A UserFs filesystem implementation module which makes available common data from the Elixir run time.

The implementation breaks the file path into leaves and the traverse/4 function works through them to find the end of the path.

The traverse/4 function verifies each element of the path as it is called. This is necessary because it is no use continuing past the pids/<0.63.0> point if PID <0.63.0> does not exist! The first two parameters to traverse/4 are passed on and through so they are available when the traversal finishes, the third parameter is the context in which to evaluate the next path element (for example traversing the "pids" directory results in the context being 'all_pids', and the element after that is {pid, Pid}, enabling, for example, a read-directory event, if it is invoked at that point, to enumerate all objects that are inside a PID.

See 'Exfuse.Fs.Example' for a simpler example of a filesystem, or the simple hello-world Exfuse.Fs.Hello.