为什么反斜杠防止别名扩展？

问题描述

在我的问题的第一部分，我将提供一些背景信息作为一个
服务给社区。第二部分包含实际问题。

第一部分

假设我' ve创建了以下别名：

  alias ls ='ls -r'
  / pre> 
 
 
我知道如何使用以下
方式临时unalias（即覆盖此别名）：
 
 
 
 1）命令的完整路径名： / bin / ls  
 
 
 
 2）命令替换： $（which ls） 
 
 
 
 3）命令内置：命令ls  
 
 
 
 4）双引号：ls 
 
 
 
 5）单引号：'ls' 
 
 
 
 6）反斜杠字符： \ls  
 
 
 
案例1是明显的，情况2只是一个变体。案例3中的内置命令被设计为忽略shell函数，但显然它也可以用于规避别名。最后，案例4和5与：
和：
 第二部分 
 
 
 
以下是问题：为什么案例6（通过说 \ls 覆盖别名）
考虑引用该词？根据这个问题的样式，我正在寻找对官方文档的引用。
 
 
 
文档说，反斜杠只能转义以下
字符，而不是单引号和双引号，引用一个
字符序列。 ：
 ：
（BTW，不是下一个字符跟随一点点过度？）
 
 
 
可能的答案可能是这种情况不是那么特别：它是
类似于ANSI-C引用中的一些情况，例如 \\\
nn 。但是，这仍然是
转义单个字符（八位字符的值为八进制
值nnn），而不是字符序列。
解决方案
只是为了完成，这是另一种方法来抑制别名&函数查找（通过清除单个命令的整个shell环境）：
 ＃cf. http://bashcurescancer.com/temporarily-clearing-environment-variables.html 
 env -i ls 
  
 
In the first part of my question I will provide some background info as aservice to the community. The second part contains the actual question.
Part I
Assume I've created the following alias:
alias ls='ls -r'
I know how to temporarily unalias (i.e., override this alias) in the followingways, using:
1) the full pathname of the command: /bin/ls
2) command substitution: $(which ls)
3) the command builtin: command ls
4) double quotation marks: "ls"
5) single quotation marks: 'ls'
6) a backslash character: \ls
Case 1 is obvious and case 2 is simply a variation. The command builtin in case 3 was designed to ignore shell functions, but apparently it also works for circumventing aliases. Finally, cases 4 and 5 are consistent with both the POSIX standard (2.3.1): 
and the Bash Reference Manual (6.6):
Part II
Here's the question: why is case 6 (overriding the alias by saying \ls)considered quoting the word? In keeping with the style of this question, I am looking for references to the "official" documentation.
The documentation says that a backslash only escapes the followingcharacter, as opposed to single and double quotation marks, which quote asequence of characters.  POSIX standard (2.2.1): 
Bash Reference Manual (3.1.2.1): 
(BTW, isn't "the next character that follows" a bit of overkill?)
A possible answer might be that this situation isn't that special: it issimilar to a few cases in ANSI-C quoting, e.g. \nnn. However, that is stillescaping a single character (the eight-bit character whose value is the octalvalue nnn), not a sequence of characters.
 解决方案 
Just for completion, here's yet another way to suppress alias & function lookups (by clearing the entire shell environment for a single command):
# cf. http://bashcurescancer.com/temporarily-clearing-environment-variables.html
env -i ls
                        
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