Upgrade BASH using Brew on Mountain Lion

gistfile1.sh

brew update
brew install bash

# Add this install of bash to the allowed shells list:
sudo bash -c "echo /usr/local/bin/bash >> /private/etc/shells"

# Homebrew installs things to /usr/local/Cellar/, then symlinks any binaries to /usr/local/bin, so you've now got the latest bash sitting at /usr/local/bin/bash

chsh -s /usr/local/bin/bash

# Checks
echo $SHELL #/usr/local/bin/bash
echo $BASH_VERSION # 4.2.45(2)-release