I'm looking for a regex (at least I think what is most likely a regex)
It could possibly be one regex, but it would more likely be several regexes.
Besides, you did not clearly specify whether you just want to validate that the text used satisfies your requirements, or whether you actually want to clean up the piece of text (i.e. remove characters that violate your requirements).
Are you posting in the right place? Check out Where do I post X? to know for sure.
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Want more info? How to link or
or How to display code and escape characters
are good places to start.