C++：關于string轉C-風格字元串

std::basic_string::c_str

  C++   Strings library   std::basic_string  

const CharT* c_str() const;

Returns a pointer to a null-terminated character array with data equivalent to those stored in the string.

The pointer is such that the range 

[c_str(); c_str() + size()]

 is valid and the values in it correspond to the values stored in the string with an additional null character after the last position.

The pointer obtained from 

c_str()

 may be invalidated by:

• Passing a non-const reference to the string to any standard library function, or
• Calling non-const member functions on the string, excluding operator[], at(), front(), back(), begin(),rbegin(), end() and rend().

Writing to the character array accessed through 

c_str()

 is undefined behavior.

c_str()  and data() perform the same function.

(since C++11)

這裡：

用c_str() 方法可以傳回一個指向C-風格的字元串的指針。

如:

string filename;
cout << "Enter the file name: ":
cin >> filename;
ofstream fout;
fout.open(filename.c_str());