Parameters

Parameter server: globally available dictionary within ROS master

ROS parameter: one variable within the parameter server

Types:

• Boolean
• Int
• Double
• String
• Lists
• ...

Example

Code examples:

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# set parameter
rospy.set_param('/publish_frequency', 2)

# get parameter
publish_freq = rospy.get_param('/publish_frequency')

# get list of parameters
try:
  rospy.get_param_names()
except ROSException:
  print("Could not get param names")

Set parameter in a launch file:

<param name="/parameter_name" type="parameter_type" value="value"/>

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<launch>
  <param name="/publish_frequency" type="int" value="2"/>
</launch>

<rosparam> is used if you want to load a list of parameters from a .yaml file

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<rosparam command="load" file="$(find <package_name>)/example.yaml" />

DEBUG

• rosparam set <param name> <value> - to create new parameter
• rosparam get <param name> - get parameter value
• rosparam list - get list of parameters

Exercise

Upgrade SimpleActionClient by setting number of runs as parameter /number_of_runs.

Upgrade SimpleActionServer by setting LED frequency as parameter /led_frequency.

Create .launch file for Action Server.