regular-expressions 【IP Addresses】

最新推荐文章于 2024-04-25 14:06:21 发布

n5ken

最新推荐文章于 2024-04-25 14:06:21 发布

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文章标签： regex numbers access each

本文链接：https://blog.youkuaiyun.com/n5ken/article/details/4382304

本文介绍两种正则表达式用于匹配有效的IPv4地址。一种简单快速但不够精确，可能将无效的IP地址视为有效；另一种虽然复杂，却能准确地验证每个部分是否在0到255的有效范围内。

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IP Addresses

Matching an IP address is another good example of a trade-off between regex complexity and exactness. /b/d{1,3}/./d{1,3}/./d{1,3}/./d{1,3}/b will match any IP address just fine, but will also match 999.999.999.999 as if it were a valid IP address. Whether this is a problem depends on the files or data you intend to apply the regex to. To restrict all 4 numbers in the IP address to 0..255, you can use this complex beast: /b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/b (everything on a single line). The long regex stores each of the 4 numbers of the IP address into a capturing group. You can use these groups to further process the IP number.

If you don't need access to the individual numbers, you can shorten the regex with a quantifier to: /b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/b . Similarly, you can shorten the quick regex to /b(?:/d{1,3}/.){3}/d{1,3}/b

参考：http://www.regular-expressions.info/examples.html