Like when you send a .7z instead of a .zip or .rar to a friend or a teacher because that's what your computer has installed and they're like "Oh No, not one of those, now I have to install 7Zip" even though the same program that opens .rar also opens .7z I feel like people are way more annoyed when they receive a .7z
Are there any examples of multiple file extensions outside of compression and archiving?
Sexylady.jpg.exe
Hmmm... nothing comes to mind, only tar.
It's common when you "wrap" one file type inside another. Like .tar combines multiple files into one, then .gz compresses a single file.
You also see it with PGP (encryption).
Suppose I have a javascript file for a node server's backend access named
db.js
Suppose I write tests for those functions and name the test script file
db.test.js
Suppose I tar and gzip that file (bear with me), now named
db.test.js.tar.gz
Suppose I sign that file with PGP, now named
db.test.js.tar.gz.pgp
Now suppose I want to hide that signed compressed tarball of a javascript tests file for my db functions, and to do so, I name it
.db.test.js.tar.gz.pgp
Now I have a file that looks like it consists of nothing but extensions. I'm sure you could push it even further though, if you tried.