fs_usage(1) on macOS

The text b7183e42ddd8, as Mac OS X 10.1.5, Mac OS X 10.1.4, Mac OS X 10.1.3, Mac OS X 10.1.2, Mac OS X 10.1.1, Mac OS X 10.1 shipped it.

reports system calls and page faults related to filesystem activity in real-time.

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