KeyCode.B

Description

'b' key.

//Attach this to a GameObject
//This script tells when the B arrow key is pressed down and when it is released
using UnityEngine;

public class Example : MonoBehaviour
{
    void Update()
    {
        //Detect when the B arrow key is pressed down
        if (Input.GetKeyDown(KeyCode.B))
            Debug.Log("B key was pressed.");

        //Detect when the B arrow key has been released
        if (Input.GetKeyUp(KeyCode.B))
            Debug.Log("B key was released.");
    }
}