tailpipe uses 'tail -f' to read a file, and spits out the result over EventSource to whoever's listening.

tailpipe.go

package main

import (
	eventsource "github.com/msgehard/goEventSource"
	"encoding/json"
	"net/http"
	"os/exec"
	"flag"
	"log"
	// "fmt"
)

type Message struct {
	Body string
}

func makeHandler(c <-chan string, quit <-chan bool) func(*eventsource.Conn) {
	return func(es *eventsource.Conn) {
		log.Println("Client listening.")
		for {
			select {
			case msg := <-c:
				log.Printf("length of msg is: %d", len(msg))
				m := Message{msg}
				j, _ := json.Marshal(m)
				es.Write(string(j))
			case <-quit:
				log.Println("tail died!")
				return
			case <-es.CloseNotify():
				log.Println("Client abandoned us.")
				return
			}
		}
	}
}

func main() {
	flag.Parse()
	filename := flag.Arg(0)

	tail := exec.Command("tail", "-f", filename)
	tailStdout, err := tail.StdoutPipe()
	if err != nil {
		log.Fatal("can't start tail. better bail!")
		return
	}

	if err := tail.Start(); err != nil {
		log.Fatal("can't start tail. gotta bail!")
		return
	}

	b := make([]byte, 1024)
	c := make(chan string)
	quit := make(chan bool)

	go func() {
		for {
			n, _ := tailStdout.Read(b)
			if n > 0 {
				c <- string(b[:n])
			}
		}
	}()

	http.Handle("/events", eventsource.Handler(makeHandler(c, quit)))
	http.Handle("/", http.FileServer(http.Dir("/home/clee/Public/tailpipe")))

	go tail.Wait()

	http.ListenAndServe(":8000", nil)
}