save: Create temporary file first before overwriting the target file

internal/buffer/save.go

@@ -31,9 +31,10 @@ func overwriteFile(name string, enc encoding.Encoding, fn func(io.Writer) error,
 	var writeCloser io.WriteCloser
 	var screenb bool
 	var cmd *exec.Cmd
+	tmpName := name + ".tmp"
 
 	if withSudo {
-		cmd = exec.Command(config.GlobalSettings["sucmd"].(string), "dd", "bs=4k", "of="+name)
+		cmd = exec.Command(config.GlobalSettings["sucmd"].(string), "dd", "bs=4k", "of="+tmpName)
 
 		if writeCloser, err = cmd.StdinPipe(); err != nil {
 			return
@@ -54,7 +55,7 @@ func overwriteFile(name string, enc encoding.Encoding, fn func(io.Writer) error,
 			screen.TempStart(screenb)
 			return err
 		}
-	} else if writeCloser, err = os.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666); err != nil {
+	} else if writeCloser, err = os.OpenFile(tmpName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666); err != nil {
 		return
 	}
 
@@ -79,10 +80,34 @@ func overwriteFile(name string, enc encoding.Encoding, fn func(io.Writer) error,
 	if withSudo {
 		// wait for dd to finish and restart the screen if we used sudo
 		err := cmd.Wait()
+		if err != nil {
+			screen.TempStart(screenb)
+			return err
+		}
+
+		cmd = exec.Command(config.GlobalSettings["sucmd"].(string), "mv", tmpName, name)
+
+		c := make(chan os.Signal, 1)
+		signal.Notify(c, os.Interrupt)
+		go func() {
+			<-c
+			cmd.Process.Kill()
+		}()
+
+		if e := cmd.Start(); e != nil && err == nil {
+			screen.TempStart(screenb)
+			return err
+		}
+
+		err = cmd.Wait()
 		screen.TempStart(screenb)
 		if err != nil {
 			return err
 		}
+	} else {
+		if err == nil {
+			err = os.Rename(tmpName, name)
+		}
 	}
 
 	return