Append works like write with the exception that it does not overwrite the old file if it already exists, but rather adds the generated output to the end of the file.

filename 'name.txt' append
   /* generator output commands here */
close

To write several times to a file in a generator, when it is impractical to keep the file open, you can open it the first time with write (to overwrite any old version), and use append each time you open the file later in the generator.