*nix alternative for _kbhit() subroutine. https://stackoverflow.com/questions/1449324/how-to-simulate-press-any-key-to-continue
#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <fcntl.h>
int kbhit(void) {
struct termios oldt, newt;
int ch;
int oldf;
tcgetattr(STDIN_FILENO, &oldt);
newt = oldt;
newt.c_lflag &= ~(ICANON | ECHO);
tcsetattr(STDIN_FILENO, TCSANOW, &newt);
oldf = fcntl(STDIN_FILENO, F_GETFL, 0);
fcntl(STDIN_FILENO, F_SETFL, oldf | O_NONBLOCK);
ch = getchar();
tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
fcntl(STDIN_FILENO, F_SETFL, oldf);
if (ch != EOF) {
ungetc(ch, stdin);
return 1;
}
return 0;
}