Convert a String To Byte Array or Slice in Go

To convert a string to byte array or slice in Go language use the below one liner code.

[]byte(string)

We can use byte array to store a collection of binary data, for example, the contents of a file.

The above code to convert string to byte slice is very useful while using ioutil.WriteFile function, which accepts a bytes as its parameter:

WriteFile func(filename string, data []byte, perm os.FileMode) error

We will go through an example to understand it further.

string to byte array example #

When we convert a string to a byte slice (array), we will get a new array that contains the same bytes as the string.

The conversion doesn’t change the string data.

I wrote a go program (‘convert-string-to-byte-array.go’) which convert a string to byte slice and prints it in the command prompt.

The converted byte array contains ASCII values of string characters.

package main

import (
	"fmt"
)

func main() {
	var str string
	str = "string to byte array or slice"
	// converting and printing Byte array
	fmt.Println([]byte(str))
}

Now run the Go program

go run convert-string-to-byte-array.go

output:
[115 116 114 105 110 103 32 116 111 32 98 121 116 101 32 97 114 114 97 121 32 111 114 32 115 108 105 99 101]

byte array with ioutil.WriteFile #

As explained above, converting a string to byte array/slice is very useful while creating files using ioutil.WriteFile function.

The below code creates a new file called hello.txt using byte array.

package main

import (
	"io/ioutil"
	"log"
)

func main() {
	message := []byte("Hello, World!")
	err := ioutil.WriteFile("hello", message, 0644)
	if err != nil {
		log.Fatal(err)
	}
}