Terminal - how to change first and last name on local account

Is John smith the current real name or is U12345? The old value should come first before the new.

sudo dscl . -change /Users/U12345 RealName U12345 "Smith, John"

@james179

Current real name is "Mary Kay", account ID U12345. I want to keep the same ID but change the "real" name to "John Smith"
Now it gives me an error:

<main> attribute status: eDSAttributeNotFound
<dscl_cmd> DS Error: -14134 (eDSAttributeNotFound)

Check out this post, should help you.

https://jamfnation.jamfsoftware.com/discussion.html?id=6658

Thanks for your help!
That one finally works for me in terminal:

sudo /usr/bin/dscl . -change /Users/I12345 RealName "Mary Kay" "John Smith"

Now -read gets back with the new full name:

sudo dscl . -read /Users/U12345 RealName
RealName: John Smith

@james179, @pblake - thanks again!