NAME
getxattr, lgetxattr, fgetxattr - retrieve an extended attribute value
SYNOPSIS
#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 filedes, const char *name,
void *value, size_t size);
DESCRIPTION
Extended attributes are name: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
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 pointed to by
filedes (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.
RETURN VALUE
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.
AUTHORS
Andreas Gruenbacher, <a.gruenbacher@bestbits.at> and the SGI XFS
development team, <linux-xfs@oss.sgi.com>. Please send any bug reports
or comments to these addresses.
SEE ALSO
getfattr(1), setfattr(1), open(2), stat(2), setxattr(2), listxattr(2),
removexattr(2), and attr(5).