Show HN: Bashfs – Run commands as your filesystem

[jasonhansel]

I worked on a semi-similar project, to let people turn bash scripts into FUSE filesystems: https://github.com/jasonhansel/microfs

For example, this script is used to make a FS that turns the web into a filesystem, so reading /www.google.com/GET will show the Google homepage: https://github.com/jasonhansel/microfs/blob/master/http.sh

[threeme3]

microfs looks interesting to me, but unfortunately crashes with a SEGFAULT on Ubuntu 19.04:

Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7de88b8 in __GI__IO_fread (buf=buf@entry=0x7fffffffd4f0, size=size@entry=1, count=count@entry=1024, fp=0x0) at iofread.c:35

[Hnrobert42]

No, but really, why? I am not putting it down. I just don’t understand what is happening exactly, and the why might help.

[iguessthislldo]

The actual "why" is the author did it for fun, there's basically no purpose to it. I can try to explain it though:

Interacting with file systems can be generally summed up in a handful of basic operations. Two of the most important operations are open, which asks the filesystem if it has a file of a given name, and read, which reads the contents of that file. FUSE is a Linux wrapper for writing virtual file systems by implementing these basic operations. Here open, instead of taking a filename, is telling the program what command to run and read, instead of returning the contents of a file is returning the output of the command.

[ansible]

I'm glad I'm not the only one who didn't get it.

I can understand if you want to do something wacky with FUSE. Something like mounting a PostScript or JSON file, and using the filesystem interface to observe and modify the contents. Or something else that is vaguely hierarchical.

I just didn't see any "reasonable" mapping for running a series of commands to a filesystem.

[PopeDotNinja]

They address this in the README.

https://github.com/pcgrosen/bashfs#why

[bdarnell]

It's mainly for fun, but to find cases where it might be useful, think about symlinks into this filesystem. `ln -s /bashfs/somescript.sh /etc/hosts` and then your hosts file can be dynamically generated without any changes to programs that read it. It can be a clever way to sneak dynamic behavior into contexts where there would normally just be a static file.

[BlackLotus89]

Quote from the Readme:

> Why not?

[xfitm3]

I get that it's for fun but the danger is security. Someone could use this as a "fun" feature at work and then get pwned.

[pcr910303]

There's a lot of 'Why?'s here, what I feel from this is that the FS can now be a turing-complete system. This will allow to extend the 'Everything is a file' concept in UNIX (whether it's good or bad is a different question;) to computation.

With BashFS, computation & interaction with other programs is now a file; we can 'open' a appropriate file instead of managing subprocesses anymore!

This (at least to me) blur the difference between UNIX (where everything should be a file) and LispMachines (where everything is a Lisp object).

[TazeTSchnitzel]

Check out Plan 9.

[YesThatTom2]

Go home, coder. You’re drunk!

[high_5]

Why not? :-D

[ORioN63]

Is there something like FUSE for a single file?

My use case is for pass. I like to keep my secret files in there, but I still have plain text redudancy, because, well, encrypted files are useless while encrypted.

I would like to have a "virtual file" which any program could accept as its config file where I could control the results of `read()`

In my case, I would associate the current file to its pass equivalent, decrypt the pass equivalent and return the decrypted data.

[dallbee]

Sure, fuse actually implements the lesser known CUSE protocol as well. Stands for character device in user space, and does exactly what you describe.

[callesgg]

That is exactly how fuse operates.

[agucova]

We've come so far as a society, it's amazing.

[rambojazz]

Is there any way this can be useful for something? Or is it just a fun experiment with FUSE?

[jarfil]

Possibly the most useful part might be the patch to upstream pyfuse3 proposed by the author, and as a reference implementation for something similar that might be useful on itself.

[xg15]

So what happens if I do ls mnt or find mnt?

Also, this looks like the perfect thing to mount to a /htdocs directory or nfs-accessible folder :)

[kristopolous]

There may be a clever way to subvert scponly and the nologin related commands with this.

Still piecing it together but maybe

[riquito]

Visionary, it was fun to see

[asimjalis]

Beautiful.

[tfowler]

Don't see much difference than something like

$ cat <(my_favorite_script)