Perl sort multiple column array - perl

Question

The hostlist.txt file has only 1 col. The prog reads hostlist.txt file, remove duplicate hostnames, sort the list, lookup ip address of each host in the list, and print the output on terminal.
hostlist.txt
host01
host03
host02
host01
output on terminal
host01,192.168.1.15
host02,192.168.1.12
host03,192.168.1.33
Program:
open(HOSTFILE, "hostlist.txt") or die "Couldn't open location file: $!\n";
while ($hosts = <HOSTFILE>) {
chomp($hosts);
push(#hostnames, $hosts);
}
close HOSTFILE;
#hostnameUnique = uniq(#hostnames);
#hostnameUniqueSorted = sort { lc($a) cmp lc($b) } #hostnameUnique;
foreach $hostname (#hostnameUniqueSorted){
$ipaddr = inet_ntoa((gethostbyname($hostname))[4]);
print "$hostname,$ipaddr\n";
}
I want to do the same thing as above, except the input file newhostlist.txt has 3 cols. Remove the duplicate hostname, sort first col($type), then sort 3rd col($location), then sort 2nd col($hostname), lookup ip address, and print output.
How do I process the multiple column array?
newhostlist.txt
dell,host01,dc2
dell,host03,dc1
hp,host02,dc1
dell,host01,dc2
Output:
dell,host03,192.168.1.33,dc1
hp,host02,192.168.1.12,dc1
dell,host01,192.168.1.15,dc2

Answer 1

#!/usr/bin/perl
use strict;
use warnings;
open(my $fh, '<', "newhostlist.txt") or die "Unable to open file: $!\n";
my %unique = map {$_ => 1} <$fh>;
my #data =
map {join",", ($_->[0], $_->[1], (#{$_->[3]}=gethostbyname($_->[1]))?inet_ntoa($_->[3][4]):'-' , $_->[2])}
sort {$a->[0] cmp $b->[0] ||
$a->[2] cmp $b->[2] ||
$a->[1] cmp $b->[1]}
map {s/^\s+|\s+$//g; [split/,/]} keys %unique;

Answer 2

ETA: Added the check for failed ipaddr lookup.
The easiest way to handle this would be to use the diamond operator, I feel:
use strict;
use warnings;
use ARGV::readonly;
my %seen;
while (<>) {
chomp; # to avoid missing newline at eof errors
next if $seen{$_};
$seen{$_}++;
my #row = split /,/, $_;
my #host = gethostbyname($hostname);
my $ipaddr;
if (#host == 0) {
$ipaddr = "host not found - ip not avail";
} else {
$ipaddr = inet_ntoa($host[4]);
}
splice #row, 2, 0, $ipaddr;
print join ",", #row;
}
Using ARGV::readonly allows for somewhat safer usage of the implicit file opens used with the diamond operator.
After that, simply weed out lines already seen by using a hash, split the row, put in the value you need where you need it, and print out the reassembled row.
If you expect more complicated data in your rows, you might wish to look at a csv module, such as Text::CSV.

Answer 3

I recommend to use an array of hashes for this:
.....
my ($type, $hostname, $location) = split /,/, $line;
push #records, {
type => $type,
hostname => $hostname,
location => $location,
};
.....
my #records_sorted = sort { $a->{type} cmp $b->{type} || $a->{location} cmp $b->{location} || $a->{hostname} cmp $b->{hostname} } #records;
...