env_logger

log thường được sử dụng với env_logger để cấu hình logging thông qua biến môi trường.

Mặc định, env_logger ghi log ra stderr.

File: Cargo.toml

[dependencies]
log = "0.4.0"
env_logger = "0.8.4"

Ví dụ:

File: src/main.rs

fn main() {
  env_logger::init();

  info!("starting up");
  error!("this is error!");
  debug!("this is debug {}!", "message");
}
$ RUST_LOG=error cargo run
[2022-07-11T02:12:24Z ERROR main] this is error

$ RUST_LOG=info cargo run
[2022-07-11T02:12:24Z INFO main] starting up
[2022-07-11T02:12:24Z ERROR main] this is error

$ RUST_LOG=debug cargo run
[2022-07-11T02:12:24Z INFO main] starting up
[2022-07-11T02:12:24Z ERROR main] this is error
[2022-07-11T02:12:24Z DEBUG main] this is debug message!

Filter log theo module name:

$ RUST_LOG=main=info cargo run
[2022-07-11T02:12:24Z INFO main] starting up
[2022-07-11T02:12:24Z ERROR main] this is error

Hiện mọi log level cho module main:

$ RUST_LOG=main cargo run
[2022-07-11T02:12:24Z INFO main] starting up
[2022-07-11T02:12:24Z ERROR main] this is error
[2022-07-11T02:12:24Z DEBUG main] this is debug message!

References