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:

Storing configuration in the environment is one of the tenets of a twelve-factor app. 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

Usage

The easiest and most common usage consists on calling

dotenv::dotenv

.env

std::os

If you need finer control about the name of the file or its location, you can use the

from_filename

from_path

dotenv_codegen

dotenv!

env!

.env

Examples

A

.env

# a comment, will be ignored
REDIS_ADDRESS=localhost:6379
MEANING_OF_LIFE=42

You can optionally prefix each line with the word

export

A sample project using Dotenv would look like this:

extern crate dotenv;

use dotenv::dotenv;
use std::env;
fn main() {
    dotenv().ok();
for (key, value) in env::vars() {
    println!("{}: {}", key, value);
}
}

Variable substitution

It's possible to reuse variables in the

.env

$VARIABLE

VAR=one
VAR_2=two

Non-existing values are replaced with an empty string
RESULT=$NOPE #value: '' (empty string)
All the letters after $ symbol are treated as the variable name to replace
RESULT=$VAR #value: 'one'
Double quotes do not affect the substitution
RESULT="$VAR" #value: 'one'
Different syntax, same result
RESULT=${VAR} #value: 'one'
Curly braces are useful in cases when we need to use a variable with non-alphanumeric name
RESULT=$VAR_2 #value: 'one_2' since $ with no curly braces stops after first non-alphanumeric symbol 
RESULT=${VAR_2} #value: 'two'
The replacement can be escaped with either single quotes or a backslash:
RESULT='$VAR' #value: '$VAR'
RESULT=$VAR #value: '$VAR'
Environment variables are used in the substutution and always override the local variables
RESULT=$PATH #value: the contents of the $PATH environment variable
PATH="My local variable value"
RESULT=$PATH #value: the contents of the $PATH environment variable, even though the local variable is defined

Dotenv will parse the file, substituting the variables the way it's described in the comments.

Using the

dotenv!

macro

Add

dotenv_codegen

#[macro_use]
extern crate dotenv_codegen;

Then, in your crate:

fn main() {
  println!("{}", dotenv!("MEANING_OF_LIFE"));
}