ensure the watcher has started before we read

tail.go

@@ -250,6 +250,11 @@ func (tail *Tail) tailFileSync() {
 
 	tail.openReader()
 
+	if err := tail.watchChanges(); err != nil {
+		tail.Killf("Error watching for changes on %s: %s", tail.Filename, err)
+		return
+	}
+
 	var offset int64
 	var err error
 
@@ -331,19 +336,29 @@ func (tail *Tail) tailFileSync() {
 	}
 }
 
-// waitForChanges waits until the file has been appended, deleted,
-// moved or truncated. When moved or deleted - the file will be
-// reopened if ReOpen is true. Truncated files are always reopened.
-func (tail *Tail) waitForChanges() error {
-	if tail.changes == nil {
+// watchChanges ensures the watcher is running.
+func (tail *Tail) watchChanges() error {
+	if tail.changes != nil {
+		return nil
+	}
+	var pos int64
+	var err error
+	if !tail.Pipe {
 		pos, err := tail.file.Seek(0, os.SEEK_CUR)
 		if err != nil {
 			return err
 		}
-		tail.changes, err = tail.watcher.ChangeEvents(&tail.Tomb, pos)
-		if err != nil {
-			return err
-		}
+	}
+	tail.changes, err = tail.watcher.ChangeEvents(&tail.Tomb, pos)
+	return err
+}
+
+// waitForChanges waits until the file has been appended, deleted,
+// moved or truncated. When moved or deleted - the file will be
+// reopened if ReOpen is true. Truncated files are always reopened.
+func (tail *Tail) waitForChanges() error {
+	if err := tail.watchChanges(); err != nil {
+		return err
 	}
 
 	select {