We don't learn specifically what his job was, but at the beginning of Chapter 3, Meursault says, "There was a stack of freight invoices that had piled up on my desk and I had to go through them all." As with everything, Meursault has a relatively apathetic attitude towards his job. He doesn't like or dislike it, he just does it. In order to better understand this you might want to look into Absurdism and Existentialism. His attitude towards promotion is indifferent. When his boss offers him a job in Paris and a chance to travel he says that it doesn't really matter and that his life in Algiers is as good as it would be anywhere else. He didn't see any reason in making a life change when he was already content with things as they were.