Best way to enable ansi formatting for terminal output only

[aaronriekenberg]

I have an application using

tracing_subscriber::fmt::init();

Have noticed by default this enables ansi formatting, which has formatting issues when redirecting output to a file or running as a systemd service.

I came up with the below function to do basically the equivalent of above but only enable ansi formatting if std::io::stdout().is_terminal() is true. This is a new feature in rust 1.70.0: https://blog.rust-lang.org/2023/06/01/Rust-1.70.0.html#isterminal

Is there a simpler way to do what is below? Could something similar to below be considered for the default tracing_subscriber::fmt::init() to enable ansi formatting only if outputting to a terminal?

Thanks!

fn initialize_tracing_subscriber() {
    use tracing_subscriber::{filter::LevelFilter, fmt, prelude::*, EnvFilter};

    use std::io::IsTerminal;

    let use_ansi = std::io::stdout().is_terminal();

    let env_filter = EnvFilter::builder()
        .with_default_directive(LevelFilter::INFO.into())
        .from_env_lossy();

    tracing_subscriber::registry()
        .with(env_filter)
        .with(fmt::layer().with_ansi(use_ansi))
        .init();
}

[davidbarsky]

Sorry for the delay. What you wrote is generally the correct approach, and while we'd like to make tracing_subscriber::fmt call std::io::stdout().is_terminal(), we can't due to our current MSRV.