Upgrade Bash on Mac

The default Bash that comes on your Mac is decades old, To get the newest version follow these instructions.

Note: the following instructions don’t change the old version of Bash, but rather install a new version and set it as the default. The two versions will exist side by side on your system but you can ignore the old version.

Make sure you have Homebrew installed, see here to get it if you don't already.

Install bash

brew install bash

Checking installed versions

Make sure we see both the old and the new by running which -a bash:
```
/usr/local/bin/bash
/bin/bash
```

Running /usr/local/bin/bash --version will return the following:

GNU bash, version 5.0.0(1)-release (x86_64-apple-darwin18.2.0)
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Running /bin/bash --version will return the following:

GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin18)
Copyright (C) 2007 Free Software Foundation, Inc.

Allowing the new Bash

Open your shells file for editing:
```
sudo vi /etc/shells
```
Add /usr/local/bin/bash to the file.
Change the default shell to use the new bash:
```
chsh -s /usr/local/bin/bash
```

Final verification

Close your terminal and restart it then run echo $BASH_VERSION to verify the changes worked:
```
5.0.0(1)-release
```

Last update: 2020-11-15