direnv - Man Page

unclutter your .profile

Examples (TL;DR)

Grant direnv permission to load the .envrc present in the current directory: direnv allow .
Revoke the authorization to load the .envrc present in the current directory: direnv deny .
Edit the .envrc file in the default text editor and reload the environment on exit: direnv edit .
Trigger a reload of the environment: direnv reload
Print some debug status information: direnv status

direnv is an environment variable manager for your shell. It knows how to hook into bash, zsh and fish shell to load or unload environment variables depending on your current directory. This allows you to have project-specific environment variables and not clutter the "~/.profile" file.

Before each prompt it checks for the existence of an .envrc file in the current and parent directories. If the file exists, it is loaded into a bash sub-shell and all exported variables are then captured by direnv and then made available to your current shell, while unset variables are removed.

Because direnv is compiled into a single static executable it is fast enough to be unnoticeable on each prompt. It is also language agnostic and can be used to build solutions similar to rbenv, pyenv, phpenv, ...

Example

$ cd ~/my_project
$ echo ${FOO-nope}
nope
$ echo export FOO=foo > .envrc
\.envrc is not allowed
$ direnv allow .
direnv: reloading
direnv: loading .envrc
direnv export: +FOO
$ echo ${FOO-nope}
foo
$ cd ..
direnv: unloading
direnv export: ~PATH
$ echo ${FOO-nope}
nope

Setup

For direnv to work properly it needs to be hooked into the shell. Each shell has it's own extension mechanism:

Bash

Add the following line at the end of the ~/.bashrc file:

eval "$(direnv hook bash)"

Make sure it appears even after rvm, git-prompt and other shell extensions that manipulate the prompt.

ZSH

Add the following line at the end of the ~/.zshrc file:

eval "$(direnv hook zsh)"

Fish

Add the following line at the end of the $XDG_CONFIG_HOME/fish/config.fish file:

direnv hook fish | source

Fish supports 3 modes you can set with with the global environment variable direnv_fish_mode:

set -g direnv_fish_mode eval_on_arrow    # trigger direnv at prompt, and on every arrow-based directory change (default)
set -g direnv_fish_mode eval_after_arrow # trigger direnv at prompt, and only after arrow-based directory changes before executing command
set -g direnv_fish_mode disable_arrow    # trigger direnv at prompt only, this is similar functionality to the original behavior

TCSH

Add the following line at the end of the ~/.cshrc file:

eval `direnv hook tcsh`

Elvish

Run:

$> direnv hook elvish > ~/.elvish/lib/direnv.elv

and add the following line to your ~/.elvish/rc.elv file:

use direnv

Usage

In some target folder, create an .envrc file and add some export(1) and unset(1) directives in it.

On the next prompt you will notice that direnv complains about the .envrc being blocked. This is the security mechanism to avoid loading new files automatically. Otherwise any git repo that you pull, or tar archive that you unpack, would be able to wipe your hard drive once you cd into it.

So here we are pretty sure that it won't do anything bad. Type direnv allow . and watch direnv loading your new environment. Note that direnv edit . is a handy shortcut that opens the file in your $EDITOR and automatically reloads it if the file's modification time has changed.

Now that the environment is loaded you can notice that once you cd out of the directory it automatically gets unloaded. If you cd back into it it's loaded again. That's the base of the mechanism that allows you to build cool things.

Exporting variables by hand is a bit repetitive so direnv provides a set of utility functions that are made available in the context of the .envrc file. Check the direnv-stdlib(1) man page for more details. You can also define your own extensions inside $XDG_CONFIG_HOME/direnv/direnvrc or $XDG_CONFIG_HOME/direnv/lib/*.sh files.

Hopefully this is enough to get you started.

Environment

XDG_CONFIG_HOME: Defaults to $HOME/.config.

Files

$XDG_CONFIG_HOME/direnv/direnv.toml: Direnv configuration. See direnv.toml(1).
$XDG_CONFIG_HOME/direnv/direnvrc: Bash code loaded before every .envrc. Good for personal extensions.
$XDG_CONFIG_HOME/direnv/lib/*.sh: Bash code loaded before every .envrc. Good for third-party extensions.
$XDG_DATA_HOME/direnv/allow: Records which .envrc files have been direnv allowed.