testing for ip resolutions of a hostname

c has asked for the wisdom of the Perl Monks concerning the following question:

I read over How to find IP address from hostname? and found it helpful and brought me somewhat up to speed on using 'gethostbyname'. I am trying to evaluate whether a hostname (fqdn or otherwise) is able to resolve to an ip address (through dns or an /etc/hosts file).
I am able to use gethostbyname for hosts that resolve properly, however when a bogus name is presented as the hostname argument, the script errors out. i would rather it come back false such that i can say:

print "It doesnt resolve\n" unless ($ip);

I am toying around with the following code:

#!/usr/bin/perl -w

use strict;
use Socket;


my $host = "noresolve";

my $i = gethostbyname($host);
my $ip = inet_ntoa($i);

print "Failure!\n" unless ( $ip );
[download]

humbly -c

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Re: testing for ip resolutions of a hostname by idnopheq (Chaplain) on Aug 28, 2001 at 21:42 UTC
UPDATE: Oops ... slip 'o the mouse. Do some error checking in your lookups. Makes life much simpler, IMHO. `#!/usr/bin/perl -w use strict; use Socket; my $host = "noresolve"; my $i = gethostbyname($host) or die "Failure to resolve $host: $!\n"; my $ip = inet_ntoa($i) or die "Failure to resolve $host: $!\n";` [download] HTH -- idnopheq Apply yourself to new problems without preparation, develop confidence in your ability to to meet situations as they arrise. ~ Shunryu Suzuki	[reply] [d/l]
Re: Re: testing for ip resolutions of a hostname by c (Hermit) on Aug 28, 2001 at 22:01 UTC
I can't use the die statements since those will force the script to exit. I want it to continue on and perform other actions based on whether or not the hostname is able to resolve to an ip address. humbly -c	[reply]
Re: Re: Re: testing for ip resolutions of a hostname by idnopheq (Chaplain) on Aug 28, 2001 at 22:10 UTC
Ah! The lightbulb dimly illuminates! Howzabout wrapping the lookup functions in a sub and replacing the 'die's with returns. Untested, BTW ... hopefully no typos ... `my $ip = lookup ( $host ) or warn "Cannot resolve $host!\n"; sub lookup { my $host = shift; my $i = gethostbyname($host) or return undef; my $ip = inet_ntoa($i) or return undef; return $ip; }` [download] HTH -- idnopheq Apply yourself to new problems without preparation, develop confidence in your ability to to meet situations as they arrise. ~ Shunryu Suzuki	[reply] [d/l]