After you've installed direnv, any directory containing a
.envrc file will be executed when you enter that directory in your shell. Pairs well with basic commands for managing programming language environments.
This is super handy for loading secret values as environment variables in your programming projects.
For example, say you have an AWS token for your project that you want to keep secret, but make available to your program; you create a
.envrc file in that directory with
direnv edit ., and fill it in with these contents:
save the file, exit your editor, and direnv will load that variable into the shell for you.
$ direnv edit . direnv: loading /home/llimllib/test/.envrc direnv: export +AWS_TOKEN
when you leave the directory, direnv will remove the variable from your environment:
$ cd ~ direnv: unloading $ echo "aws token is now empty: <$AWS_TOKEN>" aws token is now empty: <>
For security reasons, direnv won't execute a
.envrc file until you tell it to do so with
$ mkdir test $ echo "export AWS_TOKEN=blahblah" > test/.envrc $ cd test direnv: error /tmp/test/.envrc is blocked. Run `direnv allow` to approve its content $ direnv allow direnv: loading /tmp/test/.envrc direnv: export +AWS_TOKEN
What direnv is actually doing is (roughly) starting up a new shell, executing the
.envrc file, comparing the environment variables between the two, and importing the variables into your current session that are new.
That means that it is not executing the
.envrc file in your current shell session, which means that running a program that modifies your environment, like activating a python virtualenv might not work exactly like you expect it to.
If you try to activate a python virtualenv in a
activate will modify your environment to insert its own python on your
PATH - this will work because
direnv will import the update path. However, it also tries to modify your command line prompt via
$PS1, which is a local variable, and as such will not propagate back to your shell.
The direnv wiki lists some workarounds, but they're fairly gross. I just live without the updated
There are some common programming environment layouts available - for example if you add
layout node to your
.envrc, direnv will put
$PWD/node_modules/.bin on your
PATH when you enter the directory.