ROS Melodic

Package Structure


ws_catkin
├── devel
├── build
└── src
    └── package_name
        ├── CMakeList.txt
        ├── package.xml
        ├── arduino           --- arduino_sketch.ino
        ├── config            --- config.yaml
        ├── doc               --- pdf jpg
        ├── include
        │   └── package_name  --- cppheader.h
        ├── src               --- cppsource.cpp
        ├── scripts           --- python_script.py
        ├── launch            --- launch_file.launch
        ├── action            --- action.action
        ├── msg               --- msg.msg
        ├── srv               --- srv.srv
        ├── rviz              --- rviz_config.rviz
        ├── test              --- unitest.cpp/.py
        └── gazebo
            ├── meshes        --- model.STL/.dae
            ├── models        --- model.config/.sdf/.urdf
            ├── urdf          --- model.xacro/.gazebo
            └── worlds        --- model.world

Workspaces and Package

Create Workspace


mkdir catkin_ws && cd catkin_ws
wstool init src
catkin_make
source devel/setup.bash

Add Repo to Workspace


roscd; cd ../src
wstool set repo_name \
--git http://github.com/org/repo_name.git \
--version=melodic-devel
wstool up

Resolve Dependencies in Workspace


sudo rosdep init  # only once
rosdep update
rosdep install --from-paths src --ignore-src \
--rosdistro=${ROS_DISTRO} -y

Create Package


catkin_create_pkg package_name [dependencies ...]

CMakeList.txt

Skeleton


cmake_minimum_required(VERSION 2.8.3)
project(package_name)
find_package(catkin REQUIRED)
catkin_package()

Package Dependencies


find_package(catkin REQUIRED COMPONENTS roscpp)
Tell dependent packages what headers or libraries to pull in when your package is declared as a catkin component:
catkin_package(
    INCLUDE_DIRS include
    LIBRARIES ${PROJECT_NAME}
    CATKIN_DEPENDS roscpp)

Messages, Services


find_package(catkin REQUIRED COMPONENTS message_generation std_msgs)
add_message_files(FILES MyMessage.msg)
add_service_files(FILES MyService.msg)
generate_messages(DEPENDENCIES std_msgs)
catkin_package(CATKIN_DEPENDS message_runtime std_msgs)

Build Libraries, Executables


add_library(${PROJECT_NAME} src/cpp_code.cpp)
add_executable(${PROJECT_NAME}_node src/cpp_code.cpp)
target_link_libraries(${PROJECT_NAME}_node ${catkin_LIBRARIES})
add_dependencies(${PROJECT_NAME} beginner_tutorials_generate_messages_cpp)

Installation


install(TARGETS ${PROJECT_NAME} DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION})
install(TARGETS ${PROJECT_NAME}_node DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION})
install(PROGRAMS scripts/myscript DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION})
install(DIRECTORY launch DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION})

Remote Connection

To connect remotely, ensure the following:

Master’s ROS environment:

ROS_IP or ROS_HOSTNAME set to this machine’s network address.
ROS_MASTER_URI set to URI containing that IP or hostname.

Your environment:

ROS_IP or ROS_HOSTNAME set to your machine’s network address.
ROS_MASTER_URI set to the URI from the master.

To debug, check ping from each side to the other, run roswtf on each side.

Command Line Interfaces

Command	Description
`rosnode list`	List available ROS nodes
`rostopic list`	List available ROS topics
`rostopic echo /topic_name`	Print out data in topic name
`rostopic hz /topic_name`	Calculate frequency of topic
`rostopic info /topic_name`	Show information of topic
`rosmsg show message_msgs/msg_name`	Show information of data in ROS message
`rospack find {package_name}`	Find the location of the package
`rospack depends {package_name}`	Find the packages that the package depends on
`rospack help`	Show description of rospack
`rosrun rqt_graph rqt_graph`	Show rqt graph
`roscd {package_name}`	Change directory to ROS package in system
`rosls {package_name}`	List content in the directory
`find . -name".py" -exec chmod +x {} \;`	Find all files ending in .py and make them executable