How to execute 'top' Command output using Golang

I want to write the 'top' command's output to another file. But when I tried it with the below code, I get the below error:

'exit status 1'.

Here is my code:

package main

import "os/exec"

func main() {
    app := "top"
	cmd := exec.Command(app)
    stdout, err := cmd.Output()

    if err != nil {
	    println(err.Error())
	    return
    }

    print(string(stdout))
}

Any help is greatly appreciated. Thanks in advance.

From man page for "top", -b option is good for sending output to another program (no color, no anything) as plain text, and -n is the number of frame it will iterate before stopping. Without -n it will iterate infinite time.

 func main() {
      app := "top"
      arg0 := "-b"
      arg1 := "-n"
      arg2 := "1"
    
      cmd := exec.Command(app, arg0, arg1, arg2)
      stdout, err := cmd.Output()
    
      if err != nil {
    	println(err.Error())
    	return
      }
    
      print(string(stdout))
    }

s := fmt.Sprintf(`"top -bn2 | fgrep 'Cpu(s)' | tail -1"`, host)
log.Printf("top = %s\n", s)
cmd := exec.Command("bash", "-c", s)
b, e := cmd.Output()
if e != nil {
	log.Printf("failed due to :%v\n", e)
	panic(e)
}
log.Printf("%v\n", string(b))
raw := string(b)

This is what you could potentially do if you are planning to run top in batch mode. Note tail -1 maybe of value if you wanted to pick last one instead of capturing everything, and fgrep useful if you are to grep for a specific fields - however it is not necessary.

For reference, here are other ways to run top.

c := exec.Command("top")
c.Stdin = os.Stdin
c.Stdout = os.Stdout
c.Stderr = os.Stderr
c.Run()

This is for local. If you are looking via ssh, use this -

c := exec.Command("ssh", "-t", "localhost", "top")
c.Stdin = os.Stdin
c.Stdout = os.Stdout
c.Stderr = os.Stderr
c.Run()

If you want to start a server, and connect as a client via telnet and show on telnet screen result of top command (common case when running top remotely using a go introspecting server perhaps) use this -

<pre>
<code>

func main() {
	l, _ := net.Listen("tcp", "127.0.0.1:12345")
	for {
		c, _ := l.Accept()
		go func() {
			handle(&c)
		}()
	}
}
func handle(c *net.Conn) {
	cmd := exec.Command("top")
	cstdout, _ := cmd.StdoutPipe()
	go io.Copy(bufio.NewWriter(*c), bufio.NewReader(cstdout))
	cmd.Run()
}

</code>
</pre>

If you are building a terminal using telnet and ssh to run generic commands like app use this library - https://github.com/kr/pty

Edit Going to make it better ... here's an example that works for PTY, scenario is if you use ssh -t to run a command want to interact with telneting from this server type setup e.g. top use this :

<pre>
<code>

   cmd := exec.Command("ssh", "-t", "localhost", "top")
	f, _ := pty.Start(cmd)
	go io.Copy(bufio.NewWriter(*c), f)
	go io.Copy(f, bufio.NewReader(*c))
	go io.Copy(bufio.NewWriter(*c), os.Stdin)
	cmd.Run()

</code>
</pre>