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sem.h (3)

>> sem.h (3) ( Solaris man: Библиотечные вызовы )

sem.h (3) ( POSIX man: Библиотечные вызовы )

NAME

sem.h, sem -  semaphore facility

SYNOPSIS

#include <sys/sem.h>

DESCRIPTION

The <sys/sem.h> header defines the following constants and structures.

Semaphore operation flags:

SEM_UNDO

: Set up adjust on exit entry.

Command definitions for the semctl() function are provided as listed below. See semctl(2).

GETNCNT

: Get semncnt.

GETPID

: Get sempid.

GETVAL

: Get semval.

GETALL

: Get all cases of semval.

GETZCNT

: Get semzcnt.

SETVAL

: Set semval.

SETALL

: Set all cases of semval.

The semid_ds structure contains the following members:

struct ipc_perm sem_perm     /* operation permission structure */
unsigned short  sem_nsems    /* number of semaphores in set */
time_t          sem_otime    /* last semop() time */
time_t          sem_ctime    /* last time changed by semctl() */

The pid_t, time_t, key_t, and size_t types are defined as described in <sys/types.h>. See types.h(3HEAD).

A semaphore is represented by an anonymous structure containing the following members:

unsigned short semval     /* semaphore value */
pid_t          sempid     /* process ID of last operation */
unsigned short semncnt    /* number of processes waiting for semval
                            to become greater than current value */
unsigned short semzcnt    /* number of processes waiting for semval
                            to become 0 */

The sembuf structure contains the following members:

unsigned short sem_num     /* semaphore number */
short          sem_op      /* semaphore operation */
short          sem_flg     /* operation flags */

All of the symbols from <sys/ipc.h> are defined when this header is included. See ipc.h(3HEAD).