In Linux if you go digging in /proc/<pid>/fd often you'll see output like:

lrwx------ 1 root root 64 Jul 30 15:14 0 -> /dev/null
lrwx------ 1 root root 64 Jul 30 15:14 1 -> /dev/null
l-wx------ 1 root root 64 Jul 30 15:14 10 -> pipe:[90222668]
lr-x------ 1 root root 64 Jul 30 15:14 11 -> pipe:[90222669]
l-wx------ 1 root root 64 Jul 30 15:14 13 -> pipe:[90225058]
lr-x------ 1 root root 64 Jul 30 15:14 14 -> pipe:[90225059]

How do I get more info about the open pipes, such as which process is on the other end?

  • lsof, of finding in whole /proc is slow. Can someone provide a more effective solution? – pihentagy May 14 '14 at 14:09

Similiar to other answers, but:

lsof | grep 90222668

Will show you both ends, because both ends share the 'pipe number'.

  • 4
    Ah, of course. Works as expected. You can even tell the file descriptor number and which end is the reader and which is the writer by looking at the 4th column of output! – Kamil Kisiel Jul 31 '09 at 18:07
  • I think that number might be the inode number of the pipe for pipefs which you can't mount. I am looking for a way to get inode to filename mappings, but this might be the best way. By the way, I love this question :-) – Kyle Brandt Jul 31 '09 at 18:24
  • Somehow this is not working for me. All it outputs is the pipe itself. – Rui Marques Mar 17 '14 at 10:23
  • running lsof as standard user may not give you information from all processes. Usually you don't have permission to see all processes' /proc/<pid>/fd directory as a non-root user. – Andre Holzner Jun 3 '16 at 10:35
  • 6
    Also, you might want to use lsof -n -P | grep 90222668 to avoid unnecessary name lookups, which should speed it up. – Wodin Oct 14 '16 at 11:48

The only way to find what process is on the other end is by looping over all processes in /proc and seeing which are using that pipe (ie, which have symlinks in /proc/pid/fd to the same pipe ID)

  • Thanks for the tip. One way to automate this is: ls -l /proc/*/fd/ | grep $PIPE_ID; ls -l /proc/*/fd/$FD | grep $PIPE_ID The first ls command will print the file descriptors of both ends of the pipe, while the second will give you the process id – Joao Costa Jan 25 '16 at 9:17

The most information I know how to get on open pipes is

lsof|grep FIFO

Still only tells about one end of it, I'm afraid.

  • That's about the same as I can divine from /proc, I assume lsof gets it from the same location. – Kamil Kisiel Jul 30 '09 at 22:41
lsof +E | grep FIFO | grep 90222668

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