I can't seem to switch to zsh

Run this command in the Terminal:

sudo chsh -s /bin/zsh

Enter your admin password at the prompt. It will not echo any characters. Press return.

The Zsh shell does not read any of your Bash dot startup files, and needs its own to set the path and a different prompt syntax:

Copy and paste the following into a text editor as plain text and save it in your home directory as .zshrc — the leading dot is very important, as it will be a hidden file from the Finder and Terminal, but Zsh is looking for that particular file.

# .zshrc

export PATH="$HOME:/usr/local/bin:${PATH}"
# Zsh shell prompt %m - hostname %~ - current directory %% - prompt character
PS1="%m: %~ %% "

You can then do the following to make these settings current in the present Terminal session:

source ~/.zshrc

and each time you launch the Terminal with the Zsh shell, it will run the contents of the .zshrc file.

The current manual for the Zsh shell is here. You can also get help in the Terminal via:

man zsh

The first thing you should try is to change the first line in your o.sh file to the following:

#!/bin/zsh

Then make it executable if it is not already, and run it.

chmod +x o.sh
./o.sh

What breaks when you run it? Many Bash shell constructs work the same in Zsh and some do not. We are flying blind without you posting the contents of o.sh here.

Click the <> code insertion button on the bottom toolbar, click in its light gray insertion field (as I did above) in this editor, and copy/paste the o.sh source. Press a return at the end of your code, and then click the <> button again to stop code insertion.

A Bash script with the first line #!/bin/bash or #!/bin/sh (still Bash) will run as a Bash script while in the Zsh shell. The #!/bin/zsh entry would be used if there are features unique to the Zsh shell in the script.

SergioQ wrote:

I keep getting the message below when I run ./o.sh from my terminal. I have run the update, it says no changes are made. I tried lookin go the option to change via System Preferences, but can't find it.

Am totally confused as to what I need to do. Do I have to change the extension of my sh file?

The default interactive shell is now zsh.

To update your account to use zsh, please run `chsh -s /bin/zsh`.

For more details, please visit https://support.apple.com/kb/HT208050.

bash-3.2$ 

bash-3.2$ exit

How did this go for you SergioQ are you up and running your zsh ...?

To see you current shell:

 echo $SHELL

hot link to man zsh, if you copy & paste into Safari or save locally :

x-man-page://zsh

You should always "/bin/sh" in the shebang line unless it doesn't work for some reason.