Zsh is only the default shell of newly created user accounts. As a result, all existing accounts on an upgraded Mac still use Bash by default unless you change it. Each user account has its own default shell preference.
From the terminal
To change the default shell of a user account under macOS, simply run the chsh -s (change shell) command in a terminal window.
Change the default shell to Bash by running the following command:
chsh -s / bin / bash
You will need to enter the password for your user account. Finally, close the terminal window and reopen it. You will use Bash instead of Zsh.
Change the default shell to Zsh by running this command:
chsh -s / bin / zsh
Enter your password when prompted. Once the terminal window is closed and reopened, you will use Zsh.
You can see a list of included shells that you can select by running the following command:
cat / etc / shells
From System Preferences
You can also change this option graphically in System Preferences if you prefer.
Go to System Preferences> Users and Groups on your Mac. Click on the lock icon and enter your password. Hold down the Ctrl key, click the name of your user account in the left pane, and then select "Advanced Options."
Click the "Login Shell" drop-down list and select "/ bin / bash" to use Bash as the default shell or "/ bin / zsh" to use Zsh as the default shell. Click "OK" to save your changes.
Bash on macOS is still out of date
Note that the version of Bash (Bourne Again SHell) included with macOS is still quite outdated. If you run bash –version, you will see that Catalina includes Bash 3.2.57 when Bash 5.0 is the latest version. The most recent versions are licensed under GPLv3, while Apple still distributes a licensed version of GPLv2.
On the other hand, the version of Zsh (shell Z) supplied with macOS (check with zsh – version) is Zsh 5.7.2, which is the most recent version at the time of the release of Catalina.
If you want the latest version of Bash, you can install it yourself via Homebrew.