Using k8s.io/klog together with cobra in golang

2019-02-05

February 5, 2019

2 minutes

This post is somehow related to a previous article about using glog together with cobra. This time, we will be using klog which is a Kubernetes fork of glog.

	package main

	import (
	goflag "flag"

	"github.com/spf13/cobra"
	flag "github.com/spf13/pflag"
	"k8s.io/klog"
	)

	var (
	str = "hello world"

	rootCmd = &cobra.Command{
	Use: "echo",
	Short: "use klog with cobra",
	Long: "Use klog together with cobra.",
	}
	)

	func init() {
	rootCmd.Flags().SortFlags = false
	rootCmd.AddCommand(
	RunCmd(),
	)

	klog.InitFlags(nil)
	goflag.Parse()
	flag.CommandLine.AddGoFlagSet(goflag.CommandLine)
	}

	func RunCmd() *cobra.Command {
	runcmd := &cobra.Command{
	Use: "run",
	Short: "run command",
	Long: "Run command.",
	Run: func(cmd *cobra.Command, args []string) {
	klog.Infof("echo=%v", str)
	},
	}

	runcmd.Flags().SortFlags = false
	runcmd.Flags().StringVar(&str, "str", str, "string to print")
	return runcmd
	}

	func main() {
	if err := rootCmd.Execute(); err != nil {
	klog.Fatalf("root cmd execute failed, err=%v", err)
	}
	}

view raw blog_20190205_use_klog_with_cobra.go hosted with ❤ by GitHub

# run the -h command
$ ./cobraklog -h
Usage of ./cobraklog:
  -alsologtostderr
        log to standard error as well as files
  -log_backtrace_at value
        when logging hits line file:N, emit a stack trace
  -log_dir string
        If non-empty, write log files in this directory
  -log_file string
        If non-empty, use this log file
  -logtostderr
        log to standard error instead of files
  -skip_headers
        If true, avoid header prefixes in the log messages
  -stderrthreshold value
        logs at or above this threshold go to stderr (default 2)
  -v value
        log level for V logs
  -vmodule value
        comma-separated list of pattern=N settings for file-filtered logging

# run cobra's `help` command
$ ./cobraklog help
Use klog together with cobra.

Usage:
  cobraklog [command]

Available Commands:
  help        Help about any command
  run         run command

Flags:
      --alsologtostderr                  log to standard error as well as files
      --log_backtrace_at traceLocation   when logging hits line file:N, emit a stack trace (default :0)
      --log_dir string                   If non-empty, write log files in this directory
      --log_file string                  If non-empty, use this log file
      --logtostderr                      log to standard error instead of files
      --skip_headers                     If true, avoid header prefixes in the log messages
      --stderrthreshold severity         logs at or above this threshold go to stderr (default 2)
  -v, --v Level                          log level for V logs
      --vmodule moduleSpec               comma-separated list of pattern=N settings for file-filtered logging
  -h, --help                             help for cobraklog

Use "cobraklog [command] --help" for more information about a command.

# run `help` on our subcommand `run`
$ ./cobraklog help run
Run command.

Usage:
  cobraklog run [flags]

Flags:
      --str string   string to print (default "hello world")
  -h, --help         help for run

Global Flags:
      --alsologtostderr                  log to standard error as well as files
      --log_backtrace_at traceLocation   when logging hits line file:N, emit a stack trace (default :0)
      --log_dir string                   If non-empty, write log files in this directory
      --log_file string                  If non-empty, use this log file
      --logtostderr                      log to standard error instead of files
      --skip_headers                     If true, avoid header prefixes in the log messages
      --stderrthreshold severity         logs at or above this threshold go to stderr (default 2)
  -v, --v Level                          log level for V logs
      --vmodule moduleSpec               comma-separated list of pattern=N settings for file-filtered logging

# run the `run` subcommand
$ ./cobraklog run --logtostderr
I0205 16:37:39.110849   13672 main.go:41] echo=hello world

$ ./cobraklog run --logtostderr --str "hello alien world"
I0205 16:39:37.212187   13685 main.go:41] echo=hello alien world