As you have asked about the curriculum for IAS exam, check below for the information

The Civil Services Examination consists of two successive stages:
(I) Civil Services Preliminary Examination; and
Civil Services Main Exam (Written & Interview) for selection of applicants

The Preliminary Examination consists of two papers with multiple choice questions.
Both the papers are of 200 marks each (total 400 marks), this exam is planned to serve as a screening test only. In the CSAT or Paper-II of Preliminary Exam, that is the General Studies – II, the applicant will have to score a minimum 33% of marks for qualifying in Mains (written).

The syllabus for Pre Exams Paper-I includes mainly the current affairs for which the applicants have to update themselves with the national and international happenings all over.
Syllabus of Paper I - (200 marks) Duration: Two hours

Current events of national and international importance
History of India and Indian National Movement
Indian and World Geography - Physical, Social, Economic Geography of India and the World
Indian Polity and Governance - Constitution, Political System, Panchayati Raj, Public Policy, Rights Issues,
Economic and Social Development - Sustainable Development, Poverty, Inclusion, Demographics, Social Sector initiatives,
General issues on Environmental Ecology, Bio-diversity and Climate Change - that do not require subject specialisation General Science

Syllabus for Paper II-(200 marks) Duration: Two hours

Comprehension
Interpersonal skills including communication skills;
Logical reasoning and analytical ability
Decision-making and problem-solving
General mental ability
Basic numeracy (numbers and their relations, orders of magnitude,) (Class X level), Data interpretation (charts, graphs, tables, data sufficiency etc. - Class X level)