It's not possible to be perfect, but you can certainly do better than taking down S3 because of a single command gone wrong. One thing I have been doing for my

It's not possible to be perfect, but you can certainly do better than taking down S3 because of a single command gone wrong. One thing I have been doing for my own command line tools is making a preview feature for what a command will do and make the preview state be default. It's simple, but if the S3 engineer first saw a readout of the huge list of servers that were going to be taken offline instead of the small expected list we probably would not be talking about this. There's obviously a ton more you can do here (have the tool throw up "are you sure" messages for unusual inputs, etc).