Save a value to a CSV file

save-csv-array-idl

; We have an array of values to save to a CSV file
  delim = ','
  output_file = 'orbits.txt'
  
  data_to_save=make_array(2, /string, value=-999)

  data_to_save[0] = string(orbit_syear)
  data_to_save[1] = string(orbit_sdoy, format='(I03)')
  data_to_save[2] = string(orbit, format='(I05)')
 
  s=''
  lim = n_elements(data_to_save)
  for i = 0, lim - 1 do begin
    if i lt lim then begin
      s = s + data_to_save[i] + delim
    endif else begin
      s = s + data_to_save[i]
    endelse
  endfor
          
; Write out info to rundates-aux file
  openw, 1, output_file, /append      
  printf, 1, s
  close, 1