const int trig_pin = 3,
echo_pin = 2
;

unsigned long prev_time = millis();

void setup(){
  pinMode(trig_pin, OUTPUT);
  pinMode(echo_pin, INPUT);
  Serial.begin(9600);
}

void loop(){
  // transmission...
  digitalWrite(trig_pin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig_pin, LOW);

  // reception...
  int duration = pulseIn(echo_pin, HIGH);

  // showing data
  unsigned long crnt_time = millis();
  if(crnt_time - prev_time >= 1000){
    char buffer[25];
    sprintf(buffer, "Distance (cm) = %d", duration/58);
    Serial.println(buffer);
  }
}

/*
The above code doesnt work on actual hardware, the following one does

const int trig_pin = 7,
echo_pin = 6
;

unsigned long prev_time = millis();

void setup(){
  pinMode(trig_pin, OUTPUT);
  pinMode(echo_pin, INPUT);
  Serial.begin(9600);
}

void loop(){
  // transmission...
  digitalWrite(trig_pin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig_pin, LOW);

  // reception...
  int duration = pulseIn(echo_pin, HIGH);

  // showing data
  unsigned long crnt_time = millis();
  if(crnt_time - prev_time >= 740){
    char buffer[25];
    sprintf(buffer, "Distance (cm) = %d", duration/58);
    Serial.println(buffer);
    prev_time = crnt_time;
  }
  delay(10);
}
*/