$ pijul doff
Error: No such file or directory (os error 2)

This error message is not very helpful. If the user doesn’t read the command again and notices the typo, the message is extremely confusing.

@pmeunier a side note: you can just use eprintln! instead of writeln!(stderr()).

(Unless the point is to prevent panics when stderr can’t be written…)

Nope, that panics when piped to head.