Ruby 中有效子域的正则表达式 [英] Regular expression for valid subdomain in Ruby

问题描述

我正在尝试验证将用作子域的用户输入字符串.规则如下:

I'm attempting to validate a string of user input that will be used as a subdomain. The rules are as follows:

1. 长度介于 1 到 63 个字符之间(我从 Google Chrome 在子域中允许的字符数中取了 63，不确定它是否实际上是服务器指令.如果您对有效最大长度有更好的建议，我是有兴趣听)
2. 可能包含 a-zA-Z0-9、连字符、下划线
3. 不得以连字符或下划线开头或结尾

从下面的输入中，我添加了以下内容:4. 不应包含连续的连字符或下划线.

From input below, I've added the following: 4. Should not contain consecutive hyphens or underscores.

示例:

a => valid
0 => valid
- => not valid
_ => not valid
a- => not valid
-a => not valid
a_ => not valid
_a => not valid
aa => valid
aaa => valid
a-a-a => valid
0-a => valid
a&a => not valid
a-_0 => not valid
a--a => not valid
aaa- => not valid

我的问题是我不确定如何使用 RegEx 指定字符串只能是一个字符，同时还指定它不能以连字符或下划线开头或结尾.

My issue is I'm not sure how to specify with a RegEx that the string is allowed to be only one character, while also specifying that it may not begin or end with a hyphen or underscore.

谢谢！

推荐答案

您不能可以在正确子域中使用下划线，但是您需要它们吗?在 trimming 你的输入之后，做一个简单的字符串长度检查，然后用这个测试:

You can't can have underscores in proper subdomains, but do you need them? After trimming your input, do a simple string length check, then test with this:

/^[a-z\d]+(-[a-z\d]+)*$/i

使用上述方法，您将不会获得连续的 - 字符，例如a-bbb-ccc 通过，a--d 失败.

With the above, you won't get consecutive - characters, e.g. a-bbb-ccc passes and a--d fails.

/^[a-z\d]+([-_][a-z\d]+)*$/i

也允许不连续的下划线.

Will allow non-consecutive underscores as well.

更新:您会发现，在实践中，不允许使用下划线，并且所有子域都必须以字母开头.上面的解决方案不允许国际化子域(punycode).你最好用这个

Update: you'll find that, in practice, underscores are disallowed and all subdomains must start with a letter. The solution above does not allow internationalised subdomains (punycode). You're better of using this

/\A([a-z][a-z\d]*(-[a-z\d]+)*|xn--[\-a-z\d]+)\z/i

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