General :: How To Recode To UTF-8 Conditionally

I'm unifying the encoding of a large bunch of text files, gathered over time on different computers. I'm mainly going from ISO-8859-1 to UTF-8. This nicely converts one file:recode ISO-8859-1..UTF-8 file.txtI of course want to do automated batch processing for all the files, and simply running the above for each file has the problem that files whose already encoded in UTF-8, will have their encoding broken. (For instance, the character originally in ISO-8859-1 will appear like this, viewed as UTF-8, if the above recode is done twice:My question is, what kind of script would run recode only if needed, i.e.

only for files that weren't already in the target encoding (UTF-8 in my case)?From looking at recode man page, I couldn't figure out how to do something like this. So I guess this boils down to how to easily check the encoding of a file, or at least if it's UTF-8 or not.This answer implies you could recognise valid UTF-8 files with recode, but how?