From https://www.moncefbelyamani.com/which-shell-am-i-using-how-can-i-switch/

Which Shell Am I Using? How Can I Switch?

• mac
• terminal
• zsh
• bash
• homebrew
• beginner

Finding your current shell

Starting with macOS Catalina (10.15), Apple set the default shell to the Z shell (zsh). In previous macOS versions, the default was Bash.

Each shell supports a configuration file in your macOS Home folder that gets read every time you open a new terminal window (or tab). This allows the shell environment to be set up properly with your preferences, and so that the tools you depend on are ready to use.

In zsh, the configuration file is ~/.zshrc. In bash, it’s ~/.bash_profile. Some people might tell you to add things to your ~/.bashrc. Thank them for their help, and teach them that .bashrc does not get read automatically on a Mac when you open up a new shell window.

If you’re not sure which shell you’re using, there are a couple of ways to find out. One is to run this command:

echo $0

It works in bash and zsh, but not in fish. Here’s a trick I use that should work in all shells. Type any bogus command that you know doesn’t exist, for example:

monfresh

The first word in the error message should be the name of the shell. In bash, you would see this:

bash: monfresh: command not found

In zsh:

zsh: monfresh: command not found

And in fish:

fish: Unknown command: monfresh

Changing shells

If you want to switch between shells to explore the differences, or because you know you want one or the other, use these commands:

Switch to bash

chsh -s $(which bash)

Switch to zsh

chsh -s $(which zsh)

Note: What the $() syntax does is it runs what’s inside the parentheses (such as which bash), saves the output, and passes it to chsh -s. This is convenient when you don’t know the exact path to the bash or zsh command.

This will prompt you for your macOS password. For the change to take effect, you need to open a new terminal tab, or quit and restart your terminal app.

Important Note

When you switch shells, if you expect to have the same configuration, make sure to copy the contents of ~/.bash_profile into ~/.zshrc or vice versa. Also look out for any code that is not compatible with both shells.

If you’re not sure how to open and edit dotfiles, or hidden files (those with filenames that start with a period, like .zshrc), read my guide on opening hidden files on your Mac.

Possible error scenario

If you get a message about a non-standard shell, that means that your shell is not listed in /etc/shells. This can happen after installing a shell with Homebrew, which is a reasonable thing to do because you can get a newer version than the one that came with macOS.

To make macOS aware of the Homebrew version of a shell, it needs to be added to /etc/shells. Here’s how you would safely add Homebrew’s zsh:

Find the path of the Homebrew zsh:

which zsh

Open /etc/shells in Sublime Text, or another code editor, but not TextEdit:

open /etc/shells -a "Sublime Text"

Copy and paste the output of which zsh at the bottom of /etc/shells and save the file. This will prompt you for your macOS password. Run the chsh -s command again, and this time it should not complain. Remember to open a new tab to see the new shell.

Alternative

Another way to change shells is via the Terminal app preferences, by selecting the “Command (complete path)” radio button in the “Shells open with:” section as shown in the screenshot below:

Note that this does not change your default login shell, which you can check by running echo $SHELL. You can test this by following these steps:

Set your login shell to zsh:

chsh -s $(which zsh)

At the top of your ~/.zshrc, add this line:

echo "hello from zsh"

At the top of your ~/.bash_profile, add this line:

echo "hello from bash"

If the file doesn’t exist, you can create it with touch:

touch ~/.bash_profile

Update your Terminal preferences to open the shell with the command /bin/bash, as shown in the screenshot above.

Quit and restart Terminal.

You should see “hello from bash”, but if you run echo $SHELL, you will see /bin/zsh.

I’m not sure if this affects anything while developing locally, so I would stick to the default settings and use chsh -s to switch shells.

If you’re not sure how to open and edit dotfiles, or hidden files (those with filenames that start with a period, like .zshrc), read my guide on opening hidden files on your Mac.