Australia's largest retailer Woolworths posted first-half net profit up 6 per cent as its core supermarkets business outperformed weaker discretionary retail units. It also announced it will buy direct wine marketer Cellarmasters from private equity firm Archer Capital for $340 million. Woolworths, which also owns discounter Big W and electronics chain Dick Smith, said net profit before one-offs rose to $1.16 billion, from $1.095 billion a year earlier.