The Sensex at the Bombay Stock Exchange ended with a marginal gain of 17 points, or 0.1 percent, at 17,767, today, as investors adopted a cautious approach after recent gains and ahead of IIP and inflation data later this week. The Sensex had gained 61 points at the day's high, and shed 22 at the day's low.The Nifty at the National Stock Exchange edged up 5 points, or 0.1 percent, to 5,363.