function Update () {
    var controller : CharacterController = GetComponent(CharacterController);
    if (controller.isGrounded)
        print("We are grounded");
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Update() {
        CharacterController controller = GetComponent<CharacterController>();
        if (controller.isGrounded)
            print("We are grounded");
        
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Update():
        controller as CharacterController = GetComponent[of CharacterController]()
        if controller.isGrounded:
            print('We are grounded')