[apple/libc.git] / gen / FreeBSD / 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 1.17 2009/07/13 12:53:43 trasz Exp $
.Dd July 9, 2009
.Os
.Dt FTOK 3
.Sh NAME
.Nm ftok
.Nd create IPC identifier from path name
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/ipc.h
.Ft key_t
.Fn ftok "const char *path" "int id"
.Sh DESCRIPTION
The
.Fn ftok
function attempts to create a unique key suitable for use with the
.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 LEGACY SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Pp
The include file
.In sys/types.h
is necessary.
.Sh SEE ALSO
.Xr semget 2 ,
.Xr shmget 2 ,
.Xr compat 5
.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	.\"
1f2f436a A	26	.\" $FreeBSD: src/lib/libc/gen/ftok.3,v 1.17 2009/07/13 12:53:43 trasz Exp $
1f2f436a A	27	.Dd July 9, 2009
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	36	.In sys/ipc.h
e9ce8d39	37	.Ft key_t
5b2abdfb	38	.Fn ftok "const char *path" "int id"
e9ce8d39 A	39	.Sh DESCRIPTION
	40	The
	41	.Fn ftok
	42	function attempts to create a unique key suitable for use with the
ad3c9f2a	43	.Xr semget 2 ,
e9ce8d39 A	44	and
e9ce8d39 A	45	.Xr shmget 2
ad3c9f2a	46	functions, given the
e9ce8d39 A	47	.Fa path
	48	of an existing file and a user-selectable
	49	.Fa id .
	50	.Pp
	51	The specified
	52	.Fa path
5b2abdfb	53	must specify an existing file that is accessible to the calling process
3d9156a7 A	54	or the call will fail.
3d9156a7 A	55	Also, note that links to files will return the
e9ce8d39 A	56	same key, given the same
e9ce8d39 A	57	.Fa id .
e9ce8d39 A	58	.Sh RETURN VALUES
	59	The
	60	.Fn ftok
5b2abdfb	61	function will return -1 if
e9ce8d39 A	62	.Fa path
e9ce8d39 A	63	does not exist or if it cannot be accessed by the calling process.
ad3c9f2a A	64	.Sh LEGACY SYNOPSIS
	65	.Fd #include <sys/types.h>
	66	.Fd #include <sys/ipc.h>
	67	.Pp
	68	The include file
	69	.In sys/types.h
	70	is necessary.
e9ce8d39	71	.Sh SEE ALSO
e9ce8d39	72	.Xr semget 2 ,
5b2abdfb	73	.Xr shmget 2 ,
ad3c9f2a	74	.Xr compat 5
e9ce8d39 A	75	.Sh HISTORY
	76	The
	77	.Fn ftok
5b2abdfb	78	function originates with System V and is typically used by programs
e9ce8d39	79	that use the System V IPC routines.
5b2abdfb A	80	.Sh AUTHORS
5b2abdfb A	81	.An Thorsten Lockert Aq tholo@sigmasoft.com
e9ce8d39	82	.Sh BUGS
ad3c9f2a A	83	The returned key is computed based on the device minor number and inode
	84	of the specified
	85	.Fa path ,
5b2abdfb	86	in combination with the lower 8 bits of the given
e9ce8d39	87	.Fa id .
ad3c9f2a	88	Thus, it is quite possible for the routine to return duplicate keys.