Default log level for (pretty_)env_logger

main.rs

extern crate env_logger;
extern crate log;

use std::env;

fn main() {
    // By default, log all `info!` messages and higher, in all modules and crates.
    // Can be overridden by specifying the `RUST_LOG` environment variable.
    if env::var_os("RUST_LOG").is_none() {
        env_logger::Builder::from_default_env()
            .filter(None, log::LevelFilter::Info)
            .init();
    } else {
        env_logger::init();
    }
    
    info!("shows up without having to set RUST_LOG");
    debug!("only shows up when RUST_LOG=debug is set");
    
    // Or: Log *all levels* for the current crate (`module_path!()` will expand to the crate name)
    if env::var_os("RUST_LOG").is_none() {
        pretty_env_logger::formatted_builder()
            .unwrap()
            .filter(Some(module_path!()), log::LevelFilter::Trace)
            .init();
    } else {
        pretty_env_logger::init();
    }
}