Struct Formatter

pub struct Formatter { /* private fields */ }

A formatter to write logs into.

Formatter implements the standard Write trait for writing log records. It also supports terminal colors, through the style method.

Examples

Use the writeln macro to format a log record. An instance of a Formatter is passed to an env_logger format as buf:

use std::io::Write;

let mut builder = env_logger::Builder::new();

builder.format(|buf, record| writeln!(buf, "{}: {}", record.level(), record.args()));

Implementations

impl Formatter

pub fn timestamp(&self) -> Timestamp

Get a Timestamp for the current date and time in UTC.

Examples

Include the current timestamp with the log record:

use std::io::Write;

let mut builder = env_logger::Builder::new();

builder.format(|buf, record| {
    let ts = buf.timestamp();

    writeln!(buf, "{}: {}: {}", ts, record.level(), record.args())
});

pub fn timestamp_seconds(&self) -> Timestamp

Get a Timestamp for the current date and time in UTC with full second precision.

pub fn timestamp_millis(&self) -> Timestamp

Get a Timestamp for the current date and time in UTC with millisecond precision.

pub fn timestamp_micros(&self) -> Timestamp

Get a Timestamp for the current date and time in UTC with microsecond precision.

pub fn timestamp_nanos(&self) -> Timestamp

Get a Timestamp for the current date and time in UTC with nanosecond precision.

impl Formatter

pub fn style(&self) -> Style

Begin a new Style.

Examples

Create a bold, red colored style and use it to print the log level:

use std::io::Write;
use env_logger::fmt::Color;

let mut builder = env_logger::Builder::new();

builder.format(|buf, record| {
    let mut level_style = buf.style();

    level_style.set_color(Color::Red).set_bold(true);

    writeln!(buf, "{}: {}",
        level_style.value(record.level()),
        record.args())
});

pub fn default_level_style(&self, level: Level) -> Style

Get the default Style for the given level.

The style can be used to print other values besides the level.

pub fn default_styled_level(&self, level: Level) -> StyledValue<'static, Level>

Get a printable Style for the given level.

The style can only be used to print the level.

Trait Implementations

impl Debug for Formatter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Write for Formatter

fn write(&mut self, buf: &[u8]) -> Result<usize>

Writes a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.