Struct LogWriter

pub struct LogWriter { /* private fields */ }

Wrapper around a Write-capable type that filters the types of messages that are written to it.

This can be used to customize the output source of the HumanLogger.

Examples

A logger that writes to stdout only, instead of mixed stdout/stderr (like usual).

use humanlog::{ColourChoice, DebugMode, HumanLogger, LogWriter};
use log::{debug, info, error, Level};
 
let logger: LogWriter = LogWriter::new(std::io::stdout(), ColourChoice::Auto, vec![ Level::Error, Level::Warn, Level::Info, Level::Debug, Level::Trace ], "stdout");
if let Err(err) = HumanLogger::new(vec![ logger ], DebugMode::Debug).init() {
    eprintln!("WARNING: Failed to initialize logger: {err} (no logging enabled for this session)");
}

A logger that writes to a file instead of stdout/stderr.

use std::fs::File;
use humanlog::{ColourChoice, DebugMode, HumanLogger, LogWriter};
use log::{debug, info, error, Level};
 
// Open a file
match File::create("output.log") {
    Ok(handle) => {
        // Use that to create a writer that receives everything
        let logger: LogWriter = LogWriter::new(handle, ColourChoice::No, vec![ Level::Error, Level::Warn, Level::Info, Level::Debug, Level::Trace ], "file");
        if let Err(err) = HumanLogger::new(vec![ logger ], DebugMode::Debug).init() {
            eprintln!("WARNING: Failed to initialize logger: {err} (no logging enabled for this session)");
        }
    },

    Err(err) => {
        eprintln!("WARNING: Failed to initialize logger: Failed to create file 'output.log': {err} (no logging enabled for this session)");
    },
}

A logger that writes to a file in addition to the standard stdout/stderr logging.

use std::fs::File;
use humanlog::{ColourChoice, DebugMode, HumanLogger, LogWriter};
use log::{debug, info, error, Level};
 
// Open a file
match File::create("output.log") {
    Ok(handle) => {
        // Create three LogWriters: one per output stream
        let stdout_logger: LogWriter = LogWriter::stdout();
        let stderr_logger: LogWriter = LogWriter::stderr();
        // Note the repeated levels; the logger will simply log to all LogWriters that want that particular level
        let file_logger: LogWriter = LogWriter::new(handle, ColourChoice::No, vec![ Level::Error, Level::Warn, Level::Info, Level::Debug, Level::Trace ], "file");
 
        // Finally, we put it all in one logger
        if let Err(err) = HumanLogger::new(vec![ stdout_logger, stderr_logger, file_logger ], DebugMode::Debug).init() {
            eprintln!("WARNING: Failed to initialize logger: {err} (no logging enabled for this session)");
        }
    },
 
    Err(err) => {
        eprintln!("WARNING: Failed to initialize logger: Failed to create file 'output.log': {err} (no logging enabled for this session)");
    },
}

Implementations

impl LogWriter

pub fn stdout() -> Self

Default constructor for the LogWriter that initializes it for stdout.

By default, will use automatic colour selection and only logs trace, debug and info-messages.

Returns

A new LogWriter instance that can be used to log to stdout.

Examples

use humanlog::{DebugMode, HumanLogger, LogWriter};
 
// Will emulate the default behaviour of writing `Level::Error` and `Level::Warn` to stderr, the rest to stdout.
if let Err(err) = HumanLogger::new(vec![ LogWriter::stdout(), LogWriter::stderr() ], DebugMode::Debug).init() {
    eprintln!("WARNING: Failed to initialize logger: {err} (no logging enabled for this session)");
}

pub fn stderr() -> Self

Default constructor for the LogWriter that initializes it for stderr.

By default, will use automatic colour selection and only logs warning and error message.

Returns

A new LogWriter instance that can be used to log to stderr.

Examples

use humanlog::{DebugMode, HumanLogger, LogWriter};
 
// Will emulate the default behaviour of writing `Level::Error` and `Level::Warn` to stderr, the rest to stdout.
if let Err(err) = HumanLogger::new(vec![ LogWriter::stdout(), LogWriter::stderr() ], DebugMode::Debug).init() {
    eprintln!("WARNING: Failed to initialize logger: {err} (no logging enabled for this session)");
}

pub fn new( writer: impl 'static + Send + Sync + Write, colour: ColourChoice, filter: impl Into<Vec<Level>>, label: impl Into<String>, ) -> Self

Constructor for the LogWriter that wraps it around the given Writer.

Arguments

• writer: The handle or other object that implement Write and we will write to.
• colour_choice: Whether to enable ANSI colours for this file or not.
• filter: The list of Levels that are only allowed to be written to this writer.
• label: Some description of the writer for debugging purposes.

Returns

A new LogWriter instance that wraps around the given writer.

Examples

use humanlog::{ColourChoice, DebugMode, HumanLogger, LogWriter};
use log::Level;
 
// Will only ever write to stdout, regardless of the log type
let logger: LogWriter = LogWriter::new(std::io::stdout(), ColourChoice::Auto, vec![ Level::Error, Level::Warn, Level::Info, Level::Debug, Level::Trace ], "stdout");
if let Err(err) = HumanLogger::new(vec![ logger ], DebugMode::Debug).init() {
    eprintln!("WARNING: Failed to initialize logger: {err} (no logging enabled for this session)");
}