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<sys/sem.h>(0P)            POSIX Programmer's Manual           <sys/sem.h>(0P)

NAME
       sys/sem.h - XSI semaphore facility
SYNOPSIS
       #include <sys/sem.h>
DESCRIPTION
       The  <sys/sem.h> header shall define the following constants and struc-
       tures.
       Semaphore operation flags:
       SEM_UNDO
              Set up adjust on exit entry.

       Command definitions for the semctl() function shall be provided as fol-
       lows:
       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 shall contain 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  shall  be  defined as
       described in <sys/types.h> .
       A semaphore shall be 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 shall contain the following members:

              unsigned short  sem_num   Semaphore number.
              short           sem_op    Semaphore operation.
              short           sem_flg   Operation flags.
       The following shall be declared as functions and may also be defined as
       macros. Function prototypes shall be provided.

              int   semctl(int, int, int, ...);
              int   semget(key_t, int, int);
              int   semop(int, struct sembuf *, size_t);
       In addition, all of the symbols from <sys/ipc.h> shall be defined  when
       this header is included.
       The following sections are informative.
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       <sys/ipc.h>, <sys/types.h>, semctl(), semget(), semop()
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                      <sys/sem.h>(0P)