Send a notification when a long-running command finishes.

postexec.fish

# I have this inside my .config/fish/config.fish, but you migh be able to put it in .config/fish/functions ?
function show_notif --on-event fish_postexec
    set -l duration $CMD_DURATION
    set -l command $argv
    if [ $duration -gt 10000 ]
        set -l is_front (osascript -e 'tell application "Terminal" to frontmost')
        if [ $is_front != "true" ]
            osascript -e "display notification \"Command `$command` finished running after "(expr $duration / 1000)"s\" with title \"Command finished\""
        end
    end
end