CNC Machine using arduino

Hello every one. Im relatively new here. Im working on a CNC machine. I have previously done the same where I used GRBL shield and I sent my G code using GCode sender. I now want to change how I feed my G code to the GRBL. I want the G code stored in a text file. Then upload the text file on some memory which can be accessed by ATMEGA 238 microcontroller. How can I tell the GRBL software to read the text file and extruct the G codes from the text file and drive the motors using the extructed G codes? I will apreciate any idea on this.

Have you asked your question on some of the CNC forums where people are familiar with using GRBL?

GRBL is a very complex program and if you have to ask here then I reckon modifying GRBL is beyond your current programming knowledge.

...R