direnv

direnv is an extension for your shell. It augments existing shells with a new feature that can load and unload environment variables depending on the current directory.

Key Features

Automatic Environment Management: Loads environment variables when you enter a directory containing a .envrc file and unloads them when you leave.
Shell Agnostic: Supports hooks for all common shells (bash, zsh, fish, etc.).
Language Agnostic: Works for any programming language.
Security: Prevents loading .envrc files until explicitly authorized.
Standard Library (stdlib): Provides utility functions like PATH_add to simplify common tasks.

Installation on macOS

Standard method for macOS is via Homebrew:

Install via Homebrew:
```
brew install direnv
```
Hook into your shell: Add the hook to your shell configuration file (e.g., ~/.zshrc).
```
# For Zsh, add to ~/.zshrc
eval "$(direnv hook zsh)"
```
Restart your shell or source your config file.

Basic Usage

Create a .envrc file:
```
echo "export FOO=bar" > .envrc
```
Authorize the file:
```
direnv allow .
```
Verify: The variable FOO is now available. If you cd .. out of the directory, the variable will be automatically unset.