[citrin_ru]

> So much user-facing network software is built on top of other programs, like ssh or rsync, and when those things fail they just don't know what to do. And so much of the problem is precisely because they're not using them as libraries, they're using them as command-line utilities.

Unix CLI utilities have well defined way to return an error - non zero exit code. It is even possible to return different errors as different exit codes, though it is rarely done.