Course/Customizing Your Terminal/Shell Config Files

Shell Config Files

Understand .bashrc, .zshrc, and .bash_profile — what they are and when they load.

Every time you open a terminal, your shell reads one or more configuration files before it shows you a prompt. These files are where your aliases, PATH changes, custom functions, and environment variables live. Understanding which file loads when is the key to customizing your terminal reliably.

The two most common shells are Bash and Zsh. macOS switched its default shell from Bash to Zsh in 2019 (Catalina), while most Linux distributions still default to Bash. Each shell has its own set of config files, but they follow similar patterns.

For Bash, there are two main files. ~/.bash_profile runs when you start a login shell — the first terminal session you open, or when you SSH into a server. ~/.bashrc runs for every new interactive non-login shell — like opening a new tab in your terminal. A common pattern is to have .bash_profile source .bashrc so your settings are consistent everywhere.

# Inside ~/.bash_profile — source .bashrc so settings work everywhere
if [ -f ~/.bashrc ]; then
    source ~/.bashrc
fi

For Zsh, life is simpler. ~/.zshrc runs for every interactive shell session — login or not. This is the one file you'll edit most often if you use Zsh. There's also ~/.zprofile (similar to .bash_profile) and ~/.zshenv (which runs for every shell, even scripts), but .zshrc is the star.

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Not sure which shell you're running? Type echo $SHELL in your terminal. You'll see something like /bin/zsh or /bin/bash.

These config files are hidden — their names start with a dot. That's why you won't see them with a plain ls. You need ls -a to reveal them. Let's look at the simulated config files in this lesson. Try viewing the contents of .bashrc or .zshrc using cat.

cat .bashrc
cat .zshrc

WIN

Windows doesn't use .bashrc or .zshrc. PowerShell uses a profile script located at $PROFILE (usually ~\Documents\PowerShell\Microsoft.PowerShell_profile.ps1). You can find its path by running echo $PROFILE in PowerShell. If you're using WSL, your Linux shell config files work exactly as described here.

Practice