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1.1 root 1:
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3: semctl() COHERENT System Call semctl()
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8: Control semaphore operations
9:
10: #include <sys/sem.h>
11: sseemmccttll(_s_e_m_i_d, _s_e_m_n_u_m, _c_m_d, _a_r_g)
12: iinntt _s_e_m_i_d, _c_m_d, _s_e_m_n_u_m;
13: uunniioonn sseemmuunn {
14: iinntt _v_a_l;
15: ssttrruucctt sseemmiidd_ddss *_b_u_f;
16: uunnssiiggnneedd sshhoorrtt _a_r_r_a_y[];
17: } _a_r_g;
18:
19: semctl controls a variety of semaphore operations. cmd sets the
20: operation to be performed; the following cmds are executed with
21: respect to the semaphore specified by semid and semnum:
22:
23: GGEETTVVAALL
24: Return the value of sseemmvvaall (READ).
25:
26: SSEETTVVAALL
27: Set the value of sseemmvvaall to _a_r_g._v_a_l (ALTER).
28:
29: GGEETTPPIIDD
30: Return the value of sseemmppiidd (READ).
31:
32: GGEETTNNCCNNTT
33: Return the value of sseemmnnccnntt (READ).
34:
35: GGEETTZZCCNNTT
36: Return the value of sseemmzzccnntt (READ).
37:
38: The following cmds return and set, respectively, every semval in
39: the set of semaphores.
40:
41: GGEETTAALLLL Place semvals into array pointed to by _a_r_g._a_r_r_a_y
42: (READ).
43:
44: SSEETTAALLLL Set semvals according to the array pointed to by
45: _a_r_g._a_r_r_a_y (ALTER).
46:
47: The following cmds are also available:
48:
49: IIPPCC_SSTTAATT Place the current value of each member of the data
50: structure associated with semid into the structure
51: pointed to by _a_r_g._b_u_f (READ).
52:
53: IIPPCC_SSEETT Set the value of the following members of the data
54: structure associated with semid to the corresponding
55: value found in the structure pointed to by arg.buf:
56:
57: sem_perm.uid
58: sem_perm.gid
59: sem_perm.mode /* only low 9 bits */
60:
61: This command can only be executed by a process that has
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63:
64: COHERENT Lexicon Page 1
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68:
69: semctl() COHERENT System Call semctl()
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71:
72:
73: an effective user identifier equal to either that of
74: superuser or to the value of sem_perm.uid in the data
75: structure associated with semid.
76:
77: IIPPCC_RRMMIIDD Remove the system identifier specified by semid from
78: the system and destroy the set of semaphores and data
79: structure associated with it. This cmd can only be ex-
80: ecuted by a process that has an effective user iden-
81: tifier equal to either that of super user or to the
82: value of sem_perm.uid in the data structure associated
83: with semid.
84:
85: semctl will fail if one or more of the following are true:
86:
87: * semid is not a valid semaphore identifier [EINVAL].
88:
89: * semnum is less than zero or greater than sem_nsems [EINVAL].
90:
91: * cmd is not a valid command [EINVAL].
92:
93: * Operation permission is denied to the calling process.
94: [EACCES]
95:
96: * cmd is SETVAL or SETALL and the value to which semval is to be
97: set is greater than the system imposed maximum [ERANGE].
98:
99: * cmd is equal to IPC_RMID or IPC_SET and the effective user
100: identifier of the calling process is not equal to that of su-
101: peruser and it is not equal to the value of sem_perm.uid in
102: the data structure associated with semid [EPERM].
103:
104: * arg.buf points to an illegal address [EFAULT].
105:
106: ***** Return Value *****
107:
108: Upon successful completion, the value returned depends on cmd as
109: follows:
110:
111:
112: GGEETTVVAALL The value of sseemmvvaall.
113: GGEETTPPIIDD The value of sseemmppiidd.
114: GGEETTNNCCNNTT The value of sseemmnnccnntt.
115: GGEETTZZCCNNTT The value of sseemmzzccnntt.
116: All othersZero
117:
118:
119: Otherwise, semctl returns -1 and sets eerrrrnnoo to an appropriate
120: value.
121:
122: ***** Files *****
123:
124: /usr/include/sys/ipc.h
125: /usr/include/sys/sem.h
126: /dev/sem
127: /drv/sem
128:
129:
130: COHERENT Lexicon Page 2
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134:
135: semctl() COHERENT System Call semctl()
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138:
139:
140: ***** See Also *****
141:
142: COHERENT system calls, sem, semget(), semop()
143:
144: ***** Notes *****
145:
146: To improve portability, the COHERENT system implements the
147: semaphore functions as a device driver rather than as an actual
148: system call.
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196: COHERENT Lexicon Page 3
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