A bit of a wow for me was when I learned about exit statuses: 0 is success, everything else is error because there is only one way that a command can do what yo

A bit of a wow for me was when I learned about exit statuses: 0 is success, everything else is error because there is only one way that a command can do what you want and hundreds of ways it can fail. It might seems obvious, but that seriously taught me something.