Extended attributes extend the basic attributes associated with files and directories in the file system. They are stored as name:data pairs
associated with file system objects (files, directories, symlinks, etc).
listxattr() retrieves a list of names of extended attributes associated with the given path in the file system.
namebuf is a data buffer of size bytes for the names of the extended attributes associated with path. The extended attribute names are sim-
ple NULL-terminated UTF-8 strings and are returned in arbitrary order. No extra padding is provided between names in the buffer. The list
will only include names of extended attributes to which the calling process has access. The function returns the size of the list of names.
options controls how the attribute list is generated:
XATTR_NOFOLLOW do not follow symbolic links. listxattr() normally lists attributes of the target of path if it is a symbolic link. With
this option, listxattr() will list attributes of the link itself.
listxattr() and flistxattr() will list HFS Plus Compression extended attribute(s) (if present) for the file referred to by
path or fd.
If namebuf is set to NULL, the function returns the size of the list of extended attribute names. This facility can be used to determine the
size of a buffer sufficiently large to hold the names of the attributes currently associated with path.
flistxattr() is identical to listxattr(), except that it returns the list of extended attribute names associated with the open file refer-
enced by file descriptor fd.
On success, the size of the extended attribute name list is returned. If no accessible extended attributes are associated with the given
path or fd, the function returns zero. On failure, -1 is returned and the global variable errno is set as follows.
[ENOTSUP] The file system does not support extended attributes or has the feature disabled.
[ERANGE] namebuf (as indicated by size) is too small to hold the list of names.
[EPERM] path or fd refer to a file system object that does not support extended attributes. For example, resource forks don't
support extended attributes.
[ENOTDIR] A component of path 's prefix is not a directory.
[ENAMETOOLONG] name exceeds XATTR_MAXNAMELEN UTF-8 bytes, or a component of path exceeds NAME_MAX characters, or the entire path exceeds
[EACCES] Search permission is denied for a component of path or permission is denied to read the list of attributes from this file.
[ELOOP] Too many symbolic links were encountered resolving path.
[EFAULT] path points to an invalid address.
[EIO] An I/O error occurred.
[EINVAL] options does not make sense.