#!/bin/bash

sleep 1 &
PID=$!

kill -0 $PID
echo $? #expect 0

while kill -0 $PID > /dev/null 2>&1; do
  wait $PID
done
echo $PIPESTATUS $? #expect 1 0

kill -0 $PID > /dev/null 2>&1
echo $? #expect 1


sleep 1 &
PID=$!

until ! kill -0 $PID > /dev/null 2>&1; do
  echo $? #expect 1
  wait $PID
done
echo $PIPESTATUS $? #expect 1 0

sleep 1 &
PID=$!

kill -15 $PID
wait $PID

echo $? #expect 143