Standard Library
regexp

regexp package

The regexp package implements regular expression search. Its syntax follows the pattern of Perl and Python, more specifically the re2syntax (opens in a new tab) format.

official doc (opens in a new tab)

In the following code snippet, you can see an email regex validation that aims to filter out incorrectly formatted email addresses:

package main
 
import (
	"fmt"
	"regexp"
)
 
func main() {
	// Build a regular expression variable to verify the given string
	var emailRegexp *regexp.Regexp = regexp.MustCompile(`^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$`)
 
	fmt.Println("Checking valid regexps...")
 
	emails := []string{
		"info@followthepattern.net",
		"@followthepattern.net",
		"info@followthepattern",
	}
	for _, mail := range emails {
		// MatchString returns true if the given string passes the match with the regexp
		fmt.Println(mail, emailRegexp.MatchString(mail))
	}
}

You can run the above example here (opens in a new tab).

In this code snippet, we extract values from regexp groups, where a specific format string needs to be parsed to extract valid characters:

package main
 
import (
	"fmt"
	"regexp"
)
 
func main() {
	// Verification code has three elements that need to be parsed
	verificationCode := "e035f36e-b45f4b89a31e-58e1b05706e3"
 
	// Matching regexp
	regexp := regexp.MustCompile(`(?P<part1>[a-z0-9]+)-(?P<part2>[a-z0-9]+)-(?P<part3>[a-z0-9]+)`)
	fmt.Println("Is Match:", regexp.MatchString(verificationCode))
 
	// Read group values into an array
	matches := regexp.FindStringSubmatch(verificationCode)
 
	// Find the index of the group by group name
	part2 := regexp.SubexpIndex("part2")
 
	fmt.Println("Part2 Index:", part2)
	fmt.Println(matches[part2])
}

You can run this code snippet here (opens in a new tab).

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