svsem/semun.h

This is svsem/semun.h (Listing 47-2, page 970), an example from the book, The Linux Programming Interface.

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/* semun.h

   Definition of the semun union used by the System V semaphore semop()
   system call.
*/
#ifndef SEMUN_H
#define SEMUN_H                 /* Prevent accidental double inclusion */

#include <sys/types.h>          /* For portability */
#include <sys/sem.h>

#if ! defined(__FreeBSD__) && ! defined(__OpenBSD__) && \
                ! defined(__sgi) && ! defined(__APPLE__)
                /* Some implementations already declare this union */

union semun {                   /* Used in calls to semctl() */
    int                 val;
    struct semid_ds *   buf;
    unsigned short *    array;
#if defined(__linux__)
    struct seminfo *    __buf;
#endif
};

#endif

#endif

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