How to get the PID of a process in a pipeline

Question

Consider the following simplified example:

my_prog|awk \'...\' > output.csv &
my_pid=\"$!\" #Gives the PID for awk instead of for my_prog
sleep 10
kill $my         


        

Answer 1

Add a shell wrapper around your command and capture the pid. For my example I use iostat.

#!/bin/sh
echo $$ > /tmp/my.pid
exec iostat 1

Exec replaces the shell with the new process preserving the pid.

test.sh | grep avg

While that runs:

$ cat my.pid 
22754
$ ps -ef | grep iostat
userid  22754  4058  0 12:33 pts/12   00:00:00 iostat 1

So you can:

sleep 10
kill `cat my.pid`

Is that more elegant?