How find out a process piping into another process?

Question

I have long running process which is reading from STDIN. However I am not sure which process is piping data into it. The process creation is handled by a process manager and I have no control over it. I tried using lsof to figure it out, but I could not.

What would be a standard way to figure the process-id of the piping process?

Answer 1

This will give you what you want

pid=<THEPIDYOUWANT>; lsof | grep "$(lsof -nPFti -p $pid | grep -A1 tFIFO | sed -En 's/^i(.*)$/\1/p')"

the list of processes using the pipe will appear and from FD you can tell which one reads or writes.