If you take the example test program test_running.cpp and add a asio/signal_set handler to trap Ctrl-C there doesn't appear to be a way to remove the async_monitor operation thus io_service.run() never exits.

In my application our Ctrl-C handler gracefully tells all asio io_objects (timers, sockets) to "shutdown". Then the io_service exits once all the handlers have executed and the program drops out of the bottom of main.

Even calling remove_directory in the Ctrl-C handler appears to keep the work on the queue.