old_flags         284 src/subshell/common.c     const int old_flags = fcntl (fd, F_GETFL);
old_flags         286 src/subshell/common.c     fcntl (fd, F_SETFL, old_flags | O_NONBLOCK);
old_flags         288 src/subshell/common.c     fcntl (fd, F_SETFL, old_flags);