// This function disables input echo
// and input line editing (backspace,
// etc.) so your program can react
// immediately to input characters
// (ICANON).  It returns a null
// pointer on success or a pointer
// to an error message on failure.
// It spawns a child process using fork()
// to reset the terminal to its previous
// state when your program exits.
// It doesn't disable processing of
// signal characters (^Z, ^C, ^\).
const char *enable_cbreak(int fd);