--quiet don't print OK for each successfully verified file 被查证的文件如果成功，不打印OK（即仅仅显示错误信息，屏蔽验证正确的文件）
--status don't output anything, status code shows success 不输入任何东西，状态码显示success （即无论正确与否，都不输出任何信息，echo $?看最后结果）
-w, --warn warn about improperly formatted checksum lines 关于非合法的格式的checksum行，抛出warning，如此之外，不予显示
--help display this help and exit
--version output version information and exit
The sums are computed as described in RFC 1321. When checking, the input
should be a former output of this program. 当检查时，输入的应该是之前程序的输出。
The default mode is to print a line with checksum, a character indicating type a character indi-cating type (‘*’ for binary, ‘ ’ for text), and name for each FILE.
默认的mode和checksum合并为一行打印，一个字符指出mode的类型（* 为二进制，空为text），每个FILE为name
Report md5sum bugs to bug-coreutils@gnu.org
GNU coreutils home page: <>
General help using GNU software: <>
For complete documentation, run: info coreutils 'md5sum invocation'
PS:
$ openssl dgst -md5 test.enc
MD5(test.enc)= 9a8ca202880547463da5796c6d29f611
$ md5sum test.enc
9a8ca202880547463da5796c6d29f611 test.enc