# std::basic_string<CharT,Traits,Allocator>::c_str

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< cpp‎ | string‎ | basic string

const CharT* c_str() const; |  | (noexcept since C++11) (constexpr since C++20)

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() (since C++11).

Writing to the character array accessed through `c_str()` is undefined behavior.

`c_str()` and data() perform the same function. | (since C++11)

### Parameters

(none)

### Return value

Pointer to the underlying character storage.

c_str()[i] == operator[](i) for every `i` in `[`​0​`,` size()`)`. | (until C++11)
c_str() + i == std::addressof (operator[](i)) for every `i` in `[`​0​`,` size()`]`. | (since C++11)

### Complexity

Constant.

### Notes

The pointer obtained from `c_str()` may only be treated as a pointer to a null-terminated character string if the string object does not contain other null characters.

### Example

Run this code

    #include <algorithm>
    #include <cassert>
    #include <cstring>
    #include <string>

    extern "C" void c_func(const char* c_str)
    {
        printf("c_func called with '%s'\n", c_str);
    }

    int main()
    {
        std::string const s("Emplary");
        const char* p = s.c_str();
        assert(s.size() == std::strlen(p));
        assert(std::equal(s.begin(), s.end(), p));
        assert(std::equal(p, p + s.size(), s.begin()));
        assert('\0' == *(p + s.size()));

        c_func(s.c_str());
    }

Output:

    c_func called with 'Emplary'

### See also

front (DR*) | accesses the first character (public member function)
back (DR*) | accesses the last character (public member function)
data | returns a pointer to the first character of a string (public member function)

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