I just got a law degree in India. I have not yet appeared for the bar exam. How soon can I become a lawyer in UK?

What makes you think you can become a lawyer in the UK? Indian law is different from English law, even if both countries have common law systems, so your knowledge of Indian law will be next to useless in the UK. And even if *you* think you're qualified to practice law in the UK, very few clients would share that view, which means that you would struggle to do any work here, especially as UK law firms would have little interest in hiring a lawyer who is always going to be difficult to 'sell' to a client.

The other thing is, do you have the right to live and work in the UK, eg. are you a British citizen? If not, then you will never get a work permit here as a lawyer, especially a rookie one, as there is more than enough home-grown legal talent in this country and therefore no need to import more.

But let's assume you have the legal status to live and work here, and let's further assume you can demonstrate relevant knowledge of English and/or Scottish law, then in answer to your question, you will need to go through a one-year-course called Legal Practice Course (for would-be solicitors) or Bar Professional Training Course (for barristers), followed by a traineeship/pupillage lasting typically a couple of years. So it would be at least 2-3 years before you could practice law.

Answer this. what do you know about family law in the UK.
Criminal law
Motoring offences
Murder
Manslaughter.
Property law.

Any of it ,? if the answer is nothing then you won't be practising here.

You cannot become a lawyer (solicitor) in UK. There are NO employment visas for solicitors. NO shortage of UK citizens who hold law degrees from British universities, passed UK bar exams, and have been admitted to the bar as solicitors.

You have more studying to go yet. This website might be useful for you.
http://www.chambersstudent.co.uk/where-to-start/qualifying-from-overseas