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Published: Sep 15, 2015 License: MIT Imports: 7 Imported by: 37



Package stdlog provides simple and fast logging to the standard output (stdout) and is optimized for programs launched via a shell or cron. It can also be used to log to a file by redirecting the standard output to a file. This package is thread-safe.

Basic examples:

logger := stdlog.GetFromFlags()
logger.Info("Connecting to the server...")
logger.Errorf("Connection failed: %q", err)

Will output:

2014-04-02 18:09:15.862 INFO Connecting to the API...
2014-04-02 18:10:14.347 ERROR Connection failed (Server is unavailable).

Log*() functions can be used to avoid evaluating arguments when it is expensive and unnecessary:

logger.Debug("Memory usage: %s", getMemoryUsage())
if LogDebug() { logger.Debug("Memory usage: %s", getMemoryUsage()) }

If debug logging is off the getMemoryUsage() will be executed on the first line while it will not be executed on the second line.

List of command-line arguments:

    Log events at or above this level are logged.
    Logs are written to standard error (stderr) instead of standard
    Until this level is reached nothing is output and logs are stored
    in the memory. Once a log event is at or above this level, it
    outputs all logs in memory as well as the future log events. This
    feature should not be used with long-running processes.

The available levels are the eight ones described in RFC 5424 (debug, info, notice, warning, error, critical, alert, emergency) and none.

Some use cases:

  • By default, all logs except debug ones are output to the stdout. Which is useful to follow the execution of a program launched via a shell.
  • A program launched by a crontab where the variable `MAILTO` is set with `-debug -flushlog=error` will send all logs generated by the program only if an error happens. When there is no error the email will not be sent.
  • `my_program > /var/log/my_program/my_program-$(date+%Y-%m-%d-%H%M%S).log` will create a log file in /var/log/my_program each time it is run.



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func GetFromFlags

func GetFromFlags() log.Logger

GetFromFlags returns the logger defined by the command-line flags. This function runs flag.Parse() if it has not been run yet.


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