1.\"- 2.\" Copyright (c) 1999, 2000, 2001, 2003 Robert N. M. Watson 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd December 23, 1999 29.Os 30.Dt EXTATTR 9 31.Sh NAME 32.Nm extattr 33.Nd virtual file system named extended attributes 34.Sh SYNOPSIS 35.In sys/param.h 36.In sys/vnode.h 37.In sys/extattr.h 38.Sh DESCRIPTION 39Named extended attributes allow additional meta-data to be associated 40with vnodes representing files and directories. 41The semantics of this additional data is that of a "name=value" pair, where 42a name may be defined or undefined, and if defined, associated with zero or 43more bytes of arbitrary binary data. 44Extended attribute names exist within a set of namespaces; each operation 45on an extended attribute is required to provide the namespace to which to 46operation refers. 47If the same name is present in multiple namespaces, the extended attributes 48associated with the names are stored and manipulated independently. 49The following two namespaces are defined universally, although individual 50file systems may implement additional namespaces, or not implement 51these namespaces: 52.Dv EXTATTR_NAMESPACE_USER , 53.Dv EXTATTR_NAMESPACE_SYSTEM . 54The semantics of these attributes are intended to be as follows: user 55attribute data is protected according the normal discretionary 56and mandatory protections associated with the data in the file or 57directory; system attribute data is protected such that appropriate 58privilege is required to directly access or manipulate these attributes. 59.Pp 60Reads of extended attribute data may return specific contiguous regions of 61the meta-data, in the style of 62.Xr VOP_READ 9 , 63but writes will replace the entire current "value" associated with 64a given name. 65As there are a plethora of file systems with differing extended attributes, 66availability and functionality of these functions may be limited, and they 67should be used with awareness of the underlying semantics of the supporting 68file system. 69Authorization schemes for extended attribute data may also vary by file 70system, as well as maximum attribute size, and whether or not any or 71specific new attributes may be defined. 72.Pp 73Extended attributes are named using a null-terminated character string. 74Depending on underlying file system semantics, this name may or may not be 75case-sensitive. 76Appropriate vnode extended attribute calls are: 77.Xr VOP_GETEXTATTR 9 , 78.Xr VOP_LISTEXTATTR 9 , 79and 80.Xr VOP_SETEXTATTR 9 . 81.Sh SEE ALSO 82.Xr VFS 9 , 83.Xr VFS_EXTATTRCTL 9 , 84.Xr VOP_GETEXTATTR 9 , 85.Xr VOP_LISTEXTATTR 9 , 86.Xr VOP_SETEXTATTR 9 87.Sh AUTHORS 88This manual page was written by 89.An Robert Watson . 90.Sh BUGS 91In addition, the interface does not provide a mechanism to retrieve 92the current set of available attributes; it has been suggested that 93providing a 94.Dv NULL 95attribute name should cause a list of defined attributes for the passed file 96or directory, but this is not currently implemented. 97