【linux】md5sum 命令详解

1、命令详解

$ md5sum --help
Usage: md5sum [OPTION]... [FILE]...
Print or check MD5 (128-bit) checksums.
With no FILE, or when FILE is -, read standard input.

  -b, --binary         read in binary mode
  -c, --check          read MD5 sums from the FILEs and check them
      --tag            create a BSD-style checksum
  -t, --text           read in text mode (default)

The following three options are useful only when verifying checksums:
      --quiet          don't print OK for each successfully verified file
      --status         don't output anything, status code shows success
  -w, --warn           warn about improperly formatted checksum lines

      --strict         with --check, exit non-zero for any invalid input
      --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.  The default mode is to print
a line with checksum, a character indicating input mode ('*' for binary,
space for text), and name for each FILE.

Report md5sum bugs to [email protected]
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
For complete documentation, run: info coreutils 'md5sum invocation'

-b, --binary：以二进制方式读取文件
-t, --text ：默认配置，以文本方式读取文件
这两种方式的输出结果相同，测试例子如下：

$ md5sum hello.c 
6a29375b3e989a04355ecee250448c6e  hello.c
$ md5sum -b hello.c 
6a29375b3e989a04355ecee250448c6e *hello.c
$ md5sum a.out 
40a9477fa25a9df86361571dd60feffc  a.out
$ md5sum -b a.out 
40a9477fa25a9df86361571dd60feffc *a.out

-c, --check：从指定文本中读取md5值，然后检测MD5值对应的文件是否完整，这个“指定文本”的格式如下：

40a9477fa25a9df86361571dd60feffc  a.out

就是在计算文件MD5值时的输出结果，使用例子如下：

$ md5sum a.out > md5.txt
$ cat md5.txt 
40a9477fa25a9df86361571dd60feffc  a.out
$ md5sum -c md5.txt 
a.out: OK

当检查出错误时的打印信息如下

$ md5sum -c md5.txt 
a.out: FAILED
md5sum: WARNING: 1 computed checksum did NOT match

–tag：安装BSD样式输出结果

$ md5sum --tag a.out 
MD5 (a.out) = 40a9477fa25a9df86361571dd60feffc

下面三个选项，只有在检查MD5值（-c）时有效，即和-c一起使用，否则会报错：

$ md5sum --quiet  md5.txt 
md5sum: the --quiet option is meaningful only when verifying checksums
Try 'md5sum --help' for more information.

–quiet：如果检查MD5值成功，不再打印OK


$ md5sum -c md5.txt 
a.out: OK
//成功时没有输出：
$ md5sum --quiet -c md5.txt 
//失败才打印，错误信息
$ md5sum -c md5.txt 
a.out: FAILED
md5sum: WARNING: 1 computed checksum did NOT match
$ md5sum --quiet -c md5.txt 
a.out: FAILED
md5sum: WARNING: 1 computed checksum did NOT match

–status：不打印任何信息，执行结果以状态码形式输出

//失败情况
$ md5sum --status -c md5.txt 
$ echo $?
1
//成功情况
$ md5sum --status -c md5.txt 
$ echo $?
0

-w, --warn ：如果检测文本中有，非法的行，不符合md5sum -c需要的格式，则打印出警告信息

$ md5sum --warn -c md5.txt 
a.out: OK
md5sum: md5.txt: 2: improperly formatted MD5 checksum line
md5sum: WARNING: 1 line is improperly formatted

–strict：对于无效的输入，都返回非零状态（不知道怎么用）
–help：帮助信息
–version：版本信息

【linux】md5sum 命令详解

1、命令详解

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