package main

import (
	"fmt"
	"os"
	"strconv"
	"syscall"
	"time"
)

func printIds(ii int) {
	for {
		fmt.Printf(
			"gorutine %d: uid=%d euid=%d gid=%d egid=%d\n", ii,
			syscall.Getuid(), syscall.Geteuid(),
			syscall.Getgid(), syscall.Getegid(),
		)
		time.Sleep(1e9)
	}
}

func main() {
	if len(os.Args) != 3 {
		fmt.Printf("Usage: %s UID GID\n", os.Args[0])
		os.Exit(1)
	}
	uid, err := strconv.Atoi(os.Args[1])
	if err != nil {
		fmt.Println("Wrong UID:", err)
		os.Exit(1)
	}
	gid, err := strconv.Atoi(os.Args[2])
	if err != nil {
		fmt.Println("Wrong GID:", err)
		os.Exit(1)
	}

	for ii := 1; ii < 10; ii++ {
		go printIds(ii)
		time.Sleep(1e8)
	}

	if err := os.Setgid(gid); err != nil {
		fmt.Println("Setgid error:", err)
		os.Exit(1)
	}

	if err := os.Setuid(uid); err != nil {
		fmt.Println("Setuid error:", err)
		os.Exit(1)
	}

	printIds(0)
}