setting parameters in ros launch file programatically

edit

You could load a yaml file from the Lauch File. Thereby your 'outside world' Programm could Specify the params by creating a yaml file and then Lauch the roslauch and Point it to the created yaml file that roslauch loads via rosparam load.....

Edit:

ros uses yaml-cp as stated here:

http://answers.ros.org/question/12321...

Link to yaml-cpp:

https://github.com/jbeder/yaml-cpp

No, however, this is also not what those parameters are for. If you want to set parameters "on the fly", you should use dynamic_reconfigure Link.

If you want to actually edit launch files from a program, you would have to write this yourself (e.g. by plugging into the roslaunch API).

Or, if you just want to change parameters that are on the parameter server (i.e. after the launch file has been launched), you could use the getParam/setParam functions. Then again, this will not let nodes reload those parameters easily. this is what dynamic_reconfigure is for.

EDIT1

This cannot be done using ROS standard tools. If this is coming from the outside world (i.e. non-ROS), I'd suggest you create a program that reads the launch file (you need to pass in the file path, or you could tap into the rospack API to get the path of the file), edit what you need, and rewrite it.