Hello World

Using the console! macro from the stylus_sdk allows you to print output to the terminal for debugging purposes. To view the output, you'll need to run a local Stylus dev node as described in the Arbitrum docs and set the debug feature flag as shown in line 7 of the Cargo.toml file below.

The console! macro works similar to the built-in println! macro that comes with Rust.

Examples

// Out: Stylus says: 'hello there!'
console!("hello there!");
// Out: Stylus says: 'format some arguments'
console!("format {} arguments", "some");

let local_variable = "Stylus";
// Out: Stylus says: 'Stylus is awesome!'
console!("{local_variable} is awesome!");
// Out: Stylus says: 'When will you try out Stylus?'
console!("When will you try out {}?", local_variable);

src/main.rs

#![no_main]
#![no_std]
extern crate alloc;

#[global_allocator]
static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
use alloc::vec::Vec;

use stylus_sdk::{console, stylus_proc::entrypoint, ArbResult};

#[entrypoint]
fn user_main(_input: Vec<u8>) -> ArbResult {
    // Will print 'Stylus says: Hello Stylus!' on your local dev node
    // Be sure to add "debug" feature flag to your Cargo.toml file as
    // shown below.
    console!("Hello Stylus!");

    Ok(Vec::new())
}

Cargo.toml

[package]
name = "bytes_in_bytes_out"
version = "0.1.0"
edition = "2021"

[dependencies]
stylus-sdk = { version = "0.4.2", features = ["debug"] }
wee_alloc = "0.4.5"

[features]
export-abi = ["stylus-sdk/export-abi"]

[profile.release]
codegen-units = 1
strip = true
lto = true
panic = "abort"
opt-level = "s"

[workspace]