File: attr_get.3

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.\" Copyright (C) 2001, 2002, 2003, 2006, 2008 Silicon Graphics, Inc.
.\" All rights reserved.
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual.  If not, see
.\" <http://www.gnu.org/licenses/>.
.\"
.TH ATTR_GET 3 "Extended Attributes" "Dec 2001" "XFS Compatibility API"
.SH NAME
attr_get, attr_getf \- get the value of a user attribute of a filesystem object
.SH C SYNOPSIS
.PP
.sp
.nf
.B #include <attr/attributes.h>
.sp
.B "int attr_get (const char *\f2path\f3, const char *\f2attrname\f3, "
.B "              char *\f2attrvalue\f3, int *\f2valuelength\f3, int \f2flags\f3);"
.PP
.B "int attr_getf (int \f2fd\f3, const char *\f2attrname\f3, "
.B "               char *\f2attrvalue\f3, int *\f2valuelength\f3, int \f2flags\f3);"
.Op
.SH DESCRIPTION
The
.B attr_get
and
.B attr_getf
functions provide a way to retrieve the value of an attribute.
.P
.I Path\^
points to a path name for a filesystem object, and
.I fd\^
refers to the file descriptor associated with a file.
If the attribute
.I attrname
exists, the value associated with it will be copied into the
.I attrvalue
buffer.
The
.I valuelength
argument is an input/output argument that on the call to
.B attr_get
should contain the maximum size of attribute value the
process is willing to accept.
On return, the
.I valuelength
will have been modified to show the actual size of the
attribute value returned.
The
.I flags
argument can contain the following symbols bitwise OR'ed together:
.TP
.SM
\%ATTR_ROOT
Look for
.I attrname
in the
.B root
address space, not in the
.B user
address space.
(limited to use by super-user only)
.TP
.SM
\%ATTR_DONTFOLLOW
Do not follow symbolic links when resolving a
.I path
on an
.B attr_get
function call.
The default is to follow symbolic links.
.PP
.B attr_get
will fail if one or more of the following are true:
.TP 17
.SM
\%[ENOATTR]
The attribute name given is not associated with the indicated
filesystem object.
.TP
.SM
\%[E2BIG]
The value of the given attribute is too large to fit into the buffer.
The integer that the
.I valuelength
argument points to has been modified to show the actual number
of bytes that would be required to store the value of that attribute.
.TP
.SM
\%[ENOENT]
The named file does not exist.
.TP
.SM
\%[EPERM]
The effective user
.SM ID
does not match the owner of the file and the effective user
.SM ID
is not super-user.
.TP
.SM
\%[ENOTDIR]
A component of the path prefix is not a directory.
.TP
.SM
\%[EACCES]
Search permission is denied on a component of the path prefix.
.TP
.SM
\%[EINVAL]
A bit was set in the
.I flag
argument that is not defined for this system call.
.TP
.SM
\%[EFAULT]
.I Path,
.I attrname,
.I attrvalue,
or
.I valuelength
points outside the allocated address space of the process.
.TP
.SM
\%[ELOOP]
A path name lookup involved too many symbolic links.
.TP
.SM
\%[ENAMETOOLONG]
The length of
.I path
exceeds
.SM
.RI { MAXPATHLEN },
or a pathname component is longer than
.SM
.RI { MAXNAMELEN }.
.PP
.B attr_getf\^
will fail if:
.TP 15
.SM
\%[ENOATTR]
The attribute name given is not associated with the indicated
filesystem object.
.TP
.SM
\%[E2BIG]
The value of the given attribute is too large to fit into the buffer.
The integer that the
.I valuelength
argument points to has been modified to show the actual numnber
of bytes that would be required to store the value of that attribute.
.TP
.SM
\%[EINVAL]
A bit was set in the
.I flag
argument that is not defined for this system call,
or
.I fd\^
refers to a socket, not a file.
.TP
.SM
\%[EFAULT]
.I Attrname,
.I attrvalue,
or
.I valuelength
points outside the allocated address space of the process.
.TP
.SM
\%[EBADF]
.I Fd\^
does not refer to a valid descriptor.
.SH "DIAGNOSTICS"
On success, zero is returned.  On error, \-1 is returned, and
.I errno
is set appropriately.
.SH "SEE ALSO"
.BR attr (1),
.BR attr_list (3),
.BR attr_multi (3),
.BR attr_remove (3),
.BR attr_set (3)