[CentOS] E-mail advice sought

Sun May 1 17:24:30 UTC 2016
Gordon Messmer <gordon.messmer at gmail.com>

On 05/01/2016 05:23 AM, Alice Wonder wrote:
> It's the set I'm after. Or its complement. I don't care. Not whether 
> my code should use set A or its complement. 

Then you're after RFC 5321 section 4.1.2 and possibly 6531 section 3.3 
(but probably not for a few years yet).  You should also consider 
shadow-utils' chkname.c, where valid local user names are restricted to 
"[a-z_][a-z0-9_-]*[$]" of less than USER_NAME_MAX_LENGTH characters 
(though not with a regex).