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33 .Nd control operations on a semaphore set
41 .Fn semctl "int semid" "int semnum" "int cmd" ...
46 performs the operation indicated by
48 on the semaphore set indicated by
51 .Fa "union semun arg" ,
52 is required for certain values of
54 For the commands that use the
58 must be defined as follows:
61 int val; /* value for SETVAL */
62 struct semid_ds *buf; /* buffer for IPC_STAT & IPC_SET */
63 u_short *array; /* array for GETALL & SETALL */
66 Non-portable software may define
70 to use the system definition of
73 Commands are performed as follows:
75 .\" This section based on Stevens, _Advanced Programming in the UNIX
78 .Bl -tag -width IPC_RMIDXXX
80 Fetch the semaphore set's
81 .Fa "struct semid_ds" ,
82 storing it in the memory pointed to by
90 members of the semaphore set's
92 to match those of the struct pointed to by
94 The calling process's effective uid must
99 or it must have superuser privileges.
101 Immediately removes the semaphore set from the system.
103 process's effective uid must equal the semaphore set's
107 or the process must have superuser privileges.
109 Return the value of semaphore number
112 Set the value of semaphore number
116 Outstanding adjust on exit values for this semaphore in any process
119 Return the pid of the last process to perform an operation on
123 Return the number of processes waiting for semaphore number
125 value to become greater than its current value.
127 Return the number of processes waiting for semaphore number
131 Fetch the value of all of the semaphores in the set into the
135 Set the values of all of the semaphores in the set to the values
136 in the array pointed to by
138 Outstanding adjust on exit values for all semaphores in this set,
139 in any process are cleared.
143 .Vt "struct semid_ds"
144 is defined as follows:
146 .\" Taken straight from <sys/sem.h>.
150 struct ipc_perm sem_perm; /* operation permission struct */
151 u_short sem_nsems; /* number of sems in set */
152 time_t sem_otime; /* last operation time */
153 time_t sem_ctime; /* last change time */
154 /* Times measured in secs since */
155 /* 00:00:00 GMT, Jan. 1, 1970 */
162 .Dv GETVAL , GETPID , GETNCNT
166 returns the corresponding value; otherwise, 0 is returned.
167 On failure, -1 is returned, and
169 is set to indicate the error.
177 No semaphore set corresponds to
183 is not in the range of valid semaphores for given semaphore set.
185 The calling process's effective uid does not match the uid of
186 the semaphore set's owner or creator.
188 Permission denied due to mismatch between operation and mode of
194 attempted to set a semaphore outside the allowable range
202 may update some semaphore elements before returning an error.