.\"	$NetBSD: extattr_namespace_to_string.3,v 1.1 2011/12/16 12:46:00 wiz Exp $
.\"
.\" Copyright (c) 2001 Dima Dorfman <dd@FreeBSD.org>
.\" Copyright (c) 2011 Emmanuel Dreyfus <manu@NetBSD.org>
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.\" FreeBSD: src/lib/libc/posix1e/extattr.3,v 1.5 2002/12/12 17:25:53 ru Exp
.\"
.Dd December 16, 2011
.Dt EXTATTR_NAMESPACE_TO_STRING 3
.Os
.Sh NAME
.Nm extattr_namespace_to_string ,
.Nm extattr_string_to_namespace
.Nd convert an extended attribute namespace identifier to a string and vice versa
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/extattr.h
.Ft int
.Fn extattr_namespace_to_string "int attrnamespace" "char **string"
.Ft int
.Fn extattr_string_to_namespace "const char *string" "int *attrnamespace"
.Sh DESCRIPTION
The
.Fn extattr_namespace_to_string
function converts a VFS extended attribute identifier to a human-readable
string.
The
.Fn extattr_string_to_namespace
converts a human-readable string representing a namespace to a
namespace identifier.
Although a file system may implement arbitrary namespaces,
these functions only support the
.Dv EXTATTR_NAMESPACE_USER
.Pq Dq user
and
.Dv EXTATTR_NAMESPACE_SYSTEM
.Pq Dq system
namespaces,
which are defined in
.Xr extattr 9 .
.Pp
These functions are meant to be used in error reporting and other
interactive tasks.
For example,
instead of printing the integer identifying an extended attribute in
an error message,
a program might use
.Fn extattr_namespace_to_string
to obtain a human-readable representation.
Likewise,
instead of requiring a user to enter the integer representing a namespace,
an interactive program might ask for a name and use
.Fn extattr_string_to_namespace
to get the desired identifier.
.Sh RETURN VALUES
If any of the calls are unsuccessful, the value \-1 is returned
and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINVAL
The requested namespace could not be identified.
.El
.Sh SEE ALSO
.Xr getextattr 1 ,
.Xr extattr_get_file 2 ,
.Xr extattr_copy_file 3 ,
.Xr extattr 9
.Sh HISTORY
Extended attribute support was developed as part of the
.Tn TrustedBSD
Project, and introduced in
.Fx 5.0
and
.Nx 3.0 .
It was developed to support security extensions requiring additional labels
to be associated with each file or directory.