llistxattr (2) Linux Manual Page
NAME
listxattr, llistxattr, flistxattr – list extended attribute names
SYNOPSIS
#include <sys/types.h>
#include <sys/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 fd, char *list, size_t size);
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).
listxattr() retrieves the list of extended attribute names associated with the given path in the filesystem. The retrieved list is placed in list, a caller-allocated buffer whose size (in bytes) is specified in the argument size. 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 referred to by fd (as returned by open(2)) is interrogated in place of path.
A single 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.
If size is specified as zero, these calls return the current size of the list of extended attribute names (and leave list 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 set of extended attributes may change between the two calls, so that it is still necessary to check the return status from the second call.)
Example
The list of names is returned as an unordered array of null-terminated character strings (attribute names are separated by null bytes (‘