The message data in ROS topics are stored in log files called ROS bag files or rosbags. You can use MATLAB^® functions, apps and Simulink^® blocks to access, filter and execute offline analysis of ROS data in these rosbag files. These bags are often created by subscribing to one or more ROS topics, and storing the received message data in an efficient file structure. For an example of working with rosbags, see Work with rosbag Logfiles.

ROS toolbox also allows access to the message data in ROS 2 bag files or ros2bags. You can filter the ROS 2 data and execute offline analysis in these ros2bag files.

Use rosbagreader to extract message data from a rosbag and rosbagwriter to create a rosbag log file and write logs to it. You can also use the ROS Logger app to record ROS messages during Simulink simulation. For more information, see Use ROS Logger App to Save ROS Messages from Simulink.

To extract massage data from a ros2bag log file, use the ros2bagreader object. To write logs to a ros2bag log file, use the ros2bagwriter object. You can also record ROS 2 messages during a Simulink simulation by using the ROS 2 Logger app. For more information, see Use ROS 2 Logger App to Save ROS 2 Messages from Simulink.

To visualize the messages in a ROS or ROS 2 bag log file, use ROS Bag Viewer app.