Referencing a Backreference

dru145 has asked for the wisdom of the Perl Monks concerning the following question:

Monks,

I the follwing text:

192.168.89.1   acmeorp.acme.com
192.168.31.3   ftp.acme.com
192.168.19.179   [Unknown]
[download]

I'm caputuring the ip and servername into separate arrays. Here is my regex that does this:

push (@ips, $1) if /\b(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\b/;
push (@names, $1) if /\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b\s{2,}(\w[
+^\s]*|\[Unknown\])\s{2}/;
[download]

My question is, is there a way to reference the ip match in my regex that matches the server name? I thought this would work, but it doesn't:

#push (@names, $1) if /$1\s{2,}(\w[^\s]*|\[Unknown\])\s{2}/;
[download]

Thanks,
Dru
Another satisfied monk.

Comment on Referencing a Backreference Select or Download Code

Replies are listed 'Best First'.
Re: Referencing a Backreference by gav^ (Curate) on Mar 14, 2002 at 16:26 UTC
Wouldn't something like this be a lot simpler? `my @ips = (); my @names = (); while (<DATA>) { chomp; my ($ip, $name) = split /\s+/, $_, 2; push @ips, $ip; push @names, $name; } use Data::Dumper; print Dumper(\@ips, \@names); __DATA__ 192.168.89.1 acmeorp.acme.com 192.168.31.3 ftp.acme.com 192.168.19.179 [Unknown]` [download] gav^	[reply] [d/l]
Re: Re: Referencing a Backreference by Juerd (Abbot) on Mar 14, 2002 at 16:49 UTC
Wouldn't something like this be a lot simpler? So true, but it can be done even simpler! `my (@ips, @names); while (<DATA>) { my ($ip, $name) = split; push @ips, $ip; push @names, $name; }` [download] split with no arguments is like `split ' ', $_`, which in turn has a special meaning because of the chr(32) string. I think you can asume ip adresses and hostnames do not contain whitespace... If order and duplicates are not very important, a hash would be really nice: `my %hash = map split, <DATA>; my @ips = keys %hash; my @names = values %hash;` [download] U28geW91IGNhbiBhbGwgcm90MTMgY W5kIHBhY2soKS4gQnV0IGRvIHlvdS ByZWNvZ25pc2UgQmFzZTY0IHdoZW4 geW91IHNlZSBpdD8gIC0tIEp1ZXJk	[reply] [d/l] [select]
Two splits for the price of one! by belg4mit (Prior) on Mar 14, 2002 at 20:26 UTC
Not such a big deal here unless it's a huge log being parsed, but probably generally not the best generic scheme. `-- perl -pe "s/\b;([st])/'\1/mg"`	[reply]
Re: Referencing a Backreference by PrimeLord (Pilgrim) on Mar 14, 2002 at 16:54 UTC
This solution is along the same lines as gav's but with slightly less typing. `while (<DATA>) { chomp; push @ips, (split)[0]; push @names, (split)[1]; }` [download] Also I am a little confused on your question. If you are looking for a way to seperate the data, but still access server name by IP address you could always just write the info into a hash. `my %ips_names; while (<DATA>) { $ips_names{(split)[0]} = (split)[1]; }` [download] Then you can access just the portion of the data you need, but they are still tied together. Sorry if that wasn't actually what you were looking for. -Prime Update: Sigh. Juerd beat me to it again. :) Although my code is still shorter ;)	[reply] [d/l] [select]
Re: Referencing a Backreference by dru145 (Friar) on Mar 14, 2002 at 17:07 UTC
Well, there is actually more that I'm matching on. This is just a portion of it. Here is a little more background if you are interested Splitting Across Multiple Lines. I tried for two days trying to split on this text, but could not come up with a good solution. Regex work better for me in this case. I appreciate the suggestions, but I'm still wondering if there is a way to reference the regex like I'm trying to do. Thanks, Dru Another satisfied monk.	[reply]
Re: Re: Referencing a Backreference by thunders (Priest) on Mar 14, 2002 at 18:59 UTC
put the ip in a variable. Update:The error was actually in the original regex given not properly matching the names, as far as I can tell, but i think it's much more readable to use a variable name instead of $1, which I think looks confusing and non-intuitive inside of a pattern match. `#!/usr/bin/perl -w use strict; my @addrs = ( "192.168.89.1 acmeorp.acme.com", "192.168.31.3 ftp.acme.com", "192.168.19.179 [Unknown]" ); my (@ips,@names); for (@addrs) { push (@ips, $1) if /\b(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\b/; my $ip = $1; push (@names, $1) if /\Q$ip\E\s+([\w.]+[^\s]$\|\[Unknown\])\s?/; } print @names;` [download]	[reply] [d/l]


Keep It Simple, Stupid
	PerlMonks