How can I get rid of unicode characters in a csv file?

To add to Adrian Ho’s answer: Non-Ascii characters can cause havoc in (very very old by now) applications that assume a particular one-byte encoding like Latin-1. For that reason, command-line solutions like what Adrian suggests are safer for ASCII-fying text files than Windows or Mac applications, which may still leave stray Non-ASCII characters in place.

An abundance of command-line solutions can be found on the Better Place (StackOverflow):

• Remove non-ascii characters from csv
• Trying to delete non ascii characters only

If you’re in a non-stupid text-editor on Windows or Mac, Regexes will save you; e.g.

• Notepad++, How to remove all non ascii characters with regex?

(Notepad++ on Windows is non-stupid; so is BBEdit on Mac.)