timer_write Subroutine

   impure subroutine timer_write(this, file_name)
      class(timer), intent(in) :: this
      character(*), intent(in) :: file_name
      logical                  :: file_exists
      integer                  :: nunit

      ! Check if the file exists
      inquire(file=file_name, exist=file_exists)

      ! Open the file in appropriate mode
      if (file_exists) then
         open(newunit=nunit, file=file_name, status='old', action='write', position='append')
      else
         open(newunit=nunit, file=file_name, status='new', action='write')
      end if

      ! Write the elapsed time to the file
      write(nunit, '(g0)') this%elapsed_time

      ! Close the file
      close(nunit)

   end subroutine timer_write