main.go

package main
import (
	"bytes"
	"io"
	"log"
	"os"
	"os/exec"
)


func main() {
	switch os.Args[1] {
	case "buffer":
		// FAILS
		doBuffers()
	case "stdio":
		// WORKS
		doStdio()
	case "pipe":
		// WORKS
		doPipe()
	case "startpipe":
		// FAILS
		doStartPipe()
	case "file":
		// WORKS
		doFile()
	}
}

func doBuffers() {
	cmd := exec.Command("/usr/bin/runc", "create", "echo")
	cmdStdout := &bytes.Buffer{}
	cmdStderr := &bytes.Buffer{}

	cmd.Stdout = cmdStdout
	cmd.Stderr = cmdStderr

	cmd.Run()
	os.Stdout.Write(cmdStdout.Bytes())
	os.Stderr.Write(cmdStderr.Bytes())
	log.Printf("Done buffers")

}

func doStdio() {
	cmd := exec.Command("/usr/bin/runc", "create", "echo")
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	cmd.Run()
	log.Printf("Done stdio")
}

func doPipe() {
        cmd := exec.Command("/usr/bin/runc", "create", "echo")
        outPipe, err := cmd.StdoutPipe()
        if err != nil {
                log.Fatalf("Could not get stdout pipe")
        }
        errPipe, err := cmd.StderrPipe()
        if err != nil {
                log.Fatalf("Could not get stderr pipe")
        }

        cmd.Run()
        io.Copy(os.Stdout, outPipe)
        io.Copy(os.Stderr, errPipe)
        log.Printf("Done pipes")
}

func doStartPipe() {
        cmd := exec.Command("/usr/bin/runc", "create", "echo")
        outPipe, err := cmd.StdoutPipe()
        if err != nil {
                log.Fatalf("Could not get stdout pipe")
        }
        errPipe, err := cmd.StderrPipe()
        if err != nil {
                log.Fatalf("Could not get stderr pipe")
        }

        cmd.Start()
        io.Copy(os.Stdout, outPipe)
        io.Copy(os.Stderr, errPipe)
	cmd.Wait()
        log.Printf("Done startpipes")
}

func doFile() {
	fStdout, err := os.OpenFile("/tmp/stdout.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
	if err != nil {
		log.Fatalf("Error opening stdout log file: %v", err)
	}
	defer fStdout.Close()
	fStderr, err := os.OpenFile("/tmp/stderr.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
	if err != nil {
		log.Fatalf("Error opening stderr log file: %v", err)
	}
	defer fStderr.Close()

	cmd := exec.Command("/usr/bin/runc", "create", "echo")

	cmd.Stdout = fStdout
	cmd.Stderr = fStderr

	cmd.Run()
	log.Printf("Done files to /tmp/stdout.log and /tmp/stderr.log")

}