def get_pager_start(pager, start):
    """Return the string for paging files with an offset.

    This is the '+N' argument which less and more (under Unix) accept.
    """
    if pager in ['less', 'more']:
        if start:
            start_string = '+' + str(start)
        else:
            start_string = ''
    else:
        start_string = ''
    return start_string
