Putting this command into bash script

Question

with help of google , script that measures multicast streams bandwidth.

Here it is tcpdump -tnn -i eth1 -f multicast | sort | uniq -c | awk '{print $3,"> "$5,$1*$NF/2*8/1024 " Kbps"}' | awk '$1 > 10' & sleep 2s && pkill -HUP -f tcpdump

It turns out fine, except I need to hit enter to get back to prompt. I know it is && problem, but dont know how to fix it.

How can I trascribe it to shell script. And maybe add $var for number of seconds.

Answer 1

Try using timeout to kill the tcpdump after a duration:

(timeout -s HUP 2 tcpdump -tnn -i eth1 -f multicast || true) | sort | uniq -c | awk '{print $3,"> "$5,$1*$NF/2*8/1024 " Kbps"}' | awk '$1 > 10' 

To script it:

#!/bin/bash if ! [[ "$1" =~ ^[0-9]+$ ]]; then echo "Usage: $0 <number of seconds>" exit 1 fi (timeout -s HUP $1 tcpdump -tnn -i eth1 -f multicast || true) | sort | uniq -c | awk '{print $3,"> "$5,$1*$NF/2*8/1024 " Kbps"}' | awk '$1 > 10' 

Answer 2

you don't need to press enter to exit. it's just a cosmetical issue here. that is because your output "overwrites" your terminal (you can still enter any command and press enter - it will be executed).

To "fix" this layout issue you can try to append "; sleep 1; echo" to your line so it will look like:

tcpdump -tnn -i eth1 -f multicast | sort | uniq -c | awk '{print $3,"> "$5,$1*$NF/2*8/1024 " Kbps"}' | awk '$1 > 10' & sleep 2s && pkill -HUP -f tcpdump; sleep 1; echo 

Hope that helps.

And here is your bash script with variable:

#!/bin/bash SLEEPTIME=5 tcpdump -tnn -i eth0 -f multicast | sort | uniq -c | awk -v a=$SLEEPTIME '{print $3,"> "$5,$1*$NF/a*8/1024 " Kbps"}' | awk '$1 > 10' & sleep $SLEEPTIME && pkill -HUP -f tcpdump; sleep 1; echo