# std::shared_future<T>::wait_until

From cppreference.com
< cpp‎ | thread‎ | shared future

template< class Clock, class Duration > std::future_status wait_until( const std::chrono::time_point<Clock,Duration>& timeout_time ) const; |  | (since C++11)

`wait_until` waits for a result to become available. It blocks until specified `timeout_time` has been reached or the result becomes available, whichever comes first. The return value indicates why `wait_until` returned.

If the future is the result of a call to async that used lazy evaluation, this function returns immediately without waiting.

The behavior is undefined if valid() is false before the call to this function, or `Clock` does not meet the Clock requirements. The programs is ill-formed if std::chrono::is_clock_v<Clock> is false. (since C++20)

### Parameters

timeout_time | - | maximum time point to block until

### Return value

Constant | Explanation
`future_status::deferred` | The shared state contains a deferred function using lazy evaluation, so the result will be computed only when explicitly requested
`future_status::ready` | The result is ready
`future_status::timeout` | The timeout has expired

### Exceptions

Any exception thrown by clock, time_point, or duration during the execution (clocks, time points, and durations provided by the standard library never throw)

### Notes

The implementations are encouraged to detect the case when valid() == false before the call and throw a std::future_error with an error condition of `future_errc::no_state`.

The standard recommends that the clock tied to `timeout_time` be used to measure time; that clock is not required to be a monotonic clock. There are no guarantees regarding the behavior of this function if the clock is adjusted discontinuously, but the existing implementations convert `timeout_time` from `Clock` to std::chrono::system_clock and delegate to POSIX `pthread_cond_timedwait` so that the wait honors adjustments to the system clock, but not to the user-provided `Clock`. In any case, the function also may wait for longer than until after `timeout_time` has been reached due to scheduling or resource contention delays.

### Example

| This section is incomplete Reason: no example

### See also

wait | waits for the result to become available (public member function)
wait_for | waits for the result, returns if it is not available for the specified timeout duration (public member function)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/thread/shared_future/wait_until&oldid=132985"