kaitai_struct_formats VS file

Kaitai has a repository of binary formats[1] that can be used in visualizers or to auto-generate parsers.

[1] https://formats.kaitai.io/

This is tangential to your submission, but PDF is the file format I use for exercising any library that claims to be a declarative file format (ala https://github.com/kaitai-io/kaitai_struct_formats#readme )

https://www.darwinsys.com/file/

This is the authors website. Apparently yeah its not part of GNU utils, I had no idea, I knew it came with most Linux systems so I looked for the Debian package and found the site linked above.

https://packages.debian.org/bookworm/file

https://github.com/file/file/blob/master/magic/Magdir/gentoo https://www.iana.org/assignments/media-types/application/vnd.gentoo.ebuild (among others)

Look into libmagic.

in installations of Linux, file is a command to retrieve some basic information about a file type. Because contrasting to the organization of Windows, the file extension in Linux can be less important for the file's use (even irrelevant), than the actual content.

In this case, it's hitting this set of rules. I would guess it hits both class and public.

But I don't think this is what you meant. I think your question is something more like: how many file formats are there? The Unix file command recognizes several thousand, and Wikipedia has a list. Of course these are only the most common, and it's hard to delineate what counts as a unique file format. (Is YAML one file format or millions?)

The magic number for all ogg files is the same (OggS) and files magic file looks like it decides the mime type based on the codecs used in the file. However, it looks like application/ogg is used only if the file contains Kate (Karaoke and Text) content.

Also the magic number database for guessing the format of a file:

https://www.darwinsys.com/file/