init_double_occ_output Subroutine

    subroutine init_double_occ_output(funit)
        ! i need a routine to initialize the additional output, which I
        ! think should go into a seperate file for now!
        integer, intent(in) :: funit
        character(*), parameter :: this_routine = "init_double_occ_output"
        character(30) :: filename
        character(43) :: filename2
        character(12) :: num
        logical :: exists
        integer :: i, ierr

        filename = "double_occupancy_stats"

        if (tReadPops) then
            open(funit, file=filename, status='unknown', position='append')

        else

            inquire (file=filename, exist=exists)

            ! rename the existing file an create a new one
            if (exists) then

                i = 1
                do while (exists)
                    write(num, '(i12)') i
                    filename2 = trim(adjustl(filename))//"."// &
                                trim(adjustl(num))

                    inquire (file=filename2, exist=exists)
                    if (i > 10000) call stop_all(this_routine, &
                                                 "error finding free double_occupancy_stats")

                    i = i + 1
                end do

                ! i am not sure where this routine is defined:
                call rename(filename, filename2)
            end if

            open(funit, file=filename, status='unknown', iostat=ierr)

        end if

    end subroutine init_double_occ_output