This tutorial introduces ROS topics as well as using the rostopic
commandline tools.
Before we move forward, let's start by making sure that we have roscore running, in a new terminal:
$ roscore
If you left roscore running from the last tutorial, you may get the error message:
roscore cannot run as another roscore/master is already running.
Please kill other roscore/master processes before relaunching
This is fine. Only one roscore needs to be running.
The rostopic
tool allows you to get information about ROS topics.
You can use the help option to get the available sub-commands for rostopic
root@erlerobot:~# rostopic -h
rostopic is a command-line tool for printing information about ROS Topics.
Commands:
rostopic bw display bandwidth used by topic
rostopic echo print messages to screen
rostopic find find topics by type
rostopic hz display publishing rate of topic
rostopic info print information about active topic
rostopic list list active topics
rostopic pub publish data to topic
rostopic type print topic type
Type rostopic <command> -h for more detailed usage, e.g. 'rostopic echo -h'