UNIX is both the underlying code and architecture that makes up Mac OS X / iOS as well as a way of interacting with a Mac using the terminal app, X11 app, and various shells like `bash` or `zsh`. Whether you're logging into a mac using `ssh`, using `mdfind` or `tmutil` or using other open source software, you are doing things very much in common with other UNIX operating systems and toolsets such as Linux, GNU, and many, many others too numerous to list.

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