apt-get is a kind of "frontend" for
dpkg which is in an ultimate instance, who do all operations. You can easily recover your
apt-get if you download the package from the repository and install it yourself:
(this is a illustrative example, I'm using the latest version of apt i386 from precise-updates repository, you should download the one that fits you, for a complete list of versions check: Ubuntu apt package list or Launchpad apt package list. You should check your installed version using
apt-cache policy apt)
wget http://mirrors.us.kernel.org/ubuntu/pool/main/a/apt/apt_0.8.16~exp12ubuntu10.12_i386.deb http://mirrors.us.kernel.org/ubuntu/pool/main/a/apt/apt-transport-https_0.8.16%7Eexp12ubuntu10.12_i386.deb
sudo dpkg --unpack apt_0.8.16~exp12ubuntu10.12_i386.deb apt-transport-https_0.8.16%7Eexp12ubuntu10.12_i386.deb
sudo dpkg --configure -a
sudo apt-get update
Now you have your apt-get working again.
Why not use
--install instead of separated
--install switch executes tasks that are not necessary (
postrm) for recovering apt binaries, and might run into problems later due the sorry state of the installation. For such reason,
--unpack to get the binaries set in place and
--configure to restore any lost configuration file are just necessary.