If this the actual code you tried to run? This doesn't even compile, much less "work". Here's what you need to fix. You have: 
#!/usr/bin/perl

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As chromatic said, change this to 
#!/usr/bin/perl -w
use strict;

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"-w" enables warnings, and "use strict" forces you to declare your variables, prevents you from using barewords that aren't subroutines, and prevents you from using symbolic references. Good for any level of programmer.

So, with strict enabled, you should declare your $INPUT_FILE variable as a lexical variable, using my: 

my $INPUT_FILE = "ipnum";

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What's next, then? You've got this: 
open(INPUT_FILE);
@array = ;
close(INPUT_FILE);

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There are several things wrong here. First, that's now how open works. It takes *two* arguments: a filehandle and the filename (read perldoc -f open for more details). Also, as chromatic suggested, check the status of your open and close calls! Always check the return value of a system call!

Second, that next line doesn't even compile. You want to read from the filehandle--Perl makes that quite simple.

So we'll replace what you have with this: 

open INPUT_FILE, $INPUT_FILE
    or die "Can't open $INPUT_FILE: $!";
my @array = <INPUT_FILE>;
close INPUT_FILE
    or die "Can't close $INPUT_FILE: $!";

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Finally, you've got the loop that calls nslookup for each IP address in the file. One real problem here--as previously mentioned, you used single-quotes instead of backticks. You need backticks (`) in order to actually make the system call. Otherwise it's just a single-quoted string, which is nothing special.

Second, you're looping over "@arrays"--but you never defined "@arrays". You defined "@array". Perhaps this was a typo?

So, with that in mind (and with the name of your loop variable changed to reflect more accurately the value it contains): 

for my $address (@array) {
    my $output = `nslookup $address`;
    print $output;
}

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So that's it. I realize that the end result of the code doesn't differ much from what other posters have written, but I hope that the explanation I've provided might help in the future, or the present.

In reply to Re: HELP - nslookup in perl by btrott
in thread HELP - nslookup in perl by Anonymous Monk

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