4. Building a ROS Package

Building Packages

As long as all of the system dependencies of your package are installed, we can now build your new package.

Note: If you installed ROS using apt or some other package manager, you should already have all of your dependencies.

Before continuing remember to source your environment setup file if you have not already. On Ubuntu it would be something like this:

# source /opt/ros/%YOUR_ROS_DISTRO%/setup.bash
$ source /opt/ros/kinetic/setup.bash             # For Kinetic for instance

Using catkin_make

catkin_make is a command line tool which adds some convenience to the standard catkin workflow. You can imagine that catkin_make combines the calls to cmake and make in the standard CMake workflow.

Usage:

# In a catkin workspace
$ catkin_make [make_targets] [-DCMAKE_VARIABLES=...]

For people who are unfamiliar with the standard CMake workflow, it breaks down as follows:

Note: If you run the below commands it will not work, as this is just an example of how CMake generally works.

# In a CMake project
$ mkdir build
$ cd build
$ cmake ..
$ make
$ make install  # (optionally)

This process is run for each CMake project. In contrast catkin projects can be built together in workspaces. Building zero to many catkin packages in a workspace follows this work flow:

# In a catkin workspace
$ catkin_make
$ catkin_make install  # (optionally)

The above commands will build any catkin projects found in the src folder. This follows the recommendations set by REP128. If your source code is in a different place, say my_src then you would call catkin_make like this:

Note: If you run the below commands it will not work, as the directory my_src does not exist.

# In a catkin workspace
$ catkin_make --source my_src
$ catkin_make install --source my_src  # (optionally)

For more advanced uses of catkin_make see the documentation: catkin/commands/catkin_make

Building Your Package

If you are using this page to build your own code, please also take a look at the later tutorials (C++)/(Python) since you may need to modify CMakeLists.txt.

You should already have a catkin workspace and a new catkin package called beginner_tutorials from the previous tutorial, Creating a Package. Go into the catkin workspace if you are not already there and look in the src folder:

$ cd ~/catkin_ws/
$ ls src

• beginner_tutorials/  CMakeLists.txt@  

You should see that there is a folder called beginner_tutorials which you created with catkin_create_pkg in the previous tutorial. We can now build that package using catkin_make:

$ catkin_make

You should see a lot of output from cmake and then make, which should be similar to this:

• Base path: /home/user/catkin_ws
  Source space: /home/user/catkin_ws/src
  Build space: /home/user/catkin_ws/build
  Devel space: /home/user/catkin_ws/devel
  Install space: /home/user/catkin_ws/install
  ####
  #### Running command: "cmake /home/user/catkin_ws/src
  -DCATKIN_DEVEL_PREFIX=/home/user/catkin_ws/devel
  -DCMAKE_INSTALL_PREFIX=/home/user/catkin_ws/install" in "/home/user/catkin_ws/build"
  ####
  -- The C compiler identification is GNU 4.2.1
  -- The CXX compiler identification is Clang 4.0.0
  -- Checking whether C compiler has -isysroot
  -- Checking whether C compiler has -isysroot - yes
  -- Checking whether C compiler supports OSX deployment target flag
  -- Checking whether C compiler supports OSX deployment target flag - yes
  -- Check for working C compiler: /usr/bin/gcc
  -- Check for working C compiler: /usr/bin/gcc -- works
  -- Detecting C compiler ABI info
  -- Detecting C compiler ABI info - done
  -- Check for working CXX compiler: /usr/bin/c++
  -- Check for working CXX compiler: /usr/bin/c++ -- works
  -- Detecting CXX compiler ABI info
  -- Detecting CXX compiler ABI info - done
  -- Using CATKIN_DEVEL_PREFIX: /tmp/catkin_ws/devel
  -- Using CMAKE_PREFIX_PATH: /opt/ros/kinetic
  -- This workspace overlays: /opt/ros/kinetic
  -- Found PythonInterp: /usr/bin/python (found version "2.7.1") 
  -- Found PY_em: /usr/lib/python2.7/dist-packages/em.pyc
  -- Found gtest: gtests will be built
  -- catkin 0.5.51
  -- BUILD_SHARED_LIBS is on
  -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  -- ~~  traversing packages in topological order:
  -- ~~  - beginner_tutorials
  -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  -- +++ add_subdirectory(beginner_tutorials)
  -- Configuring done
  -- Generating done
  -- Build files have been written to: /home/user/catkin_ws/build
  ####
  #### Running command: "make -j4" in "/home/user/catkin_ws/build"
  ####

Note that catkin_make first displays what paths it is using for each of the 'spaces'. The spaces are described in the REP128 and by documentation about catkin workspaces on the wiki: catkin/workspaces. The important thing to notice is that because of these default values several folders have been created in your catkin workspace. Take a look with ls:

$ ls

• build
  devel
  src

The build folder is the default location of the build space and is where cmake and make are called to configure and build your packages. The devel folder is the default location of the devel space, which is where your executables and libraries go before you install your packages.

Now that you have built your ROS package let's talk more about ROS Nodes.