string2char question

Hi all! Newbie here.

Quite new to c / c++. I have a question about the below code:

char* string2char(String command){
    if (command.length() != 0) {
        char *p = const_cast<char*>(command.c_str());
        return p;

void setup() {}

void loop() {
        String string1 = "Bob";
	char *string1Char = string2char(string1);
	String string2 = "Ross";
	char *string2Char = string2char(string2);

This basically outputs repeatedly:


I understand I’m failing to grasp the concept of how pointers are working here - would someone be able to explain it? And how would I alter this so that it could show:


p goes out of scope when the function ends. Anything you do with it after it goes out of scope you do at your own peril.

String's c_str() function returns a pointer to the String's internal buffer. It doesn't make a copy.

What's happening here is that you're passing each String to string2char by copy to its "command" parameter (which is a local variable to string2char), and the lifetime of "command" ends when string2char returns. Any pointer into that object is invalid after that point.

One simple change should fix that:

char* string2char(String& command){

There's another bug, though: What if the command String is empty? string2char doesn't return a value in that case. You need to return a valid pointer (even NULL would be fine, if that's your intention) in all cases.

This basically outputs repeatedly:

Without a Serial.begin() I bet it doesn't

Please explain what you are trying to do