my xonsh prompt translated to zshrc / bashrc

zshrc

function short_dir {
    # zsh for the default
    local DIR="%%~"
    if [[ "$0" == *"bash"* ]]; then
        DIR="\w"
    fi
    printf "$DIR"
}

function os_icon {
    local ICON=""
    if grep Ubuntu /etc/lsb-release &>/dev/null; then
        ICON=""
    elif [[ "$(uname -a)" == *"Darwin"* ]]; then
        ICON=""
    fi
    printf "$ICON"
}

function update_ps1 {
    export PS1=$'\n'"┌─ $USER $(os_icon) $(hostname -s) $(short_dir) "$'\n'"└─ "
}

# for bash
export PROMPT_COMMAND="update_ps1"

# for zsh
function precmd() {
    eval "$PROMPT_COMMAND"
}