Simple bash function to watch the output of a command and show it when the output changes

watch-output.sh

function watch_change() {
  local stat
  local oldstat
  local lasttime
  lasttime=$SECONDS
  while true; do
    stat="$(eval "$@")"
    if [[ "$stat" != "$oldstat" ]]; then
      oldstat="$stat"
      diff=$((SECONDS-lasttime))
      echo -e "\n---\nChanged: (+$diff s)\n$stat"
      lasttime=$SECONDS
    fi
    sleep 0.1
  done
}

watch_change "sudo netstat -tulpena | grep -i Sample"