2 .\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
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31 .Nd control operations on a semaphore set
39 .Fn semctl "int semid" "int semnum" "int cmd" ...
44 performs the operation indicated by
46 on the semaphore set indicated by
49 .Fa "union semun arg" ,
50 is required for certain values of
52 For the commands that use the
56 must be defined as follows:
59 int val; /* value for SETVAL */
60 struct semid_ds *buf; /* buffer for IPC_STAT & IPC_SET */
61 u_short *array; /* array for GETALL & SETALL */
64 Non-portable software may define
68 to use the system definition of
71 Commands are performed as follows:
73 .\" This section based on Stevens, _Advanced Programming in the UNIX
76 .Bl -tag -width IPC_RMIDXXX
78 Fetch the semaphore set's
79 .Fa "struct semid_ds" ,
80 storing it in the memory pointed to by
88 members of the semaphore set's
90 to match those of the struct pointed to by
92 The calling process's effective uid must
97 or it must have superuser privileges.
99 Immediately removes the semaphore set from the system.
101 process's effective uid must equal the semaphore set's
105 or the process must have superuser privileges.
107 Return the value of semaphore number
110 Set the value of semaphore number
114 Outstanding adjust on exit values for this semaphore in any process
117 Return the pid of the last process to perform an operation on
121 Return the number of processes waiting for semaphore number
123 value to become greater than its current value.
125 Return the number of processes waiting for semaphore number
129 Fetch the value of all of the semaphores in the set into the
133 Set the values of all of the semaphores in the set to the values
134 in the array pointed to by
136 Outstanding adjust on exit values for all semaphores in this set,
137 in any process are cleared.
141 .Vt "struct semid_ds"
142 is defined as follows:
144 .\" Taken straight from <sys/sem.h>.
148 struct ipc_perm sem_perm; /* operation permission struct */
149 u_short sem_nsems; /* number of sems in set */
150 time_t sem_otime; /* last operation time */
151 time_t sem_ctime; /* last change time */
152 /* Times measured in secs since */
153 /* 00:00:00 GMT, Jan. 1, 1970 */
160 .Dv GETVAL , GETPID , GETNCNT
164 returns the corresponding value; otherwise, 0 is returned.
165 On failure, -1 is returned, and
167 is set to indicate the error.
175 No semaphore set corresponds to
181 is not in the range of valid semaphores for given semaphore set.
183 The calling process's effective uid does not match the uid of
184 the semaphore set's owner or creator.
186 Permission denied due to mismatch between operation and mode of
192 attempted to set a semaphore outside the allowable range
200 may update some semaphore elements before returning an error.