[apple/libc.git] / gen / ftok.3

.\" 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: src/lib/libc/gen/ftok.3,v 1.14 2001/10/01 16:08:50 ru Exp $
.Dd June 24, 1994
.Os
.Dt FTOK 3
.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
.Bf -symbolic
This function is available from the compatibility library, libcompat.
.Ef
The
.Fn ftok
function attempts to create a unique key suitable for use with the
.Xr msgget 3 ,
.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 3
.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.
Commit	Line	Data
e9ce8d39 A	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	.\"
5b2abdfb	26	.\" $FreeBSD: src/lib/libc/gen/ftok.3,v 1.14 2001/10/01 16:08:50 ru Exp $
e9ce8d39	27	.Dd June 24, 1994
e9ce8d39	28	.Os
5b2abdfb	29	.Dt FTOK 3
e9ce8d39 A	30	.Sh NAME
e9ce8d39 A	31	.Nm ftok
5b2abdfb A	32	.Nd create IPC identifier from path name
	33	.Sh LIBRARY
	34	.Lb libc
e9ce8d39	35	.Sh SYNOPSIS
5b2abdfb A	36	.In sys/types.h
5b2abdfb A	37	.In sys/ipc.h
e9ce8d39	38	.Ft key_t
5b2abdfb	39	.Fn ftok "const char *path" "int id"
e9ce8d39	40	.Sh DESCRIPTION
5b2abdfb A	41	.Bf -symbolic
	42	This function is available from the compatibility library, libcompat.
	43	.Ef
e9ce8d39 A	44	The
	45	.Fn ftok
	46	function attempts to create a unique key suitable for use with the
5b2abdfb	47	.Xr msgget 3 ,
e9ce8d39 A	48	.Xr semget 2
	49	and
	50	.Xr shmget 2
	51	functions given the
	52	.Fa path
	53	of an existing file and a user-selectable
	54	.Fa id .
	55	.Pp
	56	The specified
	57	.Fa path
5b2abdfb	58	must specify an existing file that is accessible to the calling process
e9ce8d39 A	59	or the call will fail. Also, note that links to files will return the
	60	same key, given the same
	61	.Fa id .
e9ce8d39 A	62	.Sh RETURN VALUES
	63	The
	64	.Fn ftok
5b2abdfb	65	function will return -1 if
e9ce8d39 A	66	.Fa path
	67	does not exist or if it cannot be accessed by the calling process.
	68	.Sh SEE ALSO
e9ce8d39	69	.Xr semget 2 ,
5b2abdfb A	70	.Xr shmget 2 ,
5b2abdfb A	71	.Xr msgget 3
e9ce8d39 A	72	.Sh HISTORY
	73	The
	74	.Fn ftok
5b2abdfb	75	function originates with System V and is typically used by programs
e9ce8d39	76	that use the System V IPC routines.
5b2abdfb A	77	.Sh AUTHORS
5b2abdfb A	78	.An Thorsten Lockert Aq tholo@sigmasoft.com
e9ce8d39	79	.Sh BUGS
5b2abdfb	80	The returned key is computed based on the device minor number and inode of the
e9ce8d39 A	81	specified
e9ce8d39 A	82	.Fa path
5b2abdfb	83	in combination with the lower 8 bits of the given
e9ce8d39	84	.Fa id .
5b2abdfb	85	Thus it is quite possible for the routine to return duplicate keys.