pure number allowed as username in the useradd command?

[Aaron Konstam]

On Thu, 2010-12-02 at 18:10 +0100, Joachim Backes wrote:
> Can somebody explain why pure numbers are allowed for username in the
> useradd command?
> 
> sudo useradd 123456789
> 
> is not rejected!
> 
> As is known, this leads to big problems if referring to such a user and
> the username differs from the userid: should such a username be
> interpreted as username or userid?
> 
> Thanks for each comment.
> 
> Kind regards
> 
As you said using a pure number for userid can be diasterous But you
question needs to be answered by the creator of useradd.

I once created a useradd program with added functionality and I know
from first hand experience that are many pitfalls to get it to work
properly. Consider what happens if you have a userid that is the same
number as a userid.

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Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam at sbcglobal.net