std::thread and ros::ok() do not work in ROS - c++

Question

I have a function that is executing by std::thread. I want it works until the user closes the terminal that running roscore by pressing Ctrl+C. Because of that I use this inside the thread:
void publish_camera_on_topic(std::vector<Camera> cameras, const std::vector<ros::Publisher> publishers, const int camera_index)
{
int frameSize;
BYTE *imagePtr;
// frame id
int frame_id = 0;
cv_bridge::CvImage img_bridge;
sensor_msgs::Image img_msg;
while (ros::ok()) {
// Grab and display a single image from each camera
imagePtr = cameras[camera_index].getRawImage();
frameSize = cameras[camera_index].getFrameSize();
cameras[camera_index].createRGBImage(imagePtr,frameSize);
unsigned char* pImage = cameras[camera_index].getImage();
if (NULL != pImage) {
Mat image(cameras[camera_index].getMatSize(), CV_8UC3, pImage, Mat::AUTO_STEP);
// release asap
cameras[camera_index].releaseImage();
//cvtColor(image, image, CV_BGR2RGB,3);
// publish on ROS topic
std_msgs::Header header; // empty header
header.seq = frame_id; // user defined counter
header.stamp = ros::Time::now(); // time
img_bridge = cv_bridge::CvImage(header, sensor_msgs::image_encodings::RGB8, image);
img_bridge.toImageMsg(img_msg); // from cv_bridge to sensor_msgs::Image
publishers[camera_index].publish(img_msg); // ros::Publisher pub_img = node.advertise<sensor_msgs::Image>("topic", queuesize);
}
// increase frame Id
frame_id = frame_id + 1;
}
std::cout << "ROS closing for thread of camera " << camera_index << " recieved." << std::endl;
}
Also, I create thread like this:
// image publisher
// for each camera create an publisher
std::vector<ros::Publisher> publishers;
for (size_t i = 0; i < cameras.size(); i++) {
char topic_name[200];
sprintf(topic_name, "/lumenera_camera_package/%d", i + 1);
publishers.push_back(nh.advertise<sensor_msgs::Image>(topic_name, 10));
}
// work with each camera on a seprate thread
std::vector<std::thread> thread_vector;
for(size_t i=0; i < cameras.size(); i++) {
thread_vector.push_back(std::thread(publish_camera_on_topic, cameras, publishers, i));
}
ros::spin();
std::for_each(thread_vector.begin(), thread_vector.end(), [](std::thread &t){t.join(); });
for(size_t i=0; i < cameras.size(); i++) {
cameras[i].stopStreaming();
}
ROS_INFO("Node: [lumenera_camera_node] has been Ended.");
However, when I press Ctrl+C in the terminal and stop the roscore, the threads keep running, and the value of ros::ok() does not change.

Answer 1

The problem is solved. The issue is ros::ok() does not check for ROS master. Instead of this line:
while (ros::ok()) { //do sth}
This line should be used:
while (ros::ok() && ros::master::check()) { // do sth}