# Startup Files: .bashrc, .zshrc and source

Bash reads ~/.bashrc every time a terminal opens, and a Mac's zsh reads ~/.zshrc, so aliases and functions you add there are always ready; keep a backup before you edit it, and use source to load your changes into the shell you're in.

Apprentice · Unix · Linux · Updated November 10, 2026

## After this lesson you can

- Add aliases and functions to ~/.bashrc, or ~/.zshrc on a Mac, after keeping a backup copy, so every new terminal has them
- Load changes into the shell you're in with source, and explain why bash file.sh doesn't keep them

## Key takeaways

- Every new bash reads ~/.bashrc before its first prompt, and a Mac's zsh reads ~/.zshrc. Lines you add at the end run in every new terminal.
- Copy the file before you change it, with cp ~/.bashrc ~/.bashrc.backup, so one wrong line is quick to undo.
- source ~/.bashrc, or . ~/.bashrc, runs the file in the shell you're in, so your changes work without opening a new terminal.
- bash and a file's name runs the file in a separate shell, which forgets everything it set when it ends.

Yesterday you made `todo` and `mkcd`. This morning you open a terminal, type `todo`, and get this:

```text
Command 'todo' not found, but can be installed with:
sudo apt install devtodo
```

Everything you typed at the prompt went away with yesterday's window. Then a tutorial for a tool you're installing says "add this line to your `.bashrc`", as if you'd know what that is. This lesson shows you where your shortcuts go so they're there every day, and it changes a real settings file of yours, so it starts with a copy. Web developers and IT administrators edit this file all the time: it's where a computer's terminal becomes theirs.

## The file bash reads every time it starts

A pilot runs through the same checklist before every flight. Bash has one too: before it shows its first prompt, it reads a file in your home folder called `.bashrc` (read "dot bash R C"; the *rc* stands for *run commands*) and runs every line in it, top to bottom. It's a **configuration file**, and the dot at the start makes it hidden, so `ls -a` shows it:

```bash
ls -a ~
```

```text
.  ..  .bash_logout  .bashrc  .profile  terminal-practice
```

That's a new Ubuntu account with only the course's practice folder in it; yours has more names. The aliases from the last lesson's list live in this file. `grep -n` finds them with their line numbers:

```bash
grep -n "alias l" ~/.bashrc
```

```text
78:    alias ls='ls --color=auto'
91:alias ll='ls -alF'
92:alias la='ls -A'
93:alias l='ls -CF'
```

Ubuntu's own `ll`, on line 91. Your line numbers may differ on another version of Ubuntu.

## Keep a backup, then add your lines

You're about to change a file that runs every time a terminal opens. One typo, and every new terminal starts with an error message; one `>` typed where you meant `>>`, and the whole file is empty. So make a copy first, every time:

```bash
cp ~/.bashrc ~/.bashrc.backup
ls -a ~
```

```text
.  ..  .bash_logout  .bashrc  .bashrc.backup  .profile  terminal-practice
```

If anything goes wrong, `cp ~/.bashrc.backup ~/.bashrc` puts the old file back. And keep the terminal you edited in open until a new one works: it's already running, so a broken file can't stop it.

Now open the file in nano (*Editing in the Terminal: nano*) with `nano ~/.bashrc`, press **Alt+/** to jump to the last line, and add your shortcuts below everything Ubuntu wrote. A comment line, starting with `#`, tells future you what they are:

```bash
# My shortcuts
alias ll='ls -lah'
alias todo='cat ~/terminal-practice/shortcuts/todo.txt'
mkcd() {
  mkdir -p "$1"
  cd "$1"
}
```

Save with **Ctrl+O** and Enter, and quit with **Ctrl+X**. Then look at the end of the file:

```bash
tail -n 7 ~/.bashrc
```

```text
# My shortcuts
alias ll='ls -lah'
alias todo='cat ~/terminal-practice/shortcuts/todo.txt'
mkcd() {
  mkdir -p "$1"
  cd "$1"
}
```

On a Mac, the file is `~/.zshrc`. It may not exist yet; `nano ~/.zshrc` makes it.

## source: load it now

Type `todo` in the same terminal, and it's still not found. Bash read `.bashrc` when this terminal opened, before your lines were there. A new terminal reads the new file. Or tell the shell you're in to read it again with `source` (on a Mac, `source ~/.zshrc`):

```bash
source ~/.bashrc
todo
```

```text
water the plants
call the dentist
buy coffee beans
```

A dot does the same: `. ~/.bashrc` (read "dot, then the file"). Why not run the file like a program? Try it with a small file of your own:

```bash
echo "alias today='date +%A'" > ~/terminal-practice/shortcuts/today.sh
bash ~/terminal-practice/shortcuts/today.sh
today
```

```text
today: command not found
```

`bash` and a file's name starts a second shell. That shell read the file, made the alias, and ended, and the alias ended with it, like a note handed to a friend who then leaves. `source` reads the file in your own shell, so what it sets stays:

```bash
source ~/terminal-practice/shortcuts/today.sh
today
```

```text
Monday
```

Yours prints today's day.

![Two ways to load a settings file: on the left, bash today.sh hands the file to a second shell that makes the alias today and then closes, so your shell answers "today: command not found"; on the right, source today.sh reads the file in your own shell, and today prints Monday](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/bcffea7d3872464da5306a954c44cc0a.webp)

## Which file, on which computer

| Computer | Shell | Put your lines in | Load them now |
|---|---|---|---|
| Ubuntu, and Ubuntu in WSL on Windows | bash | `~/.bashrc` | `source ~/.bashrc` |
| A Mac | zsh | `~/.zshrc` | `source ~/.zshrc` |

When you sign in to a computer over the network, bash starts as a **login shell** and reads a different file first: `~/.bash_profile`, or on Ubuntu `~/.profile`. Ubuntu's `~/.profile` loads `~/.bashrc` for you, so `.bashrc` is the one place you need. One trap: if a tutorial says to make a `~/.bash_profile` on Ubuntu, think twice. Once that file exists, a login shell reads it instead of `~/.profile`, and your `.bashrc` stops loading there.

## Try it in the terminal

[Terminal Quest: The Clockwork Workshop, goal 6](https://www.ask-codey.com/games/terminal-quest/workshop/bash/step): played right on the lesson page.

The gearbox needs its settings loaded into your shell, not into a separate one. Load the settings file the way that keeps what it sets.

## Check yourself

2 questions to try on the lesson page.

## So what

`~/.bashrc` is where your terminal becomes yours: copy it, add your lines at the end, `source` it, and every terminal you open from now on knows your shortcuts.

## Key terms

- [.bashrc and .profile](https://www.ask-codey.com/glossary/bashrc-and-profile)
- [source](https://www.ask-codey.com/glossary/source-unix)
- [Login Shell](https://www.ask-codey.com/glossary/login-shell)
- [Configuration File](https://www.ask-codey.com/glossary/configuration-file)

## Cheat sheets

- [Startup Files: .bashrc, .zshrc and source](https://www.ask-codey.com/cheat-sheets/bash-startup-files-cheat-sheet)

## Related

- [Aliases and Small Functions](https://www.ask-codey.com/lessons/bash-aliases-and-small-functions)
- [Editing in the Terminal: nano](https://www.ask-codey.com/lessons/bash-editing-with-nano)
- [A Prompt in Your Colors](https://www.ask-codey.com/lessons/bash-custom-prompt)

Source: https://www.ask-codey.com/lessons/bash-startup-files