getxattr, lgetxattr, fgetxattr — retrieve an extended attribute value
#include <sys/types.h> #include <attr/xattr.h>
ssize_t getxattr( |
const char * | path, |
| const char * | name, | |
| void * | value, | |
| size_t | size); |
ssize_t lgetxattr( |
const char * | path, |
| const char * | name, | |
| void * | value, | |
| size_t | size); |
ssize_t fgetxattr( |
int | fd, |
| const char * | name, | |
| void * | value, | |
| size_t | size); |
Extended attributes are name:value pairs associated with
inodes (files, directories, symbolic links, etc.). They are
extensions to the normal attributes which are associated with
all inodes in the system (i.e., the stat(2) data). A complete
overview of extended attributes concepts can be found in
attr(5).
getxattr() retrieves the
value of the extended
attribute identified by name and associated with the
given path in the
filesystem. The length of the attribute value is returned.
lgetxattr() is identical to
getxattr(), except in the case
of a symbolic link, where the link itself is interrogated,
not the file that it refers to.
fgetxattr() is identical to
getxattr(), only the open file
referred to by fd (as
returned by open(2)) is interrogated in
place of path.
An extended attribute 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.
An empty buffer of 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.
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.
On success, a positive number is returned indicating the
size of the extended attribute value. On failure, −1 is
returned and errno is set
appropriately.
If the named attribute does not exist, or the process has
no access to this attribute, errno is set to ENOATTR.
If the size of the
value buffer is too
small to hold the result, errno
is set to ERANGE.
If extended attributes are not supported by the
filesystem, or are disabled, errno is set to ENOTSUP.
The errors documented for the stat(2) system call are also applicable here.
These system calls have been available on Linux since kernel 2.4; glibc support is provided since version 2.3.
getfattr(1), setfattr(1), listxattr(2), open(2), removexattr(2), setxattr(2), stat(2), attr(5)
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
|
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. |