# How to find the first index value in slice of bytes in Golang?

In Golang, slice of bytes is a very common data structure that is used to store and manipulate data. It is a variable-length array of bytes that can be resized, making it a flexible and powerful data structure.

Sometimes, we need to find the first index value of a specific byte in a slice of bytes. In this article, we will see how to find the first index value in a slice of bytes in Golang.

## Step 1: Create a Slice of Bytes

Let's create a slice of bytes to work with. We can create a slice of bytes using the make() function, which takes two arguments - the type of slice and the length of the slice.

### Example

Here's an example −

package main

import "fmt"

func main() {
slice := make([]byte, 10)
fmt.Println(slice)
}


### Output

[0 0 0 0 0 0 0 0 0 0]


## Step 2: Set Byte Values in Slice

Next, we will set some byte values in the slice so that we can search for the first index value of a specific byte.

### Example

package main

import "fmt"

func main() {
slice := make([]byte, 10)

for i := range slice {
slice[i] = byte(i)
}

fmt.Println(slice)
}


### Output

[0 1 2 3 4 5 6 7 8 9]


## Step 3: Find the First Index Value

To find the first index value of a specific byte, we can use the IndexByte() function from the bytes package. The IndexByte() function takes two arguments - the slice of bytes and the byte value to search for. It returns the index value of the first occurrence of the byte value in the slice of bytes.

### Example

package main

import (
"bytes"
"fmt"
)

func main() {
slice := make([]byte, 10)

for i := range slice {
slice[i] = byte(i)
}

index := bytes.IndexByte(slice, 5)
fmt.Println(index)
}


### Output

5


In this example, we searched for the first index value of byte 5 in the slice of bytes, which is at index 5.

## Conclusion

Finding the first index value of a byte in a slice of bytes is easy in Golang using the IndexByte() function from the bytes package. With this function, we can quickly find the first occurrence of a specific byte in a slice of bytes, which is a useful operation in many applications.

Updated on: 05-May-2023

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