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Assignment problem with regex

kiojichi
New User

Sep 4, 2012, 4:22 PM

Post #1 of 3 (1618 views)

Assignment problem with regex	Can't Post

Hi All,

I'm having an issue getting a value assigned to a variable after a regex match, for an iP address. I'm sure I'm doing something that's clearly wrong, and obvious to most, but I'm new to Perl and I've been working on this for 2 days now. The assignment is just not happening right.

Code:

Code

sub block_match { 
	my $line_instance_b = $_[0]; 
	my $ipaddress; 
	if ( $line_instance_b =~ /banned_ip|Found UltraSurf Signature|ip_block / ) { 
		$ipaddress = $1 if $line_instance_b =~ /\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\b/; 
 
	print "Found ip address: ", $ipaddress, "in the following line: \n", 
		  $line_instance_b; 
	} 
	else { print "Not a block line: \n", $line_instance_b, "\n" } 
}

The line that the regex is matching against is:

Code

1307931062: INIT: banned_ip add 208.67.219.132 for FreeGate

In the match and substitution line, it appears that the regex is matching just fine, but when I try to send the matched data to a variable ($ipaddress in this case) it always fails. Is there a better way to do this?

Thanks.

kiojichi
New User

Sep 4, 2012, 5:06 PM

Post #2 of 3 (1613 views)

Re: [kiojichi] Assignment problem with regex [In reply to]	Can't Post

This question was answered for me by Jon Purdy at another site. Just pasting the answer here if its useful for someone in the future:

You’re using a non-capturing group, (?:...), which is never assigned to a match variable.

Wrap the (?:[0-9]{1,3}\.){3} part of the expression in () to capture into $1:

$ipaddress = $1 if $line_instance_b =~ /\b((?:[0-9]{1,3}\.){3})[0-9]{1,3}\b/;
#

BillKSmith
Veteran

Sep 4, 2012, 8:26 PM

Post #3 of 3 (1606 views)

Re: [kiojichi] Assignment problem with regex [In reply to]	Can't Post

Even better to use a module. Less chance of false matches.

Code

use Regexp::Common; 
sub block_match { 
    my $RE = $RE{net}{IPv4}{dec}; 
    my ($line_instance_b) = @_; 
    my $ipaddress; 
    if ( $line_instance_b =~ /banned_ip|Found UltraSurf Signature|ip_block / ) 
    { 
        ($ipaddress) = $line_instance_b =~ /$RE/;  
        print "Found ip address: ", $ipaddress, "in the following line: \n", 
            $line_instance_b; 
    } 
    else { print "Not a block line: \n", $line_instance_b, "\n" } 
}

Good Luck,
Bill

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