direnv

direnv – unclutter your .profile

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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.

Use cases

How it works

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

It supports hooks for all the common shells like bash, zsh, tcsh and fish. This allows project-specific environment variables without cluttering the ~/.profile file.

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 and phpenv.

Getting Started

Prerequisites

Basic Installation

  1. direnv is packaged in most distributions already. See the installation documentation for more details.
  2. hook direnv into your shell. Follow the hook installation documentation.

Now restart your shell.

Quick demo

To follow along in your shell.

# Create a new folder for demo purposes.
$ mkdir ~/my-project
$ cd ~/my-project

# Show that the FOO environment variable is not loaded.
$ echo ${FOO-nope}
nope

# Create a new .envrc. This file is bash code that is going to be loaded by
# direnv.
$ echo export FOO=foo > .envrc
.envrc is not allowed

# The security mechanism didn't allow to load the .envrc. Since we trust it,
# let's allow it's execution.
$ direnv allow .
direnv: reloading
direnv: loading .envrc
direnv export: +FOO

# Show that the FOO environment variable is loaded.
$ echo ${FOO-nope}
foo

# Exit the project
$ cd ..
direnv: unloading

# And now FOO is unset again
$ echo ${FOO-nope}
nope

The stdlib

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.

As an example, the PATH_add function is used to expand and prepend a path to the $PATH environment variable. Instead of export $PATH=$PWD/bin:$PATH you can write PATH_add bin. It’s shorter and avoids a common mistake where $PATH=bin.

To find the documentation for all available functions check the direnv-stdlib(1) man page.

It’s also possible to create your own extensions by creating a bash file at ~/.config/direnv/direnvrc or ~/.direnvrc. This file is loaded before your .envrc and thus allows you to make your own extensions to direnv.

The wiki

Make sure to take a look at the wiki! It contains all sorts of useful information such as common recipes, editor integration, tips-and-tricks.

https://github.com/direnv/direnv/wiki

FAQ

Based on GitHub issues interactions, here are the top things that have been confusing for users:

  1. direnv has a standard library of functions, a collection of utilities that I found useful to have and accumulated over the years. You can find it here: https://github.com/direnv/direnv/blob/master/stdlib.sh

  2. It’s possible to override the stdlib with your own set of function by adding a bash file to ~/.config/direnv/direnvrc. This file is loaded and it’s content made available to any .envrc file.

  3. direnv is not loading the .envrc into the current shell. It’s creating a new bash sub-process to load the stdlib, direnvrc and .envrc, and only exports the environment diff back to the original shell. This allows direnv to record the environment changes accurately and also work with all sorts of shells. It also means that aliases and functions are not exportable right now.

Contributing

Bug reports, contributions and forks are welcome. All bugs or other forms of discussion happen on http://github.com/direnv/direnv/issues .

Or drop by on IRC (#direnv on freenode) to have a chat. If you ask a question make sure to stay around as not everyone is active all day.

Similar projects

Here is a list of other projects found in the same design space. Feel free to submit new ones.

Copyright (C) 2019 shared by all contributors under the MIT licence.