std::basic_string<CharT,Traits,Allocator>::back - cppreference.com

From cppreference.com

	(1)	(constexpr since C++20)
const CharT& back() const;	(2)	(constexpr since C++20)

Returns reference to the last character in the string.

If empty() is true, the behavior is undefined.

(until C++26)

If empty() is true:

If the implementation is hardened, a contract violation occurs.
If the implementation is not hardened, the behavior is undefined.

(since C++26)

Return value

operator[](size() - 1)

Complexity

Constant.

Notes

In libstdc++, back() is not available in C++98 mode.

Example

#include <iostream>
#include <string>

int main()
{
    std::string s("Exemplary");
    char& back1 = s.back();
    back1 = 's';
    std::cout << s << '\n'; // "Exemplars"
    
    std::string const c("Exemplary");
    char const& back2 = c.back();
    std::cout << back2 << '\n'; // 'y'
}

Output:

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 534	C++98	std::basic_string did not have the member function `back()`	added