Go Package log

External

• https://golang.org/pkg/log

Internal

• Go Logging
• Standard Library

Overview

The "log" package provides support for logging messages to stdout, stderr or custom devices.

import (
    "log"
)
...

log.Printf("something %s\n", "else")

Elements

log.Fatal(), log.Fatalf()

https://golang.org/pkg/log/#Fatal

Fatal is equivalent to Print() followed by a call to os.Exit(1).

Recipes

Changing the Logging Device

By default, the logger is set to write to stderr. To change that, execute log.SetOutput() from the init() function, or at least before using the logging system.

Log to stdout

import (
    "log"
    "os"
)
...
func init() {

    // change the device for logging to stdout
    log.SetOutput(os.Stdout)
}

Log to a File

import (
    "log"
    "os"
)
...
func init() {
   // change the device for logging to a custom file 
   fileName := "/tmp/somefile.log"
   f, err := os.Create(fileName)
   if err != nil {
      fmt.Printf("failed to open log file %s for writing\n", fileName)
      ...
   } else {
      log.SetOutput(f)
   }
}