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102 lines
2.8 KiB
Groff
102 lines
2.8 KiB
Groff
.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
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.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 9, 2010
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.Dt SEM_INIT 3
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.Os
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.Sh NAME
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.Nm sem_init
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.Nd initialize an unnamed semaphore
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In semaphore.h
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.Ft int
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.Fn sem_init "sem_t *sem" "int pshared" "unsigned int value"
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.Sh DESCRIPTION
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The
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.Fn sem_init
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function initializes the unnamed semaphore pointed to by
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.Fa sem
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to have the value
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.Fa value .
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.Pp
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A non-zero value for
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.Fa pshared
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specifies a shared semaphore that can be used by multiple processes,
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the semaphore should be located in shared memory region (see
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.Xr mmap 2 ,
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.Xr shm_open 2 ,
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and
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.Xr shmget 2 ) ,
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any process having read and write access to address
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.Fa sem
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can perform semaphore operations on
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.Fa sem .
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.Pp
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Following a successful call to
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.Fn sem_init ,
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.Fa sem
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can be used as an argument in subsequent calls to
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.Xr sem_wait 3 ,
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.Xr sem_trywait 3 ,
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.Xr sem_post 3 ,
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and
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.Xr sem_destroy 3 .
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The
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.Fa sem
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argument is no longer valid after a successful call to
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.Xr sem_destroy 3 .
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.Sh RETURN VALUES
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.Rv -std sem_init
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.Sh ERRORS
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The
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.Fn sem_init
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa value
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argument exceeds
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.Dv SEM_VALUE_MAX .
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.It Bq Er ENOSPC
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Memory allocation error.
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.El
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.Sh SEE ALSO
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.Xr sem_destroy 3 ,
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.Xr sem_getvalue 3 ,
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.Xr sem_post 3 ,
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.Xr sem_trywait 3 ,
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.Xr sem_wait 3
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.Sh STANDARDS
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The
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.Fn sem_init
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function conforms to
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.St -p1003.1-96 .
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