How to use regular expressions in golang to verify whether the URL address is an eighth-level domain name

In web development, verifying whether a URL address is an eighth-level domain name is a common task. In golang programming, regular expressions are a powerful tool for processing and validating text data. Therefore, this article will introduce how to use regular expressions in golang to verify whether the URL address is an eighth-level domain name.

What is an eighth-level domain name?

In the Internet domain name system, a domain name is composed of multiple parts. Looking from right to left, the last part of the domain name is the top-level domain name (such as .com, .net, .org, etc.), and the penultimate part is the second-level domain name (such as google.com, baidu.com, etc.), all the way to the left Going up are third-level, fourth-level, fifth-level...eight-level domain names, for example: www.example.com.cn.xx.yy.zzz.

Basics of regular expressions

Regular expressions are a powerful text processing tool that provide a flexible way to search, match and replace string data. In golang, the standard library provides the regexp package to support regular expression operations.

The following is the basic knowledge of some common regular expressions:

1. Character group: Use some characters in [] to match any one of them, such as [abc] to match Any character among a, b, c.
2. Quantifier: used to specify the number of times a character or a group of characters appears in a match, for example, * means 0 or more, means 1 or more,? It means 0 or 1, {n} means it appears exactly n times, {n,m} means it appears n-m times (including n and m).
3. Pattern modifier: used to modify the matching pattern, for example, i means ignoring case, g means global matching.

Use regular expressions to verify whether the URL address is an eighth-level domain name

The method to verify whether the URL address is an eighth-level domain name is to use regular expressions to match.

The following is a sample function that uses regular expressions to verify whether the specified URL address is an eighth-level domain name:

import "regexp"

func IsEightLevelDomain(url string) bool {
    // 定义正则表达式，匹配由8个英文字母数字、或-、或_组成的字符串，加上.com或.cn
    regular := `^[a-zA-Z0-9-_]{8}.(com|cn)$`
    // 创建正则表达式对象
    reg := regexp.MustCompile(regular)
    // 匹配字符串
    return reg.MatchString(url)
}

The regexp.MustCompile function is used in the code to compile the regular expression, Then use the MatchString method to match the specified URL address. If the match is successful, the function returns true, otherwise it returns false.

In the above code, we use the regular expression ^[a-zA-Z0-9-_]{8}.(com|cn)$, which means matching a A string consisting of 8 English alphanumeric characters, or -, or _, plus .com or .cn.

Conclusion

In golang, regular expressions can be used to easily verify whether the URL address is an eighth-level domain name. By learning the basics of regular expressions, you can quickly write powerful text processing programs. When you need to process text data when writing a golang program, you might as well try using regular expressions to help you complete the task.

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