projects / apple / libc.git / blame
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1 | .\" $OpenBSD: ftok.3,v 1.8 1999/07/07 10:55:36 aaron Exp $ |
| 2 | .\" | |
| 3 | .\" Copyright (c) 1994 SigmaSoft, Th. Lockert <tholo@sigmasoft.com> | |
| 4 | .\" All rights reserved. | |
| 5 | .\" | |
| 6 | .\" Redistribution and use in source and binary forms, with or without | |
| 7 | .\" modification, are permitted provided that the following conditions | |
| 8 | .\" are met: | |
| 9 | .\" 1. Redistributions of source code must retain the above copyright | |
| 10 | .\" notice, this list of conditions and the following disclaimer. | |
| 11 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
| 12 | .\" notice, this list of conditions and the following disclaimer in the | |
| 13 | .\" documentation and/or other materials provided with the distribution. | |
| 14 | .\" 3. The name of the author may not be used to endorse or promote products | |
| 15 | .\" derived from this software without specific prior written permission. | |
| 16 | .\" | |
| 17 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
| 18 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
| 19 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
| 20 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| 21 | .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | |
| 22 | .\" PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; | |
| 23 | .\" OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, | |
| 24 | .\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR | |
| 25 | .\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF | |
| 26 | .\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 27 | .\" | |
| 28 | .Dd June 24, 1994 | |
| 29 | .Dt FTOK 3 | |
| 30 | .Os | |
| 31 | .Sh NAME | |
| 32 | .Nm ftok | |
| 33 | .Nd create IPC indentifier from a pathname | |
| 34 | .Sh SYNOPSIS | |
| 35 | .Fd #include <sys/types.h> | |
| 36 | .Fd #include <sys/ipc.h> | |
| 37 | .Ft key_t | |
| 38 | .Fn ftok "const char *path" "int id" ; | |
| 39 | .Sh DESCRIPTION | |
| 40 | The | |
| 41 | .Fn ftok | |
| 42 | function attempts to create a unique key suitable for use with the | |
| 43 | .Xr msgget 2 , | |
| 44 | .Xr semget 2 | |
| 45 | and | |
| 46 | .Xr shmget 2 | |
| 47 | functions given the | |
| 48 | .Fa path | |
| 49 | of an existing file and a user-selectable | |
| 50 | .Fa id . | |
| 51 | .Pp | |
| 52 | The specified | |
| 53 | .Fa path | |
| 54 | must refer to an existing file that is accessible to the calling process | |
| 55 | or the call will fail. Also, note that links to files will return the | |
| 56 | same key, given the same | |
| 57 | .Fa id . | |
| 58 | Only the 8 least significant bits of | |
| 59 | .Fa id | |
| 60 | are used in the key generation; the rest of the bits are ignored. | |
| 61 | .Sh RETURN VALUES | |
| 62 | The | |
| 63 | .Fn ftok | |
| 64 | function will return (key_t)\-1 if | |
| 65 | .Fa path | |
| 66 | does not exist or if it cannot be accessed by the calling process. | |
| 67 | .Sh SEE ALSO | |
| 68 | .Xr msgget 2 , | |
| 69 | .Xr semget 2 , | |
| 70 | .Xr shmget 2 | |
| 71 | .Sh HISTORY | |
| 72 | The | |
| 73 | .Fn ftok | |
| 74 | function originated with System V and is typically used by programs | |
| 75 | that use the System V IPC routines. | |
| 76 | .Sh AUTHOR | |
| 77 | Thorsten Lockert <tholo@sigmasoft.com> | |
| 78 | .Sh BUGS | |
| 79 | The returned key is computed based on the device and inode of the | |
| 80 | specified | |
| 81 | .Fa path | |
| 82 | in combination with the given | |
| 83 | .Fa id . | |
| 84 | Thus it is quite possible for the routine to return duplicate keys | |
| 85 | given that those fields are not 8- and 16-bit quantities like they | |
| 86 | were on System V based systems where this library routine's ancestors | |
| 87 | were originally created. |