What can I expect form the Indian Railways pantry and catering services?
In general the food is adequate, should be taken sparenly. You will be served standard Thali meals often cooked in the Pantry carraige especially for you. Typically includes rice, dal, some veg curry perhaps with paneer. Roti or chapti may be offered at an extra cost. The food is a set price: 35Rs Thali, 10Rs water.
Regional variety may vary with snakes from samosa, fried bread pokara, to south India idly and vada.
You should be wary of outside sellers that may hop onto the train to sell food or other items. These may or may not be of good qulaity. Stick to fruit or nuts, things you can peel and check the over all quality of before you eat it.