CMake is an open-source, cross-platform tool designed to manage the build process of software projects. It plays a crucial role in ROS (Robot Operating System) as the primary build system for managing and building ROS packages. ROS uses a build tool called catkin, which is built on top of CMake, to organize, configure, and compile the code in a ROS workspace.

Demo how to use CMake (catkin) in ROS to build a package.

Step 1: create a package named my_robot_pkg that relies on std_msgs and roscpp

catkin_create_pkg my_robot_pkg std_msgs roscpp

Step2 : the CMake file is generated and to be interpreted, a typical CMakelists.txt contains a. project declaration, b. find dependencies, c declare Catkin package, d. include directories, e. add executables and link libraries, f. install targets.

Step 3: once the CMakelist.txt file is created, build the package using the catkin_make command, This invokes CMake to generate the necessary build files for your package, compiles the source code, and produces the executables or libraries.

cd ~/catkin_ws
catkin_make

Step 4: ready to run the node in the package

rosrun my_robot_pkg my_robot_node

Step 5: Modify the CMakeLists.txt file to handle additional dependencies or changes in the code structure as your ROS project grows.

Here’s a simple example CMakeLists.txt for a ROS package named robot_controller:

cmake_minimum_required(VERSION 3.0.2)
project(robot_controller)

find_package(catkin REQUIRED COMPONENTS
  roscpp
  std_msgs
)

catkin_package()

include_directories(
  include
  ${catkin_INCLUDE_DIRS}
)

add_executable(controller_node src/controller_node.cpp)

target_link_libraries(controller_node
  ${catkin_LIBRARIES}
)

install(TARGETS controller_node
  RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
)

Using package building as example here, a typical package in ROS include:

CMakeLists.txt: Defines how the package should be built using CMake. package.xml: Defines metadata and dependencies, like what other ROS packages or libraries are required. src/: Directory where the source code files (C++ or Python) are stored. launch/: Directory containing launch files that define how to run multiple nodes together.