PRO  read_hdf, file_name, sds_num, data, l
; read hdf file with all data matching field_names of each grid 
; and return it in data_structure
;	See if there is anything there to read

  l = ' '
  DFSD_SETINFO, /RESTART
  DFSD_GETINFO, file_name, NSDS=NumSDS

  IF (sds_num gt numSDS) THEN BEGIN
      print, ' read_hdf: Cannot read sds#', sds_num
      print, ' there are only ', numsds,' scientific data sets in ', file_name
      print, ' returning zero valued fltarr'
      data = fltarr(3,3,3)

      RETURN
  ENDIF

  FOR i=1,sds_num DO BEGIN
      r=0.
      l=0.
      HDF_DFSD_GETINFO, file_name, label = l, dims=d, type=t,range=r
      print,i, l, d, r, t
  ENDFOR
  print, ' read ',l, ' data from ', file_name
  hdf_DFSD_GETDATA, file_name, data

  RETURN
END