APT shortcuts

#!/bin/bash
this=$(basename "$0")
there=$(dirname "$0")

idle='nice -n +40 chrt -i 0 ionice -c 3'
dir_cache=/var/cache/apt/archives
dir_lists=/var/lib/apt/lists
f_storage=/opt/apt.lists.tar.xz
compress='xz -C none -v'
ratio=1
N00B=1

__install()   { for i in ${shortcuts}; do ln -vfs ${N00B:+-i} "${this}" "${there}/$i"; done; }
__uninstall() { for i in ${shortcuts}; do rm -vf  ${N00B:+-i} "${there}/$i"; done; }

shortcuts='a-u a-s a-r a-p'

__help() { cat >&2 <<-EOF
usage:
  ${this} {cmd} [args]
    {a-u|u|update}
    {a-s|s|save}
    {a-r|r|restore}
    {a-p|p|purge}

    {install}
    {uninstall}
EOF
exit 1; }
__try_file()  { local d=$(dirname "$1"); test \( -f "$1" -a -w "$1" \) -o \( ! -e "$1" -a -w "$d" \) ; }
__try_dir()   { test -d "$1" -a -w "$1"; }
__test_file() { test -f "$1" -a -r "$1"; }
__action() {
    case "$1" in
    a-u|u|update)
        exec ${idle} apt-get update
    ;;
    a-s|s|save)
        __try_file "${f_storage}" || exit 1
        du -hd0 "${dir_lists}"
        tar cPf - "${dir_lists}" | ${idle} ${compress} -${ratio} > "${f_storage}"
    ;;
    a-r|r|restore)
        __test_file "${f_storage}" || exit 1
        ls -lh "${f_storage}"
        ${idle} ${compress} -d < "${f_storage}" | tar xPf -
    ;;
    a-p|p|purge)
        __try_dir "${dir_lists}" || exit 1
        __try_dir "${dir_cache}" || exit 1
        find "${dir_lists}" "${dir_cache}" -mindepth 1 -delete
    ;;
    install)      __install ;;
    uninstall)    __uninstall ;;
    *)            __help ;;
    esac
}

case "${this}" in
apt.cmd)  [ $# -eq 0 ] && __help; __action "$@" ;;
*)        __action "${this}" "$@" ;;
esac