;+
; NAME:
;  rd_2_position
; PURPOSE: (one line)
;  Write the beam positions
; DESCRIPTION:
;  Write a short log
;  tables/YYMMDD_2_position_SETNO.txt
; CATEGORY:
;  NIRES reduction
; CALLING SEQUENCE:
;  wr_2_position, datestr, set
; INPUTS:
;  datestr: string (YYMMDD)
;  sets: array of set structures
;  nset: number of sets
; OUTPUTS:
; SIDE EFFECTS:
;  write tables/YYMMDD_2_position_SETNO.txt
; RESTRICTIONS:
;  tables directory must exist
; PROCEDURE:
; MODIFICATION HISTORY:
;  Written 2021 Dec 30, by Leslie Young, SwRI
;-
function rd_2_position, datestr, setno, framenum, object, dpatname, beam_override

  fn = 'tables/'+datestr+'_2_position_'+string(setno, form='(I03)')+'.txt'
  if not isfile(fn) then return, -1
  
  formp = '(I5, X,A-12, X, A-7, 3X, I1, 3X,I1, 2X, F7.3, X, F7.3,2X, F7.3,X,F7.3,X,F7.3, 2X,A10, A10)'

  readfmt, fn, formp, framenum, object, dpatname, dpatipos, dpatnpos, xoffset, yoffset, xi_arcsec, eta_arcsec, d, beam, beam_override,$
           skip=2, /silent
  nsets = n_elements(beam)
  beam = strtrim(beam,2)
  beam_override = strtrim(beam_override,2)
  if nsets ne (file_lines(fn)-2) then return, -1
  return, nsets
end