vendor/log/README.md

   1 log
   2 ===
   3
   4 A Rust library providing a lightweight logging *facade*.
   5
   6 [![Build Status](https://travis-ci.org/rust-lang-nursery/log.svg?branch=master)](https://travis-ci.org/rust-lang-nursery/log)
   7 [![Build status](https://ci.appveyor.com/api/projects/status/nopdjmmjt45xcrki?svg=true)](https://ci.appveyor.com/project/alexcrichton/log)
   8 [![Latest version](https://img.shields.io/crates/v/log.svg)](https://crates.io/crates/log)
   9 [![Documentation](https://docs.rs/log/badge.svg)](https://docs.rs/log)
  10 ![License](https://img.shields.io/crates/l/log.svg)
  11
  12 * [`log` documentation](https://docs.rs/log)
  13
  14 A logging facade provides a single logging API that abstracts over the actual
  15 logging implementation. Libraries can use the logging API provided by this
  16 crate, and the consumer of those libraries can choose the logging
  17 implementation that is most suitable for its use case.
  18
  19 ## Usage
  20
  21 ## In libraries
  22
  23 Libraries should link only to the `log` crate, and use the provided macros to
  24 log whatever information will be useful to downstream consumers:
  25
  26 ```toml
  27 [dependencies]
  28 log = "0.4"
  29 ```
  30
  31 ```rust
  32 #[macro_use]
  33 extern crate log;
  34
  35 pub fn shave_the_yak(yak: &mut Yak) {
  36     trace!("Commencing yak shaving");
  37
  38     loop {
  39         match find_a_razor() {
  40             Ok(razor) => {
  41                 info!("Razor located: {}", razor);
  42                 yak.shave(razor);
  43                 break;
  44             }
  45             Err(err) => {
  46                 warn!("Unable to locate a razor: {}, retrying", err);
  47             }
  48         }
  49     }
  50 }
  51 ```
  52
  53 ## In executables
  54
  55 In order to produce log output executables have to use a logger implementation compatible with the facade.
  56 There are many available implementations to chose from, here are some of the most popular ones:
  57
  58 * Simple minimal loggers:
  59     * [`env_logger`](https://docs.rs/env_logger/*/env_logger/)
  60     * [`simple_logger`](https://github.com/borntyping/rust-simple_logger)
  61     * [`simplelog`](https://github.com/drakulix/simplelog.rs)
  62     * [`pretty_env_logger`](https://docs.rs/pretty_env_logger/*/pretty_env_logger/)
  63     * [`stderrlog`](https://docs.rs/stderrlog/*/stderrlog/)
  64     * [`flexi_logger`](https://docs.rs/flexi_logger/*/flexi_logger/)
  65 * Complex configurable frameworks:
  66     * [`log4rs`](https://docs.rs/log4rs/*/log4rs/)
  67     * [`fern`](https://docs.rs/fern/*/fern/)
  68 * Adaptors for other facilities:
  69     * [`syslog`](https://docs.rs/syslog/*/syslog/)
  70     * [`slog-stdlog`](https://docs.rs/slog-stdlog/*/slog_stdlog/)
  71     * [`android_log`](https://docs.rs/android_log/*/android_log/)
  72
  73 Executables should choose a logger implementation and initialize it early in the
  74 runtime of the program. Logger implementations will typically include a
  75 function to do this. Any log messages generated before the logger is
  76 initialized will be ignored.
  77
  78 The executable itself may use the `log` crate to log as well.