can be programed by using almost any language.
- It has access to multiple environment variables support.
Disadvantages of CGI
- It is slow while giving multiple output when user requests are very large. It eventually reduces the speed of the process.
- CGI scripts are not secure and vulnerable to attacks. Which may leads to disclosure of sensitive information.
- Do not have its own pre defined frameworks.