ROS System Command Line Study Notes

Common ROS Commands#

Here are some commands that are frequently used during ROS development:

1. Start ROS Core#

Before using ROS, you need to start a core service called roscore. Enter the following command in a new terminal:

roscore

2. Start a Node#

A ROS node is an executable file that processes and handles data. The following command will start a node named turtlesim:

rosrun turtlesim turtlesim_node

3. View Node List#

Use the following command to view all currently running nodes:

rosnode list

4. View Topic List#

ROS topics are channels used for communication between nodes. The following command will display all currently available topics:

rostopic list

5. View Service List#

ROS services are a form of synchronous communication between nodes. The following command will list all currently available services:

rosservice list

This note introduces the basic usage of ROS 1 command line. In practical operations, you will also need to learn more advanced features and commands to better master ROS 1 and complete complex robotic projects. Here are some commonly used advanced features and commands:

6. Parameter Server#

The ROS parameter server is a centralized database for storing and managing global parameters. These parameters can be modified at runtime and shared among various nodes.

View Parameter List#

To view all parameters currently stored on the parameter server, use the following command:

rosparam list

Get Parameter Value#

To get the value of a specific parameter, use the following command:

rosparam get <parameter_name>

Set Parameter Value#

To set the value of a specific parameter, use the following command:

rosparam set <parameter_name> <value>

7. ROS Messages#

ROS messages are the basic units of information passed between different nodes in the ROS system. Messages consist of a set of data structures that define different types of data.

View Message Type#

To view the message type on a specific topic, use the following command:

rostopic type <topic_name>

View Message Structure#

To view the detailed structure of a specific message type, use the following command:

rosmsg show <message_type>

8. Use Launch Files to Start Multiple Nodes#

ROS .launch files allow you to start multiple nodes at once. This is very useful for starting multiple interdependent nodes simultaneously.

Create Launch File#

First, create a directory named launch in your package and create an XML file named my_launch_file.launch within it:

mkdir -p ~/my_workspace/src/my_package/launch
touch ~/my_workspace/src/my_package/launch/my_launch_file.launch

Then, edit the my_launch_file.launch file and add the following content:

<launch>
  <node pkg="turtlesim" type="turtlesim_node" name="turtlesim"/>
  <node pkg="turtlesim" type="turtle_teleop_key" name="teleop" output="screen"/>
</launch>

Start Launch File#

To start the my_launch_file.launch file, use the following command:

roslaunch my_package my_launch_file.launch

9. Use Rosbag to Record and Playback Data#

rosbag is a tool for recording and playing back ROS topic data. This is very useful for offline analysis and testing.

Record Data#

To record data from a specific topic, use the following command:

rosbag record -o <output_file> <topic_name>

Playback Data#

To playback recorded data, use the following command:

rosbag play <bag_file>

By learning these advanced features and commands, you will be able to better master ROS 1 and successfully apply it in various complex robotic projects.