basic_signal_set::basic_signal_set (2 of 4 overloads)

Construct a signal set and add one signal.

basic_signal_set(
    asio::io_service & io_service,
    int signal_number_1);

This constructor creates a signal set and registers for one signal.

io_service: The io_service object that the signal set will use to dispatch handlers for any asynchronous operations performed on the set.
signal_number_1: The signal number to be added.

This constructor is equivalent to performing:

asio::signal_set signals(io_service);
signals.add(signal_number_1);