“回波”和“回波”之间的区别是什么？和“echo -n”？ [英] What is the difference between "echo" and "echo -n"?

问题描述

echo -n 终端上的手册页如下：

 不打印结尾的换行符。这也可以通过将`\c'附加到字符串的末尾来实现
，如通过
 iBCS2兼容系统所做的那样。注意，此选项以及`\c'的
效果是在由Cor。修订的IEEE Std 1003.1-2001 
（`POSIX.1'）中实现定义的。 1-2002。强烈鼓励旨在
最大可移植性的应用程序使用printf（1）至
抑制换行符。 
 
一些shell可能提供一个内建的echo命令，这个命令与这个实用程序类似或者相同。最值得注意的是，sh（1）中的内置回声不会
接受-n选项。请参阅builtin（1）手册页。 
  

当我尝试通过以下方式生成MD5哈希：

  echopassword| md5 
  

它返回 286755fad04869ca523320acce0dc6a4

当我做

  echo -npassword
  / pre> 
 
 
它返回在线MD5生成器返回的值： 5f4dcc3b5aa765d61d8327deb882cf99  
 
 
 
选项 -n 有什么区别？ 
解决方案
当您执行 echopassword| md5 ， echo 向要进行哈希处理的字符串添加换行符，即 password\\\
 。当添加 -n 开关时，它不会，所以只有字符 password 被哈希。
 
 
 
更好地使用 printf ，它不需要任何开关就可以实现：
  printf'password'| md5 
  
对于'password' isn 
  printf'％s'$ pass| md5 
  
这意味着密码中的转义字符（例如 \\\
 ， \t ）不会解释为 printf  p> 
The manual page on Terminal for echo -n is the following:
 -n    Do not print the trailing newline character.  This may also be
       achieved by appending `\c' to the end of the string, as is done by
       iBCS2 compatible systems.  Note that this option as well as the
       effect of `\c' are implementation-defined in IEEE Std 1003.1-2001
       (``POSIX.1'') as amended by Cor. 1-2002.  Applications aiming for
       maximum portability are strongly encouraged to use printf(1) to
       suppress the newline character.

 Some shells may provide a builtin echo command which is similar or iden-
 tical to this utility.  Most notably, the builtin echo in sh(1) does not
 accept the -n option.  Consult the builtin(1) manual page.
When I try to do generate an MD5 hash by:
echo "password" | md5
It returns 286755fad04869ca523320acce0dc6a4

When I do
echo -n "password"
It returns the value that online MD5 generators return: 5f4dcc3b5aa765d61d8327deb882cf99

What difference does the option -n do? I don't understand the entry in Terminal.
解决方案
When you do echo "password" | md5, echo adds a newline to the string to be hashed, i.e. password\n. When you add the -n switch, it doesn't, so only the characters password are hashed.

Better to use printf, which does what you tell it to without needing any switches:
printf 'password' | md5
For cases where 'password' isn't just a literal string, you should use a format specifier instead:
printf '%s' "$pass" | md5
This means that escape characters within the password (e.g. \n, \t) aren't interpreted by printf and are printed literally.

                        
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