接收输入string转char数组

#include<iostream>
#include<string>
using namespace std;

int main()
{
        string str;
        cin >> str;
        const char *c = new char[5];
        c = str.c_str();
        for(int i=0;i<5;i++)
                cout<<c[i];
        cout << endl;
}
结果1.
fds   
fds
结果2.
fdsafdsafdsa
fdsaf