NOTSET
enum FMT { NOTSET, GFLAG, BSD, POSIX };
enum { NOTSET, CLEAR, CLEARALL } clear;
enum STYLE { NOTSET = 0, FBYTES, FLINES, RBYTES, RLINES, REVERSE };
#define NOTSET(s) ((s) == 0)
typedef enum { NOTSET, FORWARD, BACKWARD } dir_t;