Changing Shells

When using a terminal to interact with your system, the command-line interface is provided by a shell program. The two most commonly chosen shells are Bash (the Bourne Again SHell) and Z Shell (zsh).

First see if you even need to switch, or if you’re already using the shell you want by printing the name of the current shell.

$ echo $0
bash

You may have come across the $SHELL environment variable, but it won’t always do what you expect it to do as you can see below when I switch to zsh and bash is still the value of $SHELL, so you’re better off just relying on $0.

$ echo $SHELL
bash
$ zsh
$ echo $SHELL
bash

So if I’ve confirmed I’m using bash and I actually want to tinker with zsh, I can either invoke zsh as above to use it temporarily, or I can make it my default shell, so it will be the shell used automatically in new terminal sessions.

Changing your default (or login) shell is done using the chsh utility. First we’ll list the available shells to make sure it’s been correctly installed.

$ chsh -l
/bin/sh
/bin/bash
/bin/zsh
/usr/bin/zsh

Which is simply the contents of /etc/shells.

$ cat /etc/shells
/bin/sh
/bin/bash
/bin/zsh
/usr/bin/zsh

Now I invoke chsh and specify the shell I want to use.

$ chsh -s /usr/bin/zsh
Changing shell for trevor.
Password:
Shell changed.

And after logging out and logging back in (just opening a new terminal won’t work) I can confirm that zsh is now my shell.

$ echo $0
zsh