Customize a new rake task in rails

Refer to lib/task/*.rake 

Arguments can be passed by using of ENV.

e.g.

desc "create csv of loan ledgers: LEDGERS_START_DATE=2011-07-01 LEDGERS_END_DATE=2011-12-31 rake adhoc:ledgers"
task :ledgers => :environment do
Adhocs.create_csv_of_loan_ledgers(ENV['LEDGERS_START_DATE'], ENV['LEDGERS_END_DATE'])
end