Move pthread* manpages to lib/libpthread as they are not libc_r specific.
[dragonfly.git] / lib / libpthread / sem_init.3
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28.\" $FreeBSD: src/lib/libc_r/man/sem_init.3,v 1.1.2.9 2001/12/17 10:08:26 ru Exp $
1de703da 29.\" $DragonFly: src/lib/libc_r/man/sem_init.3,v 1.2 2003/06/17 04:26:48 dillon Exp $
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30.Dd February 15, 2000
31.Dt SEM_INIT 3
32.Os
33.Sh NAME
34.Nm sem_init
35.Nd initialize an unnamed semaphore
36.Sh LIBRARY
37.Lb libc_r
38.Sh SYNOPSIS
39.In semaphore.h
40.Ft int
41.Fn sem_init "sem_t *sem" "int pshared" "unsigned int value"
42.Sh DESCRIPTION
43The
44.Fn sem_init
45function initializes the unnamed semaphore pointed to by
46.Fa sem
47to have the value
48.Fa value .
49A non-zero value for
50.Fa pshared
51specifies a shared semaphore that can be used by multiple processes, which this
52implementation is not capable of.
53.Pp
54Following a successful call to
55.Fn sem_init ,
56.Fa sem
57can be used as an argument in subsequent calls to
58.Fa sem_wait ,
59.Fa sem_trywait ,
60.Fa sem_post ,
61and
62.Fa sem_destroy .
63.Fa sem
64is no longer valid after a successful call to
65.Fa sem_destroy .
66.Sh RETURN VALUES
67.Rv -std sem_init
68.Sh ERRORS
69.Fn sem_init
70will fail if:
71.Bl -tag -width Er
72.It Bq Er EINVAL
73.Fa value
74exceeds SEM_VALUE_MAX.
75.It Bq Er ENOSPC
76Memory allocation error.
77.It Bq Er EPERM
78Unable to initialize a shared semaphore.
79.El
80.Sh SEE ALSO
81.Xr sem_destroy 3 ,
82.Xr sem_post 3 ,
83.Xr sem_trywait 3 ,
84.Xr sem_wait 3
85.Sh STANDARDS
86.Fn sem_init
87conforms to
88.St -p1003.1-96 .
89.Pp
90This implementation does not support shared semaphores, and reports this fact
91by setting
92.Va errno
93to
94.Er EPERM .
95This is perhaps a stretch of the intention of POSIX, but is
96compliant, with the caveat that
97.Fn sem_init
98always reports a permissions error when an attempt to create a shared semaphore
99is made.