CGI library for C++ Document 【English】

C++ CGI Library [English]

This library provides a simple interface for creating CGI (Common Gateway Interface) applications in C++. It enables the handling of GET and POST requests, parsing query strings and POST data, and managing session IDs.


  • Parse Query String: Easily parse query strings from GET requests into a std::mapor convenient access to parameters.
  • Parse POST Data: Handle POST request data, parsing it into a std::mapor easy parameter retrieval.
  • Session Management: Generate and manage session IDs to maintain session state across requests.

Request Handling: Retrieve values from either GET or POST requests based on the current request method.

About the source code

CGI Class Description

This CGI class is written in C++ and offers basic CGI (Common Gateway Interface) processing capabilities for web applications. By using this class, you can easily handle GET or POST requests from web forms and manage session IDs. Below is an overview of each method in the class.

  • CGI(): Automatically generates a session ID when an instance of the class is created.
  • parseQueryString(): Parses GET parameters from the URL's query string and returns them in a std::map<std::string, std::string>ormat, allowing access to query parameters as key-value pairs.
  • parse_post_data(): Reads POST data from the standard input and returns it in a similar `std::map<std::string, std::string>` format.
  • POST_(std::string param): Retrieves the value of a specified POST parameter. Undefined behavior if the parameter does not exist.
  • GET_(std::string param): Retrieves the value of a specified GET parameter. Returns an empty string if the parameter does not exist.
  • REQUEST_(std::string param): Determines whether the request is a GET or POST using the `REQUESTTHOD` environment variable and retrieves the parameter value accordingly.
  • GenerateSessionId(): Randomly generates a session ID. This ID serves as a consistent identifier for a user throughout their visit to the site.
  • SESSION_ID(): Retrieves the current session ID.

Usage Example

This class is useful for handling user input and managing sessions in web applications. For instance, when a user submits information through a form, this class can be used to parse and process the data. Additionally, the session ID can be used to identify a user's session for authentication or state management purposes.

Compilation Guide

To compile a C++ program that includes the CGI class, you need a C++ compiler such as g++ or clang++. Here is a basic example of how to compile a program with g++:

  1. Save your program that includes the CGI class to a file, for example, main.cpp.
  2. Open your terminal or command prompt.
  3. Navigate to the directory where main.cpp is located.
  4. Compile the program using the following command:
g++ main.cpp -std=c++11 -o ./cgi/main.cgi

This command tells `g++` to compile `main.cpp` and output an executable named `./cgi/main.cgi`.


- The `parse_post_data()` method uses `std::cin` to read POST data, so it only works in a CGI environment.
- The `POST_` method can result in undefined behavior if the key is not found, so it's important to either verify the key's existence beforehand or implement proper exception handling in actual use.
- The `SESSION_ID` method only returns the value if the session ID is not empty, but it's unlikely to encounter a situation where a session ID has not been generated.

This class provides a foundation for developing CGI-based web applications in C++, making it easier to process form data and manage sessions.


Including the Library

Include the CGI library in your project by adding `#include "CGI.h"` to your source file.

Creating an Instance

Instantiate the CGI class in your application to start using its features.

CGI cgi;

Handling Requests

Retrieve a specific parameter value from either GET or POST requests:

std::string value = cgi.REQUEST_("paramName");

Session ID

Retrieve the current session ID:

std::string sessionId = cgi.SESSION_ID();


Contributions to the CGI library are welcome. Please ensure that your code adheres to the project's coding standards and include unit tests for new features or bug fixes.


This library is open-source and licensed under MIT License. Feel free to use it in your projects as per the license agreement.




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