1.\" Copyright (c) 1994 SigmaSoft, Th. Lockert <tholo@sigmasoft.com> 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, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. The name of the author may not be used to endorse or promote products 13.\" derived from this software without specific prior written permission. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 19.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 20.\" PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 21.\" OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 22.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 23.\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 24.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.Dd June 24, 1994 28.Os 29.Dt FTOK 3 30.Sh NAME 31.Nm ftok 32.Nd create IPC identifier from path name 33.Sh LIBRARY 34.Lb libc 35.Sh SYNOPSIS 36.Fd #include <sys/types.h> 37.Fd #include <sys/ipc.h> 38.Ft key_t 39.Fn ftok "const char *path" "int id" 40.Sh DESCRIPTION 41.Bf -symbolic 42This function is available from the compatibility library, libcompat. 43.Ef 44The 45.Fn ftok 46function attempts to create a unique key suitable for use with the 47.Xr msgget 3 , 48.Xr semget 2 49and 50.Xr shmget 2 51functions given the 52.Fa path 53of an existing file and a user-selectable 54.Fa id . 55.Pp 56The specified 57.Fa path 58must specify an existing file that is accessible to the calling process 59or the call will fail. Also, note that links to files will return the 60same key, given the same 61.Fa id . 62.Sh RETURN VALUES 63The 64.Fn ftok 65function will return -1 if 66.Fa path 67does not exist or if it cannot be accessed by the calling process. 68.Sh SEE ALSO 69.Xr semget 2 , 70.Xr shmget 2 , 71.Xr msgget 3 72.Sh HISTORY 73The 74.Fn ftok 75function originates with System V and is typically used by programs 76that use the System V IPC routines. 77.Sh AUTHORS 78.An Thorsten Lockert Aq tholo@sigmasoft.com 79.Sh BUGS 80The returned key is computed based on the device minor number and inode of the 81specified 82.Fa path 83in combination with the lower 8 bits of the given 84.Fa id . 85Thus it is quite possible for the routine to return duplicate keys. 86