Subreaper reaping main

subreaper_reaping_main.go

package main

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

  "github.com/williammartin/subreaper"
  "golang.org/x/sys/unix"
)

func main() {
  switch os.Args[1] {
  case "run":
    parent()
  case "child":
    child()
  case "grandchild":
    grandchild()
  default:
    panic("You must pass an argument")
  }
}

func parent() {
  must(subreaper.Set())

  isSubreaper, err := subreaper.IsSubreaper()
  mustNot(err)

  fmt.Printf("Is this process a subreaper?: %t\n", isSubreaper)

  cmd := exec.Command("/proc/self/exe", "child")
  must(cmd.Run())

  sigs := make(chan os.Signal, 1)
  signal.Notify(sigs, unix.SIGCHLD)

  <-sigs
  var status unix.WaitStatus
  pid, err := unix.Wait4(-1, &status, unix.WNOHANG, nil)
  mustNot(err)

  fmt.Printf("Grandchild pid %d exited\n", pid)
}

func child() {
  cmd := exec.Command("/proc/self/exe", "grandchild")
  must(cmd.Start())
}

func grandchild() {
  time.Sleep(time.Second * 20)
}

func must(err error) {
  if err != nil {
    panic(err)
  }
}

func mustNot(err error) {
  must(err)
}