Fix

lib/gratan/identifier/auto.rb

@@ -1,12 +1,13 @@
 class Gratan::Identifier::Auto
   def initialize(output, options = {})
+    @output = output
     @options = options
 
     unless @options[:dry_run]
       if output == '-'
         @output = $stdout
       else
-        @output = open(output, 'w')
+        @output = output
       end
     end
 
@@ -32,9 +33,21 @@ def mkpasswd(len = 8)
   end
 
   def puts_password(user, host, password)
-    if @output
-      @output.puts("#{user}@#{host},#{password}")
-      @output.flush
+    open_output do |f|
+      f.puts("#{user}@#{host},#{password}")
+    end
+  end
+
+  def open_output
+    return if @options[:dry_run]
+
+    if @output == '-'
+      yield($stdout)
+      $stdout.flush
+    else
+      open(@output, 'a') do |f|
+        yield(f)
+      end
     end
   end
 end