How to use regular expressions in Go language to determine whether a string is a legal URL

How to use regular expressions in Go language to determine whether a string is a legal URL

In our daily program development, we often need to determine whether a string is a legal URL. The Go language provides support for regular expressions, and we can use regular expressions to determine the legitimacy of the URL. Below we will introduce how to use regular expressions in Go language to determine whether a string is a legal URL, and attach a code example.

First, we need to import the Go language regular expression library regexp. The code is as follows:

import (
    "regexp"
)

Next, we need to define a regular expression used to represent the URL. Regular expressions for URLs can take many forms. Here we use a simple regular expression to determine the legitimacy of the URL. The code is as follows:

var urlRegex = regexp.MustCompile(`^(http|https)://[a-zA-Z0-9-.]+.[a-zA-Z0-9]{2,}(:[0-9]{2,5})?(/[a-zA-Z0-9#]+/?)*(?.+)?$`)

The meaning of the above regular expression is:

• ^(http|https): starts with http or https;
• ://: Matches the :// character;
• [a-zA-Z0-9-.] : Matches one or more letters and numbers , a combination of hyphens and dots, indicating a domain name;
• .[a-zA-Z0-9]{2,}: matches one or more combinations of letters and numbers, indicating Top-level domain name;
• (:[0-9]{2,5})?: Matches a combination of one or more numbers, indicating the port number. This part can be omitted;
• (/[a-zA-Z0-9#] /?)*: matches one or more combinations of letters, numbers and # characters, indicating a path . The path part can be omitted;
• (?. )?: matches characters starting with ?, indicating query parameters. This part can be omitted;
• $: indicates the end of the string.

Next, we can write a function to determine whether the given string is a legal URL. The code is as follows:

func isURLValid(url string) bool {
    return urlRegex.MatchString(url)
}

The above function uses the MatchString method of regular expressions to perform matching judgment. If the given string conforms to the rules of the regular expression, it returns true, otherwise it returns false.

The following is a sample program that shows how to use the above function to determine whether a string is a legal URL. The code is as follows:

package main

import (
    "fmt"
    "regexp"
)

var urlRegex = regexp.MustCompile(`^(http|https)://[a-zA-Z0-9-.]+.[a-zA-Z0-9]{2,}(:[0-9]{2,5})?(/[a-zA-Z0-9#]+/?)*(?.+)?$`)

func isURLValid(url string) bool {
    return urlRegex.MatchString(url)
}

func main() {
    url := "https://www.example.com"
    fmt.Printf("The URL '%s' is valid: %v
", url, isURLValid(url))

    url = "invalid_url"
    fmt.Printf("The URL '%s' is valid: %v
", url, isURLValid(url))
}

Run the above example program and the following results will be output:

The URL 'https://www.example.com' is valid: true
The URL 'invalid_url' is valid: false

Through the above example, we can see how to use regular expressions to determine whether a string is a legal URL. In actual development, we can adjust the regular expression rules to make judgments according to our own needs. Of course, we can also use other methods to determine whether a string is a legal URL, and regular expressions are just one of them.

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