Re: Subprocess puzzle and two questions

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From	Nobody <nobody@nowhere.com>
Subject	Re: Subprocess puzzle and two questions
Date	Thu, 15 Nov 2012 22:54:10 +0000
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On Wed, 14 Nov 2012 20:49:19 -0500, Roy Smith wrote:

>> I'm slightly surprised that there's no way with the Python stdlib to 
>> point a DNS query at a specific server
> 
> Me too, including the "only slightly" part.  The normal high-level C 
> resolver routines (getaddrinfo/getnameinfo, or even the old 
> gethostbyname series), don't expose any way to do that.

That's because the high-level routines aren't tied to DNS.

gethostbyname() and getaddrinfo() use the NSS (name-service switch)
mechanism, which is configured via /etc/nsswitch.conf. Depending upon
configuration, hostnames can be looked up via a plain text file
(/etc/hosts), Berkeley DB files, DNS, NIS, NIS+, LDAP, WINS, etc. DNS is
just one particular back-end, which may or may not be used on any given
system.

If you specifically want to perform DNS queries, you have to use a
DNS-specific interface (e.g. the res_* functions described in the
resolver(3) manpage), or raw sockets, rather than a high-level interface
such as gethostbyname() or getaddrinfo().

Thread

Subprocess puzzle and two questions wrw@mac.com - 2012-11-13 22:34 -0500
  Re: Subprocess puzzle and two questions Roy Smith <roy@panix.com> - 2012-11-13 23:41 -0500
    Re: Subprocess puzzle and two questions William Ray Wing <wrw@mac.com> - 2012-11-14 00:03 -0500
      Re: Subprocess puzzle and two questions Roy Smith <roy@panix.com> - 2012-11-14 09:22 -0500
        Re: Subprocess puzzle and two questions Chris Angelico <rosuav@gmail.com> - 2012-11-15 01:40 +1100
          Re: Subprocess puzzle and two questions roy@panix.com (Roy Smith) - 2012-11-14 11:20 -0500
            Re: Subprocess puzzle and two questions Chris Angelico <rosuav@gmail.com> - 2012-11-15 08:54 +1100
              Re: Subprocess puzzle and two questions Roy Smith <roy@panix.com> - 2012-11-14 20:49 -0500
                Re: Subprocess puzzle and two questions Chris Angelico <rosuav@gmail.com> - 2012-11-15 13:04 +1100
                Re: Subprocess puzzle and two questions Roy Smith <roy@panix.com> - 2012-11-14 21:10 -0500
                Re: Subprocess puzzle and two questions Chris Angelico <rosuav@gmail.com> - 2012-11-15 13:21 +1100
                Re: Subprocess puzzle and two questions Dave Angel <d@davea.name> - 2012-11-14 21:55 -0500
                Re: Subprocess puzzle and two questions Kushal Kumaran <kushal.kumaran+python@gmail.com> - 2012-11-15 10:23 +0530
                Re: Subprocess puzzle and two questions Nobody <nobody@nowhere.com> - 2012-11-15 22:54 +0000
                Re: Subprocess puzzle and two questions Roy Smith <roy@panix.com> - 2012-11-15 20:07 -0500
                Re: Subprocess puzzle and two questions Nobody <nobody@nowhere.com> - 2012-11-17 00:17 +0000
              DNS from Python (was Re: Subprocess puzzle and two questions) aahz@pythoncraft.com (Aahz) - 2012-11-14 21:42 -0800
        Re: Subprocess puzzle and two questions wrw@mac.com - 2012-11-14 09:37 -0500
  Re: Subprocess puzzle and two questions Tim Roberts <timr@probo.com> - 2012-11-13 23:17 -0800

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