Question

在C＃和Javascript中验证FQDN的正确正则表达式是什么？我一直在寻找，我发现不同的规格。哪一个是正确的。

我发现的几个例子：

   1.(?=^.{1,254}$)(^(?:(?!\d+\.|-)[a-zA-Z0-9_\-]{1,63}(?<!-)\.?)+(?:[a-zA-Z]{2,})$)

    2. (?=^.{1,254}$)(^(?:(?!\d|-)[a-zA-Z0-9\-]{1,63}(?<!-)\.?)+(?:[a-zA-Z]{2,})$)

    3. \b((?=[a-z0-9-]{1,63}\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}\b 

   (Regular Expression cook book)

请帮忙

Answer 1

一般来说，正则表达式食谱是一个很好的信息来源，由两位正则表达式专家编写，所以你应该从那里开始。在那里概述的解决方案还不太适合您的需求（它不验证整个字符串但匹配子字符串，并且它不检查字符串的总长度），所以我们可以稍微修改它：

/^(?=.{1,254}$)((?=[a-z0-9-]{1,63}\.)(xn--+)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}$/i

<强>说明：

^                      # Start of string
(?=.{1,254}$)          # Assert length of string: 1-254 characters
(                      # Match the following group (domain name segment):
 (?=[a-z0-9-]{1,63}\.) # Assert length of group: 1-63 characters
 (xn--+)?              # Allow punycode notation (at least two dashes)
 [a-z0-9]+             # Match letters/digits
 (-[a-z0-9]+)*         # optionally followed by dash-separated letters/digits
 \.                    # followed by a dot.
)+                     # Repeat this as needed (at least one match is required)
[a-z]{2,63}            # Match the TLD (at least 2 characters)
$                      # End of string

正则表达式在C＃和Javascript中验证FQDN

1 个答案: