variable not passing

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

Trying to get this to accept an ip address as an argument and it doesnt work. If I eliminate the $addy variable and just put in an ip address here: my $client = gethostbyaddr(111.11.111.111, AF_INET); # get name it works but cant get it to accept a variable in the below:

use Socket; 
use strict;
my $addy = shift || die "Enter a IP address";
my $client = gethostbyaddr($addy, AF_INET); # get name
if ($client)
{
print $client, "\n\a";
}
else
{
print "no\n";
}
[download]

The output keeps coming back with "no" even though I put in a valid ip address. It should give me back the name to the server. Why cant I pass the $addy variable in the argument. Please help me fix this.

Comment on variable not passing Download Code

Replies are listed 'Best First'.
Re: variable not passing by gaal (Parson) on Dec 07, 2004 at 18:31 UTC
You need to call `inet_aton` on your string first. See Socket.	[reply] [d/l]
Re^2: variable not passing by Anonymous Monk on Dec 07, 2004 at 18:51 UTC
Thanks I tried this and still no luck: `use Socket; use strict; my $addy = shift \|\| die "Enter a IP address"; my $port = getservbyname('smtp', 'tcp'); my $sin = sockaddr_in($port,inet_aton($addy)); my $client = gethostbyaddr($sin, AF_INET); # get name if ($client) { print $client, "\n\a"; } else { print "no\n"; }` [download]	[reply] [d/l]
Re^3: variable not passing by gaal (Parson) on Dec 07, 2004 at 19:05 UTC
You don't need this sin stuff here. Try your original code, but with the following replacement: `# this: my $client = gethostbyaddr(inet_aton($addy), AF_INET); # get name # instead of: my $client = gethostbyaddr($addy, AF_INET); # get name` [download] It worked for you with the variable not received from the user because you weren't using quote marks, and you were getting a v-string (a deprecated feature, actually). Your luck was that a v-string is a lot like an `inet_aton()`-ed string :) Incidentally, why are you using `Socket`? Unless you want to use low-level stuff for learning or fine control, you are probably better off using IO::Socket. See perlipc, also.	[reply] [d/l] [select]
Re^4: variable not passing by Anonymous Monk on Dec 08, 2004 at 10:56 UTC
Re: variable not passing by Eimi Metamorphoumai (Deacon) on Dec 07, 2004 at 19:01 UTC
Use `my $client = gethostbyaddr(inet_aton($addy), AF_INET); # get name` [download] instead. You'll findthat if you used `"111.11.111.111"` instead of `111.11.111.111` (note the quotes), you would have gotten the same result. But it turns out that perl handles dotted quads (or actually any dotted decimals) as a particular kind of string constant (called a Version String, search for it in perldata for more info) that doesn't need processing through `inet_aton`.	[reply] [d/l] [select]