Macros starting with `f' in sys

• FD_CLR sys/types.h:115
• FD_ISSET sys/types.h:116
• FD_SET sys/types.h:114
• FD_ZERO sys/types.h:117
• FFLAGS sys/fcntl.h:93
• flushq sys/tty.h:192
• FREE sys/malloc.h:240