Linux – Netstat continuous refresh (watch changes the output)

debianlinuxnetstat

I am using this simple command to monitor connections (to deal with some recent DoS attacks) on my Debian server:

netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n

How do I run it continuously? So it will refresh itself once per minute (or any given amount of time, of course). I tried watch:

watch -n 30 "netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n"

But it changed the output from nice list with num of connections to something like this:

1 tcp        0  10015 [LOCAL IP]
...
1 Proto Recv-Q Send-Q Local Address           Foreign Address         State
1 Active Internet connections (w/o servers)

So external IP is not being displayed. Is there something I missed?

This is how the original output looks:

  2 [IP ADDRESS]
  4 [IP ADDRESS]
  4 [IP ADDRESS]
  4 [IP ADDRESS]
  7 [IP ADDRESS]
 16 [IP ADDRESS]
 71 [IP ADDRESS]

And when I say [LOCAL IP] I mean my machine's IP.

When I run it with -c it just freezes.

Best Answer

netstat -c

may help you if i've not misunderstood your problem. -c stands for --continuous.

EDIT: there you go:

watch -n 30 "netstat -ntu | awk '{print \$5}' | cut -d: -f1 | sort | uniq -c | sort -n"

I've added a \ before $.

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