System interfaces compatible with the Single Unix Specification, Version 7: Note that the core of the Single Unix Specification, Version 7 is also IEEE Std 1003.1-2017 (POSIX.1-2017). FD_CLR FD_ISSET FD_SET FD_ZERO _Exit _exit _longjmp _setjmp _tolower _toupper a64l abort abs accept access acos acosf acosh acoshf acoshl acosl aio_cancel aio_error aio_fsync aio_read aio_return aio_suspend aio_write