Files will get written to the current working directory.
After SketchUp gets done loading it will set it to the User’s “Documents” directory.
(But again, extensions can change it, so either use absolute paths, or use the block form of the Dir.chdir method, which restores the previous directory when the block exits.)
You can see what it is by typing at the console …
Dir.pwd
P.S. - AGAIN please read: [How to] Post correctly formatted and colorized code on the forum?