Struct LoggerBuilder 

pub struct LoggerBuilder { /* private fields */ }

Builder for configuring a Logger with custom appenders.

Construct one with Logger::builder, add appenders, then call LoggerBuilder::build to get the logger or LoggerBuilder::init to install it as the global logger.

Implementations

impl LoggerBuilder

pub fn level(self, level: LogLevel) -> Self

Set the log level. Defaults to the level passed to Logger::builder.

pub fn appender(self, appender: Box<dyn Appender>) -> Self

Add an appender. May be called multiple times to add several appenders.

Examples found in repository

examples/custom_appender.rs (line 49)

fn main() {
    let collector = VecAppender::new(Arc::new(KeyValueLayout));

    // Build a logger with a custom appender and install it as the global logger.
    Logger::builder(LogLevel::Info)
        .appender(Box::new(collector.clone()))
        .init();

    log4rc::info!("Hello, appender!");
    log4rc::debug!("This is filtered out at Info level");
    log4rc::error!("Something went wrong");

    // Only the Info and Error messages made it through the level filter.
    for line in collector.messages() {
        println!("captured: {line}");
    }
}

examples/file_appender.rs (line 12)

fn main() {
    let log_path = std::env::temp_dir().join("log4rc-file-appender.log");

    Logger::builder(LogLevel::Info)
        .appender(Box::new(ConsoleAppender::new(Box::new(SimpleLayout))))
        .appender(Box::new(
            FileAppender::open(&log_path, Box::new(SimpleLayout))
                .expect("failed to open log file"),
        ))
        .init();

    log4rc::info!("Writing to console and file");
    log4rc::error!("An error also goes to both");
    log4rc::debug!("Filtered out at Info level");

    // Read the file back to prove the messages were written to disk.
    let mut contents = String::new();
    std::fs::File::open(&log_path)
        .expect("failed to reopen log file")
        .read_to_string(&mut contents)
        .expect("failed to read log file");

    println!("\n--- Contents of {} ---", log_path.display());
    print!("{contents}");
    let _ = std::fs::remove_file(&log_path);
}

examples/rolling_file_appender.rs (lines 16-23)

fn main() {
    let dir = std::env::temp_dir();
    let prefix = format!("log4rc-rolling-{}", std::process::id());
    let log_path = dir.join(format!("{prefix}.log"));

    Logger::builder(LogLevel::Info)
        .appender(Box::new(
            FileAppender::builder(&log_path, Box::new(SimpleLayout))
                .max_size(100) // tiny limit so a few messages trigger a roll
                .max_files(3) // keep only the 3 newest rotated files
                .compressed() // gzip rotated files
                .build()
                .expect("failed to open log file"),
        ))
        .init();

    for i in 0..10 {
        log4rc::info!("This is message number {i:02} with some padding to grow the file");
    }

    // List the active file plus any rotated siblings.
    let mut files: Vec<_> = std::fs::read_dir(&dir)
        .unwrap()
        .flatten()
        .map(|e| e.path())
        .filter(|p| {
            p.file_name()
                .and_then(|n| n.to_str())
                .is_some_and(|n| n.starts_with(&prefix))
        })
        .collect();
    files.sort();

    println!("--- Log files ---");
    let mut total_lines = 0;
    for path in &files {
        let contents = if path.to_string_lossy().ends_with(".gz") {
            let mut contents = String::new();
            let file = std::fs::File::open(path).expect("failed to open rotated file");
            GzDecoder::new(file)
                .read_to_string(&mut contents)
                .expect("failed to decompress rotated file");
            contents
        } else {
            std::fs::read_to_string(path).expect("failed to read log file")
        };
        let lines = contents.lines().count();
        total_lines += lines;
        println!("{} ({} lines):", path.display(), lines);
    }
    println!("total lines across files: {total_lines}");

    for path in files {
        let _ = std::fs::remove_file(path);
    }
}

pub fn build(self) -> Logger

Build the configured logger.

pub fn init(self)

Build the logger and install it as the global logger, replacing any previously configured logger.

Examples found in repository

examples/custom_appender.rs (line 50)

fn main() {
    let collector = VecAppender::new(Arc::new(KeyValueLayout));

    // Build a logger with a custom appender and install it as the global logger.
    Logger::builder(LogLevel::Info)
        .appender(Box::new(collector.clone()))
        .init();

    log4rc::info!("Hello, appender!");
    log4rc::debug!("This is filtered out at Info level");
    log4rc::error!("Something went wrong");

    // Only the Info and Error messages made it through the level filter.
    for line in collector.messages() {
        println!("captured: {line}");
    }
}

examples/file_appender.rs (line 17)

fn main() {
    let log_path = std::env::temp_dir().join("log4rc-file-appender.log");

    Logger::builder(LogLevel::Info)
        .appender(Box::new(ConsoleAppender::new(Box::new(SimpleLayout))))
        .appender(Box::new(
            FileAppender::open(&log_path, Box::new(SimpleLayout))
                .expect("failed to open log file"),
        ))
        .init();

    log4rc::info!("Writing to console and file");
    log4rc::error!("An error also goes to both");
    log4rc::debug!("Filtered out at Info level");

    // Read the file back to prove the messages were written to disk.
    let mut contents = String::new();
    std::fs::File::open(&log_path)
        .expect("failed to reopen log file")
        .read_to_string(&mut contents)
        .expect("failed to read log file");

    println!("\n--- Contents of {} ---", log_path.display());
    print!("{contents}");
    let _ = std::fs::remove_file(&log_path);
}

examples/rolling_file_appender.rs (line 24)

fn main() {
    let dir = std::env::temp_dir();
    let prefix = format!("log4rc-rolling-{}", std::process::id());
    let log_path = dir.join(format!("{prefix}.log"));

    Logger::builder(LogLevel::Info)
        .appender(Box::new(
            FileAppender::builder(&log_path, Box::new(SimpleLayout))
                .max_size(100) // tiny limit so a few messages trigger a roll
                .max_files(3) // keep only the 3 newest rotated files
                .compressed() // gzip rotated files
                .build()
                .expect("failed to open log file"),
        ))
        .init();

    for i in 0..10 {
        log4rc::info!("This is message number {i:02} with some padding to grow the file");
    }

    // List the active file plus any rotated siblings.
    let mut files: Vec<_> = std::fs::read_dir(&dir)
        .unwrap()
        .flatten()
        .map(|e| e.path())
        .filter(|p| {
            p.file_name()
                .and_then(|n| n.to_str())
                .is_some_and(|n| n.starts_with(&prefix))
        })
        .collect();
    files.sort();

    println!("--- Log files ---");
    let mut total_lines = 0;
    for path in &files {
        let contents = if path.to_string_lossy().ends_with(".gz") {
            let mut contents = String::new();
            let file = std::fs::File::open(path).expect("failed to open rotated file");
            GzDecoder::new(file)
                .read_to_string(&mut contents)
                .expect("failed to decompress rotated file");
            contents
        } else {
            std::fs::read_to_string(path).expect("failed to read log file")
        };
        let lines = contents.lines().count();
        total_lines += lines;
        println!("{} ({} lines):", path.display(), lines);
    }
    println!("total lines across files: {total_lines}");

    for path in files {
        let _ = std::fs::remove_file(path);
    }
}