int zfs_for_each(int, char **, int options, zfs_type_t,
zfs_sort_column_t *, zprop_list_t **, int, zfs_iter_f, void *);
int zfs_add_sort_column(zfs_sort_column_t **, const char *, boolean_t);
void zfs_free_sort_columns(zfs_sort_column_t *);
int zfs_for_each(int, char **, int options, zfs_type_t,
zfs_sort_column_t *, zprop_list_t **, int, zfs_iter_f, void *);
int zfs_add_sort_column(zfs_sort_column_t **, const char *, boolean_t);
void zfs_free_sort_columns(zfs_sort_column_t *);