How to use regular expressions to verify URL domain names in golang

Using regular expressions to verify URL domain names in golang is a very common task. This is usually because we need to ensure that the domain name extracted from the URL is valid and legal. This article explains how to use regular expressions to verify URL domain names.

First, we need to import Golang's regular expression package, the code is as follows:

import "regexp"

Next, we need a regular expression to verify the URL domain name. Here we use a simple regular expression:

var domainRegex = regexp.MustCompile(`^[a-zA-Zd-]+(.[a-zA-Zd-]+)*.[a-zA-Z]{2,}$`)

This regular expression can match domain names contained in dot delimiters, as well as any characters, including alphanumerics and hyphens. The top-level domain name in this domain name must be composed of two or more letters.

Now we can use this regular expression to verify a given domain name. We can use the following code:

func IsValidDomain(domain string) bool {
  return domainRegex.MatchString(domain)
}

This function will return a Boolean value indicating whether the given domain name is valid. If it is valid it will return True, otherwise it will return False.

Here is a complete sample code:

package main

import (
  "fmt"
  "regexp"
)

var domainRegex = regexp.MustCompile(`^[a-zA-Zd-]+(.[a-zA-Zd-]+)*.[a-zA-Z]{2,}$`)

func IsValidDomain(domain string) bool {
  return domainRegex.MatchString(domain)
}

func main() {
  domains := []string{"github.com", "www.google.com", "bbc.co.uk", "123.45.67.89", "not.a.valid.domain"}
 
  for _, domain := range domains {
    if IsValidDomain(domain) {
      fmt.Println(domain, "is a valid domain")
    } else {
      fmt.Println(domain, "is not a valid domain")
    }
  }
}

When this code is run, it will verify a list of domain names. In this list, the first three domain names are valid. The fourth one is an IP address, not a valid domain name. The last one is not a valid domain name because it contains an invalid character.

Summary:

The above is how to use regular expressions to verify the URL domain name in golang. In this way we can easily verify whether a domain name is valid and legal. This will be a crucial step when implementing a web application. So, now you know what to do when you encounter a situation like this!

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