94 lines
2.9 KiB
Groff
94 lines
2.9 KiB
Groff
|
.\" $NetBSD: ftok.3,v 1.16 2010/04/27 15:26:59 jruoho Exp $
|
||
|
|
.\"
|
||
|
|
.\" Copyright (c) 1994 SigmaSoft, Th. Lockert <tholo@sigmasoft.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 AUTHOR ``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 AUTHOR 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.
|
||
|
|
.\"
|
||
|
|
.Dd April 27, 2010
|
||
|
|
.Dt FTOK 3
|
||
|
|
.Os
|
||
|
|
.Sh NAME
|
||
|
|
.Nm ftok
|
||
|
|
.Nd create IPC identifier from path name
|
||
|
|
.Sh LIBRARY
|
||
|
|
.Lb libc
|
||
|
|
.Sh SYNOPSIS
|
||
|
|
.In sys/types.h
|
||
|
|
.In sys/ipc.h
|
||
|
|
.Ft key_t
|
||
|
|
.Fn ftok "const char *path" "int id"
|
||
|
|
.Sh DESCRIPTION
|
||
|
|
The
|
||
|
|
.Fn ftok
|
||
|
|
function attempts to create a unique key suitable for use with the
|
||
|
|
.Xr msgget 2 ,
|
||
|
|
.Xr semget 2
|
||
|
|
and
|
||
|
|
.Xr shmget 2
|
||
|
|
functions given the
|
||
|
|
.Fa path
|
||
|
|
of an existing file and a user-selectable
|
||
|
|
.Fa id .
|
||
|
|
.Pp
|
||
|
|
The specified
|
||
|
|
.Fa path
|
||
|
|
must specify an existing file that is accessible to the calling process
|
||
|
|
or the call will fail.
|
||
|
|
Also, note that links to files will return the same key, given the same
|
||
|
|
.Fa id .
|
||
|
|
.Pp
|
||
|
|
Only the 8 least significant bits of
|
||
|
|
.Fa id
|
||
|
|
are used in the key generation; the rest of the bits are ignored.
|
||
|
|
.Sh RETURN VALUES
|
||
|
|
The
|
||
|
|
.Fn ftok
|
||
|
|
function will return ((key_t)-1) if
|
||
|
|
.Fa path
|
||
|
|
does not exist or if it cannot be accessed by the calling process.
|
||
|
|
.Sh SEE ALSO
|
||
|
|
.Xr msgget 2 ,
|
||
|
|
.Xr semget 2 ,
|
||
|
|
.Xr shmget 2
|
||
|
|
.Sh STANDARDS
|
||
|
|
The
|
||
|
|
.Fn ftok
|
||
|
|
function conforms to
|
||
|
|
.St -p1003.1 .
|
||
|
|
.Sh HISTORY
|
||
|
|
The
|
||
|
|
.Fn ftok
|
||
|
|
function originated with System V and is typically used by programs
|
||
|
|
that use the System V IPC routines.
|
||
|
|
.Sh AUTHORS
|
||
|
|
.An Thorsten Lockert Aq tholo@sigmasoft.com
|
||
|
|
.Sh BUGS
|
||
|
|
The returned key is computed based on the device and inode of the
|
||
|
|
specified
|
||
|
|
.Fa path
|
||
|
|
in combination with the given
|
||
|
|
.Fa id .
|
||
|
|
Thus it is quite possible for the routine to return duplicate keys
|
||
|
|
given that those fields are not 8- and 16-bit quantities like they
|
||
|
|
were on System V based systems where this library routine's ancestor
|
||
|
|
were originally created.
|