Need help with Regex

[ewhitt]

I need some help with RegEx. The first two columns display unique IP addresses. I need to grab the number after "1000" and disregard the following numbers. How can I ignore all the unwanted information?

*> 4.23.88.0/23     64.135.0.1                             0 1000 234 
+46164 i
*> 4.23.89.0/24     64.135.0.1                             0 1000 2014
+8 46164 i
*> 4.23.92.0/23     64.135.0.1                             0 1000 2013
+8 46164 i
*> 4.23.92.0/22     64.135.0.1                             0 1000 3018
+ 46164 i
*> 4.23.94.0/23     64.135.0.1                             0 1000 4041
+8 46164 i
*> 4.23.112.0/24    64.135.0.1                             0 1000 1018
+ 174 21889 i
*> 4.23.113.0/24    64.135.0.1                             0 1000 2018
+ 174 21889 i
*> 4.23.114.0/24    64.135.0.1                             0 1000 18 1
+74 21889 i
*> 4.36.118.0/24    64.135.0.1                             0 1000 7018
+ 174 21889 i

[toolic]

I'm not entirely sure what you want for output because you did not show an example. But, if you just want to grab the 6th column from your input, you could use split instead of a regex:

use strict;
use warnings;

while (<DATA>) {
    my $num = (split)[5];
    print "$num\n";
}

__DATA__
*> 4.23.88.0/23     64.135.0.1                             0 1000 234 
+46164 i
*> 4.23.89.0/24     64.135.0.1                             0 1000 2014
+8 46164 i
*> 4.23.92.0/23     64.135.0.1                             0 1000 2013
+8 46164 i
*> 4.23.92.0/22     64.135.0.1                             0 1000 3018
+ 46164 i
*> 4.23.94.0/23     64.135.0.1                             0 1000 4041
+8 46164 i
*> 4.23.112.0/24    64.135.0.1                             0 1000 1018
+ 174 21889 i
*> 4.23.113.0/24    64.135.0.1                             0 1000 2018
+ 174 21889 i
*> 4.23.114.0/24    64.135.0.1                             0 1000 18 1
+74 21889 i
*> 4.36.118.0/24    64.135.0.1                             0 1000 7018
+ 174 21889 i

prints:

234
20148
20138
3018
40418
1018
2018
18
7018

[ewhitt]

Interesting. I have never seen "split" used like that before. How could I pass it a variable? Say I wanted to print "four" ?

$output = "one two three four five";
$output = (split $line)[4];

Thanks!

[toolic]

The parentheses around split forces it to return an array. The square brackets are used to select a single element from the array returned by split. We could either use a constant numeric value, such as 3, or we could use a scalar variable, such as $col to select the array item. Keep in mind that Perl arrays start at 0, not 1. So, "one" becomes array element [0], and "four" is element [3]:

use strict;
use warnings;

my $col = 3;
my $str = "one two three four five";
my $output = (split /\s+/, $str)[$col];
print "output=$output\n";

__END__
output=four

[swampyankee]

&ellip;and if toolic's suggestion won't always work, i.e., the number of columns changes, you could try something like this:

#/usr/bin/perl

use strict;
use warnings;

while(<DATA>){
    (my $junk, my $keep) = split(/\s1000\s/, $line, 2);
    my @datum = split(/\s+/,$keep);
    print shift(@datum),"\n";
}
__DATA__
*> 4.23.88.0/23     64.135.0.1                             0 1000 234 
+46164 i
*> 4.23.89.0/24     64.135.0.1                             0 1000 2014
+8 46164 i
*> 4.23.92.0/23     64.135.0.1                             0 1000 2013
+8 46164 i
*> 4.23.92.0/22     64.135.0.1                             0 1000 3018
+ 46164 i
*> 4.23.94.0/23     64.135.0.1                             0 1000 4041
+8 46164 i
*> 4.23.112.0/24    64.135.0.1                             0 1000 1018
+ 174 21889 i
*> 4.23.113.0/24    64.135.0.1                             0 1000 2018
+ 174 21889 i
*> 4.23.114.0/24    64.135.0.1                             0 1000 18 1
+74 21889 i
*> 4.36.118.0/24    64.135.0.1                             0 1000 7018
+ 174 21889 i

I know that the second split and the print can be wrapped into one statement. I'm at work, so I don't want to spend too much time on this.

[JavaFan]

print $1 if /1000\s+([0-9]+)/;

Be careful, it might grab an unintended number if there's another 1000 preceeding the 1000 you intend. But the regexp above grabs the "number after '1000'".

[Grey Fox]

Like I've said in previous posts there's lots of good regex info if you search around Perl Monks try Perlmonks Tutorial:
Regular Expressions Tutorial, the Basics (for BEGINNERS)
It helps if you try to code something up yourself then post. I've found learning by doing is the best way to get familiar with REGEX.
I have also found http://www.regular-expressions.info/quickstart.html very helpful working with regex's. Lots of good examples.
I found tools like http://www.txt2re.com/ or Eclipses regex tool to be helpful in debugging my regex commands.
Good Luck.