direnv -- Unclutter your .profile

direnv is an environment switcher for the shell. It knows how to hook into bash, zsh, tcsh and fish shell to load or unload environment variables depending on the current directory. This allows project-specific environment variables without cluttering the "~/.profile" file.

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.

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.

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

Install

From source

Dependencies: make, golang

git clone https://github.com/direnv/direnv
cd direnv
make install
# or symlink ./direnv into the $PATH

From system packages

direnv is packaged for a variety of systems:

Non-official builds for Debian and Fedora are also available at https://dl.equinox.io/zimbatm/direnv/stable

From binary builds

Binary builds for a variety of architectures are also available for each release.

Fetch the binary, chmod +x direnv and put it somewhere in your PATH.

Setup

For direnv to work properly it needs to be hooked into the shell. Each shell has its 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 "~/.config/fish/config.fish" file:

eval (direnv hook fish)

TCSH

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

eval `direnv hook tcsh`

Usage

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

Note that the contents of the .envrc file must be valid bash syntax, regardless of the shell you are using. This is because direnv always executes the .envrc with bash (a sort of lowest common denominator of UNIX shells) so that direnv can work across shells. If you try to use some syntax that doesn't work in bash (like zsh's nested expansions), you will run into trouble.

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 allows it if the file's modification time has changed.

Now that the environment is loaded, you will 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 basis of the mechanism that allows you to build cool things.

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.

Loading layered .envrc

Let's say you have the following structure:

"/a/.envrc"
"/a/b/.envrc"

If you add the following line in "/a/b/.envrc", you can load both of the ".envrc" files when you are in /a/b:

source_env ..

Similar projects

Environment Modules - one of the oldest (in a good way) environment-loading systems
autoenv - lightweight; doesn't support unloads
zsh-autoenv - a feature-rich mixture of autoenv and smartcd: enter/leave events, nesting, stashing (Zsh-only).

Contribute

Bug reports, contributions and forks are welcome.

All bugs or other forms of discussion happen on http://github.com/direnv/direnv/issues.

There is a wiki available where you can share your usage patterns or other tips and tricks https://github.com/direnv/direnv/wiki

For longer form discussions you can also write to mailto:direnv-discuss@googlegroups.com

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.

anton-ryzhov / direnv