Practical application of Finite State Machines I am looking for practical applications of Finite State Machines like DFA, NFA, Moore, Mealy machines...

It would be helpful if someone point to examples from Linux Kernel. I know that DFA is used in string matching like KMP algorithm.

What is the significance of NFA, Moore and Mealy machines?
Each time you do a search (particularly a "pattern search") in your favorite editor/tool, the pattern is translated into some form of finite state machine, which does the matching.

The lexical analysis part of your compiler/interpreter (yes, even your shell) is again a finite automaton which matches keywords and other tokens recognized by the language.

Any vending machine is a finite automaton which takes in coins of different denominations and recognizes when the correct amount has been entered (OK, today's vending machines probably have a small CPU inside doing the adding, but the end result is the same).