const char msg[] = "#HEAD hello mate\n1 2 3\nA B C\n";

bool checkLine(char* str, char last* = '\n', char first = NULL) {
  char *cpos = strchr(str, last);
  int n = (cpos-str);

  if ((first != NULL) && (str[0] != first)) return false;

  if (cpos) {
    if (n > 32) return false;
    char buf[n] = {'\0'};
    strncpy(buf, str, n);
    Serial.print("buf: '"); Serial.print(buf); Serial.println("'");
  }
  return false;
}

void myFunc(char* str, char c) {
    char* ptr;
    int index;

    ptr = strchr(str, c);
    if (ptr == NULL) return;

    index = ptr - str;
    Serial.print("The index is: "); Serial.println(index);
    //ASSERT(str[index] == c);  // Verify that the character at index is the one we want.
}

void setup() {
  Serial.begin(9600);
  
  //myFunc(msg, '\n');
  checkLine(msg, '#');
  while(1) delay(1);

  char *p;
  p = msg;
  char *delim2, *delim = strchr(msg, '#');
  if (delim) {
    delim2 = strchr(delim, '\n');
    Serial.println(delim);
    Serial.println(delim2);
  }

  char *d2, *d = strchr(msg, '#');
  if (d) {
    d2 = strchr(d, ' ');
    *d2 = '\0';
    Serial.print("'"); Serial.print(d); Serial.println("'");
    if (strcmp(*d, "#HEAD")==0)
      Serial.println("MATCH!");
    //*(d + strchr(d, '\n')) = '\0';
  }

  //p += delim;
  
}

void loop() {
  // put your main code here, to run repeatedly:

}