template< typename SignalHandler> void-or-deduced async_wait( SignalHandler handler);
This function may be used to initiate an asynchronous wait against the signal set. It always returns immediately.
For each call to
async_wait(), the supplied handler will be called
exactly once. The handler will be called when:
The handler to be called when the signal occurs. Copies will be made of the handler as required. The function signature of the handler must be:
void handler( const boost::system::error_code& error, // Result of operation. int signal_number // Indicates which signal occurred. );
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
Invocation of the handler will be performed in a manner equivalent