sem.h(3head)

1sem.h(3HEAD)                        Headers                       sem.h(3HEAD)
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NAME

6       sem.h, sem -  semaphore facility
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SYNOPSIS

9       #include <sys/sem.h>
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DESCRIPTION

13       The <sys/sem.h> header defines the following constants and structures.
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16       Semaphore operation flags:
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18       SEM_UNDO    Set up adjust on exit entry.
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22       Command  definitions  for  the semctl() function are provided as listed
23       below. See semctl(2).
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25       GETNCNT    Get semncnt.
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28       GETPID     Get sempid.
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31       GETVAL     Get semval.
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34       GETALL     Get all cases of semval.
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37       GETZCNT    Get semzcnt.
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40       SETVAL     Set semval.
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43       SETALL     Set all cases of semval.
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47       The semid_ds structure contains the following members:
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49         struct ipc_perm sem_perm     /* operation permission structure */
50         unsigned short  sem_nsems    /* number of semaphores in set */
51         time_t          sem_otime    /* last semop() time */
52         time_t          sem_ctime    /* last time changed by semctl() */
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56       The pid_t, time_t, key_t, and size_t types are defined as described  in
57       <sys/types.h>. See types.h(3HEAD).
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60       A  semaphore  is  represented  by an anonymous structure containing the
61       following members:
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63         unsigned short semval     /* semaphore value */
64         pid_t          sempid     /* process ID of last operation */
65         unsigned short semncnt    /* number of processes waiting for semval
66                                      to become greater than current value */
67         unsigned short semzcnt    /* number of processes waiting for semval
68                                      to become 0 */
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72       The sembuf structure contains the following members:
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74         unsigned short sem_num     /* semaphore number */
75         short          sem_op      /* semaphore operation */
76         short          sem_flg     /* operation flags */
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80       All of the symbols from <sys/ipc.h> are defined  when  this  header  is
81       included. See ipc.h(3HEAD).
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ATTRIBUTES

84       See attributes(5) for descriptions of the following attributes:
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89       ┌─────────────────────────────┬─────────────────────────────┐
90       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
91       ├─────────────────────────────┼─────────────────────────────┤
92       │Interface Stability          │Standard                     │
93       └─────────────────────────────┴─────────────────────────────┘
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NAME

SYNOPSIS

DESCRIPTION

ATTRIBUTES

SEE ALSO