get the realtime output for a shell command in golang|-|{"files":{"shell_output.go":{"env":"plain"}},"tag":"bigdata"}

shell_output.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strings"
)

func main() {
	cmdName := "ping 127.0.0.1"
	cmdArgs := strings.Fields(cmdName)

	cmd := exec.Command(cmdArgs[0], cmdArgs[1:len(cmdArgs)]...)
	stdout, _ := cmd.StdoutPipe()
	cmd.Start()
	oneByte := make([]byte, 100)
	num := 1
	for {
		_, err := stdout.Read(oneByte)
		if err != nil {
			fmt.Printf(err.Error())
			break
		}
		r := bufio.NewReader(stdout)
		line, _, _ := r.ReadLine()
		fmt.Println(string(line))
		num = num + 1
		if num > 3 {
			os.Exit(0)
		}
	}

	cmd.Wait()
}

nice work 👍 thanks

nice, it really helps 👍

For people coming from google - I revised a bit.

package main

import (
  "bufio"
  "os"
  "os/exec"
  "fmt"
  "log"
)

func main() {
  cmd := exec.Command("ping", "127.0.0.1")
  stdout, err := cmd.StdoutPipe()
  if err != nil {
    log.Fatal(err)
  }
  cmd.Start()

  buf := bufio.NewReader(stdout) // Notice that this is not in a loop
  num := 1
  for {
    line, _, _ := buf.ReadLine()
    if num > 3 {
      os.Exit(0)
    }
    num += 1
    fmt.Println(string(line))
  }
}

You guys are the best!!! )

Hello Sir, i want to run some curl bash scripts via golang want to show that script’s realtime output to the user.
for example,
i want to run
curl -Lso- bench.sh | bash
in golang and show realtime output to the user, how can i do this?

actually, i want to run some bash scripts and some binary files via golang and show the output to the user (realtime output) if read line by line and show to user then also OK but output should show to user in fast time
not like bash script executed and after execution output will show, i don’t want like that.
the bash script installs library and packages so it may take some time so that i want to show real time output of the bash script to user.

For people coming from google - I revised a bit.

package main

import (
  "bufio"
  "os"
  "os/exec"
  "fmt"
  "log"
)

func main() {
  cmd := exec.Command("ping", "127.0.0.1")
  stdout, err := cmd.StdoutPipe()
  if err != nil {
    log.Fatal(err)
  }
  cmd.Start()

  buf := bufio.NewReader(stdout) // Notice that this is not in a loop
  num := 1
  for {
    line, _, _ := buf.ReadLine()
    if num > 3 {
      os.Exit(0)
    }
    num += 1
    fmt.Println(string(line))
  }
}

when I ran this, the ping command is stopping after an interval of time.
I use windows and ping in windows pings 4 times as default similar to ping -c4 127.0.0.1
but is there a way where we can get the return value of the command and stop the for loop?

Still up to date, March 21 2022

Nice !

Here is another example that I made based on the code posted above:

func RunCmd(ctx context.Context, cmdstr string) error {
	args := strings.Fields(cmdstr)
	cmd := exec.CommandContext(ctx, args[0], args[1:]...)

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return err
	}

	var wg sync.WaitGroup
	wg.Add(1)

	scanner := bufio.NewScanner(stdout)
	go func() {
		for scanner.Scan() {
			log.Printf("out: %s", scanner.Text())
		}
		wg.Done()
	}()

	if err = cmd.Start(); err != nil {
		return err
	}

	wg.Wait()

	return cmd.Wait()
}

Maybe you should use multiwritter:

cmd.Stdout = io.MultiWriter(os.Stdout, &stdout) cmd.Stderr = io.MultiWriter(os.Stderr, &stderr)

func main() {
	cmd := exec.Command("echo", "test")
	err := RunCommanad(cmd)
	if err != nil {
	// handle error
	}
}

func RunCommand(cmd *exec.Cmd) error {
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Run(); err != nil {
		return err
	}

	return nil
}

This is the best solution that has worked for me.