Deleting ghost files with non-ASCII characters

macos has a special /.vol/ system mapped to the actual directory and files. The files and directories are accessible via /.vol/<device_id>/<inode_number>, regardless of where the files are on the file system.

It is a nice little system.

So, programs can for example get the inode number of /Users/jdoe/someFile.txt and then open it via /.vol/12345/6789 (in this case, device id is 12345 and inode number 6789). You then move /Users/jdoe/someFile.txt anywhere you want (on the same volume) and everything just works. You can even write a shell script that supports this magic.

ls -di <file> to get inode number.

$ ls -di /User/jdoe/someFile.txt
6789 /User/jdoe/someFile.txt

EDIT:

You use stat to get the id of the volume and inode number, according to linked answer as highlighted by IMSoP.

GetFileInfo /.vol/12345/6789 would return the current location of the file previously located in /Users/jdoe/someFile.txt.

See https://stackoverflow.com/questions/11951328/is-there-any-function-to-retrieve-the-path-associated-with-an-inode for more information.

Automatic Trash Removal

To set the thirty-day automatic Trash removal option for $username:

sudo -u $username bash -c 'defaults write com.apple.finder FXRemoveOldTrashItems -bool true'

Presenting a Dialog

Please note that to get the dialog portion working on a SIP-enabled Mojave, each user requires an entry in System Preferences > Security & Privacy > Privacy > Automation to give a terminal access to System Events.app, which displays the dialog. Here's one using osascript that looks as follows.

If a user clicks "Yes," then the exit code from the dialog is 0 (zero). One might incorporate knowledge of the dialog's successful exit code with a script, as shown below.

#!/usr/bin/env bash
osascript -e 'tell app "System Events" to display dialog "Hi. I am automated script. May I delete Desktop & Trash files older than 30 days?" buttons {"Yes", "No"} with icon caution' >/dev/null 2>&1 

# $? is the exit code of the very last command that was executed (osascript).
#
if [ $? -eq 0 ]; then
    # Do something.
    echo "You clicked Yes."
fi

Finding Files

Below, finding files of specific types (file and directory) whose names are not .DS_Store or .localized and that are 30+ days old. The first line is for a safe test. Swap with the line below it to delete found objects. If an option needs to be specified more than once, use -o. Be sure to escape (\) special characters. The whitespace at the beginning and end of the parentheses is also important.

#!/usr/bin/env bash
find "$HOME/Desktop" -type f -o -type d -mtime +30 \! \( -name '.DS_Store' -o -name '.localized' \) -print
# find "$HOME/Desktop" -type f -o -type d -mtime +30 \! \( -name '.DS_Store' -o -name '.localized' \) -exec rm -rf '{}' +

Listing Users

#!/usr/bin/env bash
# Getting a list of users, filtering out service accounts, root, daemon, and nobody...
users=$(dscl . list /Users | grep -v -e '_' -e 'root' -e 'daemon' -e 'nobody')

for user in "$users"; do
    # Do something.
    id "$user"
done

unset users

Obviously there is some interpolation to do in order to stitch these snippets into a working script, but I hope it provides at least a bit more insight. Were it me, I think I might try to keep the script in /usr/local/bin and then set up a cron job to execute the script monthly.