2 .\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
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33 .Nd obtain a semaphore id
39 .Fn semget "key_t key" "int nsems" "int flag"
41 Based on the values of
46 returns the identifier of a newly created or previously existing
49 .\" This is copied verbatim from the shmget manpage. Perhaps
50 .\" it should go in a common manpage, such as .Xr ipc 2
53 is analogous to a filename: it provides a handle that names an
55 There are three ways to specify a key:
58 IPC_PRIVATE may be specified, in which case a new IPC object
61 An integer constant may be specified.
62 If no IPC object corresponding
65 is specified and the IPC_CREAT bit is set in
67 a new one will be created.
72 may be used to generate a key from a pathname.
75 .\" Likewise for this section, except SHM_* becomes SEM_*.
78 The mode of a newly created IPC object is determined by ORing these constants
86 Alter access for user.
88 Read access for group.
90 Alter access for group.
92 Read access for other.
94 Alter access for other.
97 If a new set of semaphores is being created,
99 is used to indicate the number of semaphores the set should contain.
102 may be specified as 0.
107 returns the id of a semaphore set if successful; otherwise, -1
110 is set to indicate the error.
117 .\" ipcperm could fail (we are opening to read and write, as it were)
119 Access permission failure.
121 .\" sysv_sem.c is quite explicit about these, so I'm pretty sure
125 IPC_CREAT and IPC_EXCL were specified, and a semaphore set
130 The number of semaphores requested exceeds the system imposed maximum
133 A semaphore set corresponding to
135 already exists and contains fewer semaphores than
138 A semaphore set corresponding to
144 Insufficiently many semaphores are available.
146 The kernel could not allocate a
147 .Fa "struct semid_ds" .
149 No semaphore set was found corresponding to
151 and IPC_CREAT was not specified.