preview.go

package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path"
	"time"
)

var (
	root     string
	interval int
)

func init() {
	dir, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	root = dir

	flag.IntVar(&interval, "i", 120, "print interval")
	flag.Parse()
}

func getAbsPath(filename string) (absPath string) {
	absPath = path.Join(root, filename)
	if _, err := os.Stat(absPath); os.IsNotExist(err) {
		log.Fatalf("file '%s' not exist\n", filename)
	}
	return
}

func main() {
	args := flag.Args()
	if len(args) == 0 {
		log.Fatal("error: no input file\n")
	}
	filename := args[0]

	data, err := ioutil.ReadFile(getAbsPath(filename))
	if err != nil {
		log.Fatal(err)
	}

	characters := []rune(string(data))
	for _, char := range characters {
		time.Sleep(time.Millisecond * time.Duration(interval))
		fmt.Print(string(char))
	}
}