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Validating string for FDQN

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  Validating string for FDQN Eric <eric.wong.t@gmail.com> - 2011-06-06 17:40 -0700
    Re: Validating string for FDQN harrismh777 <harrismh777@charter.net> - 2011-06-06 20:55 -0500
    Re: Validating string for FDQN Chris Angelico <rosuav@gmail.com> - 2011-06-07 12:50 +1000
    Re: Validating string for FDQN Philip Semanchuk <philip@semanchuk.com> - 2011-06-06 23:10 -0400
    Re: Validating string for FDQN Nobody <nobody@nowhere.com> - 2011-06-07 06:23 +0100
      Re: Validating string for FDQN Chris Angelico <rosuav@gmail.com> - 2011-06-07 15:52 +1000
        Re: Validating string for FDQN Chris Torek <nospam@torek.net> - 2011-06-07 06:20 +0000
        Re: Validating string for FDQN Nobody <nobody@nowhere.com> - 2011-06-07 21:46 +0100

#7123 — Validating string for FDQN

Hello,

Is there a library or regex that can determine if a string is a fqdn
(fully qualified domain name)? I'm writing a script that needs to add
a defined domain to the end of a hostname if it isn't already a fqdn
and doesn't contain the defined domain.

Thanks.

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#7125

Eric wrote:
> Is there a library or regex that can determine if a string is a fqdn
> (fully qualified domain name)? I'm writing a script that needs to add
> a defined domain to the end of a hostname if it isn't already a fqdn
> and doesn't contain the defined domain.

You might try the os module and then use something like nslookup.


import os
os.system('nslookup <name>')


The output is sent on the subprocess standard out... so you can grab it 
with piping, or redirect, or redirect to a file and read later, etc.

You might also try the subprocess module. It provides better flexibility 
and control for handling the output of the nslookup, or whatever tool 
you decide to use to find the fully qualified name.

kind regards,
m harris

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#7129

On Tue, Jun 7, 2011 at 10:40 AM, Eric <eric.wong.t@gmail.com> wrote:
> Hello,
>
> Is there a library or regex that can determine if a string is a fqdn
> (fully qualified domain name)? I'm writing a script that needs to add
> a defined domain to the end of a hostname if it isn't already a fqdn
> and doesn't contain the defined domain.

One reliable way to test would be to do a whois check on the name. If
it comes up with something, it's fully qualified.

http://code.google.com/p/pywhois/

Alternatively, if all you want is a simple syntactic check, and if you
can assume that the name is already a valid domain name (no weird
characters, etc), then you can simply divide it on the last dot and
see if the last part is a recognized TLD. A partial list of TLDs can
be found here:

http://data.iana.org/TLD/tlds-alpha-by-domain.txt

There are other TLDs too, including .localhost and .test, which you
can probably ignore.

Chris Angelico

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#7134

On Jun 6, 2011, at 8:40 PM, Eric wrote:

> Hello,
> 
> Is there a library or regex that can determine if a string is a fqdn
> (fully qualified domain name)? I'm writing a script that needs to add
> a defined domain to the end of a hostname if it isn't already a fqdn
> and doesn't contain the defined domain.

The ones here served me very well:
http://pyxml.cvs.sourceforge.net/viewvc/pyxml/xml/xml/Uri.py?revision=1.1&view=markup

bye
Philip

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#7137

On Mon, 06 Jun 2011 17:40:29 -0700, Eric wrote:

> Is there a library or regex that can determine if a string is a fqdn
> (fully qualified domain name)? I'm writing a script that needs to add
> a defined domain to the end of a hostname if it isn't already a fqdn
> and doesn't contain the defined domain.

Try socket.getfqdn() or socket.gethostbyname_ex().

With one exception[1], you can't reliably do it just by examining the
string; you have to ask the resolver.

[1] If a hostname ends with a dot, it's fully qualified.

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#7138

On Tue, Jun 7, 2011 at 3:23 PM, Nobody <nobody@nowhere.com> wrote:
> [1] If a hostname ends with a dot, it's fully qualified.
>

Outside of BIND files, when do you ever see a name that actually ends
with a dot?

ChrisA

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#7140

>On Tue, Jun 7, 2011 at 3:23 PM, Nobody <nobody@nowhere.com> wrote:
>> [1] If a hostname ends with a dot, it's fully qualified.
[otherwise not, so you have to use the resolver]

In article <mailman.2521.1307425928.9059.python-list@python.org>,
Chris Angelico  <rosuav@gmail.com> wrote:
>Outside of BIND files, when do you ever see a name that actually ends
>with a dot?

I type them in this way sometimes, when poking at network issues. :-)
-- 
In-Real-Life: Chris Torek, Wind River Systems
Salt Lake City, UT, USA (40°39.22'N, 111°50.29'W)  +1 801 277 2603
email: gmail (figure it out)      http://web.torek.net/torek/index.html

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#7185

On Tue, 07 Jun 2011 15:52:05 +1000, Chris Angelico wrote:

>> [1] If a hostname ends with a dot, it's fully qualified.
> 
> Outside of BIND files, when do you ever see a name that actually ends
> with a dot?

Whenever it is entered that way.

This may be necessary on complex networks with local subdomains, i.e.
where resolv.conf has "options ndots:2". E.g. "foo.it" might resolve to
"foo.it.bar.edu" (in bar.edu's IT department's subdomain), requiring a
trailing dot if you want the Italian site "foo.it".

The canonical real-world example of this used to be foo.cs resolving to
foo.cs.berkeley.edu (UCB Comp. Sci. department), but ever since .cs split
into .cz and .sk it's no longer ambiguous.

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