有什么区别？：，？！和？=在正则表达式？ [英] what is the difference between ?:, ?! and ?= in regex?

问题描述

我搜索了这些表达式的含义，但无法理解它们之间的确切差异。
这就是他们所说的：

I searched for the meaning of these expressions but couldn't understand the exact differnce between them. This is what they say:

• ？：匹配表达但是不要捕获它。


• ？= 匹配后缀但将其从捕获中排除。


• ？！如果没有后缀，则匹配。

• ?: Match expression but do not capture it.
• ?= Match a suffix but exclude it from capture.
• ?! Match if suffix is absent.

我尝试过使用这些简单的RegEx并获得了类似的结果。
示例：以下3个表达式给出非常相似的结果。

I tried using these in simple RegEx and got similar results for all. example: the following 3 expressions give very similar results.

• [a-zA-Z0- 9 ._-] + @ [a-zA-Z0-9 - ] +（？！\。[a-zA-Z0-9] +）*


• [a-zA-Z0-9 ._-] + @ [a-zA-Z0-9 - ] +（？= \。[a-zA-Z0-9] +）*


• [a-zA-Z0-9 ._-] + @ [a-zA-Z0-9- ] +（？：\。[a-zA-Z0-9] +）*

• [a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?!\.[a-zA-Z0-9]+)*
• [a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?=\.[a-zA-Z0-9]+)*
• [a-zA-Z0-9._-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9]+)*

推荐答案

？= 和之间的区别？！是前者需要的给定表达式匹配，后者要求不匹配。例如 a（？= b）将匹配ab中的a，但不匹配ac中的a。而 a（？！b）将匹配ac中的a，而不匹配ab中的a。

The difference between ?= and ?! is that the former requires the given expression to match and the latter requires it to not match. For example a(?=b) will match the "a" in "ab", but not the "a" in "ac". Whereas a(?!b) will match the "a" in "ac", but not the "a" in "ab".

？：和？= 之间的区别是？ = 排除整个比赛中的表达式，而？：只是不创建捕获组。所以例如 a（？：b）将匹配abc中的ab，而 a（？= b）只会匹配abc中的a。 a（b）将匹配abc中的ab和创建包含b的捕获。

The difference between ?: and ?= is that ?= excludes the expression from the entire match while ?: just doesn't create a capturing group. So for example a(?:b) will match the "ab" in "abc", while a(?=b) will only match the "a" in "abc". a(b) would match the "ab" in "abc" and create a capture containing the "b".

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