问为什么当我在Ubuntu终端上发送SIGTERM (Ctrl + C)时，我的C++代码没有终止？

EN

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

int main(int argc, char **argv){
    ros::init(argc, argv, "read_usb");
    ros::NodeHandle nh;
    ros::Rate loop_rate(100);
    while(ros::ok()){       
        std::string str;
        std::fstream openmv_cam_h7;
        openmv_cam_h7.open("/dev/ttyACM0");     
        while(openmv_cam_h7 >> str){
            std::cout << str << std::endl;
        }
        openmv_cam_h7.close();
        ros::spinOnce();
        loop_rate.sleep();
    }
}