Originální popis anglicky:
getxattr, lgetxattr, fgetxattr - retrieve an extended attribute value
Návod, kniha: Linux Programmer's Manual
#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);
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.
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.
Andreas Gruenbacher, <
a.gruenbacher@computer.org> and the SGI XFS
development team, <
linux-xfs@oss.sgi.com>. Please send any bug
reports or comments to these addresses.
getfattr(1),
setfattr(1),
listxattr(2),
open(2),
removexattr(2),
setxattr(2),
stat(2),
attr(5)
