md5&sha 生成和校验
以sha512sum 为例
sha512sum filename
$ sha512sum ls
ef73136452875c4cae5c6b43117c601ec679f027a4ff1c285d477ab6a8950edb9f8da0822a57b1c0eb719d563cb2033765cdf6c949e9df073fbf7772bf5fad71 ls
$ sha512sum ls > ls.sha512
$ sha512sum -c ls.sha512
ls: OK