Writing Your First ROS 2 Node¶

Goal¶

Create a minimal C++ node that:

Initializes the ROS 2 client library.
Creates a node object.
Spins until shut down.

Minimal C++ Node¶

#include "rclcpp/rclcpp.hpp"

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);

  auto node = std::make_shared<rclcpp::Node>("minimal_node");

  RCLCPP_INFO(node->get_logger(), "Node has been started.");

  rclcpp::spin(node);
  rclcpp::shutdown();
  return 0;
}

Key Points¶

rclcpp::init
- Initializes the ROS 2 system with command-line arguments.
rclcpp::Node
- Represents a ROS 2 node.
- Takes a node name such as "minimal_node".
rclcpp::spin
- Enters a loop that processes callbacks (timers, subscriptions, etc.).
- Keeps the node alive until interrupted (Ctrl+C).
rclcpp::shutdown
- Cleans up ROS 2 resources before exiting.

CMake Integration¶

In the package’s CMakeLists.txt, you typically:

Find rclcpp.
Add an executable.
Link the target against rclcpp.

find_package(rclcpp REQUIRED)

add_executable(minimal_node src/minimal_node.cpp)
ament_target_dependencies(minimal_node rclcpp)

install(TARGETS
  minimal_node
  DESTINATION lib/${PROJECT_NAME})

After building with colcon build and sourcing the workspace:

ros2 run my_package minimal_node