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Merge pull request #256 from yandexx/env-logger-var

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Use a custom environment variable to set up logging
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Brian Anderson 2017-07-24 17:17:16 -07:00 committed by GitHub
commit a2dbd8dadc
2 changed files with 50 additions and 5 deletions
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2
src/intro.md
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@ -99,6 +99,7 @@ community. It needs and welcomes help. For details see
| [Enable log levels per module][ex-log-mod] | [![log-badge]][log] [![env_logger-badge]][env_logger] | [![cat-debugging-badge]][cat-debugging] |
| [Log to stdout instead of stderr][ex-log-stdout] | [![log-badge]][log] [![env_logger-badge]][env_logger] | [![cat-debugging-badge]][cat-debugging] |
| [Log messages with a custom logger][ex-log-custom-logger] | [![log-badge]][log] | [![cat-debugging-badge]][cat-debugging] |
| [Use a custom environment variable to set up logging][ex-log-env-variable] | [![log-badge]][log] [![env_logger-badge]][env_logger] | [![cat-debugging-badge]][cat-debugging] |
| [Include timestamp in log messages][ex-log-timestamp] | [![log-badge]][log] [![env_logger-badge]][env_logger] [![chrono-badge]][chrono] | [![cat-debugging-badge]][cat-debugging] |
| [Log to the Unix syslog][ex-log-syslog] | [![log-badge]][log] [![syslog-badge]][syslog] | [![cat-debugging-badge]][cat-debugging] |
| [Log messages to a custom location][ex-log-custom] | [![log-badge]][log] | [![cat-debugging-badge]][cat-debugging] |
@ -243,6 +244,7 @@ Keep lines sorted.
[ex-log-custom-logger]: logging.html#ex-log-custom-logger
[ex-log-custom]: logging.html#ex-log-custom
[ex-log-debug]: logging.html#ex-log-debug
[ex-log-env-variable]: logging.html#ex-log-env-variable
[ex-log-error]: logging.html#ex-log-error
[ex-log-mod]: logging.html#ex-log-mod
[ex-log-syslog]: logging.html#ex-log-syslog

53
src/logging.md
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@ -7,6 +7,7 @@
| [Enable log levels per module][ex-log-mod] | [![log-badge]][log] [![env_logger-badge]][env_logger] | [![cat-debugging-badge]][cat-debugging] |
| [Log to stdout instead of stderr][ex-log-stdout] | [![log-badge]][log] [![env_logger-badge]][env_logger] | [![cat-debugging-badge]][cat-debugging] |
| [Log messages with a custom logger][ex-log-custom-logger] | [![log-badge]][log] | [![cat-debugging-badge]][cat-debugging] |
| [Use a custom environment variable to set up logging][ex-log-env-variable] | [![log-badge]][log] [![env_logger-badge]][env_logger] | [![cat-debugging-badge]][cat-debugging] |
| [Include timestamp in log messages][ex-log-timestamp] | [![log-badge]][log] [![env_logger-badge]][env_logger] [![chrono-badge]][chrono] | [![cat-debugging-badge]][cat-debugging] |
| [Log to the Unix syslog][ex-log-syslog] | [![log-badge]][log] [![syslog-badge]][syslog] | [![cat-debugging-badge]][cat-debugging] |
| [Log messages to a custom location][ex-log-custom] | [![log-badge]][log] | [![cat-debugging-badge]][cat-debugging] |
@ -274,6 +275,50 @@ fn run() -> Result<()> {
# quick_main!(run);
```
[ex-log-env-variable]: #ex-log-env-variable
<a name="ex-log-env-variable"></a>
## Use a custom environment variable to set up logging
[![log-badge]][log] [![env_logger-badge]][env_logger] [![cat-debugging-badge]][cat-debugging]
Logging is configured with [`LogBuilder`].
[`LogBuilder::parse`] parses `MY_APP_LOG`
environmental variable contents in the form of [`RUST_LOG`] syntax.
Then [`LogBuilder::init`] initializes the logger.
All these steps are normally done internally by [`env_logger::init`].
```rust
# #[macro_use]
# extern crate error_chain;
#[macro_use]
extern crate log;
extern crate env_logger;
use std::env;
use env_logger::LogBuilder;
# error_chain! {
# foreign_links {
# EnvLogger(log::SetLoggerError);
# }
# }
#
fn run() -> Result<()> {
LogBuilder::new()
.parse(&env::var("MY_APP_LOG").unwrap_or_default())
.init()?;
info!("informational message");
warn!("warning message");
error!("this is an error {}", "message");
Ok(())
}
#
# quick_main!(run);
```
[ex-log-timestamp]: #ex-log-timestamp
<a name="ex-log-timestamp"></a>
## Include timestamp in log messages
@ -285,9 +330,6 @@ Each log entry calls [`Local::now`] to get the current [`DateTime`] in local tim
The example calls [`LogBuilder::format`] to set a closure which formats each
message text with timestamp, [`LogRecord::level`] and body ([`LogRecord::args`]).
Subsequently calls [`LogBuilder::parse`] which parses `MY_APP_LOG` environmental variable contents in the form of [`RUST_LOG`] syntax.
Finally calls [`LogBuilder::init`] to initialize the logger.
All these steps are normally done internally by [`env_logger::init`].
```rust
# #[macro_use]
@ -297,9 +339,10 @@ extern crate log;
extern crate env_logger;
extern crate chrono;
use chrono::Local;
use env_logger::LogBuilder;
use std::env;
use env_logger::LogBuilder;
use chrono::Local;
#
# error_chain! {
# foreign_links {