C++: How can I make an infinite loop stop when pressing any key?

Question

What is the best way to terminate a while loop by pressing a specific key in C++?

Answer 1

Use system signal but you will not be able to stop with all keys.

#include <iostream>
#include <csignal>

using namespace std;

void signalHandler( int signum )
{
    cout << "Interrupt signal (" << signum << ") received.\n";

    // cleanup and close up stuff here  
    // terminate program  

   exit(signum);  

}

int main ()
{
    // register signal SIGINT and signal handler  
    signal(SIGINT, signalHandler);  

    while(1){
       cout << "Going to sleep...." << endl;
       sleep(1);
    }

    return 0;
}

Answer 2

You can quit the program, but there is no real way to make it stop with any key on a basic level.

Alternatively you can use another condition for the loop, e.g.

int counter = 0;
int counterMax = 100;
while (true && (counter++ < counterMax)) {
    // your code here
}
if (counter >= counterMax) {
    std::cout << "loop terminated by counter" << std::endl;
    // maybe exit the program
}