来看这个内容的，估计和我一样被绕晕了， 找不到规则。其实这是shell比较灵活导致的。

其实遵循如下原则可以避免莫名其妙的意外（少掉头发）。

1） 坚决不使用反引号(`),  坚决使用$()

2)  对于不需要转义的字符串，坚决使用单引号括起来。 （反斜杆， 在双引号， 或不加引号的情况下， 会有特殊的变化）

/opt/syb/test # echo \opt\tmp\ | sed 's:\\:\\\\:g'
opttmp

echo "\opt\tmp\" | sed 's:\\:\\\\:g'
> ^C

惊不惊喜意不意外？？？！！！

推荐做法：

echo '\opt' | sed 's:\\:\\\\:g'

也可以用双引号：

echo '\opt' | sed "s:\\\\:\\\\\\\\:g"

转义列表：

https://www.cnblogs.com/fnlingnzb-learner/p/6839669.html

https://www.cnblogs.com/f-ck-need-u/p/7499309.html

于是，关于sed如何和shell交互的问题可以得出一套结论：

1. 遇到需要被shell解析的都不加引号，或者加双引号；
2. 遇到shell和所执行命令共有的特殊字符时，要想被sed解析，必须加单引号，或者在双引号在加反斜线转义；
3. 那些无关紧要的字符，无论加什么引号。

不管是用单引号，还是双引号。

针对\匹配替换：  需要转义 \\

针对/匹配替换， 使用：作为分隔符， 不用转义

https://unix.stackexchange.com/questions/379572/escaping-both-forward-slash-and-back-slash-with-sed

You need to escape (with backslash \ ) all substituted slashes / and all backslashes \ separately, so:

$ echo "/tmp/test/folder1/test.txt" | sed 's/\//\\\//g'
\/tmp\/test\/folder1\/test.txt

but that's rather unreadable.

However, sed allows to use almost any character as a separator instead of / , this is especially useful when one wants to substitute slash / itself, as in your case, so using for example semicolon ; as separator the command would become simpler:

echo "/tmp/test/folder1/test.txt" | sed 's;/;\\/;g'

Other cases:

• If one wants to stick with slash as a separator and use double quotes then all escaped backslashes have to be escaped one more time to preserve their literal values:

  echo "/tmp/test/folder1/test.txt" | sed "s/\//\\\\\//g"

• if one doesn't want quotes at all then yet another backslash is needed:

  echo "/tmp/test/folder1/test.txt" | sed s/\\//\\\\\\//g

$ sed 's:/:\\/:g'  <<<"$str"
\/tmp\/test\/folder1\/test.txt

https://unix.stackexchange.com/questions/398646/why-is-a-single-backslash-shown-when-using-quotes .

the backslash retains its special meaning only when followed by one of the following characters: ‘ $ ’, ‘ ` ’, ‘ " ’, ‘ \ ’, or newline . Within double quotes, backslashes that are followed by one of these characters are removed.

Backslash is interpreted differently according context:

• Within double quotes (your first example):

  The backslash  retains its special meaning  only when followed
  by one of the following characters: $, `, ", \, or <newline>.

• Without quotes (your second example):

  A  non-quoted  backslash  (\)  is the  escape  character.   It
  preserves  the  literal  value  of  the  next  character  that
  follows,  with the  exception of  <newline>.  If  a \<newline>
  pair  appears, and  the backslash  is not  itself quoted,  the
  \<newline> is treated  as a line continuation (that  is, it is
  removed from the input stream and effectively ignored).

• Using the construct $'....' , where you can use inside the quote the standard backspace character, nearly as in C. e.g. \n , \t , etc.

• Using backquotes:

• When  the old-style  backquote form  of substitution  is used,
  backslash retains its literal  meaning except when followed by
  $, `, or \.

前言：来看这个内容的，估计和我一样被绕晕了， 找不到规则。其实这是shell比较灵活导致的。其实遵循如下原则可以避免莫名其妙的意外（少掉头发）。1） 坚决不使用反引号(`), 坚决使用$()2) 对于不需要转义的字符串，坚决使用单引号括起来。 （反斜杆， 在双引号， 或不加引号的情况下， 会有特殊的变化）例如：/opt/syb/test # echo \opt\tmp\ | sed 's:\\:\\\\:g'opttmpecho "\opt\tmp\" | se... 当我想替换文件中的路径时，使用 转义 符号（\）会比较麻烦且可读性很差。 比如要将abc.sh中的/a/b/c替换成/d/e/f，命令如下： sed -i 's/\/a\/b\/c/\/d\/e\/f/g' 分隔符由/换成#（其他字符也可以，只要跟在s命令后面即可）： sed -i 's#/a/b/c#/d/e/f#g' - ` sed ` 是 Linux 中处理文本的工具之一。 - `s` 表示替换操作。 - `/"//g` 表示将 双引号 替换为空，`g` 表示全局替换，即一行中所有匹配的 双引号 都会被替换为空。 使用这个命令可以将文件中所有的 双引号 都去掉。如果你只想去掉特定的 双引号 ，可以根据需要修改命令中的正则表达式。