Rust - Load a TOML File

Intro

In this post, I'll show you how to load a TOML file in Rust using the toml crate.

Software

The following software was used in this post.

Rust - 1.58.1

Dependencies

Add the toml crate to Cargo.toml.

Cargo.toml

[dependencies]
toml = "0.5.8"
serde = { version = "1.0.136", features = ["derive"] }

TOML File

Create a TOML file named test.toml with the following content.

test.toml

[database]
host = "localhost"
port = 5432
username = "admin"
password = "password"

[server]
host = "0.0.0.0"
port = 8080

Lets Get Rusty

Create a struct that mirrors the TOML file structure. The Deserialize macro is used to deserialize the TOML file into the struct.

main.rs

use serde::Deserialize;
use std::fs;

#[derive(Debug, Deserialize)]
struct Config {
    database: Database,
    server: Server,
}

#[derive(Debug, Deserialize)]
struct Database {
    host: String,
    port: u16,
    username: String,
    password: String,
}

#[derive(Debug, Deserialize)]
struct Server {
    host: String,
    port: u16,
}

fn main() {
    // Read the TOML file
    let config_str = fs::read_to_string("test.toml").expect("Failed to read file");

    // Parse the TOML file
    let config: Config = toml::from_str(&config_str).expect("Failed to parse TOML");

    // Print the config
    println!("{:#?}", config);
}

Run the program.

cargo run

# output

Config {
    database: Database {
        host: "localhost",
        port: 5432,
        username: "admin",
        password: "password",
    },
    server: Server {
        host: "0.0.0.0",
        port: 8080,
    },
}

The TOML file has been successfully loaded into a Rust struct.