# std::shared_ptr<T>::unique

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< cpp‎ | memory‎ | shared ptr

bool unique() const noexcept; |  | (deprecated in C++17) (removed in C++20)

Checks if *this is the only `shared_ptr` instance managing the current object, i.e. whether use_count() == 1.

### Parameters

(none)

### Return value

true if *this is the only `shared_ptr` instance managing the current object, false otherwise.

### Notes

This function was deprecated in C++17 and removed in C++20 because use_count is only an approximation in multithreaded environment (see Notes in use_count).

### Example

Run this code

    #include <iostream>
    #include <memory>

    int main()
    {
        auto sp1 = std::make_shared<int>(5);
        std::cout << std::boolalpha;
        std::cout << "sp1.unique() == " << sp1.unique() << '\n';

        std::shared_ptr<int> sp2 = sp1;
        std::cout << "sp1.unique() == " << sp1.unique() << '\n';
    }

Output:

    sp1.unique() == true
    sp1.unique() == false

### See also

use_count | returns the number of `shared_ptr` objects referring to the same managed object (public member function)

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