问题描述
我有以下RegEx ^ http:\/\/(?! www \.)(.*)$
I have the following RegEx ^http:\/\/(?!www\.)(.*)$
预期行为:
http://example.com - Match
http://www.example.com - Does not match
golang 似乎不支持否定超前.如何重写此RegEx以在 golang 上工作?
It looks like golang does not support negative lookahead. How can I rewrite this RegEx to work on golang?
更新
我不是使用golang进行编码，而是使用 Traefik 接受正则表达式(golang风格)作为配置值，所以基本上我有这个:
I'm not coding using golang, I'm using Traefik that accepts a Regex (golang flavor) as a config value, so basically I have this:
regex = "^https://(.*)$"
replacement = "https://www.$1"
我想要的是始终在URL中添加 www.，但是如果该URL已经包含 NOT ，则为 NOT ，否则它将成为 www.www.*
What I want is to always add www. to the URL, but NOT if the URL has it already, otherwise it would become www.www.*
推荐答案
如果您真的想手动创建否定的超前查询，则需要在正则表达式中排除所有可能的 w :
If you're really bent on creating a negative lookahead manually, you will need to exclude all possible w in the regexp:
^https?://(([^w].+|w(|[^w].*)|ww(|[^w].+)|www.+)\.)?example\.com$
此正则表达式允许在 example.com 之前带有点的任何单词，除非该单词只是 www .通过允许任何不以 w 开头的单词来做到这一点，或者，如果它以 w 开头，则只能是 w 或紧随其后由非 w 和其他东西组成.如果它以两个 w 开头，那么它必须是正好等于或后面跟一个非 w .如果它以 www 开头，则必须 后跟某些内容.
This regexp allows any word with a dot before example.com, unless that word is just www. It does so by allowing any word that does not start with w, or, if it starts with w it is either just that w or followed by a non-w and other stuff. If it starts with two w, then it must be either just that or followed by a non-w. If it starts with www, it must be followed by something.
澄清使这变得容易得多.方法是始终(可选)匹配 www.，然后始终将其放回替换中:
The clarification makes this much much easier. The approach is to always (optionally) match www. and then to put that back in the replacement always:
搜索:
^http://(?:www\.)?(.*)\b$
替换:
http://www.$1
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