Make the shell yours: dotfiles

Your alias vanished when you closed the terminal, because it only lived in that shell. To keep something, put it in a startup file. These are called dotfiles because their names start with a dot, which hides them from a plain ls.

• ~/.bashrc runs for each new interactive shell, like a new terminal tab. Aliases, functions and your prompt go here.
• ~/.bash_profile (or ~/.profile) runs for login shells, such as when you connect over SSH. Environment variables go here. Most people make it load .bashrc too.
• Scripts run neither, which is why an alias that works at your prompt fails inside a script.

A change doesn’t affect shells that are already open. To apply it right now, run source ~/.bashrc, which runs the file in your current shell.

macOS note: its default shell is now zsh, so the equivalent file is ~/.zshrc.

Many engineers keep their dotfiles in a Git repository and link them into place, so a new machine feels like home in a minute. Treat that repository as public, even if it’s private: API keys and tokens don’t belong in dotfiles. Load those from a secrets manager or a separate, ignored file.