Pseudo filesystems on *nix

Question

I need some opinions pointers on creating pseudo-filesystems for linux/*nix systems.

Firstly when I say pseudo-filesystem I mean something like /proc where the structure within does not represent actual files on disks or such but the state of the kernel. I would like to try something similar as an interface to an application.

As an example you could say, mount a ftp url to your filesystem and your browser app could then allow you to interact with the remote system doing ls et al on it and translating the standard filesystem requests into ftp ones.

So the first question is: how does one go about doing that? I have read a bit about it and it looks like you need to implement a new kernel module. If possible I would like to avoid that - my thinking being that someone may have already provided a tool for doing this sort of thing and provided the module to assist already.

My second question is: does anyone have a good list of examples of applications/services/whatever using this sort of technique to provide a filesystem based interface.

Lastly if anyone has any opinions on why this might be a good/bad idea to do such a thing on a generic level I would like to hear it.

Answer 1

A userspace filesystem via fuse would probably be your best way to go.

Answer 2

Regarding the next part of your question (which applications use this method), there is the window manager wmii, it uses the 9p filesystem via v9fs, which is a port of 9p to Linux. There are many examples on plan9, most notably acme. I suggested fuse because it seems more actively developed and mainstream in the Linux world, but plan9 is pretty much the reference for this approach as far as I know.