World's smallest chat

I was goofing around and someone set up a Linux VM and invited everyone to log in over ssh. I think his goal was to make a bullet-proof Linux setup. Something that would withstand users deliberately trying to bring the computer down.

BTW, the world's smallest formbomb is

:(){ :|:& };:
But you protect against it by putting soft and hard limits on the number of processes via limits.conf.

Anyway, back to the fun and games. The admin had removed wall (for obvious reasons) and didn't have a talkd. This meant we couldn't talk to each other. So I cooked up the World's Smallest Chat.

In one window, you start the chat with

echo "First line of chat" >/tmp/chat
chmod og+rw /tmp/chat

Then in another window:

tail -F /tmp/chat

Everyone can post to the chat with

echo I don't think so >/tmp/chat

However, anyone can DOS the chat with

yes >>/tmp/chat

But given how this is a chat in 4 lines of code, I don't see that as being a problem.