Using RVM with Fish Shell in just 6 lines of code

rvm.fish

# ~/.config/fish/functions/rvm.fish

function rvm --description "Ruby Version Manager"
  exec bash --login -c "rvm $argv; exec fish" ^&1
end

rvm_config.fish

# ~/.config/fish/config.fish

# Loads the default ruby and appends stderr to stdout
if test -z $rvm_bin_path
  exec bash --login -c "exec fish" ^&1
end