The number of the signal to listen for
Callback that gets called whenever a matching signal gets received
Returns an identifier that identifies the resource associated with the signal. Giving up ownership of this resource using releaseRef will re-enable the default signal handler, if any was present.
For any error condition, SignalListenID.invalid will be returned instead.
Starts listening for the specified POSIX signal.
Note that if a default signal handler exists for the signal, it will be disabled by using this function.