terminate & launch other node from code

edit

We've encountered this problem as well. On our robot, we have ROS set to autoboot on power-up. At this point, it boots into a "minimal" state in which only a few nodes are running until we receive a connection to an external network. At that point, it will launch the rest of the ROS nodes. Why we do this isn't really important, but here's HOW we do it... Just a warning, it's fairly complex.

Our whole autoboot/control system is based on a Bash/C++ interface. You are able to pipe the output of a C++ program to a Bash script and read the output. To do this, your C++ program must simply output to stdout and Bash can read it. Here's a quick example of what I mean:

control.cpp

#include <iostream>
#include <string>
#include <unistd.h>

using namespace std;

int main(int argc, char** argv)
{
    while(1)
    {
      if(guiNotConnected())
      {
        cout << "Connected" << endl;
      }
      sleep(1);
    }
}

control.bash

#!/bin/bash

function cpp_func {

    /home/robot/scripts/control

}
while read line; do
    if [ "$line" == "Connected" ]; then
        roslaunch robot_launch rest_of_ros.launch
    fi
done < <(cpp_func)

In the above example, "/home/robot/scripts/control" represents the location of the c++ executable on the filesystem. The reason it's wrapped in a Bash function is because Bash doesn't allow you to pipe an executable directly in to the function. I.E. "done << /home/robot/scripts/control" is not allowed. That's why the executable is wrapped in the Bash function cpp_func.

This allows us to execute any functions we want (start, kill, restart, etc.) on any node we want. As long as you expect an output in your Bash script, you can handle any ROS commandline processes from that one control.bash script. Just a note, you cannot send commands back to the c++ program using this method.

I just had the same problem and was stunned to see how difficult it was to find a simple example for this basic task. So I added a minimal code example to the roslaunch wiki page:

http://wiki.ros.org/roslaunch/API%20U...