The law was just recently changed, but most cops in NYC have no clue about that. You will still get stopped. I am a Fed in NYC and have been approached about the clip on my pocket more than once in the past few months. NYPD doesn't do such a good job about updating officers on things like law and things that are now legal...
If they can open the knife one handed in any way shape or form and the blade locks, to them its illegal.
And for straight blades, the law says 4", but cops don't carry rulers... I would keep it closer to 3" or under
Play it safe, if you need to carry a knife, carry something that doesn't lock like a Swiss army knife or a simple schrade.
Any spyderco, benchmade or anything that clips to your pocket is going to get noticed and will be a hassle.