From cppreference.com
constCharT*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
,
,
,
,
,
,
and
(since C++11).
Writing to the character array accessed through c_str() is undefined behavior.
c_str() and
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"voidc_func(constchar*c_str){printf("c_func called with '%s'\n",c_str);}intmain(){std::stringconsts("Emplary");constchar*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
(DR*)
accesses the first character
(public member function)
(DR*)
accesses the last character
(public member function)
returns a pointer to the first character of a string
(public member function)