.\"	$OpenBSD: extattr.3,v 1.5 2003/05/03 18:57:40 jmc Exp $
.\"
.\" Copyright (c) 2001 Dima Dorfman <dd@FreeBSD.org>
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.\" $FreeBSD: extattr.3,v 1.3 2001/10/01 16:09:18 ru Exp $
.\"
.Dd June 24, 2001
.Dt EXTATTR 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 SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <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
function undoes the aforementioned operation,
and converts a human-readable string representing a namespace to a
namespace identifier.
Although a filesystem 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 extattr 2 ,
.Xr getextattr 8 ,
.Xr setextattr 8 ,
.Xr extattr 9
.Sh HISTORY
Extended attribute support was developed as part of the
.Tn TrustedBSD
Project.
It was developed to support security extensions requiring additional labels
to be associated with each file or directory.