Run Turtlesim

Now that you’ve added ROS’ environment variables to your terminal session, you can run the turtlesim package!

Starting the Master process

Before you can run any ROS nodes, you must start the Master process.

The Master process is responsible for the following (and more):

• Providing naming and registration services to other running nodes
• Tracking all publishers and subscribers
• Aggregating log messages generated by the nodes
• Facilitating connections between nodes

To run the master process, execute the command
sh roscore
If all goes well (and it should), you will see output similar to this:

This indicates that ROS Master is running! To terminate the ROS Master process, you can simply send the SIGINT signal to the process by pressing ctrl-c in the roscore terminal window.

We are now ready to begin launching nodes!

Running Turtlesim Nodes

Now that the ROS Master is running, we can run our first two ROS nodes.

To do so, we will execute the rosrun command in a new terminal window, passing as parameters the name of the package we wish to run, and the name of the actual node.

Note

You can open a second instance of you current terminal using CTRL + SHIFT + T .

Tab completion is your friend. Each ROS distribution comes with a staggering number of packages, and an even more staggering number of nodes. In the bash shell, a single-tap of the tab key will autocomplete the command, if there is a single match. A double-tap of the tab key will result in a list of all possible matches, in the case that a single match cannot be found.

First we will start the turtlesim_node , in the turtlesim package using the following command in a second terminal instance.

$ rosrun turtlesim turtlesim_node

Next, we will start the turtle_teleop_key node , also from the turtlesim package in a third terminal instance.

$ rosrun turtlesim turtle_teleop_key

By using the arrow keys with the turtle_teleop_key node’s console selected, we are able to move the turtle in turtlesim!