title: Arduino sprintf on char* not change value
body: <p>I want to concat a value to a char* variable (this value come from a sensor and I want make a GET with this value).. but, when I print the value on the Serial Monitar.. the variable not change.. only work the first time..</p>
  
  <p>this the code.. </p>
  
  <pre><code>int sensorValue=0;
  
  void main(){
   Serial.Begin(9600);    
  }
  
  void loop(){
  
   char *hello = "GET /value=%i HTTP/1.1\r\nHost: www.baidu.com\r\nConnection: close\r\n\r\n";
  
   sprintf(hello, hello, sensorValue);
   sensorValue++;
  
  }
  </code></pre>
  
  <p>Then, the Serial Monitor only print:</p>
  
  <pre><code>GET /0 HTTP/1.1\r\nHost: www.baidu.com\r\nConnection: close\r\n\r\n
  GET /0 HTTP/1.1\r\nHost: www.baidu.com\r\nConnection: close\r\n\r\n
  GET /0 HTTP/1.1\r\nHost: www.baidu.com\r\nConnection: close\r\n\r\n
  </code></pre>
  
  <p>.....</p>