monitoring subprocess status

fork_wait.go

package main

import "fmt"
import "os"
import "syscall"
import "time"

func forkExec() {
	pa := &syscall.ProcAttr{
		Env: os.Environ(),
	}
	pid, err := syscall.ForkExec("subpro", []string{}, pa)
	if err != nil {
		fmt.Println(err)
		forkExec()
	}

	fmt.Printf("Wait4 %d\n", pid)

	var wstatus syscall.WaitStatus
	rusage := &syscall.Rusage{}
	_, err = syscall.Wait4(pid, &wstatus, syscall.WUNTRACED, rusage)
	if err != nil {
		fmt.Printf("Wait4 error: %v\n", err)
	}
	if wstatus.Exited() || wstatus.CoreDump() || wstatus.Signaled() {
		fmt.Printf("pid %d existed\n", pid)
		forkExec()
	}
}

func main() {
	fmt.Println("vim-go")
	go forkExec()
	for {
		fmt.Println("parent")
		time.Sleep(time.Second)
	}
}

subpro.go

package main

import (
	"fmt"
	"math/rand"
	"os"
	"time"
)

func main() {
	f, err := os.OpenFile("log", os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0666)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Fprintf(f, "subpro start")
	rand.Seed(time.Now().UnixNano())
	for {
		fmt.Fprintln(f, "subpro")
		time.Sleep(time.Second)
		r := rand.Intn(5)
		if r == 0 {
			break
		} else if r == 1 {
			os.Exit(-1)
		}
	}
}