It is nice for a basic port knocking as well. timeout 5s bash -c "echo >/dev/tcp/google.com/443" && echo "port open" || echo "port closed" This uses the ti

It is nice for a basic port knocking as well. timeout 5s bash -c "echo >/dev/tcp/google.com/443" && echo "port open" || echo "port closed" This uses the timeout command from coreutils though, so it is not a pure bash implementation.