added watcher functionality

README.md

@@ -4,7 +4,7 @@
 
 # Clipboard for Go
 
-Provide copying and pasting to the Clipboard for Go.
+Provide copying, pasting and monitoring clipboard functionality for Go.
 
 Build:
 
@@ -26,10 +26,6 @@ Notes:
 * Text string only
 * UTF-8 text encoding only (no conversion)
 
-TODO:
-
-* Clipboard watcher(?)
-
 ## Commands:
 
 paste shell command:

clipboard.go

@@ -5,6 +5,10 @@
 // Package clipboard read/write on clipboard
 package clipboard
 
+import (
+	"time"
+)
+
 // ReadAll read string from clipboard
 func ReadAll() (string, error) {
 	return readAll()
@@ -15,6 +19,31 @@ func WriteAll(text string) error {
 	return writeAll(text)
 }
 
+// Monitor starts monitoring the clipboard for changes. When
+// a change is detected, it is sent over the channel.
+func Monitor(interval time.Duration, stopCh <-chan struct{}, changes chan<- string) error {
+	defer close(changes)
+
+	currentValue, err := ReadAll()
+	if err != nil {
+		return err
+	}
+
+	for {
+		select {
+		case <-stopCh:
+			return nil
+		default:
+			newValue, _ := ReadAll()
+			if newValue != currentValue {
+				currentValue = newValue
+				changes <- currentValue
+			}
+		}
+		time.Sleep(interval)
+	}
+}
+
 // Unsupported might be set true during clipboard init, to help callers decide
 // whether or not to offer clipboard options.
 var Unsupported bool

cmd/monitor/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"log"
+	"time"
+
+	"github.com/spy16/clipboard"
+)
+
+func main() {
+	changes := make(chan string, 10)
+	stopCh := make(chan struct{})
+
+	go clipboard.Monitor(time.Second, stopCh, changes)
+
+	// Watch for changes
+	for {
+		select {
+		case <-stopCh:
+			break
+		default:
+			change, ok := <-changes
+			if ok {
+				log.Printf("change received: '%s'", change)
+			} else {
+				log.Printf("channel has been closed. exiting..")
+			}
+		}
+	}
+}