Struct env_logger::Env

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pub struct Env<'a> { /* private fields */ }

Expand description

Set of environment variables to configure from.

§Default environment variables

By default, the Env will read the following environment variables:

RUST_LOG: the level filter
RUST_LOG_STYLE: whether or not to print styles with records.

These sources can be configured using the builder methods on Env.

Implementations§

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impl<'a> Env<'a>

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pub fn new() -> Self

Get a default set of environment variables.

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pub fn filter<E>(self, filter_env: E) -> Self
where E: Into<Cow<'a, str>>,

Specify an environment variable to read the filter from.

Examples found in repository ?

examples/custom_default_format.rs (line 26)

fn init_logger() {
    let env = Env::default()
        .filter("MY_LOG_LEVEL")
        .write_style("MY_LOG_STYLE");

    Builder::from_env(env)
        .format_level(false)
        .format_timestamp_nanos()
        .init();
}

More examples

Hide additional examples

examples/custom_format.rs (line 28)

    fn init_logger() {
        let env = Env::default()
            .filter("MY_LOG_LEVEL")
            .write_style("MY_LOG_STYLE");

        Builder::from_env(env)
            .format(|buf, record| {
                // We are reusing `anstyle` but there are `anstyle-*` crates to adapt it to your
                // preferred styling crate.
                let warn_style = buf.default_level_style(log::Level::Warn);
                let timestamp = buf.timestamp();

                writeln!(
                    buf,
                    "My formatted log ({timestamp}): {warn_style}{}{warn_style:#}",
                    record.args()
                )
            })
            .init();
    }

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pub fn filter_or<E, V>(self, filter_env: E, default: V) -> Self
where E: Into<Cow<'a, str>>, V: Into<Cow<'a, str>>,

Specify an environment variable to read the filter from.

If the variable is not set, the default value will be used.

Examples found in repository ?

examples/default.rs (line 27)

fn main() {
    // The `Env` lets us tweak what the environment
    // variables to read are and what the default
    // value is if they're missing
    let env = Env::default()
        .filter_or("MY_LOG_LEVEL", "trace")
        .write_style_or("MY_LOG_STYLE", "always");

    env_logger::init_from_env(env);

    trace!("some trace log");
    debug!("some debug log");
    info!("some information log");
    warn!("some warning log");
    error!("some error log");
}

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pub fn default_filter_or<V>(self, default: V) -> Self
where V: Into<Cow<'a, str>>,

Use the default environment variable to read the filter from.

If the variable is not set, the default value will be used.

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pub fn write_style<E>(self, write_style_env: E) -> Self
where E: Into<Cow<'a, str>>,

Specify an environment variable to read the style from.

Examples found in repository ?

examples/custom_default_format.rs (line 27)

fn init_logger() {
    let env = Env::default()
        .filter("MY_LOG_LEVEL")
        .write_style("MY_LOG_STYLE");

    Builder::from_env(env)
        .format_level(false)
        .format_timestamp_nanos()
        .init();
}

More examples

Hide additional examples

examples/custom_format.rs (line 29)

    fn init_logger() {
        let env = Env::default()
            .filter("MY_LOG_LEVEL")
            .write_style("MY_LOG_STYLE");

        Builder::from_env(env)
            .format(|buf, record| {
                // We are reusing `anstyle` but there are `anstyle-*` crates to adapt it to your
                // preferred styling crate.
                let warn_style = buf.default_level_style(log::Level::Warn);
                let timestamp = buf.timestamp();

                writeln!(
                    buf,
                    "My formatted log ({timestamp}): {warn_style}{}{warn_style:#}",
                    record.args()
                )
            })
            .init();
    }

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pub fn write_style_or<E, V>(self, write_style_env: E, default: V) -> Self
where E: Into<Cow<'a, str>>, V: Into<Cow<'a, str>>,

Specify an environment variable to read the style from.

If the variable is not set, the default value will be used.

Examples found in repository ?

examples/default.rs (line 28)

fn main() {
    // The `Env` lets us tweak what the environment
    // variables to read are and what the default
    // value is if they're missing
    let env = Env::default()
        .filter_or("MY_LOG_LEVEL", "trace")
        .write_style_or("MY_LOG_STYLE", "always");

    env_logger::init_from_env(env);

    trace!("some trace log");
    debug!("some debug log");
    info!("some information log");
    warn!("some warning log");
    error!("some error log");
}