* 'n': check for "line" ending with an \n char
* 'e': check for "line" starting with an \n char
* 'f': check for "line" not starting with an \n char
* 'n': check for "line" ending with an \n char
* 'e': check for "line" starting with an \n char
* 'f': check for "line" not starting with an \n char