Network in the Shell - revisited

My long-time reader Lars Timmann pointed me to a another really cool usecase of the /dev/tcp pseudo device in the bash shell. You can use it to proxy ssh connections though a jump host without the need to have nc on it. He writes in a Facebook comment:

I use it in ~/.ssh/config like this:
Host host-a
ProxyCommand ssh host-b "/bin/bash -c 'exec 3<>/dev/tcp/%h/%p; cat <&3 &amp; cat >&3;'"
So there i no need for netcat on any host to use it as jump host <img src="" alt=":-)" class="emoticon" />.