Working with YAML in C++: yaml-cpp library for parsing and serialization

Working with YAML in C++: the yaml-cpp library

YAML (YAML Ain't Markup Language) is a human-readable data serialization format that is often used for configuration files, data exchange, and storing structured information. In C++, there is a powerful and easy-to-use library yaml-cpp for working with YAML. In this article, we will take a detailed look at how to install, configure, and use yaml-cpp for parsing and creating YAML documents.

Installing yaml-cpp

The yaml-cpp library is available for most platforms. The easiest way to install it is via a package manager:

• Ubuntu/Debian: sudo apt-get install libyaml-cpp-dev
• macOS (Homebrew): brew install yaml-cpp
• Windows (vcpkg): vcpkg install yaml-cpp

You can also build it from source by cloning the repository from GitHub and using CMake:

git clone https://github.com/jbeder/yaml-cpp.gitcd yaml-cppmkdir build && cd buildcmake ..makesudo make install

Basics of working with yaml-cpp

The library provides an intuitive API for loading, modifying, and saving YAML data. All data types are stored in the YAML::Node container, which can be a scalar, a sequence (array), or a mapping (dictionary).

Example YAML file

Consider the following configuration file config.yaml:

database:  host: localhost  port: 5432  name: myapp  credentials:    user: admin    password: secret123

server:  workers: 4  timeout: 30.5  debug: true

allowed_ips:  - 192.168.0.1  - 192.168.0.2  - 10.0.0.1

Parsing a YAML file

To load data from a file, the YAML::LoadFile() function is used:

#include <yaml-cpp/yaml.h>#include <iostream>#include <string>#include <vector>

int main() {    try {        // Load the YAML file        YAML::Node config = YAML::LoadFile("config.yaml");

        // Access nested data using the [] operator        std::string host = config["database"]["host"].as<std::string>();        int port = config["database"]["port"].as<int>();        std::string user = config["database"]["credentials"]["user"].as<std::string>();

        std::cout << "Database host: " << host << std::endl;        std::cout << "Database port: " << port << std::endl;        std::cout << "User: " << user << std::endl;

        // Working with a sequence (list)        YAML::Node ips = config["allowed_ips"];        std::vector<std::string> ipList;        for (const auto& ip : ips) {            ipList.push_back(ip.as<std::string>());        }

        std::cout << "Allowed IPs: ";        for (const auto& ip : ipList) {            std::cout << ip << " ";        }        std::cout << std::endl;

    } catch (const YAML::Exception& e) {        std::cerr << "YAML Error: " << e.what() << std::endl;        return 1;    }

    return 0;}

Creating and serializing YAML

yaml-cpp also allows you to create YAML documents programmatically and save them to a file:

#include <yaml-cpp/yaml.h>#include <fstream>

int main() {    // Create a root node    YAML::Node config;

    // Add data    config["application"]["name"] = "MyApp";    config["application"]["version"] = 2.1;    config["application"]["debug"] = false;

    // Create a sequence    config["features"].push_back("logging");    config["features"].push_back("caching");    config["features"].push_back("auth");

    // In