.\"
.\" Copyright (c) 2005 Apple Computer, Inc. All rights reserved.
.\"
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+.\" @APPLE_LICENSE_HEADER_START@
.\"
.\" This file contains Original Code and/or Modifications of Original Code
.\" as defined in and that are subject to the Apple Public Source License
.\" Please see the License for the specific language governing rights and
.\" limitations under the License.
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-.\" @APPLE_OSREFERENCE_LICENSE_HEADER_END@
+.\" @APPLE_LICENSE_HEADER_END@
.\"
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.\" Copyright (c) 1996 Charles M. Hannum. All rights reserved.
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
-.Dd February 27, 2005
+.Dd March 18, 2015
.Dt POLL 2
.Os
.Sh NAME
.Sh SYNOPSIS
.In poll.h
.Ft int
-.Fn poll "struct pollfd *fds" "nfds_t nfds" "int timeout"
+.Fo poll
+.Fa "struct pollfd fds[]"
+.Fa "nfds_t nfds"
+.Fa "int timeout"
+.Fc
.Sh DESCRIPTION
-.Fn Poll
-examines a set of file descriptors to see if some of them are ready for
-I/O or if certain events have occurred on them.
+.Fn poll
+examines a set of file descriptors
+to see if some of them are ready for I/O
+or if certain events have occurred on them.
The
.Fa fds
-argument is a pointer to an array of pollfd structures as defined in
+argument is a pointer to an array of pollfd structures,
+as defined in
.Aq Pa poll.h
(shown below). The
.Fa nfds
-argument determines the size of the
+argument specifies the size of the
.Fa fds
array.
.Bd -literal
The fields of
.Fa struct pollfd
are as follows:
-.Bl -tag -width XXXrevents
+.Bl -tag -width XXXPOLLWRNORM
.It fd
File descriptor to poll.
.It events
.Fa revents
have the following bits:
.Bl -tag -width XXXPOLLWRNORM
-.It POLLIN
-Data other than high priority data may be read without blocking.
-This is equivalent to ( POLLRDNORM | POLLRDBAND ).
-.It POLLRDNORM
-Normal data may be read without blocking.
-.It POLLRDBAND
-Priority data may be read without blocking.
-.It POLLPRI
-High priority data may be read without blocking.
-.It POLLOUT
-.It POLLWRNORM
-Normal data may be written without blocking.
-.It POLLWRBAND
-Priority data may be written without blocking.
+.\" ===========
.It POLLERR
-An exceptional condition has occurred on the device or socket. This
-flag is output only, and ignored if present in the input
+An exceptional condition has occurred on the device or socket.
+This flag is output only, and ignored if present in the input
.Fa events
bitmask.
+.\" ===========
.It POLLHUP
-The device or socket has been disconnected. This flag is output only,
+The device or socket has been disconnected.
+This flag is output only,
and ignored if present in the input
.Fa events
-bitmask. Note that
-POLLHUP
-and
-POLLOUT
+bitmask.
+Note that POLLHUP and POLLOUT
are mutually exclusive and should never be present in the
.Fa revents
bitmask at the same time.
+.\" ===========
+.It POLLIN
+Data other than high priority data may be read without blocking.
+This is equivalent to ( POLLRDNORM | POLLRDBAND ).
+.\" ===========
.It POLLNVAL
-The file descriptor is not open. This flag is output only, and ignored if present in the input
+The file descriptor is not open.
+This flag is output only, and ignored if present in the input
.Fa events
bitmask.
+.\" ===========
+.It POLLOUT
+Normal data may be written without blocking.
+This is equivalent to POLLWRNORM.
+.\" ===========
+.It POLLPRI
+High priority data may be read without blocking.
+.\" ===========
+.It POLLRDBAND
+Priority data may be read without blocking.
+.\" ===========
+.It POLLRDNORM
+Normal data may be read without blocking.
+.\" ===========
+.It POLLWRBAND
+Priority data may be written without blocking.
+.\" ===========
+.It POLLWRNORM
+Normal data may be written without blocking.
.El
.Pp
-The distinction between normal, priority, and high-priority data is file type
-or device specific.
+The distinction between normal, priority, and high-priority data
+is specific to particular file types or devices.
.Pp
If
.Fa timeout
-is greater than zero, it specifies a maximum interval to
-wait for any file descriptor to become ready, in milliseconds. If
+is greater than zero,
+it specifies a maximum interval (in milliseconds)
+to wait for any file descriptor to become ready.
+If
.Fa timeout
is zero, then
.Fn poll
.Fa timeout
is -1, the poll blocks indefinitely.
.Sh RETURN VALUES
-.Fn Poll
-returns the number of descriptors that are ready for I/O, or -1 if an
-error occured. If the time limit expires,
+.Fn poll
+returns the number of descriptors that are ready for I/O,
+or -1 if an error occurred.
+If the time limit expires,
.Fn poll
returns 0.
If
including one due to an interrupted call,
the
.Fa fds
-array will be unmodified.
+array will be unmodified and the global variable
+.Va errno
+will be set to indicate the error.
.Sh ERRORS
-An error return from
.Fn poll
-indicates:
+will fail if:
.Bl -tag -width Er
+.\" ===========
+.It Bq Er EAGAIN
+Allocation of internal data structures fails.
+A subsequent request may succeed.
+.\" ===========
.It Bq Er EFAULT
.Fa Fds
points outside the process's allocated address space.
+.\" ===========
.It Bq Er EINTR
-A signal was delivered before the time limit expired and
-before any of the selected events occurred.
+A signal is delivered before the time limit expires
+and before any of the selected events occurs.
+.\" ===========
.It Bq Er EINVAL
The
.Fa nfds
-argument is greater than OPEN_MAX, or the
+argument is greater than OPEN_MAX or the
.Fa timeout
argument is less than -1.
.El
.Sh SEE ALSO
.Xr accept 2 ,
.Xr connect 2 ,
+.Xr connectx 2 ,
.Xr kevent 2 ,
.Xr read 2 ,
.Xr recv 2 ,
.Fn poll
function call appeared in
.At V .
-
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