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I am writing a script that ssh's into another machine and opens a netcat server. The server needs to be able to timeout.

Using -l ignores -w.

The command netcat -w 3 throws the usage back at me.

How can I accomplish this?

  • timeout 3 thatcommandthatneedstotimeout – thrig Jan 27 '17 at 18:12
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Here's a hack that can do what you want:

nc -l 12345 & NC_PID=$! ; sleep 3; if [ `netstat -ant | grep ':12345 .*ESTABLISHED'` -eq 0 ]; then kill -9 $NC_PID; fi

It starts the server, sleeps for whatever your timeout is, and then kills the netcat unless there is an established connection. There is a slight risk of having the server hang if there is an existing connection where the remote port matches your listener, but that would be bad luck.

Note: I tested this on a CentOS Linux, so the code is not fully portable, but the idea should be implementable on any *nix machine.

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