Checking the roscore command output

Let's check the ROS topics and ROS parameters created after running roscore. The following command will list the active topics on the Terminal:

$ rostopic list  

The list of topics is as follows, as per our discussion on the rosout node subscribe /rosout topic. This has all the log messages from the ROS nodes and /rosout_agg will rebroadcast the log messages:

/rosout
/rosout_agg  

The following command lists the parameters available when running roscore. The following is the command to list the active ROS parameter:

$ rosparam list  

The parameters are mentioned here; they have the ROS distribution name, version, address of the roslaunch server and run_id, where run_id is a unique ID associated with a particular run of roscore:

/rosdistro
/roslaunch/uris/host_robot_virtualbox__51189
/rosversion
/run_id

The list of the ROS service generated during the running roscore can be checked using the following command:

$ rosservice list  

The list of services running is as follows:

/rosout/get_loggers
/rosout/set_logger_level  

These ROS services are generated for each ROS node for setting the logging levels.