正则表达式用于从FQDN中提取二级域名? [英] Regex for extracting second level domain from FQDN?

问题描述

我不知道这一点.我需要从FQDN中提取第二级域.例如，所有这些都需要返回"example.com":

I can't figure this out. I need to extract the second level domain from a FQDN. For example, all of these need to return "example.com":

1. example.com
2. foo.example.com
3. bar.foo.example.com
4. example.com:8080
5. foo.example.com:8080
6. bar.foo.example.com:8080

这是我到目前为止所拥有的:

Here's what I have so far:

    Dim host = Request.Headers("Host")
    Dim pattern As String = "(?<hostname>(\w+)).(?<domainname>(\w+.\w+))"
    Dim theMatch = Regex.Match(host, pattern)
    ViewData("Message") = "Domain is: " + theMatch.Groups("domainname").ToString

对于example.com:8080和bar.foo.example.com:8080，它将失败.有什么想法吗?

It fails for example.com:8080 and bar.foo.example.com:8080. Any ideas?

推荐答案

我成功使用了此Regex来匹配您的测试用例列表中的"example.com".

I used this Regex successfully to match "example.com" from your list of test cases.

"(?<hostname>(\w+\.)*)(?<domainname>(\w+\.\w+))"

点字符(.")需要转义为"\.".这 "."正则表达式模式中的字符与任何字符匹配.

The dot character (".") needs to escaped as "\.". The "." character in a regex pattern matches any character.

此外，您提供的regex模式要求在域名匹配(模式的这一部分(?(\ w +))")之前必须有1个或多个单词字符，后跟一个点.此外，我假设字符应该被转义).域名匹配之前没有单词和点，因此无法匹配输入的"example.com".

Also the regex pattern you provided requires that there be 1 or more word characters followed by a dot before the domainname match (this part "(?(\w+))." of the pattern. Also, I'm assuming that the . character was supposed to be escaped). This fails to make a match for the input "example.com" because there's no word character and dot before the domainname match.

我更改了模式，以便主机名匹配具有零个或多个"1个或多个单词字符后跟一个点"的匹配项.这将匹配"foo.example.com"中的"foo"和"foo.bar.example.com"中的"foo.bar".

I changed the pattern so that the hostname match would have zero or more matches of "1 or more word characters followed by a dot". This will match "foo" in "foo.example.com" and "foo.bar" in "foo.bar.example.com".

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