Module flexi_logger::writers

Contains the trait LogWriter for extending flexi_logger with additional log writers, and two concrete implementations for writing to files (FileLogWriter) or to the syslog (SyslogWriter). You can also use your own implementations of LogWriter.

Such log writers can be used in two ways:

• With Logger::log_target() you can influence to which output stream normal log messages will be written, i.e. from log macro calls without explicit target specification.

  See LogTarget for the available options.

  These log calls will only be written if they match the current log specification.

• Logger::add_writer() can be used to register an additional log writer under a target name. The target name can then be used in calls to the log macro for directing log messages to the desired writers.

  A log call with a target value that has the form {Name1,Name2,...}, i.e., a comma-separated list of target names, within braces, is not sent to the default logger, but to the loggers specified explicitly in the list. In such a list you can again specify the default logger with the target name _Default.

  These log calls will not be affected by the value of flexi_logger’s log specification; they will always be written, as you might want it for alerts or auditing.

  In the following example we define an alert writer, and a macro to facilitate using it (and avoid using the explicit target specification in the macro call), and show some example calls.

  use log::*;
  
  use flexi_logger::Logger;
  use flexi_logger::writers::FileLogWriter;
  
  // Configure a FileLogWriter for alert messages
  pub fn alert_logger() -> Box<FileLogWriter> {
      Box::new(FileLogWriter::builder()
          .discriminant("Alert")
          .suffix("alerts")
          .print_message()
          .try_build()
          .unwrap())
  }
  
  // Define a macro for writing messages to the alert log and to the normal log
  #[macro_use]
  mod macros {
      #[macro_export]
      macro_rules! alert_error {
          ($($arg:tt)*) => (
              error!(target: "{Alert,_Default}", $($arg)*);
          )
      }
  }
  
  fn main() {
      Logger::with_env_or_str("info")
          .print_message()
          .log_to_file()
          .add_writer("Alert", alert_logger())
          .start()
          .unwrap_or_else(|e| panic!("Logger initialization failed with {}", e));
  
  
      // Explicitly send logs to different loggers
      error!(target : "{Alert}", "This is only an alert");
      error!(target : "{Alert,_Default}", "This is an alert and log message");
  
      // Nicer: use the explicit macro
      alert_error!("This is another alert and log message");
  
      // Standard log macros write only to the normal log
      error!("This is a normal error message");
      warn!("This is a warning");
      info!("This is an info message");
      debug!("This is a debug message - you will not see it");
      trace!("This is a trace message - you will not see it");
  }
  

Structs

FileLogWriter	A configurable LogWriter implementation that writes to a file or a sequence of files.
FileLogWriterBuilder	Builder for FileLogWriter.

Traits

LogWriter

Writes to a single log output stream.