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_pid #my_prog still has data in its buffer that awk never saw. Data is lost!

In bash, $my_pid points to the PID for awk. However, I need the PID for my_prog. If I kill awk, my_prog does not know to flush it's output buffer and data is lost. So, how would one obtain the PID for my_prog? Note that ps aux|grep my_prog will not work since there may be several my_prog's going.

NOTE: changed cat to awk '...' to help clarify what I need.

Answer 1

Just had the same issue. My solution:

process_1 | process_2 &
PID_OF_PROCESS_2=$!
PID_OF_PROCESS_1=`jobs -p`

Just make sure process_1 is the first background process. Otherwise, you need to parse the full output of jobs -l.

Answer 2

I was able to solve it with explicitly naming the pipe using mkfifo.

Step 1: mkfifo capture.

Step 2: Run this script

my_prog > capture &
my_pid="$!" #Now, I have the PID for my_prog!
awk '...' capture > out.csv & 
sleep 10
kill $my_pid #kill my_prog
wait #wait for awk to finish.

I don't like the management of having a mkfifo. Hopefully someone has an easier solution.