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.\"
.\" Extended attributes system calls manual pages
.\"
.\" (C) Andreas Gruenbacher, February 2001
.\" (C) Silicon Graphics Inc, September 2001
.\"
.\" 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, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.TH GETXATTR 2 "Extended Attributes" "Dec 2001" "System calls"
.SH NAME
getxattr, lgetxattr, fgetxattr \- retrieve an extended attribute value
.SH SYNOPSIS
.fam C
.nf
.B #include <sys/types.h>
.B #include <attr/xattr.h>
.sp
.BI "ssize_t getxattr (const char\ *" path ", const char\ *" name ",
.BI "\t\t\t\t void\ *" value ", size_t " size );
.BI "ssize_t lgetxattr (const char\ *" path ", const char\ *" name ",
.BI "\t\t\t\t void\ *" value ", size_t " size );
.BI "ssize_t fgetxattr (int " filedes ", const char\ *" name ",
.BI "\t\t\t\t void\ *" value ", size_t " size );
.fi
.fam T
.SH DESCRIPTION
Extended attributes are
.IR name :\c
.I value
pairs associated with inodes (files, directories, symlinks, etc).
They are extensions to the normal attributes which are associated
with all inodes in the system (i.e. the
.BR stat (2)
data).
A complete overview of extended attributes concepts can be found in
.BR attr (5).
.PP
.B getxattr
retrieves the
.I value
of the extended attribute identified by
.I name
and associated with the given
.I path
in the filesystem.
The length of the attribute
.I value
is returned.
.PP
.B lgetxattr
is identical to
.BR getxattr ,
except in the case of a symbolic link, where the link itself is
interrogated, not the file that it refers to.
.PP
.B fgetxattr
is identical to
.BR getxattr ,
only the open file pointed to by
.I filedes
(as returned by
.BR open (2))
is interrogated in place of
.IR path .
.PP
An extended attribute
.I name
is a simple NULL-terminated string.
The name includes a namespace prefix \- there may be several, disjoint
namespaces associated with an individual inode.
The value of an extended attribute is a chunk of arbitrary textual or
binary data of specified length.
.PP
An empty buffer of
.I size
zero can be passed into these calls to return the current size of the
named extended attribute, which can be used to estimate the size of a
buffer which is sufficiently large to hold the value associated with
the extended attribute.
.PP
The interface is designed to allow guessing of initial buffer
sizes, and to enlarge buffers when the return value indicates
that the buffer provided was too small.
.SH RETURN VALUE
On success, a positive number is returned indicating the size of the
extended attribute value.
On failure, \-1 is returned and
.I errno
is set appropriately.
.PP
If the named attribute does not exist, or the process has no access to
this attribute,
.I errno
is set to ENOATTR.
.PP
If the
.I size
of the
.I value
buffer is too small to hold the result,
.I errno
is set to ERANGE.
.PP
If extended attributes are not supported by the filesystem, or are disabled,
.I errno
is set to ENOTSUP.
.PP
The errors documented for the
.BR stat (2)
system call are also applicable here.
.SH AUTHORS
Andreas Gruenbacher,
.RI < a.gruenbacher@computer.org >
and the SGI XFS development team,
.RI < linux-xfs@oss.sgi.com >.
Please send any bug reports or comments to these addresses.
.SH SEE ALSO
.BR getfattr (1),
.BR setfattr (1),
.BR open (2),
.BR stat (2),
.BR setxattr (2),
.BR listxattr (2),
.BR removexattr (2),
and
.BR attr (5).
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