doc: Runnable examples logging.
Also use //! Instead of /*! in liblog.
This commit is contained in:
Jonas Hietala
parent
dee8423531
commit
26b40be7ed
@ -8,120 +8,154 @@
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/*!
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Utilities for program-wide and customizable logging
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## Example
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```
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#![feature(phase)]
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#[phase(plugin, link)] extern crate log;
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fn main() {
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debug!("this is a debug {}", "message");
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error!("this is printed by default");
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if log_enabled!(log::INFO) {
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let x = 3i * 4i; // expensive computation
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info!("the answer was: {}", x);
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}
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}
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```
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## Logging Macros
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There are five macros that the logging subsystem uses:
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* `log!(level, ...)` - the generic logging macro, takes a level as a u32 and any
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related `format!` arguments
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* `debug!(...)` - a macro hard-wired to the log level of `DEBUG`
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* `info!(...)` - a macro hard-wired to the log level of `INFO`
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* `warn!(...)` - a macro hard-wired to the log level of `WARN`
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* `error!(...)` - a macro hard-wired to the log level of `ERROR`
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All of these macros use the same style of syntax as the `format!` syntax
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extension. Details about the syntax can be found in the documentation of
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`std::fmt` along with the Rust tutorial/manual.
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If you want to check at runtime if a given logging level is enabled (e.g. if the
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information you would want to log is expensive to produce), you can use the
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following macro:
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* `log_enabled!(level)` - returns true if logging of the given level is enabled
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## Enabling logging
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Log levels are controlled on a per-module basis, and by default all logging is
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disabled except for `error!` (a log level of 1). Logging is controlled via the
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`RUST_LOG` environment variable. The value of this environment variable is a
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comma-separated list of logging directives. A logging directive is of the form:
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```text
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path::to::module=log_level
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```
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The path to the module is rooted in the name of the crate it was compiled for,
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so if your program is contained in a file `hello.rs`, for example, to turn on
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logging for this file you would use a value of `RUST_LOG=hello`.
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Furthermore, this path is a prefix-search, so all modules nested in the
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specified module will also have logging enabled.
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The actual `log_level` is optional to specify. If omitted, all logging will be
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enabled. If specified, the it must be either a numeric in the range of 1-255, or
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it must be one of the strings `debug`, `error`, `info`, or `warn`. If a numeric
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is specified, then all logging less than or equal to that numeral is enabled.
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For example, if logging level 3 is active, error, warn, and info logs will be
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printed, but debug will be omitted.
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As the log level for a module is optional, the module to enable logging for is
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also optional. If only a `log_level` is provided, then the global log level for
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all modules is set to this value.
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Some examples of valid values of `RUST_LOG` are:
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* `hello` turns on all logging for the 'hello' module
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* `info` turns on all info logging
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* `hello=debug` turns on debug logging for 'hello'
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* `hello=3` turns on info logging for 'hello'
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* `hello,std::option` turns on hello, and std's option logging
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* `error,hello=warn` turn on global error logging and also warn for hello
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## Filtering results
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A RUST_LOG directive may include a regex filter. The syntax is to append `/`
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followed by a regex. Each message is checked against the regex, and is only
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logged if it matches. Note that the matching is done after formatting the log
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string but before adding any logging meta-data. There is a single filter for all
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modules.
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Some examples:
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* `hello/foo` turns on all logging for the 'hello' module where the log message
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includes 'foo'.
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* `info/f.o` turns on all info logging where the log message includes 'foo',
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'f1o', 'fao', etc.
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* `hello=debug/foo*foo` turns on debug logging for 'hello' where the the log
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message includes 'foofoo' or 'fofoo' or 'fooooooofoo', etc.
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* `error,hello=warn/[0-9] scopes` turn on global error logging and also warn for
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hello. In both cases the log message must include a single digit number
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followed by 'scopes'
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## Performance and Side Effects
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Each of these macros will expand to code similar to:
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```rust,ignore
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if log_level <= my_module_log_level() {
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::log::log(log_level, format!(...));
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}
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```
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What this means is that each of these macros are very cheap at runtime if
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they're turned off (just a load and an integer comparison). This also means that
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if logging is disabled, none of the components of the log will be executed.
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*/
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//! Utilities for program-wide and customizable logging
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//!
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//! ## Example
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//!
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//! ```
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//! #![feature(phase)]
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//! #[phase(plugin, link)] extern crate log;
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//!
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//! fn main() {
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//! debug!("this is a debug {}", "message");
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//! error!("this is printed by default");
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//!
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//! if log_enabled!(log::INFO) {
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//! let x = 3i * 4i; // expensive computation
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//! info!("the answer was: {}", x);
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//! }
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//! }
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//! ```
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//!
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//! Assumes the binary is `main`:
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//!
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//! ```{.bash}
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//! $ RUST_LOG=error ./main
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//! ERROR:main: this is printed by default
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//! ```
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//!
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//! ```{.bash}
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//! $ RUST_LOG=info ./main
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//! ERROR:main: this is printed by default
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//! INFO:main: the answer was: 12
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//! ```
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//!
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//! ```{.bash}
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//! $ RUST_LOG=debug ./main
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//! DEBUG:main: this is a debug message
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//! ERROR:main: this is printed by default
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//! INFO:main: the answer was: 12
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//! ```
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//!
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//! You can also set the log level on a per module basis:
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//!
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//! ```{.bash}
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//! $ RUST_LOG=main=info ./main
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//! ERROR:main: this is printed by default
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//! INFO:main: the answer was: 12
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//! ```
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//!
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//! And enable all logging:
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//!
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//! ```{.bash}
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//! $ RUST_LOG=main ./main
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//! DEBUG:main: this is a debug message
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//! ERROR:main: this is printed by default
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//! INFO:main: the answer was: 12
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//! ```
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//!
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//!
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//! ## Logging Macros
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//!
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//! There are five macros that the logging subsystem uses:
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//!
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//! * `log!(level, ...)` - the generic logging macro, takes a level as a u32 and any
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//! related `format!` arguments
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//! * `debug!(...)` - a macro hard-wired to the log level of `DEBUG`
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//! * `info!(...)` - a macro hard-wired to the log level of `INFO`
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//! * `warn!(...)` - a macro hard-wired to the log level of `WARN`
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//! * `error!(...)` - a macro hard-wired to the log level of `ERROR`
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//!
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//! All of these macros use the same style of syntax as the `format!` syntax
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//! extension. Details about the syntax can be found in the documentation of
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//! `std::fmt` along with the Rust tutorial/manual.
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//!
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//! If you want to check at runtime if a given logging level is enabled (e.g. if the
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//! information you would want to log is expensive to produce), you can use the
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//! following macro:
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//!
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//! * `log_enabled!(level)` - returns true if logging of the given level is enabled
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//!
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//! ## Enabling logging
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//!
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//! Log levels are controlled on a per-module basis, and by default all logging is
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//! disabled except for `error!` (a log level of 1). Logging is controlled via the
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//! `RUST_LOG` environment variable. The value of this environment variable is a
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//! comma-separated list of logging directives. A logging directive is of the form:
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//!
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//! ```text
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//! path::to::module=log_level
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//! ```
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//!
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//! The path to the module is rooted in the name of the crate it was compiled for,
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//! so if your program is contained in a file `hello.rs`, for example, to turn on
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//! logging for this file you would use a value of `RUST_LOG=hello`.
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//! Furthermore, this path is a prefix-search, so all modules nested in the
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//! specified module will also have logging enabled.
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//!
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//! The actual `log_level` is optional to specify. If omitted, all logging will be
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//! enabled. If specified, the it must be either a numeric in the range of 1-255, or
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//! it must be one of the strings `debug`, `error`, `info`, or `warn`. If a numeric
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//! is specified, then all logging less than or equal to that numeral is enabled.
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//! For example, if logging level 3 is active, error, warn, and info logs will be
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//! printed, but debug will be omitted.
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//!
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//! As the log level for a module is optional, the module to enable logging for is
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//! also optional. If only a `log_level` is provided, then the global log level for
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//! all modules is set to this value.
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//!
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//! Some examples of valid values of `RUST_LOG` are:
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//!
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//! * `hello` turns on all logging for the 'hello' module
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//! * `info` turns on all info logging
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//! * `hello=debug` turns on debug logging for 'hello'
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//! * `hello=3` turns on info logging for 'hello'
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//! * `hello,std::option` turns on hello, and std's option logging
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//! * `error,hello=warn` turn on global error logging and also warn for hello
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//!
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//! ## Filtering results
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//!
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//! A RUST_LOG directive may include a regex filter. The syntax is to append `/`
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//! followed by a regex. Each message is checked against the regex, and is only
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//! logged if it matches. Note that the matching is done after formatting the log
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//! string but before adding any logging meta-data. There is a single filter for all
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//! modules.
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//!
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//! Some examples:
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//!
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//! * `hello/foo` turns on all logging for the 'hello' module where the log message
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//! includes 'foo'.
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//! * `info/f.o` turns on all info logging where the log message includes 'foo',
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//! 'f1o', 'fao', etc.
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//! * `hello=debug/foo*foo` turns on debug logging for 'hello' where the the log
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//! message includes 'foofoo' or 'fofoo' or 'fooooooofoo', etc.
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//! * `error,hello=warn/[0-9] scopes` turn on global error logging and also warn for
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//! hello. In both cases the log message must include a single digit number
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//! followed by 'scopes'
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//!
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//! ## Performance and Side Effects
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//!
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//! Each of these macros will expand to code similar to:
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//!
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//! ```rust,ignore
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//! if log_level <= my_module_log_level() {
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//! ::log::log(log_level, format!(...));
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//! }
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//! ```
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//!
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//! What this means is that each of these macros are very cheap at runtime if
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//! they're turned off (just a load and an integer comparison). This also means that
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//! if logging is disabled, none of the components of the log will be executed.
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#![crate_name = "log"]
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#![experimental]
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@ -24,11 +24,31 @@
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/// #![feature(phase)]
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/// #[phase(plugin, link)] extern crate log;
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///
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/// # fn main() {
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/// log!(log::DEBUG, "this is a debug message");
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/// log!(log::WARN, "this is a warning {}", "message");
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/// log!(6, "this is a custom logging level: {level}", level=6u);
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/// # }
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/// fn main() {
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/// log!(log::WARN, "this is a warning {}", "message");
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/// log!(log::DEBUG, "this is a debug message");
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/// log!(6, "this is a custom logging level: {level}", level=6u);
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/// }
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/// ```
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///
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/// Assumes the binary is `main`:
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///
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/// ```{.bash}
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/// $ RUST_LOG=warn ./main
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/// WARN:main: this is a warning message
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/// ```
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///
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/// ```{.bash}
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/// $ RUST_LOG=debug ./main
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/// DEBUG:main: this is a debug message
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/// WARN:main: this is a warning message
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/// ```
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///
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/// ```{.bash}
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/// $ RUST_LOG=6 ./main
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/// DEBUG:main: this is a debug message
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/// WARN:main: this is a warning message
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/// 6:main: this is a custom logging level: 6
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/// ```
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#[macro_export]
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macro_rules! log(
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@ -53,11 +73,19 @@ macro_rules! log(
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/// #![feature(phase)]
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/// #[phase(plugin, link)] extern crate log;
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///
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/// # fn main() {
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/// # let error = 3u;
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/// error!("the build has failed with error code: {}", error);
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/// # }
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/// fn main() {
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/// let error = 3u;
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/// error!("the build has failed with error code: {}", error);
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/// }
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/// ```
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///
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/// Assumes the binary is `main`:
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///
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/// ```{.bash}
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/// $ RUST_LOG=error ./main
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/// ERROR:main: the build has failed with error code: 3
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/// ```
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///
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#[macro_export]
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macro_rules! error(
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($($arg:tt)*) => (log!(::log::ERROR, $($arg)*))
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@ -71,10 +99,17 @@ macro_rules! error(
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/// #![feature(phase)]
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/// #[phase(plugin, link)] extern crate log;
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///
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/// # fn main() {
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/// # let code = 3u;
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/// warn!("you may like to know that a process exited with: {}", code);
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/// # }
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/// fn main() {
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/// let code = 3u;
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/// warn!("you may like to know that a process exited with: {}", code);
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/// }
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/// ```
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///
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/// Assumes the binary is `main`:
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///
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/// ```{.bash}
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/// $ RUST_LOG=warn ./main
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/// WARN:main: you may like to know that a process exited with: 3
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/// ```
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#[macro_export]
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macro_rules! warn(
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@ -89,10 +124,17 @@ macro_rules! warn(
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/// #![feature(phase)]
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/// #[phase(plugin, link)] extern crate log;
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///
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/// # fn main() {
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/// # let ret = 3i;
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/// info!("this function is about to return: {}", ret);
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/// # }
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/// fn main() {
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/// let ret = 3i;
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/// info!("this function is about to return: {}", ret);
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/// }
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/// ```
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///
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/// Assumes the binary is `main`:
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///
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/// ```{.bash}
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/// $ RUST_LOG=info ./main
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/// INFO:main: this function is about to return: 3
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/// ```
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#[macro_export]
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macro_rules! info(
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@ -109,9 +151,16 @@ macro_rules! info(
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/// #![feature(phase)]
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/// #[phase(plugin, link)] extern crate log;
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///
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/// # fn main() {
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/// debug!("x = {x}, y = {y}", x=10i, y=20i);
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/// # }
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/// fn main() {
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/// debug!("x = {x}, y = {y}", x=10i, y=20i);
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/// }
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/// ```
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///
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/// Assumes the binary is `main`:
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///
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/// ```{.bash}
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/// $ RUST_LOG=debug ./main
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/// DEBUG:main: x = 10, y = 20
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/// ```
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#[macro_export]
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macro_rules! debug(
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@ -126,14 +175,26 @@ macro_rules! debug(
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/// #![feature(phase)]
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/// #[phase(plugin, link)] extern crate log;
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///
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/// # fn main() {
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/// # struct Point { x: int, y: int }
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/// # fn some_expensive_computation() -> Point { Point { x: 1, y: 2 } }
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/// if log_enabled!(log::DEBUG) {
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/// let x = some_expensive_computation();
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/// debug!("x.x = {}, x.y = {}", x.x, x.y);
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/// struct Point { x: int, y: int }
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/// fn some_expensive_computation() -> Point { Point { x: 1, y: 2 } }
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///
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/// fn main() {
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/// if log_enabled!(log::DEBUG) {
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/// let x = some_expensive_computation();
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/// debug!("x.x = {}, x.y = {}", x.x, x.y);
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/// }
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/// }
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/// # }
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/// ```
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///
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/// Assumes the binary is `main`:
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///
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/// ```{.bash}
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/// $ RUST_LOG=error ./main
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/// ```
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///
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/// ```{.bash}
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/// $ RUST_LOG=debug ./main
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/// DEBUG:main: x.x = 1, x.y = 2
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/// ```
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#[macro_export]
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macro_rules! log_enabled(
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