sem.h(3HEAD)							      Headers							      sem.h(3HEAD)

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).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       semctl(2), semget(2), semop(2), ipc.h(3HEAD), types.h(3HEAD), attributes(5), standards(5)

SunOS 5.11							    10 Sep 2004 						      sem.h(3HEAD)