How to get the PID of a process that is piped to another process in Bash?

Question

I am trying to implement a simple log server in Bash. It should take a file as a parameter and serve it on a port with netcat.

( tail -f $1 & ) | nc -l -         


        

Answer 1

Finally, I have managed to find the tail process using ps. Thanks to the idea from ennuikiller.

I have used the ps to grep tail from the args and kill it. It is kind of a hack but it worked. :)

If you can find a better way please share.

Here is the complete script:
(Latest version can be found here: http://docs.karamatli.com/dotfiles/bin/logserver)

if [ -z "$1" ]; then
    echo Usage: $0 LOGFILE [PORT]
    exit -1
fi
if [ -n "$2" ]; then
    PORT=$2
else
    PORT=9977
fi

TAIL_CMD="tail -f $1"

function kill_tail {
    # find and kill the tail process that is detached from the current process
    TAIL_PID=$(/bin/ps -eo pid,args | grep "$TAIL_CMD" | grep -v grep | awk '{ print $1 }')
    kill $TAIL_PID
}
trap "kill_tail; exit 0" SIGINT SIGTERM

while true; do
    ( $TAIL_CMD & ) | nc -l -p $PORT -vvv
    kill_tail
done