# std::literals::chrono_literals::operator""us

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< cpp‎ | chrono

Defined in header `<chrono>` |  |
constexpr std::chrono::microseconds operator ""us( unsigned long long us ); | (1) | (since C++14)
constexpr std::chrono::duration</*unspecified*/, std::micro> operator ""us( long double us ); | (2) | (since C++14)

Forms a std::chrono::duration literal representing microseconds.

1) integer literal, returns exactly std::chrono::microseconds(us)
2) floating-point literal, returns a floating-point duration equivalent to std::chrono::microseconds

### Parameters

us | - | the number of microseconds

### Return value

The std::chrono::duration literal.

### Possible implementation

    constexpr std::chrono::microseconds operator ""us(unsigned long long us)
    {
        return std::chrono::microseconds(us);
    }
    constexpr std::chrono::duration<long double, std::micro> operator ""us(long double us)
    {
        return std::chrono::duration<long double, std::micro>(us);
    }

### Notes

This operator is declared in the namespace std::literals::chrono_literals, where both literals and chrono_literals are inline namespaces. Access to this operator can be gained with:

- using namespace std::literals,
- using namespace std::chrono_literals, or
- using namespace std::literals::chrono_literals.

In addition, within the namespace std::chrono, the directive using namespace literals::chrono_literals; is provided by the standard library, so that if a programmer uses using namespace std::chrono; to gain access to the classes in the chrono library, the corresponding literal operators become visible as well.

### Example

Run this code

    #include <iostream>
    #include <chrono>

    int main()
    {
        using namespace std::chrono_literals;
        auto d1 = 250us;
        std::chrono::microseconds d2 = 1ms;
        std::cout << "250us = " << d1.count() << " microseconds\n"
                  << "1ms = " << d2.count() << " microseconds\n";
    }

Output:

    250us = 250 microseconds
    1ms = 1000 microseconds

### See also

(constructor) | constructs new duration (public member function of `std::chrono::duration<Rep,Period>`)

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