********************
The ros2 command
********************

The following list shows the most commonly used ros2 commands.

ros2 run
========

Runs executables provided by a package.

.. code-block:: bash

   # ros2 run <package_name> <executable_file>
   
This command starts a node. E.g., 

.. code-block:: bash

   $ ros2 run turtlesim


ros2 node
=========

Shows information about currently running ROS2 nodes.

.. code-block:: bash

   $ ros2 node list

Use this command to see a list of running nodes.

.. code-block:: bash

   # ros2 node info /<node_name>
   
Run this command to see the topics and services the node is using. E.g.,

.. code-block:: bash

   $ ros2 node /turtlesim.


ros2 pkg
============

Shows information about ROS2 packages visible in the current environment.

.. code-block:: bash

   $ ros2 pkg list

This command lists all ROS2 packages of your system.

.. code-block:: bash

   # ros2 pkg executables <package_name>
   
Use this command to see a list of executables made available by a package. E.g.,

.. code-block:: bash

   $ ros2 pkg executables turtlesim

.. code-block:: bash

   # ros2 pkg prefix <package_name>
   
This command is used to get the installation location of a package. E.g.,

.. code-block:: bash

   $ ros2 pkg prefix turtlesim

.. code-block:: bash

   # ros2 pkg create <package_name>

Use this command to create a ROS2 package including a CMakeLists.txt and
a package.xml file. E.g.,

.. code-block:: bash

   $ ros2 pkg create turtlesim

Use the optinal ``--build-type`` argument to specificially create a ROS2 Python
or ROS2 C++ package. By default you will create a C++ (cmake based) package.
E.g.,

.. code-block:: bash

   $ ros2 pkg create turtlesim --build-type ament_python  #Python

   $ ros2 pkg create turtlesim --build-type ament_cmake   #C++

Use the optional ``--node-name`` argument to create a simple Hello World type
executable in the package.

.. code-block:: bash

   $ ros2 pkg create <package_name> --build-type <build_type> --node-name <node_name> 

E.g.,

.. code-block:: bash

   $ ros2 pkg create turtlesim --build-type ament_python --node-name turtlesim_node


ros2 topic
==============

Shows information about topics currently used by one or more nodes.

.. code-block:: bash

   $ ros2 topic list -t
   
Use this command to see currently published topics and what type they are.

.. code-block:: bash

   # ros2 topic info /<topic_name>
   
This command is used to see information about a topic that the node is publishing. E.g.,

.. code-block:: bash

   $ ros2 topic info /turtle1/pose

.. code-block:: bash

   # ros2 topic echo /<topic_name>
   
Run this command to subscribe to the topic and print it on the terminal. E.g.,

.. code-block:: bash

   $ ros2 topic echo /turtle1/pose

.. code-block:: bash

   $ ros2 topic -h
   
This command shows a list of more available subcommands.

ros2 service/srv/interface  
=========================================

Shows information about ROS2 services.

.. code-block:: bash

   $ ros2 service list
   
This command lists currently available services.

.. code-block:: bash

   $ ros2 srv list

This command lists all available services on your ROS2 systems.

.. code-block:: bash

   # ros2 interface show <service_msg_type>
   
This command can be used to see the service definition of the service. E.g.,

.. code-block:: bash

   $ ros2 interface show turtlesim/srv/Spawn
   
.. code-block:: bash

   # ros2 service call /<service_name> <service_msg_type> '{<srv_request_arg_1: srv_req_arg_value_1, srv_request_arg_2: srv_req_arg_value_2, ...>}'

This command is used to manually call a service. The fields of the service request must
be set using a YAML dictionary that specifies the field names and values. E.g.,

.. code-block:: bash

   $ ros2 service call /spawn turtlesim/srv/Spawn '{x: 5.0, y: 2.5, theta: 0.6, name: eloquent}'

ros2 launch
===============

Start an installed launch file.

.. code-block:: bash

   # ros2 launch <package_name> <launch_file>
   
E.g., 

.. code-block:: bash

   $ ros2 launch turtlesim multisim.launch.py

Notice the ``.py`` suffix on the launch file, it’s a python script.

ros2 param
===============

Access parameters from command line.

.. code-block:: bash

   $ ros2 param lists

Use this command to get a list of all available paramaters.

.. code-block:: bash

   # ros2 param get <node_name> <parameter name>

This command is used to get the current value of a parameter. E.g.,

   $ ros2 param get /turtlesim background_r

.. code-block:: bash

   $ ros2 param set <node_name> <parameter name> <value>

This command is used to set a new value to a parameter. E.g.,

.. code-block:: bash

   $ ros2 param set /turtlesim background_r 150