poll.h File Reference

Definitions for the poll() function. More...

#include <sys/cdefs.h>
#include <sys/types.h>

Go to the source code of this file.

Data Structures
struct	pollfd
	Structure representing a single file descriptor used by poll(). More...

Macros
#define	POLLRDNORM   (1 << 0)
	Normal data may be read. More...
#define	POLLRDBAND   (1 << 1)
	Priority data may be read. More...
#define	POLLPRI   (1 << 2)
	High-priority data may be read. More...
#define	POLLOUT   (1 << 3)
	Normal data may be written. More...
#define	POLLWRNORM   POLLOUT
	Normal data may be written. More...
#define	POLLWRBAND   (1 << 4)
	Priority data may be written. More...
#define	POLLERR   (1 << 5)
	Error has occurred (revents only) More...
#define	POLLHUP   (1 << 6)
	Peer disconnected (revents only) More...
#define	POLLNVAL   (1 << 7)
	Invalid fd (revents only) More...
#define	POLLIN   (POLLRDNORM | POLLRDBAND)
	Data other than high-priority data may be read. More...

Typedefs
typedef __uint32_t	nfds_t
	Type representing a number of file descriptors. More...

Functions
int	poll (struct pollfd fds[], nfds_t nfds, int timeout)
	Poll a group of file descriptors for activity. More...

Detailed Description

Definitions for the poll() function.

This file contains the definitions needed for using the poll() function, as directed by the POSIX 2008 standard (aka The Open Group Base Specifications Issue 7). Currently the functionality defined herein only works for sockets, and that is likely how it will stay for some time.

The poll() function works quite similarly to the select() function that it is quite likely that you'd be more familiar with.

Author

Lawrence Sebald

Typedef Documentation

typedef __uint32_t nfds_t

Type representing a number of file descriptors.

Function Documentation

int poll	(	struct pollfd	fds[],
		nfds_t	nfds,
		int	timeout
	)

Poll a group of file descriptors for activity.

This function will poll a group of file descriptors to check for the events specified on them. The function shall block for the specified period of time (in milliseconds) waiting for an event to occur. The function shall return as soon as at least one fd matches the events specified (or one of the error conditions), or when timeout expires.

Parameters

fds	The file descriptors to check, and what events to look for on each.
nfds	Number of elements in fds.
timeout	Maximum amount of time to block, in milliseconds. Pass 0 to ensure the function does not block and -1 to block for an "infinite" amount of time, until an event occurs.

Returns

-1 on error (sets errno as appropriate), or the number of file descriptors that matched the event flags before the function returns.

See also

Events for the poll() function