Golang Regexp Find Examples: FindAllString

Use the Find and FindAllString funcs on regexp. Loop over the results.

Find. With regexp we are often trying to find strings within a larger string. We use patterns (passed to MustCompile) to determine which values match.

To use Find, we must have byte slices. This is inconvenient in some programs. We can use a method like FindAllString instead, to operate directly on strings.

Find example. Here we use Find. We try to find a 3-digit sequence that begins with the value 2. The Find method returns the leftmost matching sequence as a byte slice.

Important: With byte slices, we must convert them back to strings before printing them. This can be annoying.

Golang program that uses Find package main import ( "fmt" "regexp" ) func main() { // Match 3-digit values starting with 2. re := regexp.MustCompile("2\\d\\d") // Use find to get leftmost match. result := re.Find([]byte("123 124 125 205 211")) // Convert back to string and print it. fmt.Println(string(result)) } Output 205

FindAllString. This func finds multiple matches of a pattern within a string. It returns the values in a slice—we can loop over it with a for-loop.For

String: We operate directly on strings with FindAllString the results are in a slice of strings, so we can print them with no conversion.

Golang program that uses FindAllString package main import ( "fmt" "regexp" ) func main() { // Match 3-char values starting with digit 1. re := regexp.MustCompile("1..") // Find and loop over all matching strings. results := re.FindAllString("123 124 125 200 211", -1) for i := range(results) { fmt.Println(results[i]) } } Output 123 124 125

A review. With Find-methods, we perform a search within the source string—the entire string is not matched as in MatchString(). We can test matches in a for-loop after the method call.Regexp
Dot Net Perls
© 2007-2020 Sam Allen. Every person is special and unique. Send bug reports to