How can you tell whether an app on your Mac is a Universal App, or only support Intel processors?
file
You’re checking through old files. How can you tell which file type they are when you don’t recognise the extension, or they don’t even have that to help?
Getting strange errors when trying to copy an RTFD package? Try looking inside it, to see if it has developed recursive structure, like Russian dolls.
Telling what a file is – whether plain text, Unicode UTF-8, 32-bit code, and so on – can be hard. Just use a little magic, free in the command tool ‘file’. Includes Swift code to access magic numbers.
The Eclectic Light Company 