5.12. request poll()¶
5.12.1. Name¶
request-poll - Wait for some event on a file descriptor
5.12.2. Synopsis¶
#include <sys/poll.h>
-
int
poll
(struct pollfd *ufds, unsigned int nfds, int timeout)¶
5.12.3. Arguments¶
ufds
- List of file descriptor events to be watched
nfds
- Number of file descriptor events at the *ufds array
timeout
- Timeout to wait for events
5.12.4. Description¶
With the poll()
function applications can wait
for a request to complete.
On success poll()
returns the number of file
descriptors that have been selected (that is, file descriptors for which the
revents
field of the respective struct pollfd
is non-zero). Request file descriptor set the POLLPRI
flag in revents
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
set appropriately.
Attempting to poll for a request that is not yet queued will
set the POLLERR
flag in revents
.
5.12.5. Return Value¶
On success, 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
appropriately:
EBADF
- One or more of the
ufds
members specify an invalid file descriptor. EFAULT
ufds
references an inaccessible memory area.EINTR
- The call was interrupted by a signal.
EINVAL
- The
nfds
value exceeds theRLIMIT_NOFILE
value. Usegetrlimit()
to obtain this value.