dotenv-rs

从 dotenv 分叉而来

使用 Dotenv 的示例项目如下

extern crate dotenv_rs;

use dotenv_rs::dotenv;
use std::env;

fn main() {
    dotenv().ok();

    for (key, value) in env::vars() {
        println!("{}: {}", key, value);
    }
    dotenv_with_prefix(&String::from("Test")).ok();

    for (key, value) in env::vars() {
        println!("{}: {}", key, value);
    }
}

变量替换

可以使用 .env 文件中的 $VARIABLE 语法重用变量。语法和规则类似于 bash，以下是一个示例

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 将解析文件，按照注释中的描述替换变量。

使用 dotenv! 宏

将 dotenv_codegen 添加到您的依赖项中，并在您的 crate 的顶部添加以下内容

#[macro_use]
extern crate dotenv_codegen;

然后，在您的 crate 中

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