kclock/main.go

package main

import (
	"flag"
	"fmt"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/mattn/go-isatty"
)

var (
	Version = "0.0.0"
	Build   = "alpha"

	local    string
	flagTick string
	flagVer  bool
)

func main() {

	flag.StringVar(&local, "local", fmt.Sprint(time.Local), "set local manually")
	flag.StringVar(&flagTick, "tick", "1s", "ticking interval")
	flag.BoolVar(&flagVer, "v", false, "show version")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: kclock [options]\n")
		flag.PrintDefaults()
	}

	flag.Parse()

	if flagVer {
		fmt.Printf("%v - %v\n", Version, Build)
		return
	}

	l, err := time.LoadLocation(local)
	if err != nil {
		panic(err)
	}
	time.Local = l

	watch()

}

func watch() {
	interval, err := time.ParseDuration(flagTick)
	if err != nil {
		panic(err)
	}
	color := isatty.IsTerminal(os.Stdout.Fd())
	if !color {
		color = isatty.IsCygwinTerminal(os.Stdout.Fd())
	}
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)

	start := time.Now()
	<-time.After(time.Until(time.Now().Truncate(time.Second).Add(time.Second)))
	tick := time.Tick(interval)
	if color {
		fmt.Printf("\n")
	}
	for {
		if color {
			fmt.Printf("\r\033[1A\033[0K\033[32m%v\033[0m\n", time.Now().Truncate(time.Second))
		} else {
			fmt.Printf("%v\n", time.Now().Truncate(time.Second))
		}
		select {
		case <-tick:
		case <-quit:
			if color {
				fmt.Printf("\r\033[0Ktime elapsed: \033[34m%v\033[0m\n", time.Since(start))
			} else {
				fmt.Printf("time elapsed: %v\n", time.Since(start))
			}
			return
		}

	}
}