Following the instructions from this post on how to update cabal-install, I seemed to be able to install the latest version (or at least some version > 1.18, which is what I wanted.
$ cabal install Cabal cabal-install
Resolving dependencies...
Configuring cabal-install-1.22.6.0...
Building cabal-install-1.22.6.0...
Preprocessing executable 'cabal' for cabal-install-1.22.6.0...
<snip>
Linking dist/build/cabal/cabal ...
Installing executable(s) in /home/kavi/.cabal/bin
Installed cabal-install-1.22.6.0
However, when I tried cabal sandbox, it failed, so I checked cabal --version.
$ cabal --version
cabal-install version 1.16.0.2
using version 1.16.0 of the Cabal library
As you can see, the version is not the one that cabal claimed to install.
Adding ~/.cabal/bin to my path did nothing to help. (Yes, I did restart my terminal).
$ echo $PATH
<snip>:/home/kavi/.cabal/bin
$ cabal --version
cabal-install version 1.16.0.2
using version 1.16.0 of the Cabal library
I tried restarting my computer, but still:
$ cabal --version
cabal-install version 1.16.0.2
using version 1.16.0 of the Cabal library
I am using Ubuntu 14.04.
You should add /home/kavi/.cabal/bin to the beginning of the $PATH.
which cabal tells which executable shell will pick to execute, on my machine:
% echo $PATH
/Users/ogre/.local/bin:...
% which cabal
/Users/ogre/.local/bin/cabal