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+.\" 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.
+.\" 3. The name of the author may not be used to endorse or promote products
+.\"    derived from this software without specific prior written permission.
+.\"
+.\" 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.
+.\"
+.\" $FreeBSD$
+.Dd July 9, 2009
+.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 .
+.Sh RETURN VALUES
+The
+.Fn ftok
+function will return -1 if
+.Fa path
+does not exist or if it cannot be accessed by the calling process.
+.Sh SEE ALSO
+.Xr semget 2 ,
+.Xr shmget 2 ,
+.Xr msgget 2
+.Sh HISTORY
+The
+.Fn ftok
+function originates 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 minor number and inode of the
+specified
+.Fa path
+in combination with the lower 8 bits of the given
+.Fa id .
+Thus it is quite possible for the routine to return duplicate keys.