How to Assign Random String to 2D Array

The program reads a file which includes one word in every line.After reading random word put random word in a pointer and return the pointer .in main function printf("%s",func("example.txt",str)) it prints different string when the program run.I want to do this in 2d array(20*20) like table,but i could not imagine how to do this.When i print the the function in internal loop,it give me the same word in every loop step