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// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! A simple logger configured via environment variables which writes //! to stdout or stderr, for use with the logging facade exposed by the //! [`log` crate][log-crate-url]. //! //! ## Example //! //! ``` //! #[macro_use] extern crate log; //! extern crate env_logger; //! //! use log::Level; //! //! fn main() { //! env_logger::init(); //! //! debug!("this is a debug {}", "message"); //! error!("this is printed by default"); //! //! if log_enabled!(Level::Info) { //! let x = 3 * 4; // expensive computation //! info!("the answer was: {}", x); //! } //! } //! ``` //! //! Assumes the binary is `main`: //! //! ```{.bash} //! $ RUST_LOG=error ./main //! ERROR: 2017-11-09T02:12:24Z: main: this is printed by default //! ``` //! //! ```{.bash} //! $ RUST_LOG=info ./main //! ERROR: 2017-11-09T02:12:24Z: main: this is printed by default //! INFO: 2017-11-09T02:12:24Z: main: the answer was: 12 //! ``` //! //! ```{.bash} //! $ RUST_LOG=debug ./main //! DEBUG: 2017-11-09T02:12:24Z: main: this is a debug message //! ERROR: 2017-11-09T02:12:24Z: main: this is printed by default //! INFO: 2017-11-09T02:12:24Z: main: the answer was: 12 //! ``` //! //! You can also set the log level on a per module basis: //! //! ```{.bash} //! $ RUST_LOG=main=info ./main //! ERROR: 2017-11-09T02:12:24Z: main: this is printed by default //! INFO: 2017-11-09T02:12:24Z: main: the answer was: 12 //! ``` //! //! And enable all logging: //! //! ```{.bash} //! $ RUST_LOG=main ./main //! DEBUG: 2017-11-09T02:12:24Z: main: this is a debug message //! ERROR: 2017-11-09T02:12:24Z: main: this is printed by default //! INFO: 2017-11-09T02:12:24Z: main: the answer was: 12 //! ``` //! //! See the documentation for the [`log` crate][log-crate-url] for more //! information about its API. //! //! ## Enabling logging //! //! Log levels are controlled on a per-module basis, and by default all logging //! is disabled except for `error!`. Logging is controlled via the `RUST_LOG` //! environment variable. The value of this environment variable is a //! comma-separated list of logging directives. A logging directive is of the //! form: //! //! ```text //! path::to::module=level //! ``` //! //! The path to the module is rooted in the name of the crate it was compiled //! for, so if your program is contained in a file `hello.rs`, for example, to //! turn on logging for this file you would use a value of `RUST_LOG=hello`. //! Furthermore, this path is a prefix-search, so all modules nested in the //! specified module will also have logging enabled. //! //! The actual `level` is optional to specify. If omitted, all logging will //! be enabled. If specified, it must be one of the strings `debug`, `error`, //! `info`, `warn`, or `trace`. //! //! As the log level for a module is optional, the module to enable logging for //! is also optional. If only a `level` is provided, then the global log //! level for all modules is set to this value. //! //! Some examples of valid values of `RUST_LOG` are: //! //! * `hello` turns on all logging for the 'hello' module //! * `info` turns on all info logging //! * `hello=debug` turns on debug logging for 'hello' //! * `hello,std::option` turns on hello, and std's option logging //! * `error,hello=warn` turn on global error logging and also warn for hello //! //! ## Filtering results //! //! A `RUST_LOG` directive may include a regex filter. The syntax is to append `/` //! followed by a regex. Each message is checked against the regex, and is only //! logged if it matches. Note that the matching is done after formatting the //! log string but before adding any logging meta-data. There is a single filter //! for all modules. //! //! Some examples: //! //! * `hello/foo` turns on all logging for the 'hello' module where the log //! message includes 'foo'. //! * `info/f.o` turns on all info logging where the log message includes 'foo', //! 'f1o', 'fao', etc. //! * `hello=debug/foo*foo` turns on debug logging for 'hello' where the log //! message includes 'foofoo' or 'fofoo' or 'fooooooofoo', etc. //! * `error,hello=warn/[0-9]scopes` turn on global error logging and also //! warn for hello. In both cases the log message must include a single digit //! number followed by 'scopes'. //! //! ## Disabling colors //! //! Colors and other styles can be configured with the `RUST_LOG_STYLE` //! environment variable. It accepts the following values: //! //! * `auto` (default) will attempt to print style characters, but don't force the issue. //! If the console isn't available on Windows, or if TERM=dumb, for example, then don't print colors. //! * `always` will always print style characters even if they aren't supported by the terminal. //! This includes emitting ANSI colors on Windows if the console API is unavailable. //! * `never` will never print style characters. //! //! [log-crate-url]: https://docs.rs/log/ #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png", html_favicon_url = "http://www.rust-lang.org/favicon.ico", html_root_url = "https://docs.rs/env_logger/0.5.1")] #![cfg_attr(test, deny(warnings))] // When compiled for the rustc compiler itself we want to make sure that this is // an unstable crate #![cfg_attr(rustbuild, feature(staged_api, rustc_private))] #![cfg_attr(rustbuild, unstable(feature = "rustc_private", issue = "27812"))] #![deny(missing_debug_implementations, missing_docs, warnings)] extern crate log; extern crate termcolor; extern crate chrono; use std::env; use std::borrow::Cow; use std::io::prelude::*; use std::io; use std::mem; use std::cell::RefCell; use log::{Log, LevelFilter, Level, Record, SetLoggerError, Metadata}; pub mod filter; pub mod fmt; pub use self::fmt::{Target, WriteStyle, Color, Formatter}; const DEFAULT_FILTER_ENV: &'static str = "RUST_LOG"; const DEFAULT_WRITE_STYLE_ENV: &'static str = "RUST_LOG_STYLE"; /// Set of environment variables to configure from. /// /// By default, the `Env` will read the following environment variables: /// /// - `RUST_LOG`: the level filter /// - `RUST_LOG_STYLE`: whether or not to print styles with records. /// /// These sources can be configured using the builder methods on `Env`. #[derive(Debug)] pub struct Env<'a> { filter: Cow<'a, str>, write_style: Cow<'a, str>, } /// The env logger. /// /// This struct implements the `Log` trait from the [`log` crate][log-crate-url], /// which allows it to act as a logger. /// /// The [`init()`], [`try_init()`], [`Builder::init()`] and [`Builder::try_init()`] /// methods will each construct a `Logger` and immediately initialize it as the /// default global logger. /// /// If you'd instead need access to the constructed `Logger`, you can use /// the associated [`Builder`] and install it with the /// [`log` crate][log-crate-url] directly. /// /// [log-crate-url]: https://docs.rs/log/ /// [`init()`]: fn.init.html /// [`try_init()`]: fn.try_init.html /// [`Builder::init()`]: struct.Builder.html#method.init /// [`Builder::try_init()`]: struct.Builder.html#method.try_init /// [`Builder`]: struct.Builder.html pub struct Logger { writer: fmt::Writer, filter: filter::Filter, format: Box<Fn(&mut Formatter, &Record) -> io::Result<()> + Sync + Send>, } /// `Builder` acts as builder for initializing a `Logger`. /// /// It can be used to customize the log format, change the environment variable used /// to provide the logging directives and also set the default log level filter. /// /// ## Example /// /// ``` /// #[macro_use] /// extern crate log; /// extern crate env_logger; /// /// use std::env; /// use std::io::Write; /// use log::LevelFilter; /// use env_logger::Builder; /// /// fn main() { /// let mut builder = Builder::new(); /// /// builder.format(|buf, record| writeln!(buf, "{} - {}", record.level(), record.args())) /// .filter(None, LevelFilter::Info); /// /// if let Ok(rust_log) = env::var("RUST_LOG") { /// builder.parse(&rust_log); /// } /// /// builder.init(); /// /// error!("error message"); /// info!("info message"); /// } /// ``` pub struct Builder { filter: filter::Builder, writer: fmt::Builder, format: Box<Fn(&mut Formatter, &Record) -> io::Result<()> + Sync + Send>, } impl Builder { /// Initializes the log builder with defaults. pub fn new() -> Builder { Builder { filter: Default::default(), writer: Default::default(), format: Box::new(|buf, record| { let ts = buf.timestamp(); let level = record.level(); let mut level_style = buf.style(); match level { Level::Trace => level_style.set_color(Color::White), Level::Debug => level_style.set_color(Color::Blue), Level::Info => level_style.set_color(Color::Green), Level::Warn => level_style.set_color(Color::Yellow), Level::Error => level_style.set_color(Color::Red).set_bold(true), }; if let Some(module_path) = record.module_path() { writeln!(buf, "{:>5} {}: {}: {}", level_style.value(level), ts, module_path, record.args()) } else { writeln!(buf, "{:>5} {}: {}", level_style.value(level), ts, record.args()) } }), } } /// Initializes the log builder from the environment. /// /// The variables used to read configuration from can be tweaked before /// passing in. /// /// # Examples /// /// Initialise a logger using the default environment variables: /// /// ``` /// use env_logger::{Builder, Env}; /// /// let mut builder = Builder::from_env(Env::default()); /// builder.init(); /// ``` /// /// Initialise a logger using the `MY_LOG` variable for filtering and /// `MY_LOG_STYLE` for whether or not to write styles: /// /// ``` /// use env_logger::{Builder, Env}; /// /// let env = Env::new().filter("MY_LOG").write_style("MY_LOG_STYLE"); /// /// let mut builder = Builder::from_env(env); /// builder.init(); /// ``` pub fn from_env<'a, E>(env: E) -> Self where E: Into<Env<'a>> { let mut builder = Builder::new(); let env = env.into(); if let Some(s) = env.get_filter() { builder.parse(&s); } if let Some(s) = env.get_write_style() { builder.parse_write_style(&s); } builder } /// Adds filters to the logger. /// /// The given module (if any) will log at most the specified level provided. /// If no module is provided then the filter will apply to all log messages. pub fn filter(&mut self, module: Option<&str>, level: LevelFilter) -> &mut Self { self.filter.filter(module, level); self } /// Sets the format function for formatting the log output. /// /// This function is called on each record logged and should format the /// log record and output it to the given [`Formatter`]. /// /// The format function is expected to output the string directly to the /// `Formatter` so that implementations can use the [`std::fmt`] macros /// to format and output without intermediate heap allocations. The default /// `env_logger` formatter takes advantage of this. /// /// [`Formatter`]: fmt/struct.Formatter.html /// [`String`]: https://doc.rust-lang.org/stable/std/string/struct.String.html /// [`std::fmt`]: https://doc.rust-lang.org/std/fmt/index.html pub fn format<F: 'static>(&mut self, format: F) -> &mut Self where F: Fn(&mut Formatter, &Record) -> io::Result<()> + Sync + Send { self.format = Box::new(format); self } /// Sets the target for the log output. /// /// Env logger can log to either stdout or stderr. The default is stderr. pub fn target(&mut self, target: fmt::Target) -> &mut Self { self.writer.target(target); self } /// Sets whether or not styles will be written. /// /// This can be useful in environments that don't support control characters /// for setting colors. pub fn write_style(&mut self, write_style: fmt::WriteStyle) -> &mut Self { self.writer.write_style(write_style); self } /// Parses the directives string in the same form as the `RUST_LOG` /// environment variable. /// /// See the module documentation for more details. pub fn parse(&mut self, filters: &str) -> &mut Self { self.filter.parse(filters); self } /// Parses whether or not to write styles in the same form as the `RUST_LOG_STYLE` /// environment variable. /// /// See the module documentation for more details. pub fn parse_write_style(&mut self, write_style: &str) -> &mut Self { self.writer.parse(write_style); self } /// Initializes the global logger with the built env logger. /// /// This should be called early in the execution of a Rust program. Any log /// events that occur before initialization will be ignored. /// /// # Errors /// /// This function will fail if it is called more than once, or if another /// library has already initialized a global logger. pub fn try_init(&mut self) -> Result<(), SetLoggerError> { let logger = self.build(); log::set_max_level(logger.filter()); log::set_boxed_logger(Box::new(logger)) } /// Initializes the global logger with the built env logger. /// /// This should be called early in the execution of a Rust program. Any log /// events that occur before initialization will be ignored. /// /// # Panics /// /// This function will panic if it is called more than once, or if another /// library has already initialized a global logger. pub fn init(&mut self) { self.try_init().unwrap(); } /// Build an env logger. /// /// This method is kept private because the only way we support building /// loggers is by installing them as the single global logger for the /// `log` crate. pub fn build(&mut self) -> Logger { Logger { writer: self.writer.build(), filter: self.filter.build(), format: mem::replace(&mut self.format, Box::new(|_, _| Ok(()))), } } } impl Logger { /// Returns the maximum `LevelFilter` that this env logger instance is /// configured to output. pub fn filter(&self) -> LevelFilter { self.filter.filter() } /// Checks if this record matches the configured filter. pub fn matches(&self, record: &Record) -> bool { self.filter.matches(record) } } impl Log for Logger { fn enabled(&self, metadata: &Metadata) -> bool { self.filter.enabled(metadata) } fn log(&self, record: &Record) { if self.matches(record) { // Log records are written to a thread-local buffer before being printed // to the terminal. We clear these buffers afterwards, but they aren't shrinked // so will always at least have capacity for the largest log record formatted // on that thread. // // If multiple `Logger`s are used by the same threads then the thread-local // formatter might have different color support. If this is the case the // formatter and its buffer are discarded and recreated. thread_local! { static FORMATTER: RefCell<Option<Formatter>> = RefCell::new(None); } FORMATTER.with(|tl_buf| { // It's possible for implementations to sometimes // log-while-logging (e.g. a `std::fmt` implementation logs // internally) but it's super rare. If this happens make sure we // at least don't panic and ship some output to the screen. let mut a; let mut b = None; let tl_buf = match tl_buf.try_borrow_mut() { Ok(f) => { a = f; &mut *a } Err(_) => &mut b, }; // Check the buffer style. If it's different from the logger's // style then drop the buffer and recreate it. match *tl_buf { Some(ref mut formatter) => { if formatter.write_style() != self.writer.write_style() { *formatter = Formatter::new(&self.writer) } }, ref mut tl_buf => *tl_buf = Some(Formatter::new(&self.writer)) } // The format is guaranteed to be `Some` by this point let mut formatter = tl_buf.as_mut().unwrap(); let _ = (self.format)(&mut formatter, record).and_then(|_| formatter.print(&self.writer)); // Always clear the buffer afterwards formatter.clear(); }); } } fn flush(&self) {} } impl<'a> Env<'a> { /// Get a default set of environment variables. pub fn new() -> Self { Self::default() } /// Specify an environment variable to read the filter from. pub fn filter<E>(mut self, filter_env: E) -> Self where E: Into<Cow<'a, str>> { self.filter = filter_env.into(); self } fn get_filter(&self) -> Option<String> { env::var(&*self.filter).ok() } /// Specify an environment variable to read the style from. pub fn write_style<E>(mut self, write_style_env: E) -> Self where E: Into<Cow<'a, str>> { self.write_style = write_style_env.into(); self } fn get_write_style(&self) -> Option<String> { env::var(&*self.write_style).ok() } } impl<'a, T> From<T> for Env<'a> where T: Into<Cow<'a, str>> { fn from(filter_env: T) -> Self { Env::default().filter(filter_env.into()) } } impl<'a> Default for Env<'a> { fn default() -> Self { Env { filter: DEFAULT_FILTER_ENV.into(), write_style: DEFAULT_WRITE_STYLE_ENV.into() } } } mod std_fmt_impls { use std::fmt; use super::*; impl fmt::Debug for Logger{ fn fmt(&self, f: &mut fmt::Formatter)->fmt::Result { f.debug_struct("Logger") .field("filter", &self.filter) .finish() } } impl fmt::Debug for Builder{ fn fmt(&self, f: &mut fmt::Formatter)->fmt::Result { f.debug_struct("Logger") .field("filter", &self.filter) .field("writer", &self.writer) .finish() } } } /// Attempts to initialize the global logger with an env logger. /// /// This should be called early in the execution of a Rust program. Any log /// events that occur before initialization will be ignored. /// /// # Errors /// /// This function will fail if it is called more than once, or if another /// library has already initialized a global logger. pub fn try_init() -> Result<(), SetLoggerError> { try_init_from_env(Env::default()) } /// Initializes the global logger with an env logger. /// /// This should be called early in the execution of a Rust program. Any log /// events that occur before initialization will be ignored. /// /// # Panics /// /// This function will panic if it is called more than once, or if another /// library has already initialized a global logger. pub fn init() { try_init().unwrap(); } /// Attempts to initialize the global logger with an env logger from the given /// environment variables. /// /// This should be called early in the execution of a Rust program. Any log /// events that occur before initialization will be ignored. /// /// # Examples /// /// Initialise a logger using the `MY_LOG` environment variable for filters /// and `MY_LOG_STYLE` for writing colors: /// /// ``` /// # extern crate env_logger; /// use env_logger::{Builder, Env}; /// /// # fn run() -> Result<(), Box<::std::error::Error>> { /// let env = Env::new().filter("MY_LOG").write_style("MY_LOG_STYLE"); /// /// env_logger::try_init_from_env(env)?; /// /// Ok(()) /// # } /// # fn main() { run().unwrap(); } /// ``` /// /// # Errors /// /// This function will fail if it is called more than once, or if another /// library has already initialized a global logger. pub fn try_init_from_env<'a, E>(env: E) -> Result<(), SetLoggerError> where E: Into<Env<'a>> { let mut builder = Builder::from_env(env); builder.try_init() } /// Initializes the global logger with an env logger from the given environment /// variables. /// /// This should be called early in the execution of a Rust program. Any log /// events that occur before initialization will be ignored. /// /// # Examples /// /// Initialise a logger using the `MY_LOG` environment variable for filters /// and `MY_LOG_STYLE` for writing colors: /// /// ``` /// use env_logger::{Builder, Env}; /// /// let env = Env::new().filter("MY_LOG").write_style("MY_LOG_STYLE"); /// /// env_logger::init_from_env(env); /// ``` /// /// # Panics /// /// This function will panic if it is called more than once, or if another /// library has already initialized a global logger. pub fn init_from_env<'a, E>(env: E) where E: Into<Env<'a>> { try_init_from_env(env).unwrap(); }