To work with ROS one needs to source the environmental setup

source /opt/ros/melodic/setup.zsh 

rospack find NAME
rospack find roscpp

roscd NAME
roscd turtle

rosls NAME
rosls turtle

rospack depends NAME
rospack depends1 NAME
rospack depends1 rospy

To create a package one first must create and cd to subdirectory project/src/

catkin_create_pkg <package_name> [depend1] [depend2] [depend3]
catkin_create_pkg beginner_tutorials std_msgs rospy roscpp

To build a catkin workspace must first cd to project/ and run

catkin_make

To source workspace to ROS environment

source src/devel/setup.zsh

Starting ROS core server

roscore

Listing and getting information about ROS nodes

rosnode list
rosnode info /rosout

rosrun allows you to use the package name to directly run a node within a package

rosrun [package_name] [node_name]
rosrun turtlesim turtlesim_node
rosrun turtlesim turtlesim_node __name:=my_turtle

ROS graph showing the interaction between nodes and topics

rosrun turtlesim turtlesim_node
rosrun turtlesim turtle_teleop_key
rosrun rqt_graph rqt_graph

Listing ROS Topics

rostopic list -v

List data published to the Topic

rostopic echo [topic]
rostopic echo /turtle1/cmd_vel

Get the message type of the published Topic

rostopic type /turtle1/cmd_vel

Get the details of the message type

rosmsg show geometry_msgs/Twist

Publishing data to ROS Topic

rostopic pub [topic] [msg_type] [args]
rostopic pub -1 /turtle1/cmd_vel geometry_msgs/Twist -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, 1.8]'
rostopic pub /turtle1/cmd_vel geometry_msgs/Twist -r 1 -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, -1.8]'

Reports rate at which data is published to Topic

rostopic hz [topic]
rostopic hz /turtle1/pose

Display plots of data published to the Topics

rosrun rqt_plot rqt_plot

Services allow to request a node for a response.

Basic commands

rosservice list

rosservice type [service]
rosservice type /clear

rosservice call [service] [args]
rosservice call /clear
rosservice call /spawn 2 2 0.2 ""

ROS Parameters allow to store data in ROS Parameter Server

rosparam list

rosparam set [param_name]
rosparam get [param_name]

rosparam set /background_r 150
rossservice call /clear

Recording a replaying ROS inputs.

Recording a bagfile

mkdir ~/bagfiles
cd ~/bagfiles
rosbag record -a
rosbag record -O subset /turtle1/cmd_vel /turtle1/pose

Examining bagfile

rosbag info FILE

Replaying bagfile

rosbag play FILE
rosbag play -r 2 FILE