Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm trying to trace some odd behavior of a few processes and ran into a point I'm not sure how to trace past. The hung process, which I attached to using strace -p showed this:

Process 7926 attached - interrupt to quit

Okay, so it's waiting for input on fd 3, so I went to check what it is:

$ ls -l /proc/7926/fd/3
lr-x------ 1 user grp 64 Mar 15 10:41 /proc/7926/fd/3 -> pipe:[20043922]

Okay, so it's a pipe... now the question -- who is the writer of this pipe? I recall that on Linux there is a special feature for unix domain sockets where you can request a file path that starts with a NUL byte to access the "abstract socket namespace" (mentioned here: I'm not sure if there's something similar for pipes that I could take advantage of, but I haven't found anything.

I was hoping a tool like fuser or lsof might help, but I haven't gotten anywhere.

Any ideas?

share|improve this question
up vote 19 down vote accepted

The symlink contents "pipe:[20043922]" are a unique ID; the other end of the pipe will have a matching ID.

(find /proc -type l | xargs ls -l | fgrep 'pipe:[20043922]') 2>/dev/null

should show you both ends of the pipe.

share|improve this answer
Good thinking, thanks! While investigating I also came across this thread here… so I thought I'd drop the link here too just ffr for others too. – FatalError Mar 22 '12 at 13:54

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .