Simple example of using named pipes in go for IPC

named_pipes_test.go

import (
	"os"
	"os/exec"
	"path"
	"syscall"
	"testing"
	"time"
)

func TestFifo(t *testing.T) {
	pipeName := path.Join(os.TempDir(), "testpipe-*")
	err := syscall.Mkfifo(pipeName, 0660)
	if err != nil {
		t.Fatal(err)
	}
	defer os.Remove(pipeName)

	cmd := exec.Command("cat", pipeName)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	// We have to open the reading process before attempting to open the pipe for writing (below) -
	// Otherwise the open will wait infinitely for a reader to connect to the other end, since we open the pipe
	// in blocking mode (os.O_WRONLY)
	err = cmd.Start()
	if err != nil {
		t.Fatal(err)
	}

	pipe, err := os.OpenFile(pipeName, os.O_WRONLY, 0660|os.ModeNamedPipe)
	defer pipe.Close()
	if err != nil {
		t.Fatal(err)
	}

	writeToPipe(t, pipe, "1\n")
	time.Sleep(time.Second)
	writeToPipe(t, pipe, "2\n")
	time.Sleep(time.Second)
	writeToPipe(t, pipe, "3\n")
	time.Sleep(time.Second)

	err = pipe.Close()
	if err != nil {
		t.Fatal(err)
	}

	err = cmd.Wait()
	if err != nil {
		t.Fatal(err)
	}
}

func TestNonblockingFifo(t *testing.T) {
	pipeName := path.Join(os.TempDir(), "testpipe-*")
	err := syscall.Mkfifo(pipeName, 0660)
	if err != nil {
		t.Fatal(err)
	}
	defer os.Remove(pipeName)

	cmdTimeout, cancelCmd := context.WithTimeout(context.Background(), time.Second * 10)
	defer cancelCmd()
	cmd := exec.CommandContext(cmdTimeout, "cat", pipeName)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	writeTimeout, cancelWrite := context.WithTimeout(context.Background(), time.Second)
	defer cancelWrite()
	go func() {
		var pipe *os.File
		var err error
		for pipe == nil && err == nil {
			select {
			case <-writeTimeout.Done():
				t.Fatal("timeout")
			default:
				pipe, err = os.OpenFile(pipeName, os.O_WRONLY|syscall.O_NONBLOCK, 0660|os.ModeNamedPipe)
				if asPathErr, ok := err.(*os.PathError); ok {
					if asPathErr.Unwrap() == syscall.ENXIO {
						fmt.Println("pipe not open yet")
						err = nil
					}
				}
			}
		}
		if err != nil {
			cancelCmd()
			t.Fatal(err)
		}
		fmt.Println("Pipe opened!")
		defer pipe.Close()

		writeToPipe(t, pipe, "1\n")
		time.Sleep(time.Second)
		writeToPipe(t, pipe, "2\n")
		time.Sleep(time.Second)
		writeToPipe(t, pipe, "3\n")
		time.Sleep(time.Second)

		err = pipe.Close()
		if err != nil {
			cancelCmd()
			t.Fatal(err)
		}
	}()

	err = cmd.Start()
	if err != nil {
		t.Fatal(err)
	}

	err = cmd.Wait()
	if err != nil {
		t.Fatal(err)
	}
}

func writeToPipe(t *testing.T, file *os.File, arg string) {
	_, err := file.WriteString(arg)
	if err != nil {
		t.Fatal(err)
	}
	return
}