- Sur linux, il faut explicitement enabler les xattr:
mount -o remount,user_xattr /home
ou
/dev/sda7 /home reiserfs acl,user_xattr 1 2
FreeBSD
--------------------------
#include <sys/types.h>
#include <sys/extattr.h>
#include <sys/uio.h>
ssize_t extattr_get_fd(int fd, int attrnamespace, const char *attrname,
void *data, size_t nbytes);
int extattr_set_fd(int fd, int attrnamespace, const char *attrname,
const void *data, size_t nbytes);
int extattr_delete_fd(int fd, int attrnamespace, const char *attrname);
ssize_t extattr_list_fd(int fd, int attrnamespace, void *data, size_t nbytes);
ssize_t extattr_get_file(const char *path, int attrnamespace,
const char *attrname, void *data, size_t nbytes);
etc.
ssize_t extattr_get_link(const char *path, int attrnamespace,
const char *attrname, void *data, size_t nbytes);
etc.
- Namespaces are separate, not part of the name. 2 defined by default:
EXTATTR_NAMESPACE_USER, EXTATTR_NAMESPACE_SYSTEM
- _get_() can get size by passing null buffer. Can also apparently read in
multiple chunks ?? to be checked.
Linux
--------------------------------
#include <sys/types.h>
#include <attr/xattr.h>
ssize_t fgetxattr(int fd, const char *name, void *value, size_t size);
ssize_t flistxattr(int fd, char *list, size_t size);
int fsetxattr(int fd, const char *name, const void *value, size_t size,
int flags);
int fremovexattr(int fd, const char *name);
ssize_t getxattr(const char *path, const char *name, void *value, size_t size);
etc.
int lsetxattr(const char *path, const char *name, const void *value,
size_t size, int flags);
etc.
- The namespace is part of the name "user.xxx.yy". Four predefined spaces:
security, system, trusted, user. So permissions depend on the name prefix.
The system namespace is used for implementing acls
- get() can get size by passing buffer of size 0
- The flags to "set" are XATTR_CREATE or XATTR_REPLACE. Default 0 means
create or replace as appropriate.
MacOSX
-----------------------------
#include <sys/xattr.h>
ssize_t fgetxattr(int fd, const char *name, void *value, size_t size,
u_int32_t position, int options);
int fsetxattr(int fd, const char *name, void *value, size_t size,
u_int32_t position, int options);
int fremovexattr(int fd, const char *name, int options);
ssize_t flistxattr(int fd, char *namebuf, size_t size, int options);
ssize_t getxattr(const char *path, const char *name, void *value, size_t size,
u_int32_t position, int options);
etc.
- position is only used with the resource fork, else set to 0
- names are UTF-8. Max size
- get with size 0 returns actual size.
- options: XATTR_NOFOLLOW (all), XATTR_CREATE/XATTR_REPLACE (setxattr()
not set->either)
http://arstechnica.com/reviews/os/macosx-10-4.ars/7:
Apple recommends the use of a reverse-DNS naming scheme (e.g.,
com.apple.itunes.artist), but with the dots replaced with underscores
in order to avoid conflicting with the namespace convention used by
Cocoa's key/value coding system.
- Max name size 128 ?
There are apparently no predefined namespaces and no restrictions on names
Solaris
---------