error in trimdomain(3)

[Ceri Davies]

On Mon, Oct 03, 2005 at 11:24:06AM -0700, Brooks Davis wrote:
> On Mon, Oct 03, 2005 at 07:18:08PM +0100, Ceri Davies wrote:
> > On Mon, Oct 03, 2005 at 11:03:44AM -0700, Brooks Davis wrote:
> > > On Mon, Oct 03, 2005 at 11:31:24AM +0100, Ceri Davies wrote:
> > > > On Sat, Oct 01, 2005 at 02:35:50AM -0700, Brooks Davis wrote:
> > > > > I discovered today that the trimdomain() implementation in libutil deviates
> > > > > slightly from the manpage.  The manpage says:
> > > > > 
> > > > >      The function trimdomain() removes the current domain name from the passed
> > > > >      fullhost name by writing a NUL character over the first period of the
> > > > >                                                        ^^^^^^^^^^^^
> > > > >      passed name.  The current domain name is determined by calling
> > > > >      gethostname(3) and removing everything up to the first period.
> > > > > 
> > > > > which clearly indicates that trimdomain() should return either the
> > > > > unmodified string or a host name with no domain.  In reality it will
> > > > > remove the domain name even if the result is not a host name.  This
> > > > > means that if the host b.com calls trimdomain with "a.b.com" as the
> > > > > input string, the result is "a.b".
> > > > 
> > > > That's actually what the excerpt above says will happen.
> > > > 
> > > > gethostname returns "b.com", removing everything up to the first period
> > > > yields ".com", and that removed from "a.b.com" gives you "a.b".
> > > > 
> > > > I don't care if it needs to be changed, but that does exactly what it
> > > > says on the tin so far as I can see.
> > > 
> > > There are two refrences to "first period".  You are correct that the
> > > domain name of b.com is .com, but the refrence I highlighted states that
> > > the only allowable modification to the host name is writing a NUL to
> > > the first period in the string (it's actually messier than this because
> > > trimdomain also supports X11 DISPLAY strings and thus does a memmove and
> > > reterminates if there is a :0 or :0.0 type string after domain.)
> > 
> > I agree that the documentation gives that impressions but the fact that
> > it bothers to call gethostname at all makes me wonder; if it's just going
> > to replace the first period with a NUL then I don't see why that call is
> > necessary, unless the intention is to achieve the current behaviour.
> 
> My interpretation is that the function is intended to remove the domain
> only if it is the local domain and thus implicit.

Ah, now I see it; yes, I'm with you.

Ceri
-- 
Only two things are infinite, the universe and human stupidity, and I'm
not sure about the former.			  -- Einstein (attrib.)
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