I check for a listening port on a service prior to running a script using this :

until nc -z $HOST $PORT
  echo "waiting for service to be available..."
  sleep 0.5

exec "/my/script"

It used to work with gnu-netcat, but now, I've upgraded the Linux distribution, and it uses nmap-ncat for the /usr/bin/nc command.

I'd like to know an equivalent solution to use with nmap-ncat package.


--send-only </dev/null seems to do the trick.

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