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

const CharT* c_str() const;

const CharT* c_str() const noexcept;

constexpr const CharT* c_str() const noexcept;

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.

Parameters

(none).

Return value

Pointer to the underlying character storage.

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

#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());
}

c_func called with 'Emplary'

See also