Re: ip address get problem

Getting an IP address is even a Perl FAQ¹ :)

How do I find out my hostname/domainname/IP address?
The normal way to find your own hostname is to call the `hostname` program. While sometimes expedient, this has some problems, such as not knowing whether you've got the canonical name or not. It's one of those tradeoffs of convenience versus portability.

The Sys::Hostname module (part of the standard perl dis- tribution) will give you the hostname after which you can find out the IP address (assuming you have working DNS) with a gethostbyname() call.
           use Socket;
           use Sys::Hostname;
           my $host = hostname();
           my $addr = inet_ntoa(scalar gethostbyname($host || 'localho
+st'));
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Probably the simplest way to learn your DNS domain name is to grok it out of /etc/resolv.conf, at least under Unix. Of course, this assumes several things about your resolv.conf configuration, including that it exists.

(We still need a good DNS domain name-learning method for non-Unix systems.)

¹ perldoc -q "IP address"

--
b10m

All code is usually tested, but rarely trusted.

Comment on Re: ip address get problem Download Code

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Re: Re: ip address get problem by markd (Acolyte) on Mar 22, 2004 at 15:20 UTC
Thanks for that but that code does not seem to work for me. The active ip address on my host machine is on the hme0 interface. The code you supplied got me the ip address on another interface. This is why I was trying to go through the hosts file to get my ip address. This has the primary ip address on the host. The trouble is that my code to extract from this file is not working. Would you know what is wrong with this code? I can't figure what is happening: $hostname = `hostname`; print "hostname is $hostname\n"; [download] This works to get the hostname. It is the following bit of code that does not work to translate that hostname into an ip address: $source = `ypcat hosts \| grep '$hostname$'`; $source =~ /\d+.\d+.\d+.\d/; print "source is $addr\n"; [download]	[reply] [d/l] [select]
Re: ip address get problem by Abigail-II (Bishop) on Mar 22, 2004 at 16:17 UTC
The active ip address on my host machine is on the hme0 interface. The code you supplied got me the ip address on another interface. This is exactly why questions like "finding the IP address of my machine" are meaningless. It also means any solution to "finding a IP address of my machine" that use `hostname` are not very useful. Machines don't have IP addresses. Interfaces have IP addresses. An interface can have 0, 1 or more than one IP address, and an IP address can be shared by more than one interface, which may be on the same machine, or on different machines. Machines can have 0, 1 or more interfaces. Machines have hostnames, typically one. There is NO relationship between a machines hostname, and the IP addresses of their interfaces, unless the local administrator happens to set up things that way. My laptop has a hostname, and it always has the same hostname. But the IP address of its non-loopback interface depends on which network I plug the machine in. Abigail	[reply]