From: "Fernando Hevia" <fhevia@ip-tel.com.ar>
To: "'Oliveiros C,'" <oliveiros.cristina@marktest.pt>,
	<pgsql-sql@postgresql.org>
References: <E94D918326D044C69895D829038E31B2@marktestcr.marktest.pt>
Subject: Re: Is there any function to test for numeric ips?
Date: Fri, 11 Dec 2009 13:20:03 -0300
Organization: IP-TEL
Message-ID: <D417D556031146289BCD9BA0F96F20DB@iptel.com.ar>
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> -----Mensaje original-----
> De: de Oliveiros C,
> 
> Dear All,
>  
> I have a table with host names and some happen to be numeric IPs.
>  
> I would like to be able to filter out the later.
>  
> Is there any function pre-defined in the system that can test 
> a particular text type value to see if it is a numeric ip?
>  
> Something that returns true if applied to '192.168.1.1' but 
> false if applied to 'videos.sapo.pt' ?
>  
> I considered NOT LIKE '%.%.%.%' but I'm affraid it will 
> filter out host names like 'www.google.com.br'
>  
> I've realized that, for ex, inet 'x.x.x.x' will fail if the 
> input is not a numeric IP, is there any simple and direct way 
> to somewhat trap that error and convert it to a false value 
> that can be used in a WHERE clause?
>  

You could filter IP out with a regular expression:

select hostname as hosts_not_ip
from table
where hostname !~ '^[0-9]\.[0-9]\.[0-9]\.[0-9]$'

Cheers,
Fernando.