OS X ships with an outdated version of Bash as its default shell. The preinstalled version dates back to 2007, yes - nearly a decade behind. If you want to use an updated version of Bash and Bash Completions in your shell, you can install them by using Homebrew, a package manager for OS X. Installing via Homebrew Open your terminal and enter this command: brew install bash Now we’ll append our desired (Bash 4) shell’s path to a file of whitelisted system shells, and then change the system shell for our user.