.\"-
.\" Copyright (c) 1999 Robert N. M. Watson
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.\"       $FreeBSD: src/share/man/man9/extattr.9,v 1.1.2.4 2001/12/17 11:30:18 ru Exp $
.\"       $DragonFly: src/share/man/man9/extattr.9,v 1.2 2003/06/17 04:37:01 dillon Exp $
.\"
.Dd December 23, 1999
.Os
.Dt EXTATTR 9
.Sh NAME
.Nm extattr
.Nd virtual file system named extended attributes
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.In sys/extattr.h
.Sh DESCRIPTION
Named extended attributes allow additional meta-data to be associated
with vnodes representing files and directories.  The semantics of this
additional data is that of a "name=value" pair, where a name may
be defined or undefined, and if defined, associated with zero or more
bytes of arbitrary binary data.  Reads of this data may return specific
contiguous regions of the meta-data, in the style of
.Xr VOP_READ 9 ,
but writes will replace the entire current "value" associated with
a given name.  As there are a plethora of file systems with differing
extended attributes, availability and functionality of these functions
may be limited, and they should be used with awareness of the underlying
semantics of the supporting file system.  Authorization schemes for
extended attribute data may also vary by file system, as well as
maximum attribute size, and whether or not any or specific new attributes
may be defined.
.Pp
Extended attributes are named using a null-terminated character string.
Depending on file system semantics, this name may or may not be
case-sensitive.  Appropriate vnode extended attribute calls are:
.Xr VOP_GETEXTATTR 9
and
.Xr VOP_SETEXTATTR 9 .
.Sh SEE ALSO
.Xr VFS 9 ,
.Xr VOP_GETEXTATTR 9 ,
.Xr VOP_SETEXTATTR 9
.Sh AUTHORS
This man page was written by
.An Robert Watson .