rust-dotenv [](https://travis-ci.org/slapresta/rust-dotenv)
====
**Achtung!** This is a v0.\* version! Expect bugs and issues all around.
Submitting pull requests and issues is highly encouraged!
Quoting [bkeepers/dotenv][dotenv]:
> Storing [configuration in the environment](http://www.12factor.net/config)
> is one of the tenets of a [twelve-factor app](http://www.12factor.net/).
> Anything that is likely to change between deployment environments–such as
> resource handles for databases or credentials for external services–should
> be extracted from the code into environment variables.
This library is meant to be used on development or testing environments in
which setting environment variables is not practical. It loads environment
variables from a `.env` file, if available, and mashes those with the actual
environment variables provided by the operative system.
Usage
----
The easiest and most common usage consists on calling `dotenv::dotenv` when the
application starts, which will load environment variables from a file named
`.env` in the current directory or any of its parents; after that, you can just call
the environment-related method you need as provided by `std::os`.
If you need finer control about the name of the file or its location, you can
use the `from_filename` and `from_path` methods provided by the crate.
`dotenv_codegen` and `dotenv_macros` also provide the `dotenv!` macro, which
behaves identically to `env!`, but first tries to load a `.env` file at compile
time.
Examples
----
A `.env` file looks like this:
```sh
# a comment, will be ignored
REDIS_ADDRESS=localhost:6379
MEANING_OF_LIFE=42
```
You can optionally prefix each line with the word `export`, which will
conveniently allow you to source the whole file on your shell.
A sample project using Dotenv would look like this:
```rust
extern crate dotenv;
use dotenv::dotenv;
use std::env;
fn main() {
dotenv().ok();
for (key, value) in env::vars() {
println!("{}: {}", key, value);
}
}
```
Using the `dotenv!` macro on nightly
------------------------------------
Add `dotenv_macros` to your dependencies, and add `#![plugin(dotenv_macros)]` to
the top of your crate.
Using the `dotenv!` macro on stable
-----------------------------------
You can use `dotenv!` on stable using `syntex`. You'll need to add
`dotenv_codegen` and `syntex` to your build dependencies.
#### In `main.rs`:
```rust
include!(concat!(env!("OUT_DIR"), "/main.rs"));
```
#### In `main.in.rs`:
```rust
fn main() {
println!("{}", &dotenv!("MEANING_OF_LIFE"));
}
```
#### In `build.rs`:
```rust
extern crate syntex;
extern crate dotenv_codegen;
use std::env;
use std::path::Path;
pub fn main() {
let out_dir = env::var_os("OUT_DIR").unwrap();
let mut registry = syntex::Registry::new();
dotenv_codegen::register(&mut registry);
let src = Path::new("tests/main.in.rs");
let dst = Path::new(&out_dir).join("main.rs");
registry.expand("", &src, &dst).unwrap();
}
```
#### In `.env`:
```sh
MEANING_OF_LIFE=42
```
[dotenv]: https://github.com/bkeepers/dotenv