1.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice(s), this list of conditions and the following disclaimer as 9.\" the first lines of this file unmodified other than the possible 10.\" addition of one or more copyright notices. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice(s), this list of conditions and the following disclaimer in 13.\" the documentation and/or other materials provided with the 14.\" distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE 20.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 23.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 24.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 25.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 26.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27.\" 28.Dd January 9, 2010 29.Dt SEM_INIT 3 30.Os 31.Sh NAME 32.Nm sem_init 33.Nd initialize an unnamed semaphore 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In semaphore.h 38.Ft int 39.Fn sem_init "sem_t *sem" "int pshared" "unsigned int value" 40.Sh DESCRIPTION 41The 42.Fn sem_init 43function initializes the unnamed semaphore pointed to by 44.Fa sem 45to have the value 46.Fa value . 47.Pp 48A non-zero value for 49.Fa pshared 50specifies a shared semaphore that can be used by multiple processes, 51the semaphore should be located in shared memory region (see 52.Xr mmap 2 , 53.Xr shm_open 2 , 54and 55.Xr shmget 2 ) , 56any process having read and write access to address 57.Fa sem 58can perform semaphore operations on 59.Fa sem . 60.Pp 61Following a successful call to 62.Fn sem_init , 63.Fa sem 64can be used as an argument in subsequent calls to 65.Xr sem_wait 3 , 66.Xr sem_trywait 3 , 67.Xr sem_post 3 , 68and 69.Xr sem_destroy 3 . 70The 71.Fa sem 72argument is no longer valid after a successful call to 73.Xr sem_destroy 3 . 74.Sh RETURN VALUES 75.Rv -std sem_init 76.Sh ERRORS 77The 78.Fn sem_init 79function will fail if: 80.Bl -tag -width Er 81.It Bq Er EINVAL 82The 83.Fa value 84argument exceeds 85.Dv SEM_VALUE_MAX . 86.It Bq Er ENOSPC 87Memory allocation error. 88.El 89.Sh SEE ALSO 90.Xr sem_destroy 3 , 91.Xr sem_getvalue 3 , 92.Xr sem_post 3 , 93.Xr sem_trywait 3 , 94.Xr sem_wait 3 95.Sh STANDARDS 96The 97.Fn sem_init 98function conforms to 99.St -p1003.1-96 . 100