Starting Nodes

Environment Configuration

Every time you open a new shell, before using any ROS2 command, you must source the setup files first:

 source /opt/ros/jazzy/setup.bash

If you don’t want to do this every time you open a new shell, you need to add the source command to your shell startup script:

 echo "source /opt/ros/jazzy/setup.bash" >> ~/.bashrc”

Runing Nodes

A node isn't really much more than an executable executable file from a package. ros2 run allows you to use the package name to directly run a node within a package (without having to know the package path).

Usage:

 ros2 run [package_name] [executable_name]

Starting Turtlesim

According to the ROS2 website, "Turtlesim is a lightweight simulator for learning ROS 2. It illustrates what ROS 2 does at the most basic level to give you an idea of what you will do with a real robot or a robot simulation later on."

We can now run the turtlesim node in the turtlesim package. In a new terminal, we start turtlesim with:

 ros2 run turtlesim turtlesim_node

You will see the turtlesim window (your turtle could look different but that's okay):

Renaming Nodes

Sometimes, you might want to give nodes a new name. Through remapping, you can change default node properties, including node names.

For example, we can rename the turtlesim node with:

 ros2 run turtlesim turtlesim_node --ros-args --remap __node:=[new_name]

Tab Completion

NOTE: If you're using Zsh instead of Bash, see here.

It can get tedious to type out an entire package or excutable name. For example, turtle_teleop_key is a fairly long name. Luckily, some ROS2 tools support TAB completion.

Start by typing:

 ros2 run tu<now push the TAB key>

After pushing the TAB key, the command line should fill out the rest: turtlesim. This works because turtlesim is currently the only ROS2 package that starts with "tu".

Now try typing:

 ros2 run turtlesim t<now push the TAB key>

In this case, we have two excutable names that start with "turtle". The TAB key won't fill out the exutable name for us but should fill out the command line as much as possible:

ros2 run turtlesim turtle

Try typing TAB twice and all the possible names should be listed:

 ros2 run turtlesim turtle<now push the TAB key TWICE>

This should display all the ROS2 excutables in the turtlesim package that begin with "turtle":

 turtlesim_node     turtle_teleop_key  

On the command line you should still have:

 ros2 run turtlesim turtle

After adding an "_" after the name "turtle", press TAB again:

 ros2 run turtlesim turtle_<now push the TAB key>

There is only one excutable that starts with "turtle_" so you should see:

 ros2 run turtlesim turtle_teleop_key

Review

• ros2 run [package_name] [executable_name]: run a node from a given package