Re: help with subroutines and reading/writing to file

blake askew wrote:
I am new to perl and attempting to write a script that will do a reverse dns
lookup on an ip, store this result into a file, then read the file in order
to do a whois lookup. The whois lookup answer should also be written to a
seperate file. I have the reverse dns lookup working, but when I also call
my whois subroutine, nothing is written to file for the the reverse dns (I
get a file size of 0). Can someone tell me where I am going wrong here?


#!/usr/bin/perl

use warnings;
use strict;

#
# repeat outbound connection check
# usage: ./ipcheck.pl <ip>
# ARGV[0] = ip address

# required for reverse DNS lookup, whois
# to install, as root run: perl -MCPAN -e 'install Net::<module_name>'
use strict;
use Net::DNS;
use Net::IP;
use Net::ParseWhois;

#check for user input and print usage instructions if nothing is supplied
if (@ARGV <= 0)

An array can never have a value less than 0.


{
die ("Usage: ./ipcheck.pl <ip> <options>:\n");
}

# get ip address from command line input
my $ip = $ARGV[0];

print ("Creating results file $ip-results.txt\n");
#call file creation subroutine
#&createfile;

print ("Attempting reverse DNS lookup\n");
# call reverse DNS lookup subroutine
&reversedns;

The proper form for calling a subroutine in perl is:

reversedns();


print ("Attempting whois lookup\n");
#call whois subroutine
&whois;

print ("Program executed successfully");
#
-----------------------------subroutines------------------------------------------

# create file subroutine
sub createfile {

# opens the <ip>-results.txt file to write the resuls to. Prints error
message if file cannot be opened
# prints results to the dir thescript is ran from
open (RESULTS, ">$ip-results.txt") || die ("Could not open results file");

You should include the $! variable in the error message so you know *why* it failed. You might also want to include the file name so you know which file could not be opened.


}

# reverse dns subroutine
sub reversedns {

#open file to write to <ip>-results-reverse-dns.txt
open (RESULTSDNS, ">$ip-results-reverse-dns.txt") || die ("Could not
open results file");

See advice above for previous open().


#gets the ip address from the command line
my $ip = $ARGV[0];

# Creates a resolver for resolving the reverse DNS lookup.
my $res = Net::DNS::Resolver->new;

# Creates an IP object.
my $target= new Net::IP($ip) or die("Unable to ip object for $ip\n");

# create the reverse lookup DNS name
# octets in the IP address need to be reversed).
my $target_IP = join('.', reverse split(/\./,
$target->ip())).".in-addr.arpa";

# Perform a query on the produced name. (note we want the PTR records
for the name).
my $q = $res->query("$target_IP", "PTR");

perldoc -q quoting


if($q)
{
# If the query on the produced name is valid then get the
answer.
my $r = ($q->answer)[0];

# If the query returns a result other than the PTR record,
print error and die.
if($r->type ne "PTR")
{
die ("Error: query returned result other than PTR
record");
}

# prints the answer to file (<ip>-results-reverse-dns.txt)
print RESULTSDNS ($r->rdatastr."\n");
# close file when done writing
#close (RESULTSDNS);
}
}

# whois subroutine
sub whois {

# open file to read in reverse dns answer
open (RESULTSRDNS, "$ip-results-reverse-dns.txt") || die ("Could not
open reverse dns results file to read in reverse dns answer");

See advice above for previous open().


# read in reverse dns answer to use as domain variable from
<ip>-results.txt
my @domain = <RESULTSRDNS>;

# closes the file when done reading
close (RESULTSRDNS);

while (my @domain == "")

You are creating a new empty @domain variable and then comparing it numerically to a string so inside this while loop @domain will always be empty and the loop will never end.


{

#open the file to write to
open (RESULTSWHOIS, ">$ip-results-whois.txt") || die ("Could not open
temp results file for writing whois information");

See advice above for previous open().


my $soa_domain;

FIND_SOA: {
my $res = new Net::DNS::Resolver;

my $q = $res->send(@domain, "SOA");

for my $sec (qw(answer authority))
{
my $meth = $q->can($sec) or next;

for my $rec ($meth->($q))
{
next unless $rec->isa('Net::DNS::RR::SOA');

$soa_domain = $rec->name;

last FIND_SOA if $soa_domain;
}
}
}

#die "Couldn't find SOA for $domain\n" unless defined $soa_domain;
$soa_domain ||= @domain;

If $soa_domain is 0 or empty you are assigning it the number of elements of @domain?


my $whois = new Net::ParseWhois::Domain($soa_domain);
warn "Couldn't connect to Whois server$/", next unless $whois;
warn "No Whois match for $soa_domain$/", next unless $whois->ok;

# print out whois match
print RESULTSWHOIS ("Whois Information:\n");
print RESULTSWHOIS "Whois Server: ", $whois->whois_server, $/;
print RESULTSWHOIS $/;

print RESULTSWHOIS "Registrar: ", $whois->registrar, $/;
print RESULTSWHOIS "Domain: ", $whois->domain, $/;
print RESULTSWHOIS "Name: ", $whois->name, $/;
print RESULTSWHOIS "Tag: ", $whois->tag, $/;
print RESULTSWHOIS $/;

print RESULTSWHOIS "Address:", $/;
print RESULTSWHOIS "\t", $_, $/ for $whois->address;
print RESULTSWHOIS $/;

print RESULTSWHOIS "Country: ", $whois->country, $/;
print RESULTSWHOIS $/;

print RESULTSWHOIS "Name Servers:", $/;
printf RESULTSWHOIS "\t%s (%s)$/", @$_ for @{$whois->servers};
print RESULTSWHOIS $/;

if (my $c = $whois->contacts)
{
print RESULTSWHOIS "Contacts:", $/;
for my $t (sort keys %$c)
{
print RESULTSWHOIS " " x 4, $t, ":", $/;
print RESULTSWHOIS "\t", $_, $/ for @{$c->{$t}};
}
print RESULTSWHOIS $/;
}

print RESULTSWHOIS "Record created: ", $whois->record_created, $/;
print RESULTSWHOIS "Record updated: ", $whois->record_updated, $/;
print RESULTSWHOIS "Record expires: ", $whois->record_expires, $/;

print RESULTSWHOIS "=" x 76, $/ if @ARGV;

Why are you using $/ instead of "\n"?


# close the file when done writing
close (RESULTSWHOIS);
}
}


John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
.

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