[−][src]Struct fern::Output

[+] Show declaration

pub struct Output(_);

[−]

Configuration for a logger output.

Methods

`impl Output`[src][−]

`pub fn file<T: Into<Cow<'static, str>>>(file: File, line_sep: T) -> Self`[src][−]

Returns a file logger using a custom separator.

If the default separator of \n is acceptable, an fs::File instance can be passed into Dispatch::chain directly.

fern::Dispatch::new()
    .chain(std::fs::File::create("log")?)

fern::Dispatch::new()
    .chain(fern::log_file("log")?)

Example usage (using fern::log_file):

fern::Dispatch::new()
    .chain(fern::Output::file(fern::log_file("log")?, "\r\n"))

`pub fn writer<T: Into<Cow<'static, str>>>( writer: Box<dyn Write + Send>, line_sep: T ) -> Self`[src][−]

Returns a logger using arbitrary write object and custom separator.

If the default separator of \n is acceptable, an Box<Write + Send> instance can be passed into Dispatch::chain directly.

// Anything implementing 'Write' works.
let mut writer = std::io::Cursor::new(Vec::<u8>::new());

fern::Dispatch::new()
    // as long as we explicitly cast into a type-erased Box
    .chain(Box::new(writer) as Box<std::io::Write + Send>)

Example usage:

let writer = Box::new(std::io::Cursor::new(Vec::<u8>::new()));

fern::Dispatch::new()
    .chain(fern::Output::writer(writer, "\r\n"))

`pub fn stdout<T: Into<Cow<'static, str>>>(line_sep: T) -> Self`[src][−]

Returns an stdout logger using a custom separator.

If the default separator of \n is acceptable, an io::Stdout instance can be passed into Dispatch::chain() directly.

fern::Dispatch::new()
    .chain(std::io::stdout())

Example usage:

fern::Dispatch::new()
    // some unix tools use null bytes as message terminators so
    // newlines in messages can be treated differently.
    .chain(fern::Output::stdout("\0"))

`pub fn stderr<T: Into<Cow<'static, str>>>(line_sep: T) -> Self`[src][−]

Returns an stderr logger using a custom separator.

If the default separator of \n is acceptable, an io::Stderr instance can be passed into Dispatch::chain() directly.

fern::Dispatch::new()
    .chain(std::io::stderr())

Example usage:

fern::Dispatch::new()
    .chain(fern::Output::stderr("\n\n\n"))

`pub fn sender<T: Into<Cow<'static, str>>>( sender: Sender<String>, line_sep: T ) -> Self`[src][−]

Returns a mpsc::Sender logger using a custom separator.

If the default separator of \n is acceptable, an mpsc::Sender<String> instance can be passed into Dispatch:: chain() directly.

Each log message will be suffixed with the separator, then sent as a single String to the given sender.

use std::sync::mpsc::channel;

let (tx, rx) = channel();
fern::Dispatch::new()
    .chain(tx)

`pub fn call<F>(func: F) -> Self where F: Fn(&Record) + Sync + Send + 'static,` [src][−]

Returns a logger which simply calls the given function with each message.

The function will be called inline in the thread the log occurs on.

Example usage:

fern::Dispatch::new()
    .chain(fern::Output::call(|record| {
        // this is mundane, but you can do anything here.
        println!("{}", record.args());
    }))

Trait Implementations

`impl From<Dispatch> for Output`[src][+]

`fn from(log: Dispatch) -> Self`[src][−]

Creates an output logger forwarding all messages to the dispatch.

`impl From<Box<dyn Log + 'static>> for Output`[src][+]

`fn from(log: Box<dyn Log>) -> Self`[src][−]

Creates an output logger forwarding all messages to the custom logger.

`impl From<&'static (dyn Log + 'static)> for Output`[src][+]

`fn from(log: &'static dyn Log) -> Self`[src][−]

Creates an output logger forwarding all messages to the custom logger.

`impl From<File> for Output`[src][+]

`fn from(file: File) -> Self`[src][−]

Creates an output logger which writes all messages to the file with \n as the separator.

File writes are buffered and flushed once per log record.

`impl From<Box<dyn Write + 'static + Send>> for Output`[src][+]

`fn from(writer: Box<dyn Write + Send>) -> Self`[src][−]

Creates an output logger which writes all messages to the writer with \n as the separator.

This does no buffering and it is up to the writer to do buffering as needed (eg. wrap it in BufWriter). However, flush is called after each log record.