信号：操作系统和程序之间初级交流方式

它来自古老的c语言，可以通过man signal查看详情

信号列表：

常用的信号有：

• SIGINT 和 SIGTERM 都是用来终端程序的
• SIGUP: 程序后台挂起

Golang也可以处理信号， 示例如下：

package main

import (
  "fmt"
  "os"
  "os/signal"
  "syscall"
)

func main() {

  // Create the channel where the received
  // signal would be sent. The Notify
  // will not block when the signal
  // is sent and the channel is not ready.
  // So it is better to
  // create buffered channel.
  sChan := make(chan os.Signal, 1)

  // Notify will catch the
  // given signals and send
  // the os.Signal value
  // through the sChan
  signal.Notify(sChan,
    syscall.SIGHUP,
    syscall.SIGINT,
    syscall.SIGTERM,
    syscall.SIGQUIT,
    syscall.SIGKILL)

  // Create channel to wait till the
  // signal is handled.
  exitChan := make(chan int)
  go func() {
    signal := <-sChan
    switch signal {
    case syscall.SIGHUP:
      fmt.Println("The calling terminal has been closed")
      exitChan <- 0

    case syscall.SIGINT:
      fmt.Println("The process has been interrupted by CTRL+C")
      exitChan <- 1

    case syscall.SIGTERM:
      fmt.Println("kill SIGTERM was executed for process")
      exitChan <- 1

    case syscall.SIGKILL:
      fmt.Println("SIGKILL handler")
      exitChan <- 1

    case syscall.SIGQUIT:
      fmt.Println("kill SIGQUIT was executed for process")
      exitChan <- 1
    }
  }()

  code := <-exitChan //here blocked
  os.Exit(code)
}

运行代码，可以看到程序是被block住的:

通过按CTRL + C 发送SIGINT信号给程序, 程序退出