# std::counting_semaphore<LeastMaxValue>::try_acquire_until

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< cpp‎ | thread‎ | counting semaphore

template<class Clock, class Duration> bool try_acquire_until( const std::chrono::time_point<Clock, Duration>& abs_time ); |  | (since C++20)

Tries to atomically decrement the internal counter by 1 if it is greater than ​0​; otherwise blocks until it is greater than ​0​ and can successfully decrement the internal counter, or the `abs_time` time point has been passed.

The programs is ill-formed if std::chrono::is_clock_v<Clock> is false.

### Preconditions

`Clock` meets the Clock requirements.

### Parameters

abs_time | - | the earliest time the function must wait until in order to fail

### Return value

true if it decremented the internal counter, otherwise false

### Exceptions

May throw std::system_error or a timeout-related exception.

### Notes

In practice the function may take longer than `abs_time` to fail.

### See also

release | increments the internal counter and unblocks acquirers (public member function)
acquire | decrements the internal counter or blocks until it can (public member function)
try_acquire | tries to decrement the internal counter without blocking (public member function)
try_acquire_for | tries to decrement the internal counter, blocking for up to a duration time (public member function)

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