compare response of gprs module when i send specific AT command

I am using A6 module.. i only want to compare after at+cipsend...with all commands are giving me a OK response..i compared this with "ok" string that is working and after that i need to empty that string otherwise string size would be a more...

void ShowSerialData()
{
  while(SIM900.available()!=0) {
  val=char (SIM900.read());
      readstr+=val;
      if(val=='\n'){
      Serial.println(readstr);           
      if (readstr == "OK\r\n"){
       Serial.println("String sent");
    }     
        readstr="";
      }
  
  }
}

in loop code:

 Serial.print("AT+CIPSEND\\r\\n");
  SIM900.println("AT+CIPSEND"); /* Send data through TCP connection */
  delay(2000);
  ShowSerialData();

got the solution..thanks all of you