Update msh.c

fix msh_exec(char* cmd, rt_size_t length) bug

components/finsh/msh.c

@@ -257,16 +257,29 @@ int msh_exec(char* cmd, rt_size_t length)
 	int cmd0_size = 0;
     cmd_function_t cmd_func;
 
+	while(*cmd  == ' ') 
+	{
+		cmd++;
+		length--;
+	}
 	while ((cmd[cmd0_size] != ' ' && cmd[cmd0_size] != '\t') && cmd0_size < length)
 		cmd0_size ++;
-
+	
 	/* try to get built-in command */
+	if (cmd0_size == 0) return -1;
 	cmd_func = msh_get_cmd(cmd, cmd0_size);
 	if (cmd_func == RT_NULL)
 	{
 #ifdef RT_USING_MODULE
 		msh_exec_module(cmd, length);
 #else
+		argv[0] = cmd;
+		while(*cmd != ' ')
+		{
+			if (*cmd == 0) break;
+			cmd++;
+		}
+		if (*cmd == ' ') *cmd = 0;
 		rt_kprintf("%s: command not found.\n", argv[0]);
 #endif
 		return -1;