Although there is no standard (POSIX or other) for the layout of the /proc pseudo-filesystem, it turned out a very useful facility in GNU/Linux and other systems, and many tools concerned with process management use it. (ps, top, htop, gtop, killall, pkill, ...)

Instead of porting all these tools to use libps (Hurd's official method for accessing process information), they run out of the box, via the Hurd's Linux-compatible procfs at /proc. (On Linux, the /proc filesystem is used also for debugging purposes; but this is highly system-specific anyways, so there is probably no point in trying to duplicate this functionality as well...)

History of procfs

There was an implementation in HurdExtras, http://www.nongnu.org/hurdextras/#procfs.

Madhusudan.C.S has implemented a new, fully functional procfs for GSoC 2008.

In August 2010, Jérémie Koenig published another, new version. This can be found in https://git.savannah.gnu.org/cgit/hurd/procfs.git/.

Testing it is as simple as this:

$ git clone git://git.savannah.gnu.org/hurd/procfs.git
$ cd procfs/
$ make
$ settrans -ca proc procfs --compatible
$ ls -l proc/

Open issues.