Question

I want to assign string from command line. But I got segmentation fault. why? here is the code:

char* ans;  
cout << "enter string: ";  
cin >> *ans;

update:
how to allocate memory in advance if I don’t know the size of input string,
how it works in String Class?

Answer 1

You have a pointer, but that pointer doesn’t point to anywhere where there’s space allocated for data to be stored. Use std::string instead:

std::string ans;
cout << "enter string: ";  
cin >> ans;

// ...

ans.c_str(); // returns const char *