RAM Disk function using Mbed os5 standard library

Please refer following my Notebook page.
/users/kenjiArai/notebook/sd-card-control-new/#

Revision:
1:58fc0cbd9a41
Parent:
0:308d4fafaafb
Child:
4:6650958e6eae
--- a/FatFs_Mon/mon.h	Sat Apr 07 01:41:49 2018 +0000
+++ b/FatFs_Mon/mon.h	Thu Dec 26 05:29:38 2019 +0000
@@ -2,14 +2,15 @@
  * mbed Application program for the mbed
  *  FatFs Check program /monitor part
  *
- * Copyright (c) 2015,'18 Kenji Arai / JH1PJL
+ * Copyright (c) 2015,'18,'19 Kenji Arai / JH1PJL
  *  http://www.page.sannet.ne.jp/kenjia/index.html
  *  https://os.mbed.com/users/kenjiArai/
  *      Created:    May        5th, 2015
  *      Revised:    June      14th, 2015
- *      Revised:    April      7th, 2018
+ *      Revised:    December  24th, 2019
  */
 
 //  Function prototypes --------------------------------------------------------
 void mon(void);
 uint32_t get_disk_freespace(void);
+uint32_t get_data_file_size(const char *const file_name);