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/*!
Example usage of `fern` with the `syslog` crate.
Be sure to depend on `syslog` and the `syslog` feature in `Cargo.toml`:
```toml
[dependencies]
fern = { version = "0.5", features = ["syslog-3"] }]
syslog = "3.3"
```
To use `syslog`, simply create the log you want, and pass it into `Dispatch::chain`:
```no_run
extern crate fern;
extern crate syslog;
# fn setup_logging() -> Result<(), fern::InitError> {
fern::Dispatch::new()
.chain(syslog::unix(syslog::Facility::LOG_USER)?)
.apply()?;
# Ok(())
# }
# fn main() { setup_logging().ok(); }
```
One thing with `syslog` is that you don't generally want to apply any log formatting. The system logger will handle
that for you, however you may want to format messages if you additionally send them to stdout. Fortunately, fern makes
this easy:
```no_run
# extern crate fern;
# extern crate log;
# extern crate syslog;
#
# fn setup_logging() -> Result<(), fern::InitError> {
// top level config
fern::Dispatch::new()
.chain(
// console config
fern::Dispatch::new()
.level(log::LevelFilter::Debug)
.format(move |out, message, record| {
out.finish(format_args!(
"[{}] {}",
record.level(),
message,
))
})
.chain(std::io::stdout())
)
.chain(
// syslog config
fern::Dispatch::new()
.level(log::LevelFilter::Info)
.chain(syslog::unix(syslog::Facility::LOG_USER)?)
)
.apply()?;
# Ok(())
# }
# fn main() { setup_logging().ok(); }
```
With this, all info and above messages will be sent to the syslog with no formatting, and
the messages sent to the console will still look nice as usual.
---
One last pattern you might want to know: creating a log target which must be explicitly mentioned
in order to work.
```no_run
# extern crate fern;
# extern crate log;
# extern crate syslog;
#
# fn setup_logging() -> Result<(), fern::InitError> {
fern::Dispatch::new()
// by default only accept warning messages from libraries so as not to spam
.level(log::LevelFilter::Warn)
// but accept Info if we explicitly mention it
.level_for("explicit-syslog", log::LevelFilter::Debug)
.chain(syslog::unix(syslog::Facility::LOG_USER)?)
.apply()?;
# Ok(())
# }
# fn main() { setup_logging().ok(); }
```
With this configuration, only warning messages will get through by default, and since 'explicit-syslog'
is not the name of the crate, we can only send info / debug messages if we do so explicitly:
```no_run
# #[macro_use]
# extern crate log;
# fn main() {
debug!("this won't get through");
info!("neither will this"); // especially if this is a library you depend on.
warn!("this will!");
info!(target: "explicit-syslog", "this will also show up!");
# }
```
*/