Generate custom messages from ROS 2 definitions


ros2genmsg(folderpath) generates MATLAB® interfaces to ROS 2 custom messages. Specify the path to the parent folder that contains the definitions of the custom messages as .msg files.


ros2genmsg(folderpath,Name,Value) specifies additional options using one or more name-value pair arguments.


When generating custom messages for ROS 2, you must build the ROS packages. This requires you to have CMake and a C++ compiler for your platform. For more information, see ROS System Requirements

You must have the following installed on your system:


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Custom messages are user-defined messages that you can use to extend the set of message types currently supported in ROS 2. If you are sending and receiving supported message types, you do not need to use custom messages. To see a list of supported message types, call ros2 msg list in the MATLAB® Command Window. For more information about supported ROS 2 messages, see Work with Basic ROS 2 Messages.

If this if your first time working with ROS 2 custom messages, check the ROS System Requirements.

Custom messages Contents

ROS 2 custom messages are specified in ROS 2 package folders that contain a msg directory. The msg folder contains all your custom message type definitions. For example, the package example_b_msgs, within the custom folder, has the below folder and file structure.

The package contains one custom message type, Standalone.msg. MATLAB uses these files to generate the necessary files for using the custom messages contained in the package. For more information on message naming conventions, see ROS 2 Interface Definition.

In this example, you go through the procedure for creating ROS 2 custom messages in MATLAB®. You must have a ROS 2 package that contains the required msg file.

After ensuring that your custom message package is correct, note the folder path location, and then, call ros2genmsg with the specified path. The following example provided three messages example_package_a, example_package_b, and example_package_c that have dependencies. This example also illustrates that you can use a folder containing multiple messages and generate them all at the same time.

To set up custom messages in MATLAB, open MATLAB in a new session. Place your custom message folder in a location and note the folder path. In this example, the custom message interface folder is present in the current directory. If you are creating custom message packages in a separate location, provide the appropriate path to the folder that contains the custom message packages.

folderPath = fullfile(pwd,"custom");

Specify the folder path for custom message files and call ros2genmsg to create custom messages for MATLAB.

Identifying message files in folder 'U:/Documents/MATLAB/Examples/ros-ex44405863/custom'.Done.
Validating message files in folder 'U:/Documents/MATLAB/Examples/ros-ex44405863/custom'.Done.
[3/3] Generating MATLAB interfaces for custom message packages... Done.
Running colcon build in folder 'U:/Documents/MATLAB/Examples/ros-ex44405863/custom/matlab_msg_gen/win64'.
Build in progress. This may take several minutes...
Build log

Call ros2 msg list to verify creation of new custom messages.

You can now use the above created custom message as the standard messages. For more information on sending and receiving messages, see Exchange Data with ROS 2 Publishers and Subscribers.

Create a publisher to use example_package_b/Standalone message.

node = ros2node("/node_1");
pub = ros2publisher(node,"/example_topic","example_b_msgs/Standalone");

Create a subscriber on the same topic.

sub = ros2subscriber(node,"/example_topic");

Create a message and send the message.

custom_msg = ros2message("example_b_msgs/Standalone");
custom_msg.int_property = uint32(12);
custom_msg.string_property='This is ROS 2 custom message example';
pause(3)    % Allow a few seconds for the message to arrive

Use LatestMessage field to know the recent message received by the subscriber.

ans = struct with fields:
       int_property: 12
    string_property: 'This is ROS 2 custom message example'

Remove the created ROS objects.

clear node pub sub

Input Arguments

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Path to the ROS interfaces folder, which is the parent folder of ROS message packages, specified as a string scalar or character vector. The parent folder should contain a package.xml file and package folders. These folders contain a /msg folder with .msg files for message definitions. For more information, see About ROS 2 Interfaces.

Example: "/opt/ros2/dashing/share"

Data Types: char | string

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'BuildConfiguration','fasterruns'

Build configuration, specified as the comma-separated pair consisting of 'BuildConfiguration' and a character vector or string scalar containing 'fasterbuilds' or 'fasterruns'.

  • 'fasterbuilds' — Build the message libraries with compiler optimizations for shorter build times.

  • 'fasterruns' — Build the message libraries with compiler optimizations for faster execution.

Example: ros2genmsg("/opt/ros2/dashing/share",'BuildConfiguration','fasterruns')

Data Types: char | string


Restart Nodes

  • After generating custom messages, restart any existing ROS 2 nodes.

Code Generation with custom messages:

  • Custom message and service types can be used with ROS 2 functionality for generating C++ code for a standalone ROS 2 node. The generated code (.tgz archive) will include definitions for the custom messages, but it will not include the ROS 2 custom message packages. When the generated code is built in the destination, it expects the custom message packages to be available in the colcon workspace which should be your current working directory. Please ensure that you either install or copy the custom message package to your system before building the generated code.

MATLAB Compiler

  • ROS 2 custom messages and the ros2genmsg function are not supported with MATLAB Compiler™.

Introduced in R2019b