read_csv_item Function

  function read_csv_item(index, file_id) result(column)
    ! Return the index'th item from the next line of file_id and move to next line
    ! Raise error if number of items not found
    integer, intent(in) :: index, file_id
    character(len=read_line_buffer_size) :: column
    character(len=read_line_buffer_size) buffer
    character(len=read_line_buffer_size*2) scanpart
    logical column_not_found
    integer ic, iostat, ie

    scanpart = ''
    column_not_found = .True.
    ic = 0
    iostat = 0
    do while (column_not_found .and. iostat == 0)
      read(file_id, "(a)", advance="no", iostat=iostat) buffer
      scanpart = trim(adjustl(scanpart))//buffer
      ie = 1
      do while (column_not_found .and. ie > 0)
        ie = scan(scanpart, ",")
        if (ie > 0) then  ! comma found
          ic = ic + 1
          column_not_found = ic /= index
          if (.not. column_not_found) column = trim(adjustl(scanpart(:ie-1)))
          scanpart = scanpart(ie+1:)
        else if (iostat < 0 .and. ic+1 == index) then  ! last item
          column = trim(adjustl(scanpart))
          column_not_found = .False.
        end if
      end do
    end do
    if (column_not_found) then
      ! TODO error if not found, e.g. because end of file or line
    else
      ! Move to next line if not already
      if (iostat == 0) read(file_id, "(a)")
    end if
  end function read_csv_item