1 .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later 2 .. c:namespace:: MC 3 4 .. _request-func-poll: 5 6 ************** 7 request poll() 8 ************** 9 10 Name 11 ==== 12 13 request-poll - Wait for some event on a file descriptor 14 15 Synopsis 16 ======== 17 18 .. code-block:: c 19 20 #include <sys/poll.h> 21 22 .. c:function:: int poll( struct pollfd *ufds, unsigned int nfds, int timeout ) 23 24 Arguments 25 ========= 26 27 ``ufds`` 28 List of file descriptor events to be watched 29 30 ``nfds`` 31 Number of file descriptor events at the \*ufds array 32 33 ``timeout`` 34 Timeout to wait for events 35 36 Description 37 =========== 38 39 With the :c:func:`poll()` function applications can wait 40 for a request to complete. 41 42 On success :c:func:`poll()` returns the number of file 43 descriptors that have been selected (that is, file descriptors for which the 44 ``revents`` field of the respective struct :c:type:`pollfd` 45 is non-zero). Request file descriptor set the ``POLLPRI`` flag in ``revents`` 46 when the request was completed. When the function times out it returns 47 a value of zero, on failure it returns -1 and the ``errno`` variable is 48 set appropriately. 49 50 Attempting to poll for a request that is not yet queued will 51 set the ``POLLERR`` flag in ``revents``. 52 53 Return Value 54 ============ 55 56 On success, :c:func:`poll()` returns the number of 57 structures which have non-zero ``revents`` fields, or zero if the call 58 timed out. On error -1 is returned, and the ``errno`` variable is set 59 appropriately: 60 61 ``EBADF`` 62 One or more of the ``ufds`` members specify an invalid file 63 descriptor. 64 65 ``EFAULT`` 66 ``ufds`` references an inaccessible memory area. 67 68 ``EINTR`` 69 The call was interrupted by a signal. 70 71 ``EINVAL`` 72 The ``nfds`` value exceeds the ``RLIMIT_NOFILE`` value. Use 73 ``getrlimit()`` to obtain this value.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.