kill not working in while loop

Question

I want to kill all processes given by lsof in a while loop.

this works fine:

lsof -i tcp | grep -v iceweasel | awk '{ print $2 }' | while read -r line
do
    echo "$line"

done;

this one does not:

lsof -i tcp | grep -v iceweasel | awk '{ print $2 }' | while read -r line
    do
        kill "$line"

    done;

The error generated by this last while is:

./kill.all.sh: line 6: kill: PID: arguments must be process or job IDs

any idea? thanks.

Answer 1

The problem is that the output of lsof -i tcp contains the header, and its PID item is eventually passed to the kill command (kill PID) thus causing the error.

Either use -t option for headless output, or ignore the first row with AWK:

awk 'NR > 1 { print $2 }'

where NR is the record (line) number.

Note that kill only sends SIGTERM signal to the process, and the process may merely ignore it. If you want to terminate the process for sure, run kill with -9 (-KILL) option (refer to man 7 signal for signal codes).

Answer 2

Don't reinvent the wheel. For killing all processes which use tcp except iceweasel:

kill $(lsof -c ^iceweasel -a -i tcp -t)