trace appends your file for rake task in rails

While running a rake task in rails 3.1.12 and ruby 1.9.3 ie

rake output:generate_files["abc"] --trace>>test1.txt

rake task is working fine , but the test1.txt is being appended when this rake task is executed again.

So I would like to know whether there is a method so that each time this rake task is executed it overwrites my test1.txt so that i need not clear this file again and again while running the rake task