int sw = 2;
int relay =4;
int bs = 0;
void setup() {
  Serial.begin(9600);
  pinMode(relay,OUTPUT);
  pinMode(sw,INPUT);
}

void loop() {
  bs = digitalRead(sw);
  Serial.print("status = ");
  Serial.println(bs);
  delay(500); 
  if(bs == HIGH)
  {
    digitalWrite(relay,HIGH);

  }
  else{
    digitalWrite(relay,LOW);
  }
}