Thanks. It does say "a new temporary file **is** created" - emphasis on "is" rather than "may be" - unless of course I disagree with the documentation on the meaning of the word "is" (throwback to the 90s). The reason I'm asking is I do want to see it in action in testing, before I use it for real. For example, suppose this actually doesn't work with the library I'm using for whatever reason, and an empty string actually writes fully to memory rather than to disk - if I tried using this on something that's too big, it would crash (I assume) rather than spill over to disk. If I can watch it as it's happening, then I can be confident it'll work with larger sets of data. I suppose I can just do some bigger testing with a few GB of dummy data, and keep an eye on the /tmp directory and the system monitor for RAM usage. I figured I'd confirm that /tmp is right first.