!! is not specific to fish. It is a history feature to get the last command. It's like using '!ec' for getting the last command that starts with 'ec'. Using `!!` is not "getting output of previous command", it is re-executing it and getting that output.
You haven't told me how to do a `!!` in fish. (I do understand that it re-executes the previous command). I am used to using this in other shells like bash and zsh, and would like to know if there's some way of doing it in fish.
AFAIK this is not possible with fish, as variables cannot be used as commands like in bash (and the ! history feature does not exist in fish, it is designed to be fully interactive).
1. I use the Alt-. (dot) to get last argument of previous command.
2. Getting output of previous command such as : `!!` (backtick !! backtick) for which I get a "no such file".
I asked on reddit, but got no replies. Thx.