[RetroTechie]

Useful enough that it should be an OS-level standard feature, imho.

Unix-like OSes allow mounting disk images to explore their contents. But there's many more file formats where exploring files-inside-files is useful. Compressed archives, for one. Some file managers support those, but (imho) application-level is not the optimal layer to put this functionality.

Could be implemented with a kind of driver-per-filetype.

[duped]

Really what you'd like to see is a way to write the mount command for each file type (do one thing well) and another command to detect the file type and dispatch accordingly (probably similar to the `file` command), all in user space.

The only thing standing in the way of this today is that MacOS doesn't expose a user space file system API. You can do this on Linux, Windows, and BSDs today.

(No, file provider extensions don't cut it, Apple devs who read this, please give us a FUSE equivalent, we know it exists).

[stuaxo]

I want stuff to work like ZipMagic did in the early 90s/ early 2000s.

You could cd into zip files, they would act as directories and files at the same time.

I seem to remember Linus saying a file could act like a directory in Linux a long time ago too.

Though I don't think Linux has filters for the filesystem like Windows does so implementation might be more tricky.

[Groxx]

Does https://osxfuse.github.io/ cover this? Or is there some fundamental issue? (beyond "it's not built in")

[skissane]

Recent macOS versions do have a general purpose built-in API for user mode filesystems. That API is incompatible with FUSE. The big problem is it is undocumented and you need an entitlement from Apple to use it, and Apple won’t give you that.

Apple do have a publicly available API for cloud file systems (Dropbox-style products), but it makes a lot of assumptions which makes it effectively unusable for other use cases.

Then there are third party solutions like osxfuse. These have the problem that they rely on kernel extensions and Apple keeps on making those harder and harder, and is aiming to get rid of them; plus, they are all now proprietary licensed, albeit often with a free license for open source use.

One approach that does work without any kernel extensions or private APIs is to make your user filesystem an NFS server and then mount that. One competitor to osxfuse does that, but it also is proprietary

[ranger_danger]

According to the MacFUSE author, their specific approach is not actually undocumented:

> Apple has put it in an umbrella called "unsupported" (in the kernel interfaces section) ... either Apple will not take this interface away, and if they do, it will be to provide a better interface

http://preserve.mactech.com/articles/mactech/Vol.23/23.03/Ma...

[skissane]

Yes, that’s not what I’m talking about though

MacFUSE uses the kernel mode VFS API

I’m talking about the undocumented user mode filesystem LiveFS/UserFS/com.apple.filesystems.lifs API which was added in Monterey (macOS 12), and since Ventura (macOS 13) is used to implement the OOTB FAT and exFAT filesystem support. Using that requires private entitlements (e.g. com.apple.private.LiveFS.connection) which Apple (thus far) won’t give to anyone else

[ranger_danger]

What about the File Provider API?

[w10-1]

> it makes a lot of assumptions which makes it effectively unusable for other use cases

What use-cases are foreclosed and why?

[duped]

Well that requires a kext so it's a nonstarter, and fuse-t uses NFS which is extremely janky and unreliable on MacOS.

The fundamental issue is that macOS doesn't provide an API for this natively.

[skissane]

> fuse-t uses NFS which is extremely janky and unreliable on MacOS

I was wondering what issues you were talking about, and then I found this - https://github.com/macos-fuse-t/fuse-t/issues/45 - data corruption

> The fundamental issue is that macOS doesn't provide an API for this natively.

The API is there, Apple just doesn’t want to give anyone outside of Apple the entitlement that lets them use it. I don’t understand why Apple won’t.

Well, I understand that would require them to document it, ship public headers, and support it for external developers - but why not?

[duped]

> The API is there, Apple just doesn’t want to give anyone outside of Apple the entitlement that lets them use it.

If no one can call it it's not an API, it's an implementation detail. And I don't even think its exposed by headers, just alluded to by people who claim APFS is implemented in user space.

> I was wondering what issues you were talking about, and then I found this

Worse than this, it's possible to DoS a Mac with an NFS server just by refusing to reply to a request. That's unacceptable for a user space file system (although FUSE is only kinda better, in that it can force processes that read from the FS into uninterruptable sleep that prevents them from being killed).

> Well, I understand that would require them to document it, ship public headers, and support it for external developers - but why not?

Because Apple doesn't give a fuck about developers. Every developer will eventually learn this, but for those that haven't - Apple doesn't want you writing software for their platform, unless you're an Apple employee and on an Apple team paid to do it. It's why their docs suck, it's why to learn anything you need to watch ADC videos instead of read manpages, and it's why all the cool stuff is behind protected entitlements that you can't get or will be limited in using.

[mike_hearn]

No, it's almost certainly not because they don't give a fuck about developers. They definitely do.

It's much more likely that they want to:

a. Dogfood the API using internal use cases first when they can still make changes to the API without breaking anything. Note that the latest MacOS releases moved some filesystems into userspace using this new API. They probably learned some stuff by doing that.

b. Work out how to protect system stability from crappy userland filesystems. As you point out, bugs in FUSE providers can hang apps.

c. Work out how such an API interacts with their sandboxing system and how to avoid FUSE-style filesystems being used to subvert the sandbox. This is a common source of exploits in FUSE-style systems and is one of the key learnings from GNU/Hurd: UNIX software is written on the assumption that filing systems aren't malicious and invalidating that assumption creates new bug classes.

d. Work out what the most important use cases are and try to ensure those use cases will have a good or at least uniform UX first.

Providing a FUSE-like API is presumably also just not a high priority. By far the most common use case in terms of number of users is the Dropbox use case. FUSE is mostly used for toys and experiments beyond that (like filefs). Those matter and I'm sure there are friendly geeks on the Darwin team who'd like to enable those, but Linux also works for exploration. Certainly Apple management would not be happy about an engineer who decided to enable nerd experimentation but undermined the security system whilst doing so.

And it's worth remembering that you can have root on macOS. It means disabling SIP and adding a kernel boot arg, but that only takes a few minutes and then you can grant apps any entitlements you like:

https://github.com/osy/AMFIExemption

That's no good for people who aren't developers, but most FUSE filesystems are designed for developers anyway.

[skissane]

> Worse than this, it's possible to DoS a Mac with an NFS server just by refusing to reply to a request.

I wonder if their SMB/CIFS client implementation has these kinds of issues? It probably gets used more heavily

> And I don't even think its exposed by headers

Apple (accidentally?) released some of the private headers for this feature in one of their open source releases: https://github.com/apple-oss-distributions/msdosfs/blob/rel/...

[nine_k]

> why don't they

It would make macOS more of a general-purpose OS, would increase the amount of functionality from which third parties would benefit, but Apple themselves would likely not. That would increase the number and variety of tech support requests, ever so slightly but still, and would introduce a few new attack surfaces.

Instead, Apple's strategy is to tighten the macOS more and more, and turn it into a specialist OS completely controlled by Apple, with a few companies like Adobe and Ableton licensing access to its internals.

[samatman]

I've been using OSX since 2003, and developing on it for more than ten years. At no point have I seen anything that it's reasonable to call "tightening macOS", let alone the absurd claim of complete control except for an inner circle of elite companies.

The closest thing would be adding the attestation system, so that unsigned binaries have to be explicitly given permission to run... once. That's a security feature which trades a bit of convenience for a lot of protection, especially for the average user. I have no problem with that sort of thing.

I see this sort of sentiment very frequently from non-users of the operating system, but never from those of us who actually use it. Go figure.

[skissane]

Apple used to be a lot more developer-friendly company. It is part of what got them where they are now - the fact that so many developers use Macs, which in turn encourages business software vendors to support Macs

Stuff like this is of little interest to ordinary users (at least not directly), but appeals to developers

By de-emphasising the developer is experience, they are undermining one of the factors that got them to where they are today

[Sophira]

This already exists - avfs[0] does this as a FUSE filesystem. It's not the most intuitive to use, but it works, and is extensible.

[0] https://avf.sourceforge.net/

[lmm]

This was a core design feature of reiserfsv4, but Linux ultimately refused to merge it, probably not helped by the whole murdering-his-wife thing.

[skissane]

> This was a core design feature of reiserfsv4, but Linux ultimately refused to merge it

IIRC, because it contained these strange beasts which functioned as both files and directories - i.e. cat would return data, but then you could cd into them and run ls. Linus (among others) didn’t want to permit those violations of the file-directory dichotomy into the Linux kernel.

[stuaxo]

Oh that's funny- I remember a much much earlier Linus mentioning how this would he possible in Linux, I didn't know anyone actually did it.

I think you really should be able to "cd" into any kind of structured data.

[frizlab]

Honest question: How is this useful? I don’t see any use-case where this would come in handy.

[RetroTechie]

It allows you to use any tool available for regular files, on the files-in-files as well.

As opposed to extract contents and then work on that (requiring extra steps + disk space). Or be limited to what specialized utilities support.

[crabbone]

We used this in Gitlab CI. Unfortunately, the only way they deal with artifacts is by putting them in Zip files. Cache between builds would thus be stored as a Zip file. However, fully extracting it before each build would sometimes take as much, if not more time than to just build fresh. Mounting a Zip file as a filesystem allows extracting entries on-demand, at the time a file access would've been made. This was a notable speedup in our compilation process.

[pizzafeelsright]

tar is what you're looking for, no?

[crabbone]

It was a while ago, and I haven't used Gitlab in a few years. Maybe they've added TAR as an option since, but Zip was the only option at that time.

[w10-1]

It reduces the code required to convert from N-producers to M-consumer from N x M to N+M because they're reading from and to a well-understood common form.

[TimeBearingDown]

You could seed compressed archives of massive text files or similar via BitTorrent while making the contents available to your apps in read-only mode.

[russfink]

Exporting data to some format would be easy.

[crabbone]

I thought archivemount already did that. Am I missing something?

Anyway, even if that's not what you are looking for, FUSE is a more general mechanism that will allow you to do what you want (well, it seems like, at least) and much more.

[jraph]

It exists :-)

For zip archives, there are fuse-zip and mount-zip which are FUSE filesystem.

As an intermediate between OS level and application-level, there are desktop environment level: gvfs for GNOME and KIO for KDE, but they are compatible only in their own ecosystems.

[lambdaxyzw]

Would be nice to have something that integrates with 7z - it supports a lot of weird archive types, including "weird" ones I care about (for example PE files, better known as ".exe files").

[russfink]

Or zstd. I have some dd blobs of partitions, the blobs are zstandard-compressed, would like to mount them.

[mxmlnkn]

Ratarmount also works for that. However, it, and any other tool I know of, works only well if it was compressed with pzstd because of a limitation of the zstd format. It needs separate zstd frames for fast seeking.

[ramses0]

ratarmount for tar files.

[xk3]

> Compressed archives, for one

You can look inside of archives pretty easily with `lsar` (part of the unar package). It works with disk images like ISO 9660 files too

But yes, especially for nested archives, having deeper OS support would be nice.

[kybernetikos]

It's not exactly the same, but nushell provides ways of exploring inside files.