file utility

[grylem]

-m and -M options don't work

file -m jbig2.magic test.jb2
test:.jb2 : data

Expected output:
file -m jbig2.magic test.jb2
test.jb2: JBIG2 image data

[jgarzik]

file is a challenge, and I am not sure what is the best solution.

Linux and macOS both have different, OS specific binary magic file formats. macOS's is undocumented, I believe.

We could ship our own full magic database, but that adds an unwanted maintenance burden, a database constantly hungry for updates. Other options (parsing OS binary C structures) are ugly. :)

[grylem]

I used plain-text magic file.
macOS used patched for posix compliance version
ftp://ftp.astron.com/pub/file/file-5.41.tar.gz
See the file file.plist from
https://github.com/apple-oss-distributions/file/tree/file-104