How to print a byte array as binary in golang?

Question

How to print a byte array []byte{255, 253} as binary in Golang?

I.e.

[]byte{255, 253} --> 1111111111111101

By the way, that's a slice, not an array. In Go an array is an actual datatype different from slice and not just some vague list-like thing: https://stackoverflow.com/a/11737218/242457 — David Jones, Mar 27 '23 at 15:55

score 21 · Answer 1 · edited Feb 23 '23 at 10:55

21

Simplest way I have found:

package main

import "fmt"

func main() {
    bs := []byte{0x00, 0xfd}
    for _, n := range(bs) {
        fmt.Printf("%08b ", n) // prints 00000000 11111101
    }
}

Playground with this code: https://go.dev/play/p/piJV_3OTHae

edited Feb 23 '23 at 10:55

Becir

3
2

answered Aug 03 '17 at 18:41

Pylinux

11,278
4
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There's also `strconv.FormatUint` if you want the string, but same idea. – JimB Aug 03 '17 at 19:25
1

@JimB Do you have a playground with an example of `strconv.FormatUint` for printing binary? – Pylinux Aug 04 '17 at 20:40
OK, so it's a replacement for the `fmt.Printf`, I was hoping it was a replacement for the for-loop:-) – Pylinux Aug 05 '17 at 22:13

score 1 · Answer 2 · answered May 11 '21 at 17:34

Or use this simple version

func printAsBinary(bytes []byte) {

    for i := 0; i < len(bytes); i++ {
        for j := 0; j < 8; j++ {
            zeroOrOne := bytes[i] >> (7 - j) & 1
            fmt.Printf("%c", '0'+zeroOrOne)
        }
        fmt.Print(" ")
    }
    fmt.Println()
}

[]byte{0, 1, 127, 255} --> 00000000 00000001 01111111 11111111

David Jones · Accepted Answer · 2023-04-04T12:10:30.567

1

fmt.Printf can print slices and arrays and applies the format to the elements of the array. This avoids the loop and gets us remarkably close:

package main

import "fmt"

func main() {
    bs := []byte{0xff, 0xfd}
    fmt.Printf("%08b\n", bs) // prints [11111111 11111101]
}

Playground with above code: https://go.dev/play/p/8RjBJFFI4vf

The extra brackets (which are part of the slice notation) can be removed with a strings.Trim():

fmt.Println(strings.Trim(fmt.Sprintf("%08b", bs), "[]")) // prints 11111111 11111101

edited Apr 04 '23 at 12:10

answered Mar 27 '23 at 15:52

David Jones

4,766
3
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1

This was a really good solution, thanks for adding it! I selected it as the accepted answer. BTW; do the answer need the strings.Trim() part? I feel the answer would be more concise without it – Pylinux Mar 28 '23 at 10:44
well, i tried to make it clear that the `strings.Trim()` was an optional extra. – David Jones Mar 28 '23 at 12:57
Don't mind me; it's still an excelent answer:-) – Pylinux Mar 29 '23 at 18:05

How to print a byte array as binary in golang?

3 Answers3