std:env

The std:env module provides functions to load, read, and modify environment variables from Lua. It supports loading variables from .env files, getting values, and setting new variables in memory and in the system environment.

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Functions

env.load(filename: string): boolean

Loads variables from a .env file into memory and the system environment.

• Parameters:

  • filename (string): path to the .env file.

• Returns:

  • true if the file was loaded successfully.

Example:

local env = require("std:env")

-- Load variables from .env file
local ok = env.load(".env")
if ok then
    print("Variables loaded successfully")
end

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env.get(key: string): string?

Retrieves the value of a loaded environment variable.

• Parameters:

  • key (string): the name of the variable.

• Returns:

  • (string?) the variable value if it exists, or nil otherwise.

Example:

local env = require("std:env")

-- Get API key
local api_key = env.get("API_KEY")
print("API_KEY:", api_key)
-- API_KEY: 1234567890abcdef

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env.set(key: string, value: string): boolean

Sets or updates an environment variable in memory and in the system environment.

• Parameters:

  • key (string): the name of the variable.
  • value (string): the value to assign.

• Returns:

  • true on success.

This does not modify the .env file on disk; the change exists only during program execution.

Example:

local env = require("std:env")

-- Define or update a variable
env.set("DEBUG", "true")
print("DEBUG:", env.get("DEBUG"))
-- DEBUG: true

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Notes

• Use .env files to manage configuration variables for your application.
• load() automatically updates the system environment (os.setenv).
• set() is JIT: changes last only during the program runtime. For persistent changes, you need to modify the .env file manually.

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