How to convert variable number of elements of char array to string

char* data = ...;
int size = 4;
std::string str(data, size);

It's elegant with constructor of std::string.

What you want is the substr method of std::string.

You can convetr the char[] to an std::string, and then use substr to get the sub-string you want.

std::string str("The quick brown fox jumps over the lazy dog");
std::cout << str.substr(0, 9);

Output would be:

The quick

char arr[m];
std::string str="";
for(int i = 0; i < n; i++) {
    str += arr[i];
}

I have assumed that you would like to convert first n element of char aar into string.

Or

char* inp = ..;
int size = 4; // int size = 5;
std::string str(inp, size);