I would like to get my self into automation, I know there are a few programming language available such as XLST, SLAX, PYTHON. I want to know and use only one language, so want to focus on only one language. what is the most popular language used in big companies ? If you would recommand one powerfull programming language which is widely used what would be your recommandation ?
If you only want to learn one: Python
Reality is more than one is needed:
I concur with @asharp on python and the fact that more than one is needed.
If you understand the concepts behind writing software, the constructs therein, structuring your code appropriately and documenting it, then learning the syntax and structure of different languages is fairly easy.