Linux命令之md5sum

 

md5sum

md5sum用来计算一段内容的md5校验和，这段内容可以是从文件中读取的，也可以是从标准流输入的。甚至还可以将结果保存到文件，在以后使用这个文件来校验文件是否被改变。

需要注意的是md5sum只计算文件的内容，不关注文件的元信息。

 

简单使用

创建一个文件：

echo hello, world >> a.txt

计算它的md5检验和：

 

校验文件是否改变

可以把计算的结果存储到文件中，之后使用这个文件来校验文件是否发生了变化：

md5sum a.txt >> a.txt.md5sum

看下这个文件的内容：

使用这个文件来检查是否改变：

 

修改a.txt，追加一些内容：

再次检验：

 

从流读入

当不使用选项或者跟着-的时候，会从标准输入流stdin读取数据，可以使用流传递：

也可以手动输入，手动输入的时候使用Ctrl+D结束输入：

 

 

md5sum手册：

MD5SUM(1)                                                                              User Commands                                                                             MD5SUM(1)

NAME
       md5sum - compute and check MD5 message digest

SYNOPSIS
       md5sum [OPTION]... [FILE]...

DESCRIPTION
       Print or check MD5 (128-bit) checksums.  With no FILE, or when FILE is -, read standard input.

       -b, --binary
              read in binary mode

       -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)

              Note: There is no difference between binary and text mode option on GNU system.

   The following four 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

       --strict
              exit non-zero for improperly formatted checksum lines

       -w, --warn
              warn about improperly formatted checksum lines

       --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 charac‐
       ter indicating input mode ('*' for binary, space for text), and name for each FILE.

       GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report md5sum translation bugs to <http://translationproject.org/team/>

BUGS
       The MD5 algorithm should not be used any more for security related purposes.  Instead, better use an SHA-2 algorithm,  implemented  in  the  programs  sha224sum(1),  sha256sum(1),
       sha384sum(1), sha512sum(1)

 

 

 

1. http://www.cnblogs.com/f-ck-need-u/p/7430264.html

 

 

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