count the number of rows in a file

read_file.go

package main

import (
	"bufio"
	"fmt"
	//"bytes"
	"flag"
	"os"
	//"io"
	//"io/ioutil"
	"time"
)

func main() {
	filepath := flag.String("f", "", "filepath name")
	flag.Parse()

	start := time.Now()
	//f, err := ioutil.ReadFile(*filepath)
	f, err := os.Open(*filepath)
	if err != nil {
		fmt.Println(err)
		return
	}
	defer f.Close()

	lineNum := 0
	/*
		//rd := bufio.NewReader(bytes.NewBuffer(f))
		rd := bufio.NewReader(f)
		for {
			_, err = rd.ReadString('\n')
			if err == io.EOF {
				break
			} else if err != nil {
				fmt.Println(err)
				return
			}
			lineNum++
		}
	*/
	scanner := bufio.NewScanner(f)
	//scanner.Split(bufio.ScanLines)
	for scanner.Scan() {
		lineNum++
	}
	fmt.Println(lineNum)
	fmt.Println(time.Now().Sub(start))
}