Save to disk simulation and template weird error?

[khonshu]

Would it be possible to have a function that filters the result of a template (a string) returning the string as it will be saved to disk? I mean, taking away all characters that aren't allowed for the file path/name...
I have been "programming" a mix of custom columns and templates to get exactly the output I want... just to find calibre makes changes to the path/filename... My lybrary is about 16000 epub files and testing this is taking me more hours than expected... Maybe it exists already but couldn't find anything aboout it in the manuals nor googling...

Another question: Has anyone faced this: I make a template. The result is correctly displayed in the template value box but when I click on Accept the result on the columns is an error... that happened after changing a template to general program mode if that helps... I wen't back to the template and it works perfectly... my question is just curiosity as I read general program mode templates are compiled speeding up processing...

Thank you for all your work, developers and community.