What's the equivalent to ${var:-defaultvalue} in fish?

Question

Hello I am trying to translate my .bashrc to fish format almost done, mostly is clear on the documentation but this part is giving me a headache.. is so my gnupg works with

Answer 1

I had a similar question, related to XDG_* variables.

var1="${XDG_CACHE_HOME:-$HOME/.cache}"/foo
var2="${XDG_CONFIG_HOME:-$HOME/.config}"/foo
var3="${XDG_DATA_HOME:-$HOME/.local/share}"/foo
some-command "$var1" "$var2" ...

What I found as the best alternative is to simply set univeral variables once for the defaults--

set -U XDG_CACHE_HOME ~/.cache
set -U XDG_CONFIG_HOME ~/.config
set -U XDG_DATA_HOME ~/.local/share

Then in fish config file(s) or scripts, simply use "$XDG_CONFIG_HOME"/.... The value of an exported environment variable will override the universal variable if set, otherwise the universal variable is there as a default/fallback. If the universal variable is used, it is not exported to child processes, while an exported environment variable is, which provides the full equivalent to bash|zsh parameter expansion.