Sed 正则表达式和子字符串否定 [英] Sed regex and substring negation

问题描述

查找与特定模式不匹配的子字符串(前后为特定字符串的字符串)的正确语法是什么?

What is the correct syntax for finding a substring (a string which is preceded and followed by specific strings) which does not match a specific pattern?

例如，我想取以BEGIN_开始、以_END结束和结束的所有子字符串中间的子串不等于FOO；并将整个子字符串替换为(inner substring)"格式.以下将匹配:

For example, I want to take all substrings which start with BEGIN_, end with _END and the substring in between is not equal to FOO; and replace the whole substring with the format "(inner substring)". The following would match:

• BEGIN_bar_END -> (bar)
• BEGIN_buz_END -> (buz)
• BEGIN_ihfd8f398IHFf9f39_END -> (ihfd8f398IHFf9f39)

• BEGIN_bar_END -> (bar)
• BEGIN_buz_END -> (buz)
• BEGIN_ihfd8f398IHFf9f39_END -> (ihfd8f398IHFf9f39)

但是 BEGIN_FOO_END 不匹配.

我尝试了以下内容，但似乎找不到正确的语法:

I have played around with the following, but cannot seem to find the correct syntax:

sed -e 's/BEGIN_(^FOO)_END/($1)/g'
sed -e 's/BEGIN_([^FOO])_END/($1)/g'
sed -e 's/BEGIN_(?!FOO)_END/($1)/g'
sed -e 's/BEGIN_(!FOO)_END/($1)/g'
sed -e 's/BEGIN_(FOO)!_END/($1)/g'
sed -e 's/BEGIN_!(FOO)_END/($1)/g'

推荐答案

sed 中没有通用的否定运算符，IIRC 因为将带有否定的正则表达式编译为 DFA 需要指数级的时间.你可以解决这个问题

There is no general negation operator in sed, IIRC because compilation of regexes with negation to DFAs takes exponential time. You can work around this with

'/BEGIN_FOO_END/b; s/BEGIN_\(.*\)_END/(\1)/g'

其中 /BEGIN_FOO_END/b 表示:如果我们找到 BEGIN_FOO_END，则 branch(跳转)到 sed 的末尾 脚本.

where /BEGIN_FOO_END/b means: if we find BEGIN_FOO_END, then branch (jump) to the end of the sed script.

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