How do I check if a string is a substring of another string in Go? For example, I want to check someString.contains("something").
2 Answers
Use the function Contains from the strings package.
import ( "strings" ) strings.Contains("something", "some") // true To compare, there are more options:
import ( "fmt" "regexp" "strings" ) const ( str = "something" substr = "some" ) // 1. Contains res := strings.Contains(str, substr) fmt.Println(res) // true // 2. Index: check the index of the first instance of substr in str, or -1 if substr is not present i := strings.Index(str, substr) fmt.Println(i) // 0 // 3. Split by substr and check len of the slice, or length is 1 if substr is not present ss := strings.Split(str, substr) fmt.Println(len(ss)) // 2 // 4. Check number of non-overlapping instances of substr in str c := strings.Count(str, substr) fmt.Println(c) // 1 // 5. RegExp matched, _ := regexp.MatchString(substr, str) fmt.Println(matched) // true // 6. Compiled RegExp re = regexp.MustCompile(substr) res = re.MatchString(str) fmt.Println(res) // true Benchmarks: Contains internally calls Index, so the speed is almost the same (btw Go 1.11.5 showed a bit bigger difference than on Go 1.14.3).
BenchmarkStringsContains-4 100000000 10.5 ns/op 0 B/op 0 allocs/op BenchmarkStringsIndex-4 117090943 10.1 ns/op 0 B/op 0 allocs/op BenchmarkStringsSplit-4 6958126 152 ns/op 32 B/op 1 allocs/op BenchmarkStringsCount-4 42397729 29.1 ns/op 0 B/op 0 allocs/op BenchmarkStringsRegExp-4 461696 2467 ns/op 1326 B/op 16 allocs/op BenchmarkStringsRegExpCompiled-4 7109509 168 ns/op 0 B/op 0 allocs/op 
