Use with-temp-file To Write To A File In Emacs
Quick example of how to write out to a file by making a temporary buffer. You write whatever contents you want to the tmp buffer which then outputs to the file and drops the temporary buffer when it's done.
Code
(with-temp-file "test-file.txt"
(insert "here is some stuff")
(insert "\n")
(insert "and some more stuff")
)