How to parse a string to an int in C++?

Question

What\'s the C++ way of parsing a string (given as char *) into an int? Robust and clear error handling is a plus (instead of returning zero).

Answer 1

You can use the a stringstream from the C++ standard libraray:

stringstream ss(str);
int x;
ss >> x;

if(ss) { // <-- error handling
  // use x
} else {
  // not a number
}

The stream state will be set to fail if a non-digit is encountered when trying to read an integer.

See Stream pitfalls for pitfalls of errorhandling and streams in C++.