5.12. request poll()¶
request-poll - Wait for some event on a file descriptor
poll(struct pollfd *ufds, unsigned int nfds, int timeout)¶
- List of file descriptor events to be watched
- Number of file descriptor events at the *ufds array
- Timeout to wait for events
poll() function applications can wait
for a request to complete.
poll() returns the number of file
descriptors that have been selected (that is, file descriptors for which the
revents field of the respective struct
is non-zero). Request file descriptor set the
POLLPRI flag in
when the request was completed. When the function times out it returns
a value of zero, on failure it returns -1 and the
errno variable is
Attempting to poll for a request that is not yet queued will
POLLERR flag in
5.12.5. Return Value¶
poll() returns the number of
structures which have non-zero
revents fields, or zero if the call
timed out. On error -1 is returned, and the
errno variable is set
- One or more of the
ufdsmembers specify an invalid file descriptor.
ufdsreferences an inaccessible memory area.
- The call was interrupted by a signal.
nfdsvalue exceeds the
getrlimit()to obtain this value.