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< h1 id = "配置日志" > < a class = "header" href = "#配置日志" > 配置日志< / a > < / h1 >
< h3 id = "为每个模块开启独立的日志级别" > < a class = "header" href = "#为每个模块开启独立的日志级别" > 为每个模块开启独立的日志级别< / a > < / h3 >
< p > 下面代码创建了模块 < code > foo< / code > 和嵌套模块 < code > foo::bar< / code > ，并通过 < a href = "https://docs.rs/env_logger/*/env_logger/#enabling-logging" > RUST_LOG< / a > 环境变量对各自的日志级别进行了控制。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > mod foo {
mod bar {
pub fn run() {
log::warn!(" [bar] warn" );
log::info!(" [bar] info" );
log::debug!(" [bar] debug" );
}
}
pub fn run() {
log::warn!(" [foo] warn" );
log::info!(" [foo] info" );
log::debug!(" [foo] debug" );
bar::run();
}
}
fn main() {
env_logger::init();
log::warn!(" [root] warn" );
log::info!(" [root] info" );
log::debug!(" [root] debug" );
foo::run();
}
< / code > < / pre > < / pre >
< p > 要让环境变量生效，首先需要通过 < code > env_logger::init()< / code > 开启相关的支持。然后通过以下命令来运行程序:< / p >
< pre > < code class = "language-shell" > RUST_LOG=" warn,test::foo=info,test::foo::bar=debug" ./test
< / code > < / pre >
< p > 此时的默认日志级别被设置为 < code > warn< / code > ，但我们还将 < code > foo< / code > 模块级别设置为 < code > info< / code > , < code > foo::bar< / code > 模块日志级别设置为 < code > debug< / code > 。< / p >
< pre > < code class = "language-bash" > WARN:test: [root] warn
WARN:test::foo: [foo] warn
INFO:test::foo: [foo] info
WARN:test::foo::bar: [bar] warn
INFO:test::foo::bar: [bar] info
DEBUG:test::foo::bar: [bar] debug
< / code > < / pre >
< h3 id = "使用自定义环境变量来设置日志" > < a class = "header" href = "#使用自定义环境变量来设置日志" > 使用自定义环境变量来设置日志< / a > < / h3 >
< p > < a href = "https://docs.rs/env_logger/*/env_logger/struct.Builder.html" > Builder< / a > 将对日志进行配置，以下代码使用 < code > MY_APP_LOG< / code > 来替代 < code > RUST_LOG< / code > 环境变量:< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > use std::env;
use env_logger::Builder;
fn main() {
Builder::new()
.parse(& env::var(" MY_APP_LOG" ).unwrap_or_default())
.init();
log::info!(" informational message" );
log::warn!(" warning message" );
log::error!(" this is an error {}" , " message" );
}
< / code > < / pre > < / pre >
< h3 id = "在日志中包含时间戳" > < a class = "header" href = "#在日志中包含时间戳" > 在日志中包含时间戳< / a > < / h3 >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > use std::io::Write;
use chrono::Local;
use env_logger::Builder;
use log::LevelFilter;
fn main() {
Builder::new()
.format(|buf, record| {
writeln!(buf,
" {} [{}] - {}" ,
Local::now().format(" %Y-%m-%dT%H:%M:%S" ),
record.level(),
record.args()
)
})
.filter(None, LevelFilter::Info)
.init();
log::warn!(" warn" );
log::info!(" info" );
log::debug!(" debug" );
}
< / code > < / pre > < / pre >
< p > 以下是 < code > stderr< / code > 的输出:< / p >
< pre > < code class = "language-shell" > 2022-03-22T21:57:06 [WARN] - warn
2022-03-22T21:57:06 [INFO] - info
< / code > < / pre >
< h3 id = "将日志输出到指定文件" > < a class = "header" href = "#将日志输出到指定文件" > 将日志输出到指定文件< / a > < / h3 >
< p > < a href = "https://docs.rs/log4rs/" > log4rs< / a > 可以帮我们将日志输出指定的位置，它可以使用外部 YAML 文件或 < code > builder< / code > 的方式进行配置。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > < span class = "boring" > use error_chain::error_chain;
< / span >
use log::LevelFilter;
use log4rs::append::file::FileAppender;
use log4rs::encode::pattern::PatternEncoder;
use log4rs::config::{Appender, Config, Root};
< span class = "boring" > error_chain! {
< / span > < span class = "boring" > foreign_links {
< / span > < span class = "boring" > Io(std::io::Error);
< / span > < span class = "boring" > LogConfig(log4rs::config::Errors);
< / span > < span class = "boring" > SetLogger(log::SetLoggerError);
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span >
fn main() -> Result< ()> {
// 创建日志配置，并指定输出的位置
let logfile = FileAppender::builder()
// 编码模式的详情参见: https://docs.rs/log4rs/1.0.0/log4rs/encode/pattern/index.html
.encoder(Box::new(PatternEncoder::new(" {l} - {m}\n" )))
.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(())
}
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