close_log_file Subroutine

    subroutine close_log_file(io_err)
        integer, intent(inout), optional :: io_err
        !! Closes the log file
        if (file_opened) then
            if (present(io_err)) then
                close(log_unit, iostat=io_err)
            else
                close(log_unit)
            end if
            log_unit = -1
        end if
    end subroutine close_log_file