grep'\ $'和grep"\ $"之间有什么区别? [英] What's the differences between grep '\$' and grep "\$"?

问题描述

grep'\ $'和grep"\ $"有什么区别?

有人可以对下面的命令给出正确的解释.

 <代码>/usr/download/test/myshell $ cat a_file开机书豪饮机器靴子邦吉吠土豚碎的凝灰岩机器人 

输出:grep'\ $'a_file

 <代码>/usr/download/test/myshell $ grep'\ $'a_file碎的凝灰岩 

输出:grep"\ $" a_file

 /usr/download/test/myshell $ grep"\ $" a_file开机书豪饮机器靴子邦吉吠土豚碎的凝灰岩机器人 

输出:grep \ $ a_file

 <代码>/usr/download/test/myshell $ grep \ $ a_file开机书豪饮机器靴子邦吉吠土豚碎的凝灰岩机器人 

解决方案

\ 是 bash 和 grep 的转义字符./p>

• 在 grep \ $ a_file 中， bash 认为您正在转义 $ ，但是不需要转义，因此正在执行的regexp是 $ ，它会查找任何有结尾的行(毫无疑问，所有行都有).

• 在 grep"\ $" a_file 中， bash 解释双引号，从而允许在其中使用各种卑鄙的内容.特别是，它仍然允许 bash 转义，就像上面一样；再次执行的命令是 $ .

• 在 grep'\ $'a_file 中， bash 解释单引号，这基本上告诉 bash 将内容完整保留为尽可能地.值得注意的是， bash 不会删除反斜杠.正则表达式将为 \ $ ，其中 \ 从美元中删除行尾"的特殊含义，并且正在搜索文字美元字符.

有关更多详细信息，请参见 QUOTING 下的 man bash .

What's the differences between grep '\$' and grep "\$"?

Could someone give a proper explanation for the below command.

/usr/download/test/myshell$ cat a_file
boot
book
booze
machine
boots
bungie
bark
aardvark
broken$tuff
robots

Output: grep '\$' a_file

/usr/download/test/myshell$ grep '\$' a_file 
broken$tuff

Output: grep "\$" a_file

/usr/download/test/myshell$ grep "\$" a_file 
boot
book
booze
machine
boots
bungie
bark
aardvark
broken$tuff
robots

Output: grep \$ a_file

/usr/download/test/myshell$ grep \$ a_file 
boot
book
booze
machine
boots
bungie
bark
aardvark
broken$tuff
robots

解决方案

\ is an escape character for both bash and grep.

• In grep \$ a_file, bash thinks you are escaping $, but it doesn't need escaping, so the regexp being executed is $, which looks for any line that has an end (unsurprisingly, all of them do).

• In grep "\$" a_file, bash interprets double quotes, which allow a variety of bashy things to go on inside. Specifically, it still allows bash escapes, just like above; the command being executed is again $.

• In grep '\$' a_file, bash interprets single quotes, which basically tell bash to keep things inside intact as much as possible. Notably, bash will not remove the backslash. The regexp will be \$, where \ removes the special meaning of "end of line" from the dollar, and a literal dollar character is being searched for.

See man bash under QUOTING for more details.

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