Function run 

pub fn run()

Parses the command line, dispatches, and exits non-zero on failure.

This is the whole body of the atune binary. On the error path it prints atune: <error> to standard error and exits the process with the error’s own code — 2 for a usage mistake, 1 for anything else — so it does not return. Argument parsing is clap’s, which exits with its own message and its own code on a malformed invocation.