scan_fmt scan_fmt为Rust提供了一个类似于scanf()的简单输入。 目的是使从字符串或stdin读取数据更容易。 当前,格式字符串支持以下特殊序列: {{ = escape for '{' }} = escape for '}' {} = return any value (until next whitespace) {d} = return base-10 decimal {x} = return hex (0xab or ab) {f} = return float {*d} = "*" as the first character means "match but don't return" {2d} or {2x} or {2f} = limit the maximum width to 2. Any po