function 7zz() {
    # compress a direcotry to directory.7z
    # usage: 7zz path/to/directory [7z options]
    # returns: 0 - successful, 1 - argument error, 2 - not found 7z command
    local ok=$(command -v 7z >/dev/null 2>/dev/null && echo 'ok' || echo '')
    if [ "$ok" != "ok" ]; then
        echo 'not found 7z command, please install p7zip'
        return 2
    fi

    local dir="$1"
    local target="$(basename ${dir%/}.7z)"
    if [ ! -d "$dir" ]; then
        echo 'argument error\nusage: 7zz path/to/directory [7z options]'
        return 1
    fi
    if [ -f "$target" ]; then
        while true; do
            printf "Are you sure overwrite file \"$target\"? [y/N] "
            read yn
            case $yn in
            [yY][eE][sS] | [yY]) break ;;
            [nN][oO] | [nN] | "") return 0 ;;
            *) ;;
            esac
        done
        rm -f "$target"
    fi

    shift
    7z a -mx=9 -xr\!.DS_Store "$@" "$target" "$dir"
}