//char messageToParse[] = "a b/c/d e f/g";

char messageToParse[] = "$GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39";

const char* tokenSeparators = " ";
const char* itemSeparators = ",";

void handleItem(char* item) {
  Serial.print("\t\t➜");
  Serial.println(item);
}

void split(char* message, bool itemLevel = false) {
  char * tokenPtr = nullptr;
  char * startPtr = message;
  if (itemLevel) Serial.write('\t');
  Serial.print("parsing "); Serial.println(message);
  do {
    tokenPtr = strpbrk(startPtr, itemLevel ? itemSeparators : tokenSeparators);
    if (tokenPtr != nullptr) {
      char tmpChar = *tokenPtr;
      *tokenPtr = '\0';
      if (itemLevel) handleItem(startPtr); else split(startPtr, true);
      *tokenPtr = tmpChar; // restore the string
      startPtr = tokenPtr + 1; // get ready for the next token
    } else if (itemLevel) handleItem(startPtr); else split(startPtr, true);
  } while (tokenPtr != nullptr);
}

void setup() {
  Serial.begin(115200); Serial.println();
  split(messageToParse);
}

void loop() {}