I have a bash script as follows:

bash
foldername=camera_calibration_$(date +"%m-%d-%Y")
im_name="/cam0"
roslaunch image_pub cam_calibration.launch foldername:=$foldername image_name:=$im_name

My roslaunch script is as follows:

<launch>
  <arg name = "foldername" default="camera_calibration" />
  <arg name = "image_name" default="/cam1" />

  <param name="foldername" type="string" value="$(arg foldername)" />
  <param name="image_name" type="string" value="$(arg image_name)" />
  <param name="size_name" type="string" value="12x8" />
  <param name="square" type="string" value="0.05" />

  <node name="im_pub_sub_node" pkg="image_pub" type="im_pub_sub" output="screen"/>
  <node name="cameracalibrator_node" pkg="camera_calibration" type="cameracalibrator.py" output="screen"/>
</launch>

My C++ script (impubsub.cpp) as follows:

int main(int argc, char** argv) {
    std::string foldername;
    std::string imagename;
    std::string si_name;
    ros::param::get("/size_name", si_name);
    ros::param::get("/foldername", foldername);
    ros::param::get("/image_name", imagename);
    std::cout<<imagename<<std::endl;
    std::cout<<foldername<<std::endl;
    std::cout<<si_name<<std::endl;
    std::cout<<"hi"<<std::endl;
}

When I launch it I only get "hi" print on my console but not foldername, imagename defined from bash and siname param defined in launch file. It prints empty like nothing for other params defined.

Can anyone please let me know what is wrong? And how to get the print?

int main(int argc, char** argv) {

    ros::init(argc, argv, "im_sub_pub_cpp");
    ros::NodeHandle nh_;

    std::string foldername;
    std::string imagename;
    std::string si_name;
    ros::param::get("/size_name", si_name);
    ros::param::get("/foldername", foldername);
    ros::param::get("/image_name", imagename);
    std::cout<<imagename<<std::endl;
    std::cout<<foldername<<std::endl;
    std::cout<<si_name<<std::endl;
    std::cout<<"hi"<<std::endl;
}