invalid characters in string - regular expression

Question

I am storing filename in my database and when a international language is used, it stores something like below as my filename.

 平素ãã誠ã«ãä¸è©±ã«ãªã£ã¦ããã¾ã.docx

please could someone give me a regular expression which will identify such invalid characters?

The below characters are acceptable :

a-z, 0-9 , () <> [] {}  %^&*$#@~"';?:! etc. 

are all acceptable. Just not the ones above which cannot be seen on the keyboard.

Thanks .

Answer 1

A reasonably good approximation is

[^[:ascii:][:print:]]

which matches characters that are either non-ASCII or non-printable. The question stands open, of course, whether to be a printable ASCII code is enough for being acceptable as part of a file name...