1. Performance of yes is not a concern for that "common case" (well, is that case still common? who writes only interactive program that require yes/no anwers f

1. Performance of yes is not a concern for that "common case" (well, is that case still common? who writes only interactive program that require yes/no anwers from the terminal?). 2. Filling a buffer has much less CPU (power) cost as it doesn't involve context switching like I/O.