how to get the parent id in c++ with thread?

Question

I want to know how I can get the parent id from a created thread. I had the idea that i make an id variable in the main function and give it as a parameter when i create the thread, but it doesn't work. Or can i get the parent id otherwise?

My code:

void first(std::thread::id id) {
//do something
cout << id << endl;
}

int main() {

std::thread::id id = std::this_thread::get_id();
std::thread thread(first, id);

return 0;

}

What are your ideas?

You have to join your thread before the program terminates with `thread.join();` before the `return 0;` statement. — Bas Groothedde, May 26 '21 at 08:22

molicious · Answer 1 · 2021-05-26T09:39:19.710

The program

#include <iostream>
#include <thread>

void first(std::thread::id id) {
    std::cout << "ID in thread: "<< id << std::endl;
    std::thread::id ownID = std::this_thread::get_id();
    std::cout << "ID of thread: " << ownID << std::endl;
}

int main() {
    std::thread::id id = std::this_thread::get_id();
    std::cout << "ID in main: " << id << std::endl;
    std::thread thread(first, id);
    thread.join();
    return 0;
}

generates the output:

ID in main: 1
ID in thread: 1
ID of thread: 2

If this isn't the desired output, please clarify your question.
By the way: Your idea seems to be the best solution, because even the system does not keep track of parent threads. Is it possible to get parent threadID from child?

how to get the parent id in c++ with thread?

1 Answers1