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direnv

A shell extension that loads environment variables per-directory.

direnv loads and unloads environment variables based on the current working directory. When you cd into a directory that contains a .envrc file (and you have approved it once with direnv allow), direnv injects the variables into your shell; when you cd out, they are automatically removed. The result is per- project tooling configuration without polluting the global shell environment.

Zimbatm (Jonas Pfenniger) started direnv around 2014. Standard .envrc helpers cover layout commands like layout python (auto- activate a virtualenv), layout node, source_up (inherit parents), and use nix or use flake (drop into a Nix shell), so most projects need only a one-line file.

direnv has become the standard way to manage per-project environment variables on Unix systems. The Nix and Home Manager communities lean on it heavily for development shells, and many dotfile setups in the modern Rust/Go/Node toolchain combine direnv with mise or asdf for runtime version selection.

Debian/Ubuntu: sudo apt install direnv
Fedora/RHEL:   sudo dnf install direnv
Arch:          sudo pacman -S direnv
macOS:         brew install direnv