| | 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 |
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| | 24 | .\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| | 25 | .\" |
| | 26 | .\" $FreeBSD: src/lib/libc/gen/ftok.3,v 1.15 2002/10/19 13:33:12 tjr Exp $ |
| | 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 | .In sys/types.h |
| | 37 | .In sys/ipc.h |
| | 38 | .Ft key_t |
| | 39 | .Fn ftok "const char *path" "int id" |
| | 40 | .Sh DESCRIPTION |
| | 41 | The |
| | 42 | .Fn ftok |
| | 43 | function attempts to create a unique key suitable for use with the |
| | 44 | .Xr msgget 3 , |
| | 45 | .Xr semget 2 |
| | 46 | and |
| | 47 | .Xr shmget 2 |
| | 48 | functions given the |
| | 49 | .Fa path |
| | 50 | of an existing file and a user-selectable |
| | 51 | .Fa id . |
| | 52 | .Pp |
| | 53 | The specified |
| | 54 | .Fa path |
| | 55 | must specify an existing file that is accessible to the calling process |
| | 56 | or the call will fail. Also, note that links to files will return the |
| | 57 | same key, given the same |
| | 58 | .Fa id . |
| | 59 | .Sh RETURN VALUES |
| | 60 | The |
| | 61 | .Fn ftok |
| | 62 | function will return -1 if |
| | 63 | .Fa path |
| | 64 | does not exist or if it cannot be accessed by the calling process. |
| | 65 | .Sh SEE ALSO |
| | 66 | .Xr semget 2 , |
| | 67 | .Xr shmget 2 , |
| | 68 | .Xr msgget 3 |
| | 69 | .Sh HISTORY |
| | 70 | The |
| | 71 | .Fn ftok |
| | 72 | function originates with System V and is typically used by programs |
| | 73 | that use the System V IPC routines. |
| | 74 | .Sh AUTHORS |
| | 75 | .An Thorsten Lockert Aq tholo@sigmasoft.com |
| | 76 | .Sh BUGS |
| | 77 | The returned key is computed based on the device minor number and inode of the |
| | 78 | specified |
| | 79 | .Fa path |
| | 80 | in combination with the lower 8 bits of the given |
| | 81 | .Fa id . |
| | 82 | Thus it is quite possible for the routine to return duplicate keys. |
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