How to search for non-ASCII characters in filenames?

Before you make any attempts to change anything be sure to have a good backup first since something will most likely go wrong.

I found a few posts which contain some useful information which use bash commands to find filenames with non-ASCII characters. These posts contain some very good and interesting information so read them thoroughly as they involve character encoding which can have unforeseen effects on some regex. From these posts I think the "find" option or the "detox" options are the best ones. Chances are the macOS commands will be too old so you may need to use Homebrew to install newer versions of the commands, but make sure you run the Homebrew versions and not the macOS version. Maybe something here will help you.

https://stackoverflow.com/questions/19146240/find-and-delete-files-with-non-ascii-names

https://serverfault.com/questions/348482/how-to-remove-invalid-characters-from-filenames

https://unix.stackexchange.com/questions/109747/identify-files-with-non-ascii-or-non-printable-characters-in-file-name

Here is a blog about file name character issues. The following two sections may be the most relevant for TLDR:

Character Encoding Issues:

https://dwheeler.com/essays/fixing-unix-linux-filenames.html#utf8

See section 9.2 dealing with "find":

https://dwheeler.com/essays/fixing-unix-linux-filenames.html#tricks

You are on your own implementing a solution since it would take me a while to digest this information since my regex skills are very poor. Detox may be the easiest and safest option.

Like what chrs?

After awhile of attempting it turns out to be beyond my capabilities.

Hold e down & you should see...

e...

ø is gotten by holding o key down

Find Any File...

http://apps.tempel.org/FindAnyFile/index.php

Hold Option or alt key when selecting Find to Find All.

then there a cool App called A better Finder Rename...

https://www.publicspace.net/ABetterFinderRename/index.html