A shell is a program that lets users issue commands to the Operating System (OS). Some shells are text-based and some are graphical. On MacOS, for instance, the default command line shell (since Catalina) is `zsh` while the default graphical user interface shell is the Finder. Both enable the users to run programs. 1. Start the terminal emulator to run the shell. - The percent sign (`%`) at the end of the prompt generally means that this is `zsh` waiting for a command. zsh prompt

- We could confirm which shell is running by using `echo $0` or `echo $SHELL`. current shell

- Note that variables are case sensitive and predefined variables are usually in uppercase. So `echo $shell` won't return the same value as `echo $SHELL`. - To avoid accidentally overriding predefined variables, prefer lowercase names for other user defined variables. Inspect the variable using `echo` because variables may contain commands which could cause permanent changes if executed directly (e.g. files could be deleted). - It's also good to check first from where you are about to launch the binary (e.g. `which zsh`, `which scutil`, etc.).
2. Use `cat /etc/shells` to list acceptable shells. - Notice that MacOS also ships with `bash` and `sh`.
list of acceptable shells

3. We can find the system wide configuration for the zsh prompt in the `/etc` directory. Read through the file with pagination ^{[1] [2]} using `less /etc/zshrc` . - Here the primary prompt string is defined as `PS1="%n@%m %1~ %# "` - `%n` - username - `%m` - host name *** *more about zsh variables [here](https://zsh.sourceforge.io/Doc/Release/Variables-Index.html)* zsh system wide configuration

4. Be careful when editing system wide configuration. Instead, create a user specific configuration in the home directory. - `nano ~/.zshrc` - Set `PS1` variable without `%n` and `%m` - `PS1="%1~ %# "` zshrc customized prompt

5. Open a new zsh session. We can see that the username and host name are not displayed anymore. zsh prompt without the username and host name

6. The `PROMPT` variable can also be used. This is the same as `PS1`. - While on the terminal, try `export PROMPT="🌱 christine@dev %1~ %# "` export PROMPT from the terminal

7. And lastly, here's a Kaomoji prompt just for fun 😊 - `PS1="(ノ°∀°)ノ⌒･*:.｡..｡.:*･゜ﾟ･*☆.·𝓈𝑒𝑒 𝓎𝑜𝓊 ☆´¨ %1~ %# "`

Customizing zsh prompt: How to remove the username and host name

[Javascript Basics] Day 5: Arrays

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