add watcher

Adds the ability to watch a directory for changes and run a command
when changes are spit out

glide.lock

@@ -1,6 +1,8 @@
-hash: af0c2b0e7fd58c70a43dcf5c75b802f7a49c5d53ad6aec1975adfebe0acee206
-updated: 2017-02-04T09:25:07.785352554-07:00
+hash: aa963bb1783c6d48ae4d7001851c87e2abb46cfbcdfd8a4792dbe766b7fafcd3
+updated: 2017-02-27T10:22:14.549716708-07:00
 imports:
+- name: github.com/fsnotify/fsnotify
+  version: 629574ca2a5df945712d3079857300b5e4da0236
 - name: github.com/gorilla/feeds
   version: 441264de03a8117ed530ae8e049d8f601a33a099
 - name: github.com/russross/blackfriday

glide.yaml

@@ -4,3 +4,5 @@ import:
   version: ~1.4.0
 - package: github.com/ylih/extrasys
 - package: github.com/gorilla/feeds
+- package: github.com/fsnotify/fsnotify
+  version: ^1.4.2

main.go

@@ -2,17 +2,20 @@ package main
 
 import (
 	"bufio"
+	"flag"
 	"fmt"
 	"html/template"
 	"io/ioutil"
 	"log"
 	"os"
+	"os/exec"
 	"path"
 	"regexp"
 	"sort"
 	"strings"
 	"time"
 
+	"github.com/fsnotify/fsnotify"
 	. "github.com/gorilla/feeds"
 	"github.com/russross/blackfriday"
 	// "github.com/ylih/extrasys"
@@ -259,6 +262,13 @@ func main() {
 	var err error
 	// extrasys.Pledge("stdio wpath rpath cpath", nil)
 
+	var watch = flag.Bool("w", false, "Enable 'watch' mode. Requires 'wdir' and 'wcmd'.")
+	var watchDir = flag.String("wdir", "", "watch a directory for changes, run command when change happens.")
+	var watchCmd = flag.String("wcmd", "", "command to run when changes are detected in 'wdir'.")
+
+	flag.Parse()
+
+	if !*watch {
 		if len(os.Args) < 2 {
 			fmt.Println("Wrong number of arguments")
 			os.Exit(1)
@@ -362,4 +372,37 @@ func main() {
 
 		feed.WriteAtom(atomFile)
 		feed.WriteRss(rssFile)
+	} else {
+		// Watch mode
+		watcher, err := fsnotify.NewWatcher()
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer watcher.Close()
+
+		done := make(chan bool)
+		go func() {
+			for {
+				select {
+				case event := <-watcher.Events:
+					if event.Op&fsnotify.Write == fsnotify.Write {
+						log.Println("modified file:", event.Name)
+						c := exec.Command(*watchCmd)
+
+						if err := c.Run(); err != nil {
+							fmt.Println("Error: ", err)
+						}
+					}
+				case err := <-watcher.Errors:
+					log.Fatal(err)
+				}
+			}
+		}()
+
+		err = watcher.Add(*watchDir)
+		if err != nil {
+			log.Fatal(err)
+		}
+		<-done
+	}
 }