Some recovered file names start with $$_

Recuva Recuva Suggestions
1

I have recovered some files whose file names started with "$$_"filename. What are these files? What is the $$_ there for?

Thanks

2

I've no idea. Do you mean start with "$$_"filename, or $$_filename? Does the folder name give you a clue?

3

From my very old experience of Unix (not used it for years).

In a Unix Bash shell $$ returns the Process ID of a running script .

I'm assuming that Recuva is using Unix or Linux to scan the disc, (many/most recovery tools do), and is using the process ID's to generate temporary filenames for whatever it has recovered.

EDIT. 

Here's a bit more about these Unix special parameters that start with $ for anyone interested:

https://unix.stackexchange.com/questions/218270/which-are-bash-shell-special-parameters