[DFS] add df cmd in msh and provide better display.

re-write for #1138

components/dfs/src/dfs_fs.c

@@ -540,9 +540,13 @@ FINSH_FUNCTION_EXPORT(mkfs, make a file system);
 int df(const char *path)
 {
     int result;
+    int minor = 0;
     long long cap;
     struct statfs buffer;
 
+    int unit_index = 0;
+    char *unit_str[] = {"KB", "MB", "GB"};
+
     result = dfs_statfs(path ? path : NULL, &buffer);
     if (result != 0)
     {
@@ -551,8 +555,16 @@ int df(const char *path)
     }
 
     cap = buffer.f_bsize * buffer.f_bfree / 1024;
-    rt_kprintf("disk free: %d KB [ %d block, %d bytes per block ]\n",
-    (unsigned long)cap, buffer.f_bfree, buffer.f_bsize);
+    for (unit_index = 0; unit_index < 3; unit_index ++)
+    {
+        if (cap < 1024) break;
+
+        minor = (cap % 1024) * 10 / 1024; /* only one decimal point */
+        cap = cap / 1024;
+    }
+
+    rt_kprintf("disk free: %d.%d %s [ %d block, %d bytes per block ]\n",
+        (unsigned long)cap, minor, unit_str[unit_index], buffer.f_bfree, buffer.f_bsize);
     return 0;
 }
 FINSH_FUNCTION_EXPORT(df, get disk free);

components/finsh/msh_cmd.c

@@ -255,6 +255,29 @@ int cmd_mkfs(int argc, char **argv)
 }
 FINSH_FUNCTION_EXPORT_ALIAS(cmd_mkfs, __cmd_mkfs, format disk with file system);
 
+extern int df(const char *path);
+int cmd_df(int argc, char** argv)
+{
+    if (argc != 2)
+    {
+        df("/");
+    }
+    else 
+    {
+        if ((strcmp(argv[1], "--help") == 0) || (strcmp(argv[1], "-h") == 0))
+        {
+            rt_kprintf("df [path]\n");
+        }
+        else
+        {
+            df(argv[1]);
+        }
+    }
+
+    return 0;
+}
+FINSH_FUNCTION_EXPORT_ALIAS(cmd_df, __cmd_df, disk free);
+
 int cmd_echo(int argc, char** argv)
 {
 	if (argc == 2)