用golang启动一个daemon

用golang启动一个daemon

 package main

 import (
     "fmt"
     "log"
     "os"
     "runtime"
     "syscall"
     "time"
 )

 func daemon(nochdir, noclose int) int {
     var ret, ret2 uintptr
     var err syscall.Errno

     darwin := runtime.GOOS == "darwin"

     // already a daemon
     if syscall.Getppid() == 1 {
         return 0
     }

     // fork off the parent process
     ret, ret2, err = syscall.RawSyscall(syscall.SYS_FORK, 0, 0, 0)
     if err != 0 {
         return -1
     }

     // failure
     if ret2 < 0 {
         os.Exit(-1)
     }

     // handle exception for darwin
     if darwin && ret2 == 1 {
         ret = 0
     }

     // if we got a good PID, then we call exit the parent process.
     if ret > 0 {
         os.Exit(0)
     }

     /* Change the file mode mask */
     _ = syscall.Umask(0)

     // create a new SID for the child process
     s_ret, s_errno := syscall.Setsid()
     if s_errno != nil {
         log.Printf("Error: syscall.Setsid errno: %d", s_errno)
     }
     if s_ret < 0 {
         return -1
     }

     if nochdir == 0 {
         os.Chdir("/")
     }

     if noclose == 0 {
         f, e := os.OpenFile("/dev/null", os.O_RDWR, 0)
         if e == nil {
             fd := f.Fd()
             syscall.Dup2(int(fd), int(os.Stdin.Fd()))
             syscall.Dup2(int(fd), int(os.Stdout.Fd()))
             syscall.Dup2(int(fd), int(os.Stderr.Fd()))
         }
     }

     return 0
 }

 func main() {
     daemon(0, 1)
     for {
         fmt.Println("hello")
         time.Sleep(1 * time.Second)
     }

 }