Program demonstrating the difference between zombie and orphan processes

procdemo.go

// Program demonstrating the difference between zombie and orphan processes.
//
// BUILDING
//
//     go build procdemo.go
//
// USAGE
//
//     procdemo zombie
//     procdemo orphan
//
// AUTHOR
//
// - J. Brandt Buckley <brandt@runlevel1.com>
//
package main

import (
	"fmt"
	"os"
	"os/exec"
	"time"
)

// zombie executes a command and never checks its exit status.
//
// The sleep process will exit, but will still appear in the process table
// as a zombie until the we exit.
func zombie() {
	cmd := exec.Command("true")
	cmd.Start()

	fmt.Printf("Check out the zombie with:\n\n  ps -lfp %d\n\n", cmd.Process.Pid)
	fmt.Println("Process will remain in the process table until we quit (in 10 min).")

	// Don't exit for a long time so that the zombie sticks around.
	time.Sleep(600 * time.Second)
}

// orphan executes a sleep command and then kills itself.
//
// The sleep process will still be running, but init will become its parent.
func orphan() {
	cmd := exec.Command("sleep", "600")
	cmd.Start()

	fmt.Printf("Check out the orphan with:\n\n  ps -lfp %d\n\n", cmd.Process.Pid)
	fmt.Println("We're going terminate abruptly, but it will continue running until finished (10 min).")

	// Shoot self in the head
	exec.Command("kill", "-9", string(os.Getpid())).Start()
	// NOTE: We're not using the syscall package so this can be cross-compiled.
}

func usage() {
	fmt.Printf("Usage: %s <zombie|orphan>\n", os.Args[0])
}

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Argument required.")
		usage()
		os.Exit(2)
	}

	switch os.Args[1] {
	case "zombie":
		zombie()
	case "orphan":
		orphan()
	case "help", "-h", "--help":
		usage()
	default:
		fmt.Println("Invalid command.")
		usage()
		os.Exit(2)
	}
}