Set an extended attribute value
#include <sys/types.h> #include <attr/xattr.h> int setxattr (const char *path, const char *name, \t\t\t const void *value, size_t size, int flags); int lsetxattr (const char *path, const char *name, \t\t\t const void *value, size_t size, int flags); int fsetxattr (int filedes, const char *name, \t\t\t const void *value, size_t size, int flags);
Extended attributes are name:.Ivalue 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).
setxattr sets the value of the extended attribute identified by name and associated with the given path in the filesystem. The size of the value must be specified.
lsetxattr is identical to setxattr, except in the case of a symbolic link, where the extended attribute is set on the link itself, not the file that it refers to.
fsetxattr is identical to setxattr, only the extended attribute is set on the open file pointed to by filedes (as returned by open(2)) in place of path.
An extended attribute name is a simple 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 of specified length.
The flags parameter can be used to refine the semantics of the operation. XATTR_CREATE specifies a pure create, which fails if the named attribute exists already. XATTR_REPLACE specifies a pure replace operation, which fails if the named attribute does not already exist. By default (no flags), the extended attribute will be created if need be, or will simply replace the value if the attribute exists.
On success, zero is returned. On failure, -1 is returned and errno is set appropriately.
If XATTR_CREATE is specified, and the attribute exists already, errno is set to EEXIST. If XATTR_REPLACE is specified, and the attribute does not exist, errno is set to ENOATTR.
If there is insufficient space remaining to store the extended attribute, errno is set to either ENOSPC, or EDQUOT if quota enforcement was the cause.
If extended attributes are not supported by the filesystem, or are disabled, errno is set to ENOTSUP.
The errors documented for the stat(2) system call are also applicable here.