Read during a few second in C++ - c++

Question

I want to know how can i read the standard input just for 5 seconds like you just have 5 seconds to write.
#include <iostream>
#include <string>
using namespace std;
int main ()
{
string mystr;
cout << "What's your name? ";
getline (cin, mystr);
cout << "Hello " << mystr << ".\n";
cout << "What is your favorite team? ";
getline (cin, mystr);
cout << "I like " << mystr << " too!\n";
return 0;
}
Like that the user have all the time he want to write. Did getline or read have any option to force the getline to stop after 5sec ?
Thank you

Answer 1

A possible solution is to use poll() and write your own getline() function (tested on xubuntu 18.04 with g++ 7.5.0):
Here the implementation of my getline_timeout(int, std::string):
std::string getline_timeout(int ms, std::string def_value)
{
struct pollfd fds;
fds.fd = STDIN_FILENO;
fds.events = POLLIN;
int ret = poll(&fds, 1, ms);
std::string val;
if (ret > 0 && ((fds.revents & POLLIN) != 0)) {
//cout << "has data" << endl;
std::getline(std::cin, val);
} else {
//cout << "timeout / no data" << endl;
val = def_value;
}
return val;
}
#include <iostream>
#include <string>
#include <poll.h>
#include <unistd.h>
std::string getline_timeout(int ms, std::string def_value);
int main(int argc, char *argv[])
{
std::cout << "What's your name ? " << std::flush;
// Ask for the name
std::string mystr = getline_timeout(5000, "John Doe");
std::cout << "Hello " << mystr << std::endl;
std::cout << "What is your favorite team ? " << std::flush;
// Ask for the team
mystr = getline_timeout(5000, "Gryffindor");
std::cout << "I like " << mystr << " too!" << std::endl;
return 0;
}

Answer 2

The API getline() can not do what you want.
There are two way you can try:
- multi thread can work
- single thread with multiplexing IO like select/poll/epoll/iocp
In fact, they work same : setting a timer and wait for I/O input or timeout.