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Re: Using variable to hold regex expression

by Kenosis (Priest)
on Mar 11, 2013 at 23:36 UTC ( #1022900=note: print w/ replies, xml ) Need Help??


in reply to Using variable to hold regex expression

Have you considered using Regexp::Common::net to capture those IPs?

use strict; use warnings; use Regexp::Common qw/net/; while (<DATA>) { if ( my ( $firstIP, $secondIP ) = /($RE{net}{IPv4})/g ) { print "FirstIP: $firstIP\nSecondIP: $secondIP\n\n"; } } __DATA__ Sample data Mar 10 07:42:38 DR-FW-1 : %ASA-6-305011: Built dynamic UDP + translation from inside:172.28.17.130/3324 to outside(internet-traff +ic):69.176.102.83/24295 Sample data Mar 10 07:42:38 DR-FW-1 : %ASA-6-305011: Built dynamic UDP + translation from inside:155.0.42.42/3324 to outside(internet-traffic +):71.200.20.7/24295

Output:

FirstIP: 172.28.17.130 SecondIP: 69.176.102.83 FirstIP: 155.0.42.42 SecondIP: 71.200.20.7


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Re^2: Using variable to hold regex expression
by salatconed (Initiate) on Mar 12, 2013 at 00:05 UTC
    Perhaps using IP addresses was not a good example, I'm trying to figure out how to parse a string which has repetitive data, so I can write the regex expression once and get multiple returns if they exist the same way your code got both IP addresses in one call.
      ... how to parse a string which has repetitive data ...

      As choroba pointed out, every  (pattern) pair of parentheses in a regex captures something (even undef possibly) to its corresponding capture variable. One way to parse a string using nested regexes is avoid using a gazillion capturing groups. Use the non-capturing  (?:pattern) instead for grouping. See perlre, perlrequick, perlretut. In the IP example (but this should generalize to any repetitive data you wish to extract):

      >perl -wMstrict -le "my $decimal_octet = qr{ 2 (?: [0-4] \d | 5 [0-5]) | [01]? \d? \d }xms; my $ip = qr{ (?<! \d) $decimal_octet (?: \. $decimal_octet){3} (?! \d) }xms; print $ip; ;; my $s = '123.45.6.234 xx yyy zz 000.12.34.255'; my @ips = $s =~ m{ $ip }xmsg; printf qq{'$_' } for @ips; " (?^msx: (?<! \d) (?^msx: 2 (?: [0-4] \d | 5 [0-5]) | [01]? \d? \d ) (? +: \. (?^msx: 2 (?: [0-4] \d | 5 [0-5]) | [01]? \d? \d )){3} (?! \d) ) '123.45.6.234' '000.12.34.255'

      Note that neither  (?:pattern) nor the  (?<!pattern) (?!pattern) look-around assertions capture. Indeed, nothing captures (to a capture variable) since data is extracted in list context directly to an array.

      If I'm understaing you correctly, the my ( $firstIP, $secondIP ) = /($RE{net}{IPv4})/g in the above code does what you've described.

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