A shell-script based Automatic homebrew package manager updater for zsh

.update-homebrew.zsh

brew_update_version=$(date +"%Y%m%d")
brew_update_version_file="$HOME/.homebrew-lastupdate"
brew_update_in_progress_file="$HOME/.homebrew-update-in-progress"

brew_upgrade_required=0
test -f "$brew_update_version_file" || brew_upgrade_required=1

if [[ $brew_upgrade_required -eq 0 ]]; then
    this_brew_version=$(cat "$brew_update_version_file")
    test "$this_brew_version" = "$brew_update_version" || brew_upgrade_required=1

    if [ -f "$brew_update_in_progress_file" ]; then
	test "$this_brew_version" = "$brew_update_version" && brew_upgrade_required=0
    fi
fi

if [[ $brew_upgrade_required -eq 1 ]]; then
    echo -n "[Homebrew] Would you like to update? [Y/n] "
    read -r -k 1 option
    [[ "$option" != $'\n' ]] && echo
    case "$option" in
      [yY$'\n']) brew_upgrade_required=1 ;;
      [nN]) brew_upgrade_required=0 ;;
    esac

    if [[ $brew_upgrade_required -eq 0 ]]; then
	echo -n "[Homebrew] Do you want to skip update today? [y/N] "
        read -r -k 1 option
        [[ "$option" != $'\n' ]] && echo
        case "$option" in
            [nN$'\n']) brew_skip_update=1 ;;
            [yY]) brew_skip_update=0 ;;
        esac
    fi

    if [[ $brew_skip_update -eq 1 ]]; then
	echo -n "[Homebrew] All right! I will not ask you to update for today."
	echo -n $brew_update_version > $brew_update_version_file
    fi
fi

if [[ $brew_upgrade_required -eq 1 ]]; then
    echo "[Homebrew] Updating Homebrew..."
    echo -n $brew_update_version > $brew_update_in_progress_file
    brew update
    brew upgrade
    brew cleanup
    brew doctor
    echo -n $brew_update_version > $brew_update_version_file
    rm -f $brew_update_in_progress_file
    echo
fi