Go by Example: String Functions

The standard library’s strings package provides many useful string-related functions. Here are some examples to give you a sense of the package.

package main
import s "strings"
import "fmt"

We alias fmt.Println to a shorter name as we’ll use it a lot below.

var p = fmt.Println
func main() {

Here’s a sample of the functions available in strings. Since these are functions from the package, not methods on the string object itself, we need pass the string in question as the first argument to the function. You can find more functions in the strings package docs.

    p("Contains:  ", s.Contains("test", "es"))
    p("Count:     ", s.Count("test", "t"))
    p("HasPrefix: ", s.HasPrefix("test", "te"))
    p("HasSuffix: ", s.HasSuffix("test", "st"))
    p("Index:     ", s.Index("test", "e"))
    p("Join:      ", s.Join([]string{"a", "b"}, "-"))
    p("Repeat:    ", s.Repeat("a", 5))
    p("Replace:   ", s.Replace("foo", "o", "0", -1))
    p("Replace:   ", s.Replace("foo", "o", "0", 1))
    p("Split:     ", s.Split("a-b-c-d-e", "-"))
    p("ToLower:   ", s.ToLower("TEST"))
    p("ToUpper:   ", s.ToUpper("test"))

Not part of strings, but worth mentioning here, are the mechanisms for getting the length of a string in bytes and getting a byte by index.

    p("Len: ", len("hello"))
    p("Char:", "hello"[1])

Note that len and indexing above work at the byte level. Go uses UTF-8 encoded strings, so this is often useful as-is. If you’re working with potentially multi-byte characters you’ll want to use encoding-aware operations. See strings, bytes, runes and characters in Go for more information.

$ go run string-functions.go
Contains:   true
Count:      2
HasPrefix:  true
HasSuffix:  true
Index:      1
Join:       a-b
Repeat:     aaaaa
Replace:    f00
Replace:    f0o
Split:      [a b c d e]
ToLower:    test
ToUpper:    TEST
Len:  5
Char: 101

Next example: String Formatting.