direnv
is an environment switcher for the shell. It knows how to hook into
bash, zsh, tcsh, fish shell and elvish 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.
$ 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
direnv is packaged for a variety of systems:
- Fedora
- Arch AUR
- Debian
- Gentoo go-overlay
- NetBSD pkgsrc-wip
- NixOS
- OSX Homebrew
- OpenSuSe
- MacPorts
- Ubuntu
- GNU Guix
See also:
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 go environment https://golang.org/doc/install
go >= 1.9 is required
Clone project:
$ git clone [email protected]:direnv/direnv.git
Build by just typing make:
$ cd direnv
$ make
To install to /usr/local:
$ make install
Or to a different location like ~/.local
:
$ make install DESTDIR=~/.local
For direnv to work properly it needs to be hooked into the shell. Each shell has its own extension mechanism:
Add the following line at the end of the ~/.bashrc
file:
eval "$(direnv hook bash)"
Make sure it appears even after rvm, git-prompt and other shell extensions that manipulate the prompt.
Add the following line at the end of the ~/.zshrc
file:
eval "$(direnv hook zsh)"
Add the following line at the end of the ~/.config/fish/config.fish
file:
eval (direnv hook fish)
Add the following line at the end of the ~/.cshrc
file:
eval `direnv hook tcsh`
Run:
$> direnv hook elvish > ~/.elvish/lib/direnv.elv
and add the following line to your ~/.elvish/rc.elv
file:
use direnv
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.
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.
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 ..
In the general case source_up
will load any .envrc higher up in the folder structure. This allows you to truely enable arbitrary heirarchical stuctures of .envrc
usage.
source_up
Based on GitHub issues interractions, here are the top things that have been confusing for users:
-
direnv has a standard library of functions, a collection of utilities that I found useful to have and accumulated over the years. If you know how to read bash, you can find it here: https://github.com/direnv/direnv/blob/master/stdlib.sh
-
It's possible to override the stdlib with your own set of function by adding a bash file to either
~/.config/direnv/direnvrc
or~/.direnvrc
. These will become available to all your.envrc
files. -
direnv is actually creating a new bash 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.
- 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).
- asdf - a pure bash solution that has a plugin system
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:[email protected]
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.
Copyright (C) 2014 shared by all contributors under the MIT licence.