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https://github.com/vkazanov/elfuse

FUSE filesystems in Emacs Lisp
https://github.com/vkazanov/elfuse

c elisp emacs fuse libfuse

Last synced: 11 days ago
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FUSE filesystems in Emacs Lisp

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README 

        
* Elfuse



  Elfuse is a little experiment in implementing a dynamic Emacs module. The idea is to expose *some*

  of the libfuse possibilities to Emacs Lisp code.



  In other words, it should now be possible to implement file systems in Emacs lisp!



* Compile



  Because Elfuse is a dynamic module, Emacs compiled with dynamic module support is required.

  Currently (Emacs 25.1) this requires supplying a special flag at configure time (=--with-modules=).



  Additionally, Elfuse was developed and tested on Linux only (Ubuntu 16.04) using libfuse 2.9.4, no

  guaranties on other platforms or libfuse versions.



  Compilation should be trivial on Linux with a recent GCC:



#+BEGIN_SRC

  > cd elfuse/directory/

  > make

#+END_SRC



* Running Examples



  To run one of the Elfuse examples in the =examples= directory using a config-less separated Emacs

  instance do something like the following:



#+BEGIN_SRC

  > cd elfuse/directory/

  > mkdir mount

  > make hello.el

  > # an emacs window will open

  > # do M-x elfuse-start "mount/" to mount an Elfuse instance to the mount/ path

  > ls mount/ # a few fake files should appear here

  > # do M-x elfuse-stop to unmount Elfuse

#+END_SRC



  This will start Emacs with Elfuse loaded and load an example Elfuse project. In fact, this is *the*

  recommended way to run Elfuse instances (i.e., =emacs -Q --load elfuse.el=).



  Notice that =elfuse-start= / =elfuse-stop= functions are main user-visible entry points.



  Examples included:



  - =hello.el= - a static list of files with dummy content



  - =hello-2.el= - a dynamic list of files, i.e. it's possible to create a file in the mount path



  - =list-buffers.el= - expose a list of emacs buffers as a list of files. Only buffers having names

    compatible with POSIX portable filename definition will be listed. Buffer content will also be

    mirrored. Is is possible to create an Emacs buffer using =touch=.



  - =write-buffer.el= - edit an emacs buffer (=*Elfuse buffer*=) from the terminal.



* Additional Notes



  Elfuse currently doesn't have much documentation apart from the source code and =examples/*.el=. To

  play with the library the user will have to consult the examples.



  Also, it is strictly *not* recommended to try to list the mounted Elfuse directory using the same

  Emacs instance that runs Elfuse. This will definitely block Emacs.



  Elfuse runs a libfuse loop using a dedicated (Pthread) thread. When syscalls arrive the thread

  signals (sends a SIGUSR1 signal) the main Emacs thread and blocks until the main thread finds time

  to respond to the request.



  Elfuse currently does not support mounting multiple FUSE paths. Actually, it uses a single set of predefined

  callback names (i.e. =elfuse--readir-op=).



  In case things go wrong =fusermount -u path/to/a/mount= should help.



  In case things go HORRIBLY wrong =umount -f path/to/a/mount/= should do the trick.



* Background



  Some time ago I wrote [[https://github.com/vkazanov/toy-orgfuse][quick Python script]] that allows to mount org-mode files as FUSE filesystems.

  The obvious problem with the script was that it needed a custom Org-mode file parser, which would

  always lag behind the mainstream Org-mode and would miss important features. I was wondering if

  using the native parser was possible.



  As some point [[http://nullprogram.com/][Chris Wellons]] jumped in and mentioned that it might be possible to implement a

  dynamic Emacs module doing just that: Emacs Lisp bindings to FUSE. Which I did! Later on Chris

  came up with a [[http://nullprogram.com/blog/2017/02/14/][blog post]] about the way Elfuse works. Elfuse uses a few interesting tricks so if

  you're interested in details - just follow the link.