dotenv is a library that loads environment variables from a .env file into std.os.environ. Storing configuration in the environment separate from code is based on The Twelve-Factor App methodology.

This library is a Zig language port of nodejs dotenv.

Test with Zig 0.12.0-dev.1664+8ca4a5240.

Automatically find the .env file and load the variables into the process environment with just one line.

const std = @import("std");
const dotenv = @import("dotenv");

pub fn main() !void {
    const allocator = std.heap.page_allocator;

    try dotenv.load(allocator, .{});
}

By default, it will search for a file named .env in the working directory and its parent directories recursively. Of course, you can specify a path if desired.

pub fn main() !void {
    try dotenv.loadFrom(allocator, "/app/.env", .{});
}

Since writing to std.os.environ requires a C setenv call, linking with C is necessary.

If you only want to read and parse the contents of the .env file, you can try the following.

pub fn main() !void {
    var envs = try dotenv.getDataFrom(allocator, ".env");

    var it = envs.iterator();
    while (it.next()) |*entry| {
        std.debug.print(
            "{s}={s}\n",
            .{ entry.key_ptr.*, entry.value_ptr.*.? },
        );
    }
}

This does not require linking with a C library. The caller owns the memory, so you need to free both the key and value in the hashmap.

NAME_1="VALUE_1"
NAME_2='VALUE_2'
NAME_3=VALUE_3

The value of a variable can span multiple lines(quotes are required).

PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----
ABCD...
-----END RSA PRIVATE KEY-----"

Comments start with a #.

# This is a comment
NAME="VALUE" # comment

You can reference a variable using ${}, and the variable should be defined earlier.

HO="/home"
ME="/koyori"

HOME="${HO}${ME}"  # equal to HOME=/home/koyori

Add dotenv as dependency in build.zig.zon:

.{
    .name = "my-project",
    .version = "0.1.0",
    .dependencies = .{
       .dotenv = .{
           .url = "https://github.com/dying-will-bullet/dotenv/archive/refs/tags/v0.1.1.tar.gz",
           .hash = "1220f0f6736020856641d3644ef44f95ce21f3923d5dae7f9ac8658187574d36bcb8"
       },
    },
    .paths = .{""}
}

Add dotenv as a module in build.zig:

diff --git a/build.zig b/build.zig
index 957f625..66dd12a 100644
--- a/build.zig
+++ b/build.zig
@@ -15,6 +15,9 @@ pub fn build(b: *std.Build) void {
     // set a preferred release mode, allowing the user to decide how to optimize.
     const optimize = b.standardOptimizeOption(.{});

+    const opts = .{ .target = target, .optimize = optimize };
+    const dotenv_module = b.dependency("dotenv", opts).module("dotenv");
+
     const exe = b.addExecutable(.{
         .name = "tmp",
         // In this case the main source file is merely a path, however, in more
@@ -23,6 +26,8 @@ pub fn build(b: *std.Build) void {
         .target = target,
         .optimize = optimize,
     });
+    exe.addModule("dotenv", dotenv_module);
+    // If you want to modify environment variables.
+    exe.linkSystemLibrary("c");

     // This declares intent for the executable to be installed into the
     // standard location when the user invokes the "install" step (the default

MIT License Copyright (c) 2023, Hanaasagi