[Pkg-shadow-devel] Why uppercase is not allowed in username by "useradd"?

Wangrui Shen wangrui.shen at windriver.com
Fri Oct 10 06:16:54 UTC 2014

Hi experts,
In libmisc/chkname.c, is_valid_name() only return ture if
the pattern [a-z_][a-z0-9_-]*[$] is matched. For example:
~# useradd nodeA123;
useradd: invalid user name 'nodeA123'

But in other repository, the pattern is replaced with [a-zA-Z0-9_.][a-zA-Z0-9_.-]{0,30}[a-zA-Z0-9_.$-],
which means uppercase characters and additional character are also allowed, such as:
shadow-4.0.3-goodname.patch in

my questions is:
Are there some special concerns that don't allow uppercase to be used in username?


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