Re: error in trimdomain(3)

From: Ceri Davies (ceri_at_submonkey.net)
Date: 10/03/05

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    Date: Mon, 3 Oct 2005 19:44:07 +0100
To: Brooks Davis <brooks@one-eyed-alien.net>

    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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