Taking arguments via command line for launch files.

edit

I am trying to pass a value to a parameter in a node via the launch file.

I created a basic node that would print the parameter it read or it would give an error saying no parameter.

even though I pass a parameter the node is not able to read it.

I have added the code of the launch file and node below.

Launch File:

<launch>

<arg name="station" />

<node pkg="param_from_launch" type="trial" name="trial">
  <param name="param_1" value="$(arg station)"/>
</node>

</launch>

C++ Node:

#include "ros/ros.h"
#include <iostream>

int main(int argc, char **argv)
{
  // Set up ROS.
    ros::init(argc, argv, "trial");
    ros::NodeHandle n("~");   // private namespace

    int param_1;

    n.param<int>("param_from_launch", param_1, 0);
    if(n.param("param_from_launch", param_1)){
        ROS_INFO("param_from_launch: %d", param_1);
    }
    else{
        ROS_ERROR("NO PARAM");
    }
    // Let ROS handle all callbacks.
    ros::spin();

    return 0;
}  // end main()

running the node separately gives me the expected output: param_from_launch: 0. but when running the launch file I get [ERROR] [1644580954.583154879]: NO PARAM