listxattr, llistxattr, flistxattr - list extended
attribute names
SYNOPSIS
#include <sys/types.h>
#include <attr/xattr.h>
ssize_t listxattr (const char *path,
char *list, size_t size);
ssize_t llistxattr (const char *path,
char *list, size_t size);
ssize_t flistxattr (int filedes,
char *list, 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).
listxattr retrieves the list of extended attribute names
associated with the given path in the filesystem. The
list is the set of (NULL-terminated) names, one after the
other. Names of extended attributes to which the calling
process does not have access may be omitted from the list.
The length of the attribute name list is returned.
llistxattr is identical to listxattr, except in the case
of a symbolic link, where the list of names of extended
attributes associated with the link itself is retrieved,
not the file that it refers to.
flistxattr is identical to listxattr, only the open file
pointed to by filedes (as returned by open(2)) is interro
gated in place of path.
A single extended attribute name is a simple NULL-termi
nated string. The name includes a namespace prefix -
there may be several, disjoint namespaces associated with
an individual inode.
An empty buffer of size zero can be passed into these
calls to return the current size of the list of extended
attribute names, which can be used to estimate the size of
a buffer which is sufficiently large to hold the list of
names.
EXAMPLES
The list of names is returned as an unordered array of
NULL-terminated character strings (attribute names are
separated by NULL characters), like this:
Filesystems like ext2, ext3 and XFS which implement POSIX
ACLs using extended attributes, might return a list like
this:
system.posix_acl_access\0system.posix_acl_default\0
RETURN VALUE
On success, a positive number is returned indicating the
size of the extended attribute name list. On failure, -1
is returned and errno is set appropriately.
If the size of the list buffer is too small to hold the
result, errno is set to ERANGE.
If extended attributes are not supported by the filesys
tem, 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@computer.org> 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), getxattr(2),
setxattr(2), removexattr(2), and attr(5).
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