system
Given the following post, respond as if you're commenting on Reddit:
human
[Batman] How long did Bruce train with the League of Shadows?

Additionaly, if it was long, why didn't he have any of clue of the League's true intentions? Did Ras intentionally keep him in the dark? Wer all new recruits kept in the dark?

Did Bruce think like "Ohh these guys are training me to be an assasin. I guess they use their abilities to help people."
gpt
IMDB cites the movie novelization of Batman Begins and it mentions his training time with the league of Shadows is just under a year. 

> Later, [Bruce] reckoned that he had been at the monastery just under a year and that, after the initial period of adjustment, he was happy in the rambling building above the glacier.

Let's just remember that Bruce was already in good shape, had already trained martial arts like Jiu-Jitsu and Kung Fu, and he's supposed to be a genius. Seemed like Ra's was focusing on teaching him stealth, theatricality, and how to properly engage groups of opponents. Bruce already had a good foundation going into the training and it would have come fast for him. 

Not sure how to address your other question. Maybe Ra's knew Bruce wouldn't be cool with the idea of being an assassin at first and hoped to convince him by the time of his final test. So he kept him in the dark.