Well, actually magic(5) is used by the file(1) command to identify a file. So when you type `file foo.jar`, it can tell you "hey, this is a jar file". This is

Well, actually magic(5) is used by the file(1) command to identify a file. So when you type `file foo.jar`, it can tell you "hey, this is a jar file". This isn't something that other applications do, and exec and friends do not look at it to try to determine what kind of file something is or how to execute it. #! is special - and not because of magic(5) - if a file starts with `#!`, exec and friends will treat it special. Anything else will be attempted to be executed as a binary. Now, one _could_ go and install binfmt_misc and set it up so that files with a jar's magic number will be executed a certain way (`java -jar ...`), but this is neither out of the box nor something that all Unix derivatives do. Notably, binfmt_misc will also work with extensions instead of magic numbers.