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1.1 root 1: .TH SEMGET 2
2: .SH NAME
3: semget \- get set of semaphores
4: .SH SYNOPSIS
5: .B #include <sys/types.h>
6: .br
7: .B #include <sys/ipc.h>
8: .br
9: .B #include <sys/sem.h>
10: .PP
11: .nf
12: .BR "int semget (key, nsems, semflg)
13: .B key_t key;
14: .B int nsems, semflg;
15: .fi
16: .SH DESCRIPTION
17: .I Semget
18: returns the semaphore identifier associated with
19: .IR key .
20: .PP
21: A semaphore identifier and associated data structure and set containing
22: .I nsems
23: semaphores
24: (see
25: .IR intro (2))
26: are created for
27: .I key
28: if one of the following are true:
29: .IP
30: .I Key
31: is equal to
32: .SM
33: .BR IPC_PRIVATE .
34: .IP
35: .I Key
36: does not already have a semaphore identifier associated with it, and
37: .RI ( semflg " & "
38: .SM
39: .BR IPC_CREAT\*S )
40: is ``true''.
41: .PP
42: Upon creation, the data structure associated with the new semaphore
43: identifier is initialized as follows:
44: .IP
45: .BR Sem_perm.cuid ", " sem_perm.uid ,
46: .BR sem_perm.cgid ", and " sem_perm.gid
47: are set equal to the effective user
48: .SM ID
49: and effective group
50: .SM ID\*S,
51: respectively, of the calling process.
52: .IP
53: The low-order 9 bits of
54: .B sem_perm.mode
55: are set equal to the low-order 9 bits of
56: .IR semflg .
57: .IP
58: .B Sem_nsems
59: is set equal to the value of
60: .IR nsems .
61: .IP
62: .B Sem_otime
63: is set equal to 0 and
64: .B sem_ctime
65: is set equal to the current time.
66: .PP
67: .I Semget
1.1.1.2 ! root 68: fails if one or more of the following are true:
1.1 root 69: .TP 15
70: \s-1[EINVAL]\s+1
71: .I Nsems
72: is either less than or equal to zero or greater than the system-imposed limit.
73: .TP
74: \s-1[EACCES]\s+1
75: A semaphore identifier exists for
76: .IR key ,
77: but operation permission (see
78: .IR intro (2))
79: as specified by the low-order 9 bits of
80: .I semflg
81: would not be granted.
82: .TP
83: \s-1[EINVAL]\s+1
84: A semaphore identifier exists for
85: .IR key ,
86: but the number of semaphores in the set associated with it is less than
87: .IR nsems " and " nsems
88: is not equal to zero.
89: .TP
90: \s-1[ENOENT]\s+1
91: A semaphore identifier does not exist for
92: .I key
93: and
94: .RI ( semflg " &"
95: .SM
96: .BR IPC_CREAT\*S )
97: is ``false''.
98: .TP
99: \s-1[ENOSPC]\s+1
100: A semaphore identifier is to be created but
101: the system-imposed limit on the maximum number of
102: allowed semaphore identifiers system wide
103: would be exceeded.
104: .TP
105: \s-1[ENOSPC]\s+1
106: A semaphore identifier is to be created but
107: the system-imposed limit on the maximum number of
108: allowed semaphores system wide
109: would be exceeded.
110: .TP
111: \s-1[EEXIST]\s+1
112: A semaphore identifier exists for
113: .I key
114: but
115: .RI "((" semflg " & "
116: .SM
117: .RB IPC_CREAT\*S ") and ("
118: .IR semflg " & "
119: .SM
120: .BR IPC_EXCL\*S "))"
121: is ``true''.
122: .br
123: .if \n()s .bp
124: .SH "RETURN VALUE"
125: Upon successful completion,
126: a non-negative integer,
127: namely a semaphore identifier, is returned.
128: Otherwise, a value of \-1 is returned and
129: .I errno\^
130: is set to indicate the error.
131: .SH SEE ALSO
132: intro(2), semctl(2), semop(2).
133: .\" @(#)semget.2 6.2 of 9/6/83
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