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.\" $Id: ftok.3,v 1.1 1994/06/26 16:24:57 jtc Exp $ 27.Dd June 24, 1994 28.Os 29.Dt ftok 3 30.Sh NAME 31.Nm ftok 32.Nd create IPC indentifier from path name 33.Sh SYNOPSIS 34.Fd #include <sys/types.h> 35.Fd #include <sys/ipc.h> 36.Ft key_t 37.Fn ftok "const char *path" "char id" ; 38.Sh DESCRIPTION 39The 40.Fn ftok 41function attempts to create a unique key suitable for use with the 42.Xr msgget 2 , 43.Xr semget 2 44and 45.Xr shmget 2 46functions given the 47.Fa path 48of an existing file and a user-selectable 49.Fa id . 50.Pp 51The specified 52.Fa path 53must specify an existing file that is accessible to the calling process 54or the call will fail. Also, note that links to files will return the 55same key, given the same 56.Fa id . 57.Sh RETURN VALUES 58The 59.Fn ftok 60function will return -1 if 61.Fa path 62does not exist or if it cannot be accessed by the calling process. 63.Sh SEE ALSO 64.Xr msgget 2 , 65.Xr semget 2 , 66.Xr shmget 2 67.Sh HISTORY 68The 69.Fn ftok 70function originate with System V and is typically used by programs 71that use the System V IPC routines. 72.Sh AUTHOR 73.Bl -tag 74Thorsten Lockert <tholo@sigmasoft.com> 75.El 76.Sh BUGS 77The returned key is computed based on the device and inode of the 78specified 79.Fa path 80in combination with the given 81.Fa id . 82Thus is is quite possible for the routine to return duplicate keys 83given that those fields are not 8- and 16-bit quantities like they 84were on System V based systems where this library routine's ancestor 85were originally created. 86