got signal
trap -- 'echo got signal' USR1
sent 1 signal
got signal
wait interrupted
trap -- 'echo got signal' USR1
sent 2 signal
got signal
wait interrupted
trap -- 'echo got signal' USR1
sent 3 signal
got signal
wait interrupted
trap -- 'echo got signal' USR1
sent 4 signal
got signal
wait interrupted
trap -- 'echo got signal' USR1
sent 5 signal
sleep completed