Go系统命令管道操作

go 执行系统命令时不能直接使用管道符 |

实现方法如下：

方法一（同步）

func sync() {
	cmd1 := exec.Command("ls", ".")
	cmd2 := exec.Command("grep", "go")
	cmd2.Stdout = os.Stdout
	in, _ := cmd2.StdinPipe()
	cmd1.Stdout = in
	cmd2.Start()
	cmd1.Run()
	in.Close()
	cmd2.Wait()
}

方法二（异步）

func async() {
	cmd1 := exec.Command("ls", ".")
	cmd2 := exec.Command("grep", "go")
	cmd2.Stdout = os.Stdout
	out, _ := cmd1.StdoutPipe()
	in, _ := cmd2.StdinPipe()
	go func() {
		defer func() {
			out.Close()
			in.Close()
		}()
		io.Copy(in, out)
	}()
	cmd1.Run()
	cmd2.Run()
}

方法三（串联）

func main() {
	cmd1 := exec.Command("ls", ".")
	cmd2 := exec.Command("grep", "go")
	cmd3 := exec.Command("grep", "main")
	cmd3.Stdout = os.Stdout
	pipe(cmd1, cmd2, cmd3)
	cmd1.Run()
	cmd2.Run()
	cmd3.Run()
}

func pipe(cmds ...*exec.Cmd) {
	for i, cmd := range cmds[1:] {
		out, _ := cmds[i].StdoutPipe()
		in, _ := cmd.StdinPipe()
		go func() {
			defer func() {
				out.Close()
				in.Close()
			}()
			io.Copy(in, out)
		}()
	}
}