std::basic_string<CharT,Traits,Allocator>::c_str
(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.
[edit] Parameters
(none)
[edit] Return value
Pointer to the underlying character storage.
c_str()[i] == operator[](i) for every i in [0, size()).
c_str() + i == std::addressof (operator[](i)) for every i in [0, size()].
[edit] Complexity
Constant.
[edit] 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.
[edit] 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円' == *(p + s.size())); c_func(s.c_str()); }
Output:
c_func called with 'Emplary'