NAME

std::basic_string::c_str - std::basic_string::c_str

Synopsis

const CharT* c_str() const; (until C++11)
const CharT* c_str() const noexcept; (since C++11)
(until C++20)
constexpr const CharT* c_str() const noexcept; (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, (since C++11)
size()].

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'