正则表达式使用单词边界，但单词以。结尾。 （期） [英] Regex using word boundary but word ends with a . (period)

问题描述

想要匹配单词 iv 不区分大小写

want to match word i.v. case insensitive

具有模式

(?i)\bi\.v\.

但要在末尾使用单词边界

上面的模式失败了它匹配

ivx

but want a word boundary on the end
the above pattern fails in that it matches
i.v.x

但是如果我尝试在最后添加工作边界

but if I try and add a work boundary to the end

(?i)\bi\.v\.\b

它失败了，因为它甚至不匹配iv
，因为我认为 \b 正在吃字面量。作为。是一个断字

需要 \。要贪婪

it fails in that it does not even match i.v. as I think the \b is eating the literal . as . is a word break
need the \. to be greedy

我想match

sam iv sam

i want to match
sam i.v. sam

不想匹配

sam.iv

ivsam

do not want to match
sam.i.v.
i.v.sam

距离更近

(?i)\bi\.v\.\s$

但找不到iv在行尾

推荐答案

\b 仅在字母数字字符和非字母数字字符（或字符串的开头/结尾）。因此，它与。之后不匹配，除非该点后紧跟字母数字字符。

\b only matches between an alphanumeric character and a non-alphanumeric character (or the start/end of string). Therefore, it doesn't match after a ., unless an alphanumeric character immediately follows that dot.

如果您的目的是确保在点后没有非空格字符，然后可以使用否定超前断言：

If your intent is to make sure that no non-whitespace character follows after the dot, then you can specify that using a negative lookahead assertion:

(?i)\bi\.v\.(?!\S)

（?! \S）的意思是断言下一个字符不是非空白字符。

(?!\S) means "Assert that the next character is not a non-whitespace character".

这听起来有些令人费解-为什么双重否定？为什么不（？= \s）表示断言下一个字符是空白字符？好吧，这里有一个细微的差别：第二个版本要求空格字符存在；这意味着正则表达式将无法在字符串末尾匹配。第一个正则表达式也处理这种情况。

This may sound a bit convoluted - why the double negative? Why not (?=\s) which means "Assert that the next character is a whitespace character"? Well, there is a subtle difference: The second version requires a whitespace character to be there; that means the regex would fail to match at the end of the string. The first regex handles that corner case as well.

如果您通常希望单词边界的概念表示空格分隔，那么您需要替换第一个 \b ：

If you generally want the concept of "word boundary" to mean "space-delimited", then you need to replace the first \b as well:

(?i)(?<!\S)i\.v\.(?!\S)

或正则表达式将匹配您似乎不想要的 sam.iv 。

or the regex will match sam.i.v. which you don't seem to want it to.

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