Tracking progress of a SHRINK SPACE

SELECT
  round((extent_cnt - extent#) * 100 / extent_cnt, 2) percent_completed
FROM
  (
    SELECT
      extent_id,
      file_id,
      block_id,
      blocks,
      COUNT(*) OVER () extent_cnt,
      ROW_NUMBER() OVER (ORDER BY extent_id) extent#
    FROM
      dba_extents
    WHERE
      (owner, segment_name) =
        (SELECT
          o.owner, o.object_name
         FROM
           dba_objects o, v$session s
         WHERE
           s.sid = &sid AND
           s.row_wait_obj# = o.object_id AND
           o.object_type = 'TABLE')
  ) e,
  v$session_wait w
WHERE
  w.sid = &sid AND
  w.event = 'db file sequential read' AND
  w.state = 'WAITING' AND
  w.p1 = e.file_id AND
  w.p2 BETWEEN e.block_id AND e.block_id + blocks
;