How to create a file "on the fly" ?

I have a page that users fill info and a  button to submit that info. 
When the button is pressed I want to create a file with some text content.
1.How can I create a file to send it by mail ?
2.When I have send the file by mail I want the file to be deleted. How I 
delete a file?

The file I want to create must be text file with unicode support.