Roslaunch

Roslaunch is a tool for easily launching multiple ROS nodes as well as setting parameters. Roslaunch takes in one or more XML configuration files (with the .launch extension) that specify the parameters to set and nodes to launch, as well as the machines that they should be run on.

Basic sytax is

<launch>
  <param name="/parameter_name" type="variable_type" value="variable_value"/>
  <node name="name_of_the_node" pkg="name_of_the_package" type="source_file.py" ns="namespace" args="optional arguments"/>
  <include file="included.launch">
    <arg name="arg_name" value="arg_val" />
  </include>
</launch>

New .launch

Create new package rpi_feros_bringup used for launch files:

roscd
cd ..
cd src
catkin_create_pkg rpi_feros_bringup

Go the new package and create folder launch

roscd rpi_feros_bringup
mkdir launch
cd launch

Inside the folder create new file feros.launch

touch rpi_led.launch
code rpi_led.launch

Copy the following lines

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<?xml version="1.0"?>

<launch>
    <node name="btn_pub" pkg="rpi_feros" type="button_publisher.py" output="screen"/>
    <node name="led_act" pkg="rpi_feros" type="led_actuator.py" output="screen"/>   
</launch>

To run the rpi_led.launch use roslaunch function

roslaunch rpi_feros_bringup rpi_led.launch

By running this .launch file three things are started

• roscore (automatically),
• button_publisher.py, and
• led_actuator.py.