[Q] Get files opened/accessed by the operating system at a particular moment

Is there a way of logging the files accessed by the OS at a particular moment? Specifically, I am trying to get the file(s) that is/are access when a network unlock code is entered. The purpose is to find the location where the unlock code is stored. On older Samsung devices, such as the Galaxy Ace, the unlock code was stored in a file within the /dev folder.