#define BUF_SIZE 1200

char buf[BUF_SIZE] = {0};
char inChar;
bool stringComplete = false;
int i = 0;

void setup() {
  Serial.begin(9600);
  Serial.println("Please input:");
}

void loop() {
  while (Serial.available())
  {
    inChar = (char) Serial.read();

    if (inChar == '\n') {
      if (i < BUF_SIZE) {
        buf[i++] = inChar;
      }
      buf[i] = 0;
      stringComplete = true;
    } else if (i < BUF_SIZE) {
      buf[i++] = inChar;
    }
  }

  if (stringComplete) {
    Serial.print("Size of input data=");
    Serial.print(i);
    Serial.println("characters");
    Serial.print("");
    Serial.print(buf);

    stringComplete = false;
    i = 0;

    Serial.println("\nPlease input again:");
  }
}