FD_ZERO           118 ext/readline/readline.c     FD_ZERO(&rset);
FD_ZERO           242 include/ruby/intern.h #define rb_fd_zero(f)	FD_ZERO(f)
FD_ZERO           248 include/ruby/intern.h #define rb_fd_init(f)	FD_ZERO(f)
FD_ZERO          2155 thread.c           FD_ZERO(fds->fdset);
FD_ZERO          2171 thread.c       	FD_ZERO(fds->fdset);
FD_ZERO          2259 thread.c           FD_ZERO(set->fdset);