rb_fd_set         243 include/ruby/intern.h #define rb_fd_set(n, f)	FD_SET(n, f)
rb_fd_set        2192 thread.c       rb_fd_set(int n, rb_fdset_t *fds)
rb_fd_set        2271 thread.c       rb_fd_set(int fd, rb_fdset_t *set)