jiangyds_code_example.go

package main

import (
	"bytes"
	"fmt"
	"os/exec"
	"sync"
)

func main() {
	wg := new(sync.WaitGroup)
	for i := 0; i < 2500; i++ {
		wg.Add(1)
		go func(i int) {
			var b bytes.Buffer
			fmt.Println("Starting sleep ", i, "...")
			cmd := exec.Command("sleep", "3600")
			cmd.Stdout = &b
			go func() {
				output := make([]byte, 100)
				_, err := b.Read(output)
				if err != nil {
					fmt.Println(i, "says ", string(output))
				} else {
					fmt.Println(i, "error ", err)
				}
				cmd.Wait()
				wg.Done()
			}()
			err := cmd.Start()
			if err != nil {
				panic(err)
			}
			fmt.Println("Finishing sleep ", i, "...")
		}(i)
	}
	fmt.Println("Waiting for WaitGroup ...")
	wg.Wait()
	fmt.Println("WaitGroup finished!")
}

Running it:

$ ulimit -n 10000
$ go run jiangyds_code_example.go

... and checking number of threads in another terminal:

$ ps -eLf | grep jiangyds_code_example | wc -l
2835