получить расширенное значение атрибута (retrieve an extended attribute value)
Имя (Name)
getxattr, lgetxattr, fgetxattr - retrieve an extended attribute
value
Синопсис (Synopsis)
#include <sys/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);
Описание (Description)
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 xattr(7).
getxattr() retrieves the value of the extended attribute
identified by name and associated with the given path in the
filesystem. The attribute value is placed in the buffer pointed
to by value; size specifies the size of that buffer. The return
value of the call is the number of bytes placed in value.
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 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
that was assigned using setxattr(2).
If size is specified as zero, these calls return the current size
of the named extended attribute (and leave value unchanged).
This can be used to determine the size of the buffer that should
be supplied in a subsequent call. (But, bear in mind that there
is a possibility that the attribute value may change between the
two calls, so that it is still necessary to check the return
status from the second call.)
Возвращаемое значение (Return value)
On success, these calls return a nonnegative value which is the
size (in bytes) of the extended attribute value. On failure, -1
is returned and errno is set to indicate the error.
Ошибки (Error)
E2BIG The size of the attribute value is larger than the maximum
size allowed; the attribute cannot be retrieved. This can
happen on filesystems that support very large attribute
values such as NFSv4, for example.
ENODATA
The named attribute does not exist, or the process has no
access to this attribute.
ENOTSUP
Extended attributes are not supported by the filesystem,
or are disabled.
ERANGE The size of the value buffer is too small to hold the
result.
In addition, the errors documented in stat(2) can also occur.
Версии (Versions)
These system calls have been available on Linux since kernel 2.4;
glibc support is provided since version 2.3.
Стандарты (Conforming to)
These system calls are Linux-specific.
Примеры (Examples)
See listxattr(2).
Смотри также (See also)
getfattr(1), setfattr(1), listxattr(2), open(2), removexattr(2),
setxattr(2), stat(2), symlink(7), xattr(7)
