README.md

Differences between the ROS2 logger and standard println!()

The ROS2 logger and classic stdout (e.g., println!) differ in several key ways:

1. Severity Levels:
   ROS2 provides structured log levels (DEBUG, INFO, WARN, ERROR, FATAL), enabling filtering based on urgency. println! outputs raw text without categorization.

2. Dynamic Control:
   ROS2 allows runtime adjustment of logging levels (e.g., enabling DEBUG on-the-fly). println! statements cannot be disabled without code changes.

3. Metadata:
   ROS2 automatically appends context (timestamp, node name, file/line number) to logs. println! requires manual addition of such details.

4. Integration:
   ROS2 logs are captured by tools like rqt_console and can be routed to files/network. println! outputs only to stdout unless manually redirected.

5. Performance:
   ROS2 optimizes by skipping disabled log levels (e.g., DEBUG if not active). println! always executes, incurring overhead regardless of need.

6. Configuration:
   ROS2 logging is configurable via launch files/parameters (e.g., per-node log levels). println! offers no built-in configuration.

Example:

// ROS2 logger (Rust example with rclrs)
log!(node.info(), "Sensor value: {}", sensor_data);  // Adds metadata, severity, and runtime control

// Classic stdout
println!("Sensor value: {}", sensor_data);  // Simple, unstructured output

Use ROS2 logger for structured, controllable logging within the ROS2 ecosystem; use println! for quick, simple text output.