How to extract verbs,nouns from a text file

This is a simple question that calls for a big answer. It is the area of Natural Language Processing (NLP), an AI field of studies overarching intersection of linguistic with computer science. Simply put it, how to make machines understand human (natural) languages. Initially, it started with hard-coded rule-based (grammars) machine learning which requires knowledge of the language concerned and large linguistic resources such as dictionary; it then moved on to statistical approaches where some sort of similarity measures are used to infer the meaning and closeness of texts. It is an active research areas. In my opinion, it is not feasible in the near future.