#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int main(void)
{
    struct timeval tv;
    fd_set readfds;

    tv.tv_sec = 3;
    tv.tv_usec = 500000;

    FD_ZERO(&readfds);
    FD_SET(STDIN_FILENO, &readfds);

    select(STDIN_FILENO+1, &readfds, NULL, NULL, &tv);

    if (FD_ISSET(STDIN_FILENO, &readfds))
        printf("A key was pressed!\n");
    else
        printf("Timed out.\n");

    return 0;
}