execute shell command n times

loop.go

package main

import (
	"flag"
	"fmt"
	"io"
	"os/exec"
	"strings"
	"time"
)

// Read out bytes and write to ch with blocking.
func Read(ch chan<- []byte, out io.ReadCloser) {
	defer out.Close()
	for {
		buffer := make([]byte, 4096)
		out.Read(buffer)
		ch <- buffer
	}
}

// Print ch bytes with blocking.
func Print(ch <-chan []byte) {
	for {
		select {
		case buf := <-ch:
			fmt.Print(string(buf))
		}
	}
}

func main() {
	times := flag.Int("times", 1, "execute times of app.")
	flag.Parse()

	args := flag.Args()

	if len(args) < 1 {
		fmt.Println("Missing app name")
		return
	}

	// New channel to read and print stdout from command app.
	ch := make(chan []byte, 10)
	defer close(ch)
	// Print command stdout from ch
	go Print(ch)

	for i := 0; i < *times; i++ {
		fmt.Printf("Current execute \"%v\" %d times\n", strings.Join(args, " "), i+1)
		cmd := exec.Command(args[0], args[1:]...)

		stdout, err := cmd.StdoutPipe()
		if err != nil {
			fmt.Printf("Pipe stdout got error: %v", err.Error())
			return
		}
		stderr, err := cmd.StderrPipe()
		if err != nil {
			fmt.Printf("Pipe stderr got error: %v", err.Error())
			return
		}
		// Read command stdout
		go Read(ch, stdout)
		// Read command stderr
		go Read(ch, stderr)

		cmd.Run()
		cmd.Wait()
		time.Sleep(100 * time.Millisecond)
	}
}