The ROS Filesystem¶
Package¶
Now that you have gotten a little experience with ROS2, you're ready to start working within the file system.
Packages are the software organization unit of ROS2 code. Each package can contain libraries, executables, scripts, or other artifacts. For example, the turtlesim and teleop_turtle nodes are both contained in the turtlesim package.
Filesystem Tool: ros2 pkg¶
ros2 pkg allows you to get information about packages.
ros2 pkg prefix¶
ros2 pkg prefix returns the prefix path to the package.
Usage:
ros2 pkg prefix [package_name]
Example:
ros2 pkg prefix rclcpp
Would return (might be different if you have a different installation path):
/opt/ros/jazzy
ros2 pkg prefix only gives you the prefix path instead of the absolute path. To actually "cd" (Change Directory) to a certain package, try:
cd $(ros2 pkg prefix [package_name])
cd share/[package_name]
ros2 pkg list¶
ros2 pkg list outputs a list of available packages.
ros2 pkg executables¶
ros2 pkg executables outputs a list of package specific executables.
Example:
ros2 pkg executables turtlesim
turtlesim draw_square
turtlesim mimic
turtlesim turtle_teleop_key
turtlesim turtlesim_node
ros2 pkg create¶
ros2 pkg create is used to create a new package. You'll learn more about this command in Lesson 5.
More Filesystem Concepts¶
colcon¶
In ROS1, the build tool we often use is "catkin_make". In ROS2, we use colcon which is an iteration on catkin_make, catkin_make_isolated, catkin_tools, and ament_tools.
Please install colcon with:
sudo apt install python3-colcon-common-extensions
Workspace & Package¶
Normally we would put our packages in one place, and a workspace is the directory where you can store your packages.
A single workspace can have as many packages as you need. Every package has its own folder, and can be of different build types (ament_python, ament_cmake, cmake).
In order to complete the following tutorial in Lesson 5 we need a package in which to place our launch file in. Go ahead and complete these two tutorials from the official ROS tutorials.
Review¶
- ROS2 packages: an organizational unit for ROS2 code
ros2 pkg: a filesystem tool to interface with packagesros2 pkg prefix: output the prefix path of a packageros2 pkg list: outputs a list of available packagesros2 pkg executables: outputs a list of package specific executablesros2 pkg create: create a new package