byte and rune

Learn byte and rune types and character representation.

byte and rune

Go strings are made of UTF-8 bytes. A byte (uint8) represents a single byte and a rune (int32) a single Unicode character. English letters are 1 byte, but letters such as ğ, ş, ü are 2 bytes.

s := "ağ"
fmt.Println(len(s))          // 3 (bytes)
fmt.Println(len([]rune(s)))  // 2 (characters)

Walking characters with range

for i, r := range s walks a string character by character; i is the character's byte position and r the rune value. Indexing with s[i] gives a single byte and splits multi-byte letters.

for i, r := range "gö" {
    fmt.Println(i, string(r))
}
// 0 g
// 1 ö

Single quotes ('a') make a rune constant.

Exercise Bytes and characters

Declare s := "Gölge". Print the byte count (len(s)) and the character count (len([]rune(s))) on one line.

Show example solution

package main

import "fmt"

func main() {
    s := "Gölge"
    fmt.Println(len(s), len([]rune(s)))
}

Test yourself

What does <code>len("çay")</code> return?
- 6
- 2
- 4
- 3
Show answer

4 — len counts bytes: ç is 2 bytes, a and y one each → 4. For the character count use utf8.RuneCountInString or len([]rune(s)).

Character count

n := len([]____("ışık"))  // 4

Show answer

n := len([]rune("ışık"))  // 4

Type and meaning

byte

A single byte (uint8)
rune

A Unicode character (int32)
'a'

A rune constant
"a"

A string

Next lesson: Type conversion

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