如何通过从键盘获取任何值来打破Linux上的C循环？

The program I am building runs in an infinite while loop with a switch case in it. I want to insert a while loop under each case and perform few operations in the loop, but the loop should exit as soon as a keyboard input is given. So that after taking the input from keyboard another case is run with the nested while loop in it, and the process continues.The program I am building runs in an infinite w