[1letterunixname]

A few notes:

- It should be generating `path: impl AsRef<Path>` to be properly generic.

- It's not setting a nonzero exit code on error.

- Edge case handling is a vital property for production-usable tools at scale. I'm wondering if it can yet special case situations such as creating a conditional compilation version for Linux that uses the splice syscall when the arguments are 2 file handles.