function list_hdf_labels, file_name, COUNT=count
; return list of strings of labels in hdf file 
; if count is a named variable it returns the number of data sets 
  list = ''
  l = ' '
  print, 'list:', file_name
  dummy = FindFile(file_name , COUNT = exist)  
  if dummy(0) eq '' then BEGIN
      print, 'read_hdf: the file "', file_name, '" does not exist!'
      RETURN, list
  ENDIF
  sd_id = HDF_SD_START(file_name[0], /READ)
  HDF_SD_FILEINFO, sd_id, NumSDS, attributes

  count = 0L
  n = 0L
  FOR i=1L,NumSDS DO BEGIN
      r=0.
      l=0.
      sds_id = HDF_SD_SELECT(sd_id, n)
      WHILE (HDF_SD_ISCOORDVAR(sds_id)) DO BEGIN
        HDF_SD_ENDACCESS, sds_id
        n = n + 1
        sds_id = HDF_SD_SELECT(sd_id, n)
      ENDWHILE
      n = n + 1
      HDF_SD_GETINFO, sds_id, label = l, dims=d, type=t
      print, i, ' ', l, size(l)
      if (l NE '') then begin 
          list = [list, l]
          count = count + 1
      endif
      HDF_SD_ENDACCESS, sds_id

  ENDFOR
  HDF_SD_END, sd_id
  if (N_ELEMENTS(list) gt 1) THEN $
    RETURN, list[1:*] $
  ELSE BEGIN
      print, 'having trouble reading labels in ',file_name
      print, 'returning dummy list'
      list = 'No labels read ...;
  ENDELSE
END