Creating a ROS Package

1.What makes up a catkin Package?

• The simplest possible package might have a structure which looks like this:

  my_package/
  CMakeLists.txt
  package.xml
  

2.Packages in a catkin Workspace

• The recommended method of working with catkin packages is using a catkin workspace, but you can also build catkin packages standalone. A trivial workspace might look like this:

    workspace_folder/        -- WORKSPACE
      src/                   -- SOURCE SPACE
        CMakeLists.txt       -- 'Toplevel' CMake file, provided by catkin
        package_1/
          CMakeLists.txt     -- CMakeLists.txt file for package_1
          package.xml        -- Package manifest for package_1
        ...
        package_n/
          CMakeLists.txt     -- CMakeLists.txt file for package_n
          package.xml        -- Package manifest for package_n

3.Creating a catkin Package

1. First change to the source space directory of the catkin workspace you created in the Creating a Workspace for catkin tutorial:

   # You should have created this in the Creating a Workspace Tutorial
   $ cd ~/catkin_ws/src
   

2. Now use the catkin_create_pkg script to create a new package called 'beginner_tutorials' which depends on std_msgs, roscpp, and rospy:

   $ catkin_create_pkg beginner_tutorials std_msgs rospy roscpp
   

3. catkin_create_pkg requires that you give it a package_name and optionally a list of dependencies on which that package depends:

   # This is an example, do not try to run this
   # catkin_create_pkg <package_name> [depend1] [depend2] [depend3]
   

4.Building a catkin workspace and sourcing the setup file

1. Now you need to build the packages in the catkin workspace:

   $ cd ~/catkin_ws
   $ catkin_make
   

2. To add the workspace to your ROS environment you need to source the generated setup file:

   $ . ~/catkin_ws/devel/setup.bash
   

5.package dependencies

1. First-order dependencies
   • When using catkin_create_pkg earlier, a few package dependencies were provided. These first-order dependencies can now be reviewed with the rospack tool.

     $ rospack depends1 beginner_tutorials
     

   • As you can see, rospack lists the same dependencies that were used as arguments when running catkin_create_pkg. These dependencies for a package are stored in the package.xml file:

     $ roscd beginner_tutorials
     $ cat package.xml
     

2. Indirect dependencies

   • In many cases, a dependency will also have its own dependencies. For instance, rospy has other dependencies.

     $ rospack depends1 rospy
     

   • A package can have quite a few indirect dependencies. Luckily rospack can recursively determine all nested dependencies.

     $ rospack depends beginner_tutorials
     cpp_common
     rostime
     roscpp_traits
     roscpp_serialization
     genmsg
     genpy
     message_runtime
     rosconsole
     std_msgs
     rosgraph_msgs
     xmlrpcpp
     roscpp
     rosgraph
     catkin
     rospack
     roslib
     rospy