R Ashwin's five-wicket haul helped India dismiss South Africa for just 184, in their first innings, to hand the hosts a slender 17-run lead in the first Test being played in Mohali on Friday.
The off spinner made the most of a dry pitch that was showed signs of crumbling on day two. India's spinners, Ashwin and Ravindra Jadeja, struggled to find their rhythm in the morning session.
Dean Elgar and Hashim Amla looked comfortable and added 76 for the third wicket, before Elgar tried to slog Ashwin, only to be caught at backward point.
Elgar's dismissal lifted India's spirits and the bowlers started to find momentum. Ashwin then deceived Amla in the flight, as he came down the crease, only to be stumped by Wriddhiman Saha for 43. South Africa at that stage stood at 105 for four.
AB de Villiers kept India's attack at bay and scored freely in his breezy 83-ball 63. But a quicker delivery by Amit Mishra breached de Villiers' defences and he fell.
His departure proved costly for the tourists, as the remaining six batsmen managed just 26 runs between them. Ashwin was instrumental in handing his side the advantage. He claimed the wicket of Dane Villas and Imran Tahir to complete his fifer.
India's spinners dominated proceedings on the second day. Ravindra Jadeja ended with figure of 3 for 55 and Amit Mishra 2 for 35. Ashwin, in the process, became the fastest Indian bowler to the 150-mark.
India's opener, Shikhar Dhawan's, woeful run continued in the second innings, as he was dismissed in the third over for zero. Cheteshwar Pujara and Murali Vijay steadied their innings and added 86 runs for the second wicket. Vijay fell before the end of play, but India ended the day with the advantage of a 142-run lead.