Not sure what you are really wanting to know. Yes, you can cut the carpet with a knife.

Thanks PPF. I want to know if there's a special way or tool that I can use to cut it cleanly.

This is the type of question easily answered via a google search. You will find links to videos as well.

Also the type of question your local ACE Hardware people could answer, and sell you the tools needed.

Briefly, you need a knife (google "carpet knife") and a straight edge -- something flat and stiff to run the knife along. Be careful not to cut too deep scarring the floor.

Thanks :)