include/sys/select.h File Reference

#include <sys/time.h>
#include <signal.h>

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Data Structures
struct	fd_set
	File descriptor set structure for select and pselect. More...
Defines
#define	_ABLE_CLIB_SYS_SELECT_H   1
#define	FD_SETSIZE   32
	Maximum number of file descriptors in fd_set.
#define	NFDBITS   (8 * sizeof(fd_mask))
	Number of bits per entry in fd_set.
#define	__FDS_BITS(set)   ((set)->fds_bits)
#define	__FDELT(x)   ((x) / NFDBITS)
#define	__FDMASK(x)   ((fd_mask) 1 << ((x) % NFDBITS))
#define	FD_ZERO(fdsetp)
	Clear the FD set pointed to by fdsetp.
#define	FD_SET(fd, fdsetp)   (__FDS_BITS(fdsetp)[__FDELT(fd)] |= __FDMASK(fd))
	Set a file descriptor in a fd set.
#define	FD_CLR(fd, fdsetp)   (__FDS_BITS(fdsetp)[__FDELT(fd)] &= ~__FDMASK(fd))
	Clear a file descriptor in a fd set.
#define	FD_ISSET(fd, fdsetp)   ((__FDS_BITS(fdsetp)[__FDELT(fd)] & __FDMASK(fd)) != 0)
	Check if a file descriptor is set in a fd set.
Typedefs
typedef unsigned long	fd_mask
	Define the fd_mask type for the entries in fd_set.
Functions
int	select (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
	Wait for an event on one or more file descriptors in a set.
int	pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask)
	Wait for an event on one or more file descriptors in a set.

---

Define Documentation

#define __FDELT

(

x

)

((x) / NFDBITS)

#define __FDMASK

(

x

)

((fd_mask) 1 << ((x) % NFDBITS))

#define __FDS_BITS

(

set

)

((set)->fds_bits)

#define _ABLE_CLIB_SYS_SELECT_H   1

#define FD_CLR	(	fd,
		fdsetp		)	(__FDS_BITS(fdsetp)[__FDELT(fd)] &= ~__FDMASK(fd))

Clear a file descriptor in a fd set.

#define FD_ISSET	(	fd,
		fdsetp		)	((__FDS_BITS(fdsetp)[__FDELT(fd)] & __FDMASK(fd)) != 0)

Check if a file descriptor is set in a fd set.

#define FD_SET	(	fd,
		fdsetp		)	(__FDS_BITS(fdsetp)[__FDELT(fd)] |= __FDMASK(fd))

Set a file descriptor in a fd set.

#define FD_SETSIZE   32

Maximum number of file descriptors in fd_set.

#define FD_ZERO

(

fdsetp

)

Value:

do {                                                                   \
        unsigned int __bit;                                                \
        fd_set *__arr = (fdsetp);                                          \
        for (__bit = 0; __bit < sizeof(fd_set) / sizeof(fd_mask); ++__bit) \
            __FDS_BITS(__arr)[__bit] = 0;                                  \
    } while (0)

Clear the FD set pointed to by fdsetp.

#define NFDBITS   (8 * sizeof(fd_mask))

Number of bits per entry in fd_set.

The name is dictated by convention rather than standard.

---

Typedef Documentation

typedef unsigned long fd_mask

Define the fd_mask type for the entries in fd_set.

Convention dictates that both the type, as unsigned long, and the name as fd_mask.

---

Function Documentation

int pselect	(	int	nfds,
		fd_set *	readfds,
		fd_set *	writefds,
		fd_set *	exceptfds,
		const struct timespec *	timeout,
		const sigset_t *	sigmask
	)

Wait for an event on one or more file descriptors in a set.

Wait for events to occur on the file descriptors listed in readfds writefds and exceptfds, returning the set of events which have occurred. A timeout can be provided to limit how long to wait for events.

Parameters:

	nfds	The Maximum number of file descriptors to examine.
	readfds	The set of file descriptors to examine for read readyness.
	writefds	The set of file descriptors to examine for write readyness.
	exceptfds	The set of file descriptors to examine for exceptions.
	timeout	The length of time to wait for an event or NULL for no timeout.
	sigmask	Signal mask to set during call.

Returns:

The number of fd which have pending events.

int select	(	int	nfds,
		fd_set *	readfds,
		fd_set *	writefds,
		fd_set *	exceptfds,
		struct timeval *	timeout
	)

Wait for an event on one or more file descriptors in a set.

Wait for events to occur on the file descriptors listed in readfds writefds and exceptfds, returning the set of events which have occurred. A timeout can be provided to limit how long to wait for events.

Parameters:

	nfds	The Maximum number of file descriptors to examine.
	readfds	The set of file descriptors to examine for read readyness.
	writefds	The set of file descriptors to examine for write readyness.
	exceptfds	The set of file descriptors to examine for exceptions.
	timeout	The length of time to wait for an event or NULL for no timeout.

Returns:

The number of fd which have pending events.