123 lines
3.0 KiB
Groff
123 lines
3.0 KiB
Groff
.\"
|
|
.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
|
|
.\"
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd August 2, 1995
|
|
.Dt SHMAT 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm shmat ,
|
|
.Nm shmdt
|
|
.Nd attach or detach shared memory
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/types.h
|
|
.In sys/ipc.h
|
|
.In sys/shm.h
|
|
.Ft void *
|
|
.Fn shmat "int shmid" "const void *addr" "int flag"
|
|
.Ft int
|
|
.Fn shmdt "const void *addr"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn shmat
|
|
system call
|
|
attaches the shared memory segment identified by
|
|
.Fa shmid
|
|
to the calling process's address space.
|
|
The address where the segment
|
|
is attached is determined as follows:
|
|
.\"
|
|
.\" These are cribbed almost exactly from Stevens, _Advanced Programming in
|
|
.\" the UNIX Environment_.
|
|
.\"
|
|
.Bl -bullet
|
|
.It
|
|
If
|
|
.Fa addr
|
|
is 0, the segment is attached at an address selected by the
|
|
kernel.
|
|
.It
|
|
If
|
|
.Fa addr
|
|
is nonzero and SHM_RND is not specified in
|
|
.Fa flag ,
|
|
the segment is attached the specified address.
|
|
.It
|
|
If
|
|
.Fa addr
|
|
is specified and SHM_RND is specified,
|
|
.Fa addr
|
|
is rounded down to the nearest multiple of SHMLBA.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn shmdt
|
|
system call
|
|
detaches the shared memory segment at the address specified by
|
|
.Fa addr
|
|
from the calling process's address space.
|
|
.Sh RETURN VALUES
|
|
Upon success,
|
|
.Fn shmat
|
|
returns the address where the segment is attached; otherwise, -1
|
|
is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Pp
|
|
.Rv -std shmdt
|
|
.Sh ERRORS
|
|
The
|
|
.Fn shmat
|
|
system call
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
No shared memory segment was found corresponding to
|
|
.Fa shmid .
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa addr
|
|
argument
|
|
was not an acceptable address.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn shmdt
|
|
system call
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa addr
|
|
argument
|
|
does not point to a shared memory segment.
|
|
.El
|
|
.Sh "SEE ALSO"
|
|
.Xr shmctl 2 ,
|
|
.Xr shmget 2
|