Read and Change Parameters

The beginner parameter tutorial calls parameters node settings.

Each node maintains its own parameters.

List parameters

With Turtlesim and teleop running:

ros2 param list

You should see parameter names grouped under nodes.

Read a value

The official tutorial uses:

ros2 param get /turtlesim background_g

The output reports both the parameter type and current value.

Change a value

Try:

ros2 param set /turtlesim background_r 150

The Turtlesim background should change.

Important boundary

You changed runtime configuration.

You did not edit Turtlesim source code or rebuild the package.

That distinction is why parameters are useful.

Inspect before/after

Run:

ros2 param get /turtlesim background_r

before and after your set operation.

Checkpoint

Explain the difference between:

• changing a topic message;
• calling a service;
• setting a parameter.

Use the Turtlesim examples you actually ran.