Shell Configuration Files

Why are there so many of them?

zsh reads up to four config files at startup. Each has a different purpose. Putting the right line in the wrong file is the most common "my env doesn't load" bug.

The four zsh files

~/.zshenv — runs for every zsh invocation, including non-interactive scripts. Use sparingly.
~/.zprofile — login shells only (the first shell of a session). Set $PATH here. Homebrew shellenv lives here.
~/.zshrc — interactive shells. Aliases, prompts, plugins, completion. Most of your config goes here.
~/.zlogin — login shells, after .zshrc. Rarely used.

The bash equivalents

~/.bash_profile — login shells.
~/.bashrc — interactive non-login shells.
Old hack: source one from the other so you only edit .bashrc.

Login vs interactive (preview)

Login shell = first shell of a session (Terminal opens, ssh, su -). Interactive = you can type at a prompt. Most macOS Terminal sessions are both; ssh sessions are too. Subshells (bash from inside zsh) are interactive but not login. Next lesson covers the table.

Where to put what

PATH and locale → .zprofile (so non-interactive scripts via launchd see them too).
Aliases, functions, prompt → .zshrc.
Variables you want every script to see → .zshenv (rare).

Reload after editing

source ~/.zshrc or exec zsh reloads. The second is cleaner — it replaces the current shell with a fresh one and preserves your terminal window.

Code

Verify the load order·bash

# Add a print to each file so you can see when each runs
echo 'echo ".zshenv loaded"'   >> ~/.zshenv
echo 'echo ".zprofile loaded"' >> ~/.zprofile
echo 'echo ".zshrc loaded"'    >> ~/.zshrc
# Open a new terminal — note the order
# Then remove these lines once you've seen them

Reload without closing the terminal·bash

exec zsh           # cleanest
source ~/.zshrc    # also fine for interactive only
# After editing PATH / .zprofile, prefer exec zsh

Why are there so many of them?

The four zsh files

The bash equivalents

Login vs interactive (preview)

Where to put what

Reload after editing

Code

External links

Exercise

Progress

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