How to assign string to bytes array

Question

I want to assign string to bytes array:

var arr [20]byte
str := \"abc\"
for k, v := range []byte(str) {
  arr[k] = byte(v)
}

Have another m

Answer 1

For converting from a string to a byte slice, string -> []byte:

[]byte(str)

For converting an array to a slice, [20]byte -> []byte:

arr[:]

For copying a string to an array, string -> [20]byte:

copy(arr[:], str)

Same as above, but explicitly converting the string to a slice first:

copy(arr[:], []byte(str))

---

• The built-in copy function only copies to a slice, from a slice.
• Arrays are "the underlying data", while slices are "a viewport into underlying data".
• Using [:] makes an array qualify as a slice.
• A string does not qualify as a slice that can be copied to, but it qualifies as a slice that can be copied from (strings are immutable).
• If the string is too long, copy will only copy the part of the string that fits.

---

This code:

var arr [20]byte
copy(arr[:], "abc")
fmt.Printf("array: %v (%T)\n", arr, arr)

...gives the following output:

array: [97 98 99 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] ([20]uint8)

I also made it available at the Go Playground